Mechanomyographic and electromyographic responses to eccentric and concentric isokinetic muscle actions of the biceps brachii

Mechanomyographic amplitude and mean power output during maximal, concentric, isokinetic muscle actions

“…These findings are consistent with our previous studies in which we hypothesized 14,15,30,31 that the velocity-related increases in MMG amplitude were due to decreases in muscle stiffness and/or increases in the rate of actin-myosin cycling.…”

“…Bipolar (7.62 cm center-tocenter) surface electrodes (Quinton Quick Prep silver-silver chloride, Quinton Instrument Co., Bothell, Washington) were placed along the longitudinal axes of the VL, RF, and VM muscles of the dominant leg according to the procedures of Ebersole et al 9 The interelectrode distance was selected to accommodate placement of the MMG sensor between the EMG electrodes. 9,30 The placement for the VL was over the lateral portion of the muscle at approximately the midpoint between the head of the greater trochanter and lateral condyle of the femur, for VM was 20% of the distance between the medial joint line and the anterior superior spine of the pelvis, 33 and for RF was 50% of the distance between the inguinal crease and the superior border of the patella. The reference electrode was placed over the iliac crest.…”

“…That is, as velocity increased, MMG amplitude increased while PT decreased. [13][14][15]30,31 Recently, however, Bodor 3 suggested that MMG amplitude may be more closely related to muscle power output than PT during maximal, concentric, isokinetic muscle actions.…”

“…23 Most previous studies have examined MMG responses during isometric muscle actions. 8,9,11,29,32,35 Recent studies, however, have investigated MMG amplitude responses during isokinetic [14][15][16]30,31 and isotonic 7,25 muscle actions as well as cycle ergometry. 28,36 Evetovich et al [14][15][16] and Smith et al 30,31 reported velocity-related dissociations between MMG amplitude and peak torque (PT) during maximal, concentric, isokinetic muscle actions.…”

“…That is, as velocity increased, MMG amplitude increased while PT decreased. [13][14][15]30,31 Recently, however, Bodor 3 suggested that MMG amplitude may be more closely related to muscle power output than PT during maximal, concentric, isokinetic muscle actions. Therefore, the present study was designed to test this hypothesis by determining the velocity-related patterns for MMG amplitude, EMG amplitude, mean power output (MP), and PT of the superficial muscles of the quadriceps femoris during maximal, concentric, isokinetic leg extensions at velocities ranging from 60°to 300°/s.…”