Impact of back squat training intensity on strength and flexibility of hamstring muscle group

STUDY DESIGN: True experimental design.

BACKGROUND: The back squat is an integral aspect of any resistance training program to improve athletic performance. It is also used for injury prevention of the lower limbs.

OBJECTIVE: The purpose of this study was to examine the effect of back squat training at different intensities on strength and flexibility of the hamstring muscle group (HMG).

METHODS: Twenty-two male recreational bodybuilders with at least two years of experience in resistance training were recruited to participate in a nine-week training program. They were randomly assigned to a heavy back squat group (90-95% of one repetition maximum) or a moderate-intensity back squat group (60-65% of one repetition maximum).

RESULTS: The heavy back squat group resulted in a significantly (p < 0.001) increased in one repetition maximum strength but a significant (p < 0.001) reduction in HMG flexibility when compared to their counterparts. The results of the study indicate that while a heavy back squat training program is effective in improving strength, it has an adverse effect on the flexibility of the HMG.

CONCLUSION: The implication of this study is that there is a tradeoff between strength and flexibility and trainers should select the appropriate training protocols for their athletes to maximize athletic performance.