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Minimal Detectable Change Thresholds and Responsiveness of Zephyr Bioharness & Fitbit Charge Devices.

Nazari, Goris PT, MSc; MacDermid, Joy C. PT, PhD
Journal of Strength & Conditioning Research: Post Acceptance: July 18, 2017
doi: 10.1519/JSC.0000000000002136
Original Research: PDF Only

The aim of the current study was to define the MDC thresholds for Zephyr Bioharness (ZB) and Fitbit Charge (FC-HR) heart rate variables, and to establish the internal responsiveness of ZB and FC-HR devices in terms of their heart rate, respiratory rate variables and number of steps taken variables, in a healthy sample of males and females at resting, sub-maximal activity and throughout recovery phases. A total of sixty participants (30 females, 48 +/- 15) and (30 males, 48 +/- 15) were recruited using stratified convenience and snowball sampling approaches from our university student, staff and faculty population. At rest, MDC90 values of +/- 4.89 and +/- 5.15 were noted for ZB and FC-HR devices respectively. Throughout the recovery, thresholds of +/-8.14 for ZB and +/- 8.74 for FC-HR were reported. During the sub-maximal phases, scores of +/- 8.18 and +/- 9.35 were established for ZB and FC-HR respectively. From a resting to a sub-maximal state, the Standardized Response Means for ZB and FC-HR heart rate variables exhibited large responsiveness of SRMZB-HR=4.42; SRMFC-HR=4.04. In addition, the ZB respiratory rate variable showed the largest effect size of SRMZB-RR= 2.55. Similarly, large effect size of SRMFC-ST=1.76 were reported for the FC-HR steps taken variable. From a sub-maximal to a recovery state, he Standardized Response Means for ZB and FC-HR heart rate variables demonstrated effect sizes of SRMZBHR= -3.10; SRMFC-HR= -3.12). Furthermore, the ZB respiratory rate variable displayed similar internal responsiveness measures of SRMZB-RR= -2.45. To conclude, Similar MDC heart rate thresholds can be expected using the ZB and FC-HR devices, and that the two devices demonstrated large internal responsiveness in our healthy male and female cohort when transitioning from resting to submaximal states and vice-versa. Our findings suggest that the ZB and FC-HR devices can be used in monitoring performance improvements or deterioration over time, and would allow qualified personnel in assessing the effectiveness of exercise programs in healthy individuals.

Copyright (C) 2017 by the National Strength & Conditioning Association.