Cardiac Autonomic Recovery Research Articles

The Effect of Different Resistance Training Protocols on Cardiac Autonomic Modulation During Exercise Recovery: A Crossover, Randomized, and Controlled Pilot Study

Purpose: This study investigated the impact of two different resistance training (RT) protocols on cardiac autonomic modulation during exercise recovery in trained individuals. It was hypothesized that a hypertrophic resistance training program would induce more significant stress and negatively affect cardiac autonomic modulation compared to a power/force resistance training program. Methods: Six healthy, trained participants (aged 18–40) were randomized in a crossover and controlled pilot study. Participants performed two RT protocols: (i) three sets of 10 repetitions with 85% of 10 RM, 60 s inter-set rest (3x1060s) and (ii) eight sets of three repetitions with 85% of 3 RM, 120 s inter-set rest (8x3120s). Heart rate variability (HRV) was measured before and 30 min after each RT session. Results: Significant reductions in HRV parameters (RMSSD, HF, and SD1) were observed following the 3x1060s protocol (hypertrophic design) compared to baseline. Conversely, the 8x3120s (power/force design) protocol did not show significant changes in HRV parameters. A significant interaction effect for time and RT protocol was found for all HRV measures with more significant reductions observed after 3x1060s compared to 8x3120s. Conclusions: The hypertrophic RT session (3x1060s) significantly reduced HRV parameters, suggesting higher physiological stress and potentially negative implications for cardiac autonomic recovery than the power/force RT session (8x3120s). These findings highlight the importance of considering exercise intensity and protocol design to manage cardiac autonomic stress during resistance training.

Influence of biological maturation on cardiac autonomic recovery in female volleyball players during & after repeated sprints training: An experimental trial

Previously, it was suggested that biological maturation (BM) could be linked to cardiac autonomic recovery (CAR) in the pediatric population. However, this influence hasn’t been confirmed yet. Our aim was to investigate the impact of BM on CAR in female volleyball players. Experimental study with a sample of 38 volleyball players, comprising 20 girls (age: [11.6 ​± ​2.1] years) and 18 women (age: [24.5 ​± ​5.5] years), we analyzed BM, comparing maturing subjects (girls) with mature subjects (women). Additionally, we assessed peak height velocity (PHV) in girls. We conducted a training session involving repeated sprints (3 rounds of 6 sprints interspersed by 5 ​min [min] of passive rest). Using short-range radio telemetry, we analyzed CAR during (at the end of the 1st and 2nd rounds) and after (following the 3rd round) the training session of repeated sprints by applying the 60-s to 300-s heart rate recovery index (HRR-Index). Girls exhibited superior CAR compared to women (round 2: 60-s, 120-s, 240-s, and 300-s, p ​< ​0.005). Subgroup analyses of BM indicated that individuals in the Late-PHV stage demonstrated superior CAR compared to those in the Early-PHV and During-PHV groups. (60-s to 300-s, η2p ​> ​0.4, p ​< ​0.05). Subjects in the During-PHV stage were superior to those in the Early-PHV stage (240-s á 300-s, η2p ​> ​0.4, p ​< ​0.05). We have concluded that biological maturation has a significant impact on cardiac autonomic recovery.

Influence of Cardiorespiratory Fitness on Cardiac Autonomic Recovery Among Active-Duty Firefighters.

