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# Effects of Carbohydrate Restriction on Strength Performance

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## Abstract

This study investigated the effect of a carbohydrate restriction program on performance in a bout of isoinertial and isokinetic strength exercise. One female and five male subjects (mean +/- SD: age = 20.3 +/- 2.3 years; body mass = 74.6 +/- 11.5 kg; height 177.0 +/- 8.8 cm) performed isoinertial and isokinetic strength exercise under control conditions (no experimental intervention) and after a 2-day carbohydrate restriction program. The carbohydrate restriction program consisted of 60 minutes of cycling at 75% of peak cycle ergometer oxygen consumption (PVO2), followed by four 1-minute bouts at 100% of PVO2, followed by 2 days of reduced carbohydrate intake (1.2 +/- 0.5 g.kg(-1).d(-1)). Isoinertial strength exercise was three sets of squats with a load of 80% of one repetition maximum. Isokinetic strength exercise was five repetitions of leg extensions performed at five different contractile speeds (1.05, 2.09, 3.14, 4.19, and 5.24 rad.s(-1)). The carbohydrate restriction program caused a significant reduction in the number of squat repetitions performed. Torque at 0.52 rad from full extension (T30) was not significantly altered by carbohydrate restriction. Plasma lactate concentration postexercise was significantly lower after carbohydrate restriction. The fact that carbohydrate restriction reduces performance in isoinertial but not isokinetic strength exercise may be due to the different metabolic demands associated with the different exercise protocols used in the two modes of strength exercise.

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... Repeat maximal resistance exercise can result in a considerable reduction in muscle glycogen [4,5], but the extent that glycogen availability may limit the performance of repeat maximal efforts in a subsequent exercise session, is equivocal [8,9]. Symons and Jacobs [9] reported no significant effect of low muscle glycogen on peak torque, average torque, fatigue index, and total work during the performance of 50 consecutive isokinetic unilateral leg extensions. ...
... Symons and Jacobs [9] reported no significant effect of low muscle glycogen on peak torque, average torque, fatigue index, and total work during the performance of 50 consecutive isokinetic unilateral leg extensions. Similarly, Leveritt and Abernethy [8] found no significant effect of a glycogen depleting cycling exercise followed by a 2-d restricted carbohydrate diet (1.2 g•kg -1 •d -1 ) on performance (force) during isokinetic leg extensions. However, those authors did report that a carbohydrate restricted diet had a moderate negative effect on the total volume load during the first 2 sets of 3 sets to failure of the back squat exercise at 80% 1RM. ...
... However, those authors did report that a carbohydrate restricted diet had a moderate negative effect on the total volume load during the first 2 sets of 3 sets to failure of the back squat exercise at 80% 1RM. Though not measured, the carbohydrate restricted diet used in that study [8] had been reported previously to reduce muscle glycogen concentration [10]. Given that athletes are routinely involved in several days of intense training or competition, and the likelihood that glycogen depletion may inhibit performance, interventions that spare or better replenish muscle glycogen may enhance performance and also accentuate training adaptation [1]. ...
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Athletes in sports demanding repeat maximal work outputs frequently train concurrently utilizing sequential bouts of intense endurance and resistance training sessions. On a daily basis, maximal work within subsequent bouts may be limited by muscle glycogen availability. Recently, the ingestion of a unique high molecular weight (HMW) carbohydrate was found to increase glycogen re-synthesis rate and enhance work output during subsequent endurance exercise, relative to low molecular weight (LMW) carbohydrate ingestion. The effect of the HMW carbohydrate, however, on the performance of intense resistance exercise following prolonged-intense endurance training is unknown. Sixteen resistance trained men (23±3 years; 176.7±9.8 cm; 88.2±8.6 kg) participated in a double-blind, placebo-controlled, randomized 3-way crossover design comprising a muscle-glycogen depleting cycling exercise followed by ingestion of placebo (PLA), or 1.2 g•kg•bw-1 of LMW or HMW carbohydrate solution (10%) with blood sampling for 2-h post-ingestion. Thereafter, participants performed 5 sets of 10 maximal explosive repetitions of back squat (75% of 1RM). Compared to PLA, ingestion of HMW (4.9%, 90%CI 3.8%, 5.9%) and LMW (1.9%, 90%CI 0.8%, 3.0%) carbohydrate solutions substantially increased power output during resistance exercise, with the 3.1% (90% CI 4.3, 2.0%) almost certain additional gain in power after HMW-LMW ingestion attributed to higher movement velocity after force kinematic analysis (HMW-LMW 2.5%, 90%CI 1.4, 3.7%). Both carbohydrate solutions increased post-exercise plasma glucose, glucoregulatory and gut hormones compared to PLA, but differences between carbohydrates were unclear; thus, the underlying mechanism remains to be elucidated. Ingestion of a HMW carbohydrate following prolonged intense endurance exercise provides superior benefits to movement velocity and power output during subsequent repeated maximal explosive resistance exercise. This study was registered with clinicaltrials.gov (NCT02778373).
... Considerando a hipótese aguda, nosso grupo investigou o efeito da ingestão de carboidratos durante a execução do exercício de endurance sobre o subseqüente desempenho de força. Nossa hipótese era verificar se a ingestão de carboidratos poderia atenuar a depleção de glicogênio, dada a importância desse substrato para o exercício de força, conforme demonstrado anteriormente por diversos autores (11)(12)(13)(14) . Após um treino de corrida de 45 minutos, observamos redução (~40%) no número de repetições máximas no leg-press 45º. ...
... Esses resultados reforçam a hipótese aguda, considerando que a mesma atesta que a limitação do treinamento concorrente não é praticar duas modalidades que sejam incompatíveis em termos de adaptação (hipótese crônica) e, sim, o fato de o primeiro treino impedir a realização plena do segundo (hipótese aguda) (1,9,11) . ...
... Embora seja pouco provável que as alterações promovidas nos músculos da perna (ex: redução de substratos energéticos e/ou ocorrência de microlesões) pudessem interferir na produção de força dos músculos do braço e do peitoral, ainda existiria a possibilidade de o exercício de endurance afetar, de alguma maneira, o sistema nervoso. Nessa situação, seria plausível esperar o comprometimento da produção de força (11,22,23) . Por exemplo, caso ocorra redução da glicemia durante o exercício de endurance, a menor disponibilidade desse substrato poderia afetar o funcionamento do sistema nervoso, atenuando a produção de força (22) . ...
Article
Full-text available
Aim: the present study evaluated the effect of endurance exercise (running) on the subsequent strength performance of muscles of upper limbs and trunk. Methodology: Thirteen healthy female, university students, physically active were selected to compose the sample. The first phase of the experiment the subjects were submitted to an endurance exercise bout (treadmill), simulating a training session, with duration of 45 mi- nutes at 70% of the HR max. Immediately after the endurance exercise bout, the subjects performed strength tests (Dynamometry test - handgrip, 1RM test and maximal repetitions test at 70%-1RM in the bench press). Glycemia was measured in the beginning of the experiment and immediately before the strength tests. Re- sults: No significant difference was observed in the strength tests performance after the endurance exercise bout (Dynamometry, 1-RM and REPMAX - with no previous endurance exercise - 29.9 ± 3.8 kgf; 34.4 ± 3.1 kg; 1st set 12.5 ± 3.3 reps and 2 nd set 11.7 ± 2.7 reps vs. with previous endurance exercise - 29.2 ± 3.1 kgf; 33.9 ± 2.5 kg; 1 st set 13.2 ± 2.1 reps and 2 nd set 12.2 ± 2.8 reps). Regarding glycemia, no significant alteration was observed during the experiment. Conclusion: the endurance exercise bout did not affect the subsequent strength performance of the upper limbs and trunk. This data suggests that the common interference ob- served in the concurrent training is dependent on which muscular group has been recruited. Possibly, the adverse effect induced by the concurrent training, exclusively performed with lower extremities, is due to the residual fatigue installed in the muscles recruited in the previous activity. It is important to highlight that endurance exercise did not promote alteration in the glucose plasma concentration. The glycemia main- tenance associated with the lack of interference on the performance of the strength tests reinforces even more the hypothesis that the adverse effect of the concurrent training is probably caused by muscle-specific peripheral alterations.
... Repeat maximal resistance exercise can result in a considerable reduction in muscle glycogen [4,5], but the extent that glycogen availability may limit the performance of repeat maximal efforts in a subsequent exercise session, is equivocal [8,9]. Symons and Jacobs [9] reported no significant effect of low muscle glycogen on peak torque, average torque, fatigue index, and total work during the performance of 50 consecutive isokinetic unilateral leg extensions. ...
