Lester Freamon
A man of focus, commitment, sheer will...
- Член од
- 14 јануари 2015
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Introduction
A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults - PubMed
Dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults. Increasing age reduces and training experience increases the efficacy of protein supplementation during RET. With protein supplementation, protein intakes at amounts...pubmed.ncbi.nlm.nih.gov
Resistance exercise training (RET) in combination with dietary protein supplementation is a common practice, in athletes and recreational exercisers alike, with the aim of enhancing RET-induced gains in muscle mass and strength. Recognised as a potent antisarcopenic stimulus, protein supplementation has also been advocated for ageing persons participating in RET. Despite a large volume of work in this area, narrative reviews1–5 and even meta-analyses6–12 yield conflicting results as to the actual effectiveness of protein supplementation to enhance RET-mediated gains in muscle mass and strength. This lack of agreement on the efficacy of protein supplementation6–12 is likely due to the use of divergent study inclusion criteria and inclusion of subjects with differing: ages, training statuses, total protein intakes, protein sources and protein doses. Thus, an evidence-based answer to the main question of the efficacy of protein supplementation, while previously reported,7 now appears to be controversial.4
We conducted a meta-analysis that was more inclusive in nature than previous meta-analyses6–12 to provide a broad, systematic and evidence-based assessment on whether protein supplementation can augment changes in relevant RET outcomes. We used meta-regression to evaluate the impact of important potentially mediating covariates that were decided a priori to the meta-analysis. The present meta-analysis includes more than double the number of studies and participants than the largest published comprehensive meta-analysis on protein supplementation during RET to date.7ST1
We also undertook an additional rational, mechanism-based analysis that had the aim of answering the following question: is there a protein intake beyond which protein supplementation ceases to provide a measurable benefit in increasing muscle mass during RET? To answer this question, we recognised that the process of muscle protein synthesis (MPS), as the primary determinant of muscle hypertrophy,13 shows a saturable dose-response relationship with increasing protein intake.14 Since measures of MPS show good agreement with hypertrophy13 we theorised that the effect of daily protein intake on RET-induced changes in muscle mass would show a dose-responsive relationship but that this would ultimately plateau.
Methods
Inclusion criteria
Any randomised controlled trials (RCTs) that combined a RET and protein supplement intervention were considered for this meta-analysis. Trials had to be at least six weeks in duration, participants had to be performing RET at least twice per week, and at least one group had to be given a protein supplement that was not co-ingested with other potentially hypertrophic agents (eg, creatine, β-HMB, or testosterone-enhancing compounds). Only trials with humans who were healthy and not energy-restricted were accepted. Manuscripts had to be original research (not a review or conference abstract) and be written in English.
Search strategy
A systematic search of the literature was conducted (LB) in Medline, Embase, CINAHL and SportDiscus, current to January 2017 (see online supplementary appendix 1). As appropriate, a combination of keywords and subject headings was used for the following concepts: protein supplementation and resistance training or muscle strength. The original search yielded 3056 studies. Any overlooked trials were identified by consulting other reviews and meta-analyses on the subject and were added in manually (17 studies). After deduplication and screening for inclusion criteria, 155 articles were independently read/reviewed by three authors (RWM, KTM and SRM). A total of 49 RCTs were selected for inclusion in this meta-analysis (figure 1).
RET characteristics
The RET characteristics are also presented elsewhere (see online supplementary table 1). The RET interventions lasted from 6 weeks to 52 weeks (13±8 weeks) performing RET between 2 days and 5 days per week (3±1 days/week) with between 1 to 14 exercises per session (7±3 exercises/session), 1 to 12 sets per exercise (4±2 sets/exercise) and anywhere between 3 to 25 repetitions per set (9±4 repetitions/set). Four studies used just lower-body RET, two studies used just knee extensor RET, one study used elbow flexor RET only, and two studies used one lower-body and one upper-body exercise only.
Protein supplementation
Details regarding the experimental (protein supplementation) and control (placebo- or no-supplement) groups are presented elsewhere (see online supplementary table 2). A range of 4 g to 106 g of protein was supplemented per day to the protein group (36±30 g/day; young: 42±32 g/day; old: 20±18 g/day) with a range of 5 g to 44 g of protein supplemented postexercise on training days (24±11 g; young: 24±12 g; old: 23±10 g). Twenty-three conditions supplemented with whey protein, 3 with casein protein, 6 with soy protein, 1 with pea protein, 10 with milk or milk protein, 7 with whole food (eg, beef, yogurt, between-meal snack) and 13 with non-specific protein blends or blends containing multiple protein sources (eg, whey, casein, soy and egg). In 40 studies the participants consumed part or all of their daily protein supplement after their RET sessions. In 36 studies with 48 different conditions authors reported either total (g/day) or relative (g/kg/day or %kcal/day) daily protein intake preintervention and/or postintervention. There was an increase in daily protein intake in the protein group (mean±SD; range: 23±41 g/day; −25 g/day to 158 g/day; p=0.004) and no change in the control group (1±14 g/day; −17 g/day to 40 g/day; p=0.83) such that the change in daily protein intake was significantly greater in the protein group (p=0.01). Relative daily protein intake (g/kg/day) increased in the protein group (pre: 1.4±0.4, post: 1.8±0.7, Δ: 0.3±0.5 g/kg/day, p=0.002) and did not change in the control group (pre: 1.4±0.3, post: 1.3±0.3, Δ: −0.02±0.1 g/kg/day, p=0.48) such that there was a greater change in the protein group (p<0.001). Daily energy intake (kcal/day) was gathered from 23 studies with 29 conditions and did not change with the prolonged RET and protein supplementation nor was it significantly different between the protein or control groups (Δ protein group: 50±293 kcal/day, Δ control group: 70±231 kcal/day, p=0.71).
Ме мрзи да цитирам на секој сегмент посебно, но генерално следните работи не штимаат: типот на тренинг, репетиции, сетови (ниеден сериозен вежбач не вежба 2 пати неделно, уште помалку завршува тренинг со 1 вежба. Обично тренингот се движи од 15 до 21-22 сетови) и минимум се вежба 3 пати неделно, а најчесто 5 пати.
Втора работа суплементацијата со протеин: ај што почнале со смешни количини на протеин, второ дел е суплементиран (појма немаме за аминокиселинскиот состав), трето не знаеме колку била килажата на луѓето кои ја примале таа доза, трето не знаеме после колку денови е зголемен внесот и колку време биле на висок внес (според нив 158гр).
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