Abstract Cornell, DJ, Flees, RJ, Shemelya, CM, and Ebersole, KT. Influence of cardiorespiratory fitness on cardiac autonomic recovery among active-duty firefighters. J Strength Cond Res 38(1): 66–73, 2024—It has been suggested that an inability of the autonomic nervous system (ANS) to recover after strenuous events is a potential cause of sudden cardiac death among firefighters. The purpose of this study was to examine the influence of cardiorespiratory fitness (CRF) on the heart rate recovery (HRR) kinetics of firefighters. Thirty-seven male career active-duty firefighters completed both a submaximal step test and a maximal treadmill graded exercise test. A monoexponential curve was fit to postexercise submaximal and maximal HRR data of each subject. Subjects were placed into Low CRF (n = 13) and High CRF (n = 24) groups based on the standard peak aerobic capacity (V̇O2peak) criterion of &lt;42 ml·kg−1·minute−1 and ≥42 ml·kg−1·minute−1, respectively. After controlling for age and body mass index, CRF was significantly (p &lt; 0.05) correlated with the decay rate ( ) and asymptote ( ) after submaximal exercise (r sp = −0.556; r sp = −0.637, respectively), as well as the , , and amplitude ( ) after maximal exercise (r sp = −0.353; r sp = −0.416; r sp = 0.603, respectively). High CRF firefighters demonstrated a significantly faster after both submaximal (p = 0.003) and maximal exercise (p = 0.043), a lower after submaximal exercise (p = 0.002), and a higher after maximal exercise (p = 0.001), than Low CRF firefighters. Greater CRF was associated with enhanced HRR kinetics after submaximal and maximal exertion, suggesting that CRF may positively influence the ANS recovery of firefighters.

Obesity does not impair time-course of cardiac autonomic recovery post-exercise in young men

Obesity does not impair time-course of cardiac autonomic recovery post-exercise in young men

Post-exercise heart rate variability recovery after 800-m endurance run load among Cameroonian adolescent's males

The 800-m (m) run is part of Physical Education classes in Cameroon, after which arrhythmias may occur during recovery. Hence, this study aimed at determining relationship between 800-m run loads on cardiac autonomic recovery among school adolescents.Forty-two male adolescents (aged [17 ​± ​1] years) performed 800-m. Post-exercise heart rate variability (HRV) was recorded during 5-min (min) (HRV5-min) and 15-min (HRV15-min) in time: Standard deviation of normal to normal (SDNN); Root mean square of successive differences (RMSSD) and frequency domain (LH: Low frequency, HF: High frequency, TP: Total power). Rating of Perceived Exertion (RPE) and blood lactate concentration (BLa) were measured after exercise. In HRV5-min, RPE was associated with SDNN (r ​= ​−0.44, p ​< ​0.01) and RMSSD (r ​= ​−0.38, p ​< ​0.05). BLa was correlated with SDNN (r ​= ​−0.38, p ​< ​0.05) and RMSSD (r ​= ​−0.56, p ​< ​0.001) in the time-domain, LF (r ​= ​−0.64, p ​< ​0.001), HF (r ​= ​−0.58, p ​< ​0.001) and TP (r ​= ​−0.61, p ​< ​0.001) in frequency-domain. Moreover, RPE was correlated with LF (r ​= ​−0.44, p ​< ​0.01), TP (r ​= ​−0.49, p ​< ​0.01) while exercise duration with HF (r ​= ​−0.38, p ​< ​0.05). In HRV15-min, BLa was correlated with RMSSD (r ​= ​−0.53, p ​< ​0.001) and SDNN (r ​= ​−0.68, p ​< ​0.001). RPE was negatively correlated SDNN (r ​= ​−0.53, p ​< ​0.01) and RMSSD (r ​= ​−0.44, p ​< ​0.01). BLa was associated with HF (r ​= ​−0.55, p ​< ​0.001), TP (r ​= ​−0.50, p ​< ​0.01) and RPE with LF (r ​= ​−0.51, p ​< ​0.01), HF (r ​= ​−0.50, p ​< ​0.01), TP (r ​= ​−0.49, p ​< ​0.01). In addition, exercise duration was negatively linked to HF (r ​= ​−0.36, p ​< ​0.05). This study outlined that in untrained adolescents an increase of 800-m loads is associated with a slow vagal indexes of HRV during the recovery.

Training History, Cardiac Autonomic Recovery from Submaximal Exercise and Associated Performance in Recreational Runners.

