Hamstring-to-quadriceps activation ratio during lower-limb strengthening exercises

ABSTRACTMultiple exercises included in strength training involve greater activation of the quadriceps compared to hamstring muscles, which may lead to knee joint imbalances. The aim of this study was to examine the ratio of surface electromyography (sEMG) activity hamstring and quadriceps muscle groups (hamstring-to-quadriceps activation ratio; H:Q EMG), as well as lateral to medial hamstring activation ratio (LH:MH) in parallel squat, Romanian deadlift, hip thrust, lying leg curl and seated knee extension. The H:Q EMG was greater during lying leg curl compared to other exercises during both the concentric and eccentric phase, however the Romanian deadlift and hip thrust also resulted in relatively high H:Q EMG. Pairwise comparisons revealed that LH:MH was greater in the parallel squat compared to the Romanian deadlift and hip thrust in the concentric phase, and compared to the Romanian deadlift and hip thrust during the eccentric phase. Our data suggests that the lying leg curl promotes the greatest hamstring activation and H:Q EMG, amongst the exercises investigated, while also providing relatively homogenous LH:MH. The lying leg curl should be considered as a primary exercise in rehabilitation and training programmes, aiming to proportionally activate LH:MH and increase H:Q EMG, which may improve knee muscle balance.KEYWORDS: Injury preventionmuscle strength imbalancemuscle activationstrength trainingsurface electromyography Abbreviations EMG=electromyographySemg=surface electromyographyH:Q=Hamstring-to-quadriceps ratioLH:MH=lateral-to-medial hamstring ratioRF=rectus femorisVL=vastus lateralisVM=vastus medialisMH=medial hamstringLH=lateral hamstringHIS=hamstring strain injuryACL=anterior cruciate ligamentMVICs=maximal voluntary isometric contractionsRM=repetition maximumRMS=root mean squareAcknowledgementsWe also thank to Strength Training Research Group, all participants who participated in this research and made it possible.Disclosure statementThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.Data availability statementRaw data will be available upon request.Data transparencyAll authors make sure that all data and materials as well as software application or custom code support their published claims and comply with field standards.Additional informationFundingFV received a PhD scholarship from CAPES and CNPq Brazilian Government Associations Program. MD received a PhD scholarship from Australian Government Research Training Program.