Effects of endurance training on resting and post-exercise cardiac autonomic control

Physiological, anthropometric and athletic performance adaptations from completing a 1-month pre-season period. A two-year longitudinal study in female collegiate soccer players

Introduction

Collegiate coaches and integrative support staff often utilize pre-season as a brief and intense training period to prepare athletes technically, tactically, and physiologically, to meet the demands of competition during a soccer season. This study sought to examine the dose-response from performing on-field soccer activities during a four-week pre-season period in female collegiate soccer players, and if the magnitude in response was associated with accumulated exercise stress.

Methods

A total of twenty-seven healthy female soccer players training as part of a collegiate soccer program volunteered to participate in this two-year longitudinal study. Data collection commenced prior to the start of each pre-season period, at the beginning of August, and was completed at the beginning of September, when pre-season ended. Data collection periods were separated by a 31-day period. Indices of cardiovascular function, anthropometry, and athletic performance were examined during each data collection period. Internal and external measures of accumulated exercise stress were recorded using the Polar Team Pro® system.

Results

When comparing the beginning to the end of pre-season, significant improvements were observed in body fat (%) [24.2 ± 6.0 "vs." 23.3 ± 5.6, p = 0.001], heart rate variability (rMSSD) [51.8 ± 25.1 "vs." 67.9 ± 34.6 ms, p = 0.002], resting heart (bpm) [73.8 ± 12.1 "vs." 64.3 ± 8.8, p = 0.001] and cardiorespiratory performance (YoYo IRTL-1) [925.8 ± 272.8 "vs." 1,062.6 ± 223.3 m, p = 0.001]. Significant reductions in musculoskeletal performance were observed through vertical jump height (cm) [24.9 ± 23.7, p = 0.04]. Change in the end of pre-season body weight (kg) was significantly associated with accumulated accelerations and decelerations [r ≥ 0.49, p = 0.01]. End of pre-season change in cardiorespiratory performance was significantly associated with both accumulated training load (au) and TRIMP (au) [r ≥ 0.63, p = 0.01].

Discussion

In conclusion, performing a four-week pre-season period, involving only on-field training, can promote positive and significant adaptations in anthropometry, cardiovascular function, and athletic performance measures in female collegiate soccer players. The magnitudes of these adaptations were associated with both internal and external measures of accumulated exercise stress.

Effects of weight loss and weight loss maintenance on cardiac autonomic function in obesity: a randomized controlled trial

NOVELTY

Caloric restriction and exercise exert significant improvements in cardiac autonomic function as measured by HRV in overweight and obesity. Aerobic exercise training, within recommended guidelines coupled with weight loss maintenance, retains cardiac autonomic function benefits from weight loss in previously obese individuals.

Detraining Effect on Cardiac Autonomic Response to an All-Out Sprint Exercise in Trained Adolescent Swimmers

PURPOSE

This study aimed to investigate the effects of a 5-week training cessation on the cardiac autonomic response after a 50-m swimming time-trial test.

METHODS

Twenty trained and highly trained adolescent swimmers (17.1 [2.7] y) performed a 50-m front-crawl all-out test before (visit 1) and after a 5-week training cessation (visit 2). After the warm-up, heart-rate variability (HRV) was recorded in a seated position using a Polar RS800CX heart-rate monitor during the 10 minutes before (preexercise) and immediately after the 50-m front-crawl all-out test (postexercise). Two-way analysis of variance (time × visit) and analysis of covariance were conducted to compute the effect of the 50-m all-out test on vagal-related HRV parameters (mean R-R, standard deviation of R-R intervals [SDNN], square root of the mean squared differences between successive R-R intervals [RMSSD], the percentage number of pairs of adjacent normal R-R intervals differing by more than 50 milliseconds in the entire recording [pNN50], and power in the high frequency [HF]) with Bonferroni post hoc test.

RESULTS

All the HRV parameters had a time main effect (P < .05), showing a reduction after the 50 m in both visits (P < .05). All the variables exhibited a visit main effect (P < .05); the preexercise and postexercise mean R-R, natural logarithm SDNN, natural logarithm RMSSD, and natural logarithm HF values declined after the training cessation (P < .05). Natural logarithm pNN50 preexercise values were reduced in visit 2 compared with visit 1 (P < .05). Only mean R-R was further reduced in response to the test in visit 2 compared with visit 1 (P < .05).

CONCLUSIONS

After 5 weeks of training cessation, all the preexercise and postexercise vagal-related HRV parameters evidenced a reduction, suggesting an impairment in swimmers' physical status. Coaches should be cautious with training loads at the start of the season.

