The Influence Of Oral Contraceptives On Rehabilitation Following Wrist/hand Immobilization

Females are more prone to musculoskeletal injuries and experience a faster decline in muscle strength during limb immobilization than males, often requiring longer rehabilitation. Hormonal fluctuations and oral contraceptives (OC) may contribute to these differences, but the underlying mechanisms are not understood. Understanding these mechanisms is critical, as there are 46 million females on birth control in the United States, with 12% using OC. PURPOSE: The purpose of this study was to investigate differences in grip force and rehabilitation duration among males, females using monophasic OC, and females not using OC after 1-week of wrist/hand immobilization. METHODS: Ten males, 10 OC females, and 8 non-OC females (overall mean ± SD age = 22 ± 3 years, body mass index = 23.4 ± 3.3 kg/m2) immobilized their left wrist/hand with a brace for one week. OC females had consistently used monophasic OC for ≥6 months prior to enrollment, whereas non-OC females avoided contraceptives for ≥6 months. Non-OC females tracked their menstrual cycle using a fertility tracker app to ensure immobilization occurred during the luteal phase. Peak grip force was assessed before immobilization, post-immobilization, and weekly throughout rehabilitation. Participants were issued a hand gripper to perform a home exercise program twice per day for 1 week. The study concluded for each participant once their maximal grip force returned to baseline. RESULTS: All groups showed similar reductions in grip force following immobilization (mean decline for males = 17%, non-OC females = 23%, OC females = 21%). The mixed factorial analysis of variance indicated that there was no group × time interaction (p = 0.383, ή2 = 0.077), suggesting that each group responded similarly to immobilization and rehabilitation. There were main effects for time (p < 0.001, ή2 = .663) and group (p < 0.001, ή2 = .614), with all groups showing a large decline in peak force that returned to baseline within 1 week and males demonstrating greater grip force than both female groups. Only five participants required additional rehabilitation to return to baseline force, with no clear delineation between groups. CONCLUSIONS: While additional studies with larger samples are needed to confirm our findings, OC do not appear to influence immobilization and rehabilitation outcomes.