Comparison of the Observed Heart Rate during Blood Lactate-based Exercise Intensity vs. Three Heart Rate-based Methods in Cardiovascular Rehabilitation

Background: Exercise intensity in cardiac rehabilitation is normally determined by heart rate (HR) based methods; however, these methods do not always reflect physiological demands. Purpose: The present study sought to contrast 3 different HR-based methods with the observed HR during cardiovascular rehabilitation sessions determined by blood lactate (BL) levels. Methods: Before and 6 weeks after beginning the exercise program, participants performed a submaximal graded exercise test to determine exercise intensities based on BL. Eleven subjects were continuously monitored during each session with wireless HR monitors to record peak and mean HR. Mean observed HR (HRobs) from 325 moderate-intensity sessions were compared to 3 HR-based methods: 60% of heart rate reserve (60% HRR), 80% of peak HR at cardiovascular stress test (80% HRpeak), and 70% of estimated maximal HR (70% HRmax). Results: There was a significant difference between groups where 60% HRR was the highest mean HR (134, SD = 7 bpm), followed by HRobs (mean 132, SD = 17 bpm), then 80% HRpeak (mean 122, SD = 5 bpm), and 70% HRmax (mean 120, SD = 5 bpm). All differences were significant at p < 0.05 except 80% HRpeak vs 70% HRmax. Conclusions: The results of the present study showed that HR-based methods for exercise intensity in cardiovascular rehabilitation are not associated with actual physiological demands.