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Exercise training and protein metabolism: Influences of contraction, protein intake, and sex-based differences
Abstract
Muscle contraction during exercise, whether resistive or endurance in nature, has profound affects on muscle protein turnover that can persist for up to 72 h. It is well established that feeding during the postexercise period is required to bring about a positive net protein balance (muscle protein synthesis - muscle protein breakdown). There is mounting evidence that the timing of ingestion and the protein source during recovery independently regulate the protein synthetic response and influence the extent of muscle hypertrophy. Minor differences in muscle protein turnover appear to exist in young men and women; however, with aging there may be more substantial sex-based differences in response to both feeding and resistance exercise. The recognition of anabolic signaling pathways and molecules are also enhancing our understanding of the regulation of protein turnover following exercise perturbations. In this review we summarize the current understanding of muscle protein turnover in response to exercise and feeding and highlight potential sex-based dimorphisms. Furthermore, we examine the underlying anabolic signaling pathways and molecules that regulate these processes.
... Exercise, primary resistance-based, enhances MPS. However, the consumption of protein post-exercise is necessary to maximize the rates of MPS and overall stimulation of skeletal muscle hypertrophy [223]. ...
... No studies are currently available that specifically address the protein requirements of female athletes across the menstrual cycle or with the use of hormonal contraceptives. In eumenorrheic women, evidence suggests protein catabolism is higher at rest and following aerobic endurance exercise in the luteal phase, when estrogen and progesterone are elevated, compared to the early follicular phase when estrogen and progesterone concentrations are low [81,164,223,224]. Moreover, it has been shown that protein oxidation during exercise appears to be greater during the mid-luteal phase [164,223] and that females require more lysine during the luteal phase than the follicular phase [81] with a lower ability to uptake and utilize amino acids for protein synthesis. ...
... In eumenorrheic women, evidence suggests protein catabolism is higher at rest and following aerobic endurance exercise in the luteal phase, when estrogen and progesterone are elevated, compared to the early follicular phase when estrogen and progesterone concentrations are low [81,164,223,224]. Moreover, it has been shown that protein oxidation during exercise appears to be greater during the mid-luteal phase [164,223] and that females require more lysine during the luteal phase than the follicular phase [81] with a lower ability to uptake and utilize amino acids for protein synthesis. Although the blood amino acid profiles of COC users are shown to differ from non-users [225], the impact of COC on protein metabolism needs at rest or in response to exercise is yet to be elucidated. ...
Based on a comprehensive review and critical analysis of the literature regarding the nutritional concerns of female athletes, conducted by experts in the field and selected members of the International Society of Sports Nutrition (ISSN), the following conclusions represent the official Position of the Society: 1. Female athletes have unique and unpredictable hormone profiles, which influence their physiology and nutritional needs across their lifespan. To understand how perturbations in these hormones affect the individual, we recommend that female athletes of reproductive age should track their hormonal status (natural, hormone driven) against training and recovery to determine their individual patterns and needs and peri and post-menopausal athletes should track against training and recovery metrics to determine the individuals' unique patterns. 2. The primary nutritional consideration for all athletes, and in particular, female athletes, should be achieving adequate energy intake to meet their energy requirements and to achieve an optimal energy availability (EA); with a focus on the timing of meals in relation to exercise to improve training adaptations, performance, and athlete health. 3. Significant sex differences and sex hormone influences on carbohydrate and lipid metabolism are apparent, therefore we recommend first ensuring athletes meet their carbohydrate needs across all phases of the menstrual cycle. Secondly, tailoring carbohydrate intake to hormonal status with an emphasis on greater carbohydrate intake and availability during the active pill weeks of oral contraceptive users and during the luteal phase of the menstrual cycle where there is a greater effect of sex hormone suppression on gluconogenesis output during exercise. 4. Based upon the limited research available, we recommend that pre-menopausal, eumenorrheic, and oral contraceptives using female athletes should aim to consume a source of high-quality protein as close to beginning and/or after completion of exercise as possible to reduce exercise-induced amino acid oxidative losses and initiate muscle protein remodeling and repair at a dose of 0.32-0.38 g·kg-1. For eumenorrheic women, ingestion during the luteal phase should aim for the upper end of the range due to the catabolic actions of progesterone and greater need for amino acids. 5. Close to the beginning and/or after completion of exercise, peri- and post-menopausal athletes should aim for a bolus of high EAA-containing (~10 g) intact protein sources or supplements to overcome anabolic resistance. 6. Daily protein intake should fall within the mid- to upper ranges of current sport nutrition guidelines (1.4-2.2 g·kg-1·day-1) for women at all stages of menstrual function (pre-, peri-, post-menopausal, and contraceptive users) with protein doses evenly distributed, every 3-4 h, across the day. Eumenorrheic athletes in the luteal phase and peri/post-menopausal athletes, regardless of sport, should aim for the upper end of the range. 7. Female sex hormones affect fluid dynamics and electrolyte handling. A greater predisposition to hyponatremia occurs in times of elevated progesterone, and in menopausal women, who are slower to excrete water. Additionally, females have less absolute and relative fluid available to lose via sweating than males, making the physiological consequences of fluid loss more severe, particularly in the luteal phase. 8. Evidence for sex-specific supplementation is lacking due to the paucity of female-specific research and any differential effects in females. Caffeine, iron, and creatine have the most evidence for use in females. Both iron and creatine are highly efficacious for female athletes. Creatine supplementation of 3 to 5 g per day is recommended for the mechanistic support of creatine supplementation with regard to muscle protein kinetics, growth factors, satellite cells, myogenic transcription factors, glycogen and calcium regulation, oxidative stress, and inflammation. Post-menopausal females benefit from bone health, mental health, and skeletal muscle size and function when consuming higher doses of creatine (0.3 g·kg-1·d-1). 9. To foster and promote high-quality research investigations involving female athletes, researchers are first encouraged to stop excluding females unless the primary endpoints are directly influenced by sex-specific mechanisms. In all investigative scenarios, researchers across the globe are encouraged to inquire and report upon more detailed information surrounding the athlete's hormonal status, including menstrual status (days since menses, length of period, duration of cycle, etc.) and/or hormonal contraceptive details and/or menopausal status.
... Hem endürans hem de direnç egzersizleri sonrasında protein alımının kas protein sentezini indüklediği bilinmektedir. 31,32 Yüksek şiddetli egzersiz kas protein sentezini ve yıkımını artırırken net protein dengesini oluşturur. 31 Artan protein döngüsü iskelet kasının remodelasyonunu ve plastisitesini destekleyen bir fonksiyon görür. ...
... 31,32 Yüksek şiddetli egzersiz kas protein sentezini ve yıkımını artırırken net protein dengesini oluşturur. 31 Artan protein döngüsü iskelet kasının remodelasyonunu ve plastisitesini destekleyen bir fonksiyon görür. 33 Direnç egzersizleriyle kasların diyetteki proteine 24 saat kadar duyarlı kaldığı gösterilmiş ve bu süre gelişmiş kas remodelasyonu ve adaptasyonu için "fırsat penceresi" olarak nitelendirilmiştir. ...
... 42,43 Kuvvet çalışmaları söz konusu olduğunda egzersizin indüklediği kassal büyümeyi de geliştirirler. 31 Bu nedenle diyetteki protein, kaslarda protein remodelasyonunu geliştirdiği için sporcularda toparlanma döneminde temel beslenme komponentlerinden birisi olmaktadır. Egzersiz sonrası yüksek kaliteli protein desteği (0,25 gr/kg) sağlanmalıdır. ...
30 porcular temel performans parametrelerini geliştirmeye yönelik egzersizlere antrenman programlarında yer verirler. Optimal performans düzeyi için en önemli belirleyici antrenman olmakla birlikte beslenme de çok önemli ve etkili bir komponentdir. Doğru bir beslenme planı sporcuların optimal performansın gerek-tirdiği enerji düzeyine sahip olmalarını, ideal kilolarında kalmalarını ve antrenmanın programının bütün aşamalarında kendilerini iyi hissetmelerini sağlayacaktır. İdeal bir beslenme planı oluşturmak deneyimli sporcular için bile kolay bir durum değildir. 1 Sporcu Beslenmesi ve Antrenman İlişkisi Nasıl Sağlanmalı? Ö ÖZ ZE ET T Sporda başarıyı sağlayan pek çok faktör olmakla birlikte beslenme anahtar bir rol üstlen-mektedir. Araştırma sonuçları planlı ve bilimsel bir beslenme stratejisinin sportif performansı ge-liştirdiği yönünde sonuçlar vermektedir. Sporcuya özel ve antrenman periyodizasyonuna uygun bireysel beslenme stratejisinin spor türü, performans beklentisi, hedefleri, sporcunun beslenme alış-kanlıkları ve tercihlerinin dikkate alınarak oluşturulması gerekmektedir. Sporcularda egzersiz ön-cesi optimal beslenmenin sağlanması ve egzersiz sonrası toparlanmanın desteklenmesi için yeterli düzeyde günlük enerji alımı şarttır. Total enerji ihtiyacının sağlanması kaydıyla sporcunun tercih-lerine ve toleransına göre düzenleme yapılabilir. Dengeli bir beslenme fiziksel aktivite nedeniyle artan enerji ihtiyacını karşılayabilmelidir. İyi bir beslenme, yoğun antrenman programını destek-lediği gibi kassal toparlanma ve endürans egzersizlerine olan metabolik adaptasyonu kolaylaştırır. Bu derlemede, sporcu beslenmesi ve antrenman ilişkisinin öneminden bahsedilecek ve beslenme yaklaşımları ile fizyolojik yanıtlar hakkında pratik önerilere yer verilecektir. A An na ah ht ta ar r K Ke el li im me el le er r: : Sporcular; egzersiz; beslenme durumu; spor performansı A AB BS ST TR RA AC CT T A number of factors contribute to success in sport, and diet is a key component. Research findings show that a planned scientific nutritional strategy is related to better sports performance. Individualized and periodized nutritional strategy according to training program should depend on several aspects, including the sport, the athlete's goals, the environment, and practical issues. Daily energy intake is essential in athletes, and should be timed according to training sessions in order to ensure optimal pre-workout nutrition, as well as to encourage recovery post workout. If this is not possible during the day, the intake should be tailored according to individual preference and tolerance, provided that the total daily requirements are met. Maintenance of the energy balance in individuals with increased requirements because of physical activity is important. Good nutrition assists in the ability to train intensely, as well as in muscle recovery and metabolic adaptations to endurance exercise. This review will focus on the importance of the interaction between sports nutrition and training status, and discuss practical recommendations about nutritional approaches and physiological responses. K Ke ey y W Wo or rd ds s: : Athletes; exercise; nutritional status; sports performance T Tu ur rk ki iy ye e K Kl li in ni ik kl le er ri i J J S Sp po or rt ts s M Me ed d-S Sp pe ec ci ia al l T To op pi ic cs s 2 20 01 16 6; ;2 2((3 3)):
... The first aim of the study was to identify the distribution of protein in meals throughout the day, we consider this amount is similar according to studies that consumption of 20-40 g of protein before bed has positive effects on muscle protein synthesis (MPS) [22][23][24] . However, our study found positive associa-found positive associations between pre-sleep protein intake and muscle strength, indicating a potential protective effect of pre-sleep protein on cancer-induced muscle strength loss. ...
... In our study, there was an association between pre-sleep protein intake and increased muscle strength, some studies have suggested that pre-sleep protein has been shown to be effective in increasing muscle protein synthesis, inducing a positive net protein balance muscle overnight, being effectively digested and absorbed and thus increasing the availability of plasma amino acids leading to skeletal muscle hypertrophy [22][23][24][25][26][27] . ...
... can reduce anabolic properties, which could potentially increase the risk of muscle injury when under repeated training stress (31). It is however important to interpret these results with caution as we did not collect data to indicate an increase in progesterone in the estimated luteal phase. ...
... Secondly, and more specifically in the pre-menstrual window, the withdrawal of hormones pre-menstrually, where there is a transition from high to low oestrogen and progesterone, results in the up-regulation of proinflammatory pathways and an increased expression of inflammatory mediators such as prostaglandins which are essential for the breakdown of the endometrial lining (32). The effects appear to be systemic, with a number of studies demonstrating elevated levels of inflammatory biomarkers peri-menstrually (31)(32)(33). This could delay or extend recovery times, which could affect recovery and induce a state of overload by compromising tissue integrity and increase the risk of injury. ...
Purpose
The aim of the study was to assess the influence of menstrual cycle phase on injury incidence, severity and type in elite female professional footballers over three seasons.
Methods
Time-loss injuries and menstrual cycle data were prospectively recorded for 26 elite female football players across three seasons. The menstrual cycle was categorised into four phases using a standardised model: menstruation (phase 1; P1), remainder of follicular phase (phase 2; P2), early luteal (phase 3; P3), and pre-menstrual phase (phase 4; P4). Injury incidence rates (IRR) and ratios (IIRR) were calculated for overall injuries, injury severity, type, contact vs non-contact and game/training.
Results
593 cycles across 13,390 days were tracked during the study and 74 injuries from 26 players were eligible for analysis. When comparing IRR between phases (reference: P1), overall injury rates were highest in P4 (IIRR: 2.30 [95% CI: 0.99-5.34; p = 0.05]). When examining rates by injury severity and type, IRR were also highest in P4 for ≤7 days’ time-loss (4.40 [0.93-20.76; p = 0.06]), muscle-specific (6.07 [1.34-27.43; p = 0.02]) and non-contact (3.05 [1.10-8.50; p = 0.03]) injuries. Muscle-specific (IIRR P3:P1: 5.07 [1.16-22.07; p = 0.03]) and ≤ 7 days’ time-loss (4.47 [1.01-19.68; p = 0.05]) injury risk was also significantly higher in P3. Muscle injuries were the most prevalent sub-type (n = 41). No anterior cruciate ligament injuries were recorded across the monitoring period.
Conclusions
Injury risk was significantly elevated during the luteal phase of the menstrual cycle (P3 and P4) among elite female professional footballers. Further research is urgently needed to better understand the influence of the menstrual cycle on injury risk and to develop interventions to mitigate risk.
... SKM mass is regulated by the dynamic relationship between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). In the postabsorptive state, net MPB exceeds MPS whilst net MPS exceeds MPB in the postprandial state; therefore achieving net protein balance across diurnal fasted-fed cycles [5,6]. Following a protein feed, MPS increases~2e3 fold, peaking between~1.5 and 2 h post-feed whilst MPB is transiently inhibited by~50% in young healthy muscle, though this effect (i.e., increases in MPS/inhibition of MPB) is significantly blunted in older muscle [7e9]. ...
... Following a protein feed, MPS increases~2e3 fold, peaking between~1.5 and 2 h post-feed whilst MPB is transiently inhibited by~50% in young healthy muscle, though this effect (i.e., increases in MPS/inhibition of MPB) is significantly blunted in older muscle [7e9]. Indeed, both MPS and MPB are responsive to dietary protein feeding, both alone and when combined with various modalities of exercise (i.e., resistance, endurance, and concurrent exercise) [5,6], but also to periods of inactivity and disease [10e13]. ...
Muscle protein synthesis (MPS) and muscle protein breakdown (MPB) are influenced through dietary protein intake and physical (in)activity, which it follows, regulate skeletal muscle (SKM) mass across the lifespan. Following consumption of dietary protein, the bio-availability of essential amino acids (EAA), and primarily leucine (LEU), drive a transient increase in MPS with an ensuing refractory period before the next MPS stimulation is possible (due to the "muscle full" state). At the same time, MPB is periodically constrained via reflex insulin actions. Layering exercise on top of protein intake increases the sensitivity of SKM to EAA, therefore extending the muscle full set-point (∼48 h), to permit long-term remodelling (e.g., hypertrophy). In contrast, ageing and physical inactivity are associated with a premature muscle full set-point in response to dietary protein/EAA and contractile activity. Of all the EAA, LEU is the most potent stimulator of the mechanistic target of rapamycin complex 1 (mTORC1)-signalling pathway, with the phosphorylation of mTORC1 substrates increasing ∼3-fold more than with all other EAA. Furthermore, maximal MPS stimulation is also achieved following low doses of LEU-enriched protein/EAA, negating the need for larger protein doses. As a result, LEU supplementation has been of long term interest to maximise muscle anabolism and subsequent net protein accretion, especially when in tandem with resistance exercise. This review highlights current knowledge vis-à-vis the anabolic effects of LEU supplementation in isolation, and in enriched protein/EAA sources (i.e., EAA and/or protein sources with added LEU), in the context of ageing, exercise and unloading states.
... Additionally, it should be noted that it is not just the leucine content of the protein, or even the postprandial leucinemia, that solely determines postprandial myoFSR. Factors such as age, sex, health, nutritional and training status (and the interactions between them) differentially affect anabolism [25,26]. For example, ingestion of 40 g of soy protein was shown to be ineffective at increasing resting myoFSR in older men, whereas ingestion after RET led to robust increases in the myoFSR [9]. ...
... For example, ingestion of 40 g of soy protein was shown to be ineffective at increasing resting myoFSR in older men, whereas ingestion after RET led to robust increases in the myoFSR [9]. Similarly, sexually dimorphic postprandial MPS rates have been reported in older, but not younger, men and women [25][26][27][28]. Indeed, a novel aspect of the present study was the use of a mixed-sex cohort, whereas most research in this area is limited to single-sex studies (i.e., mostly men). ...
