Is myoelectric activity distributed equally within the rectus femoris muscle during loaded, squat exercises?

Publication date: Available online 9 January 2017
Source:Journal of Electromyography and Kinesiology
Author(s): Leonardo Mendes Leal de Souza, Desirée Barros da Fonseca, Hélio da Veiga Cabral, Liliam Fernandes de Oliveira, Taian Martins Vieira
Myoelectric activity distributed locally within RF was reported for isometric contractions, walking and fatigue. Here we investigate whether myoelectric activity distributes evenly within RF during squat. Surface electromyograms (EMGs) were sampled proximally and distally from RF with arrays of electrodes, while thirteen healthy volunteers performed 10 consecutive squats with 20% and 40% of their body weight. The root mean square (RMS) value, computed separately for thirds of the concentric and eccentric phases, was considered to assess the proximo-distal changes in EMG amplitude during squat. The channels with variations in EMG amplitude during squat associated with shifts in the muscle innervation zone were excluded from analysis. No significant differences were observed between RF regions when considering squat phases and knee joint angles individually (P>0.16) while a significant interaction between phase and knee joint angle with detection site was observed (P<0.005). For the two loads considered, proximal RMS values were greater during the eccentric phase and for the more flexed knee joint position (P<0.001). Our results suggest inferences on the degree of RF activation during squat must be made cautiously from surface EMGs. Of more practical relevance, there may be a potential for the differential adaption of RF proximal and distal regions to squat exercises.



http://ift.tt/2jdCSwG