ELECTROMYOGRAPHIC ANALYSIS OF STANDING POSTURE AND DEMI-PLIE IN BALLET AND MODERN DANCERS

Surface electromyography was used to analyze lower extremity muscle ac tivity during standing posture and demi-plie in first position with lo wer extremities turned out, in five ballet and seven modern female pro fessional dancers. In standing posture, increased electromyographic (E MG) activity above baseline was detected most frequently at the medial gastrocnemius (54% standing repetitions) and tibialis anterior (29%) electrodes (all dancers); in ballet dancers, increased EMG activity du ring standing was significantly less frequent at the medial gastrocnem ius, but more frequent at the tibialis anterior, than in modern dancer s. In demi-plie, the tibialis anterior had a discrete peak of EMG acti vity at midcycle in all dancers (97% demi-plies). All dancers also had midcycle EMG activity in both vastus lateralis and medialis (100% dem i-plies). At the end of rising phase of demi-plie, ballet dancers had greater EMG activity than at midcycle in vastus lateralis (100% demi-p lies) and medialis (92%); in modern dancers, end-rising phase voltage was lower than at midcycle for vastus lateralis (71% demi-plies) and m edialis (83%). Genu recurvatum greater than or equal to 10 degrees was observed at the beginning and end of demi-plie in all ballet dancers, but not in modern dancers. There was marked variation of EMG activity during demi-plie in the lateral gastrocnemius, medial gastrocnemius, gluteus maximus, hamstrings, and adductors. The results support the hy pothesis that ballet and modern dancers have different patterns of mus cle use in standing posture and demi-plie, which in part may be a resu lt of differences in genu recurvatum and turnout between the two group s.