Association between maximal aerobic capacity and heart rate variability

Relevance. Сardiovascular status could be assessed by maximal aerobic capacity (VO2max) through direct analysis of the gases involved in pulmonary ventilation and monitoring fluctuations in intervals between beats over time as heart rate variability. The aim of the study was to investigate the relationship between VO2max and heart rate variability in young adults. Materials and Methods. A total of 100 young adults between the ages of 18 and 25 were included in observational study, who did not engage in any strenuous physical activity, 50 of whom were male and 50 of whom were female.There were measured Heart rate variability in the frequency domain; LF, HF, LF/HF, and time domain; SDNN, RMSSD, pNN 50, and VO2max were assessed using a treadmill test according to Graded Exercise Protocol. Results and Discussion. There was weak positive correlation of VO2max with LF ( r = 0.177) and weak negative correlation with HF ( r = -0.141). Male participants had a weak negative relationship between VO2 max and LF ( r = -0.075), whereas female respondents had a weak positive relationship(r = 0.286). There was weak negative correlation of VO2max with LF/HF ratio for male subjects but weak positive correlation ( r = -0.101) for female subjects. For male and female participants, there was a weak negative association of VO2max with SDNN ( r = -0.170) and ( r = -0.301), respectively. Male and female participants had a weak negative association of VO2max with RMSSD, with ( r = -0.154) and ( r = -0.284) respectively. Male and female participants had a slight negative association of VO2max with pNN 50, with ( r = -0.062) and ( r = -0.441) respectively. Conclusion. Significant variations were found in the time domain and frequency domain indices including HF and LF/HF ratio which represents the balance between sympathetic and parasympathetic responses.

Application of a Reactive Agility Training Program Using Light-Based Stimuli to Enhance the Physical and Cognitive Performance of Car Racing Drivers: A Randomized Controlled Trial

BACKGROUND

There is a need to develop strategies that could contribute to the physical and mental preparation of motorsport athletes. A common method used by experienced motorsport athlete physical trainers is flashing light devices to train or assess reactive agility, despite limited evidence. Therefore, in the present study, we determined the effects of a 6-week reactive agility training program using light-based stimuli on the physiological and cognitive abilities of car racing drivers.

MATERIALS AND METHODS

The CONSORT guidelines for randomized controlled trial were used. In a single-blinded randomized controlled trial, 24 car racing drivers (EXP, n = 12; CON, n = 12) performed a comprehensive battery of cognitive tests marketed specifically at motorsport athletes from Vienna test system (VTS) at rest or during moderate intensity exercise on a bicycle. Physiological abilities were determined via a maximal incremental cardio-respiratory treadmill test. Baseline and post-intervention tests were performed on three consecutive days. Participants in EXP underwent a 6-week intervention consisting of 60-min training sessions twice a week using the Witty SEM light stimulus.

RESULTS

Participants in EXP but not in CON performed some of the VTS cognitive tasks with higher accuracy and/or shorter reaction time after the intervention at rest and during exercise. Car racing drivers performed the STROOP word-reading condition more accurately when the task was performed during the exercise vs. rest, regardless of group. In addition, the intervention induced beneficial changes in peak heart rate (HR), HR at gas exchange threshold, ventilation, and relative maximal oxygen consumption (rVO₂ max). In contrast, body mass and fat mass increased, while peak HR and rVO₂ max decreased in CON. Finally, participants in EXP improved their reactive agility performance and reaction time throughout the training program.

CONCLUSION

Overall, the reactive agility training program using light-based stimuli appeared to be efficient to induce beneficial effects on some physiological and cognitive performance measures; therefore, it may have the potential to contribute to car racing drivers' physical and mental performance.

Effects of Resistance Training Intensity on Heart Rate Variability at Rest and in Response to Orthostasis in Middle-Aged and Older Adults

OBJECTIVE

Aging and deficits related to decreased physical activity can lead to higher risks of autonomic nervous system (ANS) dysfunction. The aim of this study was to evaluate the effects of 24 weeks of resistance training (RT) at various intensities on hemodynamics as well as heart rate variability (HRV) at rest and in response to orthostatic tests in middle-aged and older adults.

METHODS

Forty adults were randomized into three groups: high-intensity (HEX) (80% 1-RM) (11 female, 4 male; 60 ± 4 years); low-moderate-intensity (LEX) (50% 1-RM) (nine female, four male; 61 ± 5 years); and a control group (CON) (eight female, four male; 60 ± 4 years). The RT program consisted of nine exercises, with two sets performed of each exercise two times per week for 24 weeks. Data collected included 1-RM, heart rate, and blood pressure and HRV at rest and in response to orthostasis.

RESULTS

Both the HEX (42-94%) and LEX (31.3-51.7%) groups showed increases in 1-RM (p < 0.01). The HEX group showed decreases in resting heart rate (-4.0%), diastolic blood pressure (-3.2 mmHg (-4.2%)), and low frequency/high frequency (LF/HF) (Ln ratio) (p < 0.05). Post-study, the HEX group had higher HF (Ln ms²) than the CON, adjusted for pre-study value and age (p < 0.05). Post-study, the supine-standing ratio (SSR) of LFn (normalized unit) in the HEX group was greater than that in the LEX and CON groups, while the SSR of LF/HF in the HEX group was greater than the CON (p < 0.05). In conclusion, high-intensity RT can improve resting heart rate and HRV by enhancing cardiac vagal control. High-intensity RT might also improve the orthostatic response in terms of HRV. High intensity RT might assist ANS modification and could perhaps decrease the risks of cardiovascular disease and orthostatic intolerance.

