Abstract
Background:Many large studies have implemented wrist or thigh accelerometry to capture physical activity, but the accuracy of these measurements to infer activity energy expenditure (AEE) and consequently total energy expenditure (TEE) has not been demonstrated. The purpose of this study was to assess the validity of acceleration intensity at wrist and thigh sites as estimates of AEE and TEE under free-living conditions using a gold-standard criterion.Methods:Measurements for 193 UK adults (105 men, 88 women, aged 40–66 years, BMI 20.4–36.6 kg m−2) were collected with triaxial accelerometers worn on the dominant wrist, non-dominant wrist and thigh in free-living conditions for 9–14 days. In a subsample (50 men, 50 women) TEE was simultaneously assessed with doubly labelled water (DLW). AEE was estimated from non-dominant wrist using an established estimation model, and novel models were derived for dominant wrist and thigh in the non-DLW subsample. Agreement with both AEE and TEE from DLW was evaluated by mean bias, root mean squared error (RMSE), and Pearson correlation.Results:Mean TEE and AEE derived from DLW were 11.6 (2.3) MJ day−1 and 49.8 (16.3) kJ day−1 kg−1. Dominant and non-dominant wrist acceleration were highly correlated in free-living (r = 0.93), but less so with thigh (r = 0.73 and 0.66, respectively). Estimates of AEE were 48.6 (11.8) kJ day−1 kg−1 from dominant wrist, 48.6 (12.3) from non-dominant wrist, and 46.0 (10.1) from thigh; these agreed strongly with AEE (RMSE ~12.2 kJ day−1 kg−1, r ~ 0.71) with small mean biases at the population level (~6%). Only the thigh estimate was statistically significantly different from the criterion. When combining these AEE estimates with estimated REE, agreement was stronger with the criterion (RMSE ~1.0 MJ day−1, r ~ 0.90).Conclusions:In UK adults, acceleration measured at either wrist or thigh can be used to estimate population levels of AEE and TEE in free-living conditions with high precision.
Highlights
Supplementary information The online version of this article contains supplementary material, which is available to authorized users.Characterising the energy balance of individuals in freeliving conditions requires an accurate assessment of total energy expenditure
DLW doubly labelled water, BMI body mass index, TEE total energy expenditure, REE Resting energy expenditure, AEE activity energy expenditure, DIT Diet-Induced Thermogenesis, DW Dominant Wrist, NDW Non-Dominant Wrist, ENMO Euclidean Norm Minus One, HPFVM High-Pass Filtered Vector Magnitude used to characterise the relationship between the acceleration measurements and activity energy expenditure/total energy expenditure derived from doubly labelled water
We arrived at estimates that were moderately correlated with the criterion (r > 0.6) with small and nonsignificant mean biases at the population level from both wrists and root mean squared error (RMSE) of approximately 12 kJ day−1 kg−1
Summary
We evaluated the models in a large holdout sample (n = 645) and found that they explained 44– 47% of the variance in activity energy expenditure with no significant mean bias at the population level As this comparison was against a silver-standard measurement of activity volume, these estimation models could be more conclusively validated by integrating the estimated activity energy expenditure signal over time, and assessing agreement of activity volume with a gold-standard criterion such as doubly labelled water. The purpose of this study was to assess the validity of acceleration intensity at wrist and thigh sites as estimates of AEE and TEE under free-living conditions using a gold-standard criterion. Conclusions: In UK adults, acceleration measured at either wrist or thigh can be used to estimate population levels of AEE and TEE in free-living conditions with high precision
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