... Symons and Jacobs [9] reported no significant effect of low muscle glycogen on peak torque, average torque, fatigue index, and total work during the performance of 50 consecutive isokinetic unilateral leg extensions. Similarly, Leveritt and Abernethy [8] found no significant effect of a glycogen depleting cycling exercise followed by a 2-d restricted carbohydrate diet (1.2 g•kg -1 •d -1 ) on performance (force) during isokinetic leg extensions. However, those authors did report that a carbohydrate restricted diet had a moderate negative effect on the total volume load during the first 2 sets of 3 sets to failure of the back squat exercise at 80% 1RM. ...
... However, those authors did report that a carbohydrate restricted diet had a moderate negative effect on the total volume load during the first 2 sets of 3 sets to failure of the back squat exercise at 80% 1RM. Though not measured, the carbohydrate restricted diet used in that study [8] had been reported previously to reduce muscle glycogen concentration [10]. Given that athletes are routinely involved in several days of intense training or competition, and the likelihood that glycogen depletion may inhibit performance, interventions that spare or better replenish muscle glycogen may enhance performance and also accentuate training adaptation [1]. ...
... Lambert et al. (28) recommends a CHO intake of 5-6 g/kg per d or 55-60 % of daily energy intake for bodybuilders. However, and of particular note, it has been observed that daily CHO intake considerably less than such recommendations does not impair resistance-based exercise performance (30,32,33,(38)(39)(40) or hinder the requisite post-exercise cellular signalling responses for adaptation (29,31,41,42) . ...
... While glycogen serves as a substrate during resistance training, the total energy expenditure of strength athletes is less than that of mixed sport and endurance athletes (13) , and experimental evidence has yet to confirm a minimum threshold of daily CHO intake for resistance trainees. Although Leveritt & Abernathy (39) reported a decrease in the number of back squat repetitions to failure following a low-CHO diet consisting of 1·26 g/kg per d (111·9 g/d; 19·3 % of energy intake) for 2 d in recreationally active subjects, the following investigations have demonstrated that modest, and even minimal, amounts of CHO may maintain resistance-based exercise performance (Table 1). Mitchell et al. (30) found that volumes (load × repetitions) of back squats, leg press and knee extensions were not compromised following 48 h of 0·4 g/kg per d CHO (31·6 g/d; 4·1 % of energy intake) compared with a high CHO intake of 7·7 g/kg per d (642·6 g/d; 80·2 % of energy intake) in recreationally trained males. ...
... The maintenance of strength and power performance in response to a short-term CHO-restricted diet (i.e. 2-4 d) (39,44) may not be unexpected, as this may be an insufficient time table to substantially decrease muscle glycogen stores. A number of the reported studies, however, did not collect skeletal muscle samples to assess intramuscular glycogen levels. ...
Article
Full-text available
Substantial research has been completed examining the impact of carbohydrate (CHO) intake on endurance exercise, whereas its role in resistance-based exercise performance, adaptation and cell signalling has yet to be fully characterised. This empirical shortcoming has precluded the ability to establish specific CHO recommendations for resistance exercise. This results in recommendations largely stemming from findings based on endurance exercise and/or anecdotal evidence despite the distinct energetic demands and molecular responses mediating adaptation from endurance- and resistance-based exercise. Moreover, the topic of CHO and exercise has become one of polarising nature with divergent views – some substantiated, others lacking evidence. Current literature suggests a moderately high daily CHO intake (3–7 g/kg per d) for resistance training, which is thought to prevent glycogen depletion and facilitate performance and adaptation. However, contemporary investigation, along with an emerging understanding of the molecular underpinnings of resistance exercise adaptation, may suggest that such an intake may not be necessary. In addition to the low likelihood of true glycogen depletion occurring in response to resistance exercise, a diet restrictive in CHO may not be detrimental to acute resistance exercise performance or the cellular signalling activity responsible for adaptation, even when muscle glycogen stores are reduced. Current evidence suggests that signalling of the mammalian target of rapamycin complex 1, the key regulatory kinase for gene translation (protein synthesis), is unaffected by CHO restriction or low muscular glycogen concentrations. Such findings may call into question the current view and subsequent recommendations of CHO intake with regard to resistance-based exercise.
... Several studies use the term "residual fatigue" to refer to the carryover detrimental effects generated by previous exercise (i.e., aerobic exercise), which would cause impairment on subsequent exercise performance (e.g., strength exercise) (8,30,31,37,39,43,45,47). Thus, owing to residual fatigue from previous aerobic exercise, the individual would start ST without adequate rest or recovery, decreasing the capacity to develop force and/or to accomplish the same total training volume during the ST session (8,37,39,43,45,47). ...
... Moreover, considering the evidence in the literature demonstrating that total training volume is an important variable for strength and muscle hypertrophy gains (29,40,44,50,51) and that acute volume performed is reduced in a CT session (8,30,31,37,39,43,45,47), it is quite plausible to expect lower strength and hypertrophy adaptations Strength and Conditioning Journal | www.nsca-scj.com after a period of CT. ...
... To eliminate or at least minimize the acute interference effects, the utilization of ergogenic aids has been considered by some investigations (2,3,19,20,30,45). ...
Article
This review analyzes relevant variables involved in acute interference effects of concurrent training (CT) sessions of aerobic exercise followed by strength exercises. The aerobic exercise intensity, mode, volume, duration of recovery interval between exercises, muscle groups involved, and utilization of ergogenic aids are the variables identified in this review. High-intensity interval aerobic exercises result in more pronounced negative effects on strength-endurance exercise but not in maximal strength. Cycling results in more negative effects on strength-endurance performance exercise than running. A 4-hour to 8-hour recovery interval seems to be enough to avoid interference on strength-endurance performance. Reduction in strength-endurance performance is located in muscle groups involved in both exercises. Low aerobic exercise volume (3 km) with ∼18 minutes of duration does not diminish strength endurance, whereas higher volumes (5 and 7 km) with ∼30 and ∼42 minutes of duration, respectively, generate impairments. Caffeine, carbohydrate, and beta-alanine are not able to revert the deleterious effect on strength-endurance performance, whereas creatine and capsaicin analog supplementation are. Thus, these variables must be taken into consideration to prescribe and organize a CT session. This information may help coaches to organize exercise sessions that minimize or avoid the impairment in strength performance after aerobic exercises.
... Considerando a hipótese aguda, nosso grupo investigou o efeito da ingestão de carboidratos durante a execução do exercício de endurance sobre o subseqüente desempenho de força. Nossa hipótese era verificar se a ingestão de carboidratos poderia atenuar a depleção de glicogênio, dada a importância desse substrato para o exercício de força, conforme demonstrado anteriormente por diversos autores (11)(12)(13)(14) . Após um treino de corrida de 45 minutos, observamos redução (~40%) no número de repetições máximas no leg-press 45º. ...
... Esses resultados reforçam a hipótese aguda, considerando que a mesma atesta que a limitação do treinamento concorrente não é praticar duas modalidades que sejam incompatíveis em termos de adaptação (hipótese crônica) e, sim, o fato de o primeiro treino impedir a realização plena do segundo (hipótese aguda) (1,9,11) . ...
... Embora seja pouco provável que as alterações promovidas nos músculos da perna (ex: redução de substratos energéticos e/ou ocorrência de microlesões) pudessem interferir na produção de força dos músculos do braço e do peitoral, ainda existiria a possibilidade de o exercício de endurance afetar, de alguma maneira, o sistema nervoso. Nessa situação, seria plausível esperar o comprometimento da produção de força (11,22,23) . Por exemplo, caso ocorra redução da glicemia durante o exercício de endurance, a menor disponibilidade desse substrato poderia afetar o funcionamento do sistema nervoso, atenuando a produção de força (22) . ...
