Menstrual cycle stage and oral contraceptive effects on anterior tibial displacement in collegiate female athletes.

AIM: The aim of this study was to establish if differences in anterior tibial displacement exists in collegiate female student-athletes at different stages of the menstrual cycle. DESIGN AND SETTING: a 2 x 3 factorial design with repeated measures on the second factor guided this study. The first independent variable was group with 2 levels (control and oral contraceptive) and the second independent variable was menstrual cycle phase with 3 levels (follicular, ovulation, luteal). The single dependent variable was anterior tibial displacement. All data were collected in a research laboratory. SUBJECTS: 53 female student athletes (control: n=28; oral contraceptive: n=25) with no previous history of knee injury or anomalies with a normal 28-30 day menstrual cycle participated. MEASUREMENTS: anterior tibial displacement (mm) measurements were taken on days 1 (follicular phase), 13 (ovulation phase), and 23 (luteal phase) of each subject's menstrual cycle using a KT1000 knee arthrometer. RESULTS: For the entire group, statistically significant increases in anterior tibial laxity were found (F=4.49; df=52.1; P<0.05) between the follicular cycle (0+/-SD =5.14 mm) and ovulation cycle (0+/-SD=5.81 mm); and follicular cycle (0+/-SD=5.14 mm) and luteal cycle (0+/-SD=5.79 mm). A separate analysis of the non-birth control group revealed no significant difference in anterior tibial laxity throughout the stages of the menstrual cycle. CONCLUSION: The results of this study suggest that: 1) the menstrual cycle does have an influence on laxity of the anterior displacement of the knee; 2) significant increases in anterior displacement are shown during the ovulation and luteal phases of the menstrual cycle; and 3) birth control subjects tend to have increased laxity when compared to those subjects who are not on hormone therapy.

In-plant evaluation of the muscle strength of workers.

The static muscular strength of the back extensors, arm flexors and hand grip were measured on industrial workers (463 men and 139 women) involved in physically demanding jobs. No significant differences in strength were found among workers on different jobs. However, strength differences were evident with respect to age and sex; women were about 60 percent as strong as men, and men below 31 years of age were stronger than men above this age.