Variable agreement between wearable heart rate monitors during exercise in cystic fibrosis

In people with cystic fibrosis (CF), greater cardiorespiratory fitness is associated with improved survival and quality of life. Wearable activity monitors are a popular method of monitoring exercise, with measures of heart rate used to indicate exercise intensity. We assessed the agreement of heart rate recordings obtained using the Fitbit Charge HR(™), Polar® H7 heart rate sensor and Masimo SET® Rad-5v pulse oximeter with the three-lead ECG during continuous and interval exercise. Adults with CF completed two exercise sessions, of 15-min duration per session, on a cycle ergometer while wearing the previously mentioned monitors. Firstly, participants cycled at 30% of estimated peak workload (W(peak)). Secondly, participants cycled at 1-min intervals at 60% of W(peak) interspersed with 2 min of unloaded cycling. Heart rate readings on all devices were recorded at minute intervals and their agreement was analysed using the Bland–Altman method. The Polar® H7 heart rate sensor had the best agreement with three-lead ECG, with a bias of 0±1 bpm during both continuous and interval exercise. The Masimo SET® Rad-5v pulse oximeter had good agreement, with a bias of 1±7 bpm and 1±5 bpm during continuous and interval exercise, respectively. The Fitbit Charge HR(™) demonstrated less agreement, with a bias of 9±17 bpm and 5±13 bpm during continuous and interval exercise, respectively. The Fitbit Charge HR(™) is not recommended for assessing heart rate during exercise in adults with CF. Findings support the use of the Polar® H7 for accurate heart rate monitoring.