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Protein Amount, Quality and Distribution in Active Older Adults and Its Effects on Outcomes of Fat Free Mass, Skeletal Muscle Strength and Power

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Abstract

This study aimed to investigate the associations of habitual protein intake in a cohort of active older adults including: daily relative protein intake, distribution of protein intake across main meals, and number of meals providing ≥0.4 g/kg body mass (BM) on outcomes of fat free mass (FFM), leg power, leg strength, and handgrip strength (HGS). This was a cross-sectional study (2018-2020) where data were obtained and analysed from n= 53 active older adults (≥50 yrs; ≥90 min/week of self-reported physical activity). Daily absolute (g) and relative protein (g/kgBM/day) intake, absolute and relative protein intake per meal, the number of meals that provided 0.4 g/kgBM, and the protein intake distribution were calculated for each participant through a 3-day food diary assessment and analysis. Appendicular muscle mass index (ALM/ht 2 ; dual x-ray absorptiometry), leg strength (1-repetition maximum using leg press), leg power (force plate countermovement jump) and HGS (dynamometer) were assessed. An independent t-test was used to test statistical significance between groups based on protein intake. Pearson's correlation determined differences between protein intakes with lean muscle mass and strength outcomes. Results: Daily protein intake was (mean ± SD) 1.4 ± 0.4 g/kg BM/day, with the coefficient of variation of main meals calculated at 0.46 (0.41-0.51), and the average number of meals that provided ≥0.4g/kgBM was 1.1 ± 0.8 meals. There was a moderate but significant positive correlation between number of meals per day providing ≥0.4g/kgBM, and number and leg press (r = .301, p< .05), significant for males (r= .591, p= .029), but not females (r=.262, p= .196). There was also a small significant association between the number of total protein and dairy serves per day and leg strength ((r= .290, p= .035; r= .372, p= .006, respectively). No significant correlations were observed for outcomes of HGS or FFM and any of the dietary protein measures. Conclusion: In a cohort of active older adults who achieve greater protein intakes than the current recommendations, a minimum of 1 meal containing ≥0.4 g/kg BM of protein and higher intakes of dairy based foods may be required to achieve favourable outcomes in leg strength.

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... The present cross-sectional study was conducted on 268 adults (117 males and 151 females) aged 18-70 living in Tehran, Iran. To determine the sample size, we have considered the correlation of protein intake with muscle handgrip as outcome variable (Huschtscha et al., 2021). We calculated the sample size based on correlation coefficients ≥0.3 at the 5% significance level and with 80% power. ...
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To determine whether preservation of physical function with aging may be partially met through modification in dietary protein intake. Prospective cohort study. Women's Health Initiative (WHI) Clinical Trials (CT) and Observational Study (OS) conducted at 40 clinical centers. Women aged 50 to 79 (N = 134,961) with dietary data and one or more physical function measures. Physical function was assessed using the short-form RAND-36 at baseline and annually beginning in 2005 for all WHI participants and at closeout for CT participants (average ~7 years after baseline). In a subset of 5,346 participants, physical performance measures (grip strength, number of chair stands in 15 seconds, and timed 6-m walk) were assessed at baseline and Years 1, 3, and 6. Calibrated energy and protein intake were derived from regression equations using baseline food frequency questionnaire data collected on the entire cohort and doubly labeled water and 24-hour urinary nitrogen collected from a representative sample as reference measures. Associations between calibrated protein intake and each of the physical function measures were assessed using generalized estimating equations. Calibrated protein intake ranged from 6.6% to 22.3% energy. Higher calibrated protein intake at baseline was associated with higher self-reported physical function (quintile (Q)5, 85.6, 95% confidence interval (CI) = 81.9-87.5; Q1, 75.4, 95% CI = 73.2-78.5, Ptrend = .002) and a slower rate of functional decline (annualized change: Q5, -0.47, 95% CI = -0.63 to -0.39; Q1, -0.98, 95% CI = -1.18 to -0.75, Ptrend = .02). Women with higher calibrated protein intake also had greater grip strength at baseline (Q5, 24.7 kg, 95% CI = 24.3-25.2 kg; Q1, 24.1 kg, 95% CI = 23.6-24.5 kg, Ptrend = .04) and slower declines in grip strength (annualized change: Q5, -0.45 kg, 95% CI = -0.39 to -0.63 kg; Q1, -0.59 kg, 95% CI = -0.50 to -0.66 kg, Ptrend = .03). Women with higher calibrated protein intake also completed more chair stands at baseline (Q5, 7.11, 95% CI = 6.91-7.26; Q1, 6.61, 95% CI = 6.46-6.76, Ptrend = .002). Higher calibrated protein intake is associated with better physical function and performance and slower rates of decline in postmenopausal women.