The aim of the present study was to evaluate the effect of feeding fava bean (Vicia faba L.) protein (FBP) on resting and post-exercise myofibrillar fractional synthetic rate (myoFSR). In a parallel, double-blind, randomised control trial, sixteen young, healthy recreationally active adults (age = 25 (5) years, body mass = 70 (15) kg, stature = 1.72 (0.11) m, mean (SD)) ingested 0.33 g·kg−1 FBP (n = 8) or a negative control (CON, i.e., EAA-free mixture) (n = 8), immediately after a bout of unilateral knee-extensor resistance exercise. Plasma, saliva, and m. vastus lateralis muscle samples were obtained pre-ingestion and 3 h post-ingestion. MyoFSR was calculated via deuterium labelling of myofibrillar-bound alanine, measured by gas chromatography–pyrolysis–isotope ratio mass spectrometry (GC-Pyr-IRMS). Resistance exercise increased myoFSR (p = 0.012). However, ingestion of FBP did not evoke an increase in resting (FBP 29 [−5, 63] vs. CON 12 [−25, 49]%, p = 0.409, mean % change [95% CI]) or post-exercise (FBP 78 [33, 123]% vs. CON 58 [9, 107]%, p = 0.732) myoFSR. Ingestion of 0.33 g·kg−1 of FBP does not appear to enhance resting or post-exercise myoFSR in young, healthy, recreationally active adults.
... The implications of this study for preventing age-related sarcopenia a degenerative decrease of muscle mass is obvious When compared to other protein sources, whey protein digests and absorbs quickly, raising the total amount of amino acids in the blood. Following resistance exercise, this hyperaminoacidemia condition drives a surge in the production of muscle proteins and a small inhibition of muscle protein breakdown [10]. Because WP contains a comparatively higher amount of the branched-chain amino acid leucine, this process of stimulating protein synthesis also happens through this route. ...
The best pharmacological treatments and dietary regimens for cancer continue to be a problem for public health. In the scientific field of oncology, whey protein WP is frequently used as a dietary strategy. The goal of the current meta-analysis is to ascertain the positive impact of WP supplements on cancer patients. A comprehensive literature search was conducted to identify RCTs that investigated WP in cancer patients. Cochrane Database of Clinical Trials, Scopus, PubMed, Google Scholar and WOS with no language restrictions for relevant studies.
Reports were fully assessed based on the inclusion criteria found only 23. Only four studies were included in the systematic review and meta‐analysis. Body weight and weight change showed the difference was significantly favoring the whey protein arm at 12 weeks (MD = 1.41 [0.14, 2.69]). BMI and change in BMI, lean tissue mass and increase in lean tissue mass showed nonsignificant differences throughout follow-up. Handgrip strength and change in handgrip strength showed significantly higher in the whey-treated arm after 3 and 6 months (MD = 3.11 [1.45, 4.78], 1.04 [− 0.55, 2.63], respectively. Whey protein significantly decreased the hematological toxicity of chemotherapy (RR = 0.55 [0.30, 0.98]) compared to the control group However, gastrointestinal toxicity was not reduced with whey protein treatment (RR = 0.58 [0.19, 1.79]).
In malnourished cancer patients undergoing Chemotherapy supplementation with WP may improve body weight, and handgrip strength and reduce Chemotherapy toxicity, which may lead to improved treatment efficacy.
... Although the protein intake of Spanish athletes did not differ particularly from the values found in other climbing athletes [21,44,58], several athletes showed intakes below the recommendations. Considering the large energy deficit status of these athletes and the high frequency of isometric contractions performed during climbing [13,65], it may be especially important to take care of protein intake in climbing athletes in view of maintaining maximal levels of fat-free mass and grip strength [66,67]. However, focusing on energy intake in relation to increases in nutritional carbohydrate intake seems to be the most sensible recommendation based on the findings of the present study. ...
Climbing is an Olympic discipline in full development and multidisciplinary in nature, where the influences of body composition and nutritional status on performance have not yet been clarified despite the quest for a low weight in anti-gravity disciplines such as climbing. The present cross-sectional study aimed to conduct nutritional (3-day dietary diaries) and body composition (ISAK profile) assessments on sport climbing athletes by gender and climbing level during the months of February and March 2024. The t-test for independent samples and the Mann–Whitney U-test, as well as an ANOVA and the Kruskal–Wallis H-test, were used to compare the distributions of two or more groups, respectively, and Pearson’s and Spearman’s correlation coefficients were used to estimate the correlations between the different variables. The mean age of the 46 Spanish climbers (22 men and 24 women) was 30 years (SD: 9) with 7.66 years of experience (SD: 6.63). The mean somatotype of the athletes was classified as balanced mesomorph. Negative correlations were observed between fat mass variables and climbing level (p < 0.010), and positive correlations were observed with forearm circumference (p < 0.050). The mean energy availability (EA) was 33.01 kcal-kg FFM⁻¹d⁻¹ (SD: 9.02), with 55.6% of athletes having a suboptimal EA status and 35.6% having low energy availability (LEA). The carbohydrate and protein intakes were below the recommendations in 57.8% and 31.1% of athletes, respectively. There were deficient intakes of all micronutrients except phosphorus in males. These findings suggest that climbing athletes are at a high risk of developing low energy availability states and concomitant problems. Optimal nutritional monitoring may be advisable in this type of athlete to try to reduce the risk of LEA.
... Differences in PFAA concentration between highly trained athletes representing different sports are not known, but are to be expected due to the specific demands of training and competition that lead to distinctive metabolic adaptations. Stimuli triggered by different exercise modes produce divergent responses, for example, resistance exercise promotes myofibrillar, while endurance mode mitochondrial protein synthesis in trained individuals [11,12]. However, direct comparisons of exercise-induced PFAA concentrations between groups of specialized high-level athletes are lacking. ...
Circulating blood is an important plasma free amino acids (PFAAs) reservoir and a pivotal link between metabolic pathways. No comparisons are available between athletes with opposite training adaptations that include a broader spectrum of both proteinogenic and non-proteinogenic amino acids, and that take into account skeletal muscle mass. We hypothesized that the levels of the exercise-induced PFAAs concentration are related to the type of training-related metabolic adaptation. We compared highly trained endurance athletes (n = 11) and sprinters (n = 10) aged 20‒35 years who performed incremental exercise until exhaustion. Venous blood was collected before and during the test and 30-min recovery (12 samples). Forty-two PFAAs were assayed using LC-ESI-MS/MS technique. Skeletal muscle mass was estimated using dual X-ray absorptiometry method. Glutamine and alanine were dominant PFAAs throughout the whole exercise and recovery period (~350‒650 μmol∙L⁻¹). Total, combined proteinogenic, non-essential, and non-proteinogenic PFAAs levels were significantly higher in endurance athletes than sprinters (ANOVA group effects: p = 0.007, η² = 0.321; p = 0.011, η² = 0.294; p = 0.003, η² = 0.376; p = 0.001, η² = 0.471, respectively). The exercise response was more pronounced in endurance athletes, especially for non-proteinogenic PFAAs (ANOVA interaction effect: p = 0.038, η² = 0.123). Significant between-group differences were observed for 19 of 33 PFAAs detected, including 4 essential, 7 non-essential, and 8 non-proteinogenic ones. We demonstrated that the PFAAs response to incremental aerobic exercise is associated with the type of training-related metabolic adaptation. A greater turnover and availability of circulating PFAAs for skeletal muscles and other body tissues is observed in endurance- than in sprint-trained individuals. Non-proteinogenic PFAAs, despite low concentrations, also respond to exercise loads, indicating their important, though less understood role in exercise metabolism. Our study provides additional insight into the exercise-induced physiological response of PFAAs, and may also provide a rationale in discussions regarding dietary amino acid requirements in high-performance athletes with respect to sports specialization.
... In relation to protein intake, the intakes reported by Spanish climbers do not differ greatly from the values reflected in other studies with climbers [21,44,58], although Simič et al. [56] and Chmielewska et al. [42] showed protein intakes in relation to BM lower than these findings. Nevertheless, considering the deficient energy intakes, the prevalence of athletes below protein recommendations and the high frequency of isometric contractions performed during climbing [13,65], it may be prudent to monitor the intake of this macronutrient in climbing athletes for the adequacy of body mass and grip strength [66,67]. ...
Climbing is an Olympic discipline in full development and multidisciplinary in nature, in which the influence of body composition and nutritional status on performance has not yet been clarified despite the quest for low weight in anti-gravity disciplines such as climbing. The present study aimed to do a nutritional (3-day dietary diaries) and body composition (ISAK profile) assessment of sport climbing athletes of different genders and sport levels. The mean age of the forty-six Spanish climbers (22 men and 24 women) was 30 years (SD: 9) with 7.66 years of experience (SD: 6.63). The mean somatotype of the athletes was classified as balanced mesomorph. Negative correlations were observed between fat mass variables and climbing level (p
... These are physiological processes that serve to break down old, non-functional, and damaged or oxidised proteins to replace them with newly optimised ones. The ratio between protein synthesis and protein breakdown is known as protein turnover (Burd et al., 2009). Protein balance, on the other hand, represents the difference between protein synthesis and protein degradation rates. ...
In strength and power sports, an optimal development of muscle strength, power, and speed, as well as optimal body composition, is key for performance and competitive success. Additionally, the ability to perform and sustain high-intensity exercise, either in a single bout or in multiple bouts separated by short resting intervals, is also determinant to success in a wide variety of strength and power sports. The optimal development of these capacities depends on multiple factors, with adequate training stimuli and nutritional support being two cornerstones to success. This article presents an overview of the physiology underpinning high-intensity, short-duration exercises, and discusses training methods for developing muscle strength and power, and for promoting muscle growth. Nutritional strategies, as well as supplements to aid training performance, recovery, and competition performance are discussed, with focus on high-intensity exercises, strength, and power sports.
... During resistance exercise, skeletal muscle can promote protein metabolism in response to exercise stimuli. In particular, muscle protein synthesis is increased for up to 24 h after resistance exercise, contributing to muscle hypertrophy [7]. During resistance exercise, the secretion of myokines and cytokines is promoted in the muscles [8,9]. ...
Background: Recently, many studies have been devoted to discovering nutrients for exercise-like effects. Resistance exercise and the intake of essential amino acids (EAAs) are known to be factors that can affect muscle mass and strength improvement. The purpose of this study was to investigate changes in muscle quality, myokines, and inflammation in response to resistance exercise and EAA supplementation. Methods: Thirty-four males volunteered to participate in this study. They were assigned to four groups: (1) placebo (CO), (2) resistance exercise (RE), (3) EAA supplementation, and (4) RE + EAA supplementation. Body composition, muscle quality, myokines, and inflammation were measured at baseline and four weeks after treatment. Results: Lean body fat had decreased in both RE and RE + EAA groups. Lean body mass had increased in only the RE + EAA group. In all groups except for CO, irisin, myostatin A, and TNF-α levels had decreased. The grip strength of the right hand and trunk flexion peak torque increased in the RE group. The grip strength of the left hand, trunk flexion peak torque, and knee flexion peak torque of the left leg were increased in RE + EAA. Conclusions: RE, EAA, and RE + EAA could effectively improve the muscle quality, myokine, and inflammation factors of young adult males. This finding highlights the importance of resistance exercise and amino acid intake.
... We calculated iAUC for both the early (0-2 h) and total (0-5 h) postprandial periods. We chose the 0-2 h period to designate the early timeframe as this represents the typical time frame of peak amino acid availability [27,28]. Moreover, this period is a physiologically relevant postexercise window from a performance nutrition perspective to support the skeletal muscle adaptive response [29]. ...
Microbial protease co-ingestion with pea protein increased postprandial plasma total amino acid concentrations across 5 hours compared to placebo in health adults, as well as increasing branched chain, essential, and total amino acid availability in the early postprandial period (0‒2 hours). Future studies are warranted to investigate the metabolic fate (e.g., muscle protein synthesis, oxidation) of plasma amino acids after microbial protease supplementation and the long-term clinical and performance nutrition relevance.
... While proteins are not considered a primary source of energy during physical activity, they are important for endurance sports or long workouts, where there is a risk of muscle and hepatic glycogen store and intramuscular fat depletion. In such scenarios, proteins can serve as an important source of energy, contributing to up to 5% of total energy expenditure [19,20]. Amino acids, in particular branched-chain amino acids (BCAAs), are also valuable during prolonged exercise, as they can supply up to 10-15% of energy required [21]. ...
Supplementation is crucial for improving performance and health in phenylketonuria (PKU) patients, who face dietary challenges. Proteins are vital for athletes, supporting muscle growth, minimizing catabolism, and aiding muscle repair and glycogen replenishment post-exercise. However, PKU individuals must limit phenylalanine (Phe) intake, requiring supplementation with Phe-free amino acids or glycomacropeptides. Tailored to meet nutritional needs, these substitutes lack Phe but fulfill protein requirements. Due to limited supplement availability, athletes with PKU may need higher protein intake. Various factors affect tolerated Phe levels, including supplement quantity and age. Adhering to supplement regimens optimizes performance and addresses PKU challenges. Strategically-timed protein substitutes can safely enhance muscle synthesis and sports performance. Individualized intake is essential for optimal outcomes, recognizing proteins’ multifaceted role. Here, we explore protein substitute supplementation in PKU patients within the context of physical activity, considering limited evidence.
... In order to achieve maximum muscle protein synthesis and net protein balance, it is crucial to consume a source of protein after resistance exercise [127]. These factors are necessary to sustain muscular hypertrophy throughout training. ...
Citation: Martín-Rodríguez, A.; Belinchón-deMiguel, P.; Rubio-Zarapuz, A.; Tornero-Aguilera, J.F.; Martínez-Guardado, I.; Villanueva-Tobaldo, C.V.; Clemente-Suárez, V.J. Advances in Understanding the Interplay between Dietary Practices, Body Composition, and Sports Performance in Athletes. Nutrients 2024, 16, 571. Abstract: The dietary practices of athletes play a crucial role in shaping their body composition, influencing sports performance, training adaptations, and overall health. However, despite the widely acknowledged significance of dietary intake in athletic success, there exists a gap in our understanding of the intricate relationships between nutrition, body composition, and performance. Furthermore, emerging evidence suggests that many athletes fail to adopt optimal nutritional practices, which can impede their potential achievements. In response, this Special Issue seeks to gather research papers that delve into athletes' dietary practices and their potential impacts on body composition and sports performance. Additionally, studies focusing on interventions aimed at optimizing dietary habits are encouraged. This paper outlines the key aspects and points that will be developed in the ensuing articles of this Special Issue.
... While proteins are not considered a primary source of energy during physical activity, they are important for endurance sports or long workouts, where there is a risk of muscle and hepatic glycogen store and intramuscular fat depletion. In such scenarios, proteins can serve as an important source of energy, contributing to up to 5% of total energy expenditure [19,20]. Amino acids, in particular branched-chain amino acids (BCAAs), are also valuable during prolonged exercise, as they can supply up to 10-15% of energy required [21]. ...
Proteins play a pivotal role in supporting athletes by promoting muscle hypertrophy and minimizing protein catabolism during exercise. They stimulate muscle protein synthesis, aiding in the repair of exercise-induced muscle damage and serving as an energy source, particularly for post-exercise glycogen replenishment. In individuals with phenylketonuria (PKU), for whom protein intake is limited to essential phenylalanine (Phe), supplementation with Phe-free amino acids or glycomacropeptides is necessary. Tailored for macronutrient and micronutrient content, these protein substitutes fulfill most protein requirements, but lack Phe, unlike dietary sources of protein. Protein requirements for athletes with PKU exceed general recommendations due to limited availability in supplements and potential catabolism mitigation. Various factors influence tolerated dietary Phe in PKU, including protein substitute quantity, distribution, pharmacological treatment, age, growth rate, pregnancy, catabolic states, and physical activity. While general protein requirements for PKU surpass those of the general population, adherence to supplement regimens is crucial for athletes and patients with PKU. Strategically timed protein substitutes enhance muscle protein synthesis, body composition, and sports performance within safety limits. Individualized intake is essential for optimal outcomes, as proteins have a multifaceted role in optimizing athletic performance and addressing challenges in PKU.
... Moreover, the importance of skeletal muscle mass extends beyond active individuals, providing direct clinical applications and benefits. This dynamic interplay-the balance between muscle protein synthesis and breakdown-is particularly crucial for aging adults, as skeletal muscle undergoes continuous regulation (54). The loss of muscle mass occurs when there is a negative balance, indicating a higher breakdown than synthesis, resulting in a net loss. ...
Nutrition serves as the cornerstone of an athlete's life, exerting a profound impact on their performance and overall well-being. To unlock their full potential, athletes must adhere to a well-balanced diet tailored to their specific nutritional needs. This approach not only enables them to achieve optimal performance levels but also facilitates efficient recovery and reduces the risk of injuries. In addition to maintaining a balanced diet, many athletes also embrace the use of nutritional supplements to complement their dietary intake and support their training goals. These supplements cover a wide range of options, addressing nutrient deficiencies, enhancing recovery, promoting muscle synthesis, boosting energy levels, and optimizing performance in their respective sports or activities. The primary objective of this narrative review is to comprehensively explore the diverse nutritional requirements that athletes face to optimize their performance, recovery, and overall well-being. Through a thorough literature search across databases such as PubMed, Google Scholar, and Scopus, we aim to provide evidence-based recommendations and shed light on the optimal daily intakes of carbohydrates, protein, fats, micronutrients, hydration strategies, ergogenic aids, nutritional supplements, and nutrient timing. Furthermore, our aim is to dispel common misconceptions regarding sports nutrition, providing athletes with accurate information and empowering them in their nutritional choices.