Article
Full-text available
AIM: the present study evaluated the effect of endurance exercise (running) on the subsequent strength performance of muscles of upper limbs and trunk. METHODOLOGY: Thirteen healthy female, university students, physically active were selected to compose the sample. The first phase of the experiment the subjects were submitted to an endurance exercise bout (treadmill), simulating a training session, with duration of 45 minutes at 70% of the HRmax. Immediately after the endurance exercise bout, the subjects performed strength tests (Dynamometry test - handgrip, 1RM test and maximal repetitions test at 70%-1RM in the bench press). Glycemia was measured in the beginning of the experiment and immediately before the strength tests. RESULTS: No significant difference was observed in the strength tests performance after the endurance exercise bout (Dynamometry, 1-RM and REPMAX - with no previous endurance exercise - 29.9 ± 3.8 kgf; 34.4 ± 3.1 kg; 1st set 12.5 ± 3.3 reps and 2nd set 11.7 ± 2.7 reps vs. with previous endurance exercise - 29.2 ± 3.1 kgf; 33.9 ± 2.5 kg; 1st set 13.2 ± 2.1 reps and 2nd set 12.2 ± 2.8 reps). Regarding glycemia, no significant alteration was observed during the experiment. CONCLUSION: the endurance exercise bout did not affect the subsequent strength performance of the upper limbs and trunk. This data suggests that the common interference observed in the concurrent training is dependent on which muscular group has been recruited. Possibly, the adverse effect induced by the concurrent training, exclusively performed with lower extremities, is due to the residual fatigue installed in the muscles recruited in the previous activity. It is important to highlight that endurance exercise did not promote alteration in the glucose plasma concentration. The glycemia maintenance associated with the lack of interference on the performance of the strength tests reinforces even more the hypothesis that the adverse effect of the concurrent training is probably caused by muscle-specific peripheral alterations.
... However, since the strength assessment took place 2 hours following the glycogen depletion protocol it is unclear whether the reductions in force were the result of glycogen depletion or general fatigue due to the prolonged exercise. Leveritt and Abernethy [70] used a similar glycogen depletion protocol followed by two days of restricted carbohydrate intake (1.2 + 0.5 g  kg -1 , 19 + 3% energy intake). Compared to a control condition, carbohydrate restriction reduced the total amount of repetitions performed during isoinertial squat with 80% 1RM but did not affect isokinetic torque during the knee extension. ...
... Mitchell et al. [71] subjected subjects to a similar depletion protocol followed by two days of a high (7.6 g  kg -1 ) or low (0.34 g  kg -1 ) carbohydrate diet. In contrast to Leveritt and Abernethy [70], no differences in total repetitions of squat, leg press, or leg extensions were found between conditions. These conflicting results seem paradoxical. ...
Article
It is commonly accepted that adequate carbohydrate availability is necessary for optimal endurance performance. However, for strength- and physique-based athletes, sports nutrition research and recommendations have focused on protein ingestion, with far less attention given to carbohydrate. Varying resistance exercise protocols, such as differences in intensity, volume, and intra-set rest prescriptions between strength-training and physique-training goals elicit different metabolic responses, which may necessitate different carbohydrate needs. The results of several acute and chronic training studies suggest that while severe carbohydrate restriction may not impair strength adaptations during a resistance training program, consuming an adequate amount of carbohydrate in the days leading up to testing may enhance maximal strength and strength-endurance performance. Although several molecular studies demonstrate no additive increases in post-exercise mTORC1 phosphorylation with carbohydrate and protein compared protein ingestion alone, the effects of chronic resistance training with carbohydrate restriction on muscle hypertrophy are conflicting and require further research to determine a minimal carbohydrate threshold necessary to optimize muscle hypertrophy. This review summarizes the current knowledge regarding carbohydrate availability and resistance training outcomes and poses new research questions that will better help guide carbohydrate recommendations for strength and physique athletes. Additionally, given that success in physique sports is based on subjective appearance, and not objective physical performance, we also review the effects of sub-chronic carbohydrate ingestion during contest preparation on aesthetic appearance.
... This difference in timing means that the time for RWG and recovery of fluid and fuel stores is limited in these athletes. Because methods of RWL are generally based on dietary restriction and dehydration (5,24), it is noteworthy that states of hypohydration and low carbohydrate intake can both negatively impact strength outcomes (19,27). ...
... The subjects were separated into 4 distinct groups (A, B, C, and D) based on these criteria. Nineteen (19) respondents did not fit the criteria of any of the 4 predefined groups and were excluded from the analysis. Owing to the considerably larger sample size in group A (n 5 233) compared with other groups and small sample sizes of groups B (n 5 35), C (n 5 31), and D (n 5 22), this study focused solely on group A for the purpose of detailed analysis and discussion. ...
Article
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Nolan, D, Lynch, AE, and Egan, B. Self-reported prevalence, magnitude, and methods of rapid weight loss in male and female competitive powerlifters. J Strength Cond Res XX(X): 000-000, 2019-Rapid weight loss (RWL) is common practice in weight category sports, but no empirical data exist documenting the weight-making practices of competitive strength athletes. This study investigated the self-reported prevalence, magnitude, and methods of RWL used by male and female powerlifters when preparing for competition. Competitive powerlifters (n = 321; M/F, 194/127) completed an anonymous online questionnaire previously validated for assessment of methods of RWL. Respondents were categorized by their federation's respective antidoping policy, weigh-in procedure, and degree of assistive equipment allowed, in addition to their use or not of RWL. Subgroup analyses were performed on the largest category of respondents (n = 200, M/F, 117/83; ≤2-hour weigh-in, drug-tested, "raw") based on sex, weight category, and competitive status. Prevalence of RWL was 85.8%, with an average RWL of 3.0 ± 1.9% body mass and an RWL score of 25.1 ± 7.4. Neither sex nor weight category influenced the RWL score, but in male athletes, a lower RWL score (22.7 ± 6.3) was reported in athletes in the lowest tertile of the Wilks score (p = 0.015). Frequencies of "always use" were reported as 54.0% for fluid restriction and 49.0% for water loading. Coaches (37.5%) and online resources (35.0%) were "very influential" on RWL practices in these athletes, while doctors (85.5%) and dieticians (63.0%) were reported to be "not influential." The prevalence of RWL is high in competitive powerlifting, and the methods used are akin to other weight category sports, but the reported RWL scores are lower than reported in combat sports with longer recovery periods after weigh-in.
... The relationship between muscle glycogen content and high-intensity exercise performance has been investigated in numerous studies originally in the 1980s [75][76][77][78][79][80][81][82][83][84] and 1990s [29][30][31][85][86][87][88][89][90][91][92], while only a few additional studies since then have provided additional insight [93][94][95][96][97][98][99]. The performance measures in these studies can be subdivided into (I) continuous high-intensity exercise (> 60 s duration), (II) single or repeated sprints (< 60 s duration) and (III) neuromuscular contractile performance (voluntary or electrically induced maximal or near-maximal contractions). ...
... Finally, divergent findings appear for the capacity to perform resistance or power exercise in purpotedly lowered glycogen conditions as one study observed an impairment in total work capacity [98], whereas two studies did not show any effect [90,94]. In a study by Leveritt et al. [92] a reduced performance was only observed for maximal isoinertial strength including multiple repetitions, but not in a limited series of brief isokinetic knee-extensions at different speeds, which likely poses less of a challenge to the glycogenolytic system. In summary, no effects of muscle glycogen availability are observed when evaluating the performance of brief electrically or voluntarily induced single contractions, which may be explained by lower glycogenolytic stress in such brief contractions. ...
Article
Full-text available
Muscle glycogen is the main substrate during high-intensity exercise and large reductions can occur after relatively short durations. Moreover, muscle glycogen is stored heterogeneously and similarly displays a heterogeneous and fiber-type specific depletion pattern with utilization in both fast- and slow-twitch fibers during high-intensity exercise, with a higher degradation rate in the former. Thus, depletion of individual fast- and slow-twitch fibers has been demonstrated despite muscle glycogen at the whole-muscle level only being moderately lowered. In addition, muscle glycogen is stored in specific subcellular compartments, which have been demonstrated to be important for muscle function and should be considered as well as global muscle glycogen availability. In the present review, we discuss the importance of glycogen metabolism for single and intermittent bouts of high-intensity exercise and outline possible underlying mechanisms for a relationship between muscle glycogen and fatigue during these types of exercise. Traditionally this relationship has been attributed to a decreased ATP resynthesis rate due to inadequate substrate availability at the whole-muscle level, but emerging evidence points to a direct coupling between muscle glycogen and steps in the excitation–contraction coupling including altered muscle excitability and calcium kinetics.
... However, carbohydrate intake has an important role in the bodybuilder's diet as a regulator of thyroid hormones and as a contributor to micronutrient needs [55,56]. Further, a very low carb diet could limit regeneration of adenosine triphosphate (ATP) and limit the muscles' ability to contract with high force [57,58]. During high intensity exercise, muscle-glycogen is the major contributor of substrate and it has been shown that glycolysis provides~80% of ATP demand from one set of elbow flexion when taken to muscular failure [59]. ...