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Both low dietary protein intake and inadequate distribution of protein over the three mealtimes have been reported in older Caucasian adults, but the association between protein intake at each meal and muscle mass has not been studied. The purpose of this study was to evaluate dietary protein intake and distribution by mealtimes, and to explore their association with appendicular skeletal muscle mass in apparently healthy older adults. This was a cross-sectional pilot study that included 78 people over the age of 60 years. Caloric and protein intake were estimated on the basis of three nonconsecutive 24-hour diet recalls and appendicular skeletal muscle mass by dual-energy X-ray absorptiometry. Men consumed 13.4 g of protein/day more than women (P < 0.05). The estimated value of dietary protein intake was 0.9 g/kg/day. In this sample, 28% of subjects did not cover 100% of the dietary reference intake for protein. Lower consumption of dietary protein was found at breakfast and dinnertime compared with the recommended amount of 25-30 g (P < 0.05). Also, the study observed that appendicular skeletal muscle mass in men and women who consumed <25 g of protein at each mealtime was different from that found in the group that consumed >25 g of protein at one, two, or three mealtimes. While protein intake was higher than current recommendations, it failed to achieve the values reported as necessary to prevent sarcopenia. In addition, there was under-consumption of protein per mealtime, especially at breakfast and dinner.
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To preserve muscle mass and therefore limit the risk of disability in older adults protein intake is seen as important factor. Besides the amount of protein, its distribution over the day is thought to affect protein anabolism. This cross-sectional study investigates the association between the amount and distribution of protein intake and frailty in older adults. In 194 community-dwelling seniors (>=75 years) amount of protein intake and its distribution over the day (morning, noon, evening) were assessed using a food frequency questionnaire. Unevenness of protein distribution was calculated as coefficient of variation (CV). Frailty was defined as the presence of at least three, pre-frailty as the presence of one or two of the following criteria: weight loss, exhaustion, low physical activity, low handgrip strength and slow walking speed. 15.4% of the participants were frail, 40.5% were pre-frail. Median (min.-max.) daily protein intake was 77.5 (38.5-131.5) g, 1.07 (0.58-2.27) g/kg body weight (BW) and 15.9 (11.2-21.8) % of energy intake without significant differences between the frailty groups. The risk of frailty did not differ significantly between participants in the higher compared to the lowest quartile of protein intake. Frail participants consumed significantly less protein in the morning (11.9 vs. 14.9 vs. 17.4%, p = 0,007), but more at noon (61.4 vs. 60.8 vs. 55.3%, p = 0.024) than pre-frail and non-frail. The median (min.-max.) CV of protein distribution was highest in frail (0.76 (0.18-1.33)) compared to pre-frail (0.74 (0.07-1.29)) and non-frail (0.68 (0.15-1.24)) subjects (p = 0.024). In this sample of healthy older persons, amount of protein intake was not associated with frailty, but distribution of protein intake was significantly different between frail, pre-frail and non-frail participants. More clinical studies are needed to further clarify the relation between protein intake and frailty.
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New evidence shows that older adults need more dietary protein than do younger adults to support good health, promote recovery from illness, and maintain functionality. Older people need to make up for age-related changes in protein metabolism, such as high splanchnic extraction and declining anabolic responses to ingested protein. They also need more protein to offset inflammatory and catabolic conditions associated with chronic and acute diseases that occur commonly with aging. With the goal of developing updated, evidence-based recommendations for optimal protein intake by older people, the European Union Geriatric Medicine Society (EUGMS), in cooperation with other scientific organizations, appointed an international study group to review dietary protein needs with aging (PROT-AGE Study Group). To help older people (>65 years) maintain and regain lean body mass and function, the PROT-AGE study group recommends average daily intake at least in the range of 1.0 to 1.2 g protein per kilogram of body weight per day. Both endurance- and resistance-type exercises are recommended at individualized levels that are safe and tolerated, and higher protein intake (ie, ≥1.2 g/kg body weight/d) is advised for those who are exercising and otherwise active. Most older adults who have acute or chronic diseases need even more dietary protein (ie, 1.2-1.5 g/kg body weight/d). Older people with severe kidney disease (ie, estimated GFR <30 mL/min/1.73m(2)), but who are not on dialysis, are an exception to this rule; these individuals may need to limit protein intake. Protein quality, timing of ingestion, and intake of other nutritional supplements may be relevant, but evidence is not yet sufficient to support specific recommendations. Older people are vulnerable to losses in physical function capacity, and such losses predict loss of independence, falls, and even mortality. Thus, future studies aimed at pinpointing optimal protein intake in specific populations of older people need to include measures of physical function.
