Accuracy And Reliability Of A Commercial Group Fitness Heart Rate Monitor Across Exercise Intensity

PURPOSE: To determine the accuracy and reliability of a commercial group fitness heart rate (HR) monitor during an incremental test to exhaustion on a cycle ergometer. METHODS: Twenty recreationally-trained, college-aged males (mean ± SD age = 21.1 ± 1.9 years; body mass = 84.7 ± 15.0 kg; height = 181.2 ± 7.5 cm; aerobic training = 1.8 ± 1.9 hr·wk-1; resistance training = 6.2 ± 2.7 hr·wk-1) volunteered to complete an incremental test to exhaustion on a cycle ergometer that began at 80 W and increased 30 W every two minutes. A group fitness heart rate monitor was placed on the forearm as well as the upper arm of each subject with a 12-lead electrocardiogram (ECG) used as the criterion method. Heart rate was recorded from each device every 30 seconds and averaged across each two-minute stage. Subjects were provided strong verbal encouragement throughout the test to achieve their maximal exercise intensity (i.e. within 10 bpm of age-predicted maximum HR and rating of perceived exertion ≥18). Accuracy of each heart rate monitor was assessed through calculation of mean absolute percent error (MAPE), simple linear regression, and Bland-Altman plot. An intraclass correlation coefficient (ICC) was used to assess inter-device reliability. Statistical significance was set at an alpha level of 0.05. RESULTS: The MAPE (± SD) values were 0.9 (± 0.6)% and 0.8 (± 0.5)% for the forearm and the upper arm heart rate monitors, respectively. Linear regression analyses for ECG HR vs. forearm HR resulted in a strong correlation (r = 0.998) and standard error of estimate (SEE) value of 1.2 bpm, whereas ECG HR vs. upper arm HR resulted in a strong correlation (r = 0.999) and SEE value of 1.0 bpm. The mean (± SD) constant error (CE) (actual ECG HR - predicted HR) values were 1.0 (± 1.2) bpm and 0.8 (± 1.1) bpm for the forearm and upper arm, respectively. The Bland-Altman regression analyses (CE vs. ECG HR) resulted in a non-significant correlation for the forearm (r = 0.107, p = 0.268), but a significant correlation for the upper arm (r = 0.303, p < 0.001). The ICC for inter-device reliability between the forearm and upper arm monitors was R = 0.999. CONCLUSIONS: Our findings indicated the group fitness heart rate monitors placed on the forearm and upper arm provided highly accurate and reliable values when compared to an ECG from low to maximal exercise intensities.