Indices of mechanical power output were obtained from twelve subjects during high intensity leg cycle ergometry tests (20 second duration; 75 grams per kilogram total body mass) using two protocols: one with a standard handle-bar grip (with-grip), and one with supinated wrists (without-grip). Peak mechanical power, mean mechanical power, fatigue index and total mechanical work values were calculated for each subject during each test, and the sample mean differences associated with the two protocols were compared using paired Student t-tests. The with-grip protocol yielded significantly greater peak mechanical power output and greater fatigue index than the without-grip protocol (886 +/- 124W and 815 +/- 151W, respectively; and 35 +/- 10% and 25 +/- 8%, respectively; p<0.01). The electrical activity of the anterior forearm musculature was measured in the twelfth subject during the performance of each of the test protocols. While peak mechanical power output was greater during the with-grip protocol, than during the without-grip protocol, the electromyographs showed much greater forearm muscle activity during the with-grip protocol. Thus the protocol which allowed for the greatest measure of peak leg power output was also associated with considerable arm muscle activity. These findings should be considered when biochemical and physiological measurements are obtained from arm blood samples.