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ABSTRACT: Age-related muscle wasting (sarcopenia) is accompanied by a loss of strength which can compromise the functional abilities of the elderly. Muscle proteins are in a dynamic equilibrium between their respective rates of synthesis and breakdown. It has been suggested that age-related sarcopenia is due to: i) elevated basal-fasted rates of muscle protein breakdown, ii) a reduction in basal muscle protein synthesis (MPS), or iii) a combination of the two factors. However, basal rates of muscle protein synthesis and breakdown are unchanged with advancing healthy age. Instead, it appears that the muscles of the elderly are resistant to normally robust anabolic stimuli such as amino acids and resistance exercise. Ageing muscle is less sensitive to lower doses of amino acids than the young and may require higher quantities of protein to acutely stimulate equivalent muscle protein synthesis above rest and accrue muscle proteins. With regard to dietary protein recommendations, emerging evidence suggests that the elderly may need to distribute protein intake evenly throughout the day, so as to promote an optimal per meal stimulation of MPS. The branched-chain amino acid leucine is thought to play a central role in mediating mRNA translation for MPS, and the elderly should ensure sufficient leucine is provided with dietary protein intake. With regards to physical activity, lower, than previously realized, intensity high-volume resistance exercise can stimulate a robust muscle protein synthetic response similar to traditional high-intensity low volume training, which may be beneficial for older adults. Resistance exercise combined with amino acid ingestion elicits the greatest anabolic response and may assist elderly in producing a 'youthful' muscle protein synthetic response provided sufficient protein is ingested following exercise.
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the European Working Group on Sarcopenia in Older People has developed a clinical definition of sarcopenia based on low muscle mass and reduced muscle function (strength or performance). Grip strength is recommended as a good simple measure of muscle strength when 'measured in standard conditions'. However, standard conditions remain to be defined. a literature search was conducted to review articles describing the measurement of grip strength listed in Medline, Web of Science and Cochrane Library databases up to 31 December 2009. there is wide variability in the choice of equipment and protocol for measuring grip strength. The Jamar hand dynamometer is the most widely used instrument with established test-retest, inter-rater and intra-rater reliability. However, there is considerable variation in how it is used and studies often provide insufficient information on the protocol followed making comparisons difficult. There is evidence that variation in approach can affect the values recorded. Furthermore, reported summary measures of grip strength vary widely including maximum or mean value, from one, two or three attempts, with either hand or the dominant hand alone. there is considerable variation in current methods of assessing grip strength which makes comparison between studies difficult. A standardised method would enable more consistent measurement of grip strength and better assessment of sarcopenia. Our approach is described.
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Adequate dietary protein intake is required to postpone and treat sarcopenia in elderly people. Insight into dietary protein intake in this heterogeneous population segment is needed to locate dietary inadequacies and to identify target populations and feeding strategies for dietary interventions. Therefore, we assessed dietary protein intake, distribution of protein intake throughout the day, and the use of protein-containing food sources in community-dwelling, frail, and institutionalized elderly people in the Netherlands. Secondary analyses were carried out using dietary data collected from studies among community-dwelling, frail, and institutionalized elderly people to evaluate protein intake characteristics. Dietary protein intake averaged 1.1 ± 0.3 g/kg-bw/day in community-dwelling, 1.0 ± 0.3 g/kg-bw/day in frail, and 0.8 ± 0.3 g/kg-bw/day in institutionalized elderly men. Similar protein intakes were found in women. Ten percent of the community-dwelling and frail elderly and 35% of the institutionalized elderly people showed a protein intake below the estimated average requirement (0.7 g/kg-bw/day). Protein intake was particularly low at breakfast in community-dwelling (10 ± 10 g), frail (8 ± 5 g), and institutionalized elderly people (12 ± 6 g) with bread and dairy products as predominant protein sources. Whereas daily protein intake is generally well above the recommended dietary allowance in community-dwelling and frail elderly people, a significant proportion of institutionalized elderly showed an intake below the current protein requirement, making them an important target population for dietary interventions. Particularly at breakfast, there is scope for improving protein intake.
