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 (age 19.2±2.7 years, BMI 22.5±3.3 kg/m²) wore 2 Silva pedometers (over the right and left hips) whilst walking on a motorised treadmill at 2, 2.5, 3, 3.5 and 4mph. Pedometer step counts were compared with actual steps counted. Free-living study: 134 participants (age 36.4±18.1 years, BMI 26.3±5.1 kg/m²) 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 to ActiGraph step counts. Percent 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 percent error in steps ranged from 6.7 (4mph) – 46.9% (2mph). Free-living study: Overall percent errors of the Silva and NL-1000 pedometers relative to the criterion were 36.3% and 9% respectively. Significant differences in percent 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.