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.

Acute Changes in Heart Rate Variability to Glucose and Fructose Supplementation in Healthy Individuals: A Double-Blind Randomized Crossover Placebo-Controlled Trial

Simple Summary

In this study, we investigated the cardio-autonomic stress responses to the ingestion of liquid glucose, fructose, a combination thereof and a placebo in healthy individuals at rest. The cardio-autonomic response was more pronounced in all groups with carbohydrates compared to placebo indicating an increased cardio-autonomic stress response resulting in a reduced heart-rate variability. When investigating different levels of blood glucose, the findings showed a significant decline in heart-rate variability with increasing blood glucose levels. This was also seen with severely low levels of blood glucose. The speed of how quick blood glucose increased and decreased also impacted the cardio-autonomic response which further deteriorated heart-rate variability. These findings indicate that healthy human’s autonomic system responds quickly to changes in their blood glucose.

Abstract

Background: It is unknown how different types of carbohydrates alter the cardio-autonomic system in healthy individuals. Therefore, the aim of this study was to investigate how heart-rate variability changes to single dose ingestion of glucose, fructose, glucose and fructose, and an artificial sweetener (sucralose). Methods: In a double-blind randomized crossover placebo-controlled setting, 15 participants received all study-specific substances in liquid form. During each 2-h visit, venous blood glucose was measured in a 5-min interval while heart-rate variability was measured continuously via Holter-electrocardiograph. Results: Ingestion of different types of carbohydrates and sucralose showed significant differences for heart rate (p < 0.001), SDNN (p < 0.008), RMSSD (p < 0.001), pNN50 (p < 0.001) and blood pressure (p < 0.001). Different glucose levels significantly altered parameters of heart-rate variability and blood pressure (all p < 0.001), while the rate of change in blood glucose led to changes in heart rate variability, but not in heart rate (p = 0.25) or blood pressure (p = 0.99). Conclusions: Ingestion of different types of carbohydrates lead to reductions in heart-rate variability compared to a placebo. Blood glucose values above or below 70–90 mg/dL decreased heart rate variability while this was also seen for rapid glucose changes, yet not as pronounced. Healthy individuals should be conscious about carbohydrate intake while maintaining blood glucose levels between 70–90 mg/dL.

Studying the effect of garlic consumption and endurance training on serum levels of some pro-and anti-inflammatory cytokines in female mice with breast cancer - A randomized trial

Background:

This study aimed to determine the effect of garlic consumption and endurance training on the serum levels of some pro-inflammatory and anti-inflammatory cytokines in female mice with breast cancer.

Methods:

This study is an experimental research randomly conducted on 32 female BALB/c mice divided into 4 equal groups (N = 8), including: Cancer Control (CC), Garlic Supplementation (GS), Endurance Training (ET), Endurance Training + Garlic Supplementation (ET + GS). One million cancerous cells were injected to all mice's upper right thigh using the subcutaneous injection method. Exercise groups performed endurance training for 8 weeks (5 days a week.(Garlic supplement groups received 1 ml of the garlic extract orally per kilogram of body weight. The control groups -were not given any task, activity or exercise during the research. At the end of the research, all the mice were anesthetized, and their blood samples were collected.

Results:

The period of 8-week simultaneous endurance exercise and consumption of garlic supplement significantly decreased the serum level of interleukin-6 (F = 75 P = 0.00), interleukin-8 (F = 97.9 P = 0.00), and interleukin-17 (F = 95.7 P = 0.00), and increased the serum level of interleukin-10 (F = 50.4 P = 0.00).

Conclusions:

Along with other existing methods, reduction of inflammatory factors, endurance exercises and consumption of garlic supplement have been proved to be an extremely effective treatment for breast cancer patients.

Heart Rate Variability During Physical Exercise Is Associated With Improved Cognitive Performance in Alzheimer's Dementia Patients-A Longitudinal Feasibility Study

Heart rate variability (HRV) rapidly gains attention as an important marker of cardiovascular autonomic modulation. Moreover, there is evidence for a link between the autonomic deficit measurable by reduced HRV and the hypoactivity of the cholinergic system, which is prominently affected in Alzheimer's disease (AD). Despite the positive influence of physical exercise on cognition and its promising association with HRV, previous studies did not explore the effect of long-term physical exercise in older adults with AD. Taking advantage of a longitudinal study we analyzed the effect of a 20-week dual task training regime (3 × 15-min per week) on the vagal mediated HRV index RMSSD (root mean square of successive RR interval differences) during physical exercise and the short-term memory performance in a AD cohort (N = 14). Each training contained physical exercise on a bicycle ergometer while memorizing 30 successively presented pictures as well as the associated post-exercise picture recognition memory test. Linear-mixed modeling revealed that HRV-RMSSD significantly increased over the intervention time. Moreover, the reaction time in the picture recognition task decreased while the accuracy remained stable. Furthermore, a significantly negative relationship between increased fitness measured by HRV-RMSSD and decreased reaction time was observed. This feasibility study points to the positive effects of a dual task regime on physical and cognitive fitness in a sample with impaired cognitive performance. Beyond this, the results show that the responsiveness of parasympathetic system as measured with HRV can be improved in patients with dementia.