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Strength training has become one of the most popular physical activities for increasing characteristics such as absolute muscular strength, endurance, hypertrophy and muscular power. For efficient, safe and effective training, it is of utmost importance to understand the interaction among training variables, which might include the intensity, number of sets, rest interval between sets, exercise modality and velocity of muscle action. Research has indicated that the rest interval between sets is an important variable that affects both acute responses and chronic adaptations to resistance exercise programmes. The purpose of this review is to analyse and discuss the rest interval between sets for targeting specific training outcomes (e.g. absolute muscular strength, endurance, hypertrophy and muscular power). The Scielo, Science Citation Index, National Library of Medicine, MEDLINE, Scopus, Sport Discus and CINAHL databases were used to locate previous original scientific investigations. The 35 studies reviewed examined both acute responses and chronic adaptations, with rest interval length as the experimental variable. In terms of acute responses, a key finding was that when training with loads between 50% and 90% of one repetition maximum, 3-5 minutes' rest between sets allowed for greater repetitions over multiple sets. Furthermore, in terms of chronic adaptations, resting 3-5 minutes between sets produced greater increases in absolute strength, due to higher intensities and volumes of training. Similarly, higher levels of muscular power were demonstrated over multiple sets with 3 or 5 minutes versus 1 minute of rest between sets. Conversely, some experiments have demonstrated that when testing maximal strength, 1-minute rest intervals might be sufficient between repeated attempts; however, from a psychological and physiological standpoint, the inclusion of 3- to 5-minute rest intervals might be safer and more reliable. When the training goal is muscular hypertrophy, the combination of moderate-intensity sets with short rest intervals of 30-60 seconds might be most effective due to greater acute levels of growth hormone during such workouts. Finally, the research on rest interval length in relation to chronic muscular endurance adaptations is less clear. Training with short rest intervals (e.g. 20 seconds to 1 minute) resulted in higher repetition velocities during repeated submaximal muscle actions and also greater total torque during a high-intensity cycle test. Both of these findings indirectly demonstrated the benefits of utilizing short rest intervals for gains in muscular endurance. In summary, the rest interval between sets is an important variable that should receive more attention in resistance exercise prescription. When prescribed appropriately with other important prescriptive variables (i.e. volume and intensity), the amount of rest between sets can influence the efficiency, safety and ultimate effectiveness of a strength training programme.
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Aging is associated with reductions in muscle mass and strength, so-called sarcopenia, and is generally characterized using muscle mass index (MMI = FFM (kg)/height (m)2). It is believed that adequate nutrition especially regarding protein intake, can delay this progression and enhance the quality of life of elders. We examined whether the predominant source of protein consumed (animal or vegetal) by older women was associated with MMI. Thirty-eight healthy, normal weight, sedentary women, aged between 57-75 years (mean age: 66 +/- 5 years old), and taking no medication that could influence metabolism were recruited. Body composition was measured by dual-energy X-ray absorptiometry; muscle protein content was measured by the use of creatinine excretion. Physical activity metabolism was obtained by the use of accelerometry, and indirect calorimetry. Finally, protein intake was measured with a 3-day dietary record. Significant correlations were observed between MMI and body mass index, fat-free mass, muscle protein content, total protein intake, animal protein intake, fat mass, visceral fat and daily energy expenditure. However, a stepwise regression analysis showed animal protein intake to be the only independent predictor of MMI (r2=0.19; p=0.008). Our results suggest that protein intake, especially from animal sources, may be associated with a better preservation of MMI. However, more research is needed to confirm our results.
