Local xenon 133 clearance from the quadriceps muscle during exercise in man.

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Abstract
Muscle blood flow (MBF) in the lateral portion of m. quadriceps was measured at rest and during exercise on a bicycle ergometer at 3 submaximal and 1 maxi-mal work loads in 15 young males, 7 untrained (maxium O2 consumption VO2max 3.3 liters/min) and 8 trained (VO2max 4.5 1/min.) subjects. The flow was measured by the local injection technique and the injections of 133Xe were repeated for every flow calculation. The elimination rate was recorded for 15 min. at rest and during submaximal loads, and for at least 4 min. during maximal work. The elimination curves during exercise were usually evaluated using 2 exponential functions. The fast component contained an average 83% of the injectate and has been considered a function of the blood flow to the muscle fibers. The muscle blood flow increased gradually with increasing work levels, but when approaching maximal work levels, there was a tendency to a declining rate in flow increase. Trained and untrained subjects had identical MBF at equal relative work loads. Mean values for MBF were 15, 28, 43, and 49 ml/(100 g x min.) at work loads corresponding to 24, 48, 75, and 99% of individual maximal O2 uptake.