As both Qpeak and Hbmass remained stable the increased VO2max likely stems from other physiological adaptations. Additionally, variability in study entry time, combined with cardio-haematological transitions from pregnancy, could account for the nonsignificant changes in haematological and Qpeak results. Breastfeeding may have influenced Q and PV. Six weeks of SIT rapidly improves cardiovascular fitness in previously trained women. Furthermore, in recreational and elite athletes, ergometer cycling SIT is well tolerated, can be started early postpartum, and does not impede breastfeeding.
Richard et al. (Tue,) studied this question.