... Moreover, the importance of skeletal muscle mass extends beyond active individuals, providing direct clinical applications and benefits. This dynamic interplay-the balance between muscle protein synthesis and breakdown-is particularly crucial for aging adults, as skeletal muscle undergoes continuous regulation (54). The loss of muscle mass occurs when there is a negative balance, indicating a higher breakdown than synthesis, resulting in a net loss. ...
Nutrition serves as the cornerstone of an athlete’s life, exerting a profound impact on their performance and overall well-being. To unlock their full potential, athletes must adhere to a well-balanced diet tailored to their specific nutritional needs. This approach not only enables them to achieve optimal performance levels but also facilitates efficient recovery and reduces the risk of injuries. In addition to maintaining a balanced diet, many athletes also embrace the use of nutritional supplements to complement their dietary intake and support their training goals. These supplements cover a wide range of options, addressing nutrient deficiencies, enhancing recovery, promoting muscle synthesis, boosting energy levels, and optimizing performance in their respective sports or activities. The primary objective of this narrative review is to comprehensively explore the diverse nutritional requirements that athletes face to optimize their performance, recovery, and overall well-being. Through a thorough literature search across databases such as PubMed, Google Scholar, and Scopus, we aim to provide evidence-based recommendations and shed light on the optimal daily intakes of carbohydrates, protein, fats, micronutrients, hydration strategies, ergogenic aids, nutritional supplements, and nutrient timing. Furthermore, our aim is to dispel common misconceptions regarding sports nutrition, providing athletes with accurate information and empowering them in their nutritional choices.
... L-leucine has been shown to independently upregulate MPS by activating the mammalian target of rapamycin complex-1 (42). Generally, it is recognized that 8-10 g (1.8-2.0 g leucine) of essential amino acids maximizes MPS with whey protein specifically leading to a rapid rise in blood amino acid concentrations and therefore MPS (43,44). Nonetheless, it is generally recognized that the total daily intake of protein and wholebody protein balance (i.e., nitrogen balance) are key determinants compared to the timing of protein intake in the context of muscle recovery (45). ...
British Army basic training (BT) is physically demanding with new recruits completing multiple bouts of physical activity each day with limited recovery. Load carriage is one of the most physically demanding BT activities and has been shown to induce acute exercise-induced muscle damage (EIMD) and impair muscle function. Protein supplementation can accelerate muscle recovery by attenuating EIMD and muscle function loss. This study investigated the impact of an additional daily bolus of protein prior to sleep throughout training on acute muscle recovery following a load carriage test in British Army recruits. Ninety nine men and 23 women (mean ± SD: age: 21.3 ± 3.5 yrs., height: 174.8 ± 8.4 cm, body mass 75.4 ± 12.2 kg) were randomized to dietary control (CON), carbohydrate placebo (PLA), moderate (20 g; MOD) or high (60 g; HIGH) protein supplementation. Muscle function (maximal jump height), perceived muscle soreness and urinary markers of muscle damage were assessed before (PRE), immediately post (POST), 24-h post (24 h-POST) and 40-h post (40 h-POST) a load carriage test. There was no impact of supplementation on muscle function at POST (p = 0.752) or 40 h-POST (p = 0.989) load carriage but jump height was greater in PLA compared to HIGH at 24 h-POST (p = 0.037). There was no impact of protein supplementation on muscle soreness POST (p = 0.605), 24 h-POST (p = 0.182) or 40 h-POST (p = 0.333). All groups had increased concentrations of urinary myoglobin and 3-methylhistidine, but there was no statistical difference between groups at any timepoint (p > 0.05). We conclude that pre-sleep protein supplementation does not accelerate acute muscle recovery following load carriage in British Army recruits during basic training. The data suggests that consuming additional energy in the form of CHO or protein was beneficial at attenuating EIMD, although it is acknowledged there were no statistical differences between groups. Although EIMD did occur as indicated by elevated urinary muscle damage markers, it is likely that the load carriage test was not arduous enough to reduce muscle function, limiting the impact of protein supplementation. Practically, protein supplementation above protein intakes of 1.2 g⸱kg⁻¹⸱day⁻¹ following load carriage over similar distances (4 km) and carrying similar loads (15–20 kg) does not appear to be warranted.
... Protein synthesis and turnover were upregulated both in response to acute AE and the combination of acute AE and PI but not in response to PI alone, which indicated that acute AE had a strong effect on protein synthesis and turnover and this effect may be enhanced when PI was added. This is reasonable in that muscle contraction during exercise, whether RE or EE, has a profound effect on muscle protein turnover [72]. These findings were also consistent with the reports from previous RCTs [73,74], which indicated that PI alone could not modulate myofibrillar protein synthesis (MyoPS) rates that were caused by disuse, while pre-sleep protein ingestion could stimulate myofibrillar and mitochondrial protein synthesis during an overnight recovery from AE. ...
This study aimed to provide a more comprehensive molecular insight into the effects of aerobic exercise (AE), protein intake (PI), and AE combined with PI on human skeletal muscle by comparing their transcriptomic profiles. Fourteen published datasets obtained from the Gene Expression Omnibus (GEO) database were used. The hub genes were identified in response to acute AE (ACTB, IL6), training AE (UBB, COL1A1), PI (EZH2), acute AE combined with PI (DDIT3), and training AE combined with PI (MYC). Both FOS and MYC were upregulated in response to acute AE, and they were, respectively, downregulated by higher PI and a combination of AE and PI. COL1A1 was upregulated by training AE but was downregulated by higher PI. Results from the gene set enrichment analysis (p < 0.05 and FDR < 25%) showed that AE and PI delivered their impacts on human skeletal muscle in analogous pathways, including aerobic respiration, mitochondrial complexes, extracellular matrix (ECM) remodeling, metabolic process, and immune/inflammatory responses, whereas, PI may attenuate the response of immune/inflammation and ECM remodeling which would be promoted by AE, irrespective of its types. Compared to PI alone, acute AE combined with PI would further promote protein turnover and synthesis, but suppress skeletal muscle contraction and movement.
... The reasons for such interrogations are twofold. First, data in the field indicate that muscle protein synthesis (rather than muscle proteolysis) is more responsive to mechanical loading during well-fed states (579,580), and Brook et al. (581) have similarly suggested that ". . .the measurement of [muscle protein synthesis] remains a cornerstone for understanding the control of hypertrophy-mainly because it is the underlying driving force behind skeletal muscle hypertrophy." ...
Mechanisms underlying mechanical overload-induced skeletal muscle hypertrophy have been extensively researched since the landmark report by Morpurgo (1897) of "work-induced hypertrophy" in dogs that were treadmill-trained. Much of the pre-clinical rodent and human resistance training research to date supports that involved mechanisms include enhanced mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, an expansion in translational capacity through ribosome biogenesis, increased satellite cell abundance and myonuclear accretion, and post-exercise elevations in muscle protein synthesis rates. However, several lines of past and emerging evidence suggest additional mechanisms that feed into or are independent of these processes are also involved. This review will first provide a historical account as to how mechanistic research into skeletal muscle hypertrophy has progressed. A comprehensive list of mechanisms associated with skeletal muscle hypertrophy is then outlined and areas of disagreement involving these mechanisms are presented. Finally, future research directions involving many of the discussed mechanisms will be proposed.
... The smaller changes in lean body mass in women might be due to older women"s decreased hypertrophy capacity in response to RE and their impaired ability to increase muscle protein synthesis after protein consumption. 40 However, more research is needed to substantiate this. ...
... Since there is little evidence to suggest sex differences in the anabolic response from RET with similar training statues [20], we opted to include male and female subjects. While hormonal variation does appear to uniquely impact women physiologically, there is no clear evidence that the menstrual cycle or oral contraceptive use significantly influences physical performance [21,22]. ...
Background
Resistance exercise training (RET) is a common and well-established method to induce hypertrophy and improvement in strength. Interestingly, fish oil supplementation (FOS) may augment RET-induced adaptations. However, few studies have been conducted on young, healthy adults.
Methods
A randomized, placebo-controlled design was used to determine the effect of FOS, a concentrated source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), compared to placebo (PL) on RET-induced adaptations following a 10-week RET program (3 days·week⁻¹). Body composition was measured by dual-energy x-ray absorptiometry (LBM, fat mass [FM], percent body fat [%BF]) and strength was measured by 1-repetition maximum barbell back squat (1RMSQT) and bench press (1RMBP) at PRE (week 0) and POST (10 weeks). Supplement compliance was assessed via self-report and bottle collection every two weeks and via fatty acid dried blood spot collection at PRE and POST. An a priori α-level of 0.05 was used to determine statistical significance and Cohen’s d was used to quantify effect sizes (ES).
Results
Twenty-one of 28 male and female participants (FOS, n = 10 [4 withdrawals]; PL, n = 11 [3 withdrawals]) completed the 10-week progressive RET program and PRE/POST measurements. After 10-weeks, blood EPA+DHA substantially increased in the FOS group (+109.7%, p< .001) and did not change in the PL group (+1.3%, p = .938). Similar between-group changes in LBM (FOS: +3.4%, PL: +2.4%, p = .457), FM (FOS: −5.2%, PL: 0.0%, p = .092), and %BF (FOS: −5.9%, PL: −2.5%, p = .136) were observed, although, the between-group ES was considered large for FM (d = 0.84). Absolute and relative (kg·kg [body mass]⁻¹) 1RMBP was significantly higher in the FOS group compared to PL (FOS: +17.7% vs. PL: +9.7%, p = .047; FOS: +17.6% vs. PL: +7.3%, p = .011; respectively), whereas absolute 1RMSQT was similar between conditions (FOS: +28.8% vs. PL: +20.5%, p = .191). Relative 1RMSQT was higher in the FOS group (FOS: +29.3% vs. PL: +17.9%, p = .045).
Conclusions
When combined with RET, FOS improves absolute and relative 1RM upper-body and relative 1RM lower-body strength to a greater extent than that observed in the PL group of young, recreationally trained adults.
... Endurance exercise, such as jogging or walking, enhances moderately the loads on the skeleton above gravity, so it does not increase muscle cross-sectional area (CSA), which is directly related to muscle strength and power. [17,18] However, resistance exercise, such as weight training, is known to prevent the pathology of osteoporosis. [19,20] Therefore, a combination of walking and resistance exercise is expected to have a greater impact on muscle mass and bone structure or bone density than just walking. ...
Background:
This study aimed to analyze the effects of walking and resistance exercises on bone structure, bone mineral density (BMD), and skeletal muscle mass. We used data from the fourth Korean National Health and Nutrition Examination Survey (KNHANES).
Methods:
A total of 3,477 participants aged ≥19 years underwent hip structural analysis (HSA), BMD, and skeletal muscle index (SMI). All radiologic evaluations were performed using dual energy X-ray absorptiometry (DXA). The Korean short version of the International Physical Activity Questionnaire was used to measure physical activity status. The physical activity recommendations of the American College of Rheumatology Work Group Panel were used to evaluate the extent of activity.
Results:
The BMD and SMI in the group in which walking activity was performed 5 days or more per week for at least 30 min per day were significantly higher than those in the group in which walking activity was not performed. HSA and SMI in the group in which resistance exercise was performed 2 days or more per week for at least 30 min per day were found to be significantly higher than those in the group in which strengthening exercises were not performed.
Conclusions:
If resistance exercise and walking are combined, bone loss and muscle loss are prevented maintaining cortical thickness in the elderly. Walking for more than 5 days a week and resistance exercise for more than 2 days a week will help to maintain the skeletal muscle as well as the cortex around the femur neck, thus helping to prevent fragility fractures in older individuals.
... While initial research had suggested a greater muscle protein synthetic response to resistance training when nutritional support was provided before compared with after resistance exercise (Tipton et al., 2001), this has not been replicated elsewhere (Fujita et al., 2009;Tipton et al., 2007). Consequently, current guidelines advocate protein ingestion at a time that coincides with maximal stimulation of muscle protein synthesis, which is after exercise (Burd, Tang, Moore, & Phillips, 2009). ...
... Acute exercise combined with protein or amino acid intake can enhance muscle protein anabolic response by activating the mTORC1 pathway, which is beneficial to promoting post-exercise recovery [55]. In this study, although the supplementation with L-PS23 or HK-PS23 probiotics alone may promote the absorption and utilization of protein in the diet, thereby promoting muscle recovery ( Figure 3A,B), further research is still needed. ...
Excessive, high-intensity or inappropriate exercise may cause muscle damage. How to speed up recovery and reduce exercise discomfort are currently very important issues for athletes and sports people. Past research has shown that probiotics can improve inflammation and oxidative stress, as well as improve exercise performance and antifatigue. However, further research is needed to confirm the recovery benefits for muscle damage. In this double-blind design study, all subjects were randomly assigned to placebo, a live Lactobacillus paracasei group (L-PS23, 2 × 1010 colony forming unit (CFU)/day), or a heat-killed L. paracasei group (HK-PS23, 2 × 1010 cells/day), and supplemented for six consecutive weeks. Afterwards, subjects completed 100 maximal vertical jumps to bring about exercise-induced muscle damage (EIMD). Countermovement jump (CMJ), isometric mid-thigh pull (IMTP), and Wingate anaerobic test (WAnT), as well as blood tests for markers of muscle damage and inflammation were made pre-exercise and 3, 24, 48 h post exercise. The results show that both L-PS23 and HK-PS23 supplementation significantly slowed the loss of muscle strength after muscle injury, and they significantly reduced the production of markers of muscle damage and inflammation (p < 0.05). In addition, L-PS23 and HK-PS23 had the benefits of accelerating the recovery and improvement of muscle strength, the blood markers of muscle injury and inflammation, and slowing the decline in testosterone concentrations (p < 0.05). Especially in the HK-PS23 supplemented group, there was a better trend. In conclusion, we found that L-PS23 or HK-PS23 supplementation for six weeks prevented strength loss after muscle damage and improved blood muscle damage and inflammatory markers, with protective, accelerated recovery and anti-fatigue benefits.
... Participants were considered resistance trained if they were engaged in resistance training >3 times per week for >3 months prior to taking part in the study. This population was selected as training status impacts the anabolic response to exercise (16) . Therefore, selecting resistance trained individuals ensured optimal exercise execution, (more) ecological validity (to exercise training) and an assumed greater homogeneity of responses to exercise. ...
Ingestion of mycoprotein stimulates skeletal muscle protein synthesis (MPS) rates to a greater extent than concentrated milk protein when matched for leucine content, potentially attributable to the whole-food nature of mycoprotein. We hypothesised that bolus ingestion of mycoprotein as part of its whole food matrix would stimulate MPS rates to a greater extent compared with a leucine matched bolus of protein concentrated from mycoprotein. Twenty-four healthy young (age; 21±2 y, BMI; 24±3 kg.m ² ) males received primed, continuous infusions of L-[ ring - ² H 5 ]phenylalanine and completed a bout of unilateral resistance leg exercise before ingesting either 70 g mycoprotein (MYC; 31.4 g protein, 2.5 g leucine; n =12) or 38.2 g of a protein concentrate obtained from mycoprotein (PCM; 28.0 g protein, 2.5 g leucine; n =12). Blood and muscle samples ( vastus lateralis ) were taken pre- and (4 h) post- exercise/protein ingestion to assess postabsorptive and postprandial myofibrillar protein fractional synthetic rates (FSRs) in resting and exercised muscle. Protein ingestion increased plasma essential amino acid and leucine concentrations ( P <0.0001), but more rapidly (both 60 vs 90 min; P <0.0001) and to greater magnitudes (1367 vs 1346 μmol·L ⁻¹ and 298 vs 283 μmol·L ⁻¹ , respectively; P <0.0001) in PCM compared with MYC. Protein ingestion increased myofibrillar FSRs ( P <0.0001) in both rested (MYC, Δ0.031±0.007%·h ⁻¹ and PCM, Δ0.020±0.008%·h ⁻¹ ) and exercised (MYC, Δ0.057±0.011%·h ⁻¹ and PCM, Δ0.058±0.012%·h ⁻¹ ) muscle, with no differences between conditions ( P >0.05). Mycoprotein ingestion results in equivalent postprandial stimulation of resting and post-exercise myofibrillar protein synthesis rates irrespective of whether it is consumed within or without its whole-food matrix.
... Maintaining the mass of skeletal muscle is of great importance in maintaining functional capacity and metabolic health. Muscle mass persistence is regulated by fluctuations in muscle protein synthesis and breakdown (7). Proteins obtained as a result of feed consumption stimulate muscle protein synthesis by providing substrates (i.e. ...
