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2000 Publications

Electromyographic Analysis of Exercise Resulting in Symptoms of Muscle Mchugh MP, Connolly DAJ, Eston RG, Gleim GW.Nicholas Institute of Sports Medicine and Athletic Trauma, New York, New York and School of Sport, Health and Physical Education Sciences, University of Wales, Bangor, Gwynedd, United Kingdom. - last modified 2013-02-10 00:00
Journal of Sports Sciences. 18: 163-172, 2000.


Surface electromyographic (EMG) signals were recorded from the hamstring muscles during six sets of sub-maximal isokinetic (2.6 rad/sec) eccentric (11 men, 9 women) or concentric (6 men, 4 women) contractions. EMG/torque increased during eccentric (P<0.01) but did not change during concentric exercise. Median frequency (MF) increased during eccentric (P<0.01) with no change during concentric exercise. EMG/torque was lower for sub-maximal eccentric compared with maximum isometric contractions (P<0.001).

EMG/torque for sub-maximal concentric contractions was also lower than for maximum isometric contractions (P<0.01). EMG/torque was lower for eccentric compared with concentric contractions (P<0.05). MF was higher for sub-maximal eccentric contractions compared with maximum isometric contractions (P<0.001).

MF was not different between sub-maximal concentric contractions and maximum isometric contractions (P=0.07). Eccentric exercise resulted in significant isometric strength loss (P<0.01), pain (P<0.01) and muscle tenderness (P<0.05). Greatest strength loss was seen one day following eccentric exercise, while greatest pain and muscle tenderness occurred two days following eccentric exercise.

There were no changes in these markers following concentric exercise. In conclusion, eccentric exercise resulted in moderate symptoms of muscle damage, which were absent following concentric exercise. Lower EMG/torque is consistent with selective recruitment of a small number of motor units during eccentric exercise. Higher MF for eccentric contractions may be explained by selective recruitment of fast-twitch motor units.

These data are consistent with the theory that muscle damage results from excessive stress on a small number of active fibres during eccentric contractions.