... Further, it has been suggested that when glycogen stores are too low (~70 mmol/kg), this may inhibit the release of calcium and hasten the onset of muscle fatigue [62]. Low muscle glycogen significantly reduces the number of repetitions performed when three sets of squats at 80% 1 RM are performed [57]. ...
Article
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Many nutrition practices often used by bodybuilders lack scientific support and can be detrimental to health. Recommendations during the dieting phase are provided in the scientific literature, but little attention has been devoted to bodybuilders during the off-season phase. During the off-season phase, the goal is to increase muscle mass without adding unnecessary body fat. This review evaluated the scientific literature and provides nutrition and dietary supplement recommendations for natural bodybuilders during the off-season phase. A hyper-energetic diet (~10–20%) should be consumed with a target weight gain of ~0.25–0.5% of bodyweight/week for novice/intermediate bodybuilders. Advanced bodybuilders should be more conservative with the caloric surplus and weekly weight gain. Sufficient protein (1.6–2.2 g/kg/day) should be consumed with optimal amounts 0.40–0.55 g/kg per meal and distributed evenly throughout the day (3–6 meals) including within 1–2 hours pre- and post-training. Fat should be consumed in moderate amounts (0.5–1.5 g/kg/day). Remaining calories should come from carbohydrates with focus on consuming sufficient amounts (≥3–5 g/kg/day) to support energy demands from resistance exercise. Creatine monohydrate (3–5 g/day), caffeine (5–6 mg/kg), beta-alanine (3–5 g/day) and citrulline malate (8 g/day) might yield ergogenic effects that can be beneficial for bodybuilders.
... Considering the so-called potentially critical nutrients (vitamin B12, vitamin D, iron, iodine, calcium, zinc, long-chain omega-3-fatty acids), vegan diets in particular have been formerly described as deficient [83] (pp. [229][230][231][232][233][234]. However, some of these nutrients (calcium, iodine, iron, vitamin D, zinc) are not only key for vegans, but critical for omnivores and vegetarians, too. ...
... However, preserving skeletal muscle mass is important to maintain metabolic health and functional capac-the nutritional foundation of health, but are also of even more significance to successful athletes, since carbohydrates are key at high metabolic rates and promotes exercise performance. Resulting from this, any athlete should fuel primarily by carbohydrates -even strength athletes [231,[232][233][234][235] -, with at least 50% of daily energy, or even 60-65% to meet the energy needs considered by sports nutrition recommendations [236]. This is easy to achieve through the high-carbohydrate nature of a vegan diet. ...
Article
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https://clinmedjournals.org/International-Journal-of-Sports-and-Exercise-Medicine.php?fbclid=IwAR2VOazGWyn0X6pk574PNVzXRy3yOFjpLkSQ3SmcJxFe68cyEBZs2a641JI or directly from https://clinmedjournals.org/articles/ijsem/international-journal-of-sports-and-exercise-medicine-ijsem-6-165.pdf?fbclid=IwAR0-UxOUaOZySmOSRGWTPj267VkDhJPwQIH8elrmQHtG6IgdnMXBzR-ieZg
... At the best of our knowledge, the present study is the first to investigate the effects of different hypoenergetic diets on isokinetic strength of women. Previous results with men 29,30 revealed that maximum isokinetic endurance and strength performance were not impaired by a low muscle glycogen content (intense exercise designed to deplete glycogen stores followed by two days of a very low carbohydrate intake). Otherwise, Leveritt and Abernethy 30 have demonstrated an impaired isotonic strength perfor-mance on the first two sets of squats performed at 80% of 1 RM. ...
... Previous results with men 29,30 revealed that maximum isokinetic endurance and strength performance were not impaired by a low muscle glycogen content (intense exercise designed to deplete glycogen stores followed by two days of a very low carbohydrate intake). Otherwise, Leveritt and Abernethy 30 have demonstrated an impaired isotonic strength perfor-mance on the first two sets of squats performed at 80% of 1 RM. ...
Article
Weight reduction strategies usually include diet and regular physical activity. A very low-carbohydrate and high protein diet (VLCD) may be preferred instead of a low energy conventional diet (CONV). The effects of VLCD on strength performance are yet to be understood. Aim of the study is to determine the effects of two different restrictive diets on strength performance. Sedentary women were assigned to either a VLCD (<40 g carbohydrate; n=12) or a CONV diet (500 to 800 kcal restrictive; 48%, 22% and 30% from carbohydrate, protein and fat, respectively; n=12). Knee extension isokinetic strength tests (3 yen 15 reps at 60 degrees .s-1, with 90 or 180 s rest interval between sets) were performed prior and after a one week diet period. Both groups reduced body mass (VLCD: -2.6+/-1.0% vs. CONV: -1.9+/-1.3%; P<0.05), with no between diets effect. The sum of the total work in three sets (ATW) was 4850+/-1002 J vs. 4801+/-973 J with 90 s rest interval, and 4812+/-1174 J vs. 4812+/-1210 J with 180 s rest interval, respectively, in the pre vs. post-VLCD period. For CONV, values were 4709+/-729 J vs. 4530+/-996 J with 90 s rest interval, and 4760+/-732 J vs. 4816+/-702 J with 180 s rest interval, respectively, in the pre vs. post-CONV treatment. No significant differences were detected in the ATW between groups. Short-term hypoenergetic diets, irrespective of the carbohydrate content, seem to reduce significantly body mass, but do not impair acute strength performance.
... The degree of glycogen depletion is likely dependent on the type, intensity, and duration of the exercise session, with hypertrophytype resistance exercise (i.e., higher repetition and moderate load exercise) likely to produce larger reductions in muscle glycogen (31). Previous studies have demonstrated that commencing resistance-type exercise with suboptimal muscle glycogen levels can impair performance capabilities (17,23). Although this is not a universal finding (25), muscle glycogen seems to be an important fuel source for resistance exercise performance, and pre-exercise glycogen stores might therefore affect performance and possible training quality/ adaptation. ...
... Indeed, some evidence supports the notion that preresistance exercise carbohydrate intake/glycogen stores might be an important determinant of performance. Leveritt and Abernethy (23) reported that a muscle glycogendepleting regimen (cycling exercise followed by 2 days of low-carbohydrate diet) produced a ;20% reduction in the number of repetitions completed in 3 sets of back squat to fatigue. Interestingly, Leveritt and Abernethy (23) also measured performance in 5 sets of 5 repetitions of isokinetic dynamometry, observing no difference between conditions. ...
