Effect of sprint interval training on circulatory function during exercise in sedentary, overweight/obese women

Very high-intensity, low-volume, sprint interval training (SIT) increases muscle oxidative capacity and may increase maximal oxygen uptake (\( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \)), but whether circulatory function is improved, and whether SIT is feasible in overweight/obese women is unknown. To examine the effects of SIT on \( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \) and circulatory function in sedentary, overweight/obese women. Twenty-eight women with BMI > 25 were randomly assigned to SIT or control (CON) groups. One week before pre-testing, subjects were familarized to \( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \) testing and the workload that elicited 50% \( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \) was calculated. Pre- and post-intervention, circulatory function was measured at 50% of the pre-intervention \( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \), and a GXT was performed to determine \( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \). During the intervention, SIT training was given for 3 days/week for 4 weeks. Training consisted of 4–7, 30-s sprints on a stationary cycle (5% body mass as resistance) with 4 min active recovery between sprints. CON maintained baseline physical activity. Post-intervention, heart rate (HR) was significantly lower and stroke volume (SV) significantly higher in SIT (−8.1 and 11.4%, respectively; P < 0.05) during cycling at 50% \( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \); changes in CON were not significant (3 and −4%, respectively). Changes in cardiac output (\( {\dot{\text{Q}}} \)) and arteriovenous oxygen content difference [(a − v)O₂ diff] were not significantly different for SIT or CON. The increase in \( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \) by SIT was significantly greater than by CON (12 vs. −1%). Changes by SIT and CON in HR_max (−1 vs. −1%) were not significantly different. Four weeks of SIT improve circulatory function during submaximal exercise and increases \( {\dot{V}\text{O}}_{{ 2 {\text{max}}}} \) in sedentary, overweight/obese women.