Autonomic Responses to an Acute Bout of High-Intensity Body Weight Resistance Exercise vs. Treadmill Running.

The aim of this study was to compare postexercise autonomic nervous system (ANS) recovery between a high-intensity training protocol (HITP) and high-intensity treadmill running (TM) in 10 physically fit males. For each trial, ANS activity was measured through the heart rate variability markers of log-transformed square root of the successive R-R differences (lnRMSSD) and high frequency power (lnHF). These markers were analyzed in 5-minute segments at 5-10 minutes of the pre-exercise period (PRE) and during the postexercise period at 15-20 minutes (POST15-20min), 20-25 minutes (POST20-25min), 25-30 minutes (POST25-30min), and 1 hour (POST60min). Plasma epinephrine (E) and norepinephrine (NE) were also examined at PRE, immediately post exercise (IPE), 1-hour post (1HP), and 2-hour post (2HP). The results of this study demonstrate a significant overall time-dependent decreases in lnRMSSD and lnHF (p = 0.003 and 0.001, respectively) in both trials. Trial-dependent differences were also observed in postexercise lnRMSSD and lnHF measures, HITP being significantly lower than TM (p = 0.002 and 0.000, respectively). lnRMSSD at POST60min-HITP remained significantly lower compared to PRE (p ≤ 0.05). lnHF returned to baseline in HIPT and TM (p = 0.081 and 0.065, respectively). A time-dependent increase in E and NE was observed in both trials at time point IPE when compared to PRE (p ≤ 0.05). E at 1HP and 2HP returned to near resting levels (p = 0.62, p = 0.26), whereas NE remained slightly elevated in both groups (p = 0.003, p = 0.021). A trial-dependent increase was observed with the HITP eliciting a greater E response (p = 0.025) and NE response (p = 0.03). The HITP causes a greater disruption of the ANS than intensity-matched TM exercise.

The relationship between resting heart rate variability and heart rate recovery.

OBJECTIVE: There is limited research available regarding a possible relationship between resting heart rate variability (HRV) and post-exercise heart rate recovery (HRR). The aim of this study was to examine the relationship between resting HRV and HRR after maximal exercise. METHODS: Sixty-six college age men participated in this study. HRV was measured in a supine position before and for 30 min after a maximal exercise test on a treadmill. HRV was assessed in the time (i.e., SDNN) and frequency (i.e., normalized HF power [HFnu] and normalized LF:HF ratio [LFnu:HFnu]) domains. Heart rate was recorded at maximal exercise (MHR), and at 1- (HR1) and 2- (HR2) min of the cool-down recovery period. HRR was determined from the difference between MHR and HR1 (HRR1) and the difference between MHR and HR2 (HRR2). RESULTS: No significant relationship was found between resting HRV and HRR1 or HRR2. However, SDNN was significantly inversely correlated to MHR (P < 0.05), and HFnu was significantly inversely correlated to MHR (P < 0.01), HR1 (P < 0.01), and HR2 (P < 0.05). Furthermore, MHR accounted for the greatest variation in both SDNN and HFnu (P < 0.05). INTERPRETATION: Therefore, the HRV may not be related to the recovery of HR expressed as a slope (i.e., HRR) within 2 min following a maximal exercise test. This is possibly due to a significant inverse relationship between HRV and MHR, HR1 and HR2 post-maximal exercise.