This study investigated the effect of prolonged exertion on cardiac parasympathetic (cPS) reorganization and associated aerobic performance in response to repeated short-lasting submaximal exercise bouts (SSE) performed for 7 days following prolonged exertion. In 19 recreational runners, heart rate (HR) and HR variability (HRV) indices (lnRMSSD, lnHF, and lnLF/HF) were monitored pre- and post-submaximal graded cycling performed on consecutive days following a half-marathon (HM) and compared with the baseline, pre-HM values. Additionally, HR recovery (HRR), aerobic performance, and rate of perceived exertion (RPE) were determined. HR, HRV indices, and HRR were tested for correlation with exercise performance. A significant time effect was found in HR, HRR, and HRV indices as well as in aerobic performance and RPE during the study period. Most of the measured parameters differed from their baseline values only on the same day following HM. However, HRR and HR measured in recovery after SSE were additionally affected one day following the half-marathon yet in opposite directions to those recorded on the same day as the HM. Thus, postSSE HR and HRR exhibited a bivariate time response (postSSE HR: 102 ± 14 bpm; p < 0.001; 82 ± 11 bpm; p = 0.007 vs. 88 ± 11 bpm; HRR in 30 s after SSE cessation: 14.9 ± 4.9 bpm; p < 0.001; 30.1 ± 13.3 bpm; p = 0.006 vs. 24.4 ± 10.8 bpm), potentially indicating a cPS dysfunction phase on the same day and cPS rebound phase one day following HM reflected also in consecutive changes in aerobic power. Correlations were found between the changes in measured cardiac indices with respect to baseline and the changes in aerobic performance indices throughout the study period. The effect of exercise history on cPS reorganization is more pronounced in response to SSE than at rest. Accordingly, we conclude that SSE performed repeatedly on a daily basis following prolonged exertion offers a noninvasive tool to evaluate the impact of training history on cPS recovery and associated aerobic power output in recreational athletes.

Effects of Acute Exercise on Cardiac Autonomic Response and Recovery in Non-Dialysis Chronic Kidney Disease Patients

ABSTRACT Purpose: Heart rate variability (HRV) has gained acceptance as a key marker of cardiovascular health. We compared HRV responses after continuous moderate-intensity exercise (CMIE) and high-intensity interval exercise (HIIE) matched for intensity and duration in individuals with midspectrum chronic kidney disease (CKD). Methods: Twenty men and women (age 62.0 ± 10 yrs.) diagnosed with CKD stages G3a and G3b participated in a 2 (condition) x 4 (time point) repeated cross-over measures design study. HRV time-domain indices were based on the standard deviation of all NN intervals (SDNN) and the square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD) and frequency domain. High-frequency (HF), low-frequency (LF), total power (TP) were examined. CMIE consisted of treadmill walking for 30 minutes at a 2% incline and speed corresponding to 60%–65% of reserve volume of oxygen (VO2R). HIIE included five intervals of 3 minutes at 90% of VO2R and 2 minutes at 20% VO2R intervals. Conditions were designed to be of the same average intensity (60% to 65% of VO2R) and caloric expenditure (~144 kcal). Results: Immediately following exercise SDNN, RMSSD, HF, LF, and TP were significantly lower compared to before exercise (p <.05). HRV responses were not different between conditions and conditions X time (p >.05). Conclusions: Thirty minutes of either CMIE or HIIE decreased HRV indices, pointing to an autonomic imbalance favoring vagal mediation. HRV’s responses regarding HIIE were no different from CMIE, therefore, from an autonomic function point of view this similarity may be useful for CKD exercise prescription and programming.

Effect of cryotherapy on post-exercise cardiac autonomic recovery in mixed martial arts (MMA) fighters: A Randomized Clinical Trial

Background: Cryotherapy brings benefits for muscle recovery and reduction of lactate thresholds in fighters; however, the effect of cryotherapy on the autonomous cardiac recovery (ACR) of wrestlers is not yet defined in the scientific literature. Objective: To analyze the effect of cryotherapy on ACR after simulated combat exercise in mixed martial arts (MMA) fighters. Methods: Crossover randomized clinical trial with a sample of 17 MMA fighters (male, age &gt;18 years). There was simulated combat of three rounds of MMA; each round lasted 5-min, there were the 60s between rounds. ACR was assessed by resting heart rate (RHR), which was monitored by a portable Polar-FT1® device. We measured RHR in the interval between the rounds at the 30s and 60s of rest in the conditions: without cryotherapy (Control), application of an ice pack in the thoracic region (TC); Immersion of feet in ice water (FC). Results: At 30-s of RHR, the control condition was better than FC to reduce RHR in rounds 1 and 2 (p&lt;0.05; η2p:0.28). At the 60s of RHR, the control condition was better than FC and TC (p&lt;0.05; η2p:0.32). The control condition had a better RHR recovery rate than the FC condition after rounds one (η2p: 0.23), two (η2p: 0.46), and three (η2p: 0.27) (p&lt;0.05). The TC condition did not show differences concerning the control and FC conditions. Conclusion: Cryotherapy applications in the thoracic region and by complete immersion of the feet did not generate significant effects on the ACR of MMA fighters.