This study aimed to determine the metabolomic characteristics associated with the fattening performance of the Awassi lamb breed under intensive fattening for 90 days. Twenty-four lambs were used in the research. The lambs were divided into two groups according to their fattening performance (good fattening performance, n = 12, and poor fattening performance, n = 12), and their metabolomic properties were evaluated. The differences between the two research groups in the amino acids of alloisoleucine, aspartic acid, histidine, hydroxylysine, isoleucine, lysine, methionine, phenylalanine, tryptophan, valine, and 1-methylhistidine were found to be statistically significant (P ≤ 0.001). Moderately significant negative correlations were found between daily concentrate feed intake and 3-methylhistidine (r = −0.469; P = 0.021), hydroxylysine (r = −0.408; P = 0.048), and serotonin (r= −0.467; P = 0.021); as well as between the average daily weight gain (ADWG) and alloisoleucine (r = −0.528; P = 0.008), 3-methylhistidine (r = −0.440; P = 0.032), and hydroxylysine (r = −0.577; P = 0.003). A moderate positive correlation was found between hydroxyisovalerylcarnitine and ADWG (r = 0.476; P = 0.019), and a negative correlation was found between hydroxyisovalerylcarnitine and the feed conversion ratio (r = −0.430; P = 0.036). Pathway analysis revealed that the most important biological pathway was the phenylalanine, tyrosine, and tryptophan biosynthesis pathway. The results of the research reveal the potential for plasma free amino acid and carnitine profiles to be used as candidate biomarkers in the evaluation of fattening performance in lambs.
... Hormones and nutritional factors in the body can regulate MPS and MPB [5]. MPS is mainly affected by mechanical stimulation and amino acid intake [6]. Skeletal muscle protein is composed of 20 amino acids, and 9 of them are considered essential amino acids (EAAs) for humans. ...
Maintaining muscle quality throughout life is crucial to human health and well-being. Muscle is the most extensive form of protein storage in the human body; skeletal muscle mass is determined by the balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). MPB provides amino acids needed by various organs; however, excessive MPB, especially with aging, may cause loss of muscle mass and a decline in motor function, even threatening life. The turnover of muscle protein is vital to the health of humans. Thus, while the study of MPS and MPB has theoretical and practical significance, the network that controls MPS is very complicated and we cannot discuss both MPS and MPB in a single review. Therefore, this review mainly discusses the regulation of MPS, especially by amino acids. Amino acids regulate protein synthesis in cell and animal models, but compelling evidence for amino acids promoting protein synthesis in human muscles is ambiguous. In particular, studies on the stimulation of human MPS by branched-chain amino acids (BCAAs) have been inconsistent. Amino acids other than BCAAs such as threonine and tryptophan may also have MPS-stimulating effects, and alternatives to BCAAs, such as Beta-Hydroxy-Beta-Methyl butyrate (HMB) and branched-chain ketoacids (BCKAs) are also worthy of further investigation explore. Amino acids coordinate protein synthesis and degradation through the mechanistic target of rapamycin complex 1 (mTORC1); however, the amino acid-mTORC1-protein synthesis pathway is complex, and new insights into amino acid control continue to emerge. Understanding how amino acids control MPS is of forward-looking significance for treating muscle mass loss during human aging.
... Protein synthesis may be stimulated by different factors, including resistance training and dietary proteins (amino acids). It has been shown that resistance training and protein consumption independently stimulate muscle protein synthesis with (leg press) synergistic effects on skeletal muscle anabolism [29][30][31]. Thus, the association of these strategies may be considered a more effective alternative to promote an increase in lean body mass and attenuate the progression of sarcopenia in older individuals. ...
Background:
There are some controversial findings regarding the benefits of combining protein supplementation with resistance training in order to optimize adaptations to training in older adults.
Objective:
The aim of this review was to summarize the evidence from meta-analyses assessing the effects of protein supplementation combined with resistance training on body composition and muscle strength in the older population.
Methods:
We included systematic reviews with meta-analyses of randomized clinical trials that examined the effects of protein and/or amino acid supplementation associated with resistance training compared with resistance training alone on lean body mass, muscle mass, and muscle strength in older people. The search was performed using the MEDLINE (PubMed), Embase, Cochrane Database of Systematic Reviews, Google Scholar, and OpenGrey databases. Methodological quality was assessed using the Assessing the Methodological Quality of Systematic Reviews 2 checklist, and the quality of evidence was determined using the Grading of Recommendations Assessment, Development and Evaluation system. The pooled effect estimates were computed from the standardized mean difference and the 95% confidence interval achieved by each meta-analysis, using random effects models.
Results:
Five reviews were included, all of moderate methodological quality. In the analyses, protein supplementation combined with resistance training was associated with greater increases in lean body mass and muscle mass when compared with resistance training alone. However, no differences were observed between the interventions on muscle strength increases. The quality of evidence ranged from moderate to very low.
Conclusion:
Protein supplementation associated with resistance training induces greater increases in lean body mass compared with resistance training alone. In addition, it is suggested that the use of protein supplementation enhances gains in muscle mass but does not promote greater increases in muscle strength.
... Therefore, under the two synergistic effects, it has the benefit of increasing net muscle protein synthesis (Tipton et al., 1999;Franceschi et al., 2018). In addition, acute exercise combined with the ingestion of protein or amino acids can enhance the muscle protein anabolic response by activating the mTORC1 pathway, which is beneficial for promoting recovery following exercise and may improve muscle mass and quality over the long term (Burd et al., 2009). However, resistance training and protein supplementation are not as effective for the elderly as for the young, which is called the chronic slow response of the elderly (Kumar et al., 2009). ...
Background/Purpose: In recent years, the aging population has gradually increased, and the aging process is accompanied by health-associated problems, such as loss of muscle mass and weakness. Therefore, it is important to explore alternative strategies for improving the health status and physical fitness of the aged population. In this study, we investigated the effect of soy protein supplementation combined with resistance training on changes in the muscle mass, muscle strength, and functional activity performance of aging mice.
Methods: Female Institute of Cancer Research (ICR) mice were divided into four groups (n = 8 per group): sedentary control (SC), isolated soy protein (ISP) supplementation, resistance training (RT), and a combination of ISP and RT (ISP + RT). The mice in designated groups received oral ISP supplementation (0.123 g/kg/day), RT (5 days/week for a period of 4 weeks), or a combination of both ISP plus RT for 4 weeks. Afterward, we assessed muscle strength, endurance, and anaerobic endurance performance and analyzed blood biochemical and pathological tissue sections to investigate whether there were adverse effects or not in mice.
Results: ISP supplementation effectively improved the muscle mass, muscle endurance, and endurance performance of aging female mice. The RT group not only showed similar results with ISP but also increased muscle strength and glycogen content. Nevertheless, the combination of ISP supplementation and RT had greater beneficial effects on muscle strength, physical performance, and glycogen levels (p < 0.05). In addition, the combination of ISP supplementation and RT had significantly increased type II muscle percentage and cross-sectional area (p < 0.05).
Conclusion: Although ISP or RT alone improved muscle mass and performance, the combination of ISP with RT showed greater beneficial effects in aging mice. Our findings suggest that regular exercise along with protein supplementation could be an effective strategy to improve overall health and physical fitness among the elderly.
Antrenman bilimi, sporcuların performansını artırmak ve uzun vadeli başarı sağlamak için sürekli gelişen bir alan olmuştur. Ancak günümüzün dinamik spor dünyasında, sadece kısa vadeli performans artışı değil, uzun süreli sürdürülebilir bir gelişim de giderek daha fazla önem kazanmaktadır. Sürdürülebilirlik kavramı, antrenman bilimi içinde, hem sporcuların fiziksel ve zihinsel sağlığını korumayı hem de spor kaynaklarını ve çevresel etkiyi optimize etmeyi içerir. Bu bağlamda, sürdürülebilir bir antrenman yönetimi, sporcuların uzun yıllar boyunca en üst düzeyde performans gösterebilmesi ve sporun gelecek nesiller için aynı etkiyi devam ettirebilmesi açısından kritik bir rol oynamaktadır. Antrenman bilimi alanında sürdürülebilirlik, üç temel bileşen etrafında şekillenir: fizyolojik, psikolojik ve çevresel. Fizyolojik sürdürülebilirlik, sporcuların aşırı antrenman, sakatlık ve yorgunluk gibi sorunlarla karşılaşmadan gelişimlerini sürdürebilmelerini sağlamayı hedefler. Psikolojik sürdürülebilirlik ise sporcuların zihinsel dayanıklılığını artırarak, motivasyonlarının uzun süre devam etmesine katkı sağlar. Çevresel sürdürülebilirlik ise antrenman süreçlerinde kullanılan malzeme, ekipman ve tesislerin çevre dostu olmasını ve antrenmanların doğaya minimum zarar vermesini içerir. Bu noktada, nitel araştırmalar, sürdürülebilir antrenman uygulamalarının anlaşılması ve geliştirilmesi açısından önemli bir yöntemdir. Niteliksel araştırma yöntemleri, sporcuların bireysel deneyimlerini, antrenörlerin stratejilerini ve uzun vadeli başarı planlarını daha derinlemesine anlamamıza olanak tanır. Mülakatlar, vaka incelemeleri ve katılımcı gözlem gibi nitel yöntemler, sürdürülebilir antrenman programlarının nasıl yapılandırılması gerektiği konusunda değerli bilgiler sunar. Örneğin, nitel araştırmalar yoluyla sporcuların antrenman süreçlerinde karşılaştıkları zorluklar, motivasyon kayıpları ya da sürdürülebilir bir başarı için hangi stratejilerin daha etkili olduğu gibi sorulara yanıt bulmak mümkündür. Aynı şekilde, antrenörlerin sürdürülebilirlik konusundaki bakış açıları, bu alandaki politikaların ve uygulamaların iyileştirilmesine yardımcı olabilir. Bu kitap, antrenman bilimi alanında sürdürülebilirlik konusunu derinlemesine ele almakta ve bu süreçte nitel araştırmaların nasıl bir katkı sağladığını irdelemektedir. Kitap boyunca, antrenmanların sürdürülebilirliğini artırmak için kullanılabilecek stratejilere ve bu stratejilerin uygulanabilirliğini destekleyen nitel araştırma bulgularına yer verilecektir. Sporcu sağlığı ve performansının sürdürülebilirliği üzerine odaklanan bu çalışma hem akademisyenler hem de pratikte çalışan antrenörler için değerli bir kaynak olmayı hedeflemektedir. Ayrıca bu kitap Sürdürülebilir Spor ve Niteliksel Araştırmalar Serimizin üçüncü kitabını oluşturmaktadır. Alan yazına bilimsel olarak büyük anlamlar katacak bir araştırma kitabı olması temennisiyle.
Plant proteins are increasingly seen as critical nutrient sources for both amateur and professional athletes. The aim of the presented study was to review the inventions and experimental articles referring to the application of plant-based proteins, peptides and amino acids in food products dedicated to sportspeople and published in the period 2014–2023. The literature search was conducted according to PRISMA statementsacross several key databases, including Scopus and ISI Web of Science. Altogether, 106 patents and 35 original articles were found. The survey of patents and inventions described in the articles showed the use of 52 taxa (mainly annual herbaceous plants), creating edible seeds and representing mainly the families Fabaceae and Poaceae. The majority of inventions were developed by research teams numbering from two to five scientists, affiliated in China, The United States of America and Japan. The greatest number of inventions applied plant-based proteins (especially protein isolates), declared the nutritional activity and were prepared in liquid or solid consistency. According to the reviewed studies, the intake of soybean and potato proteins might provide better results than animal-based protein (excluding resistance training), whereas the consumption of pea and rice protein does not possess any unique anabolic properties over whey protein. The analysis of other investigations demonstrated the varied acceptability and consumption of food products, while the high rating of the tested food products presented in four articles seems to be an effect of their sensual values, as well as other elements, such as production method, health benefits and cost-effectiveness. Considering the great potential of useful plant species, it might be concluded that future investigations focusing on searching for novel plant protein sources, suitable for the preparation of food products dedicated to amateur and professional sportspeople, remain of interest.
Sarcopenia is a process of progressive aging-associated loss of skeletal muscle mass (SMM) recognized as a serious global health issue contributing to frailty and increased all-cause mortality. Exercise and nutritional interventions (particularly intake of dairy products and milk) demonstrate good efficacy, safety, and broad applicability. Here, we propose that at least some of the well-documented favorable effects of milk and milk-derived protein supplements on SMM might be mediated by D-galactose, a monosaccharide present in large quantities in milk in the form of disaccharide lactose (milk sugar). We suggest that ingestion of dairy products results in exposure to D-galactose in concentrations metabolized primarily via the Leloir pathway with the potential to (i) promote anabolic signaling via maintenance of growth factor (e.g., insulin-like growth factor 1 [IGF-1]) receptor mature glycosylation patterns; and (ii) provide extracellular (liver glycogen) and intracellular substrates for short (muscle glycolysis) and long-term (muscle glycogen, intramyocellular lipids) energy availability. Additionally, D-galactose might optimize the metabolic function of skeletal muscles by increasing mitochondrial content and stimulating glucose and fatty acid utilization. The proposed potential of D-galactose to promote the accretion of SMM is discussed in the context of its therapeutic potential in sarcopenia.
Introduction Pea protein is an attractive non-animal derived protein source to support dietary protein requirements. However, while high in leucine, a low methionine content has been suggested to limit its anabolic potential. Mycoprotein has a complete amino acid profile which, at least in part, may explain its ability to robustly stimulate MyoPS rates. We hypothesised that an inferior post-exercise MyoPS response would be seen following ingestion of pea protein compared with mycoprotein, which would be (partially) rescued by blending the two sources. Methods Thirty-three healthy, young (age; 21±1 y, BMI; 24±1 kg٠m-2) and resistance trained participants received primed, continuous infusions of L-[ring-2H5]phenylalanine and completed a bout of whole-body resistance exercise before ingesting 25 g protein from mycoprotein (MYC, n=11), pea protein (PEA, n=11) or a blend (39% MYC, 61% PEA) of the two (BLEND, n=11). Blood and muscle samples were taken pre-, 2 h and 4 h post- exercise/protein ingestion to assess postabsorptive and postprandial post-exercise myofibrillar protein fractional synthetic rates (FSRs). Results Protein ingestion increased plasma essential amino acid and leucine concentrations (time effect; P<0.0001), but more rapidly in BLEND and PEA compared with MYC (time x condition interaction; P<0.0001). From similar postabsorptive values (MYC, 0.026±0.008%·h-1; PEA, 0.028±0.007%·h-1; BLEND, 0.026±0.006%·h-1), resistance exercise and protein ingestion increased myofibrillar FSRs (time effect; P<0.0001) over a 4 h postprandial period (MYC, 0.076±0.004%·h-1; PEA, 0.087±0.01%·h-1; BLEND, 0.085±0.01%·h-1), with no differences between groups (all; P>0.05). Conclusions These data show that all three non-animal derived protein sources have utility in supporting post-exercise muscle reconditioning.
ÖZET
Kuersetin ve Resveratrol Tüketiminin Elit Adölesan Atletizm Mesafe
Koşucularının Laktik Asit Düzeyleri ile Koşu Performansı Üzerine Etkilerinin
İncelenmesi
Bu çalışmanın amacı kuersetin ve resveratrol tüketiminin elit adölesan atletizm
mesafe koşucularının laktik asit düzeyleri ile koşu performansı üzerine etkilerinin
incelenmesidir.
Araştırmaya Isparta ilinde bulunan elit düzeyde atletizm ile ilgilenen 4 kadın
ve 4 erkek adölesan sporcu katılmıştır. Çalışmaya katılan elit adölesan atletlerin yaş
ortalamaları 16,13±2,03 yıl, sporcuların vücut ağırlığı ortalamaları 52,02±6,91 kg, boy
ortalamaları ise 168,3±10,61 cm olarak tespit edilmiştir. Adölesan sporcuların
performanslarına kuersetin ve resveratrolün etkisini ölçmek için çalışma birer hafta ara ile 3 hafta sürmüştür. Her haftanın belirlenen 2 günü kampa alınarak ilk hafta plasebo, ikinci hafta 500 mg kuersetin ve üçüncü hafta 100 mg resveratrol takviyeleri verilmiştir. Kampın ilk günü takviyesiz 1500 m koşmaları istenmiştir. Koşu öncesi ve sonrası laktik asit ölçümü alınmış ve koşu süreleri kaydedilmiştir. İkinci günü ise takviyeler verilerek aynı ölçümler tekrarlanmıştır. Araştırmada; lactate scout,
kronometre ve bioelektrik direnç ölçüm cihazı kullanılmıştır. Elde edilen verilerin
analizi için Paired – T Testi ve Korelasyon Testlerinden faydalanılmıştır, anlamlılık
düzeyi 0,05 olarak kabul edilmiştir.
Elde edilen bulgulara bakıldığında; Kuersetin takviyesinin akut etkisinin kadın
sporcularda biriken laktik asit seviyelerinde anlamlı düzeyde olduğu, erkeklerde ise
koşu süresinde fark oluşturmasına rağmen istatistiksel olarak anlamlı olmadığı,
resveratrol takviyesinde ise akut etkinin olmadığı dolayısıyla anlamlı bir sonuç
çıkmadığı tespit edilmiştir.
Sonuç olarak; kuersetin ve resveratrol müdahalelerinde yalnızca kuersetin
takviyesinin kadın elit adölesan atletlerde istatistiksel olarak anlamlı fark yarattığı
görülmüştür. Fakat istatistiksel olarak anlamlı çıkmasa da Atletizm spor dalı için çok
önemli olan koşu süresi farklılıkları ile karşılaşılmıştır. Dolayısıyla bu çalışmanın
özellikle kadın ve nispeten erkek sporcular için kuersetin takviyesinin laktik asit
seviyelerini azalttığı, yorgunluğun gecikmesini sağlayarak daha iyi bir performans
gösterebileceğini anlatan bir çalışma olduğu söylenebilmektedir.
