Oral contraceptive use and adaptations to exercise training

Abstract

Purpose: Oral contraceptive (OC) use reduces peak aerobic capacity (V O2peak) however, whether it also influences adaptations to training was yet to be determined. This study aimed to examine the influence of OC use on time-to-fatigue (TTF) and peak exercise performance [peak power output (PPO)] and physiological adaptations [ VO2peak and peak cardiac output (Qpeak)] following sprint interval training (SIT) in recreationally-active women. Additionally, due to the potential altered blood distribution as a result of OC use, we investigated central physiological factors [pulmonary oxygen uptake kinetics (V O2p), cardiac output (Q ) and heart rate (HR) kinetics] and peripheral tissue saturation index (TSI) which may have explained any differences in performance adaptation between groups. Methods: On two separate occasions, women taking an OC (n = 25) or experiencing natural regular menstrual cycles (MC; n = 22) completed an incremental exercise test to assess V O2peak, PPO, and Qpeak, and a square-wave step-transition protocol to moderate (90%POVT) and heavy (Δ50%POVT) exercise to assess TTF, V O2p, Q , HR and TSI responses before, immediately after, and four weeks following 12 sessions of SIT. The SIT consisted of 10, oneminute efforts at 100-120% PPO in a 1:2 work: rest ratio. Results: Though V O2peak increased in both groups following SIT (both p < 0.001), the MC group showed greater improvement (OC +8.5%; MC +13.0%; p = 0.010). Similarly, Qpeak increased in both groups, with greater improvement in the MC group (OC +4.0%; MC +16.1%; p = 0.013). PPO and TTF increased in both groups (OC +13.1%; MC +13.8%; NS). All pulmonary, cardiovascular and muscular on-kinetic parameters improved following SIT in both groups with the exception of V O2p in the OC-group (p = 0.371) and TSI in the MC-group (p = 0.295). All parameters decreased four weeks after SIT cessation, but remained elevated from pre-training levels; the OC group showed more sustained training effects in V O2peak (OC -4.0%; MC -7.7%; p = 0.010). Conclusion: SIT improved peak exercise responses and TTF in recreationally-activewomen. However, OC use dampened V O2peak, Q peak and V O2p adaptation. OC use may reduce central adaptations to SIT in women without influencing exercise performance adaptations, possibly due to greater peripheral adaptation and the influence of exogenous oestradiol on the cardiovascular system and skeletal blood flow. A follow-up period indicated that OC users had spared V O2peak and TSI adaptations, suggesting OC use may influence the time course of physiological training adaptations. Therefore, OC use should be verified, controlled for, and considered when interpreting physiological adaptations to exercise training in women and further investigation is necessary to explain the apparent disparity between performance and physiological adaptations to training with OC use.