Metabolic rate prediction by massless actigraphy for outdoor activities

Purpose: In military scenarios, there is a need for a system that can enable identification of possible future injury during different activities that are considered to be physically strenuous. The purpose of the present study was to determine whether the use of an octagonal actigraph in conjunction with heart rate (fc) measurements could serve as an accurate method for metabolic rate estimation for different free-living activities in field settings. Methods: Twenty young healthy volunteers (10 men, 22 ± 3 years of age, and 10 women, 23 ± 3 years of age) participated in this study. All participants were exposed to six different activities (walking, running, sweeping, climbing and descending stairs, and shopping). Continuous actigraphic measurements were collected from the hip and wrist, fc was monitored with a Polar chest belt, and oxygen consumption (VO₂) was measured with a K4b² system. Results: A prediction model for VO₂ was constructed from actigraphic and fc measurements. Comparisons between predicted and measured VO₂ values revealed high correlations (hip, R² = 0.842; wrist, R ² = 0.822). Conclusions: This new prediction model highly correlated with VO₂ measurements. The hip was found to be more favorable than the wrist for assessment of VO₂ for different free-living activities.