Greater arterial wall viscosity in endurance-trained men

PURPOSE

The age-associated increase in arterial wall viscosity (AWV) is attenuated by high cardiorespiratory fitness level. However, AWV in endurance-trained athletes have not been determined. We designed a cross sectional study to compare central AWV and compliance between endurance-trained young athletes and age-matched control men.

METHODS

Twenty-one endurance-trained men (age 20.7 ± 0.3 years) and 20 age-matched healthy control men (age 21.6 ± 0.4 years) were studied. The common carotid artery was measured noninvasively by tonometry and automatic tracking of B-mode images to obtain instantaneous pressure and diameter hysteresis loops, and we calculated the dynamic carotid arterial compliance, static (effective and isobaric) compliance, and viscosity index.

RESULTS

The AWV index in the endurance-trained men was larger than the control peers (2285 ± 181 vs. 1429 ± 124 mmHg·s/mm: P < 0.001). In addition, dynamic and static compliance were not statistically different between both groups.

CONCLUSION

The present study indicated that the central AWV in endurance-trained athletes was greater than age-matched healthy control men. We believe that the AWV, as well as arterial compliance, is an important element for assessing vascular adaptation to endurance training.

Hemodynamic and creatine kinase changes after a 12-week equipment-based Pilates training program in hypertensive women

Exercise therapy is a conservative strategy to manage hypertension. The aim of this study was to investigate the effects of a 12-week equipment-based Pilates training program on the hemodynamics of medication-controlled hypertensive women. Forty-five women were classified into two groups: medication-controlled hypertensive (n = 30) or control (n = 15). To be eligible for the hypertensive group, participants had to have a clinical diagnosis of hypertension, be taking medication to control their blood pressure and not to have done any exercise activity in the previous three months. In the control group, the participants needed to have normal blood pressure levels and not to have done any exercise activity in the previous three months. All women participated in a 12-week equipment-based Pilates training program (2 × 60min sessions per week). Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR) and creatine kinase levels (CK) were assessed before and after the program. SBP, DBP and heart rate were also assessed before and after each session. There was no statistically significant difference after Pilates training for systolic (normotensive MD 4.1, 95%CI -9.2 to 17.5, hypertensive MD 3.8, 95%CI -5.3 to 13.1) and diastolic (normotensive MD 5.8, 95%CI -2.0 to 13.7, hypertensive MD 4.0, 95%CI -4.3 to 12.4) blood pressure. Heart rate was reduced after Pilates training in both normotensive (MD 4.5, 95%CI 1.1 to 7.8) and medication-controlled hypertensive (MD 7.9, 95%CI 4.4 to 11.4) women. Creatine kinase activity was reduced after Pilates training in medication-controlled hypertensive women (p = 0.019). Blood pressure was not altered, but heart rate and creatinine kinase activity were reduced following 12 weeks of Equipment-based Pilates training.

BRADYCARDIA IN ATHLETES: DOES THE TYPE OF SPORT MAKE ANY DIFFERENCE? – A SYSTEMATIC REVIEW

ABSTRACT Bradycardia in athletes can range from moderate to severe, and the factors that contribute to slow heart rate are complex. Studies investigating the mechanisms associated with this condition are controversial, and may be linked to the form of exercise practiced. A systematic literature review was conducted to discuss bradycardia mechanisms in athletes who practice different forms of sport. The databases consulted were Pubmed (MEDLINE), Clinical Trials, Cochrane, Scopus, Web of Science, SciELO, Sport Discus and PEDro. The search included English language articles published up to January 2019, that evaluated athletes who practiced different forms of sport. One hundred and ninety-three articles were found, ten of which met the inclusion criteria, with 1549 male and female athletes who practiced diverse forms of sport. Resting heart rate and cardiac structure were studied in association with the form of sport practiced, through heart rate variability, electrocardiogram, echocardiogram and pharmacological blockade. The studies suggest that a slow resting heart rate cannot be explained by increased vagal modulation alone, but also includes changes in cardiac structure. According to the studies, different sports seem to produce different cardiac responses, and the bradycardia found in athletes can be explained by non-autonomic and autonomic mechanisms, depending on the type of effort or the form of sport practiced. However, the mechanism underlying the slow heart rate in each form of sport is still unclear. Level of evidence II; Prognostic studies - Investigating the effect of a patient characteristic on the outcome of disease.

