Isokinetic torque and surface electromyography during fatiguing muscle contractions in young and older men and women

• The overall aim was to investigate the fatigue pattern and perceived fatigue during repetitive dynamic contractions in young and older men and women. Sixteen older men and women (mean age 73 ± 3 years) and 22 young men and women (mean age 28 ± 6 years) performed 100 repeated maximum concentric isokinetic knee extension contractions at 90°·s-1 (1.57 rad·s-1). Throughout the 100 contractions, peak torque (PT) and surface electromyography (EMG) signals from the rectus femoris muscle and the vastus lateralis muscle were recorded simultaneously, together with perceived fatigue (CR-10 scale of Borg). The mean frequency of the power spectrum (MNF) and the root mean square of the signal amplitude (RMS) of the EMG were affected by age and with a sex related difference but for PT the difference of the fatigue pattern was most evident between the sexes. In addition, the young men rated the highest fatigue. Based on EMG, PT and ratings of perceived fatigue it was concluded that the old men fatigued most, the old women fatigued least and the young men perceived greatest fatigue.

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