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Bin Naharudin, MN, Yusof, A, Shaw, H, Stockton, M, Clayton, DJ, and James, LJ. Breakfast omission reduces subsequent resistance exercise performance. J Strength Cond Res XX(X): 000-000, 2019-Although much research has examined the influence of morning carbohydrate intake (i.e., breakfast) on endurance performance, little is known about its effects on performance in resistance-type exercise. Sixteen resistance-trained men (age 23 6 4 years, body mass 77.56 6 7.13 kg, and height 1.75 6 0.04 m) who regularly ($3 day/wk 21) consumed breakfast completed this study. After assessment of 10 repetition maximum (10RM) and familiarization process, subjects completed 2 randomized trials. After an overnight fast, subjects consumed either a typical breakfast meal (containing 1.5 g of carbohydrate/kg; breakfast consumption [BC]) or a water-only breakfast (breakfast omission [BO]). Two hours later, subjects performed 4 sets to failure of back squat and bench press at 90% of their 10RM. Sensations of hunger, fullness, desire to eat, and prospective food consumption were collected before, as well as immediately , 1 hour and 2 hours after BC/BO using 100-mm visual analogue scales. Total repetitions completed were lower during BO for both back squat (BO: 58 6 11 repetitions; BC: 68 6 14 repetitions; effect size [ES] = 0.98; p , 0.001) and bench press (BO: 38 6 5 repetitions; BC: 40 6 5 repetitions; ES = 1.06; p , 0.001). Fullness was greater, whereas hunger, desire to eat, and prospective food consumption were lower after a meal for BC compared with BO (p , 0.001). The results of this study demonstrate that omission of a pre-exercise breakfast might impair resistance exercise performance in habitual breakfast consumers. Therefore, consumption of a high-carbohydrate meal before resistance exercise might be a prudent strategy to help maximize performance. ... T he loads lifted during resistance training are traditionally prescribed as a percentage of predetermined maximal strength (1 repetition maximum [1RM]) (3,25). However, this approach does not account for day-to-day fluctuations in strength (22), which can vary regularly because of a range of factors, including training-related fatigue (9,13), food and fluid intake (23,26,36), sleep quantity and quality (6,32), and psychological stress levels (28). The effects of these factors on performance during resistance training are highly individualized, and coaches are often unable to account for them. ... ... Mean measured 1RM, MVC, and perceived muscle soreness are presented in Table 1 The mean predicted 1RM scores for the 1RM MVT , 1RM LD0 , and 1RM FV models are presented in Table 2. For the 1RM MVT , there was no interaction effect between time and method of 1RM assessment ( For the 1RM LD0 , there was no interaction between time and model of 1RM assessment (F 3.10, 52.70 = 1.632; p = 0.192; ƞ 2 = 0.088) or main effect for the method of 1RM assessment (F 1.58, 26.93 = 1.906; p = 0.172; ƞ 2 = 0.101). There was a significant main effect for time (F 2.00, 34.00 = 6.009; p = 0.006; ƞ 2 = 0.261), with post hoc confirming that 1RM LD0 values decreased from baseline at 24 hours (p = 0.003, d = 0.01-0.08) ... Article The purpose of this study was to investigate using load-velocity relationships to quantify fluctuations in maximal strength (1-repetition maximum; 1RM) which occur as a result of training-induced fatigue. The nineteen well-trained males (age: 24.3±2.9 years, height: 180.1±5.9 cm, body mass: 84.2±10.5 kg, squat 1RM: 151.1 ± 25.7 kg) who were recruited for this study attended five sessions. After baseline strength testing, individual load-velocity relationships were established using mean concentric velocity during visits 2, 4 and 5, with visit 3 consisting of a bout of fatiguing exercise (5 sets of squats performed to muscular failure with 70% 1RM). Predicted 1RM values were calculated using the minimal velocity threshold (1RMMVT), load at zero velocity (1RMLD0) and force-velocity (1RMFV) methods. Measured 1RM, maximal voluntary contractions, and perceived muscle soreness were used to examine the effects of fatigue in relation to the predicted 1RM scores. The 1RMMVT and 1RMLD0 demonstrated a very strong and strong correlation with measured 1RM during each of the sessions (r = 0.90-0.96 and r = 0.77-0.84, respectively), while no strong significant correlations were observed for the 1RMFV. Further analysis using Bland-Altman plots demonstrated substantial inter-individual variation associated with each method. These results suggest that load-velocity based 1RM predictions are not accurate enough to be used for daily training load prescription, as has been previously suggested. Nevertheless, these predictions are practical to implement during an individual’s warm- up, and may be useful to indicate general fluctuations in performance potential, particularly if used in conjunction with other common monitoring methods. ... Manipulations which have been used during highintensity exercise that approximates resistance exercise are creatine ingestion to elevate intramuscular stores of PCr, [18][19][20][21][22] changes in extracellular hydrogen ion concentration through sodium bicarbonate, [23][24][25] sodium citrate supplements, [26][27][28] and/or ammonium chloride ingestion [29,30] and carbohydrate restriction or supplementation to alter carbohydrate availability. [31][32][33][34][35][36] Fatigue during resistance exer- cise is likely to be multifactorial; however, PCr depletion, intramuscular acidosis, and a reduction in muscle glycogen content as causes of fatigue during multiple bout resistance exercise will be considered in sections 3.1, 3.2 and 4.2. ... ... [15] A glycogen-sparing mechanism as a result of carbohydrate feedings during high-intensity intermittent exercise has been recently documented during intense intermittent running [35] and during resistance exercise. [32] Data which support the concept of a carbohydrate limitation during resistance exercise come from Leveritt and Abernathy [34] who reported that exhaustive exercise followed by 2 days of carbohydrate restriction (1.2g carbohydrate per day; carbohydrate 19% of total energy intake) resulted in a significant 21% reduction in the number of repetitions performed during three sets of isoinertial squats. ... Article Full-text available Resistance exercise is an activity performed by individuals interested in competition, those who wish to improve muscle mass and strength for other sports, and for individuals interested in improving their strength and physical appearance. In this review we present information suggesting that phosphocreatine depletion, intramuscular acidosis and carbohydrate depletion are all potential causes of the fatigue during resistance exercise. In addition, recommendations are provided for nutritional interventions, which might delay muscle fatigue during this type of activity. ... Haff [66] reported a significant benefit of consuming a carbohydrate supplement versus a placebo during resistance training, with those taking the supplement better able to perform a greater number of sets and repetitions. Additionally, muscle glycogen depletion in conjunction with aerobic exercise has been found to compromise muscular strength performance [67]. Therefore, resistance training performance will be enhanced when diet or supplementation allows the maintenance of intramuscular glycogen stores. ... Article Full-text available Competitive bodybuilders are well known for extreme physique traits and extremes in diet and training manipulation to optimize lean mass and achieve a low body fat. Although many of the dietary dogmas in bodybuilding lack scientific scrutiny, a number, including timing and dosing of high biological value proteins across the day, have more recently been confirmed as effective by empirical research studies. A more comprehensive understanding of the dietary intakes of bodybuilders has the potential to uncover other dietary approaches, deserving of scientific investigation, with application to the wider sporting, and potential health contexts, where manipulation of physique traits is desired. Our objective was to conduct a systematic review of dietary intake practices of competitive bodybuilders, evaluate the quality and currency of the existing literature, and identify research gaps to inform future studies. A systematic search of electronic databases was conducted from the earliest record until March 2014. The search combined permutations of the terms 'bodybuilding', 'dietary intake', and 'dietary supplement'. Included studies needed to report quantitative data (energy and macronutrients at a minimum) on habitual dietary intake of competitive bodybuilders. The 18 manuscripts meeting eligibility criteria reported on 385 participants (n = 62 women). Most studies were published in the 1980-1990s, with three published in the past 5 years. Study methodological quality was evaluated as poor. Energy intake ranged from 10 to 24 MJ/day for men and from 4 to 14 MJ/day for women. Protein intake ranged from 1.9 to 4.3 g/kg for men and from 0.8 to 2.8 g/kg for women. Intake of carbohydrate and fat was <6 g/kg/day and below 30 % of energy, respectively. Carbohydrate intakes were below, and protein (in men) intakes were higher than, the current recommendations for strength athletes, with no consideration for exploration of macronutrient quality or distribution over the day. Energy intakes varied over different phases of preparation, typically being highest in the non-competition (>6 months from competition) or immediate post-competition period and lowest during competition preparation (≤6 months from competition) or competition week. The most commonly reported dietary supplements were protein powders/liquids and amino acids. The studies failed to provide details on rationale for different dietary intakes. The contribution of diet supplements was also often not reported. When supplements were reported, intakes of some micronutrients were excessive (~1000 % of US Recommended Dietary Allowance) and above the tolerable upper limit. This review demonstrates that literature describing the dietary intake practices of competitive bodybuilders is dated and often of poor quality. Intake reporting required better specificity and details of the rationale underpinning the use. The review suggests that high-quality contemporary research is needed in this area, with the potential to uncover dietary strategies worthy of scientific exploration. ... Insulin is important to postexercise recovery because it promotes the restoration of muscle glycogen stores (which can be considerably lowered during exercise) by moving glucose from circulation into the muscle cells. The inability to restore muscle glycogen levels after exercise may result in decrements in subsequent strength performance (49). Exercise also mechanically produces microtears in the muscle