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High-resistance training and muscle metabolism during prolonged exercise
C Goreham1, H J Green, M Ball-Burnett
1Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
The American Journal of Physiology
|March 10, 1999
Summary
High-resistance training (HRT) improves muscle metabolism, increasing phosphocreatine and glycogen while lowering lactate. These metabolic changes occur independently of fiber hypertrophy, suggesting a distinct adaptation mechanism.
Area of Science:
- Exercise Physiology
- Muscle Metabolism
- Sports Science
Background:
- High-resistance training (HRT) is known to induce muscle adaptations.
- The relationship between muscle fiber hypertrophy and metabolic changes during submaximal exercise requires further investigation.
Purpose of the Study:
- To determine if muscle submaximal exercise metabolism changes occur due to fiber hypertrophy induced by HRT.
- To examine metabolic adaptations at different stages of a 12-week HRT program.
Main Methods:
- Untrained males underwent 12 weeks of lower-limb HRT (3 days/wk, 3 sets, 6-8 RM).
- Muscle metabolism was assessed using a two-stage cycle test at 57% and 72% of pretraining peak aerobic power (VO2 peak) at 4, 7, and 12 weeks.
- Muscle phosphocreatine (PCr), lactate, and glycogen levels were measured.
Main Results:
- HRT led to increased PCr and glycogen, and decreased lactate at the end of exercise, particularly at 72% VO2 peak.
- These metabolic adaptations occurred by 4 weeks of training, preceding observed fiber hypertrophy.
- Fiber hypertrophy, observed at 7 and 12 weeks, did not further enhance the metabolic response.
- No significant changes in VO2 peak or submaximal exercise oxygen consumption rate were found.
Conclusions:
- HRT induces significant muscle metabolic adaptations during submaximal exercise.
- These metabolic improvements occur independently of fiber hypertrophy.
- Early metabolic adaptations to HRT are not mediated by changes in muscle fiber size or oxidative capacity.