Evaluation of a commercially available pedometer used to promote physical activity as part of a national programme

Abstract

Objective: To assess the accuracy of a pedometer (manufactured by Silva) currently being used as part of a national programme to promote physical activity in the UK.

Methods: Laboratory study: 68 participants (aged 19.2 years (SD 2.7), body mass index (BMI) 22.5 kg/m(2) (SD 3.3)) wore two Silva pedometers (over the right and left hips) while walking on a motorised treadmill at 2, 2.5, 3, 3.5 and 4 mph. Pedometer step counts were compared with actual steps counted. Free-living study: 134 participants (aged 36.4 years (SD 18.1), BMI 26.3 kg/m(2) (SD 5.1)) wore one Silva pedometer, one New-Lifestyles NL-1000 pedometer and an ActiGraph GT1M accelerometer (the criterion) during waking hours for one day. Step counts registered by the Silva and NL-1000 pedometers were compared with ActiGraph step counts. Percentage error of the pedometers were compared across normal-weight (n = 58), overweight (n = 45) and obese (n = 31) participants.

Results: Laboratory study: Across the speeds tested percentage error in steps ranged from 6.7 (4 mph) to 46.9% (2 mph). Free-living study: Overall percentage errors of the Silva and NL-1000 pedometers relative to the criterion were 36.3% and 9%, respectively. Significant differences in percentage error of the Silva pedometer were observed across BMI groups (normal-weight 21%, overweight 40.2%, obese 59.2%, p<0.001).

Conclusion: The findings suggest the Silva pedometer is unacceptably inaccurate for activity promotion purposes, particularly in overweight and obese adults. Pedometers are an excellent tool for activity promotion; however, the use of inexpensive, untested pedometers is not recommended as they will lead to user frustration, low intervention compliance and adverse reaction to the instrument, potentially impacting future public health campaigns.