Continuous versus separate isokinetic test protocol: the effect of estradiol on the reproducibility of concentric and eccentric isokinetic measurements in knee muscles.

OBJECTIVE: To investigate the effects of estradiol on the reliability of concentric and eccentric isokinetic measurements of knee muscles and to compare the reproducibility of measurements in a continuous test protocol and a separate test protocol.

DESIGN: Repeated measurements.

SETTING: A university exercise physiology laboratory.

PARTICIPANTS: Twenty healthy sedentary women volunteers, aged 19 to 37 years, who had regular menstrual cycles (ranging from 27 to 35 days). Subjects were randomly divided into two groups: continuous test group (n = 10) and separate test group (n = 10) and tested at the menstrual phase (days 1 to 3) and preovulatory phase (days 12 to 14) in both legs.

METHODS: Continuous reciprocal flexion-extension contractions were used in the continuous test group, and separated flexion and extension contractions were used in the separate test group. Four different test protocols were designed to determine the effects of test mode and number of contractions on the isokinetic measurements: Group A, 4 reciprocal flexion-extension repetitions at each angular velocity of 60 degrees/sec and 180 degrees/sec in one leg in the continuous test group; Group B, 4 and 20 reciprocal flexion-extension repetitions at 60 degrees/sec and 180 degrees/sec, respectively, in the contralateral leg in the same group; Group C, 4 repetitions in extensors and flexors at each angular velocity of 60 degrees/sec and 180 degrees/sec with a 5-minute rest between the two muscle groups in one leg in the separate test group; and Group D, 4 repetitions at 60 degrees/sec and 20 repetitions at 180 degrees/sec for extensors and flexors with a 5-minute rest between the two muscle groups in the contralateral leg in the same group. Blood samples were analyzed for sex hormones, creatine kinase, and lactate dehydrogenase before the tests at the menstrual phase and the preovulatory phase. In addition subjective assessment of muscle soreness was made at each blood sampling.

RESULTS: Concentric and eccentric peak torque, average power, total work, and endurance ratio at both angular velocities were not significantly different in the two phases of the cycle by paired observation t test for each of the four groups. Except for concentric and eccentric endurance ratios of quadriceps and hamstrings, and concentric peak torque and average power of hamstrings at 180 degrees/sec in Group D, intraclass correlation coefficients of tested variables showed correlations that were moderate to excellent (p < .05) between two phases. In addition, there were no significant correlations between estradiol and the tested variables. Resting serum creatine kinase and lactate dehydrogenase activities and the score of muscle soreness were at the baseline and not significantly different prior to the tests performed at preovulatory and menstrual phases.

CONCLUSIONS: The results suggest that: (1) reproducibility of isokinetic tests during the menstrual cycle is not influenced by sex hormone fluctuations, particularly estradiol; (2) when compared with the separate test protocol used in this study, the continuous test protocol is more appropriate to measure peak torque, average power, total work, and endurance ratio for both muscle groups of the knee even if the number of contractions is changed. However, these conclusions are specific to sedentary individuals; to make more valid conclusions, further studies with different subject groups are needed.