High-intensity interval aerobic exercise delays recovery from heart rate variability: a systematic review with meta-analysis.

PURPOSE

The present review investigates the responses of heart rate variability indices following high-intensity interval aerobic exercise, comparing it with moderate-intensity continuous exercise in adults, with the aim of informing clinical practice.

METHODS

Searches were conducted in four databases until March 2023. Eligible studies included randomized controlled trials that assessed heart rate variability indices such as the standard deviation of normal-to-normal heartbeat intervals (SDNN), the root mean square of successive differences (RMSSD), the proportion of the number of pairs of successive normal-to-normal (NN or R-R) intervals that differ by more than 50 ms (NN50) divided by the total number of NN intervals (pNN50), power in high frequency range (HF), power in low frequency range (LF), and LF/HF before and after high-intensity interval and moderate-intensity continuous aerobic exercise. The risk of bias in included studies was evaluated using the RoB 2 tool.

RESULTS

A total of 16 studies were included in the systematic review, while 9 were included in the meta-analysis. Overall, the majority of included individuals were healthy and young. Our meta-analysis indicated that individuals who performed high-intensity interval exercise showed a slower recovery to baseline levels for HF (standardized mean difference, SMD -0.98 [95% CI -1.52 to -0.44], p < 0.001) and LF (SMD -0.42 [95% CI -0.81 to -0.02], p = 0.04) within the first 10 min of recovery, which did not occur after 1 h. Among the 16 included studies, 10 had some concerns related to bias risk, while 6 were classified as high risk.

CONCLUSIONS

High-intensity interval aerobic exercise results in delayed recovery of HF and LF indices within the first 10 min after the session. However, our review indicates that healthy individuals restore modulation of the autonomic nervous system to baseline levels after this time interval, regardless of exercise intensity.