Assessment of parasympathetic reactivation after exercise

Castro FA, Costa EC, Boullosa D, Astorino TA. Affective valence predictors from real-world based short sprint interval training

Affective valence is typically positive at exercise intensities below the lactate threshold, yet more aversive responses occur at supra-threshold intensities. Nevertheless, the physiological and psychological predictors of affective valence during supramaximal intensities including short sprint interval training (sSIT) have not yet been elucidated. Seventeen (7 women/10 men) moderately active young adults (age ​= ​[28.2 ​± ​5.6] years;V ˙ O2max [maximum oxygen consumption] ​= ​[52.9 ​± ​8.1] mL·kg- 1·min- 1; BMI [body mass index] ​= ​[24 ​± ​2] kg·m- 2) completed four low-volume running sSIT sessions (10 ​× ​4 ​s efforts with 30 ​s of passive recovery). We recorded participants' heart rate (HR), root mean square of successive differences of normal RR intervals (RMSSD), heart rate recovery (HRR), ratings of perceived exertion (RPE), feeling scale (FS), intention and self-efficacy during, and after each session. Overall, no significant correlation (p ​> ​0.05) was found between FS and baseline clinical outcomes. No significant correlation (p ​> ​0.05) was detected between FS and any training parameter. No significant correlations were noted between FS and exercise task self-efficacy and intentions (p ​> ​0.05). The regression model was significant (F 3,61  ​= ​5.57; p ​= ​0.002) and only three variables significantly entered the generated model: ΔHRRend-120s end (p ​= ​0.002; VIF ​= ​2.58; 40.8%), time ≥ 90% HRpeak (p ​= ​0.001; VIF ​= ​1.26; 31.6%), and RMSSDend (p ​= ​0.025; VIF ​= ​2.23; 27.6%). These findings suggest that HR-based measures, particularly those related to in-task stress (time ≥ 90% HRpeak) and acute recovery (ΔHRRend-120s end, and RMSSDend), may predict affective valence during real-world sSIT.

Physical activity, fitness, and cardiac autonomic function among adults born postterm

Recent studies have suggested that adverse outcomes of postterm birth (≥42 completed weeks of gestation), including increased cardiometabolic risk factors, impaired glucose metabolism, and obesity, may extend into adulthood. We studied interconnected determinants of cardiovascular health, including physical activity (PA; based on accelerometry for 2 weeks), muscular strength (measured by handgrip strength), cardiorespiratory fitness (CRF; measured by 4-min step test), and cardiac autonomic function (heart rate [HR] recovery, HR variability, and baroreflex sensitivity) among 46-year-old adults from the Northern Finland Birth Cohort born postterm (n = 805) and at term (n = 2645). Adults born postterm undertook vigorous PA 2.0 min day-1 (95% CI, 0.4-3.7) less than term-born adults when adjusted for sex, age, and maternal- and pregnancy-related covariates in multiple linear regression. Postterm birth was associated with reduced CRF, based on a higher peak HR (2.1 bpm; 95% CI, 0.9-3.4) and slower HR recovery 30 s after the step test (-0.7 bpm; 95% CI, -1.3 to -0.1). Postterm birth was associated with less PA of vigorous intensity and CRF and slower HR recovery in middle age. Our findings reinforce previous suggestions that postterm birth should be included as a perinatal risk factor for adult cardiometabolic disease.

Posttraining Dry Cupping Treatment Elevates Heart Rate Variability in Taekwondo Athletes

ABSTRACT

Elite taekwondo (TKD) athletes require physical strength and mastery of complex techniques to excel in a highly competitive environment. This study aimed to investigate the effects of dry cupping posttraining on heart rate variability (HRV) and recovery in TKD athletes. Fourteen male TKD athletes participated in a crossover study and were randomly assigned to either a dry cupping (Group CUP) or a placebo group without cupping (Group PLA) after completing a standardized TKD-specific training program. A 28-day washout period was implemented between the two treatments to minimize potential carryover effects. HRV and rated perceived exertion (RPE) were evaluated at three-time points: before training (Pre), immediately after training (Post), and 30 min after rest or dry cupping (Post30) in both groups. The results indicated that heart rate (HR) at Post and Post30 was significantly higher than at Pre in both groups. Low frequency (LF) and the LF/high frequency (HF) ratio at Post were significantly elevated compared to Pre in both groups. However, at Post30, these values remained significantly higher in Group PLA but not in Group CUP. HF at Post was significantly reduced compared to Pre in both groups, but at Post30, this reduction persisted only in Group PLA and not in Group CUP. Significant differences in the levels of LF, HF, and the LF/HF ratio were observed between Group PLA and Group CUP at Post30. The CUP group also showed significantly lower RPE compared to the PLA group at Post30. In conclusion, dry cupping treatment after TKD training significantly improved HRV parameters and reduced perceived fatigue, suggesting its potential as an effective method for enhancing recovery in TKD athletes.

Investigating the Role of Exercise Pattern in Acute Cardiovagal Recovery

PURPOSE

Research on intermittent training has mainly focused on the effects of exercise intensity while overlooking the specific effect of the modulations associated with alternating exercise and recovery. This study investigated how the frequency of modulations during moderate-intensity exercise affects postexercise vagal reactivation.

METHODS

Healthy, active females and males 18-39 yr old were recruited for the study. Participants completed three treadmill running sessions on separate days. Each moderate-intensity session accumulated 30 min at 90% of the intensity associated with the second ventilatory threshold and was performed as either high-frequency intermittent (HiFi; 15 × [2 min + 2 min recovery]), low-frequency intermittent (LoFi; 5 × [6 min + 2 min recovery]), or moderate-intensity continuous training (MICT; 1 × 30 min). Heart rate recovery (HR rec ) at 1 min and heart rate variability recovery (HRV rec ; lnRMSSD) were assessed in response to submaximal constant-speed tests performed before (CST1) and after (CST2) each of the exercise sessions. HR rec , HRV rec , blood lactate (BLa), and blood pressure were also collected during the exercise sessions.

RESULTS

Twenty-one individuals (8 females, 13 males) participated in the study. HR rec from CST2 was faster in HiFi versus MICT ( P < 0.001), whereas HRV rec post-CST2 was higher after HiFi versus both LoFi ( P = 0.024) and MICT ( P < 0.001). BLa increased in all conditions ( P = 0.007) but remained lower during HiFi compared with LoFi and MICT (both P < 0.001). Diastolic blood pressure did not change during exercise with HiFi ( P = 0.939) but decreased during LoFi ( P = 0.006) and MICT ( P = 0.008).

CONCLUSIONS

Exercise pattern influences the physiologic response to exercise. Higher frequencies of modulations can preserve vagal activity and expedite postexercise recovery, suggesting moderate-intensity intermittent exercise as a potential strategy to mitigate autonomic impact and acute physiological stress while maintaining total work performed.

The effect of age on heart rate variability indices during and following high-intensity continuous exercise in masters and young cyclists

This study compared heart rate variability (HRV) parameters of cardiovascular autonomic regulation between well-trained masters and young cyclists at rest, during and following a continuous cycle (CTS) protocol. Ten masters (age = 56 ± 5 years) and eight young (age = 26 ± 3 years) cyclists completed a 100 min experimental protocol consisting of a 60 min CTS cycling bout at 95% of Ventilatory Threshold 2 followed by 40 min of supine recovery. Beat-to-beat heart rate was measured continuously, and HRV parameters analysed at standardised 5 min intervals during rest, exercise and recovery. The root mean square of the successive differences (RMSSD), low-frequency power and high-frequency power parameters were corrected by division of the R-R interval (time domain), or R-R interval squared (frequency domain). Further, the RMSSD and RMSSD:RR for successive 60-s R-R intervals at the onset (0-10 min) and offset (60-70 min) of CTS exercise were analysed over 10-min periods. The natural logarithm (Ln) of skewed parameters was taken for analysis. Significant interaction effects (P < 0.05) for 5 min segments were found for (LnRMSSD, LnRMSSD:RR, LnHF and LnHF:RR2. Masters cyclists demonstrated lower values of parasympathetic activity at rest and during recovery (15-20 min and 35-40 min) compared to younger cyclists. However, similar HRV responses were observed during exercise, including throughout the acute onset and offset periods (P > 0.05). This data shows that cardiac autonomic regulation during, or immediately following CTS exercise may not be influenced by age, but masters athletes may exhibit a lower baseline for parasympathetic activity.

Yoga vs. Static Stretching: Recovery Impact on Male Athletes' Post-HIIT Heart Rate, Respiratory Rate, Blood Pressure, and Heart Rate Variability Analysis

Heart rate and heart rate variability indicate an athlete's cardiovascular recovery and autonomic balance after intense exercise. While stretching aids recovery, its effects on autonomic balance are inconsistent. Yoga's combination of postures, breathing, and relaxation may further activate the parasympathetic system, making it a promising tool for sports recovery. This study employed a crossover design to examine the effects of yoga and stretching on post 30-min session of high-intensity interval training (HIIT) recovery in male athletes. Twenty athletes of Mae Fah Luang University (Age 20.95±0.99 years old, VO2max 42.53±4.79 ml/kg/min) were given recovery methods, 15-min stretching and 15-min yoga following HIIT. Heart rate, blood pressure, respiratory rate, and heart rate variability were evaluated immediately after HIIT, 5-min, 10- min, 15-min of the recovery period, and at 24-hour after recovery. A Two-way repeated-measures analysis of variance (ANOVA) was employed to examine the interaction effects between different methods and time of recovery. A significance level of 0.05 indicated a statistically significant difference. The findings indicated a statistically significant interaction between the group and time of heart rate variability and respiratory rate (p<0.05, effect size [ES] medium). Post-hoc analysis indicated that performing yoga showed a significantly lower respiratory rate at 5-min, 10-min, and 15-min compared to stretching (p<0.05, ES large). Yoga demonstrated a noteworthy enhancement in heart rate variability during the 5-min and 10-min recovery periods in comparison to stretching. In summary, this study provides empirical evidence supporting the efficacy of yoga as a post-exercise recovery strategy following high-intensity interval training. The role of breathing, rhythmic muscle contractions, and deep relaxation in yoga appears to facilitate the recovery phase more effectively than stretching alone. This suggests incorporating yoga as an active recovery regimen.

