Affordable fitness tracker step count, heart rate and calorie expenditure validation in controlled environment: a cross-sectional study

Obesity prevalence continues to increase globally, with increased physical activity considered as the most effective intervention. Fitness activity tracker have been shown to assist people increase their physical activity level, with increasing number of features and affordability over the past decade. An affordable fitness tracker, Archon Alive 001 was compared to Actigraph wGT3x-BT, with participants walking on treadmill at three, four, five and eight kilometers per hour (kph) and hand tally used as criterion measurement. Mean Absolute Percentage Error (MAPE) of Archon and Actigraph relative to hand tally at varying speeds, and related bivariate correlation were calculated, along with multivariate analysis of variance to assess the effect of speed and participant demographics on tracker MAPE. Polar OH1 heart rate monitor synchronized with PNOĒ metabolic analyzer was used to monitor heart rate and calorie expenditure. MAPE and correlation between PNOĒ and Archon calorie expenditure was calculated. Bland-Altman analysis and Intraclass Correlation Coefficient (ICC) was used to compare heart rate measurement between Polar and Archon. Compared to hand tally calculations, Archon step count was accurate, with average MAPE of 3.46%, and average correlation of r = 0.986, p < 0.001, while Actigraph average MAPE was 31.46%, with average correlation of r = 0.513, p = 0.001 at various speed. Age and speed had small effect on Archon’s accuracy. Sex had small effect, while speed had a large effect on Actigraph accuracy. Archon heart rate had Intraclass Correlation Coefficient (ICC) of 75.8%, with mean difference of -3.33 beats per minute (bpm) and 95% Limit of Agreement at -31.55 bpm to 24.90 bpm relative to Polar OH1. Archon total calorie expenditure output had 29.3% MAPE, and correlation r = 0.629, p < 0.001 relative to PNOĒ. Archon Alive demonstrated high accuracy in step counting, along with acceptable reliability and accuracy for heart rate and calorie expenditure measurements, making it sufficient for monitoring exercise intensity. Heart rate and calorie expenditure outputs were insufficiently accurate for clinical assessment.