Walking Cadence during Moderate-Intensity Physical Activity in Pregnant Women.

Mallory Marshall,Beth Birchfield,Daphne Schmid,Christopher Ballmann,Madison Currie,Joyeuse Senga,Mckenna Persch,Rebecca Rogers

doi:10.3390/ijerph18126593

Abstract

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•kg−1•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.

Highlights

Current data indicate for the first time that the traditionally used 3 metabolic equivalents (METs) cutoff for moderate-intensity activity is appropriate for pregnant women despite metabolic alterations associated with pregnancy
The purpose of this study was to determine if the walking cadence equivalent to three METs in pregnant women is similar to non-pregnant populations
19.9 ± 4.1 weeks) and n = 10 3rd-trimester (27–40 weeks gestation; mean 31.5 ± 2.1 weeks) pregnant women were recruited via word of mouth, social media posts to the university neighborhood social network groups, and emails to the university community to participate in this study

Summary

Introduction

Walking cadence (steps/min) has been shown to effectively predict moderate-intensity (i.e., 3 MET) physical activity (PA) in the general population as well as in older adults. The heuristic (i.e., practical, rounded) value of 100 steps/min corresponds well to moderate-intensity PA [1,2,3,4,5,6]. Walking is the most commonly utilized form of PA during pregnancy [8,9], and has been shown to reduce possible risk factors of gestational diabetes [10,11], preeclampsia [12], and excessive gestational weight gain [13], and increase the likelihood of healthy birthweight for the offspring [14,15].

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Methods

Conclusion