Recovery of heart rate and heart rate variability after a maximal cardiopulmonary exercise test in novice female runners

PURPOSE

Previous studies have shown delayed cardiac vagal reactivation after high-intensity endurance exercise when estimated with heart rate variability (HRV). However, the recovery dynamics of RR intervals (RRI) and HRV after a maximal incremental exercise test have been studied less in non-athletic population and especially in females. The main aim of the study was to examine the recovery dynamics of RRI and HRV immediately after a maximal cardiopulmonary exercise test (CPET) in adult females.

METHODS

Twenty-eight healthy, novice recreational female runners (33.7 ± 4.2 years) were selected to participate in this study from a larger group of participants (Run RCT). RRIs were collected continuously during a controlled rest, a CPET on a treadmill and a 15-min controlled, passive recovery. Minute-by-minute recovery dynamics were analyzed.

RESULTS

The dynamic phase of RRI and heart rate recovery (HRR) (from 192.2 ± 9.9 to 111.4 ± 2.4, P < 0.001) occurred during the first 4.5 min with HRR of 36 ± 10 beats during the first minute of the recovery. Resting heart rate was negatively associated (r =  - 0.53, P = 0.016) with HRR during the recovery. No recovery of root mean square of successive RRIs (RMSSD) was detected during the 15-min recovery. RMSSD was 15.0 ± 9.2% of resting values at the end of the recovery.

CONCLUSION

No recovery of vagal-derived HRV was detected immediately after a CPET in novice recreational female runners despite marked changes in sympathovagal balance, detected by rapid recovery of RRI during the first 5 min after exercise cessation.

Effects of voluntary exercise and electrical muscle stimulation on reaction time in the Go/No-Go task

INTRODUCTION

Acute exercise improves cognitive performance. However, it remains unclear what triggers cognitive improvement. Electrical muscle stimulation (EMS) facilitates the examination of physiological changes derived from peripheral muscle contraction during exercise. Thus, we compared the effects of EMS and voluntary exercise at low- or moderate-intensity on reaction time (RT) in a cognitive task to understand the contribution of central and peripheral physiological factors to RT improvement.

METHODS

Twenty-four young, healthy male participants performed a Go/No-Go task before and after EMS/exercise. In the EMS condition, EMS was applied to the lower limb muscles. In the low-intensity exercise condition, the participants cycled an ergometer while maintaining their heart rate (HR) at the similar level during EMS. In the moderate-intensity exercise condition, exercise intensity corresponded to ratings of perceived exertion of 13/20. The natural log-transformed root mean square of successive differences between adjacent inter-beat (R-R) intervals (LnRMSSD), which predominantly reflects parasympathetic HR modulation, was calculated before and during EMS/exercise.

RESULTS

RT improved following moderate-intensity exercise (p = 0.002, Cohen' d = 0.694), but not following EMS (p = 0.107, Cohen' d = 0.342) and low-intensity exercise (p = 0.076, Cohen' d = 0.380). Repeated measures correlation analysis revealed that RT was correlated with LnRMSSD (Rrm(23) = 0.599, p = 0.002) in the moderate-intensity exercise condition.

CONCLUSION

These findings suggest that the amount of central neural activity and exercise pressor reflex may be crucial for RT improvement. RT improvement following moderate-intensity exercise may, at least partly, be associated with enhanced sympathetic nervous system activity.

Heart rate variability: A primer for alcohol researchers

Problem alcohol drinking remains a major cost and burden for society. Also, rates of problem drinking in women have dramatically increased in recent decades, and women are at risk for more alcohol problems and comorbidities. The purpose of this commentary is to discuss the potential utility of cardiac measures, including heart rate (HR) and HR variability (HRV), as markers of individual and sex differences in the drive to drink alcohol. We recently used cardiac telemetry in female and male adult rats to determine whether different cardiac markers, including HR and HRV, would differently predict alcohol and anxiety-like behavior across the sexes. Indeed, female behaviors related to HRV measures that indicate more parasympathetic (PNS) influence (the "rest and digest" system). In contrast, male behaviors are associated more with sympathetic (SNS) indicators (the activation system). Remarkably, similar sex differences in PNS versus SNS engagement under challenge are seen in several human studies, suggesting strong cross-species convergence in differential autonomic regulation in females and males. Here, we describe the larger challenges that alcohol addiction presents, and how HRV measures may provide new biomarkers to help enhance development of more individualized and sex-specific treatments. We briefly explain the physiological systems underlying cardiac PNS and SNS states, and how specific HRV metrics are defined and validated, especially why particular HRV measures are considered to reflect more PNS versus SNS influence. Finally, we describe hormonal influences and sex differences in brain circuits related to cardiac autonomic regulation. Together, these findings show that HR and HRV have potential for uncovering key underlying mechanisms of sex and individual differences in autonomic drivers, which could guide more personalized treatment.

Effects of different extreme cold exposure on heart rate variability

Frequent extreme cold events in recent years have brought serious threats to outdoor workers and rescuers. Changes in ambient temperature are associated with altered cardiac autonomic function. The study aims to investigate heart rate variability (HRV) and its relationship to other physiological parameters under extreme cold exposures. Twelve males underwent a 30-min preconditioning phase in a neutral environment followed by a 30-min cold exposure (-5, -10, -15, and -20 °C). Time-domain indexes(meanRR, SDNN, RMSSD, and pNN50), frequency domain indexes [Log(HF), Log(LF), and low frequency/high frequency (LF/HF)], parasympathetic nervous system (PNS), and sympathetic nervous system (SNS) were analysed. Results showed all HRV indexes of four cold exposures were significant. The decrease in temperature was accompanied by progressive PNS activation with SNS retraction. SDNN was the most sensitive HRV index and had good linear relationships with blood pressure, pulse, and hand temperature. The results are significant for formulating safety protection strategies for workers in extremely cold environments.Practitioner Summary: This study investigated heart rate variability (HRV) in 12 males during a 30-min cold exposure (-5, -10, -15, and -20 °C). Results showed all HRV indexes of four cold exposures were significant. The decrease in temperature was accompanied by progressive PNS activation with SNS retraction. SDNN was the most sensitive HRV index and had good linear relationships with blood pressure, pulse, and hand temperature.

Effect of olfactory stimulation from aromatherapy on the autonomic nervous activity during aerobic exercises

Variations in the autonomic nervous system activity during exercise therapy in patients with cardiovascular diseases may lead to adverse events. Aromatherapy may reduce these adverse events by enhancing parasympathetic nervous activity (PNA). However, the effects of aromatherapy during exercise remain relatively unknown. This study aimed to evaluate the effect of aromatherapy on autonomic nervous activity during exercise and recovery. This randomized crossover study included 20 healthy men subjected to both aroma and placebo conditions which involved rest and moderate-intensity aerobic exercise on a cycle ergometer, followed by recovery. Blood pressure, heart rate variability indices, and SpO2 were measured during the rest, exercise, and recovery phases. Moreover, aroma preferences and emotional changes in response to the aroma were assessed. Under the placebo condition, high frequency (HF), root mean square of successive differences indices, and heart rate showed delayed recovery (P < 0.05). Furthermore, a moderate positive correlation was identified between aroma preference, pleasant emotions induced by aromatherapy, and the HF index (P < 0.05). These results indicate that aromatherapy facilitates the recovery of PNA after exercise. Furthermore, these effects were more pronounced among individuals who exhibited a stronger preference for and more positive emotions toward aromas.

Post-exercise heart rate recovery and its speed are associated with resting-reactivity cardiovagal modulation in healthy women

The present study sought to expand upon prior investigations of the relationship between post-exercise heart rate recovery (HRR) and cardiovagal resting-reactivity modulation. HRR from 1st to 5th min after maximal exercise test was correlated with a cardiovagal index of heart rate variability (SD1) at resting (supine and orthostatic positions) and its reactivity after the orthostatic stress test in 34 healthy women. Statistical analysis employed non-parametric tests with a p-value set at 5%. HRR, ∆%HRR, and coefficient of HRR (CHRR) at the 3rd and 5th min correlated with SD1 and SD1n (normalized units) in the supine position (rs = 0.36 to 0.47; p =  < 0.01). From the 1st to 5th min, HRR, ∆%HRR, and CHRR correlated with SD1 and SD1n in the orthostatic position (rs = 0.29 to 0.47; p =  ≤ 0.01 to 0.05), except for HRR at 5th min with SD1n (p = 0.06). Following the orthostatic stress test, HRR at 3rd and HRR, %∆HRR at 5th min correlated with ∆absSD1 (rs = 0.28 to 0.35; p = 0.02 to 0.05). All HRR measurements at 1st min correlated with ∆absSD1n (rs = 0.32 to 0.38; p = 0.01 to 0.03), and the CHRR at 1st min correlated with ∆%SD1(rs = 0.37; p = 0.01). After the sample was divided into high and low cardiovagal modulation subgroups, the subgroup with high modulation at rest (supine and orthostatic) and higher cardiovagal reactivity (reduction) showed faster HRR (p =  ≤ 0.01 to 0.05; ES:0.37 to 0.50). HRR throughout the 1st to 5th min positively correlates with cardiovagal modulation in the orthostatic position, and the 3rd and 5th min positively correlate with cardiovagal modulation in both postures at rest. Faster HRR following the maximal exercise test is associated with high resting-reactivity cardiovagal modulation in healthy women.