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.

Reliability of a Repeated High-Intensity Effort Test for Elite Rugby Union Players

This study aimed to adapt a repeated high-intensity effort (RHIE) test to the rugby union physical demands and assess both sprint time and tackle indices reliability. Following a familiarization session, sixteen elite rugby union players completed two RHIE tests consisting of 12 × 20 m sprint + tackle. Total sprint time and total g-force during tackling, average sprint time and average g-force as well as percentage decrement_{sprint time} and percentage decrement_tackle were considered for the analysis. Sprint time indices showed high to very high absolute and relative reliability (intraclass coefficient correlation (ICC) = 0.95, Standard Error Measurement (SEM) = 1.30%; ICC = 0.95, SEM = 1.44%; ICC = 0.73, SEM = 23.0%, for total sprint time, average sprint time and percentage decrement_{sprint time}, respectively). Tackle indices showed moderate to high reliability (ICC = 0.54, SEM = 16.5%; ICC = 0.61, SEM = 15.6%; ICC = 0.71, SEM = 12.3%, for total g-force, average g-force and percentage decrement_tackle, respectively). The RHIE test provides reliable measures of sprint time and tackle indices. Tackle indices should be used as a validation criterion of the test, whereas total time should be considered as the test final result.

The impact of nine weeks swimming exercise on heart function in hypertensive and normotensive rats: role of cardiac oxidative stress

BACKGROUND

The purpose of this study was to estimate the effects of 9-week swimming training on cardiodynamic parameters and coronary flow in a rat model of high salt-induced hypertension with a special focus on the role of oxidative stress.

METHODS

Rats involved in the research were divided randomly into four groups: healthy sedentary (SA), healthy trained (TA), sedentary hypertensive (SHA) and trained hypertensive animals (THA). Trained rats were exposed to 9-week swimming training (5 days/week, 60 min/day). Additionally, in order to induce hypertension animals from SHA and THA groups were on high sodium (8% NaCl solution) diet during 4 weeks. Afterwards all rats were sacrificed and hearts were isolated and retrogradely perfused according to Langendorff technique. The following parameters of cardiac function were continuously recorded: maximum and minimum rate of pressure development in left ventricle, systolic and diastolic left ventricular pressure and heart rate. Coronary flow was measured flowmetrically. Oxidative stress markers were determined in coronary venous effluent.

RESULTS

Our findings demonstrated that 9 weeks of swimming training led to improvement of cardiac contractility, relaxation and systolic capacity of normotensive rats, while this training protocol induced enhanced diastolic function in hypertensive conditions. More pronounced effects of exercise in alleviating oxidative stress were observed in hypertensive rats.

CONCLUSIONS

Obvious beneficial exercise-induced cardiac adaptations provide scientific basis for further researches which would thoroughly clarify the mechanisms through which swimming training alters myocardial function both in healthy conditions and in the presence of chronic diseases.

Effects of Exercise on the Resting Heart Rate: A Systematic Review and Meta-Analysis of Interventional Studies

Resting heart rate (RHR) is positively related with mortality. Regular exercise causes a reduction in RHR. The aim of the systematic review was to assess whether regular exercise or sports have an impact on the RHR in healthy subjects by taking different types of sports into account. A systematic literature research was conducted in six databases for the identification of controlled trials dealing with the effects of exercise or sports on the RHR in healthy subjects was performed. The studies were summarized by meta-analyses. The literature search analyzed 191 studies presenting 215 samples fitting the eligibility criteria. 121 trials examined the effects of endurance training, 43 strength training, 15 combined endurance and strength training, 5 additional school sport programs. 21 yoga, 5 tai chi, 3 qigong, and 2 unspecified types of sports. All types of sports decreased the RHR. However, only endurance training and yoga significantly decreased the RHR in both sexes. The exercise-induced decreases of RHR were positively related with the pre-interventional RHR and negatively with the average age of the participants. From this, we can conclude that exercise-especially endurance training and yoga-decreases RHR. This effect may contribute to a reduction in all-cause mortality due to regular exercise or sports.

Heart rate recovery as a sensitive indicator of physical activity changes in perimenopausal and postmenopausal women

