Quantitative EMG analysis to investigate synergistic coactivation of ankleand knee muscles during isokinetic ankle movement. Part 1: time amplitude analysis

Synergy generally refers to the coordinated action of several motor element s to produce a specific motor task, either intentionally or automatically. One example is motor irradiation, a sudden spread of synergistic muscular c oactivation resulting from a forceful single joint movement. To investigate this type of synergy pattern, a quantitative EMG approach was employed to characterize explicit neuromuscular synergy in the ankle-knee complex durin g maximal ankle isokinetic contraction. In the present study, isokinetic an kle contractions, both dorsiflexion and plantarflexion, at four different s peeds (30, 60, 120, and 240 degrees /s) were studied in a normal adult popu lation (N=11) to assess synergistic coactivation of the prime movers (tibia lis anterior and gastrocnemius) and irradiated muscles (ipsilateral and con tralateral rectus femoris and biceps femoris) of the ankle-knee complex. El ectromyographic signals were collected with surface EMG electrodes and proc essed with traditional time-amplitude analysis to examine specific neural c ontrol strategies. The data generally supported several empirical assumptio ns common to neurological facilitation techniques. (1) Motor irradiation to the knee muscles due to ankle muscle isokinetic contraction was strongly d irectionally dependent. (2) Motor irradiation to the ipsilateral knee muscl es due to ankle isokinetic contraction was speed dependent. (3) The prime m overs demonstrated a similar control strategy, irrespective of different co ntraction speeds. (C) 2001 Elsevier Science Ltd. All rights reserved.