Habitual aerobic exercise in healthy postmenopausal women does not augment basal cardiac autonomic activity yet modulates autonomic-metabolic interactions.

The aim of the present study was to examine the effects of habitual exercise training and metabolic health on basal cardiac autonomic function and cardiac autonomic recovery after exercise in healthy postmenopausal women (PMW). Habitually aerobically trained PMW (PMW-tr; 56 ± 1y; n = 11), and untrained PMW (PMW-un; 57 ± 1y; n = 13) and premenopausal women (PreM; ages 26 ± 1y; n = 14) were studied. Cardiac autonomic function, assessed using heart rate variability (HRV), was measured before and one hour after 45-minutes of moderate-intensity exercise (60% VO2peak). Fast Fourier frequency domain measures of high (HF; 0.15 Hz-0.4 Hz), low (LF; 0.04 Hz-0.15 Hz), very low (VLF; 0.01 Hz-0.04 Hz), and Total (VLF + LF + HF) HRV were assessed. Serum estradiol, insulin, and glucose were determined, and HOMA-IR, an index of insulin resistance, was calculated. In PMW groups, body composition and serum markers did not differ (P > 0.05). Pre-exercise, heart rate was lower (P < 0.05) in PMW-tr than PMW-un, yet HRV did not differ (P > 0.05). In PMW-tr only, HF was inversely associated (P < 0.05) with insulin (r = -0.738) and HOMA-IR (r = -0.758). In PreM, HRV was higher than PMW (P < 0.05) and was positively correlated with estradiol (P < 0.05). Postexercise, HRV was decreased within all groups (P < 0.05) yet remained higher in PreM (P < 0.05), and similar (P > 0.05) between PMW. Basal and postexercise HRV does not differ between habitually aerobically trained and untrained PMW. However, greater insulin sensitivity was associated with higher cardiac parasympathetic tone in trained PMW only. Exercise training may favorably modulate cardiac autonomic-metabolic interactions in PMW.

Cardiac autonomic recovery in response to aerobic versus resistance exercise in type 2 diabetes mellitus patients

Cardiac autonomic recovery in response to aerobic versus resistance exercise in type 2 diabetes mellitus patients

Green Exercise: Can Nature Video Benefit Isometric Exercise?

Green exercise is the combination of physical activity and nature exposure, which has been associated with positive effects on psychophysiological health. This study aimed to investigate the effects of nature video viewing on isometric exercise and find a useful practice for green exercise in urban living. In the current study, 18 male subjects were recruited in a randomized crossover trial and underwent a sequence of wall squat exercises. The whole experiment contained three periods of baseline (before exercise), exercise, and recovery (after exercise), and each period lasted for 2 min. A video of forest walking was played in the exercise and recovery periods as treatment, while a black screen was set as control. The Rate of Perceived Exertion Scale (RPE) and Feeling Scale (FS) were employed to measure perceived exertion and affective responses in the exercise period; heart rate (HR) and heart rate variability (HRV) including the standard deviation of normal-to-normal RR intervals (SDNN), the root mean square of successive differences (RMSSD), and the standard deviations of the Poincaré plot (SD1), were recorded in the three periods. Heart rate recovery (HRR) in the recovery period was further calculated based on 30 s and 60 s time frames. Results demonstrated that during the exercise period nature video viewing was associated with better affective responses (median of 1.00 and an interquartile (IQR) of 2.00, p = 0.017), lower perceived exertion (median = 6.00, IQR = 2.00, p = 0.021), and lower HR (median = 89.60, IQR = 20.94, p = 0.01), but the differences in HRV indices between the experimental settings were not statistically significant. In the recovery period, significantly higher values of RMSSD (median = 34.88, IQR = 24.52, p = 0.004), SD1 (median = 24.75, IQR = 17.41, p = 0.003), and HR (median = 84.18, IQR = 16.58, p = 0.001) were observed in the treatment setting, whereas no statistically significant difference was found for HRR. In general, our findings support that nature video viewing may help reduce perceived exertion, increase exercise pleasure, buffer heart rate, and improve cardiac autonomic recovery for wall squat exercising, which implies the potential of nature-based stimuli in green exercise. However, due to the limited research sample, further study may need to include female participants and focus on various populations to confirm the effectiveness of using virtual and environments depicting nature at home or in public exercise places to promote positive exercise experience.