Heart rate recovery (HRR), which is defined as the rate of heart rate decline after cessation of exercise, is an important indicator of exercise tolerance. The aim of this study was to investigate the effect of a 4-month moderate reduction in physical activity on pre-exercise and exercise heart rate (HR) as well as HRR after exercise cessation in perimenopausal and postmenopausal women. 10 physically active females, 62.5±3.0 years old, participated in this study. They performed an 8-min constant power output (~50W) cycling exercise at an intensity corresponding to about 65% of maximal heart rate. Heart rate was measured continuously starting from 1 minute before exercise, during the exercise test and 3 min after exercise cessation. Furthermore, before and after exercise, blood pressure (BP) and tympanic temperature (Tt) were measured. The exercise test was performed twice, before and after a 4-month reduction in physical activity. 4 months of the slight reduction in physical activity (by ~16%) did not cause any changes in pre-exercise and exercise HR, however, significantly higher HR during the 1st min after exercise (p=0.03), as well slower HRR (p=0.03), were reported. No effects of the reduction in physical activity were observed in resting and post-exercise BP and Tt. Even a slight reduction in physical activity is accompanied by a lower rate of HRR , which indicates a decrease in exercise tolerance. These results indicate that HRR is a sensitive indicator of physical capacity also in peri- and postmenopausal women, since the changes in HRR in response to physical activity level occur earlier than changes in pre-exercise and exercise heart rate. heart rate, heart rate recovery, physical activity in the elderly

Parasympathetic activity delayed after self-paced exercise

The main purpose of this study was to compare the effect of the constant load and self-paced exercise with similar total work on autonomic control after endurance exercise. Ten physically active men were submitted to (i) a maximal incremental exercise test, (ii) a 4-km cycling time trial (4-km TT), and (iii) a constant workload test with identical total external work performed at 4-km TT. Gas exchange was measured throughout the tests, while blood lactate, heart rate, and heart rate variability (HRV) were measured during the passive recovery. Power output measured at the last lap (i.e. 3600-4000 m) of 4-km TT (316 ± 89 W) was statistically higher than power output measured at the end of the constant workload exercise (211 ± 42 W). The 4-km TT produced higher values of blood lactate concentration (8.8 ± 2.1 mmol L^-1) than the constant workload test (7.8 ± 2.1 mmol L^-1). The heart rate recovery measured at 60 s (constant workload: 37 ± 7 bpm; 4-km TT: 30 ± 6) and 120 s (constant workload: 57 ± 9 bpm; 4-km TT: 51 ± 9 bpm) were higher in the constant workload than in the self-paced exercise. The HRV (i.e. RMSSD30s) was statistically higher in the constant load exercise measured at 120, 420, 450, 480, 540, and 570 s than the self-paced exercise. These findings suggest that the autonomic control responses were dependent of the endurance exercise modalities, with parasympathetic activity being delayed after self-paced exercise, as evidenced by post-exercise heart rate indices.

An Acute Bout of Aquatic Treadmill Exercise Induces Greater Improvements in Endothelial Function and Postexercise Hypotension Than Land Treadmill Exercise: A Crossover Study

OBJECTIVE

The purpose of the study was to compare acute bouts of aquatic treadmill (ATM) and land treadmill (LTM) exercise on flow-mediated dilation, postexercise blood pressure, plasma nitrate/nitrite, and atrial natriuretic peptide in untrained, prehypertensive men.

DESIGN

In a counterbalanced, crossover design, 19 untrained, prehypertensive men completed bouts of ATM and LTM on separate days. Flow-mediated dilation was measured pre-exercise and 1-hr postexercise. Blood samples were obtained pre-exercise and immediately postexercise and analyzed for plasma nitrate/nitrite and atrial natriuretic peptide. A magnitude-based inference approach to inference was used for statistical analysis.

RESULTS

A possible clinically beneficial increase in flow-mediated dilation (1.2%, 90% confidence interval = -0.07% to 2.5%) was observed 1 hr after ATM. In contrast, a possible clinically harmful decrease in flow-mediated dilation (-1.3%, 90% confidence interval = -2.7% to 0.2%) was observed 1 hr after LTM. The magnitude of the postexercise systolic blood pressure reduction was greater after ATM (-4.9, SD = 2.9 mm Hg) than LTM (-2.6, SD = 2.5 mm Hg). Atrial natriuretic peptide increased 34.3 (SD = 47.0%) after ATM and decreased -9.0 (SD = 40.0%) after LTM.

CONCLUSIONS

An acute bout of ATM induced a more favorable endothelial response and greater postexercise hypotensive response than LTM. These changes were associated with increased atrial natriuretic peptide levels after ATM.

The Use of Autonomic Modulation Device to Control Training Performance after High-Intensity Interval Training Program

The aim of the present research was to analyze the autonomic response in a group of trained swimmers before and after conducting a 4-week period of high-intensity interval training (HIT). Heart rate variability was analyzed in 14 swimmers (16.2 ± 2.6 years, 169.1 ± 10.2 cm and 61.3 ± 9.9 kg) in basal condition and during a HIT session before and after completing a training period. The HIT session that was evaluated consisted of: 16 × 25 m maximum speed, resting 30 s between sets. Participants combined aerobic training with tethered swimming and HIT sessions three times per week in a period of 4 weeks. Results showed a significantly decrease (p < 0.05) of the standard deviation of the NN intervals (SDNN), the standard deviation of differences between adjacent NN intervals (SDSD), the number of successive difference of intervals which differ by more than 50 ms (NN50), after the training period. Results showed a higher parasympathetic activation besides improvements in autonomic adaptation after HIT training period.