Influence of Respiratory Frequency of Slow-Paced Breathing on Vagally-Mediated Heart Rate Variability

Breathing techniques, particularly slow-paced breathing (SPB), have gained popularity among athletes due to their potential to enhance performance by increasing cardiac vagal activity (CVA), which in turn can help manage stress and regulate emotions. However, it is still unclear whether the frequency of SPB affects its effectiveness in increasing CVA. Therefore, this study aimed to investigate the effects of a brief SPB intervention (i.e., 5 min) on CVA using heart rate variability (HRV) measurement as an index. A total of 75 athletes (22 female; Mage = 22.32; age range = 19-31) participated in the study, attending one lab session where they performed six breathing exercises, including SPB at different frequencies (5 cycles per minute (cpm), 5.5 cpm, 6 cpm, 6.5 cpm, 7 cpm), and a control condition of spontaneous breathing. The study found that CVA was significantly higher in all SPB conditions compared to the control condition, as indexed by both root mean square of the successive differences (RMSSD) and low-frequency HRV (LF-HRVms2). Interestingly, LF-HRVms2 was more sensitive in differentiating the respiratory frequencies than RMSSD. These results suggest that SPB at a range of 5 cpm to 7 cpm can be an effective method to increase CVA and potentially improve stress management and emotion regulation in athletes. This short SPB exercise can be a simple yet useful tool for athletes to use during competitive scenarios and short breaks in competitions. Overall, these findings highlight the potential benefits of incorporating SPB into athletes' training and competition routines.

Heart rate dynamics and asymmetry during sympathetic activity stimulation and post-stimulation recovery in ski mountaineers-a pilot exploratory study

There is a lack of studies on non-linear heart rate (HR) variability in athletes. We aimed to assess the usefulness of short-term HR dynamics and asymmetry parameters to evaluate the neural modulation of cardiac activity based on non-stationary RR interval series by studying their changes during sympathetic nervous system activity stimulation (isometric handgrip test) and post-stimulation recovery in professional ski mountaineers. The correlation between the changes in the parameters and the respiratory rate (RespRate) and also the duration of the career was analyzed. Short-term (5 min) and ultra-short-term (1 min) rates of patterns with no variations (0V), number of acceleration runs of length 1 (AR1), and short-term Porta's Index were greater, whereas Guzik's Index (GI) was smaller during sympathetic stimulation compared to rest. GI increased and the number of AR1 decreased during recovery. Greater increases in GI and RMSSD were associated with greater decreases in RespRate during recovery. Greater increases in RespRate from rest to short-term sympathetic stimulation were associated with greater increases in 0V (Max-min method) and AR1 but also with greater decreases in decelerations of short-term variance and accelerations and decelerations of long-term variance. Greater increases in 0V (Max-min method) and number of AR1 during sympathetic stimulation were associated with a shorter career duration. Greater decreases in these parameters during recovery were associated with a longer career duration. Changes in measures of HR dynamics and asymmetry, calculated based on short-term non-stationary RRi time series induced by sympathetic stimulation and post-stimulation recovery, reflected sympathovagal shift and were associated with condition-related alterations in RespRate and career duration in athletes who practice ski mountaineering.

The neuromodulatory role of dopamine in improved reaction time by acute cardiovascular exercise

Acute cardiovascular physical exercise improves cognitive performance, as evidenced by a reduction in reaction time (RT). However, the mechanistic understanding of how this occurs is elusive and has not been rigorously investigated in humans. Here, using positron emission tomography (PET) with [11 C]raclopride, in a multi-experiment study we investigated whether acute exercise releases endogenous dopamine (DA) in the brain. We hypothesized that acute exercise augments the brain DA system, and that RT improvement is correlated with this endogenous DA release. The PET study (Experiment 1: n = 16) demonstrated that acute physical exercise released endogenous DA, and that endogenous DA release was correlated with improvements in RT of the Go/No-Go task. Thereafter, using two electrical muscle stimulation (EMS) studies (Experiments 2 and 3: n = 18 and 22 respectively), we investigated what triggers RT improvement. The EMS studies indicated that EMS with moderate arm cranking improved RT, but RT was not improved following EMS alone or EMS combined with no load arm cranking. The novel mechanistic findings from these experiments are: (1) endogenous DA appears to be an important neuromodulator for RT improvement and (2) RT is only altered when exercise is associated with central signals from higher brain centres. Our findings explain how humans rapidly alter their behaviour using neuromodulatory systems and have significant implications for promotion of cognitive health. KEY POINTS: Acute cardiovascular exercise improves cognitive performance, as evidenced by a reduction in reaction time (RT). However, the mechanistic understanding of how this occurs is elusive and has not been rigorously investigated in humans. Using the neurochemical specificity of [11 C]raclopride positron emission tomography, we demonstrated that acute supine cycling released endogenous dopamine (DA), and that this release was correlated with improved RT. Additional electrical muscle stimulation studies demonstrated that peripherally driven muscle contractions (i.e. exercise) were insufficient to improve RT. The current study suggests that endogenous DA is an important neuromodulator for RT improvement, and that RT is only altered when exercise is associated with central signals from higher brain centres.

Attenuated peripheral oxygen extraction and greater cardiac output in women with posttraumatic stress disorder during exercise

Posttraumatic stress disorder (PTSD) is associated with an increased risk of developing cardiovascular disease, especially in women. Evidence indicates that men with PTSD exhibit lower maximal oxygen uptake (V̇o2max) relative to controls; however, whether V̇o2max is blunted in women with PTSD remains unknown. Furthermore, it is unclear what determinants (i.e., central and/or peripheral) of V̇o2max are impacted by PTSD. Therefore, we evaluated the central (i.e., cardiac output; Q̇c) and peripheral (i.e., arteriovenous oxygen difference) determinants of V̇o2max in women with PTSD; hypothesizing that V̇o2max would be lower in women with PTSD compared with women without PTSD (controls), primarily due to smaller increases in stroke volume (SV), and therefore Q̇c. Oxygen uptake (V̇o2), heart rate (HR), Q̇c, SV, and arteriovenous oxygen difference were measured in women with PTSD (n = 14; mean [SD]: 43 [11] yr,) and controls (n = 17; 45 [11] yr) at rest, and during an incremental maximal treadmill exercise test, and the Q̇c/V̇o2 slope was calculated. V̇o2max was not different between women with and without PTSD (24.3 [5.6] vs. 26.4 [5.0] mL/kg/min; P = 0.265). However, women with PTSD had higher Q̇c [P = 0.002; primarily due to greater SV (P = 0.069), not HR (P = 0.285)], and lower arteriovenous oxygen difference (P = 0.002) throughout exercise compared with controls. Furthermore, the Q̇c/V̇o2 slope was steeper in women with PTSD relative to controls (6.6 [1.4] vs. 5.7 [1.0] AU; P = 0.033). Following maximal exercise, women with PTSD exhibited slower HR recovery than controls (P = 0.046). Thus, despite attenuated peripheral oxygen extraction, V̇o2max is not reduced in women with PTSD, likely due to larger increases in Q̇c.NEW & NOTEWORTHY The current study indicates that V̇o2max is not different between women with and without PTSD; however, women with PTSD exhibit blunted peripheral extraction of oxygen, thus requiring an increase in Q̇c to meet metabolic demand during exercise. Furthermore, following exercise, women with PTSD demonstrate impaired autonomic cardiovascular control relative to sedentary controls. We interpret these data to indicate that women with PTSD demonstrate aberrant cardiovascular responses during and immediately following fatiguing exercise.

Augmented sympathoexcitation slows postexercise heart rate recovery

Slow heart rate recovery following exercise may be influenced by persistent sympathoexcitation. This study examined 1) the effect of muscle metaboreflex activation (MMA) on heart rate recovery following dynamic exercise; and 2) whether the effect of MMA on heart rate recovery is reversible by reducing sympathoexcitation [baroreflex activation via phenylephrine (PE)] in canines. Twenty-two young adults completed control and MMA protocols during cycle ergometry at 110% ventilatory threshold with 5 min recovery. Heart rate recovery kinetics [tau (τ), amplitude, end-exercise, and end-recovery heart rate] and root mean square of successive differences (RMSSD) were measured. Five chronically instrumented canines completed control, MMA (50%-60% imposed reduction in hindlimb blood flow), and MMA with end-exercise PE infusion (MMA + PE) protocols during moderate exercise (6.4 km·h-1) and 3 min recovery. Heart rate recovery kinetics and MAP were measured. MAP increased during MMA versus control in canines (P < 0.001). Heart rate recovery τ was slower during MMA versus control in humans (17% slower; P = 0.011) and canines (150% slower; P = 0.002). Heart rate recovery τ was faster during MMA + PE versus MMA (40% faster; P = 0.034) and was similar to control in canines (P = 0.426). Amplitude, end-exercise, and end-recovery heart rate were similar between conditions in humans (all P ≥ 0.122) and in canines (all P ≥ 0.084). MMA decreased RMSSD in early recovery (P = 0.004). MMA-induced sympathoexcitation slows heart rate recovery and this effect is markedly attenuated with PE. Therefore, elevated sympathoexcitation via MMA impairs heart rate recovery and inhibition of this stimulus normalizes, in part, heart rate recovery.NEW & NOTEWORTHY Augmented sympathoexcitation, via muscle metaboreflex activation, functionally slows heart rate recovery in both young healthy adults and chronically instrumented canines. Furthermore, elevated sympathoexcitation corresponded with lower parasympathetic activity, as assessed by heart rate variability, during the first 3 min of recovery. Finally, sympathoinhibition, via phenylephrine infusion, normalizes heart rate recovery during muscle metaboreflex activation.

