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Protein nutrition and resistance exercise.
1Nutrition, Metabolism, and Exercise Laboratory, Donald W. Reynolds Center on Aging, University of Arkansas for Medical Sciences, Central Arkansas Veterans Healthcare System, Little Rock, AR 72205, USA.
Summary
Resistance exercise enhances muscle size by increasing contractile proteins. Optimal protein intake and supplementation may further boost muscle growth, especially in older adults, by supporting muscle protein synthesis and reducing nitrogen excretion.
Area of Science:
- Exercise Physiology
- Muscle Biology
- Nutritional Science
Background:
- Skeletal muscle hypertrophy, or increase in muscle size, is primarily due to increased contractile proteins.
- The precise mechanisms linking mechanical stimuli from resistance exercise to enhanced RNA and protein synthesis remain unclear.
- Eccentric contractions, involving muscle lengthening under load, cause damage that may initiate metabolic responses promoting muscle protein turnover.
Purpose of the Study:
- To explore the mechanisms underlying muscle hypertrophy in response to resistance exercise.
- To investigate the role of eccentric contractions in stimulating muscle protein synthesis.
- To examine the impact of dietary protein intake and supplementation on resistance exercise outcomes.
Main Methods:
- Analysis of muscle adaptation to resistance training, including concentric and eccentric contractions.
- Investigation of cellular and molecular responses, such as RNA synthesis and protein turnover.
- Review of studies on dietary protein intake and supplementation in conjunction with resistance exercise.
Main Results:
- Resistance exercise, particularly eccentric contractions, triggers cellular damage and inflammatory responses that may stimulate muscle protein synthesis.
- Unlike endurance exercise, resistance exercise reduces nitrogen excretion, potentially lowering protein requirements.
- Studies suggest that increased protein intake (up to 1.6 g/kg/day) can enhance hypertrophy, and protein-calorie supplements aid strength and muscle mass gains in older adults.
Conclusions:
- Eccentric contractions play a significant role in initiating adaptive responses leading to muscle hypertrophy.
- Dietary protein intake is crucial for optimizing muscle growth from resistance training, with specific recommendations for intake.
- Protein supplementation can be beneficial for maximizing strength and muscle mass gains, particularly in elderly populations undergoing resistance training.