Daily inspiratory muscle training lowers blood pressure and vascular resistance in healthy men and women

NEW FINDINGS

What is the central question of this study? What impact does inspiratory muscle training have on systemic vascular resistance, cardiac output and baroreflex sensitivity in adult men and women? What is the main finding and its importance? Inspiratory muscle training exerts favorable effects on blood pressure, vascular resistance and perception of stress. This exercise format is well-tolerated and equally effective whether implemented in men or women.

ABSTRACT

Previous work has shown that inspiratory muscle training (IMT) lowers blood pressure after a mere 6 weeks, identifying IMT as a potential therapeutic intervention to prevent or treat hypertension. Here, we explore the effects of IMT on respiratory muscle strength and select cardiovascular parameters in recreationally active men and women. Subjects were randomly assigned to IMT (n = 12, 75% maximal inspiratory pressure) or sham training (n = 13, 15% maximal inspiratory pressure) groups and underwent a 6-week intervention comprising 30 breaths day^-1 , 5 days week^-1 . Pre- and post-training measures included maximal inspiratory pressure and resting measures of blood pressure, cardiac output, heart rate, spontaneous cardiac baroreflex sensitivity and systemic vascular resistance. We evaluated psychological and sleep status via administration of the Cohen-Hoberman inventory of physical symptoms and the Epworth sleepiness scale. Male and female subjects in the IMT group showed declines in systolic/diastolic blood pressures (-4.3/-3.9 mmHg, P < 0.025) and systemic vascular resistance (-3.5 mmHg min l^-1 , P = 0.008) at week 6. There was no effect of IMT on cardiac output (P = 0.722), heart rate (P = 0.795) or spontaneous cardiac baroreflex sensitivity (P = 0.776). The IMT subjects also reported fewer stress-related symptoms (pre- versus post-training, 12.5 ± 8.5 versus 7.2 ± 9.7, P = 0.025). Based on these results, we suggest that a short course of IMT confers significant respiratory and cardiovascular improvements and parallel (modest) psychological benefits in healthy men and women.

Effects of weight changes in the autonomic nervous system: A systematic review and meta-analysis

BACKGROUND

Obesity has been linked to autonomic dysfunction, which is thought to be one of the main contributors for hypertension, cardiac remodelling and death. Exercise and diet-based weight loss are the mainstay therapy for obesity, but there is a paucity of data regarding the effect of weight changes in autonomic nervous system (ANS) activity.

OBJECTIVE

To describe the impact of weight changes in autonomic nervous system.

METHODS

A systematic literature search of four biomedical databases was performed evaluating effects of weight changes, thorough diet and/or exercise-based interventions, in the following ANS outcomes: heart rate variability, namely low frequency (LF)/high frequency (HF) ratio (LF/HF ratio), normalized units of LF (LFnu) and HF (HFnu), muscle sympathetic nerve activity (MSNA), noradrenaline spillover rate (NA-SR), standard deviation of normal-to-normal intervals (SDNN), root mean square of successive differences (RMSSD), baroreflex sensitivity and pupillometry. Quality appraisal was performed using the GRADE methodology and, where fitting, studies with comparable outcomes were pooled for meta-analysis.

RESULTS

Twenty-seven studies - 7 controlled clinical trials and 20 observational studies - were included. Weight gain was reported in 4 studies and weight loss in all the other studies. Interventions inducing weight changes included: hypocaloric or hypercaloric diets, exercise (strength, endurance or aerobic training) and hypocaloric diet coupled with exercise programs. Most studies which resulted in weight loss reported decreases in LF/HF ratio, LFnu, MSNA burst frequency and incidence, NA-SR, and an increase of baroreflex sensitivity, HF, HFnu and RMSSD, pointing to a parasympathetic nervous system activation. Meta-analysis regarding weight loss interventions showed a significant pooled effect size (95% CI) with a decreased of MSNA burst frequency -5.09 (-8.42, -1.75), MSNA incidence -6.66 (-12.40, -0.62), however this was not significant for SDNN 14.32 (-4.31, 32.96). Weight gain was associated with an increase in LF/HF, LFnu, MSNA burst frequency and incidence. The weight loss effects were potentiated by the association of hypocaloric diet with exercise. Nevertheless, weight changes effects in these outcomes were based in low or very low quality of evidence.

CONCLUSIONS

Diet and exercise based weight loss appears to increase parasympathetic and decrease sympathetic activity, the opposing effects being observed with weight gain. These findings are not uniformly reported in the literature, possibly due to differences in study design, methodology, characteristics of the participants and techniques used to estimate autonomic nervous activity.

