How to HIIT while pregnant? The protocol characteristics and effects of high intensity interval training implemented during pregnancy - A systematic review

There is strong scientific evidence that prenatal physical activity of moderate-to-high intensity is a prerequisite of the proper course of pregnancy, childbirth and fetus development. However, to date little data have been available on high intensity interval training (HIIT) performed during pregnancy. Following the PRISMA guidelines, this systematic review aimed at: first, to characterize HIIT protocols used or planned to be implemented during pregnancy; second, to determine their training effects on participant's health and obstetric outcomes. We included nine original works and three clinical trials in the analysis. The HIIT protocols substantially differed in terms of the training components (type, intensity, frequency, duration and progression) and the structure of intervals (intensity and time of workout and recovery intervals). Our most important finding is that performing HIIT during pregnancy is safe in terms of obstetric outcomes and well tolerated by pregnant participants, while providing them with the enjoyment of exercise. HIIT interventions either led to an improvement in selected maternal and fetal health parameters or had no impact. No adverse effects were observed. Pregnant women may benefit from HIIT programs in the same way as other populations. Evidence-based recommendations on prenatal HIIT should be developed and promoted worldwide among pregnant women, exercise and health professionals.