Sprint interval training in the postpartum period maintains the enhanced cardiac output of pregnancy: A case study

During pregnancy an increased cardiac output ( $$ ) and blood volume (BV) occur to support fetal growth. Increased $$ and BV also occur during chronic endurance exercise training and benefit performance. We investigated if sprint interval training (SIT) undertaken early postpartum maintains the elevated $$ and BV of pregnancy and benefits performance. The participant, a competitive field hockey player and former cyclist, visited our laboratory at 2 weeks of gestation (baseline) and postpartum pre-, mid- and post-intervention (PP_pre, PP_mid and PP_post). Delivery was uncomplicated and she felt ready to start the SIT programme 5 weeks postpartum. Inert gas rebreathing was used to measure peak exercise $$ ( $$ _peak); $$ was measured with a metabolic cart; and postpartum haematological values were measured with carbon monoxide rebreathing. The 18 SIT sessions progressed from four to eight sprints at 130% of $$ peak power output. $$ _peak increased from baseline at all postpartum time points (baseline 16.2 vs. 17.5, 16.8 and 17.2 L/min at PP_pre, PP_mid and PP_post, respectively). Relative $$ remained below baseline values at all postpartum measurements (baseline 44.9 vs. 41.0, 42.3 and 42.5 mL/kg/min at PP_pre, PP_mid and PP_post, respectively) whereas absolute $$ rapidly reached baseline values postpartum (baseline 3.19 vs. 3.12, 3.23 and 3.18 L/min at PP_pre, PP_mid and PP_post, respectively). Postpartum BV (5257, 4271 and 5214 mL at PP_pre, PP_mid and PP_post, respectively) and Hb_mass (654, 525 and 641 g at PP_pre, PP_mid and PP_post, respectively) were similar between PP_pre and PP_post but decreased alongside $$ _peak at PP_mid. Peak power was returned to pre-pregnancy values by intervention end (302 vs. 303 W, baseline vs. PP_post). These findings show that SIT undertaken early postpartum defends the elevated $$ _peak of pregnancy and rapidly returns absolute $$ and peak power to baseline levels.