Influence of Fiber Type Composition and Capillary Density on Onset of Blood Lactate Accumulation,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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Onset of blood lactate accumulation OBLA was determined in sixteen healthy and physically active men 23-33 yrs during cycling using a continuous step-wise increased exercise intensity protocol. OBLA was defined as the exercise intensity corresponding to a lactate concentration of 4 mmol per liter of blood. Oxygen consumption, pulmonary ventilation, respiratory quotient R, heart rate and lactate concentration were monitored during each exercise intensity. Muscle biopsies were obtained from m. vastus lateralis at rest for determination of fiber type composition and capillary density. Calculated values mean or - SD for exercise intensity, oxygen consumption and ventilation at OBLA were 159 or - 37W, 2.43 or - 0.47 liters per min and 49.8 or - 10.5 liters per min or 65 or - 10 percent of V sub O sub 2 max OBLA percent V sub O 2 max was found to correlate significantly r0.75, p less than 0.001 to the relative muscle area occupied by ST Type I fibers. Furthermore, 92 of the variance in OBLA could be explained by percent ST area capillary density. It is suggested that both inherent and adaptative qualities of the exercising muscle are of significance for the onset of blood lactate accumulation.
- Anatomy and Physiology
- Medicine and Medical Research