Validation of a Self-Monitoring Tool for Use in Exercise Therapy

Abstract Background Aerobic exercise at a subsymptom heart rate has been recommended as therapy for postconcussion syndrome. Assessing adherence with an accurate heart rate-monitoring instrument is difficult, limiting the proliferation of large-scale randomized controlled trials. Objective To evaluate the validity of the Fitbit Charge HR compared with electrocardiogram (EKG) to monitor heart rate during a treadmill-based exercise protocol. Design A methods comparison study. Setting Sports medicine research center within a tertiary care institution. Participants A convenience sample of 22 healthy participants (12 female) aged 18-26 years (mean age: 22 ± 2 years). Methods Fitbit Charge HR heart rate measurements were compared with EKG data concurrently collected while participants completed the Buffalo Concussion Treadmill Test. Main Outcome Measures Agreement between Fitbit Charge HR and EKG was assessed by intraclass correlation coefficients (ICC 3,1 ), Bland-Altman limits of agreement, and percent error. Results We observed a strong single-measure absolute agreement between Fitbit Charge HR and EKG (intraclass correlation coefficient=0.83; 95% confidence interval 0.67-0.90). Fitbit Charge HR underestimated heart rate compared with EKG (mean difference=−6.04 bpm; standard deviation=10.40 bpm; Bland-Altman 95% limits of agreement=−26.42 to 14.35 bpm). A total of 69.9% of Fitbit heart rate measurements were within 10% error compared with EKG, and 91.5% of all heart rate measurements were within 20% error. Conclusions Although the mean bias in measuring heart rate was relatively small, the limits of agreement between the Fitbit Charge HR and EKG were broad. Thus, the Fitbit Charge HR would not be a suitable option for monitoring heart rate within a narrow range. For the purposes of postconcussion exercise therapy, the relatively inexpensive cost, easy implementation, and low maintenance make Fitbit Charge HR a viable option for assessing adherence to an exercise program when expensive clinical equipment is unavailable. Level of Evidence II