Student arousal, engagement, and emotion relative to Physical Education periods in school

BACKGROUND

Exercise has transient effects on cognition and mood, however the impact of Physical Education (PE) on cognitive and affective processes across the school day has not been examined.

METHOD

This study used wearables and questionnaires to track student arousal, engagement, and emotion across school days/periods following PE. Skin conductance, heart rate, heart rate variability, and self-reported engagement, arousal, and valence were analyzed for 23 students (age 15-17 years) on days with and without PE.

RESULTS

Sympathetic arousal was significantly higher for two hours following PE and there were stronger decreases in arousal across other classes relative to days without PE. On days with PE, engagement decreased, whereas valence increased from morning to afternoon.

CONCLUSION

These findings highlight the importance of considering acute effects of PE on learning across the entire school day, and demonstrates the feasibility of wearables to clarify how the timing of PE could positively or negatively affect self-regulation and learning.

Long-term association of ultra-short heart rate variability with cardiovascular events

Heart rate variability (HRV) is a cardiac autonomic marker with predictive value in cardiac patients. Ultra-short HRV (usHRV) can be measured at scale using standard and wearable ECGs, but its association with cardiovascular events in the general population is undetermined. We aimed to validate usHRV measured using ≤ 15-s ECGs (using RMSSD, SDSD and PHF indices) and investigate its association with atrial fibrillation, major adverse cardiac events, stroke and mortality in individuals without cardiovascular disease. In the National Survey for Health and Development (n = 1337 participants), agreement between 15-s and 6-min HRV, assessed with correlation analysis and Bland-Altman plots, was very good for RMSSD and SDSD and good for PHF. In the UK Biobank (n = 51,628 participants, 64% male, median age 58), after a median follow-up of 11.5 (11.4-11.7) years, incidence of outcomes ranged between 1.7% and 4.3%. Non-linear Cox regression analysis showed that reduced usHRV from 15-, 10- and 5-s ECGs was associated with all outcomes. Individuals with low usHRV (< 20th percentile) had hazard ratios for outcomes between 1.16 and 1.29, p < 0.05, with respect to the reference group. In conclusion, usHRV from ≤ 15-s ECGs correlates with standard short-term HRV and predicts increased risk of cardiovascular events in a large population-representative cohort.

Effects of remote ischemic conditioning on conditioned pain modulation and cardiac autonomic modulation in women with knee osteoarthritis: placebo-controlled randomized clinical trial protocol

BACKGROUND

It is estimated that over 240 million people worldwide have osteoarthritis, which is a major contributor to chronic pain and central changes in pain processing, including endogenous pain modulation. The autonomic nervous system plays a crucial role in the pain regulatory process. One of the main mechanisms of remote ischemic conditioning is neuronal signaling from the preconditioned extremity to the heart. This study aims to analyze the acute effect of remote ischemic conditioning on local pain, conditioned pain modulation, and cardiac autonomic control in women with knee osteoarthritis and to see if there is a correlation between them.

METHODS

Women more than 50 years with knee osteoarthritis diagnosed according to the American College of Rheumatology criteria in the postmenopausal period will be considered eligible. The study will have blind randomization, be placebo-controlled, and be balanced in a 1:1 ratio. The total of 44 participants will be divided into two groups (22 participants per group): (i) remote ischemic conditioning and (ii) placebo remote ischemic conditioning. Protocol consisting of four cycles of total ischemia, followed immediately by four cycles of 5 min of vascular reperfusion, totaling 40 min. The primary outcomes in the protocol are conditioned pain modulation, which has the pressure pain threshold (kgf/cm2) as its primary outcome measure, and cardiac autonomic modulation, which has the indices found in heart rate variability as its primary outcome measure. Comparisons will be performed using generalized linear mixed models fitted to the data. For correlation, the Pearson or Spearman test will be used depending on the normality of the data. All analyses will assume a significance level of p < 0.05.

DISCUSSION

It is believed that the results of this study will present a new perspective on the interaction between the pain processing system and the cardiovascular system; they will provide the professional and the patient with a greater guarantee of cardiovascular safety in the use of the intervention; it will provide knowledge about acute responses and this will allow future chronic intervention strategies that aim to be used in the clinical environment, inserted in the multimodal approach, for the treatment of osteoarthritis of the knee.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05059652. Registered on 30 August 2021. Last update on 28 March 2023.

Physiological response and physical performance after 40 min and 90 min daytime nap opportunities

This study aimed to examine the impact of 40-min and 90-min naps on performance in the 5-m shuttle run test (5mSRT) and on various physiological and perceptual measures. Sixteen male athletes (20 ± 3 years, 173 ± 7 cm, 67 ± 7 kg) performed the 5mSRT after a 40-min nap (N40), after a 90-min nap (N90), and in a no-nap, control condition (N0). The 5mSRT involves six repetitions of 30 s of all-out exercise. Total distance (in the six repetitions) and highest distance (in a single repetition) in the 5mSRT were greater after naps than in N0 (p < 0.001), and the total distance, which reflects the anaerobic capacity, was greater in N90 than in N40 (p < 0.05). Physiological and perceptual responses were favourable in both nap conditions (p < 0.01), more so in N90 than in N40 (p < 0.05). Together, the results support the contention that physiological/perceptual responses after napping contribute to improved exercise performance and that longer naps are more effective.

Short-term high-salt consumption does not influence resting or exercising heart rate variability but increases MCP-1 concentration in healthy young adults

High salt consumption increases blood pressure (BP) and cardiovascular disease risk by altering autonomic function and increasing inflammation. However, it is unclear whether salt manipulation alters resting and exercising heart rate variability (HRV), a noninvasive measure of autonomic function, in healthy young adults. The purpose of this investigation was to determine whether short-term high-salt intake 1) alters HRV at rest, during exercise, or exercise recovery and 2) increases the circulating concentration of the inflammatory biomarker monocyte chemoattractant protein 1 (MCP-1). With the use of a randomized, placebo-controlled, crossover study, 20 participants (8 females; 24 ± 4 yr old, 110 ± 10/64 ± 8 mmHg) consumed salt (3,900 mg sodium) or placebo capsules for 10 days each separated by ≥2 wk. We assessed HRV during 10 min of baseline rest, 50 min of cycling (60% V̇o2peak), and recovery. We quantified HRV using the standard deviation of normal-to-normal RR intervals, the root mean square of successive differences (RMSSD), and additional time and frequency domain metrics of HRV. Plasma samples were collected to assess MCP-1 concentration. No main effect of high salt or condition × time interaction was observed for HRV metrics. However, acute exercise reduced HRV (e.g., RMSSD time: P < 0.001, condition: P = 0.877, interaction: P = 0.422). High salt elevated plasma MCP-1 (72.4 ± 12.5 vs. 78.14 ± 14.7 pg/mL; P = 0.010). Irrespective of condition, MCP-1 was moderately associated (P values < 0.05) with systolic (r = 0.32) and mean BP (r = 0.33). Short-term high-salt consumption does not affect HRV; however, it increases circulating MCP-1, which may influence BP in young adults.

Change in heart rate variability during two firefighting work cycles

This study aimed to determine whether the change in heart rate variability from pre to post firefighting is modulated by different work cycles. Thirteen male firefighters underwent two firefighting simulations that comprised two identical 25-min work bouts intercalated by a passive recovery period of either 20 min (T20) or 5 min (T5). The square root of the mean squared differences of successive R-R intervals (RMSSD) and aural temperature were measured at rest before (PRE) and after (POST) firefighting simulations. The decrease in RMSSD was different between firefighting simulations (T20: -10 ± 21.2 ms, T5: -19.9 ± 20.9 ms, interaction, p = 0.02). Post-firefighting aural temperature was greater (p = 0.05) in T5 (37.18 ± 0.53 °C) than in T20 (36.88 ± 0.49 °C). In conclusion, a shorter recovery period of 5 min between firefighting work bouts decreases post-firefighting heart rate variability, possibly attributed to a lower parasympathetic reactivation and a higher absolute value of body temperature.