Post-exercise cardiac autonomic and cardiovascular responses to heart rate-matched and work rate-matched hypoxic exercise

PurposeThis study investigated the effect of performing hypoxic exercise at the same heart rate (HR) or work rate (WR) as normoxic exercise on post-exercise autonomic and cardiovascular responses.MethodsThirteen men performed three interval-type exercise sessions (5 × 5-min; 1-min recovery): normoxic exercise at 80% of the WR at the first ventilatory threshold (N), hypoxic exercise (FiO2 = 14.2%) at the same WR as N (H-WR) and hypoxic exercise at the same HR as N (H-HR). Autonomic and cardiovascular assessments were conducted before and after exercise, both at rest and during active squat–stand manoeuvres (SS).ResultsCompared to N, H-WR elicited a higher HR response (≈ 83% vs ≈ 75%HRmax, p < 0.001) and H-HR a reduced exercise WR (− 21.1 ± 9.3%, p < 0.001). Cardiac parasympathetic indices were reduced 15 min after exercise and recovered within 60 min in N and H-HR, but not after H-WR (p < 0.05). H-WR altered cardiac baroreflex sensitivity (cBRS) both at rest and during SS (specifically in the control of blood pressure fall during standing phases) in the first 60 min after the exercise bout (p < 0.05). Post-exercise hypotension (PEH) did not occur in H-HR (p > 0.05) but lasted longer in H-WR than in N (p < 0.05).ConclusionsModerate HR-matched hypoxic exercise mimicked post-exercise autonomic responses of normoxic exercise without resulting in significant PEH. This may relate to the reduced WR and the limited associated mechanical/metabolic strain. Conversely, WR-matched hypoxic exercise impacted upon post-exercise autonomic and cardiovascular responses, delaying cardiac autonomic recovery, temporarily decreasing cBRS and evoking prolonged PEH.

Cardiac autonomic recovery following traditional and augmented remote ischemic preconditioning.

While the possible ergogenic benefits of remote ischemic preconditioning (RIPC) make it an attractive training modality, the mechanisms of action remain unclear. Alterations in neural tone have been demonstrated in conjunction with circulatory occlusion, yet investigation of the autonomic nervous system following RIPC treatment has received little attention. We sought to characterize alterations in autonomic balance to both RIPC and augmented RIPC (RIPCaug) performed while cycling, using acute and sustained autonomic indices. Thirteen participants (8M:5F) recorded baseline waking heart rate variability (HRV) for 5days prior to treatment. Participants then completed control exercise (CON), RIPC, and RIPCaug interventions in a randomized cross-over design. Cardiovascular measurements were recorded immediately before and after each intervention at rest, and during an orthostatic challenge. Waking HRV was repeated the morning after each intervention. RIPC resulted in acutely reduced resting heart rates (HR) (∆-4 ± 6bpm, P = 0.02) and suppressed HR 30s following the orthostatic challenge compared to CON (64 ± 10 vs 74 ± 9bpm, P = 0.003). RIPCaug yielded elevated HRs compared to CON and RIPC prior to (P = 0.003) and during the orthostatic challenge (P = 0.002). RIPCaug reduced LnSDNN (Baseline 4.39 ± 0.27; CON 4.44 ± 0.39; RIPC 4.41 ± 0.34; RIPCaug 4.22 ± 0.29, P = 0.02) and LnHfa power (Baseline 7.82 ± 0.54; CON 7.73 ± 1.11; RIPC 7.89 ± 0.78; RIPCaug 7.23 ± 0.87, P = 0.04) the morning after treatment compared to all other conditions. Our data suggest that RIPC may influence HR acutely, possibly through a reduction in cardiac sympathetic activity, and that RIPCaug reduces HRV through cardiac vagal withdrawal or increased cardiac sympathetic modulation, with alterations persisting until the following morning. These findings imply a dose-response relationship with potential for optimization of performance.

