New Orleans (American Physiological Society) -- Differences in fatigue between men and women have been found in a number of previous research studies. The collective results are mixed, but a significant number of findings indicate that women fatigue less than men.

One proposed mechanism suggested to explain this difference in fatigability is that women are better able to utilize oxidative pathways of metabolism to provide the energy for muscle contraction. Efficient utilization of these aerobic pathways results in the production of lesser quantities of metabolic by-products such as inorganic phosphate, which is thought to contribute to muscle fatigue.

New research to validate this hypothesis is being presented before an annual gathering of the nation's leading physiologists. The author of "Effects Of Ischemia on Gender-Dependent Differences in Human Skeletal Muscle Fatigue," is David Russ, Ph.D. from the University of Massachusetts. He will present his findings in detail at the American Physiological Society's (APS) annual meeting, part of the "Experimental Biology 2002" conference. More than 12,000 attendees will attend the conference being held at the Ernest N. Morial Convention Center, New Orleans, LA from April 20-24, 2002.

Methodology

This research investigation compared the fatigue produced by an identical exercise protocol in men and women under two different conditions: a control condition and an ischemic condition, where blood flow (and thus oxygen) to the muscle is cut off by mechanical compression. If gender differences in fatigue exist and are due to an "oxidative advantage" for women, then the results would demonstrate that women exhibit less fatigue under control conditions, but that women and men would fatigue equally under ischemic conditions. The measures of fatigue in this study are voluntary force production, electrically stimulated force production (which eliminates motivation as a factor), and electromyography (which examines the level of muscle activation).

Results

The results support the hypotheses that women fatigue less than men, but when deprived of oxygen, they fatigue to the same extent.

Conclusions

This effort examined only one muscle, the tibialis anterior (upper two-thirds of lateral surface of tibia, interosseous membrane, and intermuscular septum). The researcher cautions that results might well vary for different muscles. Further, the findings do not explain the mechanism of the "oxidative advantage" in women. One reason could be due to more efficient and increased oxygen delivery or to a greater oxidative capacity to utilize the oxygen that is delivered to the muscle, or a combination of the two. Finally, the difference in fatigue is likely task-dependent and might change if the type of exercise changed.