The t test for paired data was used to determine significant differences in maximum RMS and relative activation time of muscles between the DL and SLDL exercises.
Comparisons of RMS revealed significant differences (P<0.05) between the DL and the SLDL for the VL and MG muscles.
The temporal activation between the DL and SLDL for the BF, LM, MG, and AT muscles demonstrated similar patterns.
The key findings of this study were the differences in RMS for the VL and MG muscles between the DL and SLDL exercises.
The VL RMS during the SLDL showed a constant activity during the descent phase of the movement (between -80[degrees] and 0[degrees]).
The MG activity during the DL and SLDL exercises increased slightly during the ascent phase.
During the SLDL, the BF showed the same behavior as during the DL, with a peak of muscle activity in the ascent phase between 20[degrees] and 40[degrees] during hip extension.
This hypothesis indicated that the single-joint exercise such as the SLDL may provide an increase in hamstring muscle activity.
The LM activation during the DL and the SLDL may be characterized as a normal pattern of muscle activity, since little variation was showed during the ascent and descent phases of the movements.
The AT muscle activity remained constant at a low intensity during the DL and SLDL. Relative time of activation showed high standard deviation values indicating a high variation among subjects for both exercises, which indicates individual technique may be a factor that affects muscle activity during the DL and SLDL.
However, in the current study all subjects had at least 2 yrs of resistance training experience with the DL and SLDL exercises.
The EMG data indicate that the DL is more effective for activating the VL muscle than the SLDL. However, the MG muscle showed higher muscle activation during the SLDL than the DL.