Abstract
High intensity interval training (HIIT) leads to improvements in maximal oxygen consumption (VO2max) in 2-weeks (Talanian, 2007). Long term (>4months) oral contraceptive use (OC) can decrease VO2max by 11% (Casazza, 2002). It is unknown whether OC can impair exercise training induced adaptations. Therefore, the purpose of this study was to investigate the effects of seven high intensity interval training (HIIT) sessions over 2 weeks on sub-maximal (submax) exercise responses and VO2max in women taking oral contraceptives. Methods Sixteen healthy women of average fitness, VO2max = 40.29 + 7.51 ml/kg/min, volunteered for this study. The participants were eight women who were taking a monophasic or triphasic OC for > 4 months and eight women who were regularly menstruating and not taking non-oral hormone based contraception were used as the cohort (NOC). Maximal and submax testing at (10% below VT1) were performed on a cycle ergometer pre and post HIIT. Statistical comparisons were made between OC and NOC to determine the physiological adaptations that occurred with HIIT. Results The NOC women had a significant decrease in submax heart rate (HRsub) (148 + 6.1 vs. 136 + 4.7 bpm, p=0.02), and an increase in submax oxygen pulse (O2pulsesub) (10.36 + 0.81 vs. 10.98 + 0.81 ml/bpm, p=0.02). The OC had a significant increase in submax diastolic blood pressure (dBPsub) (59.7 + 3.0 vs. 65.2 + 3.12 mmHg, p<0.01). There were no other significant differences between groups. Post HIIT maximal parameters significantly improved similarly in both groups. Absolute and relative VO2max increased 6.5% (2.6 + 0.1 vs. 2.8 + 0.1 L/min, p<0.01) (40.3 + 1.9 vs. 43.1 + 1.8 ml/kg/min, p<0.01), peak power increased 6% (226.5 + 10.37 vs. 241.5 + 9.2 W p< 0.01), and maximal oxygen pulse increased 9.3% (14.14 + 0.67 vs. 15.26 + 0.61 ml/beat). Conclusion Oral Contraceptive use alters sub-maximal cardiovascular training responses by blunting HRsub, dBPsub, and O2pulsesub adaptations to HIIT, without affecting submax, substrates utilized, or VO2max. The exogenous OC appear to alter sub-maximal cardiovascular function and hemodynamic HIIT training adaptations.