Anahtar Kelimler: Kuersetin, Resveratrol, Laktik Asit, Yorgunluk, Sportif
Performans, Adölesan, Kadın Sporcular, Besin Takviyesi,
Atletizm
ABSTRACT
Investigation of the Effects of Quercetin and Resveratrol Consumption on
Lactic Acid Levels and Running Performance of Elite Adolescent Athletics
Distance Runners
The aim of this study is to investigate the effects of quercetin and resveratrol
consumption on the lactic acid levels and running performance of elite adolescent
athletics distance runners.
4 women and 4 male adolescent athletes interested in elite athletics in Isparta
province participated in the study. The average age of elite adolescent athletes
participating in the study was 16.13 ± 2.03 years, the average weight of athletes was 52.02 ± 6.91 kg, and the average height was 168.3 ± 10.61 cm. The study took 3 weeks, one week apart, to measure the effect of quercetin and resveratrol on the performance of adolescent athletes. The two days of each week were taken to the camp and the first week was given placebo, the second week was 500 mg quercetin and the third week was 100 mg resveratrol supplements. On the first day of the camp, they were asked to run 1500 m without reinforcement. Before and after the run, lactic acid measurement was taken and the running times were recorded. On the second day, the same measurements were repeated with supplements. In the study; lactate scout, stopwatch and bioelectric resistance measurement device were used. Paired - T Test and Correlation Tests were used for the analysis of the data obtained, the significance level was accepted as 0.05.
Considering the findings obtained; It has been determined that the acute
effect of quercetin supplement is significant in lactic acid levels accumulated in female athletes, although it is not statistically significant in males despite the difference in running time, and there is no significant result in resveratrol supplement due to the absence of acute effect.
As a result; In quercetin and resveratrol interventions, only quercetin
supplementation was found to make a statistically significant difference in female elite adolescent athletes. However, although not statistically significant, differences in running time, which are very important for Athletics sports branch, were encountered. Therefore, it can be said that this study is a study explaining that quercetin supplementation decreases lactic acid levels, especially for female and relatively male athletes, and provides a better performance by providing delay of fatigue.
Key Words: Quercetin, Resveratrol, Lactic Acid, Fatigue, Sporty Performance,
Adolescent, Women Athletes, Nutritional Supplement, Athletic
Collegiate athletes are valuable assets of the University. Their athletic performance requires a high level of competitiveness to achieve commendable record standing; thus, nutrition plays an important role. Their dietary habits and how knowledgeable they are about proper nutrition are the primary concern of this study that will probably affect their performance. The purpose of the study is to determine if there is a relationship between Dietary Habits and Nutritional Knowledge. Also, to investigate if these two variables serve as a predictor of Athletic Performance among selected UST collegiate athletes. The descriptive- Correlational design was used in the study. Respondents were identified using the purposive sampling technique and stratified random sampling. 100 Team A selected collegiate athletes from the University of Santo Tomas who participated in the UAAP Season '80 were surveyed and completed a Dietary Habits and Nutritional Knowledge Questionnaire developed by Paugh (2005). Data were analyzed using Regression and Pearson Correlation Coefficient at an alpha level of .05. The results revealed that respondents practiced good dietary habits and had a good knowledge of nutrition with a General Weighted Mean of 2.70 and 3.02, respectively. There is a significant relationship between dietary habits and nutritional knowledge. Dietary habit predicts athletic performance while nutritional knowledge does not predict athletic performance.The researchers highly recommend the full support/assistance of Coaches/Athletic Trainers/ Sports Conditioning Coach, and Parents in guiding the nutritional diet of student-athlete and the availability of Sport Dietician to implement a dietary plan for student-athletes to reach their optimal athletic performance.
Keywords: Dietary Habits, Nutritional Knowledge, Athletic Performance, Collegiate Athletes, Nutrition
This study investigated the aminoacidemia after ingestion of a poultry protein hydrolysate (PPH) and whey protein in healthy young and old participants. Protein-drinks were also digested using the INFOGEST static in vitro digestion model to simulate gastrointestinal changes in young and old adults. In fasted state, 10 young (20-40y) and 10 old (70-80y) ingested PPH or whey as a 20 g protein-drink and blood samples were collected. Plasma leucine concentration increased more when ingesting whey than PPH (young 62 ± 27 vs. 48 ± 27%, old 94 ± 57 vs. 66 ± 26%) but the peak concentration was reached faster after drinking PPH (p
Mass spectrometry has developed into a platform for the assessment of health, sensory, quality and safety aspects of food. Current nutrition research focuses on unravelling the link between acute or chronic dietary and nutrient intake and the physiological effects at cellular, tissue and whole body level. The bioavailability and bioefficacy of food constituents and dose-effect correlations are key to understanding the impact of food on defined health outcomes. To generate this information, appropriate analytical tools are required to identify and quantify minute amounts of individual compounds in highly complex matrices (such as food or biological fluids) and to monitor molecular changes in the body in a highly specific and sensitive manner. Mass spectrometry has become the method of choice for such work and now has broad applications throughout all areas of nutrition research. This book focuses the contribution of mass spectrometry to the advancement of nutrition research. Aimed at students, teachers and researchers, it provides a link between nutrition and analytical biochemistry. It guides nutritionists to the appropriate techniques for their work and introduces analytical biochemists to new fields of application in nutrition and health. The first part of the book is dedicated to the assessment of macro- and micro-nutrient status with a view to making dietary recommendations for the treatment of diet-related diseases. The second part shows how mass spectrometry has changed nutrition research in fields like energy metabolism, body composition, protein turnover, immune modulation and cardiovascular health.
Purpose
Exercise training plays an important role in maintaining the bone health and prevention of osteoporosis or age-related bone loss. Aerobic exercise, resistance exercise or a combination of both are used to maintain bone health. Mechanical loading induced by resistance exercise stimulates a number of mechanisms that help to maintain or improve bone mineral density. The present review article aims at summarizing the mechanisms and the use of resistance exercises for improving or maintaining the bone and muscle mass.
Methodology
Literature search was done using PubMed Central, CINAHL, sciencedirect.com with keywords resisted exercises, osteoporosis, postmenopausal and effect of resisted exercises in osteoporosis.
Results
Resistance exercises have a significant effect in maintaining the musculoskeletal health. Mechanical loading of the bone especially with high intensity exercises, leads to an improvement in the bone mineral density.
Conclusion
Resistance exercises may help to regulate the bone health and prevent the development of osteoporosis. These can be included in the exercise programmes designed for osteoporotic or postmenopausal patients.
This year’s 39th International Symposium on Diabetes and Nutrition in Anavyssos, Greece, hosted a series of presentations and plenary lectures with a focus on the effects of weight loss, micronutrients, nutritional supplements, and alternative dietary patterns in the prevention and management of Type 2 diabetes (T2D) and cardiovascular risk reduction. Michael Lean discussed how diabetes remission can be achieved through weight loss using a low-energy diet (LED) or very low-energy diet (VLED), accompanied by continued long-term support from specialised healthcare professionals. Jeffrey Mechanick discussed the importance and impact of early intervention on T2D and cardiovascular disease (CVD). He emphasised that T2D should be seen not just at the point of disease, but on a spectrum from prediabetes to complications, with early interventions having significant impact on not only the progression of T2D, but also into the latter stages.Simin Liu presented an integrative multilevel framework for causal inference to personalise cardiometabolic health, highlighting recent work investigating the roles of dietary minerals, environment metals, and genomics in relation to cardiovascular disease and diabetes. Several of the presentations included discussion of specific interventions. Daniel West discussed the use of whey protein (WP) and how it can help control postprandial glycaemic excursions (PGE) in people with T2D controlled on oral antihyperglycaemic drugs. Following this, Andrea Hawkinson discussed how a new supplement, mulberry leaf (Morus alba) extract (MLE), can significantly lower postprandial glucose response, as well as early insulin response, highlighting the need for further studies to evaluate its efficacy in people with T2D. Philip Atherton showed studies providing evidence that protein and essential amino acid (EAA) supplementation can help support muscle mass, which is especially essential for older people with T2D and sarcopenia. Finally, Jose-María López-Pedrosa spoke about how a supplement containing slow digestible carbohydrates (SDC), arginine, lysine, and β-hydroxy-β-methylbutyric acid (HMB) can help preserve muscle mass, as well as improve insulin resistance, in a rat model of diabetes.
Background: Resistance exercise leads to net muscle protein accretion through a synergistic interaction of exercise and feeding. Proteins from different sources may differ in their ability to support muscle protein accretion because of different patterns of postprandial hyperaminoacidemia.
Objective: We examined the effect of consuming isonitrogenous, isoenergetic, and macronutrient-matched soy or milk beverages (18 g protein, 750 kJ) on protein kinetics and net muscle protein balance after resistance exercise in healthy young men. Our hypothesis was that soy ingestion would result in larger but transient hyperaminoacidemia compared with milk and that milk would promote a greater net balance because of lower but prolonged hyperaminoacidemia.
Design: Arterial-venous amino acid balance and muscle fractional synthesis rates were measured in young men who consumed fluid milk or a soy-protein beverage in a crossover design after a bout of resistance exercise.
Results: Ingestion of both soy and milk resulted in a positive net protein balance. Analysis of area under the net balance curves indicated an overall greater net balance after milk ingestion (P < 0.05). The fractional synthesis rate in muscle was also greater after milk consumption (0.10 ± 0.01%/h) than after soy consumption (0.07 ± 0.01%/h; P = 0.05).
Conclusions: Milk-based proteins promote muscle protein accretion to a greater extent than do soy-based proteins when consumed after resistance exercise. The consumption of either milk or soy protein with resistance training promotes muscle mass maintenance and gains, but chronic consumption of milk proteins after resistance exercise likely supports a more rapid lean mass accrual.
The speed of absorption of dietary amino acids by the gut varies according to the type of ingested dietary protein. This could
affect postprandial protein synthesis, breakdown, and deposition. To test this hypothesis, two intrinsically 13C-leucine-labeled milk proteins, casein (CAS) and whey protein (WP), of different physicochemical properties were ingested
as one single meal by healthy adults. Postprandial whole body leucine kinetics were assessed by using a dual tracer methodology.
WP induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia,
probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not
after WP ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with
the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 ± 91 μmol⋅kg−1) than with WP (373 ± 56 μmol⋅kg−1). Leucine intake was identical in both meals (380 μmol⋅kg−1). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP (P < 0.05, WP vs. CAS). In conclusion, the speed of protein digestion and amino acid absorption from the gut has a major effect
on whole body protein anabolism after one single meal. By analogy with carbohydrate metabolism, slow and fast proteins modulate
the postprandial metabolic response, a concept to be applied to wasting situations.
Six men were studied to determine the interrelationships among blood supply, motor unit (MU) activity and lactate concentrations during intermittent isometric contractions of the hand grip muscles. The subjects performed repeated contractions at 20% of maximal voluntary contraction (MVC) for 2 s followed by 2-s rest for 4 min with either unhindered blood circulation or arterial occlusion given between the 1st and 2nd min. The simultaneously recorded intramuscular MU spikes and surface electromyogram (EMG) data indicated that mean MU spike amplitude, firing frequency and the parameters of surface EMG power spectra (mean power frequency and root mean square amplitude) remained constant during the experiment with unhindered circulation, providing no electrophysiological signs of muscle fatigue. Significant increases in mean MU spike amplitude and frequency were, however, evident during the contractions with arterial occlusion. Similar patterns of significant changes in the surface EMG spectra parameters and venous lactate concentration were also observed, while the integrated force-time curves remained constant. These data would suggest that the metabolic state of the active muscles may have played an important role in the regulation of MU recruitment and rate coding patterns during exercise.
The nature of the deficit underlying age-related muscle wasting remains controversial. To test whether it could be due to a poor anabolic response to dietary amino acids, we measured the rates of myofibrillar and sarcoplasmic muscle protein synthesis (MPS) in 44 healthy young and old men, of similar body build, after ingesting different amounts of essential amino acids (EAA). Basal rates of MPS were indistinguishable, but the elderly showed less anabolic sensitivity and responsiveness of MPS to EAA, possibly due to decreased intramuscular expression, and activation (phosphorylation) after EAA, of amino acid sensing/signaling proteins (mammalian target of rapamycin, mTOR; p70 S6 kinase, or p70(S6k); eukaryotic initiation factor [eIF]4BP-1; and eIF2B). The effects were independent of insulin signaling since plasma insulin was clamped at basal values. Associated with the anabolic deficits were marked increases in NFkappaB, the inflammation-associated transcription factor. These results demonstrate first, EAA stimulate MPS independently of increased insulin availability; second, in the elderly, a deficit in MPS in the basal state is unlikely; and third, the decreased sensitivity and responsiveness of MPS to EAA, associated with decrements in the expression and activation of components of anabolic signaling pathways, are probably major contributors to the failure of muscle maintenance in the elderly. Countermeasures to maximize muscle maintenance should target these deficits.
Muscle growth is associated with an activation of the mTOR signaling pathway and satellite cell regulators. The purpose of this study was to determine whether 17 selected genes associated with mTOR/muscle protein synthesis and the satellite cells/myogenic program are differentially expressed in young and older human skeletal muscle at rest and in response to a potent anabolic stimulus [resistance exercise + essential amino acid ingestion (RE+EAA)]. Twelve male subjects (6 young, 6 old) completed a bout of heavy resistance exercise. Muscle biopsies were obtained before and at 3 and 6 h post RE+EAA. Subjects ingested leucine-enriched essential amino acids at 1 h postexercise. mRNA expression was determined using qRT-PCR. At rest, hVps34 mRNA was elevated in the older subjects (P < 0.05) while there was a tendency for levels of myoD, myogenin, and TSC2 mRNA to be higher than young. The anabolic stimulus (RE+EAA) altered mRNAs associated with mTOR regulation. Notably, REDD2 decreased in both age groups (P < 0.05) but the expression of Rheb mRNA increased only in the young. Finally, cMyc mRNA was elevated (P < 0.05) in both young and old at 6 h post RE+EAA. Furthermore, RE+EAA also increased expression of several mRNAs associated with satellite function in the young (P < 0.05), while expression of these mRNAs did not change in the old. We conclude that several anabolic genes in muscle are more responsive in young men post RE+EAA. Our data provide new insights into the regulation of genes important for transcription and translation in young and old human skeletal muscle post RE+EAA.
The purpose of this study was to investigate the magnitude and time course for changes in muscle protein synthesis (MPS) after a single bout of resistance exercise. Two groups of six male subjects performed heavy resistance exercise with the elbow flexors of one arm while the opposite arm served as a control. MPS from exercised (ex) and control (con) biceps brachii was assessed 4 (group A) and 24 h (group B) postexercise by the increment in L-[1-13C]leucine incorporation into muscle biopsy samples. In addition, RNA capacity and RNA activity were determined to assess whether transcriptional and/or translational processes affected MPS. MPS was significantly elevated in biceps of the ex compared with the con arms of both groups (group A, ex 0.1007 +/- 0.0330 vs. con 0.067 +/- 0.0204%/h; group B ex 0.0944 +/- 0.0363 vs. con 0.0452 +/- 0.0126%/h). RNA capacity was unchanged in the ex biceps of both groups relative to the con biceps, whereas RNA activity was significantly elevated in the ex biceps of both groups (group A, ex 0.19 +/- 0.10 vs. con 0.12 +/- 0.05 micrograms protein.h-1.microgram-1 total RNA; group B, ex 0.18 +/- 0.06 vs. con 0.08 +/- 0.02 micrograms protein.h-1.microgram-1 total RNA). The results indicate that a single bout of heavy resistance exercise can increase biceps MPS for up to 24 h postexercise. In addition, these increases appear to be due to changes in posttranscriptional events.
Previous studies using indirect means to assess the response of protein metabolism to exercise have led to conflicting conclusions. Therefore, in this study we have measured the rate of muscle protein synthesis in normal volunteers at rest, at the end of 4 h of aerobic exercise (40% maximal O2 consumption), and after 4 h of recovery by determining directly the rate of incorporation of 1,2-[13C]leucine into muscle. The rate of muscle protein breakdown was assessed by 3-methylhistidine (3-MH) excretion, and total urinary nitrogen excretion was also measured. There was an insignificant increase in 3-MH excretion in exercise of 37% and a significant increase (P less than 0.05) of 85% during 4 h of recovery from exercise (0.079 +/- 0.008 vs. 0.147 +/- 0.0338 mumol.kg-1.min-1 for rest and recovery from exercise, respectively). Nonetheless, there was no effect of exercise on total nitrogen excretion. Muscle fractional synthetic rate was not different in the exercise vs. the control group at the end of exercise (0.0417 +/- 0.004 vs. 0.0477 +/- 0.010%/h for exercise vs. control), but there was a significant increase in fractional synthetic rate in the exercise group during the recovery period (0.0821 +/- 0.006 vs. 0.0654 +/- 0.012%/h for exercise vs. control, P less than 0.05). Thus we conclude that although aerobic exercise may stimulate muscle protein breakdown, this does not result in a significant depletion of muscle mass because muscle protein synthesis is stimulated in recovery.
