Accuracy of Wearable Devices for Measuring Heart Rate During Conventional and Nordic Walking

Introduction Nordic walking is being used increasingly as an exercise method in many clinical disorders. To apply Nordic walking in cases of fragile or deconditioned patients, monitoring of exercise intensity such as heart rate (HR) measurement is required. The accuracy of wearable HR monitors during Nordic walking has not yet been reported. Objective To compare the accuracy of an electrocardiography (ECG)–based HR monitor (Polar H7) and a photoplethysmography (PPG)–based HR monitor (Fitbit Charge 2) during conventional and Nordic walking. Design Accuracy was assessed by comparing the HR values obtained using the wearable devices with those obtained via 12‐lead ECG as a reference. Setting Laboratory setting. Participants Fifteen male volunteers age 23.7 ± 3.0 years. Interventions None. Main Outcomes Measures HR was simultaneously recorded via 12‐lead ECG, the Polar H7, and the Fitbit Charge 2 during conventional and Nordic walking. Agreement between the devices was assessed by calculating Lin's concordance correlation coefficient ( r c ), the mean absolute difference, and the limit of agreement (LoA) from Bland‐Altman plots. Results Regarding HR values including Nordic and conventional walking, there was a better agreement between the Polar H7 and the reference ( r c = 0.96) than between the Fitbit Charge 2 and the reference ( r c = 0.84). For the Polar H7, the mean absolute difference from the reference did not differ significantly between the walking methods; for the Fitbit Charge 2, the mean absolute difference was significantly higher during Nordic walking than during conventional walking (6.60 vs. 3.68 bpm, P < .001). The Fitbit Charge 2 had a wider LoA than did the Polar H7 during both walking methods. Conclusion ECG‐based wearable devices may be better than PPG‐based devices for monitoring HR during Nordic walking. However, both types of devices may adequately monitor HR during conventional walking.