fibers (15), particularly after exercise incorporating eccentric contractions. ... Article Full-text available THIS REVIEW SUMMARIZES THE EMPIRICAL RESEARCH OF THE EFFECTIVENESS, SAFETY, AND DOSAGES OF THE LESSER-KNOWN, BUT COMMONLY ADDED, SUPPORTIVE INGREDIENTS IN MULTI-INGREDIENT PERFORMANCE SUPPLEMENTS (MIPS). PRIMARY INGREDIENTS THAT ARE WELL KNOWN AND PREVIOUSLY REVIEWED (I.E., CAFFEINE, CREATINE, BETA-ALANINE) ARE EXCLUDED FROM THIS REVIEW. THE IMPROVEMENTS REPORTED ARE COMMONLY MEDIATED BY SECONDARY MECHANISMS SUCH AS IMPROVED BLOOD FLOW, PROTEIN BALANCE, METABOLISM, AND ANTIOXIDANT STATUS. OVERWHELMING EVIDENCE EXISTS SUGGESTING THAT THE SUPPORTIVE INGREDIENTS IN MIPS ARE SAFE TO USE; HOWEVER, THE AMOUNT PRESENT IN MOST MIPS IS LIKELY TOO SMALL TO ELICIT STRENGTH, POWER, OR RECOVERY RESPONSES. ... Higherrepetition, moderate-load training characteristic of programming prescribed to promote skeletal muscle hypertrophy results in the greatest reductions in muscle glycogen stores (Pascoe et al., 1993), an effect most pronounced in type II fibres (Koopman et al., 2006). Reductions in muscle glycogen stores have been associated with performance impairment in both isokinetic torque (Jacobs, Kaiser, & Tesch, 1981) and isoinertial resistance training capacity (Leveritt & Abernethy, 1999), although this effect is not always evident (Mitchell, DiLauro, Pizza, & Cavender, 1997) and possibly dependent on the method used to induce a state of glycogen depletion. Nonetheless, it is conceivable that impaired training or competition performance could occur in any session or event that relied on rapid and repeated glycogen breakdown. ... Article Full-text available Strength and power athletes are primarily interested in enhancing power relative to body weight and thus almost all undertake some form of resistance training. While athletes may periodically attempt to promote skeletal muscle hypertrophy, key nutritional issues are broader than those pertinent to hypertrophy and include an appreciation of the sports supplement industry, the strategic timing of nutrient intake to maximize fuelling and recovery objectives, plus achievement of pre-competition body mass requirements. Total energy and macronutrient intakes of strength-power athletes are generally high but intakes tend to be unremarkable when expressed relative to body mass. Greater insight into optimization of dietary intake to achieve nutrition-related goals would be achieved from assessment of nutrient distribution over the day, especially intake before, during, and after exercise. This information is not readily available on strength-power athletes and research is warranted. There is a general void of scientific investigation relating specifically to this unique group of athletes. Until this is resolved, sports nutrition recommendations for strength-power athletes should be directed at the individual athlete, focusing on their specific nutrition-related goals, with an emphasis on the nutritional support of training. ... Carbohydrate requirements are increased among athletes and other physically active individuals. (ADA 2000) (Jacobs 1999) (Haff 1999) (Leveritt 1999). ... ... One study demonstrated a significant decrease in the number of squats performed after CHO depletion, interestingly, there was no reduction in the number of isokinetic knee extensions performed under the same conditions. 180 Because of the wide variety of protocols used in the above studies and because fatigue is a multifactorial phenomenon, it is difficult to generalize the effect of glycogen depletion on resistance exercise. There is also very little research regarding the affect of CHO supplementation prior to or during resistance training on subsequent exercise performance. ... Article Full-text available ... However, like protein, carbohydrate intake needs to be customized to the individual. Inadequate carbohydrate can impair strength training [41] and consuming adequate carbohydrate prior to training can reduce glycogen depletion [42] and may therefore enhance performance. ... Article Full-text available The popularity of natural bodybuilding is increasing; however, evidence-based recommendations for it are lacking. This paper reviewed the scientific literature relevant to competition preparation on nutrition and supplementation, resulting in the following recommendations. Caloric intake should be set at a level that results in bodyweight losses of approximately 0.5 to 1%/wk to maximize muscle retention. Within this caloric intake, most but not all bodybuilders will respond best to consuming 2.3-3.1 g/kg of lean body mass per day of protein, 15-30% of calories from fat, and the reminder of calories from carbohydrate. Eating three to six meals per day with a meal containing 0.4-0.5 g/kg bodyweight of protein prior and subsequent to resistance training likely maximizes any theoretical benefits of nutrient timing and frequency. However, alterations in nutrient timing and frequency appear to have little effect on fat loss or lean mass retention. Among popular supplements, creatine monohydrate, caffeine and beta-alanine appear to have beneficial effects relevant to contest preparation, however others do not or warrant further study. The practice of dehydration and electrolyte manipulation in the final days and hours prior to competition can be dangerous, and may not improve appearance. Increasing carbohydrate intake at the end of preparation has a theoretical rationale to improve appearance, however it is understudied. Thus, if carbohydrate loading is pursued it should be practiced prior to competition and its benefit assessed individually. Finally, competitors should be aware of the increased risk of developing eating and body image disorders in aesthetic sport and therefore should have access to the appropriate mental health professionals. ... Nesse sentido, é consenso que a base para a prescrição de exercício em treinamento contra-resistência (TCR) se estabelece através da relação entre o percentual de 1RM e o número de repetições (1) . Por outro lado, estudos anteriores têm mostrado que inúmeros fatorescomo o nível de condicionamento físico (2) , o grupamento muscular (3) , sono (4) , alimentação (5) , ritmo cronobiológico (6) , motivação (7) , ciclo menstrual (8) e a fadiga muscular (9) -interferem efetivamente em tal relação, resultando em distintas intensidades para dado número de repetições. ... Article Full-text available O objetivo do presente estudo foi desenvolver uma equação para predição da carga de uma repetição máxima (1RM) em homens e mulheres, usando exclusivamente as características antropométricas. Participaram deste estudo 44 jovens de baixo risco, com experiência em treinamento de força, sendo 22 do sexo masculino (23 ± 4anos, 76,6 ± 12,7kg, 173,9 ± 5,5cm, 11 ± 4,5% de gordura) e 22 do feminino (22 ± 4anos, 54 ± 6,0kg, 161 ± 5,8cm, 18 ± 2,2% de gordura). Inicialmente, eles passaram por uma avaliação antropométrica seguida de um teste de 1RM de familiarização no exercício de desenvolvimento, que foi repetido após 48h. A repetibilidade do teste de 1RM foi testada pelo Wilcoxon matched paired test. Finalmente, a carga de 1RM foi modelada em função das variáveis antropométricas por regressão linear múltipla (forward stepwise) usando como critério de corte das variáveis independentes Dr2 < 0,01. A confiabilidade dos modelos foi expressa pela análise de Bland e Altman. Adotou-se em todos os testes a = 0,05. Não se registraram diferenças entre teste e reteste, resultando em 44,6 ± 13,2kg e 12,2 ± 3,2kg nos indivíduos do sexo masculino (SM) e feminino (SF), respectivamente. Além das variáveis antropométricas, incluiu-se aos modelos o tempo de experiência em treinamento de força. No SM, o modelo resultou em 84% da variância explicada, com erro padrão equivalente a 12%. Por outro lado, no SF, a capacidade preditiva do modelo obtido foi mais fraca, resultando em 56% da variância explicada e erro padrão equivalente a 20%. Em conclusão, os modelos obtidos mostraram adequada confiabilidade, de forma que podem ser utilizados como ferramentas para predição da carga de 1RM. ... Within this context, it is a consensus that the grounding for the exercise prescription in counter-resistance training (CRT) is established through the relation between the 1RM percentage and the number of repetitions (1) . On the other hand, previous studies have shown that several factors -such as: physical conditioning level (2) ; muscular group (3) ; sleep routine (4) ; diet (5) ; chronobiological rhythm (6) ; motivation (7) ; menstrual cycle (8) and muscular fatigue (9) -effectively interfere in such relation, resulting in distinct intensities for a given number of repetitions. ... Article Full-text available The goal of the present study was to develop an equation for predicting the workload of one maximal repetition (1RM) in wom- en and men, based exclusively on anthropometrical characteris- tics. Forty-four low-risk and experienced in strength training young subjects, being 22 male (23 ± 4 years, 76.6 ± 12.7 kg, 173.9 ± 5.5 cm, 11 ± 4.5% of body fat) and 22 female (22 ± 4 years, 54 ± 6.0 kg, 161 ± 5.8 cm, 18 ± 2.2% of body fat) volunteered for this study. All subjects were submitted to an anthropometrical evaluation fol- lowed by a 1RM familiarization test (shoulder press), which was repeated after 48 h. The repeatability was tested using Wilcoxon Matched paired test. Finally, the 1RM workload was modeled in relation to the anthropometrical variables through multiple linear regression (forward stepwise) using as cutoff criteria for the inde- pendent variables ∆r 2 < 0.01. The models reliability was expressed by the Bland and Altman analysis. All tests assumed α = 0.05. No significant differences were recorded between the two tests, re- sulting 44.6 ± 13.2 kg and 12.2 ± 3.2 kg, for male (MS) and female (FS) subjects respectively. The time of practice in strength training was also included in the models. The model resulted in 84% of explained variance and a standard error of 12% for the MS. On the other hand, for the FS the predictive capacity was weaker than for = the MS, resulting in 56% of the explained variance and a stan- dard error of 20%. In conclusion, the obtained models showed acceptable reliability so that they can be currently used as a tool for predicting the 1RM workload. ... An important consideration for PL is that official weigh-in time for most drug-tested federations occur ≤2 h prior to competition (Ferland & Comtois, 2019), compared with 24 h to 36 h in combat sports (Artioli et al., 2016;Reale et al., 2017). With such discrepancies of weigh-in timing and their relationship to muscle recovery, nutrition and physiological adaptations, fluid and carbohydrate stores may be compromised in PL athletes (Nolan et al., 2020), particularly when considering hypohydration and low muscle glycogen can negatively impact strength outcomes (Leveritt & Abernethy, 1999;Schoffstall, Branch, Leutholtz & Swain, 2001;Slater et al., 2019). With this is mind, the aim of the study was to assess the frequency with which certain RWL methods are adopted by male and female PL athletes in the United Kingdom (UK) during competition preparation. ... Article Previous research in Powerlifting (PL) has qualitatively investigated rapid weight-loss (RWL) in PL athletes and body image, however limited research exists in quantifying such methods adopted in PL. This study aimed to assess the frequency of RWL methods are adopted by male and female PL athletes in the United Kingdom (UK) during competition preparation. A total of n = 37 (n = 19 female, n = 18 male) competitive powerlifters completed an anonymous online questionnaire assessing RWL methods. A Chi-square cross tabulation was utilised to identify any significant differences between independent and dependent variables. Multiple regression analyses were then conducted to assess the contribution of biological sex and PL category on RWL methods. Commonly reported methods of weight loss were gradual dieting (49%), fluid restriction (46%), and water loading (51%). Differences between PL category (Junior, Open, Masters One) and adopting RWL were observed (X 2 =4.220, p <0.05). PL category was a predictor of undertaking RWL (R 2 adj = 0.160, F (2, 34) = 4.429, p ≤ 0.05), whilst biological sex was a predictor of timeframe of undertaking RWL (R 2 adj = 0.123, F (2, 34) = 3.534, p ≤ 0.05). RWL strategies are adopted by PL athletes in order to make weight for competition. Despite known effects of RWL on strength performance, limited research currently exists on these strategies specifically within PL, therefore this may be a consideration for future research. Practitioners working with PL athletes may wish to consider appropriate nutrition and weight loss strategies in preparation for PL competitions. ... Many studies have examined low carbohydrate dietary conditions as they relate to aerobic and high-intensity endurance exercise. Few have investigated the effect of a low carbohydrate condition on acute strength (1,2). Previous results have been mixed and it is unclear if a low carbohydrate diet is a significant detriment to moderate intensity resistance training. ... ... The largest reductions in glycogen are seen with high repetitions with moderate load training [40], an effect that mainly occurs in type II fibers [39]. It has been demonstrated that a reduction of muscle glycogen affects both isokinetic torque [29] and isoinertial resistance exercise capacity negatively [42]. However, this effect is not always evident [43] and is likely to be affected by the protocol used to induce glycogen depletion [44]. ... Article Full-text available It is well established that glycogen depletion affects endurance exercise performance negatively. Moreover, numerous studies have demonstrated that post-exercise carbohydrate ingestion improves exercise recovery by increasing glycogen resynthesis. However, recent research into the effects of glycogen availability sheds new light on the role of the widely accepted energy source for adenosine triphosphate (ATP) resynthesis during endurance exercise. Indeed, several studies showed that endurance training with low glycogen availability leads to similar and sometimes even better adaptations and performance compared to performing endurance training sessions with replenished glycogen stores. In the case of resistance exercise, a few studies have been performed on the role of glycogen availability on the early post-exercise anabolic response. However, the effects of low glycogen availability on phenotypic adaptations and performance following prolonged resistance exercise remains unclear to date. This review summarizes the current knowledge about the effects of glycogen availability on skeletal muscle adaptations for both endurance and resistance exercise. Furthermore, it describes the role of glycogen availability when both exercise modes are performed concurrently. ... Research shows that approximately 80% of ATP used in a typical hypertrophyoriented resistance exercise session is obtained from glycolysis (Lambert and Flynn, 2002;MacDougall et al., 1999;Pascoe et al., 1993). Leveritt and Abernethy (1999) found that reductions in muscle glycogen stores significantly impaired performance in resistance exercise. Nevertheless, although dietary carbohydrate has been shown to enhance exercise performance, only moderate amounts appear to be required to achieve beneficial effects. ... Article Full-text available The purpose of this study was to determine the effects of different amounts of energy intake in combination with progressive resistance training on muscle mass and body fat in bodybuilders. Eleven male bodybuilders (26.8 ± 2.3 years, 90.1 ± 9.7 kg, and 176.9 ± 7.1 cm) were randomly assigned into one of two groups: a group that ingested higher amounts of energy (G1, 67.5 ± 1.7 kcal/kg/d, n = 6), and a group that ingested moderate amounts of energy (G2, 50.1 ± 0.51 kcal/kg/d, n = 5). Both groups performed resistance training 6 days per week over a 4-week study period. Measures of body composition were assessed before and after the intervention period. For body fat, only the G1 presented significant changes from pre- to post-training (G1 = +7.4% vs. G2 = +0.8%). For muscle mass, both groups showed significant increases after the intervention period, with G1 presenting a greater increase compared to G2 (G1 = +2.7% vs. G2 = +1.1%). Results suggest that greater energy intake in combination with resistance training induces greater increases in both muscle mass and body fat in competitive male bodybuilders. ... Blood lactate concentration increased more than 3-fold in both groups; a 2.5-fold higher increase than that found by Chappell et al. [34]. This difference may be attributed to the energy restriction employed in our study, and is consistent with the claim that lower energy availability alters the metabolic response to exercise without detrimental effects in performance [35]. Furthermore, the effect size values for lactate levels suggest that carbohydrate refeed had a more pronounced attenuation after GVT in the SER condition, possibly due to the decrease in the stimulation of the glycolytic pathway. ... Article Full-text available Bodybuilding is a sport in which competitors’ physiques are judged on their muscular size, symmetry, and leanness, as displayed in a number of different poses. In the pre-competitive period, bodybuilders attempt to reduce body fat stores as much as possible while maintaining fat-free mass (FFM). This is achieved via a sustained negative energy balance, generally induced by a combination of decreased energy intake and increased energy expenditure. This study aimed to assess the ability of bodybuilders to resist fatigue during resistance exercise based German Volume Training (GVT), as well as the affective response after carbohydrate refeed following four weeks of moderate or severe energy restriction. Eleven male bodybuilders (28.4 ± 2.3 years old) with experience in competitions were randomized into two groups: Moderate Energy Restriction (MER; n=6) or Severe Energy Restriction (SER; n=5). On the 2nd day (during energy restriction) and 7th day (during refeed) of the fourth week, both groups completed two leg press protocols involving the GVT method. After the first and last workout protocol subjects were assessed for muscle soreness using the visual-analog scale (VAS), rating of perceived exertion (RPE), affective response, lactate, and creatine kinase. Anthropometric analysis indicated that a reduction of 3.7 and 3.2% in body mass corresponded to a loss of 16.0 and 17.6% of fat mass for the MER and SER groups, respectively, with both groups maintaining FFM. Blood CK and VAS values were reduced only in SER. Our results suggest that a carbohydrate refeed may help to attenuate the perception of muscle soreness and maintain exercise performance, especially when severe energy restriction is combined with an intense training protocol such as GVT. ... Consequently, the elevation of endogenous glycogen stores through pre-exercise feeding might delay fatigue and enhance performance (11) . Indeed, commencing a bout of resistance exercise with reduced glycogen stores has been shown to reduce performance by some (12)(13)(14) , but not all (15) studies. Similarly, we recently reported (16) that compared to a no breakfast trial, an ecologically valid breakfast (containing 1.5 g carbohydrate/kg body mass) increased performance in 4 sets of back squat and 4 sets of bench press 2 h later. ... Article Full-text available Given the common view that pre-exercise nutrition/breakfast is important for performance, the present study investigated whether breakfast influences resistance exercise performance via a physiological or psychological effect. Twenty-two resistance trained, breakfast-consuming men completed three experimental trials, consuming water-only (WAT), or semi-solid breakfasts containing 0 g/kg (PLA) or 1.5 g/kg (CHO) maltodextrin. PLA and CHO meals contained xanthan gum and low-energy flavouring (~29 kcal) and subjects were told both ‘contained energy’. Two hours post-meal, subjects completed 4 sets of back squat and bench press to failure at 90% 10 repetition maximum. Blood samples were taken pre-meal, 45 min and 105 min post-meal to measure serum/plasma glucose, insulin, ghrelin, GLP-1 and PYY concentrations. Subjective hunger/fullness were also measured. Total back squat repetitions were greater in CHO (44 (SD 10) repetitions) and PLA (43 ± 10 repetitions) than WAT (38 (SD 10) repetitions; P < 0.001). Total bench press repetitions were similar between trials (WAT 37 (SD 7) repetitions; CHO 39 ± 7 repetitions; PLA 38 (SD 7) repetitions; P = 0.130). Performance was similar between CHO and PLA trials. Hunger was suppressed and fullness increased similarly in PLA and CHO, relative to WAT ( P < 0.001). During CHO, plasma glucose was elevated at 45 min ( P < 0.05), whilst serum insulin was elevated ( P < 0.05) and plasma ghrelin supressed at 45 and 105 min ( P < 0.05). These results suggest that breakfast/pre-exercise nutrition enhances resistance exercise performance via a psychological effect, although a potential mediating role of hunger cannot be discounted. ... The acceptable macronutrient distribution range (AMDR) for carbohydrates is 45-65% of daily calories (24). Given that the previous literature has demonstrated that a single bout of resistance training can result in a significant drop in muscle glycogen (53) and low glycogen levels have been associated with increased feelings of fatigue, perceived exertion during exercise (43), and decreased athletic performance capabilities; (28,30,38) athletes may wish to avoid lower levels of carbohydrate ingestion. As such, to maintain and/or replenish muscle glycogen, 3-5 g of carbohydrate$kg body mass 21 may be recommended for strength athletes (47). ...
