ABSTRACT
The purpose of this study was to compare the physiologic responses to low-impact aerobics
using treadmill walking as a control. Ten pregnant women between 21 and 28 weeks of
gestation completed 40 minutes of low-impact aerobic dance. The maternal and fetal
responses were then compared to 40 minutes of walking at the same heart rate. The
aerobics program consisted of a 10-minute warm-up, 20 minutes of high-intensity exercise,
and 10 minutes of decreasing intensity. Heart rates were recorded every 5 minutes,
and oxygen uptake (V·O2) and fetal response (real-time ultrasound) were obtained every 10 minutes. The maternal
heart rates were similar during both trials (overall, 133 ± 6 beat/min). V·O2 values during walking were about 4 mL/kg/min greater than during aerobic dance (p = ≤0.003). Minute ventilation (V·E) was also greater during walking (28.7 ± 6.4 versus
24.1 ± 3.4 L/min, p = 0.001). Respiratory exchange ratios and the ventilatory equivalents for oxygen
(V·E/V·O2) were similar for both trials. Aerobic dance caused greater fetal heart rates than
walking (p = ≤0.001), differences being as high as 25 beat/min. The fetal rates had returned
toward rest within 5 minutes following exercise. Low-impact aerobic dance, compared
with walking at similar heart rates, results in a lower maternal metabolic rate and
increases the transient stress on the fetus.
Keywords
Oxygen uptake - ventilation - fetal heart rate - exercise