Beetroot Juice Produces Changes in Heart Rate Variability and Reduces Internal Load during Resistance Training in Men: A Randomized Double-Blind Crossover

Beetroot juice (BJ) has been used as a sport supplement, improving performance in resistance training (RT). However, its effect on the modulation of the autonomic nervous system has not yet been widely studied. Therefore, the objective of this randomized double-blind crossover study was to assess the effect of acute BJ supplementation compared to placebo in blood pressure (BP), heart rate (HR), heart rate variability (HRV) and internal load during RT measure as Root Mean Square of the Successive Differences between adjacent RR intervals Slope (RMSSD and RMSSD-Slope, respectively). Eleven men performed an incremental RT test (three sets at 60%, 70% and 80% of their repetition maximum) composed by back squat and bench press with. HR, HRV and RMSSD-Slope were measured during and post exercise. As the main results, RMSSD during exercise decrease in the BJ group compared to placebo (p = 0.023; ES = 0.999), there were no differences in RMSSD post-exercise, and there were differences in RMSSD-Slope between groups in favor of the BJ group (p = 0.025; ES = 1.104) with a lower internal load. In conclusion, BJ supplementation seems to be a valuable tool for the reduction in the internal load of exercise during RT measured as RMSSD-Slope while enhancing performance.

Feasibility of Ultra-Short-Term Analysis of Heart Rate and Systolic Arterial Pressure Variability at Rest and during Stress via Time-Domain and Entropy-Based Measures

Heart Rate Variability (HRV) and Blood Pressure Variability (BPV) are widely employed tools for characterizing the complex behavior of cardiovascular dynamics. Usually, HRV and BPV analyses are carried out through short-term (ST) measurements, which exploit ~five-minute-long recordings. Recent research efforts are focused on reducing the time series length, assessing whether and to what extent Ultra-Short-Term (UST) analysis is capable of extracting information about cardiovascular variability from very short recordings. In this work, we compare ST and UST measures computed on electrocardiographic R-R intervals and systolic arterial pressure time series obtained at rest and during both postural and mental stress. Standard time-domain indices are computed, together with entropy-based measures able to assess the regularity and complexity of cardiovascular dynamics, on time series lasting down to 60 samples, employing either a faster linear parametric estimator or a more reliable but time-consuming model-free method based on nearest neighbor estimates. Our results are evidence that shorter time series down to 120 samples still exhibit an acceptable agreement with the ST reference and can also be exploited to discriminate between stress and rest. Moreover, despite neglecting nonlinearities inherent to short-term cardiovascular dynamics, the faster linear estimator is still capable of detecting differences among the conditions, thus resulting in its suitability to be implemented on wearable devices.

Does Exercise Training Improve Cardiac-Parasympathetic Nervous System Activity in Sedentary People? A Systematic Review with Meta-Analysis

The aim of this study was to investigate the training-induced effect on cardiac parasympathetic nervous system (PNS) activity, assessed by resting heart rate variability (HRV) and post-exercise heart rate recovery (HRR), in sedentary healthy people. Electronic searches were carried out in PubMed, Embase, and Web of Science. Random-effects models of between-group standardised mean difference (SMD) were estimated. Heterogeneity analyses were performed by means of the chi-square test and I2 index. Subgroup analyses and meta-regressions were performed to investigate the influence of potential moderator variables on the training-induced effect. The results showed a small increase in RMSSD (SMD+ = 0.57 [95% confidence interval (CI) = 0.23, 0.91]) and high frequency (HF) (SMD+ = 0.21 [95% CI = 0.01, 0.42]) in favour of the intervention group. Heterogeneity tests reached statistical significance for RMSSD and HF (p ≤ 0.001), and the inconsistency was moderate (I2 = 68% and 60%, respectively). We found higher training-induced effects on HF in studies that performed a shorter intervention or lower number of exercise sessions (p ≤ 0.001). Data were insufficient to investigate the effect of exercise training on HRR. Exercise training increases cardiac PNS modulation in sedentary people, while its effect on PNS tone requires future study.

Kinetics of neuropeptide Y, catecholamines, and physiological responses during moderate and heavy intensity exercises

Neuropeptide Y 1-36 (NPY1-36) is a vasoconstrictor peptide co-secreted with norepinephrine (NE) by nerve endings during sympathetic activation. NPY1-36 potentiates NE action post-synaptically through the stimulation of the Y1 receptor, whereas its metabolite NPY3-36 resulting from DPP4 action activates Y2 presynaptic receptors, inhibiting NE and acetylcholine secretion. The secretions of NPY1-36 and NPY3-36 in response to sympathetic nervous system activation have not been studied due to the lack of analytical techniques available to distinguish them. We determined in healthy volunteers NPY1-36, NPY3-36 and catecholamine kinetics and how these neurotransmitters modulate the physiological stress response during and after moderate- and heavy-intensity exercises. Six healthy males participated in this randomized, double-blind, saxagliptin vs placebo crossover study. The volunteers performed an orthostatic test, a 30-min exercise at moderate intensity and a 15-min exercise at heavy intensity each followed by 50 min of recovery in two separate sessions with saxagliptin or placebo. Oxygen consumption (V̇O₂), ventilation and heart rate were continuously recorded. NE, epinephrine, NPY1-36 and NPY3-36 were quantified by tandem mass spectrometry. We found that exercise triggers NPY1-36 and NE secretion in an intensity-dependent manner and that NE returns faster to the baseline concentration than NPY1-36 after exercise. NPY3-36 rises during recovery parallel to the decline of NPY1-36. Saxagliptin reverses the NPY1-36/NPY3-36 ratio but does not affect hemodynamics, nor NPY1-36 and catecholamine concentrations. We found that NPY1-36 half-life is considerably shorter than previously established with immunoassays. NPY1-36 and NE secretions are finely regulated to prevent an excessive physiological Y1 stimulating response to submaximal exercise.

A Novel Physical Fatigue Assessment Method Utilizing Heart Rate Variability and Pulse Arrival Time towards Personalized Feedback with Wearable Sensors

This paper proposes a novel method for physical fatigue assessment that can be applied in wearable systems, by utilizing a set of real-time measurable cardiovascular parameters. Daylength measurements, including a morning test set, physical exercise during the day, and an afternoon test set were conducted on 16 healthy subjects (8 female and 8 male). To analyze cardiovascular parameters for physical fatigue assessment, electrocardiography, pulse wave and blood pressure were measured during the test sets. The fatigue assessment questionnaire score, reaction time, countermovement jump height and hand grip strength were also measured and used as reference parameters. This study demonstrates that (i) the compiled test battery can selectively assess the rested vs. physically-fatigued states; (ii) the obtained linear support-vector machine, trained using the heart rate variability based parameter (F-score 0.842, accuracy 0.813) and pulse arrival time based parameter (F-score 0.875, accuracy 0.875) shows a promising ability to classify between the physically mildly fatigued and significantly fatigued states. Despite the somewhat limited study group size, the results of the study are unique and provide a significant advancement on the existing physical fatigue assessment methods towards a personalized and continuous real-time fatigue monitoring system with wearable sensors.

Dysautonomia following COVID-19 is not associated with subjective limitations or symptoms but is associated with objective functional limitations

Background

Individuals who contract coronavirus disease 2019 (COVID-19) can suffer with persistent and debilitating symptoms long after the initial acute illness. Heart rate (HR) profiles determined during cardiopulmonary exercise testing (CPET) and delivered as part of a post-COVID recovery service may provide insight into the presence and impact of dysautonomia on functional ability.

Objective

Using an active, working-age, post–COVID-19 population, the purpose of this study was to (1) determine and characterize any association between subjective symptoms and dysautonomia; and (2) identify objective exercise capacity differences between patients classified “with” and those “without” dysautonomia.

Methods

Patients referred to a post–COVID-19 service underwent comprehensive clinical assessment, including self-reported symptoms, CPET, and secondary care investigations when indicated. Resting HR >75 bpm, HR increase with exercise <89 bpm, and HR recovery <25 bpm 1 minute after exercise were used to define dysautonomia. Anonymized data were analyzed and associations with symptoms, and CPET outcomes were determined.

Results

Fifty-one of the 205 patients (25%) reviewed as part of this service evaluation had dysautonomia. There were no associations between symptoms or perceived functional limitation and dysautonomia (P >.05). Patients with dysautonomia demonstrated objective functional limitations with significantly reduced work rate (219 ± 37 W vs 253 ± 52 W; P <.001) and peak oxygen consumption (V̇o₂: 30.6 ± 5.5 mL/kg/min vs 35.8 ± 7.6 mL/kg/min; P <.001); and a steeper (less efficient) V̇e/V̇co₂ slope (29.9 ± 4.9 vs 27.7 ± 4.7; P = .005).

Conclusion

Dysautonomia is associated with objective functional limitations but is not associated with subjective symptoms or limitation.

Post-exercise heart rate recovery and parasympathetic reactivation are comparable between prepubertal boys and well-trained adult male endurance athletes

Purpose

This study tested the hypothesis that prepubertal boys, but not untrained men, would exhibit a similar post-exercise parasympathetic reactivation as well-trained adult male endurance athletes.

Methods

Twelve prepubertal boys (12.3 ± 1.6 years), 14 untrained men (21.8 ± 2.2 years) and 16 well-trained adult male endurance athletes (24.5 ± 4.8 years) completed an incremental maximal run field test on a track. Immediately after exercise completion, heart rate recovery (HRR) was assessed in the supine position for 5 min. Heart rate variability was analyzed in the time domain, and log-transformed values of the root mean square of successive differences in heart beats (Ln RMSSD₃₀) were calculated over consecutive 30 s windows.

