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THE EFFECT OF WHEY ISOLATE AND RESISTANCE TRAINING ON STRENGTH, BODY COMPOSITION AND PLASMA GLUTAMINE

Cribb, P J.1; Williams, A D.1; Hayes, A1; Carey, M F.1

Medicine & Science in Sports & Exercise: May 2002 - Volume 34 - Issue 5 - p S299
H30D FREE COMMUNICATION/SLIDE NUTRITION AND RESISTANCE EXERCISE
Free

1Center for Rehabilitation in Exercise and Sport Science Victoria University of Technology Australia.

Email: paul.cribb@research.vu.edu.au (Sponsor: Steve Selig, FACSM)

It is well established that athletes undertaking intense resistance training programs require higher dietary protein intakes. However very few studies have addressed what type of protein is optimal to enhance stength gains from weight training exercise.

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PURPOSE:

This study examined the effects of two commonly used dietary protein supplements, whey isolate and casein, on strength, body composition and plasma glutamine levels during a 10-week intense resistance training program.

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METHODS:

In a randomized, double-blind protocol thirteen resistance-trained males (age: 25.5 ± 2.7, 26.1 ± 2.1 yrs; weight: 84.0 ± 2.0, 79.7 ± 4.2 mean ± SEM for whey (n = 6) and casein (n = 7) groups, respectively) supplemented their normal diet with either a 100% whey isolate or casein (1.5gms/kg body wt/day) for 10 weeks. All subjects undertook the same fully supervised resistance training program three days per week. Written three-day food recordings were completed by the bodybuilders to demonstrate that subject's normal eating patterns were maintained throughout the study. Strength was assessed by 1-RM in the barbell bench press, squat and pull down. Body composition was assessed by DEXA (QDR4500). Plasma glutamine levels were determined by an enzymatic method with spectroscopic detection. All assessments occurred in the week prior, to and the week following training.

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RESULTS:

The whey isolate group achieved a significantly greater gain (P < 0.01) in lean mass (4.99 ± 0.25) than the casein group (0.81 ± 0.43kg). While both groups significantly increased (P < 0.05) strength in the three exercises assessed, the whey isolate group made greater strength increases (P < 0.05) in all three exercises compared to the casein group. The whey isolate group also showed a significant decrease (P < 0.05) in fat mass (−1.46 ± 0.52kg), whereas the casein group exhibited a slight rise (0.19 ± 0.27kg). Plasma glutamine levels, pre and post training, did not change in either group.

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CONCLUSION:

The major finding of this study was that a 100% whey isolate protein supplement was more effective at increasing muscle mass and strength and decreasing fat mass than a casein protein supplement in resistance trained athletes. Both types of protein appear to prevent a decline in plasma glutamine levels that have previously been reported with intense exercise training. Supported by AST Sports Science.

©2002The American College of Sports Medicine