Relationship between maximal aerobic power and the fatiguability during repeated isokinetic contractions / 体力科学

ABSTRACT

To investigate the relationship between maximal aerobic power (VO<SUB>2</SUB>max) and fatigu-abililty during repeated isokinetic contractions, 39 male speed skaters (mean 20.8 years) served as subjects. They were divided into two groups according to their VO<SUB>2</SUB>max levels ; high VO<SUB>2</SUB>max group (HI, n=19) and low VO<SUB>2</SUB>max group (LO, n=20) . VO<SUB>2</SUB>max was measured in all subjects during incremental exercise on a bicycle ergometer and body composition was determined by densitometry. Cross-sectional area (CSA) of the leg extensor muscles was evaluated using ultrasonic method. Fatiguability was assessed during the fatigue test consisting of 50 repeated isokinetic knee-extensions at an angular velocity of 180 deg⋅sec<SUP>-1</SUP>. Remark-able findings include<BR>1. There were no significant differences in body composition and thigh composition between the two groups except for high subcutaneous fat in group LO.<BR>2. There were significant differences in VO<SUB>2</SUB>max between group HI (3.93<I>l</I>⋅min<SUP>-1</SUP>, 67.3 m<I>l</I>⋅kg LBM<SUP>-1</SUP>⋅min<SUP>-1</SUP>) and group LO (3.59<I>l</I>⋅min<SUP>-1</SUP>, 59.9 m<I>l</I>⋅kg LBM<SUP>-1</SUP>⋅min<SUP>-1</SUP>) .<BR>3. In the fatigue test, the average initial values did not differ, however, the average final values were higher in group HI. Also, a significant difference was observed in per unit CSA between the two groups.<BR>4. Higher peak forces (kg) in group HI were observed after the initial 30 dymanic contractions per unit CSA and % of peak values (% peak force) .<BR>5. A close relationship was demonstrated between VO<SUB>2</SUB>max per LBM and the fatigue index, i. e., the mean decline in peak force with 50 contractions (r=-0.37, p<0.05) .<BR>Based on the present findings it is suggested that maximal aerobic power (VO<SUB>2</SUB>max) influences the rate of fatigue development even during short-term maximal isokinetic contractions, and that there may be some physiological cross-linkages between cardiopulmonary regulation and the metabolic properties of skeletal muscles. This finding is also in conformity with earlier results indicating the importance of oxygen delivery as a limiting factor for muscle performance.