Concentric and eccentric isokinetic measurements in knee muscles during the menstrual cycle: A special reference to reciprocal moment ratios

Objective: To investigate the effects of menstrual cycle on the reliability of concentric (CON) and eccentric (ECC) isokinetic measurements and reciprocal moment ratios in knee muscles. Design: Repeated measurements. Setting: A university exercise physiology laboratory. Participants: Sixteen healthy sedentary women volunteers, aged 24 to 35 years, who had regular menstrual cycle (ranging from 24 to 32 days). Methods: Subjects were tested at 60°/sec (4 repetitions) and 180°/sec (20 repetitions) of angular velocities for CON and ECC tests at the menstrual (MP, days 1 to 3), follicular (FP, days 7 to 10), and luteal phases (LP, 19 to 21). Blood samples were analyzed for sex hormones at the FP and LP. Results: ECC and CON peak torques and total works, and their reciprocal ratios in dominant knee muscles, were not significantly different among the phases by ANOVA. Intraclass correlation coefficients (ICCs) among the phases for peak torque and total work of knee extensors in both angular velocities were in the range of .68 to .91 and .45 to .84 for CON and ECC tests, respectively. However, it was in the range of .03 to .72 and .65 to .94 for CON and ECC tests of knee flexors, respectively. In addition, there were no significant correlations between sex hormones and tested variables. Conclusion: The results suggest that the phase of the menstrual cycle should not be taken into account in isokinetic measurements.