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

During pregnancy an increased cardiac output ( Q ̇ $\dot{Q}$ ) and blood volume (BV) occur to support fetal growth. Increased Q ̇ $\dot{Q}$ 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 Q ̇ $\dot{Q}$ 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 Q ̇ $\dot{Q}$ ( Q ̇ $\dot{Q}$ peak ); V ̇ O 2 peak ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{peak}}}}$ 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 V ̇ O 2 peak ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{peak}}}}$ peak power output. Q ̇ $\dot{Q}$ 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 V ̇ O 2 peak ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{peak}}}}$ 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 V ̇ O 2 peak ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{peak}}}}$ 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 Q ̇ $\dot{Q}$ 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 Q ̇ $\dot{Q}$ peak of pregnancy and rapidly returns absolute V ̇ O 2 peak ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{peak}}}}$ and peak power to baseline levels. HIGHLIGHTS: What is the central question of this study? Can the enhanced cardiac output of pregnancy be maintained with strenous exercise training undertaken early postpartum. What is the main finding and its importance? Baseline values of absolute oxygen consumption, peak power output and peak exercise cardiac output can be regained rapidly or surpassed following 6 weeks of sprint interval training postpartum. Sprint interval training can be used by endurance trained females to safely resume training early postpartum, allowing a rapid and efficient return to baseline fitness levels.