Muscle biopsies of the vastus lateralis muscle taken before and after 18 weeks of resistance training were compared by preparing frozen cross sections for electron microscopy and using adjacent sections for fiber typing by myosin ATPase activity. Quantitative ultrastructural changes were observed in histochemically-identified muscle fiber types of twelve young women who underwent the training. The percentage of type IIB fibers decreased and IIA fibers increased. The cross-sectional area of all major fiber types increased with training. The absolute volume of myofibrils, intermyofibrillar space, and mitochondria increased with training for most major fiber types (type I, IIA and IIAB), but the relative volume percentages were not significantly changed because of corresponding fiber hypertrophy. Mean mitochondrial size for types I and IIA and myofibril size for types IIC and IIB increased significantly with training. The capillary number per fiber and density did not change with training. Activity levels were measured for selected glycolytic and oxidative enzymes. Cytochrome oxidase and hexokinase increased significantly with training, while creatine kinase, citrate synthase, phosphofructokinase, glyceraldehyde phosphate dehydrogenase and hydroxyacyl CoA dehydrogenase enzymes were not significantly altered. The results suggest that this type of high-repetition resistance training causes the intracellular components of all fiber types to increase proportionally with an increase in fiber size. In addition, the enzyme analysis indicates the muscle as a whole may increase its oxidative phosphorylation capacity in conjunction with the decreased percentage of type IIB fibers.
It has been shown that muscle protein synthetic rate (MPS) is elevated in humans by 50% at 4 hrs following a bout of heavy resistance training, and by 109% at 24 hrs following training. This study further examined the time course for elevated muscle protein synthesis by examining its rate at 36 hrs following a training session. Six healthy young men performed 12 sets of 6- to 12-RM elbow flexion exercises with one arm while the opposite arm served as a control. MPS was calculated from the in vivo rate of incorporation of L-[1,2-13C2] leucine into biceps brachii of both arms using the primed constant infusion technique over 11 hrs. At an average time of 36 hrs postexercise, MPS in the exercised arm had returned to within 14% of the control arm value, the difference being nonsignificant. It is concluded that following a bout of heavy resistance training, MPS increases rapidly, is more than double at 24 hrs, and thereafter declines rapidly so that at 36 hrs it has almost returned to baseline.
We investigated the effects of the nature of the flooding amino acid on the rate of incorporation of tracer leucine into human skeletal muscle sampled by biopsy. Twenty-three healthy young men (24.5 +/- 5. 0 yr, 76.2 +/- 8.3 kg) were studied in groups of four or five. First, the effects of flooding with phenylalanine, threonine, or arginine (all at 0.05 g/kg body wt) on the incorporation of tracer [13C]leucine were studied. Then the effects of flooding with labeled [13C]glycine [0.1 g/kg body wt, 20 atoms percent excess (APE)] and [13C]serine (0.05 g/kg body wt, 15 APE) on the incorporation of simultaneously infused [13C]leucine were investigated. When a large dose of phenylalanine or threonine was administered, incorporation of the tracer leucine was significantly increased (from 0.036 to 0. 067 %/h and 0.037 to 0.070 %/h, respectively; each P < 0.01). However, when arginine, glycine, or serine was administered as a flooding dose, no stimulation of tracer leucine incorporation could be observed. These results, together with those previously obtained, suggest that large doses of individual essential, but not nonessential, amino acids are able to stimulate incorporation of constantly infused tracer amino acids into human muscle protein.
The results of several recent studies indicate that bradykinin protects tissues against the deleterious effects of ischemia-reperfusion (I/R). However, other studies indicate that bradykinin can act as a proinflammatory agent, inducing P-selectin expression, the formation of chemotactic stimuli, and endothelial barrier disruption. In the present study, we used intravital microscopic techniques to examine the dose-dependent effects of bradykinin on leukocyte-endothelial cell interactions, the formation of platelet-leukocyte aggregates, and venular hemodynamics in rat mesentery in an attempt to explain these divergent findings. Superfusion of the mesentery with low concentrations of bradykinin (</=10(-7) M) increased venular erythrocyte velocity (V(RBC)) without increasing the number of adherent leukocytes, whereas higher concentrations (>/=10(-6) M) decreased V(RBC), increased the number of platelet-leukocyte aggregates, and induced leukocyte adhesion in single postcapillary venules. The formation of platelet-leukocyte aggregates and increased leukocyte adhesion induced by high-dose bradykinin were attenuated by administration of a B(2)-receptor (HOE-140) or a platelet-activating factor (PAF, WEB-2086) antagonist. Thus these adhesive interactions induced by high-dose bradykinin appear to be mediated by a mechanism that is dependent on B(2)-receptor activation and the formation of PAF or PAF-like lipids. The effects of bradykinin on venular V(RBC) and blood flow were also concentration dependent, with low doses producing nitric oxide-mediated vasodilation, whereas high doses decreased V(RBC) by a mechanism that is PAF independent.
Acute and long-term effects of resistance exercise combined with vascular occlusion on muscular function were investigated. Changes in integrated electromyogram with respect to time (iEMG), vascular resistive index, and plasma lactate concentration were measured in five men either during or after elbow flexion exercises with the proximal end of the arm occluded at 0-100 mmHg. The mean iEMG, postexercise hyperemia, and plasma lactate concentration were all elevated with the increase in occlusion pressure at a low-intensity exercise, whereas they were unchanged with the increase in occlusion pressure at high-intensity exercise. To investigate the long-term effects of low-intensity exercise with occlusion, older women (n = 24) were subjected to a 16-wk exercise training for elbow flexor muscles, in which low-intensity [ approximately 50-30% one repetition maximum (1 RM)] exercise with occlusion at approximately 110 mmHg (LIO), low-intensity exercise without occlusion (LI), and high- to medium-intensity ( approximately 80-50% 1 RM) exercise without occlusion (HI) were performed. Percent increases in both cross-sectional area and isokinetic strength of elbow flexor muscles after LIO were larger than those after LI (P < 0.05) and similar to those after HI. The results suggest that resistance exercise at an intensity even lower than 50% 1 RM is effective in inducing muscular hypertrophy and concomitant increase in strength when combined with vascular occlusion.
To evaluate the importance of protein digestion rate on protein deposition, we characterized leucine kinetics after ingestion of "protein" meals of identical amino acid composition and nitrogen contents but of different digestion rates. Four groups of five or six young men received an L-[1-13C]leucine infusion and one of the following 30-g protein meals: a single meal of slowly digested casein (CAS), a single meal of free amino acid mimicking casein composition (AA), a single meal of rapidly digested whey proteins (WP), or repeated meals of whey proteins (RPT-WP) mimicking slow digestion rate. Comparisons were made between "fast" (AA, WP) and "slow" (CAS, RPT-WP) meals of identical amino acid composition (AA vs. CAS, and WP vs. RPT-WP). The fast meals induced a strong, rapid, and transient increase of aminoacidemia, leucine flux, and oxidation. After slow meals, these parameters increased moderately but durably. Postprandial leucine balance over 7 h was higher after the slow than after the fast meals (CAS: 38 +/- 13 vs. AA: -12 +/- 11, P < 0.01; RPT-WP: 87 +/- 25 vs. WP: 6 +/- 19 micromol/kg, P < 0.05). Protein digestion rate is an independent factor modulating postprandial protein deposition.
The present study was designed to determine whether consumption of an oral essential amino acid-carbohydrate supplement (EAC) before exercise results in a greater anabolic response than supplementation after resistance exercise. Six healthy human subjects participated in two trials in random order, PRE (EAC consumed immediately before exercise), and POST (EAC consumed immediately after exercise). A primed, continuous infusion of L-[ring-(2)H(5)]phenylalanine, femoral arteriovenous catheterization, and muscle biopsies from the vastus lateralis were used to determine phenylalanine concentrations, enrichments, and net uptake across the leg. Blood and muscle phenylalanine concentrations were increased by approximately 130% after drink consumption in both trials. Amino acid delivery to the leg was increased during exercise and remained elevated for the 2 h after exercise in both trials. Delivery of amino acids (amino acid concentration times blood flow) was significantly greater in PRE than in POST during the exercise bout and in the 1st h after exercise (P < 0.05). Total net phenylalanine uptake across the leg was greater (P = 0.0002) during PRE (209 +/- 42 mg) than during POST (81 +/- 19). Phenylalanine disappearance rate, an indicator of muscle protein synthesis from blood amino acids, increased after EAC consumption in both trials. These results indicate that the response of net muscle protein synthesis to consumption of an EAC solution immediately before resistance exercise is greater than that when the solution is consumed after exercise, primarily because of an increase in muscle protein synthesis as a result of increased delivery of amino acids to the leg.
We used a previously developed compartmental model to assess the postprandial distribution and metabolism of dietary nitrogen (N) in the splanchnic and peripheral areas after the ingestion of a single mixed meal containing either (15)N-labeled milk or soy purified protein. Although the lower whole-body retention of dietary N from soy protein was measured experimentally, the splanchnic retention of dietary N was predicted by the model not to be affected by the protein source, and its incorporation into splanchnic proteins was predicted to reach approximately 35% of ingested N at 8 h after both meals. However, dietary N intestinal absorption and its appearance in splanchnic free amino acids were predicted to be more rapid from soy protein and were associated with a higher deamination, concomitant with a higher efficiency of incorporation of dietary N into proteins in the splanchnic bed. In contrast, soy protein was predicted to cause a reduction in peripheral dietary N uptake, as a consequence of both similar splanchnic retention and increased oxidation compared with milk protein. In addition, protein synthesis efficiency was reduced in the peripheral area after soy protein intake, leading to dietary N incorporation in peripheral proteins that fell from 26 to 19% of ingested N 8 h after milk and soy protein ingestion, respectively. Such a model thus enables a description of the processes involved in the differential metabolic utilization of dietary proteins and constitutes a valuable tool for further definition of the notion of protein quality during the period of protein gain.
The effects of resistance exercise combined with vascular occlusion on muscle function were investigated in highly trained athletes. Elite rugby players (n = 17) took part in an 8 week study of exercise training of the knee extensor muscles, in which low-intensity [about 50% of one repetition maximum] exercise combined with an occlusion pressure of about 200 mmHg (LIO, n = 6), low-intensity exercise without the occlusion (LI, n = 6), and no exercise training (untrained control, n = 5) were included. The exercise in the LI group was of the same intensity and amount as in the LIO group. The LIO group showed a significantly larger increase in isokinetic knee extension torque than that in the other two groups (P < 0.05) at all the velocities studied. On the other hand, no significant difference was seen between LI and the control group. In the LIO group, the cross-sectional area of knee extensors increased significantly (P < 0.01), suggesting that the increase in knee extension strength was mainly caused by muscle hypertrophy. The dynamic endurance of knee extensors estimated from the decreases in mechanical work production and peak force after 50 repeated concentric contractions was also improved after LIO, whereas no significant change was observed in the LI and control groups. The results indicated that low-intensity resistance exercise causes, in almost fully trained athletes, increases in muscle size, strength and endurance, when combined with vascular occlusion.
Background:
The progressive loss of skeletal muscle mass with aging is attributed to a disruption in the regulation of skeletal muscle protein turnover.
Objective:
We investigated the effects on whole-body protein balance and mixed-muscle protein synthesis rates of the ingestion of carbohydrate with or without protein and free leucine after simulated activities of daily living.
Design:
Eight elderly (75 +/- 1 y) and 8 young (20 +/- 1 y) lean men were randomly assigned to 2 crossover experiments in which they consumed either carbohydrate (CHO) or carbohydrate plus protein and free leucine (CHO+Pro+Leu) after performing 30 min of standardized activities of daily living. Primed, continuous infusions with L-[ring-13C6]phenylalanine and L-[ring-2H2]tyrosine were applied, and blood and muscle samples were collected to assess whole-body protein turnover and the protein fractional synthetic rate in the vastus lateralis muscle over a 6-h period.
Results:
Whole-body phenylalanine and tyrosine flux were significantly higher in the young than in the elderly men (P < 0.01). Protein balance was negative in the CHO experiment but positive in the CHO+Pro+Leu experiment in both groups. Mixed-muscle protein synthesis rates were significantly greater in the CHO+Pro+Leu than in the CHO experiment in both the young (0.082 +/- 0.005%/h and 0.060 +/- 0.005%/h, respectively; P < 0.01) and the elderly (0.072 +/- 0.006%/h and 0.043 +/- 0.003%/h, respectively; P < 0.01) subjects, with no significant differences between groups.
Conclusions:
Co-ingestion of protein and leucine with carbohydrate after activities of daily living improves whole-body protein balance, and the increase in muscle protein synthesis rates is not significantly different between lean young and elderly men.
Resistance exercise is fundamentally anabolic and as such stimulates the process of skeletal muscle protein synthesis (MPS) in an absolute sense and relative to skeletal muscle protein breakdown (MPB). However, the net effect of resistance exercise is to shift net protein balance (NPB = MPS - MPB) to a more positive value; however, in the absence of feeding NPB remains negative. Feeding stimulates MPS to an extent where NPB becomes positive, for a transient time. When combined, resistance exercise and feeding synergistically interact to result in NPB being greater than with feeding alone. This feeding- and exercise-induced stimulation of NPB is what, albeit slowly, results in muscle hypertrophy. With this rudimentary knowledge we are now at the point where we can manipulate variables within the system to see what impact these interventions have on the processes of MPS, MPB, and NPB and ultimately and perhaps most importantly, muscle hypertrophy and strength. We used established models of skeletal muscle amino acid turnover to examine how protein source (milk versus soy) acutely affects the processes of MPS and MPB after resistance exercise. Our findings revealed that even when balanced quantities of total protein and energy are consumed that milk proteins are more effective in stimulating amino acid uptake and net protein deposition in skeletal muscle after resistance exercise than are hydrolyzed soy proteins. Importantly, the finding of increased amino acid uptake would be independent of the differences in amino acid composition of the two proteins. We propose that the improved net protein deposition with milk protein consumption is also not due to differences in amino acid composition, but is due to a different pattern of amino acid delivery associated with milk versus hydrolyzed soy proteins. If our acute findings are accurate then we hypothesized that chronically the greater net protein deposition associated with milk protein consumption post-resistance exercise would eventually lead to greater net protein accretion (i.e., muscle fiber hypertrophy), over a longer time period. In young men completing 12 weeks of resistance training (5d/wk) we observed a tendency (P = 0.11) for greater gains in whole body lean mass and whole as greater muscle fiber hypertrophy with consumption of milk. While strength gains were not different between the soy and milk-supplemented groups we would argue that the true significance of a greater increase in lean mass that we observed with milk consumption may be more important in groups of persons with lower initial lean mass and strength such as the elderly.
Muscle mass declines with aging. Amino acids alone stimulate muscle protein synthesis in the elderly. However, mixed nutritional supplementation failed to improve muscle mass. We hypothesized that the failure of nutritional supplements is due to altered responsiveness of muscle protein anabolism to increased amino acid availability associated with endogenous hyperinsulinemia. We measured muscle protein synthesis and breakdown, and amino acid transport in healthy young (30 +/- 3 yr) and elderly (72 +/- 1 yr) volunteers in the basal postabsorptive state and during the administration of an amino acid-glucose mixture, using L-[ring-(2)H(5)]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Basal muscle amino acid turnover was similar in young and elderly subjects. The mixture increased phenylalanine leg delivery and transport into the muscle in both groups. Phenylalanine net balance increased in both groups (young, -27 +/- 8 to 64 +/- 17; elderly, -16 +/- 4 to 29 +/- 7 nmol/(min.100 mL); P: < 0.0001, basal vs. mixture), but the increase was significantly blunted in the elderly (P: = 0.030 vs. young). Muscle protein synthesis increased in the young, but remained unchanged in the elderly [young, 61 +/- 17 to 133 +/- 30 (P: = 0. 005); elderly, 62 +/- 9 to 70 +/- 14 nmol/(min.100 mL) (P: = NS)]. In both groups, protein breakdown decreased (P: = 0.012) and leg glucose uptake increased (P: = 0.0258) with the mixture. We conclude that the response of muscle protein anabolism to hyperaminoacidemia with endogenous hyperinsulinemia is impaired in healthy elderly due to the unresponsiveness of protein synthesis.
