The Validity and Reliability of Pedometers for Assessing Physical Activity in Children

Updated: Feb 26

November 2020

 

Introduction

With over a quarter (27%) of children aged between two to fifteen being classified as overweight or obese (Corrigan, and Scarlett, 2020), it is crucial that we understand the levels of physical activity in this population. As physical activity is a multi-dimensional construct, it is difficult to find a highly valid measure which applies to every mode of physical activity (Sylvia et al., 2013). And with each measure, there is also a difficulty in analysing the data to determine an individual’s level of physical activity. Blend this with inaccuracies in data collection, obtaining valid and reliable results can be challenging. This literature review aims to assess the validity and reliability of pedometers as a tool to measure levels of physical activity in children and make recommendations about the usefulness of these devices to researchers.

Purpose and Engineering of Pedometers

A pedometer is an instrument that counts the number of steps taken and may also attempt to estimate distance too. However, even with stride length adjustment, greater error is expected versus counting steps. Modern pedometers are clipped to a belt on the hip, or less commonly worn on the ankle (Montoye, et al., 1996).

Electronic pedometers involve a spring suspended, horizontal lever arm that moves up and down due to the vertical accelerations of the hip during walking and running. This consequentially opens and closes the electrical circuit, allowing the computer to count the number of steps taken, which is then presented on the digital display (Welk, 2002).


The Reliability of Pedometers for Measuring Steps

There are a variety of models of pedometer, each with their own proprietary mechanism and software, giving them varying levels of reliability. Schneider et al. (2003) tested ten pedometers over four-hundred metre walk, and found that the Kenz Lifecorder (KZ), New Lifestyles NL-2000 (NL) and the Yamax Digiwalker SW-701 (DW) were the most reliable, with values within ±3% of the actual steps taken, 95% of the time. Intra-model reliability was also remarkably high in these models (>0.99) and also the Omron HJ-105 (OM), However, the OM was the worst performing unit, along with the Sportline 330 (SL330)), with values over an order of magnitude lower than the best performing pedometers- within ±37% of the actual step value 95% of the time. Therefore, out of the ten pedometers tested, KZ, NL and DW are the most reliable- with OM being highly reliable also, but relatively inaccurate. Nevertheless, OM is a variable sensitivity pedometer, which was simply set at the middle setting. Calibrating this device to the correct sensitivity would likely yield more accurate results.

In children specifically, Mitre et al. (2009) found that in twenty-seven children aged eleven (±1) the OM and the Yamax Digi-Walker SW-200 (SW-200) pedometers were deemed inaccurate; underreporting step count- particularly at lower speeds and in children with a higher BMI. The study found that accelero