Stance width and bar load effects on leg muscle activity during the parallel squat.
OBJECTIVE
Altering foot stance is often prescribed as a method of isolating muscles during the parallel squat. The purpose of this study was to compare activity in six muscles crossing the hip and/or knee joints when the parallel squat is performed with different stances and bar loads.


METHODS
Nine male lifters served as subjects. Within 7 d of determining IRM on the squat with shoulder width stance, surface EMG data were collected (800 Hz) from the rectus femoris, vastus medialis, vastus lateralis, adductor longus, gluteus maximus, and biceps femoris while subjects completed five nonconsecutive reps of the squat using shoulder width, narrow (75% shoulder width), and wide (140% shoulder width) stances with low and high loads (60% and 75% 1RM, respectively). Rep time was controlled. A goniometer on the right knee was used to identify descent and ascent phases. Integrated EMG values were calculated for each muscle during phases of each rep, and the 5-rep means for each subject were used in a repeated measures ANOVA (phase x load x stance, alpha = 0.05).


RESULTS
For rectus femoris, vastus medialis, and vastus lateralis, only the load effect was significant. Adductor longus exhibited a stance by phase interaction and a load effect. Gluteus maximus exhibited a load by stance interaction and a phase effect. Biceps femoris activity was highest during the ascent phase.


CONCLUSIONS
The results suggest that stance width does not cause isolation within the quadriceps but does influence muscle activity on the medial thigh and buttocks.
McCaw
S T
ST
Department of Health, Physical Education and Recreation, Illinois State University, Normal 61790-5120, USA. smccaw@ilstu.edu
Melrose
D R
DR
D000328:Adult; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D007866:Leg / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*