Article
Population ageing is a global phenomenon. It is regarded as a major cause of upward pressure on healthcare costs. One of the greatest threats to healthy, independent ageing is sarcopenia, the progressive loss of skeletal muscle mass and function with age. Physical inactivity and poor nutrition represent crucial and imminently modifiable risk factors for sarcopenia. Resistance exercise training is the most effective method for improving muscle mass and function in older adults. Evidence indicates that resistance training‐induced improvements in muscle mass, strength and function may be further augmented by certain nutrients and nutritional strategies. Ageing is associated with a reduction in the anabolic sensitivity of skeletal muscle to dietary protein ingestion and accumulating evidence indicates that older adults require protein intakes 50%–100% higher than the recommended daily allowance (0.8 g/kg/day) to preserve muscle mass and function. Protein quality, the pattern of protein intake over the day (i.e. per‐meal protein), specific amino acids (i.e. leucine) and other nutrients (i.e. vitamin D, long‐chain n‐3 polyunsaturated fatty acids) are also key considerations. From the personalised nutrition perspective, it is now acknowledged that individual responses to nutrition/exercise interventions are highly variable, despite equivalent compliance, thus highlighting the inadequacy of a ‘one‐size‐fits‐all’ approach. The application of personalised medicine to sarcopenia represents an exciting emerging field of research with the potential to dramatically improve patient outcomes. This approach makes use of recent developments in ‘omics’ technologies and aims to identify the factors (i.e. genes, key biomarkers, medical history, environment, lifestyle) that determine whether an individual is a higher or a lower responder to a particular intervention. This narrative review discusses current evidence regarding nutrition and exercise countermeasures for sarcopenia, with a specific emphasis on recent developments in personalised approaches.
Article
Background: It has been hypothesized that for older adults evenly distributing consumption of protein at 30-40 g per meal throughout the day may result in more favorable retention of lean mass and muscular strength. Such a thesis has not, to our knowledge, been tested outside of short-term studies or acute measures of muscle protein synthesis. Aims: To examine whether the number of times an individual consumed a minimum of 30 g of protein at a meal is associated with leg lean mass and knee extensor strength. Methods: Data from the 1999-2002 NHANES were used, with 1081 adults (50-85 y) constituting the analytic sample. A "multiple pass" 24-h dietary interview format was used to collect detailed information about the participants' dietary intake. Knee extensor strength was assessed objectively using the Kin Com MP dynamometer. Leg lean mass was estimated from whole-body dual-energy X-ray absorptiometry (DXA) scans. Results: Participants with 1 vs. 0 (βadjusted = 23.6, p = 0.002) and 2 vs. 0 (βadjusted = 51.1, p = 0.001) meals of ≥30 g protein/meal had greater strength and leg lean mass (1 vs. 0, βadjusted = 1160, p < 0.05 and 2 vs. 0, βadjusted = 2389, p < 0.05). The association of protein frequency with leg lean mass and strength plateaued at ∼45 g protein/meal for those consuming 2 vs. 0 meals above the evaluated protein/meal threshold. However, for those with only 1 meal at or above the evaluated threshold, the response plateaued at 30 g/meal. Leg lean mass mediated the relationship between protein frequency and strength, with the proportion of the total effect mediated being 64%. Conclusions: We found that more frequent consumption of meals containing between 30 and 45 g protein/meal produced the greatest association with leg lean mass and strength. Thus, the consumption of 1-2 daily meals with protein content from 30 to 45 g may be an important strategy for increasing and/or maintaining lean body mass and muscle strength with aging.
Article
Background: Dietary protein digestion and absorption is an important factor modulating muscle protein accretion. However, there are few data available on the effects of coingesting other macronutrients with protein on digestion and absorption kinetics and the subsequent muscle protein synthetic response. Objective: The objective of the study was to determine the impact of carbohydrate coingestion with protein on dietary protein digestion and absorption and muscle protein accretion in healthy young and older men. Design: Twenty-four healthy young (aged 21± 1 y, body mass index 21.8 ±0.5 kg/m(2)) and 25 older (aged 75 ± 1 y, body mass index 25.4 ± 0.6 kg/m(2)) men received a primed continuous L-[ring-(2)H5]-phenylalanine and L-[ring-3,5-(2)H2]-tyrosine infusion and ingested 20 g intrinsically L-[1-(13)C]-phenylalanine-labeled protein with (Pro+CHO) or without (Pro) 60 g carbohydrate. Plasma samples and muscle biopsies were collected in a postabsorptive and postprandial state. Results: Carbohydrate coingestion delayed the appearance of exogenous phenylalanine in the circulation (P = .001). Dietary protein-derived phenylalanine availability over the 5-hour postprandial period was lower in the older (62 ± 2%) when compared with the young subjects (74 ± 2%; P = .007), with no differences between conditions (P = .20). Carbohydrate coingestion did not modulate postprandial muscle protein synthesis rates (0.035 ± 0.003 vs 0.043 ± 0.004 and 0.033 ± 0.002 vs 0.035 ± 0.003%/h after Pro vs Pro+CHO in the young and older group, respectively). In accordance, no differences in muscle protein-bound L-[1-(13)C]-phenylalanine enrichments were observed between conditions (0.020 ± 0.002 vs 0.020 ± 0.002 and 0.019 ± 0.003 vs 0.022 ± 0.004 mole percent excess after Pro vs Pro+CHO in the young and older subjects, respectively). Conclusion: Carbohydrate coingestion with protein delays dietary protein digestion and absorption but does not modulate postprandial muscle protein accretion in healthy young or older men.