... Hence, the low-carbohydrate availability during bulking noted by subjects in the current study should be considered counterproductive to achieving the goals of this phase. This is of particular concern considering that athletes may include aerobic exercise as part of their daily training protocol (15), which in turn could promote a greater decrease in muscle glycogen and thus further compromise resistance training performance (24). It is difficult to reconcile discrepancies between the athletes' perception of their intended behaviors vs. their actual nutritional practices relating to carbohydrate intake. ...
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Lenzi, JL, Teixeira, EL, de Jesus, G, Schoenfeld, BJ, and de Salles Painelli, V. Dietary strategies of modern bodybuilders during different phases of the competitive cycle. J Strength Cond Res 35(9): 2546-2551, 2021-Bodybuilders have used a wide array of nutritional strategies over the years. However, most information on the topic is anecdotal, with limited research about the nutritional habits of modern bodybuilders, especially those from new categories. Accordingly, we sought to compare the dietary routines of bodybuilders from the Men's Physique category during "bulking" and "cutting" phases, while attempting to identify the rationale underpinning these practices. Sixteen experienced male bodybuilding competitors were interviewed during bulking (10-12 weeks before competition) and cutting (1 week before competition) phases, wherein we quantified energy and nutrient intake and determined their rationale and sources of education. Dietary analysis revealed a low carbohydrate intake during bulking, with a further decrease (at p < 0.05) during cutting. A similar decrease (at p < 0.05) from bulking to cutting was shown in the intake of most macronutrients and micronutrients, although intake of protein and almost all the micronutrients was well above the recommendation throughout the competitive cycle. Most of the consumed supplements can be deemed unnecessary or without scientific support. Most athletes reported self-managing their diet and supplement program, without the assistance of nutrition professionals. As such, some of their professed nutritional habits obtained during interviewers were not consistent with the food diary information. Although some dietary strategies used by bodybuilders in the Men's Physique category are consistent with evidence-based practice, most can be considered extreme and lack scientific support. The source of education may help to explain their decision-making.
... This is supported by cy of amino acid utilisation. However, because of most[19][20][21][22][23]but not all available literature.[24]the large thermic effect of protein, we suggest that MacDougall et al.[25]had individuals perform the protein intake should be 25–30% of total energy 6–17 1-minute bouts on a cycle ergometer at 140% intake which under most, if not all circumstances, of maximum oxygen consumption. Muscle glycowill be >0.8g of protein/kg/day. ...
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The objective of this study was to examine the muscle metabolic changes occurring during intense and prolonged, heavy-resistance exercise. Muscle biopsies were obtained from the vastus lateralis of 9 strength trained athletes before and 30 s after an exercise regimen comprising 5 sets each of front squats, back squats, leg presses and knee extensions using barbell or variable resistance machines. Each set was executed until muscle failure, which occurred within 6-12 muscle contractions. The exercise: rest ratio was approximately 1:2 and the total performance time was 30 min. Concentrations of adenosine triphosphate (ATP), creatine phosphate (CP), creatine, glycogen, glucose, glucose-6-phosphate (G-6-P), alpha-glycerophosphate (alpha-G-P) and lactate were determined on freeze-dried tissue samples using fluorometric assays. Blood samples were analyzed for lactate and glucose. The exercise produced significant reductions in ATP (p less than 0.01) and CP (p less than 0.001), while alpha-G-P more than doubled (p less than 0.05), glucose increased tenfold (p less than 0.001) and G-6-P fourfold (p less than 0.001). Muscle lactate concentration at cessation of exercise averaged 17.3 mmol X kg-1 w. w. Glycogen concentration decreased (p less than 0.001) from 160 to 118 mmol X kg-1 w. w. It is concluded that high intensity, heavy resistance exercise is associated with a high rate of energy utilization through phosphagen breakdown and activation of glycogenolysis.
The effect of altering muscle glycogen on the ability of skeletal muscle to generate voluntary and electrically evoked isometric force following prolonged exercise has been investigated in five healthy male subjects. Measurements from the triceps surae were made at rest, and before and after prolonged exercise (uphill walking) at approximately 75%$$\dot V_{{\text{O}}_{\text{2}} {\text{ max}}}$$ in low muscle glycogen (low CHO) and high muscle glycogen (high CHO) conditions. The results showed that before exercise there was no change in maximal twitch tension ($${\text{P}}_{{\text{t}}_{\text{o}} }$$), maximal tetanic tension at frequencies of 10 (Po10), 20 (Po20) and 50 Hz (Po50), and maximal voluntary contraction (MVC) in low and high CHO compared with normal. The loss of force during a 2 min electrically evoked “fatigue test” at rest was found to be higher (p<0.05) in low CHO and lower (p<0.05) in high CHO than normal. Following the prolonged exercise, muscle weakness was produced in both low and high CHO conditions, but was found to be significantly greater in the low CHO condition for the measurements of Po10 (p<0.01), Po20 (p<0.05) and MVC (p<0.05). It is concluded that changes in muscle glycogen alone do not alter the isometric force generating capacity of human muscle, but when combined with prolonged exercise low muscle glycogen enhances exercise-induced muscle weakness.
The purpose of this study was to determine how individuals adapt to a combination of strength and endurance training as compared to the adaptations produced by either strength or endurance training separately. There were three exercise groups: a strength group (S) that exercised 30--40 min . day-1, 5 days . week-1, and endurance group (E) that exercised 40 min . day-1, 6 days . week-1; and an S and E group that performed the same daily exercise regimens as the S and E groups. After 10 weeks of training, VO2max increased approx. 25% when measured during bicycle exercise and 20% when measured during treadmill exercise in both E, and S and E groups. No increase in VO2max was observed in the S group. There was a consistent rate of development of leg-strength by the S group throughout the training, whereas the E group did not show any appreciable gains in strength. The rate of strength improvement by the S and E group was similar to the S group for the first 7 weeks of training, but subsequently leveled off and declined during the 9th and 10th weeks. These findings demonstrate that simultaneously training for S and E will result in a reduced capacity to develop strength, but will not affect the magnitude of increase in VO2max.
Two groups of male subjects were studied to examine the effects of different exercise protocols on performance of an isokinetic, short-time strength test, the performance of which is related to fast twitch (FT) muscle fiber recruitment. The laboratory group (LG) (n = 10) cycled (30 min, 70% VO2 max), ran (75 min), and performed repeated bouts of "sprint" cycling and rapid, maximal contractions of the quadriceps. The marathon group (MG) (n = 7) participated in and completed Stockholm's Marathon 1979. A strength test was performed before and within 1-2 h after completion of the group exercise protocol. The m. vastus lateralis was biopsied and muscle fibers classified as slow twitch (ST) or FT. After periodic acid-Schiff staining fibers were qualitatively classified as to glycogen content. In LG significant glycogen depletion occurred in both fiber types and in MG predominantly ST fibers were exhausted of glycogen after the exercise protocol. The glycogen exhaustion from both fiber types in LG was associated with impaired maximal muscular strength produced during a single dynamic contraction, as well as with reduced muscle fatigue patterns. When glycogen exhaustion was induced in ST muscle fibers only in the MG, no impairment was observed for maximal muscular strength but fatigue during 50 consecutive contractions was significantly increased.