Results

Prepubertal children and well-trained adult endurance athletes showed significantly faster HRR than untrained adults from 30 s post-exercise until the end of recovery (p < 0.05). Ln RMSSD₃₀ was significantly higher in prepubertal children and athletes than untrained adults over the post-exercise time interval 60–150 s (p < 0.05). No significant differences were observed for HRR and Ln RMSSD₃₀ between prepubertal children and athletes.

Conclusion

Prepubertal children and well-trained adult endurance athletes exhibited comparable and faster HRR and parasympathetic reactivation than untrained adults following maximal exercise. This indirectly suggests that oxidative profile may be preserved by exercise training during growth and maturation to offset the decline in post-exercise HRR, parasympathetic reactivation and aspects of metabolic health.

Immersive Virtual Reality Influences Physiologic Responses to Submaximal Exercise: A Randomized, Crossover Trial

Objectives: This cross-sectional, randomly assigned study aimed to assess the influence of immersive virtual reality (VR) on exercise tolerance expressed as the duration of a submaximal exercise test (ET) on a cycle ergometer. Methods: The study enrolled 70 healthy volunteers aged 22-25years. Each participant performed an ET with and without VR. Time- and frequency-domain heart rate variability (HRV) parameters were analyzed for the first 3min (T1), the last 3min (T2), and the time at which the shorter of the two tests terminated (Tiso). In the time domain, a SD of R-R intervals (SDNN) and a root mean square of successive R-R interval differences (RMSSD) in milliseconds were computed. The following spectral components were considered: low frequency (LF), high frequency (HF), total power (TP), and LF/HF ratio. The study was registered in ClinicalTrials.gov (NCT04197024). Results: Compared to standard ET, tests in immersive VR lasted significantly longer (694 vs. 591s, p<0.00001) and were associated with lower HR response across the range of corresponding exercise levels, averaging 5-8 beats/min. In the multiple regression analysis, the ET duration was positively determined by male sex, immersion in VR, and negatively determined by HRT1 and RMSSDT1. Conclusion: Exercising in VR is associated with lower HR which allowed subjects to exercise for a longer time before reaching target heart rate (HR). In addition, the increase in exercise duration was found to be related to an adjustment in autonomic nervous activity at a given work rate favoring parasympathetic predominance.

Vagal reactivation after a cardiac rehabilitation session associated with hydration in coronary artery disease patients: crossover clinical trial

This study aimed to investigate the hydration influence on the autonomic responses of coronary artery disease subjects in the immediate recovery period after a cardiovascular rehabilitation session, in view of the risks of a delayed autonomic recovery for this population. 28 males with coronary artery disease were submitted to: (I) Maximum effort test; (II) Control protocol (CP), composed by initial rest, warm-up, exercise and passive recovery; (III) Hydration protocol (HP) similar to CP, but with rehydration during exercise. The recovery was evaluated through the heart rate (HR) variability, HR recovery and by the rate of perceived exertion and recovery. The main results revealed that the vagal reactivation occurred at the first 30 s of recovery in HP and after the first minute in CP. A better behavior of the HR at the first minute of recovery was observed in HP. The rate of perceived exertion had a significant decrease in the first minute of recovery in HP, while in CP this occurred after the third minute. In conclusion, despite an anticipated vagal reactivation found at HP, these results should be analyzed with caution as there were no significant differences between protocols for all variables and the effect sizes were small.

A Review of Inflammatory Bowel Disease: A Model of Microbial, Immune and Neuropsychological Integration

Objective: Inflammatory bowel diseases (IBDs) are complex chronic inflammatory disorders of the gastro-intestinal (GI) tract with uncertain etiology. IBDs comprise two idiopathic disorders: Crohn's disease (CD) and ulcerative colitis (UC). The aetiology, severity and progression of such disorders are still poorly understood but thought to be influenced by multiple factors (including genetic, environmental, immunological, physiological, psychological factors and gut microbiome) and their interactions. The overarching aim of this review is to evaluate the extent and nature of the interrelationship between these factors with the disease course. A broader conceptual and longitudinal framework of possible neuro-visceral integration, core microbiome analysis and immune modulation assessment may be useful in accurately documenting and characterizing the nature and temporal continuity of crosstalk between these factors and the role of their interaction (s) in IBD disease activity. Characterization of these interactions holds the promise of identifying novel diagnostic, interventions, and therapeutic strategies. Material and Methods: A search of published literature was conducted by exploring PubMed, EMBASE, MEDLINE, Medline Plus, CDSR library databases. Following search terms relating to key question were set for the search included: "Inflammatory bowel diseases," "gut microbiota," "psychological distress and IBD," "autonomic reactivity and IBD," "immune modulation," "chronic inflammation," "gut inflammation," "enteric nervous system," "gut nervous system," "Crohn's disease," "Ulcerative colitis", "depression and IBD", "anxiety and IBD", "quality of life in IBD patients," "relapse in IBDs," "remission in IBDs," "IBD disease activity," "brain-gut-axis," "microbial signature in IBD," "validated questionnaires in IBD," "IBD activity indices," "IBD aetiology," "IBDs and stress," "epidemiology of IBDs", "autonomic nervous system and gut inflammation", "IBD and environment," "genetics of IBDs," "pathways of immune response in IBDs," "sleep disturbances in IBD," "hypothalamic-pituitary-adrenal axis (HPA)," "sympatho-adrenal axis," "CNS and its control of gut function" "mucosal immune response," "commensal and pathogenic bacteria in the gut," "innate and adaptive immunity." Studies evaluating any possible associations between gut microbiome, psychological state, immune modulation, and autonomic function with IBDs were identified. Commonly cited published literatures with high quality research methodology/results and additional articles from bibliographies of recovered papers were examined and included where relevant. Results: Although there is a substantial literature identifying major contributing factors with IBD, there has been little attempt to integrate some factors over time and assess their interplay and relationship with IBD disease activity. Such contributing factors include genetic and environmental factors, gut microbiota composition and function, physiological factors, psychological state and gut immune response. Interdependences are evident across psychological and biological factors and IBD disease activity. Although from the available evidence, it is implausible that a single explanatory model could elucidate the interplay between such factors and the disease course as well as the sequence of the effect during the pathophysiology of IBD. Conclusion: Longitudinal monitoring of IBD patients and integrating data related to the contributing/risk factors including psychological state, physiological conditions, inflammatory/immune modulations, and microbiome composition/function, could help to explain how major factors associate and interrelate leading to exacerbation of symptoms and disease activity. Identifying the temporal trajectory of biological and psychosocial disturbances may also help to assess their effects and interdependence on individuals' disease status. Moreover, this allows greater insight into understanding the temporal progressions of subclinical events as potential ground for disease severity in IBD. Furthermore, understanding the interaction between these risk factors may help better interventions in controlling the disease, reducing the costs related to disease management, further implications for clinical practice and research approaches in addition to improving patients' mental health and quality of life.

Effects of Acute Stretching Exercise and Training on Heart Rate Variability: A Review

ABSTRACT

Wong, A and Figueroa, A. Effects of acute stretching exercise and training on heart rate variability: A review. J Strength Cond Res 35(5): 1459-1466, 2021-Stretching (ST), an exercise modality widely used for flexibility improvement, has been recently proposed as an effective adjunct therapy for declines in cardiovascular health, warranting research into the effects of ST exercise on cardiac autonomic function (CAF). Heart rate (HR) variability (HRV) is a reliable measure of CAF, mainly the sympathetic and parasympathetic modulations of HR. A low HRV has been associated to increased risk of cardiovascular events and mortality. Exercise interventions that enhance HRV are therefore seen as beneficial to cardiovascular health and are sought after. In this review, we discuss the effect of ST both acute and training on HRV. Stretching training seems to be a useful therapeutic intervention to improve CAF in different populations. Although the mechanisms by which ST training improves CAF are not yet well understood; increases in baroreflex sensitivity, relaxation, and nitric oxide bioavailability seem to play an important role.

Exercise-related blood pressure response is related to autonomic modulation in young adults: A new extension study

BACKGROUND:

The delayed blood pressure recovery (BPR) at post-exercise has been in association with a major risk of cardiovascular disease and death.

OBJECTIVE:

The study focused on evaluating the systolic and diastolic blood pressure recovery (SBPR, DBPR) and the autonomic modulation following treadmill exercise in healthy young adults. Although considerable literature had been published about BPR and HRV, the association between BPR and ultra-short-term HRV has not yet been completely described.

METHODS:

Fifteen subjects performed exercise with three different intensities on a treadmill, the speed was 6 km/h, 9 km/h, 12 km/h, respectively. SBP and DBP was measured per 30 s in each trial. The synchronous 5-min electrocardiogram (ECG) signals were recorded and HRV30s parameters including SDNN30s, RMSSD30s, SDNN30s/RMSSD30s, SD130s, SD230s and SD130s/SD230s were calculated every 30 s periods in 5 min ECG signals to match the corresponding BPR.

RESULTS:

The intraclass correlation coefficient (ICC) values and the Bland-Altman plots indicated good consistency and repeatability between HRV30s and HRV5min at three post-exercise trials, with most ICC values > 0.75. Besides, SBPR and DBPR generally decreased and returned to the Rest level in 5 mins. The Spearman correlation coefficients showed strong relationships between BPR and HRV30s sympathetic-vagal balance parameters, i.e., ratio SDNN/RMSSD and ratio SD1/SD2.

CONCLUSIONS:

These observations represented a new insight into the cardiovascular regulation at post-exercise, which could contribute to physical exercise areas in the future.

