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Skeletal muscle buffer value, fibre type distribution and high intensity exercise performance in man
A F Mannion1, P M Jakeman, P L Willan
1School of Sport and Exercise Sciences, University of Birmingham, UK.
Experimental Physiology
|January 1, 1995
Summary
Muscle buffer value (beta) does not limit high-intensity exercise performance. Instead, type II muscle fiber area is key, enhancing dynamic but hindering isometric exercise capacity by influencing lactate and pH levels.
Area of Science:
- Exercise Physiology
- Muscle Physiology
- Biochemistry
Background:
- Understanding factors limiting high-intensity exercise performance is crucial for training and athletic development.
- The roles of muscle buffer capacity, fiber type, and metabolic byproducts (lactate, pH) are complex and interconnected.
- Previous research suggests potential links, but direct interrelationships require further investigation.
Purpose of the Study:
- To examine the interrelationships between quadriceps femoris muscle buffer value (beta), muscle fiber type distribution, and changes in lactate concentration and pH.
- To determine the influence of these factors on performance during fatiguing dynamic and isometric exercise.
- To identify the primary determinants of high-intensity exercise capacity.
Main Methods:
- Muscle biopsy samples were obtained from 18 healthy volunteers at rest and post-exercise.
- Analysis included muscle buffer value (beta), type II fiber area percentage, muscle lactate concentration, and pH.
- Exercise protocols involved fatiguing dynamic (modified Wingate Test) and isometric (60% MVC) contractions.
Main Results:
- Muscle buffer value (beta) showed a positive, non-significant correlation with type II fiber area.
- Elevated beta was associated with less pH decrease but did not improve performance or lactate accumulation.
- Superior dynamic exercise performance correlated with high muscle lactate and low pH, dependent on type II fiber area.
- Isometric exercise performance showed a trend towards association with low lactate and high pH.
- Type II fiber area was the most important determinant of high-intensity exercise capacity, favoring dynamic over isometric performance.
Conclusions:
- Muscle buffer value is not a primary limiting factor for high-intensity exercise performance.
- Intramuscular acidosis's role in fatigue may be indirect, with type II fiber area being a more significant determinant.
- A high proportion of type II fibers enhances dynamic exercise capacity but may impair isometric performance.