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

During pregnancy an increased cardiac output (Q̇Q̇) and blood volume (BV) occur to support fetal growth. Increased Q̇Q̇ 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 Q̇Q̇ 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 (PPpre, PPmid and PPpost). Delivery was uncomplicated and she felt ready to start the SIT programme 5 weeks postpartum. Inert gas rebreathing was used to measure peak exercise Q̇Q̇ (Q̇Q̇ peak) ; V̇O2peak{V̇{{₎₂}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 V̇O2peak{V̇{{₎₂}peak}} peak power output. Q̇Q̇ peak increased from baseline at all postpartum time points (baseline 16. 2 vs. 17. 5, 16. 8 and 17. 2 L/min at PPpre, PPmid and PPpost, respectively). Relative V̇O2peak{V̇{{₎₂}peak}} remained below baseline values at all postpartum measurements (baseline 44. 9 vs. 41. 0, 42. 3 and 42. 5 mL/kg/min at PPpre, PPmid and PPpost, respectively) whereas absolute V̇O2peak{V̇{{₎₂}peak}} rapidly reached baseline values postpartum (baseline 3. 19 vs. 3. 12, 3. 23 and 3. 18 L/min at PPpre, PPmid and PPpost, respectively). Postpartum BV (5257, 4271 and 5214 mL at PPpre, PPmid and PPpost, respectively) and Hbmass (654, 525 and 641 g at PPpre, PPmid and PPpost, respectively) were similar between PPpre and PPpost but decreased alongside Q̇Q̇ peak at PPmid. Peak power was returned to pre-pregnancy values by intervention end (302 vs. 303 W, baseline vs. PPpost). These findings show that SIT undertaken early postpartum defends the elevated Q̇Q̇ peak of pregnancy and rapidly returns absolute V̇O2peak{V̇{{₎₂}peak}} and peak power to baseline levels.