Relationship of recovery from intense exercise to the oxidative potential of skeletal muscle

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Abstract
This study examined if there was a relationship between the aerobic-oxidative potential of skeletal muscle and the metabolic and force recovery after intense exercise. Eleven male subjects performed three bouts of unilateral knee extensions using an isokinetic device. Sixty seconds of rest separated bouts. Muscle biopsies were taken from the vastus lateralis prior to exercise, immediately after bout 2 and before bout 3. Samples were analysed for adenosine triphosphate (ATP), adenosine diphosphate (ADP), inosine monophosphate (IMP), creatine phosphate (CP) and lactate contents and citrate synthase (CS) activity. Peak torque at the end of bout 2 was 45% of initial peak torque of bout 1 (IPT1). With recovery, initial peak torque bout 3 (IPT3) was 81% of IPT1. Peak torque after recovery (IPT3/IPT1) was related to CA activity (r = 0.69). ATP, CP and ATP/ADP decreased with exercise. ADP, IMP and lactate increased. With recovery, ATP and CP remained depressed. IMP and lactate remained elevated ATP/ADP and ADP returned towards ''normal'', but only the latter attained resting levels. When analysing the individual responses the following correlations were found. After recovery, ATP/ADP (r = 0.57), ATP/ADP relative to rest (r = 0.71), lactate (r = -0.62), CP (r = 0l75) and CP relative to rest (r = 0.83) were related to CS activity. The changes in lactate (r = -0.76) and CP (r = 0.79) during recovery (bout 3-bout 2) were also related to CS activity. The results suggest that the recovery of force and the ''normalization'' of metabolite contents after short-term intense exercise are dependent on the aerobic-oxidative potential of skeletal muscle. Thus, muscles with high CS activity showed marked decreases in lactate and increases in CP contents after recovery. A low CS activity, in contrast, was associated with no or only small recovery of these metabolites.