Walking Cadence during Moderate-Intensity Physical Activity in Pregnant Women

Evidence has established that a cadence of 100 steps/min is indicative of the moderate intensity threshold of 3 metabolic equivalents (METs), but this has only been described in non-pregnant individuals. As metabolic alterations are well established during pregnancy, the purpose of this study was to determine if the walking cadence equivalent to 3 METs in pregnant women is similar to non-pregnant populations. Pregnant females (n = 29; age = 30.3 +/- 3.2 years, gestational age = 23.9 +/- 6.6 weeks) in their second or third trimester (>12 weeks gestation) completed three stages of treadmill walking for 5 min at different standardized walking speeds: 2.5, 3.0, and 3.5 miles per hour (mph). Oxygen consumption (VO2) and heart rate (HR) were measured each minute and METs were calculated for each stage. Real-time continuous monitoring of walking cadence was evaluated by an OptoGait gait analysis system. Following the three standardized speed stages, participants completed an additional stage walking at a speed that elicited 100 steps/min; VO2 and HR were also collected. A one-sample t-test was used to compare MET values at each stage to the heuristic 3 MET cutoff, and Pearson correlation coefficient was calculated to evaluate the relationship between cadence and METs. Mean cadence increased linearly across the three stages (2.5 mph = 103.7 +/- 4.5, 3.0 mph = 112.5 +/- 5.3, and 3.5 mph = 120.4 +/- 6.2 steps/min), as did METs (2.5 mph = 2.7 +/- 1.7, 3.0 mph = 3.2 +/- 0.8, and 3.5 mph = 4.3 +/- 1.8 METs) regardless of trimester. The average treadmill speed at which women walked at 100 steps/min was 2.4 +/- 0.4 mph which elicited an oxygen consumption of 9.5 mL center dot kg(-1)center dot min(-1), or 2.7 +/- 0.7 METs. There was no significant difference between METs at 3.0 mph and the conventional 3 MET cut point for moderate-intensity PA (p < 0.05). There was a moderate and significant relationship between METs and cadence (2nd trimester: r = 0.51; 3rd trimester: r = 0.42). Current data indicate for the first time that the traditionally used 3 MET cutoff for moderate-intensity activity is appropriate for pregnant women despite metabolic alterations associated with pregnancy. This may have important implications for exercise prescription in pregnant populations.

Automated summary

The study found that pregnant women have a similar walking cadence equivalent to 3 METs as non-pregnant populations, indicating that the traditional 3 MET cutoff for moderate-intensity activity is appropriate for pregnant women. There was a moderate and significant relationship between METs and cadence, suggesting that exercise prescription in pregnant populations can be based on established metabolic thresholds.