Effect of Ethnicity on Changes in VO2max and Cardiac Output in Response to Short-Term High Intensity Interval Training

Introduction: Prior data obtained in primarily Caucasian (C) and African American adults show that ethnicity does not mediate responsiveness to exercise training. It is unknown if Hispanics (H), who face elevated health risks and are less active than C, exhibit a similar response to exercise training. AIM: To determine if ethnicity alters physiological responses to high intensity interval training (HIIT) in C versus H women. METHODS: Twelve C and ten H women ages 19 - 35 yr who were healthy, non-obese, and inactive completed nine sessions of HIIT at 85 %PPO. Maximal oxygen uptake (VO2max), was assessed twice at baseline during which thoracic impedance was used to evaluate heart rate (HR), stroke volume (SV) and cardiac output (CO). Habitual physical activity was assessed during the study using accelerometry. RESULTS: Training elicited a heart rate equal to 89.8±3.3% HRmax, and 99.5% of sessions were completed. Results showed a significant main effect of training for VO2max in C and H (F =13.97, p =0.001), but there was no group by training interaction (p=0.65). There was also a main effect of training for CO and SV in C and H (F=7.57, p=0.012; F=7.16, p=0.022), yet post hoc analyses revealed significant increases were only exhibited in C. No main effect of training was seen in a-VO2diff across groups (F=1.32, p=0.26), but there was a large effect size seen in H (d=1.02). CONCLUSION: Data show no effect of ethnicity on changes in VO2max with HIIT, yet C and H may achieve this outcome differently. Longer studies in similar populations are needed to verify this result.