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EMG analysis of lower extremity muscle recruitment patterns during an unloaded squat
During an unloaded squat, hamstring and quadriceps co-contraction has been documented and explained via a co-contraction hypothesis. This hypothesis suggests that the hamstrings provide a stabilizing force at the knee by producing a posteriorly-directed force on the tibia to counteract the anterior tibial force imparted by the quadriceps. Research support for this hypothesis, however, is equivocal. Therefore, the purposes of this study were 1) to determine muscle recruitment patterns of the gluteus maximus, hamstrings, quadriceps, and gastrocnemius during an unloaded squat exercise via EMG and 2) to describe the amount of hamstring-quadriceps co-contraction during an unloaded squat. Surface electrodes were used to monitor the EMG activity of six muscles of 41 healthy subjects during an unloaded squat. Each subject performed three 4-s maximal voluntary isometric contractions (MVIC) for each of the six muscles. Electrogoniometers were applied to the knee and hip to monitor joint angles, and each subject performed three series of four complete squats in cadence with a metronome (50 beats.min-1). Each squat consisted of a 1.2-s eccentric, hold, and concentric phase. A two-way repeated measures ANOVA (6 muscles X 7 arcs) was used to compare normalized EMG (percent MVIC) values during each arc of motion (0-30°, 30-60°, 60-90°, hold, 90-60°, 60-30°, 30-0°) of the squat. Tukey post-hoc analyses were used to quantify and interpret the significant two-way interactions. Resu
Lippincott Williams & Wilkins
PMID : 9107637 ISSN : 0195-9131 CODEN : MSPEDA
Medicine and science in sports and exercise A. 1997, vol. 29, n° 4, pp. 532-539 [bibl. : 22 ref.]
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