The Effects of Oral Contraceptives on Grip Strength and Neuromuscular Activation During Short-Term Immobilization and Rehabilitation of the Wrist/Hand

Abstract

Females often experience greater weakness following immobilization compared to males. Hormonal fluctuations from the menstrual cycle or oral contraceptive (OC) use may contribute to sex differences and response variation. We examined differences in peak and rapid force and neuromuscular activation among females using monophasic OC and females not using OC following immobilization and rehabilitation. To examine potential sex differences, a male control group was included. Ten males, 10 OC females, and 10 non-OC females (mean {+/-} SD age = 23 {+/-} 3 years) immobilized their left wrist/hand with a brace for one week, followed by [≥] one week of rehabilitation. Participants completed grip tests to assess peak force and the rate of force development (RFD) before and after immobilization and post-rehabilitation, with electromyographic signals recorded from the extensor carpi radialis brevis (ECBR) and flexor digitorum superficialis (FDS). Grip force declined post-immobilization: males = -17.2 {+/-} 10.3%, non-OC = -22.3 {+/-} 24.7%, OC = -20.7 {+/-} 14.8%. No significant time x group interactions were observed for any dependent variables (p > 0.05, 2p [≤] 0.084). Time effects showed recovery post-rehab. RFD, particularly at 200 ms, declined posttest and rebounded post-rehab. ECBR excitation increased post-rehab; FDS trended upward. Only 5 participants required > one week of rehabilitation (2 males, 2 non-OC, 1 OC). We conclude that males and females exhibit similar declines and recovery in grip force after one week of wrist/hand immobilization, regardless of OC use. OC use does not appear to affect outcomes in female patients undergoing musculoskeletal rehabilitation. NEW & NOTEWORTHYPrevious studies report greater strength losses in females than males after immobilization, yet the underlying mechanisms remain unclear. This is the first study to examine whether monophasic OC use influences neuromuscular responses to disuse and recovery. We found no significant differences in the loss or recovery of peak force, RFD, or sEMG excitation between OC users, non-users, and males. Short-term immobilization and rehabilitation outcomes are not meaningfully affected by OC use in healthy, young females.