Quadriceps Electromyographic Activity in Closed and Open Kinetic-Chain Exercises with Hip-Adductor Co-Contraction in Sedentary Women

Background: Different closed and open kinetic-chain exercises with hip-adductor co-contraction have different effects on quadriceps activity. The aim of this study was to investigate the difference in quadriceps activity during the squat (SQ) and knee extension (KE) and straight leg raise (SLR) exercises with and without hip adduction in sedentary women. Methods: Twenty-eight sedentary women aged 44.5 ± 8.5 years were recruited. They performed three exercises with and without hip adduction. Surface electromyography (sEMG) activity was measured on the rectus femoris (RF), vastus medialis oblique (VMO) and vastus lateralis (VL) muscles. The levels of sEMG activities of the three muscles were compared among the six exercises using a repeated-measures ANOVA. Results: The findings showed that RF activity was lowest during the SQ alone and highest during the SLR exercise (p < 0.05 to 0.001). The VMO activity was significantly greater in the SQH than in the five types of exercises (p < 0.05 to 0.001), which led to a significant VMO/VL ratio as well. VL activity increased while the squat with hip adduction and knee extension with hip adduction exercise compared with SQ alone. Conclusion: This study indicates that a closed-chain squat with hip co-contraction can produce the VMO and VMO/VL ratio activity, while an open chain of SLR better activates the RF activity. The findings support the understanding of quadriceps activity in different exercises to be an alternative home-based exercise for physical therapy in women facing muscle weakness.