TABLE 3.
Meta-analyses of chronic effect of RET with PRO/AA supplementation on muscle size and strength1
| Change |
PRO intake |
||||||||||
| First author, year (ref) | Subjects | Groups | PRO/other | Muscle mass/CSA | RET | Size, CSA, μm2 | FFM/LM, kg | Body fat, kg | Strength, 1 RM | g ⋅ kg−1 ⋅ d −1 | g/d |
| Nissen, 2003 (177); reported effect size | n = 64: 52 young and 12 old | PRO (n = 34), PLA (n = 3) | 0.8–1.37 extra grams PRO ⋅ kg−1 ⋅ d−1 | Varied | Varied, <3 wk | — | 0.07 (–0.03, 0.17)3 | — | −0.01 (–0.15, 0.13)3 | — | — |
| Cermak, 2013 (169) | n = 444 young adults; PLA (n = 51–188) | PRO all (n = 67–264) | More PRO (42 ± 30 g (range: 6–106 g) on training days | DXA, some fCSA | Varied, <6 wk | T1: 241 (131, 350); T2: 477 (333, 620)2 | 0.81 (0.53, 1.1)2 | −0.11 (–0.5, 0.29) | 14.4 (5.2, 23.6)2 | — | Median:40; mean: 47 |
| PRO TR (n = 7–47) | — | 0.98 (0.45, 1.5)2 | — | — | Median:84; mean: 72 | ||||||
| PRO UT (n = 5–85) | — | 0.75 (0.42, 1.1)2 | — | — | Median:38; mean: 32 | ||||||
| Miller, 2014 (176) | n = 626 young and old; RET subgroup, n = 258 | Whey, diet replacement | 35–88 g/d | DXA | No-Ex + Ex, <4 wk | — | −0.66 (−2.91, 1.59)3 | −0.60 (–4.08, 2.88)3 | — | 0.23–1.2 (range) | 35–88 (range) |
| Whey, supplement | — | 0.28 (−2.79, 3.35) | −0.21 (−2.16, 1.75) | — | |||||||
| Whey vs. other sources | — | 0.37 (−1.47, 2.21) | 0.14 (−2.05, 1.76) | — | |||||||
| Whey+RET | Varied Ex | — | 2.24 (0.66, 3.81) | — | — | ||||||
| Schoenfeld, 2013 (171); reported effect size | Strength: n = 484 young and old; LM: n = 525 young and old | Overall effect size | All studies pooled | DXA, fCSA | Varied, <6 wk | — | 0.47 (0.31, 0.63)3 | — | 1.39 (0.88,1.90)3 | — | — |
| PRO: basic model | (treatment or control) as a predictor | — | 0.24 (0.04, 0.44)2,3 | — | 0.38 (–0.34, 1.10)3 | — | — | ||||
| PRO: all covariates | Group, PRO matched, training status, blinding, gender, age, body mass, training duration | — | 0.16 (–0.07, 0.38)3 | — | 0.28 (–0.52, 1.07)3 | — | — | ||||
| PRO-reduced model | PRO intake, study duration, and blinding | — | 0.14 (–0.07, 0.35)3 | — | 0.39 (–0.34, 1.11)3 | — | — | ||||
| FFM or CSA | 0.14 (–0.17, 0.46)3 | 0.08 (–0.07, 0.24)3 | — | — | — | — | |||||
| Total PRO intake only model | PRO intake | — | 0.14 (–0.07, 0.35)3 | — | — | — | — | ||||
1
Values are means (95% CIs) and are effect sizes unless stated otherwise. AA, amino acid; CSA, cross-sectional area; Ex, exercise; fCSA, myofiber cross-sectional area; FFM, fat-free mass; PLA, placebo; PRO, protein; ref, reference; RET, resistance exercise training; RM, repetition maximum; T1, myosin heavy chain I myofibers; T2, myosin heavy chain II myofibers; TR, trained; UT, untrained.
2
Effect of PRO/AAs.
3
Standardized effect size.