A Comparison of Three Cam Profiles as Measured by EMG and Angular Displacement

The purpose of this study was to determine if variations in cam profiles cause differences in muscle contraction as measured by surface EMG, knee joint angular displacement, and torque. There were seven hypotheses tested. The ten subjects were adult male volunteers (18-24 years) who participated in a counterbalanced treatment design study testing three variously shaped cams over five lifting tests. The results indicated that for the EMG data, the cam and lifts effect had significant Wilk's values. For the cam effect the consistent cam had the highest millivolt value. For the lift effect, the pre 1 rep max had the highest millivolt value. Results for the angular displacement demonstrated a significant Wilk's value for the cam effect only. The easy cam had the greatest degrees of displacement. Of the torque analysis, only the concentric torque showed significance at the 0.05 level. This study supports the earlier findings that the consistent cam efficiently loaded the muscle at more points in the range of motion and was able to maneuver throughout a greater arc in this same range than the easy or hard cams. However, even though the preliminary data showed differences in speed of movement, it could not be determined if there were actual differences in the amount of work produced by the cams.