isometric exercise in human skeletal muscle

The present work was aimed at measuring intramuscular oxygen consumption ( ) as a function of temperature (T), Ȯ2 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 -T curve should display a maximum for some ‘optimal’ T. Intramuscular T and Ȯ2 measurements were performed using a combined deep body temperatureynear infrared probe during muscle cooling. At rest, increased non-linearly and monotonically as a function of T (ns8). increased ;2 times when going from ̇ ̇ O O 2 2 26 to 36 8C. A log( )-T plot or a log( )-1yT did not linearise the data. During isometric contraction, values at ̇ ̇ ̇ O O O 2 2 2 26.8"0.6, 28.6"0.9, 31.9"0.9 and 35.9"0.9 8C were 3.04"1.26, 7.60"1.64, 4.43"1.95, and 6.64"1.37 mmol 100 g min , respectively (ns6). The value at 28.6 8C was significantly higher (P-0.05) than that at 26.8 and 31.9 y1 y1 Ȯ2 8C. The ‘sudden’ change at 28.6 8C is compatible with the phenomenon observed at the mitochondrial level. 2002 Ȯ2 Elsevier Science Inc. All rights reserved.