Neuromuscular Strategies during Cycling at Different Muscular Demands.
OBJECTIVE
This study investigated muscle coordination while pedaling at 150 and 300 W with a cadence of 90 rpm. Changes in the variability of the electromyographic (EMG) signals were quantified in 14 subjects.


METHODS
Principal component analysis was used to find correlated EMG patterns among seven leg muscles that reflect neuromuscular strategies while pedaling. Sample entropy was used to assess the regularity of the short-term fluctuations of the EMG. Signal structure relates to the autocorrelation and to the information in the phase of the signal. This study used the information encrypted in the phase to quantify neuromuscular control and compared the results to phase-randomized surrogate data.


RESULTS
Although the pattern remained similar, the correlation between individual muscles showed effort-dependent differences. Increased workload altered the overall neuromuscular strategy indicated by changes in the contribution of individual muscles to the movement. Additionally, the executed strategy was characterized by increased structure. Regularity of the short-term fluctuations in the EMG increased significantly with effort level. Both experimental conditions showed more structure in the phase of the EMG compared to the surrogate data.


CONCLUSIONS
This increased structure in the EMG signal may represent a less random and more orderly recruited firing pattern during the pedaling task at higher effort levels.
Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, CANADA.
Hendrik
H
Enders
Vinzenz
V
VON Tscharner
Benno M
BM
Nigg
D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004576:Electromyography; D019277:Entropy; D005080:Exercise Test; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D025341:Principal Component Analysis