Article
Impaired muscle function has been demonstrated to be an important predictor of frailty and fracture in elderly people. The aim of this cross-sectional study was to evaluate the association of dairy intake with body composition and physical performance in 1,456 older women aged 70 to 85 years. Participants were assessed for dairy consumption (milk, yogurt, and cheese) by a validated food frequency questionnaire, body composition by dual-energy x-ray absorptiometry, and physical performance using hand-grip strength and Timed Up and Go tests. Data on falls in the previous 3 months were collected. Women were categorized according to tertiles of dairy intake: first tertile (≤1.5 servings/day), second tertile (1.5 to 2.2 servings/day), and third tertile (≥2.2 servings/day). Main outcomes were compared using analysis of covariance adjusting for confounding factors. Odds ratios for self-reported falls and risk of poor Timed Up and Go were obtained by using binary logistic regression. The mean age was 75.2±2.7 years and body mass index was 27.2±4.7. Compared with those in the first tertile of dairy intake, women in the third tertile had significantly greater whole body lean mass (34.4±0.3 vs 32.9±0.3 kg; P=0.001) and appendicular skeletal muscle mass (15.3±0.2 vs 14.5±0.2 kg; P=0.002), greater hand-grip strength (20.9±0.2 vs 20.0±0.2 kg; P=0.02), and 26% lower odds for a poor Timed Up and Go test (P=0.04); however, the difference in prevalence of falls in the previous 3 months was not statistically significant (10.3% vs 14.4%; P=0.08). Our results suggest an association of higher dairy intake with greater whole body lean mass and better physical performance in older women.
Article
Background: Protein ingestion after a single bout of resistance-type exercise stimulates net muscle protein accretion during acute postexercise recovery. Consequently, it is generally accepted that protein supplementation is required to maximize the adaptive response of the skeletal muscle to prolonged resistance-type exercise training. However, there is much discrepancy in the literature regarding the proposed benefits of protein supplementation during prolonged resistance-type exercise training in younger and older populations. Objective: The objective of the study was to define the efficacy of protein supplementation to augment the adaptive response of the skeletal muscle to prolonged resistance-type exercise training in younger and older populations. Design: A systematic review of interventional evidence was performed through the use of a random-effects meta-analysis model. Data from the outcome variables fat-free mass (FFM), fat mass, type I and II muscle fiber cross-sectional area, and 1 repetition maximum (1-RM) leg press strength were collected from randomized controlled trials (RCTs) investigating the effect of dietary protein supplementation during prolonged (>6 wk) resistance-type exercise training. Results: Data were included from 22 RCTs that included 680 subjects. Protein supplementation showed a positive effect for FFM (weighted mean difference: 0.69 kg; 95% CI: 0.47, 0.91 kg; P < 0.00001) and 1-RM leg press strength (weighted mean difference: 13.5 kg; 95% CI: 6.4, 20.7 kg; P < 0.005) compared with a placebo after prolonged resistance-type exercise training in younger and older subjects. Conclusion: Protein supplementation increases muscle mass and strength gains during prolonged resistance-type exercise training in both younger and older subjects.
Article
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.
