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A descriptive comparison of expert and novice dancers? electromyographic responses to varying conditions during weight shift
Chatfield, Steven PhD , University of Oregon, Eugene, Oregon, United States; Krasnow, Donna MS, York University, Toronto, Ontario, Canada; and Herman, Amanda BA, University of Oregon, Eugene, Oregon, United States
The purpose of this study was to compare electromyographic (EMG) responses across 3 conditions of a dance motif involving forward shift of weight beginning and ending on a one-legged balance. EMG?s for the tibialis anterior, gastrocnemius, quadriceps, hamstrings, erector spinae, and abdominals were collected on 3 local professional dancers (28 ±6 y.o.) and 3 collegiate novices (19 ±1 y.o.). Variations of the movement motif used during testing were: 1) visualization only (imagining performance of the movement during quiet standing on both legs), 2) straight start (erect spine on a straight, one-legged balance), and 3) curved start (flexed spine on a bent one-legged balance). Conditions were randomly distributed across 90 trials per participant. Trials were performed to a constant 120 bpm tempo. Participants were coached to stand ready (for baseline data) prior to executing each trial on cue. EMG?s were collected continuously at 1200 Hz for 4 seconds. EMG?s were filtered, rectified, and smoothed. Analysis was based on ensemble averaging beginning with within subject data and proceeding through between group data. Change in an EMG signal was expressed in terms of standard deviations (S.D.) away from the signal?s baseline value. Overall, compared to novices, experts demonstrated faster spikes of higher amplitude EMG activity for abdominals and hamstrings (abdominals: +4.9 .S.D. in 274 msec for experts versus +2.6 S.D. in 301 msec for novices) (hamstrings: +4.8 S.D. in 287 msec for experts versus +2.0 S.D. in 324 msec for novices). Interestingly, experts had a +5.3 S.D. abdominal EMG spike during visualization without overt skeletal movement. The novice?s abdominal EMG during visualization showed no detectable change from baseline. In conclusion, these data suggest that expert dancers are different from novices in the neuromotor strategy they demonstrate for the abdominals and hamstrings. The experts? strategy may reflect increased pelvic and lumbar stability.
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