Maternal and fetal responses to acute high-intensity resistance exercise during pregnancy

Objective To examine maternal and fetal cardiovascular responses to high-intensity resistance exercise in pregnancy. Methods 10 healthy pregnant (26.4±3.2 weeks gestation) and 10 healthy non-pregnant individuals were recruited (34.8±6 and 33.5±2.9 years, respectively). At least 48 hours after baseline strength testing to determine 10-repetition maximum (10 RM), participants completed 10 repetitions of barbell back squat, bench press and deadlift at 70%, 80% and 90% of 10 RM with free breathing, followed by 10 repetitions at 90% 10 RM with a Valsalva manoeuvre. Maternal heart rate was monitored continuously. Fetal heart rate, umbilical systolic/diastolic (S/D) ratio, resistive index (RI) and pulsatility index (PI), as well as maternal blood pressure, glucose and lactate were assessed immediately before and after exercise. Results The amount of weight lifted and the rate of perceived exertion by pregnant and non-pregnant participants were similar throughout each exercise. Maternal heart rate increased with the amount of weight lifted, peaking with the use of the Valsalva manoeuvre (squat: 137.3±8.4 bpm; bench press: 110.5±10.4 bpm; deadlift: 130.7±9.0 bpm). Fetal bradycardia was not observed, and fetal heart rate did not change from pre-to-post exercise (squat: p=0.639; bench press: p=0.682; deadlift: p=0.847). Umbilical blood flow metrics, such as RI, remained within normal ranges throughout each set of squats (p=0.642), bench press (p=0.287) and deadlifts (p=0.614). Conclusion Our findings suggest that high-intensity resistance exercises are well tolerated by both mother and fetus, including while using the Valsalva manoeuvre. Data are available upon reasonable request.