Does the number of sets in a resistance exercise session affect the fast and slow phases of post-exercise cardiac autonomic recovery?

Abstract Aims: The purpose of this study was to evaluate the acute effects of different resistance exercise (RE) volumes on postexercise cardiac autonomic modulation in men. Methods: Ten young men (25.5 ± 4.9 years, 24.8 ± 2.1 kg/m2) performed 3 trials of RE with 1, 2 or 3 sets (48-72 h between each trial) of 10-12 repetitions (70% of the one-maximum repetition) of bench press, leg press, and barbell row. Heart rate variability (HRV) was assessed at the 1st and 5th minutes of recovery (fast phase) and 3 consecutive 5-minute intervals from the 5th to 20th minute of recovery (slow phase). Parasympathetic and global modulations were assessed using the SD1 and SD2 indices of HRV, respectively. The comparison of the interventions was performed using the Friedman and Wilcoxon tests (p<0.05). Results: Lower parasympathetic modulation was identified after 2 and 3 sets compared to 1 set in both the fast and slow recovery phases (p= 0.004-0.05). Lower global modulation was identified after 3 sets compared to 1 set in both fast and slow recovery phases (p= 0.005-0.01). No differences in post-exercise parasympathetic and global modulation were observed between 2 and 3 sets. Conclusion: We concluded that 2 and 3 sets of RE compared to 1 set promoted higher autonomic reduction on the post-exercise phase, which should be considered by coaches when prescribing an RE program for untrained participants or intend to manipulate the postexercise organic recovery.

Cardiac Autonomic and Physiological Responses to Moderate- intensity Exercise in Hypoxia.

Exercise physiological responses can be markedly affected by acute hypoxia. We investigated cardiac autonomic and physiological responses to different hypoxic training protocols. Thirteen men performed three exercise sessions (5×5-min; 1-min passive recovery): normoxic exercise at 80% of the power output (PO) at the first ventilatory threshold (N), hypoxic exercise (FiO2=14.2%) with the same PO as N (HPO) and hypoxic exercise at the same heart rate (HR) as N (HHR). PO was lower in HHR (21.1±9.3%) compared to N and HPO. Mean HR was higher in HPO (154±11 bpm, p<0.01) than N and HHR (139±10 vs. 138±9 bpm; p=0.80). SpO2 was reduced (p<0.01) to a similar extent (p>0.05) in HPO and HHR compared to N. HR recovery (HRR) and HR variability indices were similar in N and HHR (p>0.05) but reduced in HPO (p<0.05), mirroring a delayed parasympathetic reactivation. Blood lactate and ventilation were similar in N and HHR (p>0.05) and increased in HPO (p<0.001). During recovery oxygen consumption and ventilation were similar in N and HHR (p>0.05) and increased in HPO (p<0.01). Moderate HR-matched hypoxic exercise triggers similar cardiac autonomic and physiological responses to normoxic exercise with a reduced mechanical load. On the contrary, the same absolute intensity exercise in hypoxia is associated with increased exercise-induced metabolic stress and delayed cardiac autonomic recovery.

Short-Term Cardiac Autonomic Recovery after a Repeated Sprint Test in Young Soccer Players.

