Walk this way: validity evidence of iphone health application step count in laboratory and free-living conditions

Abstract

Several attempts have been made to demonstrate the accuracy of the iPhone pedometer function in laboratory test conditions. However, no studies have attempted to evaluate evidence of convergent validity of the iPhone step counts as a surveillance tool in the field. This study takes a pragmatic approach to evaluating Health application derived iPhone step counts by measuring accuracy of a standardized criterion iPhone SE and a heterogeneous sample of participant owned iPhones (6 or newer) in a laboratory condition, as well as comparing personal iPhones to accelerometer derived steps in a free-living test. During lab tests, criterion and personal iPhones differed from manually counted steps by a mean bias of less than ±5% when walking at 5km/h, 7.5km/h and 10km/h on a treadmill, which is generally considered acceptable for pedometers. In the free-living condition steps differed by a mean bias of 21.5% or 1340 steps/day when averaged across observation days. Researchers should be cautioned in considering the use of iPhone models as a research grade pedometer for physical activity surveillance or evaluation, likely due to the iPhone not being continually carried by participants; if compliance can be maximized then the iPhone might be suitable.

Designing meaningful outcome parameters using mobile technology: a new mobile application for telemonitoring of patients with heart failure

“…The observed compliance rate of >80% and mean wear time of 12.71 ± 1.13 h account for the validity of the measured step count. 22,23 Apart from activity monitoring, wrist-worn smart devices like the Apple Watch measure its wearer's heart rate via photoplethysmography. The observed underestimation and overestimation of high and low distances may at least in part be explained by the fact that the used iOS/watchOS devices have the highest accuracy at a pace of 5 km/h walking speed that is less good with slower walking pace.…”

“…The observed underestimation and overestimation of high and low distances may at least in part be explained by the fact that the used iOS/watchOS devices have the highest accuracy at a pace of 5 km/h walking speed that is less good with slower walking pace. 22,23 Apart from activity monitoring, wrist-worn smart devices like the Apple Watch measure its wearer's heart rate via photoplethysmography. For the Apple Watch 1, several trials give evidence of its good or very good accuracy in measuring heart rate under laboratory conditions.…”

Evaluating the Carrot Rewards app, a population-level incentive-based intervention promoting step counts across two Canadian provinces: a quasi-experimental study (Preprint)

“…In a free-living condition, steps were under-estimated by approximately 1,340 steps/day when averaged across observation days. [39] According to the study authors this likely reflects not carrying the iPhone continually throughout the day rather than inaccuracy in the step counting feature.…”

“…In a recent validation study of the iPhone step counting feature (version 6 or newer), it was found to be accurate in laboratory conditions [39]. In a free-living condition, steps were under-estimated by approximately 1,340 steps/day when averaged across observation days.…”

Existe influência do nível de atividade física habitual na capacidade aeróbia e variabilidade da frequência cardíaca em mulheres na fase da pós menopausa?

“…Inclusive, um estilo de vida menos ativo remete em problemas de saúde e está, certamente, relacionado com a diminuição dos passos diários de um indivíduo 4 , uma vez que, maior volume de passos diários é inversamente proporcional a obesidade em nível populacional 5 . Para avaliação dos passos diários, geralmente utiliza-se acelerômetros e pedômetros 6 , porém, o pedômetro tem sido usado com maior frequência por ter custo baixo e fácil aplicabilidade 7 . Assim, os passos diários monitorados por pedômetro demonstra-se como uma boa alternativa para controlar e avaliar de forma objetiva o NAFH 8 .…”