31P NMR study of phosphorus containing metabolites in the uterus of hamster: changes during the estrous cycle and the effect of hormonal manipulation

Physical, Biochemical, and Neuromuscular Responses to Repeated Sprint Exercise in Eumenorrheic Female Handball Players: Effect of Menstrual Cycle Phases

Graja, A, Kacem, M, Hammouda, O, Borji, R, Bouzid, MA, Souissi, N, and Rebai, H. Physical, biochemical, and neuromuscular responses to repeated sprint exercise in eumenorrheic female handball players: effect of menstrual cycle phases. J Strength Cond Res XX(X): 000-000, 2020-Very few studies have been interested in the relationship between ovarian hormones and physiological function in female athletes. The aim of this study was to assess the effect of menstrual phases (MP) on physical, neuromuscular, and biochemical responses after repeated sprint exercise (RSE) in female handball players. Ten eumenorrheic athletes (22.5 ± 1.5 years, 1.70 ± 0.04 m) participated in 3 study visits (follicular phase [FP], luteal phase [LP], and premenstrual phase [PMP]). During each MP, they performed 20 × 5-second cycle sprints interspersed with 25 seconds of rest. Maximal voluntary contraction (MVC) tests of the knee extensor muscles at 90° of knee flexion were performed before and after RSE. Peak force and electromyography (EMG) signals were measured during the MVC tests. Blood samples were collected before and 3 minutes after each session. The percentage of decrement in peak power output over the 20 × 5-second cycle test (i.e., fatigue index) calculated between sprints 1 and 20 decreased significantly during PMP (-43.3% ± 5.7%) but not in LP (-39.2% ± 7.7%) compared with FP (-32.44% ± 6.3%) (p < 0.05). Moreover, no significant difference was found between MP in all frequency components of EMG before RSE (p > 0.05). Maximal voluntary contraction, neuromuscular efficiency, and median frequency values of vastus lateralis and rectus femoris were significantly decreased in PMP compared with FP and LP (p < 0.05). Creatine kinase (CK) levels were significantly higher in PMP compared with FP and LP after RSE (p < 0.05). These findings suggest that RSE induces more peripheral fatigue associated with muscle damage in PMP. This might be attributable to hormonal variation across MP. Therefore, FP seems to be the right time for intense training to improve strength performance.

Effects of menstrual phase on performance and recovery in intense intermittent activity

Game sport and training require repeated high intensity bursts. This study examined differences between high intensity, intermittent work in two phases of the menstrual cycle. Six physically active young women (age 19-29) performed 10 6-s sprints on a cycle ergometer in both the mid-follicular (FP) (days 6-10) and late-luteal phases (LP) (days 20-24) of the menstrual cycle. Work, power, oxygen intake (VO2) parameters, and capillarized blood lactate were measured. Data are analyzed using the Friedman and Wilcoxon matched pairs tests. There was no difference between menstrual phases in peak 6-s power (6.8(0.6) W kg(-1) in FP, 6.9(0.6) W kg(-1) in LP), the drop off in work (1.2(3.5) J kg(-1) in FP and 1.0(2.7) J kg(-1) in LP), or in the sprint VO2 (23.7(1.5) mL kg(-1) min(-1) in LP and 24.3(2.4) mL kg(-1) min(-1) in FP). Capillarized blood lactate was also similar in both phases of the menstrual cycle both at 1 min (9.2(2.7) mmol L(-1) in FP, 9.2(3.1) mmol L(-1)) and at 3 min (9.0(2.2) mmol L(-1) in FP, 9.2(2.2) mmol L(-1) in LP). However, the average 6-s work was greater in the LP (39.3(3.4) J kg(-1)) than during the FP (38.3(3.1) J kg(-1)) (P=0.023). The recovery VO2 was also greater in the LP than the FP (26.3(2.4) mL kg(-1) min(-1) in LP, 25.0(2.6) mL kg(-1) min(-1) in FP, P=0.023). Average work over a series of sprints and the VO2 consumed between sprints may be slightly greater during the LP than the FP of the menstrual cycle.