J Physiol 2001 August 15: 535(1): 301–11(1) Age-associated loss of skeletal muscle mass and strength can partly be counteracted by resistance training, causing a net synthesis of muscular proteins. Protein synthesis is influenced synergistically by post-exercise amino acid supplementation, but the importance of the timing of protein intake remains unresolved. (2) The study investigated the importance of immediate (P0) or delayed (P2) intake of an oral protein supplement upon muscle hypertrophy and strength over a period of resistance training in elderly males. (3) Thirteen men (age 74 ± 1 years; body mass index (BMI), 25 ± 1 kg m- 2 (means ± SEM)) completed a 12-week resistance training program (three times per week) receiving oral protein in liquid form (10 g protein, 7 g carbohydrate, 3 g fat) immediately after (P0) or 2 h after (P2) each training session. Muscle hypertrophy was evaluated by magnetic resonance imaging (MRI) and from muscle biopsies and muscle strength was determined using dynamic and isokinetic strength measurements. Body composition was determined from dual-energy X-ray absorptiometry (DEXA) and food records were obtained over 4 days. The plasma insulin response to protein supplementation was also determined. (4) In response to training, the cross-sectional area of m. quadriceps femoris (54.6 ± 0.5–58.3 ± 0.5 cm2) and mean fiber area (4047 ± 320–5019 ± 615 μ m2) increased in the P0 group, whereas no significant increase was observed in P2. For P0 both dynamic and isokinetic strength increased, by 46 and 15%, respectively (P P
In 1969, Pozefsky et al. ([8][1]) reported on the effects of systemic insulin infusion on forearm amino acid and glucose uptake. They noted that a large increase in insulin from 12 to 157 μU/ml resulted in a significant lowering of forearm (muscle) “…alpha amino nitrogen release by 74%…
The present study was performed to test the hypothesis that orally administered essential amino acids, in combination with carbohydrate, will stimulate net muscle protein synthesis in resting human muscle in vivo. Four volunteers ingested 500 mL of a solution containing 13.4 g of essential amino acids and 35 g sucrose (EAA). Blood samples were taken from femoral arterial and venous catheters over a 2-hour period following the ingestion of EAA to measure arteriovenous concentrations of amino acids across the muscle. Two muscle biopsies were taken during the study, one before administration of the drink and one approximately 2 hours after consumption of EAA. Serum insulin increased from normal physiologic levels at baseline (9.2 +/- 0.8 microU/mL) and peaked (48 +/- 7.1 microU/mL) 30 minutes after EAA ingestion. Arterial essential amino acid concentrations increased approximately 100 to 400% above basal levels between 10 and 30 minutes following drink ingestion. Net nitrogen (N) balance changed from negative (-495 +/- 128 nmol/mL) prior to consumption of EAA to a peak positive value (416 +/- 140 nmol/mL) within 10 minutes of ingestion of the drink. EAA resulted in an estimated positive net N uptake of 307.3 mg N above basal levels over the 2-hour period. Muscle amino acid concentrations were similar prior to and 2 hours following ingestion of EAA. We conclude that ingestion of a solution composed of carbohydrates to stimulate insulin release and a small amount of essential amino acids to increase amino acid availability for protein synthesis is an effective stimulator of muscle protein anabolism.
A fatty meal induces vasodilatation (of both resting and stimulated forearm flow) in healthy young adults, an effect most likely mediated by the vasodilator actions of insulin. We therefore hypothesized that an impaired meal-related vascular response might be an in vivo marker of vascular insulin resistance, related to the presence of diabetes and/or higher age. Postprandial vascular responses were assessed in three groups of subjects: 15 Type 2 diabetic subjects (age 58 +/- 8 yr), 15 age-, gender-, and body mass index (BMI)-matched older control subjects (age 57 +/- 9 yr), and 15 healthy young control subjects (age 33 +/- 7 yr). Studies were carried out before and 3 and 6 h after a standardized high-fat meal (1,030 kcal, 61 g fat). Forearm microvascular flows were measured by strain gauge plethysmography and large-artery function by ultrasound. Resting blood flow and hyperemic area under curve (AUC) flow were not significantly different in diabetic subjects (resting 117 +/- 42% and AUC 134 +/- 46% of premeal values) compared with age-matched controls (resting 131 +/- 39% and AUC 134 +/- 47%); however, the response in diabetic subjects was blunted compared with young controls (resting 171 +/- 67% and AUC 173 +/- 99% of premeal values; P = 0.02 and P = 0.18, respectively). On multiple regression analysis, we found that increasing age (but not BMI or diabetes) was significantly associated with impaired postprandial vascular responses (resting: r = -0.4, P = 0.002; AUC: r = -0.4, P = 0.006). Therefore, meal ingestion results in impaired vasodilator responses in older nondiabetic and diabetic adults, related to aging rather than insulin resistance.
The anabolic effect of resistance exercise is enhanced by the provision of dietary protein.
We aimed to determine the ingested protein dose response of muscle (MPS) and albumin protein synthesis (APS) after resistance exercise. In addition, we measured the phosphorylation of candidate signaling proteins thought to regulate acute changes in MPS.
Six healthy young men reported to the laboratory on 5 separate occasions to perform an intense bout of leg-based resistance exercise. After exercise, participants consumed, in a randomized order, drinks containing 0, 5, 10, 20, or 40 g whole egg protein. Protein synthesis and whole-body leucine oxidation were measured over 4 h after exercise by a primed constant infusion of [1-(13)C]leucine.
MPS displayed a dose response to dietary protein ingestion and was maximally stimulated at 20 g. The phosphorylation of ribosomal protein S6 kinase (Thr(389)), ribosomal protein S6 (Ser(240/244)), and the epsilon-subunit of eukaryotic initiation factor 2B (Ser(539)) were unaffected by protein ingestion. APS increased in a dose-dependent manner and also reached a plateau at 20 g ingested protein. Leucine oxidation was significantly increased after 20 and 40 g protein were ingested.
Ingestion of 20 g intact protein is sufficient to maximally stimulate MPS and APS after resistance exercise. Phosphorylation of candidate signaling proteins was not enhanced with any dose of protein ingested, which suggested that the stimulation of MPS after resistance exercise may be related to amino acid availability. Finally, dietary protein consumed after exercise in excess of the rate at which it can be incorporated into tissue protein stimulates irreversible oxidation.
We investigated how myofibrillar protein synthesis (MPS) and muscle anabolic signalling were affected by resistance exercise at 20-90% of 1 repetition maximum (1 RM) in two groups (25 each) of post-absorptive, healthy, young (24 +/- 6 years) and old (70 +/- 5 years) men with identical body mass indices (24 +/- 2 kg m(-2)). We hypothesized that, in response to exercise, anabolic signalling molecule phosphorylation and MPS would be modified in a dose-dependant fashion, but to a lesser extent in older men. Vastus lateralis muscle was sampled before, immediately after, and 1, 2 and 4 h post-exercise. MPS was measured by incorporation of [1,2-(13)C] leucine (gas chromatography-combustion-mass spectrometry using plasma [1,2-(13)C]alpha-ketoisocaparoate as surrogate precursor); the phosphorylation of p70 ribosomal S6 kinase (p70s6K) and eukaryotic initiation factor 4E binding protein 1 (4EBP1) was measured using Western analysis with anti-phosphoantibodies. In each group, there was a sigmoidal dose-response relationship between MPS at 1-2 h post-exercise and exercise intensity, which was blunted (P < 0.05) in the older men. At all intensities, MPS fell in both groups to near-basal values by 2-4 h post-exercise. The phosphorylation of p70s6K and 4EBP1 at 60-90% 1 RM was blunted in older men. At 1 h post-exercise at 60-90% 1 RM, p70s6K phosphorylation predicted the rate of MPS at 1-2 h post-exercise in the young but not in the old. The results suggest that in the post-absorptive state: (i) MPS is dose dependant on intensity rising to a plateau at 60-90% 1 RM; (ii) older men show anabolic resistance of signalling and MPS to resistance exercise.
Muscle mass accretion is accomplished by heavy-load resistance training. The effect of light-load resistance exercise has been far more sparsely investigated with regard to potential effect on muscle size and contractile strength. We applied a resistance exercise protocol in which the same individual trained one leg at 70% of one-repetition maximum (1RM) (heavy load, HL) while training the other leg at 15.5% 1RM (light load, LL). Eleven sedentary men (age 25 +/- 1 yr) trained for 12 wk at three times/week. Before and after the intervention muscle hypertrophy was determined by magnetic resonance imaging, muscle biopsies were obtained bilaterally from vastus lateralis for determination of myosin heavy chain (MHC) composition, and maximal muscle strength was assessed by 1RM testing and in an isokinetic dynamometer at 60 degrees /s. Quadriceps muscle cross-sectional area increased (P < 0.05) 8 +/- 1% and 3 +/- 1% in HL and LL legs, respectively, with a greater gain in HL than LL (P < 0.05). Likewise, 1RM strength increased (P < 0.001) in both legs (HL: 36 +/- 5%, LL: 19 +/- 2%), albeit more so with HL (P < 0.01). Isokinetic 60 degrees /s muscle strength improved by 13 +/- 5% (P < 0.05) in HL but remained unchanged in LL (4 +/- 5%, not significant). Finally, MHC IIX protein expression was decreased with HL but not LL, despite identical total workload in HL and LL. Our main finding was that LL resistance training was sufficient to induce a small but significant muscle hypertrophy in healthy young men. However, LL resistance training was inferior to HL training in evoking adaptive changes in muscle size and contractile strength and was insufficient to induce changes in MHC composition.
Twenty-four women completed a 20-week heavy-resistance weight training program for the lower extremity. Workouts were twice a week and consisted of warm-up exercises followed by three sets each of full squats, vertical leg presses, leg extensions, and leg curls. All exercises were performed to failure using 6-8 RM (repetition maximum). Weight training caused a significant increase in maximal isotonic strength (1 RM) for each exercise. After training, there was a decrease in body fat percentage (p less than 0.05), and an increase in lean body mass (p less than 0.05) with no overall change in thigh girth. Biopsies were obtained before and after training from the superficial portion of the vastus lateralis muscle. Sections were prepared for histological and histochemical examination. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were distinguished following routine myofibrillar adenosine triphosphatase histochemistry. Areas were determined for fiber types I, IIA, and IIAB + IIB. The heavy-resistance training resulted in significant hypertrophy of all three groups: I (15%), IIA (45%), and IIAB + IIB (57%). These data are similar to those in men and suggest considerable hypertrophy of all major fiber types is also possible in women if exercise intensity and duration are sufficient. In addition, the training resulted in a significant decrease in the percentage of IIB with a concomitant increase in IIA fibers, suggesting that strength training may lead to fiber conversions.
1. Groups of male hamsters of different ages were subjected to a weight‐lifting exercise regimen, and the biceps brachii, soleus and extensor digitorum longus (EDL) muscles examined for structural changes occurring in response to the increased workload. In addition, two groups of adult hamsters were left to recover from the exercise stimulus for 5 and 15 weeks respectively.
2. All the exercised muscles exhibited muscle fibre hypertrophy, and the extent of the hypertrophy was greater in the younger animals. In all age groups, the biceps brachii and EDL showed more hypertrophy than did the soleus. There was no significant increase in fibre number after exercise.
3. In both groups allowed to recover from the exercise stimulus, the fibre dimensions reverted back to those of the control muscles; this appeared to be complete after 15 weeks recovery.
4. Electron microscopical studies of fibres from exercised and control biceps brachii revealed no significant changes with exercise in the proportions present of myofibrillar, mitochondrial and tubular components within muscle fibres of the same size.
The rates of protein synthesis and degradation and of amino acid transport were determined in the leg muscle of untrained postabsorptive normal volunteers at rest and approximately 3 h after a resistance exercise routine. The methodology involved use of stable isotopic tracers of amino acids, arteriovenous catheterization of the femoral vessels, and biopsy of the vastus lateralis muscle. During postexercise recovery, the rate of intramuscular phenylalanine utilization for protein synthesis increased above the basal value by 108 +/- 18%, whereas the rate of release from proteolysis increased by 51 +/- 17%. Muscle protein balance improved (P < 0.05) after exercise but did not become positive (from -15 +/- 12 to -6 +/- 3 nmol phenylalanine.min-1.100 ml leg volume-1). After exercise, rates of inward transport of leucine, lysine, and alanine increased (P < 0.05) above the basal state from 132 +/- 16 to 208 +/- 29, from 122 +/- 8 to 260 +/- 8, and from 384 +/- 71 to 602 +/- 89 nmol.min-1.100 ml leg-1, respectively. Transport of phenylalanine did not change significantly. These results indicate that, during recovery after resistance exercise, muscle protein turnover is increased because of an acceleration of synthesis and degradation. A postexercise acceleration of amino acid transport may contribute to the relatively greater stimulation of protein synthesis.
The current Canadian Recommended Nutrient Intake (RNI) for protein (0.86 g.kg-1.day-1) makes no allowance for an effect of habitual physical activity. In addition, Tarnopolsky et al. (J. Appl. Physiol. 68: 302-308, 1990) showed that males may catabolize more protein than females consequent to endurance exercise. We examined nitrogen (N) balance and leucine kinetics during submaximal endurance exercise to determine the adequacy of the current Canadian RNI for protein for male and female endurance athletes. Athletes were matched for equal training volume, competitive status, and conditioning and were fed diets isoenergetic with their habitual intake, containing protein at the Canadian RNI. Subjects were adapted to the diet for 10 days before completing a 3-day measurement of N balance. N balance showed that the RNI was inadequate for females (-15.9 +/- 6.0 mg.kg-1.day-1) and males (-26.3 +/- 11.0 mg.kg-1.day-1). Leucine kinetics during exercise were determined for each subject on day 3 of the N balance experiment by use of a primed continuous infusion of L-[1-13C]leucine and the reciprocal pool model. Exercise resulted in a significant (P < 0.01) increase in leucine oxidation for both groups. Males oxidized a greater amount of leucine during the infusion than females (P < 0.01). Leucine flux also increased significantly (P < 0.01) during exercise in both groups. We conclude that the current Canadian RNI for protein is inadequate for those who chronically engage in endurance exercise.(ABSTRACT TRUNCATED AT 250 WORDS)
There is little known about the responses of muscle protein metabolism in women to exercise. Furthermore, the effect of adding resistance training to an endurance training regimen on net protein anabolism has not been established in either men or women. The purpose of this study was to quantify the acute effects of combined swimming and resistance training on protein metabolism in female swimmers by the direct measurement of muscle protein synthesis and whole body protein degradation. Seven collegiate female swimmers were each studied on four separate occasions with a primed constant infusion of ring-[13C6]phenylalanine (Phe) to measure the fractional synthetic rate (FSR) of the posterior deltoid and whole body protein breakdown. Measurements were made over a 5-h period at rest and after each of three randomly ordered workouts: 1) 4,600 m of intense interval swimming (SW); 2) a whole body resistance-training workout with no swimming on that day (RW); and 3) swimming and resistance training combined (SR). Whole body protein breakdown was similar for all treatments (0.75 +/- 0.04, 0.69 +/- 0.03, 0.69 +/- 0.02, and 0.71 +/- 0.04 mumol.min-1.kg-1 for rest, RW, SW, and SR, respectively). The FSR of the posterior deltoid was significantly greater (P < 0.05) after SR (0.082 +/- 0.015%/h) than at rest (0.045 +/- 0.006%/h). There was no significant difference in the FSR after RW (0.048 +/- 0.004%/h) or SW (0.064 +/- 0.008%/h) from rest or from SR. These data indicate that the combination of swimming and resistance exercise stimulates net muscle protein synthesis above resting levels in female swimmers.
Six normal untrained men were studied during the intravenous infusion of a balanced amino acid mixture (approximately 0.15 g.kg-1.h-1 for 3 h) at rest and after a leg resistance exercise routine to test the influence of exercise on the regulation of muscle protein kinetics by hyperaminoacidemia. Leg muscle protein kinetics and transport of selected amino acids (alanine, phenylalanine, leucine, and lysine) were isotopically determined using a model based on arteriovenous blood samples and muscle biopsy. The intravenous amino acid infusion resulted in comparable increases in arterial amino acid concentrations at rest and after exercise, whereas leg blood flow was 64 +/- 5% greater after exercise than at rest. During hyperaminoacidemia, the increases in amino acid transport above basal were 30-100% greater after exercise than at rest. Increases in muscle protein synthesis were also greater after exercise than at rest (291 +/- 42% vs. 141 +/- 45%). Muscle protein breakdown was not significantly affected by hyperminoacidemia either at rest or after exercise. We conclude that the stimulatory effect of exogenous amino acids on muscle protein synthesis is enhanced by prior exercise, perhaps in part because of enhanced blood flow. Our results imply that protein intake immediately after exercise may be more anabolic than when ingested at some later time.
Mixed muscle protein fractional synthesis rate (FSR) and fractional breakdown rate (FBR) were examined after an isolated bout of either concentric or eccentric resistance exercise. Subjects were eight untrained volunteers (4 males, 4 females). Mixed muscle protein FSR and FBR were determined using primed constant infusions of [2H5]phenylalanine and 15N-phenylalanine, respectively. Subjects were studied in the fasted state on four occasions: at rest and 3, 24, and 48 h after a resistance exercise bout. Exercise was eight sets of eight concentric or eccentric repetitions at 80% of each subject's concentric 1 repetition maximum. There was no significant difference between contraction types for either FSR, FBR, or net balance (FSR minus FBR). Exercise resulted in significant increases above rest in muscle FSR at all times: 3 h = 112%, 24 h = 65%, 48 h = 34% (P < 0.01). Muscle FBR was also increased by exercise at 3 h (31%; P < 0.05) and 24 h (18%; P < 0.05) postexercise but returned to resting levels by 48 h. Muscle net balance was significantly increased after exercise at all time points [(in %/h) rest = -0.0573 +/- 0.003 (SE), 3 h = -0.0298 +/- 0.003, 24 h = -0.0413 +/- 0.004, and 48 h = -0.0440 +/- 0.005], and was significantly different from zero at all time points (P < 0.05). There was also a significant correlation between FSR and FBR (r = 0.88, P < 0.001). We conclude that exercise resulted in an increase in muscle net protein balance that persisted for up to 48 h after the exercise bout and was unrelated to the type of muscle contraction performed.
