Email updates

Keep up to date with the latest news and content from BMC Public Health and BioMed Central.

Open Access Research article

Agreement between pedometer and accelerometer in measuring physical activity in overweight and obese pregnant women

Tarja I Kinnunen123, Peter WG Tennant1, Catherine McParlin4, Lucilla Poston5, Stephen C Robson2 and Ruth Bell1*

Author Affiliations

1 Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK

2 Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK

3 School of Health Sciences, University of Tampere, Tampere, Finland

4 Newcastle upon Tyne Hospitals NHS Trust, Newcastle upon Tyne, UK

5 Maternal and Fetal Research Unit, King's College, London, UK

For all author emails, please log on.

BMC Public Health 2011, 11:501  doi:10.1186/1471-2458-11-501

Published: 27 June 2011

Abstract

Background

Inexpensive, reliable objective methods are needed to measure physical activity (PA) in large scale trials. This study compared the number of pedometer step counts with accelerometer data in pregnant women in free-living conditions to assess agreement between these measures.

Methods

Pregnant women (n = 58) with body mass index ≥25 kg/m2 at median 13 weeks' gestation wore a GT1M Actigraph accelerometer and a Yamax Digi-Walker CW-701 pedometer for four consecutive days. The Spearman rank correlation coefficients were determined between pedometer step counts and various accelerometer measures of PA. Total agreement between accelerometer and pedometer step counts was evaluated by determining the 95% limits of agreement estimated using a regression-based method. Agreement between the monitors in categorising participants as active or inactive was assessed by determining Kappa.

Results

Pedometer step counts correlated moderately (r = 0.36 to 0.54) with most accelerometer measures of PA. Overall step counts recorded by the pedometer and the accelerometer were not significantly different (medians 5961 vs. 5687 steps/day, p = 0.37). However, the 95% limits of agreement ranged from -2690 to 2656 steps/day for the mean step count value (6026 steps/day) and changed substantially over the range of values. Agreement between the monitors in categorising participants to active and inactive varied from moderate to good depending on the criteria adopted.

Conclusions

Despite statistically significant correlations and similar median step counts, the overall agreement between pedometer and accelerometer step counts was poor and varied with activity level. Pedometer and accelerometer steps cannot be used interchangeably in overweight and obese pregnant women.