The aim of this study was to describe the time course (within 2 h post-exercise) of heart rate variability (HRV) recovery following a traditional repeated sprint ability (RSA) test applied to youth soccer players. Twenty-four young soccer players (18.4 ± 0.5 years) undertook the following assessments: (1) 10 min rest in the seated position for HRV assessment; (2) a repeated sprint ability (RSA) test; (3) passive recovery in the seated position for 10 min, immediately after finishing the RSA test and 1 h and 2 h post-RSA test. During the HRV measurements (using the natural log of root mean square difference of successive normal RR intervals—lnRMSSD) the participants were instructed to assume a comfortable sitting position, remaining awake and breathing spontaneously for 10 min. Magnitude-based inference was used in the analyses. After the RSA test, the post-1 h measure was almost certainly lower than the resting measure, but almost certainly higher than the lnRMSSD measured post-RSA test. The lnRMSSD post-2 h was likely lower than the resting lnRMSSD and very likely higher than post-1 h. In conclusion, lnRMSSD is severely depressed after performing an RSA test, and reactivation is incomplete after 2 h of passive recovery. This result should be considered by practitioners when applying successive training sessions within intervals shorter than 2 h.

The elevation training mask induces modest hypoxaemia but does not affect heart rate variability during cycling in healthy adults.

This study examined the acute effects of the elevation training mask (ETM) on haemodynamics and heart rate variability (HRV) at rest, during cycling, and during recovery in healthy adults. Fifteen healthy male (N=9) and female (N=6) adults (27.0 ± 1.14 years) completed two trials with the mask (MASK) and without the mask (CON). The 40-minute cycling exercise protocol included 10-minute phases of (1) rest, (2) 50% of VO2peak cycling, (3) 70% of VO2peak cycling, and (4) recovery. Blood pressure and pulse oximetry saturation (SPO2) were measured at each phase. An Actiwave-Cardio ECG monitor (CamNtech, UK) was used to measure HRV variables including time and frequency domains. A greater response in systolic blood pressure (p=.035) was observed at rest while SPO2 (p=.033) was lower during high-intensity cycling (70% of VO2peak) in the MASK trial. The HRV indices were not different between trials during cycling. However, heart rate (p=.047) was greater while inter-beat interval and sympathovagal balance (the ratio between low-frequency and high-frequency components; ln LF/HF, p=.01) were lower in the MASK than the CON trials during recovery. Wearing an ETM during high-intensity cycling (70% of VO2peak) induces modest hypoxaemia. Although this device did not affect HRV changes during cycling, it seems to delay the cardiac-autonomic recovery from exercise. Healthy adults may be required to perform high-intensity exercise with an ETM to simulate a hypoxic environment, but future studies are needed to determine whether repeated exposure to this condition provides similar benefits as altitude training.

PO-189 Cardiac autonomic recovery from an acute bout of cardio pulmonary exercise test

Objective Heart rate variability (HRV) is a non-invasive clinical indicator of cardiovascular health, to date there has been little agreement on what HRV recovery following exercise. The present study aimed to evaluate the acute effects of cardio pulmonary exercise test (CPET) on cardiac autonomic activity in adolescent individuals.&#x0D; Methods Fifty-two healthy participants (Male=26, age: 20.31±1.49 years, height: 176±5.67 cm, body mass: 69.08±10.27 kg. Female=26, age: 20.62±0.98 years, height: 162.46±5.39 cm, body mass: 53.42±7.31 kg) underwent CEPT measurements of HRmax and VO2peak. Tests were performed on the Master Screen CPX model according to the Bruce protocol (JAEGER, Germany). Predicted peak heart rate was calculated as 220-age. HRV measurements were collected using the SphygmoCor device (AtCor Medical, Australia) at baseline, 5, 30 and 60 min after the CPET. Differences between groups were assessed using an independent t-test. The HRV variables were analyzed using a 2-factor [sex (male, female); time (Baseline, Post-5min, Post-30min, Post-60min)] repeated-measures ANOVA.&#x0D; Results There were significant differences in VO2peak (51.09±4.41 vs. 37.59±3.62 ml min-1 kg-1) (P&lt;0.05), RPE (ratings of perceived exertion)、RER (respiratory exchange ratio) were similar between groups (P&gt;0.05). There were significant increases (P&lt;0.01) in heart rate, markers of sympathetic activity (nLF) and sympathovagal balance (nLF/nHF) for 60 min after the CEPT trial, there were also significant decreases (P&lt;0.01) in markers of vagal tone (RMMSD, nHF) for 60 min. There were no significant interactions between groups from rest to recovery from maximal exercise for any HRV variables. The overall change in ln LF/HF was of greater proportion in male participants(P&lt;0.05) within 5 min.&#x0D; Conclusions Our findings indicate that the change of autonomic recovery was difference between male and female within 5 min, and it takes longer than 60 min to recover following an acute bout of CPET trial.

