MEN AND WOMEN FATIGUE SIMILARLY DURING FATIGUING ARM CONTRACTIONS
Rudroff, T., Poston, B., Bojsen-Molr, J., & Enoka, R. M. (2004). Strength-matched men and women perform similarly on fatiguing contractions with arm muscles. Medicine and Science in Sports and Exercise, 36(5), Supplement abstract 1889.
Women often experience longer times to task failure when performing fatiguing contractions at the same relative intensity as men. One factor that can contribute to this effect is a difference in the strength of the two sexes. This study compared changes in the mean arterial pressure and electromyogram (EMG) of strength-matched men (N = 5) and women (N = 5) when performing two types of fatiguing contractions with the elbow flexor muscles for the same duration. Ss, matched for maximal torque, performed two fatiguing contractions on separate days. On one occasion they exerted a constant force with a contraction sustained at 20% maximum voluntary contraction force (Force Task) and on another day they maintained a constant elbow joint angle with an equivalent load (Position Task). The elbow was flexed to 1.57 radians with the upper arm horizontal and the forearm vertical and supinated. After an initial familiarization session and assessment of the time to task failure for the position task, each subject performed, on different days, the force and position tasks for a duration that was 90% of the time to task failure for the position task. Immediately before termination of the task, a blood pressure cuff located on the proximal upper arm was inflated to 250 mmHg for two minutes to delay recovery of blood flow so that the accumulated metabolites were kept in the muscles. The metabotropic feedback from the active muscles was estimated by measuring the change in mean arterial pressure during a two-minute occlusion compared with the values obtained in the two-minute rest period at the beginning of the protocol.
The change in the average electromyographic activity (% of initial value) for the elbow flexor muscles during the two tasks was comparable for men and women, although the increase in EMG differed for the position and force tasks. The mean arterial pressure values during blood flow occlusion, however, were similar for men and women for the position and the force tasks.
Implication. The amount of muscle activation and the muscle metabolite-induced stimulation of the exercise pressor response during two types of fatiguing contractions performed for a similar duration did not differ for strength-matched men and women.
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