Reliability of postexercise heart rate recovery.

Passive postexercise heart rate (HR) recovery is currently used in the assessment of endurance athletes to determine changes in performance or in the clinical setting as a predictor of all-cause mortality. The purpose of this investigation was to assess the reliability of HR recovery. Thirty healthy subjects performed two maximal and two submaximal treadmill exercises, followed by 5 minutes of passive recovery. HR signal was used to compute raw and Delta (exercise - recovery) HR after 1, 2, 3, and 5 minutes of exercise cessation. A mono-exponential function was fitted to the data using the least squares procedure. We found no significant bias between repeated measures. Relative reliability was lower for Delta HR when compared with raw HR (0.43 < ICC < 0.71 vs. 0.68 < ICC < 0.83, respectively). Absolute reliability was relatively constant over time for raw HR (SEM = approximately 8 %), while it decreased exponentially from the 1st (SEM = approximately 20 %) to the 5th minute of recovery (SEM = approximately 8 %) for Delta HR. The reliability of parameter estimates from exponential curve fitting was less consistent, since both ICC (0.43 to 0.88) and SEM (5.7 to 21.4 %) differed from one parameter to the other according to the intensity of exercise. We conclude that passive postexercise HR recovery reliability is heterogeneous. Raw HR is the desired method to describe it.