From: The effect of protein timing on muscle strength and hypertrophy: a meta-analysis
Study | Subjects | Supplementation | Protein matched with control? | Anthropometric and/or body composition assessment method | Training protocol | Strength results | Body composition results |
---|---|---|---|---|---|---|---|
Antonio et al., [33] | 19 untrained young women | 18.3Â g EAA or an equal dose of cellullose placebo taken (collectively) 20Â minutes pre and post-exercise | No | DXA | Periodized progressive resistance training consisting of exercises for all major muscle groups performed 3Â days/wk for 6 wks | Total weight lifted at the 12 RM intensity did not significantly change in either group | No significant body composition changes occurred in either group |
Goddard et al., [34] | 17 untrained older men (60–80 y) | 12 g of essential amino acids and 72 g (total) of fructose and dextrose consumed immediately after exercise | No | Computed tomography (CT). | Progressive resistance training consisting of knee extensions preformed 3 days/wk for 12 wks | Training produced a significant increase in 1RM strength and measures of maximal torque, no differences between groups | No significant differences in muscle CSA increase between groups |
Rankin et al., [35] | 13 untrained young men | Chocolate milk (providing a protein dose of 0.21Â g/kg) or a CHO-electrolyte beverage (Gatorade) immediately after exercise | No | Dual X-ray absorptiometry (DXA) and multiple upper & lower body circumference measurements | Periodized progressive resistance training consisting of exercises for all major muscle groups performed 3Â days/wk for 10 wks | 1 RM strength increased in all exercises, with no significant difference between groups | No significant differences in fat reduction, mean mass gain, or circumference changes between groups |
Andersen et al., [36] | 22 untrained young men | 25Â g protein (combination of whey, casein, egg white, and glutamine) or 25Â g maltodextrin immediately before and after exercise | No | Muscle biopsy | Periodized progressive resistance training consisting of lower body exercises performed 3Â days/wk for 14 wks | Squat jump height increased only in the protein group, whereas countermovement jump height and peak torque during slow isokinetic muscle contraction increased similarly in both groups. | The protein group showed hypertrophy of type I & II muscle fibers, whereas no significant change occurred in the CHO group |
Bird et al., [37] | 32 untrained young men | 6 g EAA or 6% CHO solution + 6 g EAA or placebo during exercise | No | DXA and muscle biopsy | Progressive resistance training consisting of exercises for all major muscle groups performed 2 days/wk for 12 wks | Training caused a significant increase in 1RM in the leg press similarly in both treatment groups compared to placebo, isokinetic strength increased in all groups, with no differences between groups | CHO + EAA showed greater gains in fat-free mass compared to placebo, fat mass decreased in all groups without any significant difference between groups |
Coburn et al., [38] | 33 untrained young men | 20 g whey + 6.2 g leucine or 26.2 g maltodextrin 30 minutes prior to and immediately after exercise | No | Magnetic resonance imaging (MRI) | Progressive resistance training consisting of knee extensions performed 3 days/wk for 8 wks | Significantly greater 1 RM strength increase in the trained limb in the protein group compared to placebo | No significant body composition changes occurred in any of the groups, CSA increases did not differ between the protein and placebo groups |
Candow, Burke, et al., [39] | 27 untrained young men & women | Whey (1.2 g/kg) + sucrose (0.3 g/kg) or placebo (1.2 g/kg maltodextrin + 0.3 g/kg sucrose) | No | DXA | Progressive, periodized resistance training consisting of exercises for all major muscle groups performed 4 days/wk for 6 wks | 1 RM strength increases in the squat and bench press were significantly greater in the protein groups than placebo | Lean mass increase was significantly greater in the protein groups than placebo |
Note that only the soy treatment was excluded from analysis. | |||||||
Candow, Chilibeck, et al., [40] | 29 untrained older men | Multi-ingredient supplement containing a protein dose of 0.3Â g/kg immediately before exercise and a CHO-based placebo immediately after, or the reverse order of the latter, or placebo before & after exercise | No | Air-displacement plethysmography, ultrasound | Progressive resistance training consisting of exercises for all major muscle groups performed 3Â days/wk for 12 wks | 1 RM strength increases in the leg press & bench press occurred in all groups, no significant differences between groups | Lean mass and muscle thickness increased in all groups, no significant difference between groups |
Cribb and Hayes, [16] | 23 young recreational male bodybuilders | 1Â g/kg of a supplement containing 40Â g whey isolate, 43Â g glucose, and 7Â g creatine monohydrate consumed either immediately before and after exercise or in the early morning and late evening | Yes | DXA and muscle biopsy | Progressive resistance training consisting of exercises for all major muscle groups performed 3Â days/wk for 10 wks | Immediate pre-post supplementation caused greater increases in 1-RM in 2 out of 3 exercises | Significant increases in lean body mass and muscle CSA of type II fibers in immediate vs. delayed supplementation |
Hartman et al., [41] | 56 untrained young men | 17.5Â g protein within milk or a soy beverage, or CHO control immediately after exercise and again 1Â hr after exercise | No | DXA and muscle biopsy | Progressive resistance training consisting of exercises for all major muscle groups performed 5Â days/wk for 12 wks | All groups experienced 1RM strength gains, but no between-group differences were seen | Type II muscle fiber area increased in all groups, but with greater increases in the milk group than in the soy and control groups, fat-free mass increased to a greater extent in the milk group compared to the soy & control groups |
Note that only the soy treatment was excluded from analysis. | |||||||
Hoffman et al., [42] | 21 well-trained young men | 42Â g protein within a multi-ingredient supplement or a CHO placebo taken once in the morning and again after training | No | DXA | Progressive, periodized resistance training consisting of exercises for all major muscle groups performed 4Â days/wk for 12 wks | 1 RM bench press strength (but not squat strength) significantly increased in the protein group, while no measures of strength increased in the placebo group | No significant between-group or absolute changes in body composition occurred |