Article
Ingestion of sufficient dietary protein is a fundamental prerequisite for muscle protein synthesis and maintenance of muscle mass and function. Elderly people are often at increased risk for protein-energy malnutrition, sarcopenia, and a diminished quality of life. This study sought to compare changes in muscle protein synthesis and anabolic efficiency in response to a single moderate serving (113 g; 220 kcal; 30 g protein) or large serving (340 g; 660 kcal; 90 g protein) of 90% lean beef. Venous blood and vastus lateralis muscle biopsy samples were obtained during a primed, constant infusion (0.08 mumol/kg/min) of L-[ring-(13)C(6)] phenylalanine in healthy young (n=17; 34+/-3 years) and elderly (n=17; 68+/-2 years) individuals. Mixed muscle fractional synthesis rate was calculated during a 3-hour postabsorptive period and for 5 hours after meal ingestion. Data were analyzed using a two-way repeated measures analysis of variance with Tukey's pairwise comparisons. A 113-g serving of lean beef increased muscle protein synthesis by approximately 50% in both young and older volunteers. Despite a threefold increase in protein and energy content, there was no further increase in protein synthesis after ingestion of 340 g lean beef in either age group. Ingestion of more than 30 g protein in a single meal does not further enhance the stimulation of muscle protein synthesis in young and elderly.
Article
The paper addresses the degree to which the attainment of the status as an elite athlete in different sports ameliorates the known age-related losses in skeletal muscle structure and function. The retrospective design, based on comparisons of published data on former elite and masters athletes and data on control subjects, assessed the degree to which the attainment of elite and masters athlete status ameliorated the known age-related changes in skeletal muscle structure and function. Institutional. Elite male athletes. Participation in selected individual and team sports. Strength, power, VO2max, and performance. For elite athletes in all sports, as for the general population, age-related muscle atrophy begins at about 50 years of age. Despite the loss of muscle mass, elite athletes who maintain an active lifestyle age gracefully with few health problems. Conversely, those who lapse into inactivity regress toward general population norms for fitness, weight control, and health problems. Elite athletes in the dual and team sports have careers that rarely extend into their 30s. Lifelong physical activity does not appear to have any impact on the loss in fiber number. The loss of fibers can be buffered to some degree by hypertrophy of fibers that remain. It is surprising that the performance of elite athletes in all sports appears to be impaired before the onset of the fiber loss. Even with major losses in physical capacity and muscle mass, the performance of elite and masters athletes is remarkable.
Article
To compare the reproducibility of the newly developed jumping mechanography with other physical tests. Study 1: Repeated testing with an interval of 2 weeks to assess the short-term repetition error. Study 2: Testing on 5 successive days to assess learning effects. Geriatric clinic, Esslingen, Germany. Study 1 had 36 subjects aged 24 to 88; Study 2 had 22 subjects aged 19 to 86. Locomotor competence in all subjects was assessed using the ability to walk unaided and to perform a tandem stand and tandem walk. The test battery consisted of timed up and go, freely chosen gait speed, maximum gait speed, chair-rising test, and maximum power in jumping mechanography. All subjects performed the jumping mechanography without major problems. Study 1: Of all tests, maximum power in jumping mechanography depicted the smallest intrasubject short-term error (3.6%), the largest intersubject coefficient of variation (45.4%), and the greatest test-retest correlation coefficient (r=0.99). Study 2: The only tests for which the learning effects were confined to the 1% range were the maximum gait speed test and the maximum power in jumping mechanography. Assessment of maximum power in jumping mechanography appears to have good test-retest reliability with negligible learning effects. Moreover, it results in a comparatively large intersubject variability, which makes it an interesting method in the assessment of aging effects in middle-aged to older subjects and patients.
Article
To counteract the debilitating progression of sarcopenia, a protein supplement should provide an energetically efficient anabolic stimulus. We quantified net muscle protein synthesis in healthy elderly individuals (65-79 yrs) following ingestion of an isocaloric intact whey protein supplement (WY; n=8) or an essential amino acid supplement (EAA; n=7). Femoral arterio-venous blood samples and vastus lateralis muscle biopsy samples were obtained during a primed, constant infusion of L-[ring-2H5]phenylalanine. Net phenylalanine uptake and mixed muscle fractional synthetic rate (FSR) were calculated during the post-absorptive period and for 3.5 h following ingestion of 15 g EAA or 15 g whey. After accounting for the residual increase in the intracellular phenylalanine pool, net post-prandial phenylalanine uptake was 53.4+/-9.7 mg phe leg-1 (EAA) and 21.7+/-4.6 mg phe leg-1 (WY), (P<0.05). Postabsorptive FSR values were 0.056+/-0.004% h-1 (EAA) and 0.049+/-0.006% h-1 (WY), (P>0.05). Both supplements stimulated FSR (P<0.05), but the increase was greatest in the EAA group with values of 0.088+/-0.011% h-1 (EAA) and 0.066+/-0.004% h-1 (WY), (P<0.05). While both EAA and WY supplements stimulated muscle protein synthesis, EAAs may provide a more energetically efficient nutritional supplement for elderly individuals.
