Is muscular strength balance influenced by menstrual cycle in female soccer players?

BACKGROUND: Muscular strength imbalance is an important risk factor for ACL injury, but it is not clear the impact of menstrual cycle on muscular strength balance. Our aims were to compare muscular balance (hamstring-to-quadriceps peak torque strength balance ratio) between luteal and follicular phases and compare gender differences relative to strength balance to observe possible fluctuations in strength balance ratio. METHODS: Thirty-eight soccer athletes (26 women and 12 men) took part in this study. Athletes participated in two identical isokinetic strength evaluations for both knee (non-dominant ND and dominant D). Peak torque for quadriceps and hamstring muscles were measured in concentric mode and hamstring-to-quadriceps peak torque strength balance ratio calculated. RESULTS: Women had significantly lower hamstring-to-quadriceps peak torque strength balance ratio during the follicular compared to luteal phase, for the ND limb (P=0.011). However, no differences, between luteal and follicular phases, were observed in the D limb. In men, no difference in strength balance ratios was found between the ND and D limbs. CONCLUSIONS: These data may be useful in prevention programs for knee (ACL) injuries among soccer female athletes.