Mechanomyographic and electromyographic responses to submaximal cycle ergometry


Housh, D.J.; Perry, S.R.; Bull, A.J.; Housh, T.J.; Johnson, G.O.; Ebersole, K.T.; D.V.ies, H.A.

Medicine and Science in Sports and Exercise 31(5 Suppl.): S223

1999


The purpose of this study was to examine the mechanomyographic (MMG) and electromyographic (EMG) responses during continuous, submaximal cycle ergometry. Eight adult subjects (age=22±2 yrs) performed an incremental test to voluntary exhaustion for the determination of peak power (Ppeak) and two continuous 15 minute rides at 50 and 65% Ppeak. EMG ([mu]Vrms) and MMG (m Vrms) amplitude values were recorded every 30 seconds from the vastus lateralis using a bipolar surface electrode arrangement and piezoelectric crystal contact sensor, respectively. The EMG and MMG amplitude values from the submaximal rides were normalized using the highest values recorded during the maximal test and plotted versus time for each power output. The results of regression analyses indicated that there were no significant (p>0.05) slopes (slopes=0) for the normalized EMG versus time relationships at 50 or 65% Ppeak. There were however, significant (p<0.05) negative slopes for the normalized MMG versus time relationships at both 50 and 65% Ppeak. These findings indicated that there was a dissociation between the electrical (EMG) and mechanical (MMG) aspects of muscle activity during continuous cycle ergometry. Furthermore, unlike previous studies using isometric exercise, MMG amplitude decreased across time even though the power output was unchanged. It is possible that changes in muscle temperature and/or fluid content during the continuous rides contributed to the decreases in MMG amplitude in the present study.