We examined the effect of resistance training on the response of mixed muscle protein fractional synthesis (FSR) and breakdown rates (FBR) by use of primed constant infusions of [2H5]phenylalanine and [15N]phenylalanine, respectively, to an isolated bout of pleiometric resistance exercise. Trained subjects, who were performing regular resistance exercise (trained, T; n = 6), were compared with sedentary, untrained controls (untrained, UT; n = 6). The exercise test consisted of 10 sets (8 repetitions per set) of single-leg knee flexion (i.e., pleiometric muscle contraction during lowering) at 120% of the subjects' predetermined single-leg 1 repetition maximum. Subjects exercised one leg while their contralateral leg acted as a nonexercised (resting) control. Exercise resulted in an increase, above resting, in mixed muscle FSR in both groups (UT: rest, 0.036 +/- 0.002; exercise, 0.0802 +/- 0.01; T: rest, 0.045 +/- 0.004; exercise, 0.067 +/- 0.01; all values in %/h; P < 0.01). In addition, exercise resulted in an increase in mixed muscle FBR of 37 +/- 5% (rest, 0.076 +/- 0.005; exercise, 0.105 +/- 0.01; all values in %/h; P < 0.01) in the UT group but did not significantly affect FBR in the T group. The resulting muscle net balance (FSR - FBR) was negative throughout the protocol (P < 0.05) but was increased in the exercised leg in both groups (P < 0.05). We conclude that pleiometric muscle contractions induce an increase in mixed muscle protein synthetic rate within 4 h of completion of an exercise bout but that resistance training attenuates this increase. A single bout of pleiometric muscle contractions also increased the FBR of mixed muscle protein in UT but not in T subjects.
Resistance exercises stimulate protein synthesis in human muscle, but the roles of changes in mRNA concentrations and changes in the efficiency of mRNA translation have not been defined. The present study was done to determine whether resistance exercise affects concentrations of total RNA, total mRNA, actin mRNA, or myosin heavy-chain mRNA (total and isoform specific). Eight subjects, 62-75 yr old, performed unilateral knee extensions at 80% of their one-repetition-maximum capacity on days 1, 3, and 6 of the study. On day 7, biopsies of exercised and nonexercised vastus lateralis muscles were obtained. Myofibrillar synthesis was determined by stable- isotope incorporation, and mRNA concentrations were determined by membrane hybridization and PCR-based methods. The exercise stimulated myofibrillar synthesis [30 +/- 6 (SE)%] without affecting RNA or mRNA concentrations. The effect of exercise on protein synthesis in individual subjects did not correlate with the effect on total RNA and mRNA concentrations. These data suggest that the stimulation of myofibrillar synthesis by resistance exercise is mediated by more efficient translation of mRNA.
We examined the response of net muscle protein synthesis to ingestion of amino acids after a bout of resistance exercise. A primed, constant infusion of L-[ring-2H5]phenylalanine was used to measure net muscle protein balance in three male and three female volunteers on three occasions. Subjects consumed in random order 1 liter of 1) a mixed amino acid (40 g) solution (MAA), 2) an essential amino acid (40 g) solution (EAA), and 3) a placebo solution (PLA). Arterial amino acid concentrations increased approximately 150-640% above baseline during ingestion of MAA and EAA. Net muscle protein balance was significantly increased from negative during PLA ingestion (-50 +/- 23 nmol. min-1. 100 ml leg volume-1) to positive during MAA ingestion (17 +/- 13 nmol. min-1. 100 ml leg volume-1) and EAA (29 +/- 14 nmol. min-1. 100 ml leg volume-1; P < 0.05). Because net balance was similar for MAA and EAA, it does not appear necessary to include nonessential amino acids in a formulation designed to elicit an anabolic response from muscle after exercise. We concluded that ingestion of oral essential amino acids results in a change from net muscle protein degradation to net muscle protein synthesis after heavy resistance exercise in humans similar to that seen when the amino acids were infused.
We have determined the individual and combined effects of insulin and prior exercise on leg muscle protein synthesis and degradation, amino acid transport, glucose uptake, and alanine metabolism. Normal volunteers were studied in the postabsorptive state at rest and about 3 h after a heavy leg resistance exercise routine. The leg arteriovenous balance technique was used in combination with stable isotopic tracers of amino acids and biopsies of the vastus lateralis muscle. Insulin was infused into a femoral artery to increase the leg insulin concentrations to high physiologic levels without substantively affecting the whole-body level. Protein synthesis and degradation were determined as rates of intramuscular phenylalanine utilization and appearance, and muscle fractional synthetic rate (FSR) was also determined. Leg blood flow was greater after exercise than at rest (P<0.05). Insulin accelerated blood flow at rest but not after exercise (P<0.05). The rates of protein synthesis and degradation were greater during the postexercise recovery (65+/-10 and 74+/-10 nmol x min(-1) x 100 ml(-1) leg volume, respectively) than at rest (30+/-7 and 46+/-8 nmol x min(-1) x 100 ml(-1) leg volume, respectively; P<0.05). Insulin infusion increased protein synthesis at rest (51+/-4 nmol x min(-1) x 100 ml(-1) leg volume) but not during the postexercise recovery (64+/-9 nmol x min(-1) x 100 ml(-1) leg volume; P<0.05). Insulin infusion at rest did not change the rate of protein degradation (48+/-3 nmol x min(-1) 100 ml(-1) leg volume). In contrast, insulin infusion after exercise significantly decreased the rate of protein degradation (52+/-9 nmol x min(-1) x 100 ml(-1) leg volume). The insulin stimulatory effects on inward alanine transport and glucose uptake were three times greater during the postexercise recovery than at rest (P<0.05). In contrast, the insulin effects on phenylalanine, leucine, and lysine transport were similar at rest and after exercise. In conclusion, the ability of insulin to stimulate glucose uptake and alanine transport and to suppress protein degradation in skeletal muscle is increased after resistance exercise. Decreased amino acid availability may limit the stimulatory effect of insulin on muscle protein synthesis after exercise.
Components of signaling pathways for mechanotransduction during load-induced enlargement of skeletal muscle have not been completely defined. We hypothesized that loading of skeletal muscle would result in an adaptive increase in the expression of two focal adhesion complex (FAC)-related proteins, focal adhesion kinase (FAK) and paxillin, as well as increased FAK activity. FAK protein was immunolocalized to the sarcolemmal region of rooster anterior latissimus dorsi (ALD) myofibers in the middle of the ALD muscle. FAK (77 and 81%) and paxillin (206 and 202%) protein concentrations per unit of total protein in Western blots increased significantly after 1.5 and 7 days, but not after 13 days, of stretch-induced hypertrophy-hyperplasia of the ALD muscle. FAK autokinase activity in immunoprecipitates was increased after 1.5, 7, and 13 days in stretched ALD muscles. To determine whether increased FAK and paxillin protein concentrations are associated with hypertrophy and/or new fiber formation, two additional experiments were performed. First, during formation of primary chicken myotubes (a model of new fiber formation), FAK protein concentration (63%), FAK activity (157%), and paxillin protein concentration (97%) increased compared with myoblasts. Second, FAK (112% and 611%) and paxillin (87% and 431%) protein concentrations per unit of total protein in the soleus muscle increased at 1 and 8 days after surgical ablation of the synergistic gastrocnemius muscle (a model of hypertrophy without hyperplasia). Thus increases in components of the FAC occur in hypertrophying muscle of animals and in newly formed muscle fibers in culture. Furthermore, increased FAK activity suggests a possible convergence of signaling at the FAC in load-induced growth of skeletal muscle.
The purpose of this study was to investigate the time course of skeletal muscle adaptations resulting from high-intensity, upper and lower body dynamic resistance training (WT). A group of 17 men and 20 women were recruited for WT, and 6 men and 7 women served as a control group. The WT group performed six dynamic resistance exercises to fatigue using 8-12 repetition maximum (RM). The subjects trained 3 days a week for 12 weeks. One-RM knee extension (KE) and chest press (CP) exercises were measured at baseline and at weeks 2, 4, 6, 8, and 12 for the WT group. Muscle thickness (MTH) was measured by ultrasound at eight anatomical sites. One-RM CP and KE strength had increased significantly at week 4 for the female WT group. For the men in the WT group, 1 RM had increased significantly at week 2 for KE and at week 6 for CP. The mean relative increases in KE and CP strength were 19% and 19% for the men and 19% and 27% for the women, respectively, after 12 weeks of WT. Resistance training elicited a significant increase in MTH of the chest and triceps muscles at week 6 in both sexes. There were non-significant trends for increases in quadriceps MTH for the WT groups. The relative increases in upper and lower body MTH were 12%-21% and 7%-9% in the men and 10%-31% and 7%-8% in the women respectively, after 12 weeks of WT. These results would suggest that increases in MTH in the upper body are greater and occur earlier compared to the lower extremity, during the first 12 weeks of a total body WT programme. The time-course and proportions of the increase in strength and MTH were similar for both the men and the women.
This study was designed to determine the response of muscle protein to the bolus ingestion of a drink containing essential amino acids and carbohydrate after resistance exercise. Six subjects (3 men, 3 women) randomly consumed a treatment drink (6 g essential amino acids, 35 g sucrose) or a flavored placebo drink 1 h or 3 h after a bout of resistance exercise on two separate occasions. We used a three-compartment model for determination of leg muscle protein kinetics. The model involves the infusion of ring-(2)H(5)-phenylalanine, femoral arterial and venous blood sampling, and muscle biopsies. Phenylalanine net balance and muscle protein synthesis were significantly increased above the predrink and corresponding placebo value (P < 0.05) when the drink was taken 1 or 3 h after exercise but not when the placebo was ingested at 1 or 3 h. The response to the amino acid-carbohydrate drink produced similar anabolic responses at 1 and 3 h. Muscle protein breakdown did not change in response to the drink. We conclude that essential amino acids with carbohydrates stimulate muscle protein anabolism by increasing muscle protein synthesis when ingested 1 or 3 h after resistance exercise.
Muscle mass declines with aging. Amino acids alone stimulate muscle protein synthesis in the elderly. However, mixed nutritional supplementation failed to improve muscle mass. We hypothesized that the failure of nutritional supplements is due to altered responsiveness of muscle protein anabolism to increased amino acid availability associated with endogenous hyperinsulinemia. We measured muscle protein synthesis and breakdown, and amino acid transport in healthy young (30 +/- 3 yr) and elderly (72 +/- 1 yr) volunteers in the basal postabsorptive state and during the administration of an amino acid-glucose mixture, using L-[ring-(2)H(5)]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Basal muscle amino acid turnover was similar in young and elderly subjects. The mixture increased phenylalanine leg delivery and transport into the muscle in both groups. Phenylalanine net balance increased in both groups (young, -27 +/- 8 to 64 +/- 17; elderly, -16 +/- 4 to 29 +/- 7 nmol/(min.100 mL); P: < 0.0001, basal vs. mixture), but the increase was significantly blunted in the elderly (P: = 0.030 vs. young). Muscle protein synthesis increased in the young, but remained unchanged in the elderly [young, 61 +/- 17 to 133 +/- 30 (P: = 0. 005); elderly, 62 +/- 9 to 70 +/- 14 nmol/(min.100 mL) (P: = NS)]. In both groups, protein breakdown decreased (P: = 0.012) and leg glucose uptake increased (P: = 0.0258) with the mixture. We conclude that the response of muscle protein anabolism to hyperaminoacidemia with endogenous hyperinsulinemia is impaired in healthy elderly due to the unresponsiveness of protein synthesis.
This investigation examined the effect of mechanical loading state on focal adhesion kinase (FAK), paxillin, and serum response factor (SRF) in rat skeletal muscle. We found that FAK concentration and tyrosine phosphorylation, paxillin concentration, and SRF concentration are all lower in the lesser load-bearing fast-twitch plantaris and gastrocnemius muscles compared with the greater load-bearing slow-twitch soleus muscle. Of these three muscles, 7 days of mechanical unloading via tail suspension elicited a decrease in FAK tyrosine phosphorylation only in the soleus muscle and decreases in FAK and paxillin concentrations only in the plantaris and gastrocnemius muscles. Unloading decreased SRF concentration in all three muscles. Mechanical overloading (via bilateral gastrocnemius ablation) for 1 or 8 days increased FAK and paxillin concentrations in the soleus and plantaris muscles. Additionally, whereas FAK tyrosine phosphorylation and SRF concentration were increased by < or =1 day of overloading in the soleus muscle, these increases did not occur until somewhere between 1 and 8 days of overloading in the plantaris muscle. These data indicate that, in the skeletal muscles of rats, the focal adhesion complex proteins FAK and paxillin and the transcription factor SRF are generally modulated in association with the mechanical loading state of the muscle. However, the somewhat different patterns of adaptation of these proteins to altered loading in slow- vs. fast-twitch skeletal muscles indicate that the mechanisms and time course of adaptation may partly depend on the prior loading state of the muscle.
Branched chain amino acids (BCAA) are particularly effective anabolic agents. Recent in vitro studies suggest that amino acids, particularly leucine, activate a signaling pathway that enhances messenger ribonucleic acid translation and protein synthesis. The physiological relevance of these findings to normal human physiology is uncertain. We examined the effects of BCAA on the phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (eIF4E-BP1) and ribosomal protein S6 kinase (p70S6K) in skeletal muscle of seven healthy volunteers. We simultaneously examined whether BCAA affect urinary nitrogen excretion and forearm skeletal muscle protein turnover and whether the catabolic action of glucocorticoids could be mediated in part by inhibition of the action of BCAA on the protein synthetic apparatus.
BCAA infusion decreased urinary nitrogen excretion (P < 0.02), whole body phenylalanine flux (P < 0.02), plasma phenylalanine concentration (P < 0.001), and improved forearm phenylalanine balance (P = 0.03). BCAA also increased the phosphorylation of both eIF4E-BP1 (P < 0.02) and p70S6K (P < 0.03), consistent with an action to activate the protein synthetic apparatus. Dexamethasone increased plasma phenylalanine concentration (P < 0.001), prevented the BCAA-induced anabolic shift in forearm protein balance, and inhibited their action on the phosphorylation of p70S6K. We conclude that in human skeletal muscle BCAA act directly as nutrient signals to activate messenger ribonucleic acid translation and potentiate protein synthesis. Glucocorticoids interfere with this action, and that may be part of the mechanism by which they promote net protein catabolism in muscle.
There is a controversy in the literature as to the effects of gender on leucine kinetics. Two research groups found that men oxidize more leucine during exercise, whereas another group showed no gender effects. The purpose of our study was to examine the effects of gender on leucine and, for comparison purposes, lysine kinetics. Our subjects (n = 14) were seven matched pairs of men and women selected for their exercise habits and age. After 1 wk of a standardized diet, they exercised at 50% of maximal O(2) uptake for 1 h. There was an effect of exercise in both genders: an increased leucine oxidation and an attenuation in nonoxidative leucine disposal compared with rest (P < 0.05). Furthermore, our study confirms that there are gender differences in leucine, but not lysine, kinetics. Men had a higher rate of leucine oxidation and a lower rate of nonoxidative leucine disposal during exercise (P < 0.05). For women, a larger proportion of their exercise energy needs came from fat; for men, a greater fraction came from carbohydrate (P < 0.05). We conclude that female exercisers rely to a greater extent on fat as an energy source, thereby using less carbohydrate, amino acid, and protein as a fuel source.
1. Age-associated loss of skeletal muscle mass and strength can partly be counteracted by resistance training, causing a net synthesis of muscular proteins. Protein synthesis is influenced synergistically by postexercise amino acid supplementation, but the importance of the timing of protein intake remains unresolved. 2. The study investigated the importance of immediate (P0) or delayed (P2) intake of an oral protein supplement upon muscle hypertrophy and strength over a period of resistance training in elderly males. 3. Thirteen men (age, 74 +/- 1 years; body mass index (BMI), 25 +/- 1 kg m(-2) (means +/- S.E.M.)) completed a 12 week resistance training programme (3 times per week) receiving oral protein in liquid form (10 g protein, 7 g carbohydrate, 3 g fat) immediately after (P0) or 2 h after (P2) each training session. Muscle hypertrophy was evaluated by magnetic resonance imaging (MRI) and from muscle biopsies and muscle strength was determined using dynamic and isokinetic strength measurements. Body composition was determined from dual-energy X-ray absorptiometry (DEXA) and food records were obtained over 4 days. The plasma insulin response to protein supplementation was also determined. 4. In response to training, the cross-sectional area of m. quadriceps femoris (54.6 +/- 0.5 to 58.3 +/- 0.5 cm(2)) and mean fibre area (4047 +/- 320 to 5019 +/- 615 microm(2)) increased in the P0 group, whereas no significant increase was observed in P2. For P0 both dynamic and isokinetic strength increased, by 46 and 15 %, respectively (P < 0.05), whereas P2 only improved in dynamic strength, by 36 % (P < 0.05). No differences in glucose or insulin response were observed between protein intake at 0 and 2 h postexercise. 5. We conclude that early intake of an oral protein supplement after resistance training is important for the development of hypertrophy in skeletal muscle of elderly men in response to resistance training.
The major anabolic influences on muscle are feeding and contractile activity. As a result of feeding, anabolism occurs chiefly by increases in protein synthesis with minor changes in protein breakdown. Insulin has a permissive role in increasing synthesis, but the availability of amino acids is crucial for net anabolism. We have investigated the role of amino acids in stimulating muscle protein synthesis, the synergy between exercise and amino acid availability, and some of the signaling elements involved. The results suggest that muscle is acutely sensitive to amino acids, that exercise probably increases the anabolic effects of amino acids by a separate pathway, and that for this reason it is unlikely that accustomed physical exercise increases protein requirements.