Delayed heart rate recovery and its variability in fitness functional training compared to endurance athletes: a...

The present study sought to expand upon prior investigations of the effect of different training modalities on post-exercise heart rate recovery (HRR) and heart rate variability (HRV).

To compare the HRR and HRV in physically active men with endurance and fitness functional training recreational athletes following maximal treadmill exercise testing.

We conducted a cross-sectional study with 53 healthy men split into a control group (CG: n = 15; physically active men), endurance group (EG: n = 16; recreational triathlon athletes), and fitness functional training group (FFG: n = 15; recreational fitness functional training athletes). Short-term (5 min) HRR and HRV indexes (SD1, SD2, and HR/LF) were analyzed in 1-minute segments throughout 5 mins of recovery immediately following maximal treadmill exercise testing. Statistical analysis employed a generalized linear model test with a p-value set at 5%.

FFG showed slower HRR than EG at all post-exercise time points (β =  - 13.74 to -8.83 bpm; p < 0.01-0.02) and lower HRR than CG at the 1st minute of recovery (β =  - 10.47 bpm; p = 0.03). The SD1 (cardiovagal reactivation) was lower in CG than EG at the 1 st (β =  - 0.84 ms; p = 0.02); however, no differences (p > 0.05) existed among all groups throughout the recovery period. The SD2 (overall cardiac autonomic modulation) was lower in FFG than EG at 2nd (β =  - 2.51 ms, p = 0.02) and 3rd (β =  - 3.20 ms, p = 0.03) minutes. FFG and EG showed higher values of HR/LF index (indicative of sympathetic activity) than CG at the 1 st minute (β = 432.38 to 1,104.49; p < 0.01). FFG also showed higher HR/LF activity than CG an EG at the 2nd and 3rd minutes of recovery (β = 60.48 to 205.31, p < 0.01 to 0.05), and at the 4th minute, than EG (β = 29.33; p = 0.05).

HRR was lower in FFG compared to EG throughout recovery. There were no differences in cardiovagal reactivation between the groups from the second to the fifth minute. FFG showed low cardiac overall modulation and high sympathetic activity throughout recovery compared to other groups. These findings may reflect that the FFG displays a persistent coactivation of both autonomic branches following maximal exercise testing compared to the different training modalities.