Post-exercise Heart Rate Variability: Whole-body Cryotherapy vs. Contrast Water Therapy

High-intensity training sessions are known to alter cardiac autonomic modulation. The purpose of this study was to compare the effects of whole-body cryotherapy, contrast water therapy and passive recovery on the time course of cardiac autonomic markers following a standardized HIT session. Eleven runners completed a high intensity session followed by one of the following recovery interventions: whole-body cryotherapy, contrast water therapy or passive recovery. Changes in cardiac autonomic modulation were assessed in supine and standing positions during an active tilt test at pre-, post-14 h and post-38 h. In supine, high-frequency power increased from pre- to post-14 h following whole-body cryotherapy (1661.1±914.5 vs. 2799.0±948.4 ms², respectively; p=0.023) and contrast water therapy (1906.1±1327.9 vs. 4174.3±2762.9 ms², respectively; p=0.004) whereas high frequency power decreased in response to passive recovery (p=0.009). In standing, low-frequency power increased from pre-to post-38 h (1784.3 ± 953.7 vs. 3339.8±1862.7 ms², respectively; p=0.017) leading to an increase in total power from pre- to post-38 h (1990.8 ± 1089.4 vs. 3606.1±1992.0 ms², respectively; p=0.017). Spectral analysis revealed that contrast water therapy appears to be a more efficient recovery strategy than whole-body cryotherapy in restoring cardiac autonomic homeostasis.

Contribution of the Autonomic Nervous System to Recovery in Firefighters

CONTEXT

Sudden cardiac deaths (SCDs) have accounted for nearly half of the line-of-duty deaths among US firefighters over the past 10 years. In 2018, 33% of all SCDs occurred after the end of a fire service call. Researchers have suggested that an imbalance in autonomic nervous system (ANS) regulation of heart rate postcall may interfere with recovery in firefighters.

OBJECTIVE

To use heart-rate recovery (HRR) and heart-rate variability (HRV), 2 noninvasive markers of ANS function, to examine the ANS recovery profiles of firefighters.

DESIGN

Cross-sectional study.

SETTING

Firehouse and research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty-seven male career active-duty firefighters (age = 39 ± 9 years, height = 178.8 ± 5.4 cm, mass = 87.9 ± 11.2 kg).

MAIN OUTCOME MEASURE(S)

Percentage of maximal HR (%MHR) and HRV (natural log of the square root of the mean sum of the squared differences [lnRMSSD]) were collected after both submaximal and maximal exercise protocols during a 10-minute seated recovery. The HRR profiles were examined by calculating the asymptote, amplitude, and decay parameters of the monoexponential HRR curve for each participant.

RESULTS

Differences in HRR parameters after 10 minutes of seated recovery were identified after submaximal versus maximal exercise (P < .001). In addition, although ANS was more suppressed after maximal exercise, HRV indicated incomplete recovery, and regardless of the test, recovery %MHR and lnRMSSD values did not return to pretest %MHR and lnRMSSD values.

CONCLUSIONS

Our results suggest that the ANS contributions to recovery in active-duty firefighters are exercise-intensity specific, and this is likely an important factor when establishing best-practice recovery guidelines.

Heart Rate Dynamics During Acute Recovery From Maximal Aerobic Exercise in Young Adults

INTRODUCTION

Resting heart rate (HRrest), heart rate variability (HRV), and HR recovery (HRR) from exercise provide valuable information about cardiac autonomic control. RR-intervals during acute recovery from exercise (RRrec) are commonly excluded from HRV analyses due to issues of non-stationarity. However, the variability and complexity within these trends may provide valuable information about changes in HR dynamics.

PURPOSE

Assess the complexity of RRrec and determine what physiologic and demographic information are associated with differences in these indices in young adults.

METHODS

RR-intervals were collected throughout maximal treadmill exercise and recovery in young adults (n = 92). The first 5 min of RRrec were (1) analyzed with previously reported methods that use 3-interval lengths for comparison and (2) detrended using both differencing(diff) and polynomial regression(res). The standard deviation of the normal interval (SDNN), root mean square of successive differences (rMSSD), root mean square (RMS) of the residual of regression, and sample entropy (SampEn) were calculated. Repeated measures analysis of covariance (ANCOVA) tested for differences in these indices for each of the methodological approaches, controlling for race, body fat, peak oxygen uptake (VO2p eak), and resting HR (HRrest). Statistical significance was set at p < 0.05.

RESULTS

VO2p eak and HRrest were significantly correlated with traditional measures of HRR and the variability surrounding RRrec. SampEndiff and SampEnres were correlated with VO2p eak but not HRrest or HRR. The residual-method provided a significantly (p = 0.04) lower mean standard error (MSE) (0.064 ± 0.042) compared to the differencing-method (0.100 ± 0.033).

CONCLUSIONS

Complexity analysis of RRrec provides unique information about cardiac autonomic regulation immediately following the cessation of exercise when compared to traditional measures of HRR and both HRrest and VO2peak influence these results.

Post-exercise heart rate recovery and its speed are associated with cardiac autonomic responsiveness following orthostatic stress test in men

Objective: The present study sought to expand upon prior investigations of the relationship between the post-exercise heart rate recovery (HRR) and the cardiac autonomic responsiveness after orthostatic stress test.Method: HRR at the 1st, 3rd, and 5th min after maximal exercise test were correlated with relative change (Δ%) of time-domain (CV, pNN50, and rMSSD) and frequency-domain (TP, LF, HF, and LF/HF ratio) indices of heart rate variability (HRV) after active orthostatic test in 46 healthy men. Statistical analysis employed non-parametric tests with a p-value set at 5%.Results: HRR at 1st min correlated with Δ%pNN50 (r_s:0.36 - p = .02). In the 3rd and 5th min, these measures correlated with Δ%pNN50, Δ%rMSSD, Δ%CV, Δ%TP, and Δ%HF indices (r_s:0.33, 0.59 - p ≤ .05). Coefficient of HRR at the 1st min correlated with Δ%pNN50, Δ%rMSSD, and Δ%HF (r_s:0.28, 0.45 - p ≤ .05). The 3rd and 5th min showed correlation with Δ%pNN50, Δ%rMSSD, Δ%HF, Δ%CV, and Δ%TP (r_s:0.37, 0.64 - p ≤ .05). No correlation was found with indices combined sympathetic-parasympathetic modulation and HRR. After the sample was divided into high and low parasympathetic responsiveness subgroups after the orthostatic test, faster HRR was associated with the degree of parasympathetic responsiveness (reduction) following postural change (p ≤ .05).Conclusion: HRR throughout the 1st to 5th min is positively correlated with parasympathetic responsiveness and overall cardiac autonomic modulation of HRV after the orthostatic stress test, and faster HRR is positively correlated with the relative degree of parasympathetic responsiveness after the active postural change at rest in healthy men.

An examination of single day vs. multi-day heart rate variability and its relationship to heart rate recovery following maximal aerobic exercise in females

The purpose of this study was to examine the relationship of a single day measure of heart rate variability (HRV), and the averaged baseline measures of HRV to heart rate recovery (HRR) following maximal exercise. Thirty females (22.9 ± 3.2 years, 64.8 ± 8.4 kg) completed four visits (V1-V4), where a 10-min HRV was recorded. Upon completing the V4 recording, a treadmill graded exercise test (GXT) was performed, followed by a 5-min active cool down. HRV was assessed through time domain measures [natural log of root mean square of successive R-R differences (lnRMSSD) and standard deviation of normal to normal intervals (lnSDNN)] and natural log frequency domain measures [low frequency (lnLF) and high frequency (lnHF)]. Variables collected over V1-V4 were measured as; day of (DO) GXT, 3 day (AV3), and 4 day average (AV4). HRR was calculated as the maximal HR achieved minus the HR at: 30-s (HRR30), 1-min (HRR1), 2-min (HRR2), 3-min (HRR3), 4-min (HRR4) or 5-min (HRR5) of recovery. Pearson's Product correlations revealed significant correlations (P = < 0.05) between all HRV_DO measures to each HRR measure and are presented in ranges: lnSDNN (r = 0.442-0.522), lnRMSSD (r = 0.458-0.514), lnLF (r = 0.368-0.469), lnHF (r = 0.422-0.493). For HRV_AV3, lnRMSSD_AV3 and HRR1 were positively correlated (r = 0.390, P = 0.033). Last, HRV_AV4 showed positive relationships (P = < 0.05) between lnRMSSD_AV4 and HRR30 (r = 0.365, P = 0.048); and for HRR1 and lnSDNN_AV4 (r = 0.400, P = 0.029), lnRMSSD_AV4 (r = 0.442, P = 0.014), and lnHF_{AV4 (}r = 0.368, P = 0.045); and lnRMSSD_AV4 and HRR3 (r = 0.381, P = 0.038). Within the current study HRV_DO displayed the strongest correlations to HRR therefore, averaged resting HRV measures do not strengthen the prediction of cardiovascular recovery following a GXT in this population.

