Non-standard O2 consumption-temperature curves during rest and isometric exercise in human skeletal muscle

The present work was aimed at measuring intramuscular oxygen consumption (0,) as a function of temperature (T), in human forearm, during rest and aerobic isometric exercise (4% of the maximal voluntary contraction, MVC). Based upon results from in vitro experiments performed on isolated mitochondria of animal species, it was hypothesised that, during isometric exercise, the O-2-T curve should display a maximum for some 'optimal' T. Intramuscular T and measurements were performed using a combined deep body temperature/near infrared probe during muscle cooling. At rest, O-2, increased non-linearly and monotonically as a function of T (n = 8). O-2, increased similar to2 times when going from 26 to 36 degreesC. A log(O-2)-T plot or a log(O-2)-I/T did not linearise the data. During isometric contraction, 0, values at 26.8 +/- 0.6, 28.6 +/- 0.9, 31.9 +/- 0.9 and 35.9 +/- 0.9 degreesC were 3.04 +/- 1.26, 7.60 +/- 1.64, 4.43 +/- 1.95, and 6.64 +/- 1.37 mumol 100 g(-1) min(-1), respectively (n=6). The O-2. value at 28.6 degreesC was significantly higher (P<0.05) than that at 26.8 and 31.9 degreesC. The 'sudden' 6, change at 28.6 degreesC is compatible with the phenomenon observed at the mitochondrial level. (C) 2002 Elsevier Science Inc. All rights reserved.