Article
1. For animals of all ages, during activation of skeletal muscles and the subsequent contraction, the balance between the force developed by the muscle and the external load determines whether the muscle shortens, remains at fixed length (isometric) or is lengthened. With maximum activation, the force developed is least during shortening, intermediate when muscle length is fixed and greatest during lengthening contractions. During lengthening contractions, when force is high, muscles may be injured by the contractions. 2. 'Frailty' and 'failure to thrive' are most frequently observed in elderly, physically inactive people. A 'frail' person is defined as one of small stature, with muscles that are atrophied, weak and easily fatigued. The condition of 'failure to thrive' is typified by a lack of response to well-designed programmes of nutrition and physical activity. 3. With ageing, skeletal muscle atrophy in humans appears to be inevitable. A gradual loss of muscle fibres begins at approximately 50 years of age and continues such that by 80 years of age, approximately 50% of the fibres are lost from the limb muscles that have been studied. For both humans and rats, the observation that the timing and magnitude of the loss of motor units is similar to that for muscle fibres suggests that the mechanism responsible for the loss of fibres and the loss of whole motor units is the same. The degree of atrophy of the fibres that remain is largely dependent on the habitual level of physical activity of the individual. 4. 'Master athletes' maintain a high level of fitness throughout their lifespan. Even among master athletes, performance of marathon runners and weight lifters declines after approximately 40 years of age, with peak levels of performance decreased by approximately 50% by 80 years of age. The success of the master athletes and of previously sedentary elderly who undertake well-designed, carefully administered training programmes provide dramatic evidence that age-associated atrophy, weakness and fatigability can be slowed, but not halted.
Article
Dietary surveys suggest that many older, community-dwelling adults consume insufficient dietary protein, which may contribute to the age-related loss of lean mass (LM). The objective of the study was to determine the association between dietary protein and changes in total LM and nonbone appendicular LM (aLM) in older, community-dwelling men and women. Dietary protein intake was assessed by using an interviewer-administered 108-item food-frequency questionnaire in men and women aged 70-79 y who were participating in the Health, Aging, and Body Composition study (n=2066). Changes in LM and aLM over 3 y were measured by using dual-energy X-ray absorptiometry. The association between protein intake and 3-y changes in LM and aLM was examined by using multiple linear regression analysis adjusted for potential confounders. After adjustment for potential confounders, energy-adjusted protein intake was associated with 3-y changes in LM [beta (SE): 8.76 (3.00), P=0.004] and aLM [beta (SE): 5.31 (1.64), P=0.001]. Participants in the highest quintile of protein intake lost approximately 40% less LM and aLM than did those in the lowest quintile of protein intake (x+/-SE: -0.501+/-0.106 kg compared with -0.883+/-0.104 kg for LM; -0.400+/-0.058 kg compared with -0.661+/-0.057 kg for aLM; P for trend<0.01). The associations were attenuated slightly after adjustment for change in fat mass, but the results remained significant. Dietary protein may be a modifiable risk factor for sarcopenia in older adults and should be studied further to determine its effects on preserving LM in this population.
Australian Dietary guidelines-providing the scientific evidence for healthier Australian Diets
  • National Health
  • Medical Research
  • Council
National Health and Medical Research Council. Australian Dietary guidelines-providing the scientific evidence for healthier Australian Diets (2013). https://nhrmc.gov.au/about -us/publications/australian-dietary-guidelines [Accessed October 2020].
Consumption of whole eggs promotes greater stimulation of postexercise muscle protein synthesis than consumption of isonitrogenous amounts of egg whites in young men
  • S Van Vliet
  • E L Shy
  • Abou Sawan
  • S Beals
  • J W West
  • D W Skinner
  • S K Ulanov
  • A V Li
  • Z Paluska
  • S A Parsons
  • C M Moore
  • D R Burd
van Vliet S, Shy EL, Abou Sawan S, Beals JW, West DW, Skinner SK, Ulanov AV, Li Z, Paluska SA, Parsons CM, Moore DR, Burd NA. Consumption of whole eggs promotes greater stimulation of postexercise muscle protein synthesis than consumption of isonitrogenous amounts of egg whites in young men. Am J Clin Nutr. 2017; 106(6): 1401-1412.