Electromyographic activity of posterior kinetic chain muscles during hamstring strengthening exercises.

ABSTRACT

OBJECTIVES: To compare the muscle activation of the biceps femoris (BF), semitendinosus (ST), gluteus maximus (GM), and contralateral erector spinae (ES) in four specific eccentric hamstring-oriented exercises using overground maximal sprints as an EMG normalization method. DESIGN: cross-sectional study. PARTICIPANTS: twenty-four healthy athletes participated in this study. MAIN OUTCOME MEASURES: The maximum EMG activation of all targeted muscles was measured during maximal sprints and four hamstring exercises Nordic hamstring (NH), Russian belt (RB), glider (GL) and lying kick (LK). Maximum EMG activation during sprints were used to normalize EMG muscle activation. RESULTS: RB and GL showed lower hamstrings activation (from 15.71% to 39.23% and from 26.34% to 31.23%, respectively), so these exercises may be used as the first step of the retraining. The higher hamstring activation was reached in the NH (from 20.15% to 66.81%) and the LK (from 50.5% to 61.2%). Regarding muscles comparison, BF and ST were the most dependent on the exercise ranging from 26.67% to 62.22%, and from 26.34% to 66.81%, respectively. CONCLUSIONS: Muscle activation is dependent on the exercise procedure. RB and GL should be used as a first step because of their low activation. Instead, NH and LK should be used at the last phases of retraining process. Considering the synergistic activation of the PKC muscles during LK, and because of its unilateral and explosive characteristics, LK seems a suitable exercise for retraining PKC muscles in general.