Shortening Work-Rest Durations Reduces Physiological and Perceptual Load During Uphill Walking in Simulated Cold High-Altitude Conditions

Fornasiero, Alessandro, Aldo Savoldelli, Federico Stella, Alexa Callovini, Lorenzo Bortolan, Andrea Zignoli, David A. Low, Laurent Mourot, Federico Schena, and Barbara Pellegrini. Shortening work-rest durations reduces physiological and perceptual load during uphill walking in simulated cold high-altitude conditions. High Alt Med Biol. 21:249-257, 2020. Background: We investigated the effects of two different work-rest durations on the physiological and perceptual responses to a simulated mountain hike in a cold hypoxic environment. Materials and Methods: Twelve healthy nonacclimatized active men (age 31.3 ± 5.3 years, body mass index 22.4 ± 1.5 kg/m2) completed a 80-minute work-matched intermittent exercise on a motorized treadmill (25% incline, fixed self-selected speed), in a simulated mountain environment (-25°C, FiO2 = 11%, ≈5000 m a.s.l.), wearing extreme cold weather gear, once with short (20 × 3 minutes walking with 1 minute rest; SHORT) and once with long (10 × 6 minutes walking with 2 minutes rest; LONG) work-rest durations. Heart rate (HR), pulse oxygen saturation (SpO2), rate of perceived exertion (RPE), and thermal sensation (TS) were assessed throughout the exercise protocols. Cardiac autonomic modulation was assessed before (PRE) and after exercise (POST) in supine position, as well as during standing resting periods by means of HR recovery (HRR) assessment. Results: SpO2 and TS were similar (p > 0.05) in SHORT and LONG protocols. HR and RPE were increased, and HRR reduced during LONG compared to SHORT (p < 0.05). Parasympathetic activity indices were reduced at POST after both protocols (p < 0.05), but to a lesser extent after SHORT (p < 0.05). Conclusions: Reduced work-rest durations are associated with improved perceptual responses and less perturbation of cardiac autonomic balance, compared to longer work-rest durations. Shorter exercise periods from more frequent breaks during hikes at high altitude may represent a valid strategy to limit the impact of exercise under extreme environmental conditions.

Cardiac Parasympathetic Reactivation Following Small-Sided Games, Repeated Sprints and Circuit Training in Elite Handball Players

To compare acute parasympathetic reactivation following usual training exercises, the acute post-exercise heart rate (HR) and heart rate variability (HRV) were analysed. Fourteen elite male handball players completed three separate sessions of 16-min small-sided games (SSGs), repeated sprints (RSs) consisting of two sets of six repetitions of a 25-m sprint with a 180° change of direction (12.5 m + 12.5 m) every 25 s and 40 min of handball-specific circuit training (CT, one brief action every 40 s). The HR was recorded during the exercises; HRV was assessed 10 min before and after exercise. The exercise HR was higher for SSGs than RSs and it was higher for RSs than CT. Comparison of the baseline and acute post-exercise HRV values showed that parasympathetic indices decreased following SSG (p < 0.01 – p < 0.0001; large effect size) and RS (p < 0.05 –p < 0.01; large effect size) interventions. For CT, recovery values remained similar to the baseline (small effect size). The comparison of the acute recovery period between exercise modalities showed that the root mean square of the successive differences (RMSSD) was lower for SSGs than RSs and CT. No difference in any HRV indices was observed between RSs and CT. Time-varying of RMSSD for successive 30 s segments during the 10 min recovery period showed lower values for SSGs than CT for all tested points; the progressive increase in the beat-to-beat interval was similar for all interventions. In conclusion, SSGs caused the greatest post-exercise vagal disruption and it is likely that CT is the exercise modality that least delays over-all recovery. These results might help coaches design better training sessions by understanding athletes’ recovery status after completing their conditioning exercises.

Oral caffeine intake amplifies the effect of isoproterenol in patients with frequent premature ventricular contractions

AIMS

Infrequent appearance and failed induction of premature ventricular contractions (PVCs) at catheter ablation make their localization difficult and are associated with a poor procedural outcome. This study aimed to assess the effect of preprocedural oral caffeine intake on induction of PVCs during catheter ablation.

METHODS AND RESULTS

Seventy patients (age: 54 ± 14 years, 37 men) undergoing catheter ablation for monofocal PVCs were randomized to receive oral caffeine (5 mg/kg) or placebo. Before ablation, PVC counts for 5 min were performed at baseline and during isoproterenol infusion and the isoproterenol washout period. PVC count fluctuation was defined as the difference between the highest and lowest 5-min count among the three-time periods. The 5-min PVC counts during baseline and isoproterenol infusion were equivalent between the groups. However, those during the isoproterenol washout period and PVC count fluctuation were significantly higher in the caffeine group than the control group (73.1 ± 73.2 vs. 38.9 ± 28.9 beats/5 min, P = 0.012 and 69.3 ± 61.3 vs. 37.7 ± 30.9 beats/5 min, P = 0.008, respectively). The procedure and ablation times were significantly shorter in the caffeine group than the control group (105.0 ± 23.4 vs. 136.9 ± 43.2 min, P < 0.01 and 219.1 ± 104.7 vs. 283.5 ± 136.0 sec, P < 0.01, respectively).

CONCLUSION

Oral caffeine intake amplified the effect of isoproterenol infusion on PVC induction during catheter ablation. The combined use of oral caffeine intake and isoproterenol infusion can be an option to increase intraprocedural PVCs.

Does firefighters' physical fitness influence their cardiac parasympathetic reactivation? Analysis with post-exercise heart rate variability and ultra-short-term measures

Purpose. This study assessed the influence of firefighters' physical fitness on performances and parasympathetic reactivation in rescue interventions, and tested the validity of post-exercise ultra-short-term heart rate variability. Methods. Twenty-four firefighters were assigned to two groups based on their fitness and performed three simulated interventions. The mean completion time was recorded. The post-exercise root mean square of successive differences of R-R intervals (LnRMSSD) was determined from both criterion (between 5 and 10 min) and ultra-short-term (every 1-min segment from minutes 0-6) analyses. Results. Completion time was better for the highest fitness group in the three simulated interventions while post-exercise LnRMSSD was not influenced by the firefighters' fitness. Reliability between ultra-short-term and criterion analyses differed between the segments tested; minute 5-6 revealed the highest intra-class correlations (0.86-0.97). Concerning sensitivity of both analyses, the criterion analysis revealed differences between the three rescue interventions and the fitness test, but these results were not observed with ultra-short-term measures. Conclusions. Fitness was associated with firefighters' performances but not with parasympathetic reactivation in the firefighting intervention. The ultra-short-term measures do not seem to be a suitable post-exercise LnRMSSD analysis because of the low sensitivity to reveal differences among exercise conditions.

Exercise based assessment of cardiac autonomic function in type 1 versus type 2 diabetes mellitus

Background

Cardiac autonomic neuropathy (CAN) is a complication of diabetes mellitus (DM) that is associated with increased mortality. Exercise-based assessment of autonomic function has identified diminished parasympathetic reactivation after exercise in type 2 DM. It is postulated herein, that this would be more prominent among those with type 1 DM.

Methods

Sixteen subjects with type 1 DM (age 32.9 ± 10.1 years), 18 subjects with type 2 DM (55.4 ± 8.0 years) and 30 controls (44.0 ± 11.6 years) underwent exercise-based assessment of autonomic function. Two 16-min submaximal bicycle tests were performed followed by 45 min of recovery. On the second test, atropine (0.04 mg/kg) was administered near end-exercise so that all of the recovery occurred under parasympathetic blockade. Plasma epinephrine and norepinephrine levels were measured at rest, during exercise, and during recovery.

Results

There were no differences in resting or end-exercise heart rates in the three groups. Parasympathetic effect on RR-intervals during recovery (p < 0.03) and heart rate recovery (p = 0.02) were blunted in type 2 DM. Type 1 DM had higher baseline epinephrine and norepinephrine levels (p < 0.03), and exhibited persistent sympathoexcitation during recovery.

Conclusions

Despite a longer duration of DM in the study patients with type 1 versus type 2 DM, diminished parasympathetic reactivation was not noted in type 1 DM. Instead, elevation in resting plasma catecholamines was noted compared to type 2 DM and controls. The variable pathophysiology for exercise-induced autonomic abnormalities in type 1 versus type 2 DM may impact prognosis.

Impaired heart rate recovery after sub-maximal physical exercise in people with multiple sclerosis

BACKGROUND

Heart Rate Recovery (HRR) after a physical exercise has been poorly investigated in people with multiple sclerosis (PwMS).

OBJECTIVE

To evaluate the kinetics of HRR and its autonomic modulation in PwMS and to elucidate the interplay between HRR and subjective fatigue.

METHODS

ECG was digitally acquired during rest (5 min), submaximal exercise (4 min at 10 W of upper limb cycling) and recovery (3 min) in 17 PwMS (EDSS: 5.9 ± 1.2, mean±standard deviation) and 17 healthy control (HC) subjects. Short-term (first 30 s) and long-term (up to180 s) validated indices of HRR were calculated. The time course of the parasympathetic index of heart rate variability RMSSD (Root Mean Square of Successive Differences) was computed every 30 s of recovery. Subjective fatigue was evaluated by the Borg scale applied to breathing and upper limbs.

RESULTS

In comparison with HC, the short-term HRR indices were significantly slower (P < 0.05) in PwMS, whereas the long-term ones did not. The time course of RMSSD was significantly different in PwMS (P < 0.05). HRR and HRV indexes did not correlate with fatigue perception and baseline HRV values.

CONCLUSION

The cardiac parasympathetic reactivation from a submaximal exercise was blunted in PwMS, thereby slowing the short-term phase of HRR. This may contribute to the higher cardiovascular risk in PwMS, but the mechanism needs further investigation. The parasympathetic impairment during post-exercise HR reactivation cannot be predicted by baseline HRV values and may therefore be revealed only by an appropriate provocative low-intensity physical test.