Elsevier

Metabolism

Volume 54, Issue 2, February 2005, Pages 151-156
Metabolism

The effect of resistance training combined with timed ingestion of protein on muscle fiber size and muscle strength

https://doi.org/10.1016/j.metabol.2004.07.012Get rights and content

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.

Introduction

It is generally accepted that training and nutrition in the restitution period affects the development of skeletal muscles. Recently, focus has been on optimal nutrition and especially on the ingestion of protein to enhance hypertrophic response to resistance training. Previous research has revealed that muscle protein metabolism can be modulated not only by resistance exercise [1], [2], [3], [4] but also by changes in circulating amino acids [2], [5], [6]. Administration of amino acids in combination with resistance exercise augments protein synthesis acutely [2], [7], which would be expected to result in a more pronounced muscle hypertrophy over a prolonged period. In contrast, if subjects remain fasted after a bout of resistance training, muscle net protein balance remains negative and a catabolic state is induced [1], [4]. It therefore seems of paramount importance to ingest sufficient amounts of dietary protein in conjunction with resistance training when muscular hypertrophy or optimal restitution is the goal. Postexercise carbohydrate supplementation may also be beneficial because of a decreased rate of muscle protein breakdown [8]. Thus, a general energy intake after each training bout may be important.

On this background, the present study aimed to compare the effect of a 14-week resistance training combined with timed ingestion of isoenergetic protein vs carbohydrate supplementation on muscle morphology (determined as muscle fiber hypertrophy) in addition to muscle functional performance (determined as maximal muscle contraction strength and vertical jump performance) of young men.

Section snippets

Subjects and study design

Twenty-two young healthy men (age, 23.2 ± 0.6 years; height, 184.5 ± 2.0 cm; weight, 77.0 ± 2.6 kg; mean ± SD) participated in the study. Exclusion criteria included the following: (a) elite athletes, (b) those who engaged in resistance training in the past 6 months, (c) vegetarians, and (d) those who had regular ingestion of nutritional supplements (eg, creatine, protein drink, ribose) in the past 3 months. Most subjects were physically active on a recreational basis. All enrolled subjects

Pretraining

At pretraining, no statistical difference between the groups was observed with regard to muscle fCSA, vertical jump height, and isokinetic peak torque. In addition, no significant difference in any dietary parameter was seen between the carbohydrate and protein groups. Both groups fulfilled the recommended daily allowances of macronutrient and micronutrient intake. Furthermore, the 2 groups were similar in age, body weight, and height (Table 1).

Muscle hypertrophy

After 14 weeks of resistance training, only the

Discussion

The main findings of the present study were that resistance training combined with protein vs carbohydrate supplementation induced similar gains in mechanical muscle performance, whereas only protein supplementation induced muscle hypertrophy. Thus, resistance training combined with protein supplementation resulted in 18% and 26% increased type I and type II muscle fCSA, respectively (Fig. 1). In contrast, resistance training combined with carbohydrate supplementation did not affect muscle

Acknowledgments

This study was supported by Numico Research BV (Wageningen, the Netherlands), Danish Research Council (Copenhagen, Denmark) grant 22010254, and Danish National Foundation (Copenhagen, Denmark) grant 504-14. We thank Birgitte Lillethorup and Hanne Overgaard for technical assistance.

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