Willoughby et al., [17] | 19 untrained young men | 20Â g whey-dominant protein or 20Â g dextrose consumed 1Â hour before and after exercise | No | Hydrostatic weighing, muscle biopsy, surface measurements | Progressive resistance training consisting of exercise for all major muscle groups performed 4Â days/wk for 10 wks | Protein supplementation caused greater increases in relative strength (maximal strength corrected for bodyweight) in bench press & leg press | Significant increase in total body mass, fat-free mass, and thigh mass with protein vs. carb supplementation |
Eliot et al., [43] | 42 untrained older men | 35 g whey protein + CHO-electrolyte solution, or whey/CHO + 5 g creatine, or creatine-only, or CHO placebo | No | DXA and bioelectrical impedance | Progressive resistance training consisting of exercise for all major muscle groups performed 3 days/wk for 14 wks | Not measured | No significant effects of any of the whey and/or creatine treatments were seen beyond body composition changes caused by training alone |
Note that creatine treatments were excluded from analysis | |||||||
Mielke et al., [44] | 39 untrained young men | 20 g whey protein + 6.2 g of leucine or 20 g maltodextrin 30 minutes before and immediately after exercise | No | Hydrodensitometry, | Dynamic constant external resistance (DCER) bilateral leg extension and bench press exercises were performed 3 days/wk for 8 wks. | 1 RM strength increased significantly in both groups without any between-group differences | No significant training-induced changes in body composition in either group, |
Verdijk et al., [21] | 28 untrained elderly men | 10Â g casein hydrolysate or placebo consumed immediately before and after exercise | No | DXA, CT, and muscle biopsy | Progressive resistance training consisting leg press and knee extension performed 3Â days/wk for 12 wks | 1 RM leg press & leg extension strength increased, with no significant difference between groups | No significant differences in muscle CSA increase between groups |
Hoffman et al., [20] | 33 well-trained young men | Supplement containing 42Â g protein (milk/collagen blend) and 2Â g carbohydrate consumed either immediately before and after exercise or in the early morning and late evening | Yes | DXA | Progressive resistance training consisting exercises for the major muscle groups peformed 4Â days/wk for 10 wks. | 1 RM & 5 RM bench press & squat strength increased, with no significant difference between groups | No significant differences in total body mass or lean body mass between groups. |
Hulmi et al., [18] | 31 untrained young men | 15Â g whey isolate or placebo consumed immediately before and after exercise | No | MRI, muscle biopsy | Progressive, periodized total body resistance training consisting of exercises for all major muscle groups trained performed 2Â days/wk for 21 wks | Strength increased similarly in the protein & placebo group, but only the protein group increased isometric leg extension strength vs the control group | Significant increase in CSA of the vastus lateralis but not of the other quadriceps muscles in the protein group vs placebo |
Josse et al., [45] | 20 untrained young women | 18Â g protein within milk or an isocaloric maltodextrin placebo immediately after exercise and again 1Â hr later | No | DXA | Progressive, periodized resistance training consisting of exercises for all major muscle groups performed 5Â days/wk for 12 wks | 1 RM strength increased similarly in both groups, but milk significantly outperformed placebo in the bench press | Lean mass increased in both groups but to a significantly greater degree in the milk group, fat mass decreased in the milk group only |
Walker et al., [46] | 30 moderately trained men and women | 19.7 g of whey protein and 6.2 g leucine or isocaloric CHO placebo 30–45 minutes before exercising and the second packet 30–45 minutes after exercising. | No | DXA | Bodyweight-based exercises and running at least 3 days/wk, externally loaded training not specified | 1 RM bench press strength increased significantly in the protein group only | Total mass, fat-free mass, and lean body mass increased significantly in the protein group only |
Vieillevoye et al., [47] | 29 untrained young men | 15 g EAA + 15 g saccharose. or 30 g saccharose consumed with breakfast and immediately after exercise | No | Ultrasonography, 3-site skinfold assessment with calipers, 3-site circumference measurements | Progressive, periodized resistance training consisting of exercises for all major muscle groups performed 2 days/wk for 12 wks | Maximal strength significantly increased in both groups, with no between-group diffrerence | Muscle mass significantly increased in both groups with no differences between groups, muscle thickness of the gastrocnemius medialis significantly increased in the EAA group only |
Wycherly et al., [22] | 34 untrained, older men & women w/type 2 diabetes | 21Â g protein, 0.7Â g fat, 29.6Â g carbohydrate consumed either immediately prior to, or at least 2Â h following exercise | Yes | DXA, waist circumference | Progressive resistance training consisting of exercises for all major muscle groups performed 3Â days/wk for 16 wks | Not measured | Fat mass, fat-free mass, and waist circumference decreased with no significant differences between groups |
Erskine et al., [48] | 33 untrained young men | 20Â g whey protein or placebo consumed immediately before and after exercise | No | MRI | 4-6 sets of elbow flexion performed 3Â days/wk for 12Â weeks | No significant differences in maximal isometric voluntary force or 1 RM strength between groups | No significant differences in muscle CSA between groups |
Weisgarber et al., [49] | 17 untrained young men and women | Whey protein dosed at 0.3Â g/kg or isocaloric CHO immediately before, during, and after exercise | No | DXA and ultrasound | Progressive resistance training consisting of exercises for all major muscle groups performed 4Â days/wk for 8 wks | 1 RM strength in the chest press increased in both groups without any between-group difference | Significant increases in muscle mass were seen without any difference between groups |