Author(s): ROBERTSON, E., O'LEARY, T., MYERS, S., COOMBS, C., TANG, J., GREEVES, J., Institution: BRITISH ARMY, Country: UNITED KINGDOM, Abstract-ID: 1342

INTRODUCTION:
Hormonal contraceptives, commonly used by female athletes and servicewomen, contain synthetic oestradiol and/or progestogens that influence endogenous oestradiol and androgens; these hormones have widespread effects on neuromuscular and musculotendon function. This study compared neuromuscular function and musculotendon properties in physically active women using different hormonal contraceptive methods.
METHODS:
Participants were 66 women (aged 18-38 y) who were naturally menstruating (MC) (n = 20) or using the combined oral contraceptive pill (COCP) (n = 17), a progestogen-only contraceptive (POC) (n = 14), or the intra-uterine system (IUS) (n = 15). Body composition was determined by DXA and current physical activity recorded by questionnaire. Experimental testing was completed at ovulation (confirmed by urinary luteinising hormone) for MC, at the end of the active pill phase (day 21) for COCP, and at a time of convenience for POC and IUS. Fasted circulating concentrations of oestradiol, testosterone, sex hormone binding globulin (SHBG), androstenedione, dehydroepiandrosterone-sulfate (DHEA-S), and insulin-like growth factor-I (IGF-I) were measured. Knee extensor isometric, and knee extensor and flexor isokinetic (60 and 180°·s-1), peak torque were measured using isokinetic dynamometry. Lower limb muscle and tendon stiffness, tone, and elasticity were measured using digital palpation. A one-way ANCOVA compared groups controlling for age, body mass, and physical activity.
RESULTS:
There were no between-group differences in demographics, body composition, or physical activity. IGF-I and DHEA-S did not differ between groups (p ≥ 0.089). Oestradiol was higher in MC than COCP and POC (p ≤ 0.032) but not different to IUS (p = 0.334). Oestradiol was higher in POC and IUS (p < 0.001) than COCP but POC and IUS were not different (p = 0.334). Testosterone was higher in IUS than COCP (p = 0.005) but was not different between other groups (p ≥ 0.061). SHBG was lower in MC than COCP (p < 0.001) but MC was not different to POC or IUS (p ≥ 0.143). SHBG was higher in COCP than POC and IUS (p < 0.001) but POC and IUS were not different (p = 0.903). Free androgen index was higher in MC and POC than COCP (p < 0.001) but MC and POC were not different (p = 0.435). Free androgen index was higher in IUS than MC and COCP (p ≤ 0.048) but not different between IUS and POC (p = 0.435). Androstenedione was higher in MC than COCP (p < 0.001) but MC was not different to POC or IUS (p ≥ 0.058). Androstenedione was higher in POC and IUS (p ≤ 0.006) than COCP but POC and IUS were not different (p = 0.363). Peak knee extensor torque, peak knee flexor torque, and lower limb musculotendon elasticity, stiffness, and tone did not differ between groups (p ≥ 0.077).
CONCLUSION:
Hormonal contraceptives may influence circulating androgens, but it is unlikely these androgens exert measurable effects on lean mass, neuromuscular function, or musculotendon properties.