Abstract
Acute muscle protein metabolism is modulated not only by resistance exercise but also
by amino acids. However, less is known about the long-term hypertrophic effect of
protein supplementation in combination with resistance training. The present study
was designed to compare the effect of 14 weeks of resistance training combined with
timed ingestion of isoenergetic protein vs carbohydrate supplementation on muscle
fiber hypertrophy and mechanical muscle performance. Supplementation was administered
before and immediately after each training bout and, in addition, in the morning on
nontraining days. Muscle biopsy specimens were obtained from the vastus lateralis
muscle and analyzed for muscle fiber cross-sectional area. Squat jump and countermovement
jump were performed on a force platform to determine vertical jump height. Peak torque
during slow (30° s−1) and fast (240° s−1) concentric and eccentric contractions of the knee extensor muscle was measured in
an isokinetic dynamometer. After 14 weeks of resistance training, the protein group
showed hypertrophy of type I (18% ± 5%; P < .01) and type II (26% ± 5%; P < .01) muscle fibers, whereas no change above baseline occurred in the carbohydrate
group. 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. In conclusion, a minor advantage of protein supplementation over carbohydrate
supplementation during resistance training on mechanical muscle function was found.
However, the present results may have relevance for individuals who are particularly
interested in gaining muscle size.
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Article info
Publication history
Accepted:
July 8,
2004
Received:
January 15,
2004
Identification
Copyright
© 2005 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
