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Abstract

During unimanual motor tasks, muscle activity may not be restricted to the contracting muscle, but occurs involuntarily in the contralateral resting limb. This phenomenon has been referred to as mirror electromyographic (MEMG) activity. To date, however, it is unknown if the occurrence of the physiological form of MEMG can also be observed in lower extremities (LE) during the performance of unilateral isometric leg contractions. Furthermore, it still remains elusive if and how MEMG is affected by long-term exercise training. Here, we provide novel evidence for physiological MEMG in LE during strong unilateral contractions in healthy young adults. Endurance athletes show a higher extent of MEMG in LE compared to non-athletes. While the underlying neurophysiological mechanisms of MEMG still remain elusive, our study indicates, at least indirectly, that sport-related long-term training might affect the amount of MEMG during strong isometric contractions specifically in trained limbs.