Neuromuscular performance changes throughout the menstrual cycle in physically active females

OBJECTIVES: To determine changes in neuromuscular performance throughout the menstrual cycle in females aged 18-25. METHODS: Fifty physically active college females (25 on oral contraceptives (OC)) were recruited to participate. Data collection visits coincided with early-follicular (Fp), ovulatory (Op), and the mid-luteal (Lp) phases. Isokinetic peak torque at the knee (IPT) was measured at 60°/sec, 180°/sec, and 300°/sec. Grip force was measured using a handheld dynamometer. Plasma estradiol and progesterone confirmed menstrual cycle and serum relaxin was screened as a potential covariate. RESULTS: Grip strength was lower during Fp (30.1±0.7kg) than during Op (31.5±0.7 kg, p=0.003) and Lp (32.6±0.7 kg, p<0.001). IPT at 60°/sec was lower during Fp (83±14 nM) than during the Op (86±15 nM, p=0.02). IPTs at 180°/sec and 300°/sec were lower during Fp than Op and Lp (180°:54±10 vs. 58±10 and 61±11 nM [both, p<0.001]; 300°: 43±9 vs. 46±9 and 47±9 nM [both<0.001]. The OC group-by-phase interaction was not significant for any of the outcomes. CONCLUSIONS: Results indicate that muscular performance is diminished during Fp and the lack of group-by-phase interaction indicates that this effect is not hormone-related. These data indicate that females may be at a greater risk of injury due to decreased strength during Fp than other phases of their cycle.