Delayed parasympathetic reactivation and sympathetic withdrawal following maximal cardiopulmonary exercise testing (CPET) in hypoxia.

This study investigated the effects of acute hypoxic exposure on post-exercise cardiac autonomic modulation following maximal cardiopulmonary exercise testing (CPET). Thirteen healthy men performed CPET and recovery in normoxia (N) and normobaric hypoxia (H) (FiO2 = 13.4%, ≈ 3500m). Post-exercise cardiac autonomic modulation was assessed during recovery (300s) through the analysis of fast-phase and slow-phase heart rate recovery (HRR) and heart rate variability (HRV) indices. Both short-term, T30 (mean difference (MD) 60.0s, 95% CI 18.2-101.8, p = 0.009, ES 1.01), and long-term, HRRt (MD 21.7s, 95% CI 4.1-39.3, p = 0.020, ES 0.64), time constants of HRR were higher in H. Fast-phase (30 and 60s) and slow-phase (300s) HRR indices were reduced in H either when expressed in bpm or in percentage of HRpeak (p < 0.05). Chronotropic reserve recovery was lower in H than in N at 30s (MD - 3.77%, 95% CI - 7.06 to - 0.49, p = 0.028, ES - 0.80) and at 60s (MD - 7.23%, 95% CI - 11.45 to - 3.01, p = 0.003, ES - 0.81), but not at 300s (p = 0.436). Concurrently, Ln-RMSSD was reduced in H at 60 and 90s (p < 0.01) but not at other time points during recovery (p > 0.05). Affected fast-phase, slow-phase HRR and HRV indices suggested delayed parasympathetic reactivation and sympathetic withdrawal after maximal exercise in hypoxia. However, a similar cardiac autonomic recovery was re-established within 5min after exercise cessation. These findings have several implications in cardiac autonomic recovery interpretation and in HR assessment in response to high-intensity hypoxic exercise.

Co-Existence of hypertension worsens post-exercise cardiac autonomic recovery in type 2 diabetes

BackgroundCardiac autonomic neuropathy (CAN) is a commonly overlooked complication of Type 2 Diabetes Mellitus (T2DM) characterized by imbalance between sympathetic and parasympathetic supply to the heart. The susceptibility of heart to dysrhythmias and fatal events increases during and after exercise due to a shift in autonomic regulation. Diabetes and hypertension (HTN) frequently occur concurrently and both conditions lead to impaired cardiac autonomic control. However, their impact together on post-exercise autonomic recovery remains to be explored. ObjectiveThe objective of the study was to investigate the effect of co-existence of HTN on cardiac autonomic recovery (assessed by heart rate recovery and heart rate variability) in patients with T2DM. MethodsForty eight type 2 diabetic patients (24 normotensive, 24 hypertensive), 24 non-diabetic patients with essential HTN, and 27 healthy controls, were recruited into the study and assessed for heart rate recovery (HRR) following a graded maximal test. Also, heart rate variability (HRV) was recorded before and following the bout of maximal exercise. ResultsHeart rate recovery at 1 (HRR1min) and 2 (HRR2min) minute(s) showed significant effects for DM (p < 0.001) and HTN (p < 0.001), while DM × HTN interaction was found to be non-significant. Resting HRV showed a significant decline in time-domain variables for the DM group (p < 0.01). Recovery of HRV showed a significant effect of time (p < 0.05) for all indices, the group effect was found significant only for time-domain measures (p < 0.05). ConclusionBoth HRR and HRV recovery were impaired in DM and HTN. Moreover, the co-existence of HTN had a synergistic effect, causing further worsening of autonomic recovery in T2DM.