Heart Rate Variability: An Old Metric with New Meaning in the Era of Using mHealth technologies for Health and Exercise Training Guidance. Part Two: Prognosis and Training

It has been demonstrated that heart rate variability (HRV) is predictive of all-cause and cardiovascular mortality using clinical ECG recordings. This is true for rest, exercise and ambulatory HRV clinical ECG device recordings in prospective cohorts. Recently, there has been a rapid increase in the use of mobile health technologies (mHealth) and commercial wearable fitness devices. Most of these devices use ECG or photo-based plethysmography and both are validated for providing accurate heart rate measurements. This offers the opportunity to make risk information from HRV more widely available. The physiology of HRV and the available technology by which it can be assessed has been summarised in Part 1 of this review. In Part 2 the association between HRV and risk stratification is addressed by reviewing the current evidence from data acquired by resting ECG, exercise ECG and medical ambulatory devices. This is followed by a discussion of the use of HRV to guide the training of athletes and as a part of fitness programmes.

In-season changes in heart rate recovery are inversely related to time to exhaustion but not aerobic capacity in rowers

To determine if in-season changes in heart rate recovery (HRR) are related to aerobic fitness and performance in collegiate rowers. Twenty-two female collegiate rowers completed testing before and after their competitive season. Body fat percentage (BF%) was determined by dual-energy X-ray absorptiometry. Maximal aerobic capacity (VO_2max ) and time to exhaustion (T_max ) were determined during maximal rowing ergometer testing followed by 1 minute of recovery. HRR was expressed absolutely and as a percentage of maximal HR (HRR%_1 min ). Variables were compared using paired Wilcoxon tests. Multivariable regression models were used to predict in-season changes in HRR using changes in VO_2max and T_max , while accounting for changes in BF%. From preseason to post-season, VO_2max and BF% decreased (3.98±0.42 vs 3.78±0.35 L/min, P=.002 and 23.8±3.4 vs 21.3±3.9%, P<.001, respectively), while T_max increased (11.7±1.3 vs 12.6±1.3 min, P=.002), and HRR%_1 min increased (11.1±2.7 vs 13.8±3.8, P=.001). In-season changes in VO_2max were not associated with HRR%_1 min (P>.05). In-season changes in T_max were related to changes in HRR%_1 min (β=-1.67, P=.006). In-season changes in BF% were not related to changes in HRR (P>.05 for all). HRR_1 min and HRR%_1 min were faster preseason to post-season, although the changes were unrelated to VO_2max . Faster HRR%_1 min post-season was inversely related to changes in T_max . This suggests that HRR should not be used as a measure of aerobic capacity in collegiate rowers, but is a promising measure of training status in this population.

Periodized training achieves better autonomic modulation and aerobic performance than non-periodized training

BACKGROUND

The aim of the present research was to analyze autonomic response and aerobic performance after performing three different workloads training distributions.

METHODS

Thirty athletes (mean age 38.7±9.8 years, height 174.7±6.5 cm, body weight 72.0±9.8 kg) were randomly divided into three groups of 10 participants each, to perform three different 4-week training programs: in a PRO group, aerobic training intensity increased during the 4 weeks; in a UNI group, aerobic intensity was uniform throughout the program; and in a FRE group, free training was performed. Total power, the very-low-frequency band, the low-frequency (LF) band, the high-frequency (HF) band, LF and HF normalized, basal heart rate, LF/HF ratio and maximal aerobic velocity were measured before and after the 4 weeks of training.

RESULTS

A significantly increase (P<0.05) in HF and HF normalized in the PRO group was measured. The basal HR of FRE group increased significantly after the 4-week training program.

CONCLUSIONS

After a 4-week training, PRO training workload distribution achieved higher autonomic adaptation than UNI and FRE training workload distribution. This information could help the coaches to develop better training programs and organize correctly the different mesocycles of training during the season to obtain a correct autonomic response of their athletes.

Cardiac Autonomic Responses during Exercise and Post-exercise Recovery Using Heart Rate Variability and Systolic Time Intervals-A Review

Cardiac parasympathetic activity may be non-invasively investigated using heart rate variability (HRV), although HRV is not widely accepted to reflect sympathetic activity. Instead, cardiac sympathetic activity may be investigated using systolic time intervals (STI), such as the pre-ejection period. Although these autonomic indices are typically measured during rest, the “reactivity hypothesis” suggests that investigating responses to a stressor (e.g., exercise) may be a valuable monitoring approach in clinical and high-performance settings. However, when interpreting these indices it is important to consider how the exercise dose itself (i.e., intensity, duration, and modality) may influence the response. Therefore, the purpose of this investigation was to review the literature regarding how the exercise dosage influences these autonomic indices during exercise and acute post-exercise recovery. There are substantial methodological variations throughout the literature regarding HRV responses to exercise, in terms of exercise protocols and HRV analysis techniques. Exercise intensity is the primary factor influencing HRV, with a greater intensity eliciting a lower HRV during exercise up to moderate-high intensity, with minimal change observed as intensity is increased further. Post-exercise, a greater preceding intensity is associated with a slower HRV recovery, although the dose-response remains unclear. A longer exercise duration has been reported to elicit a lower HRV only during low-moderate intensity and when accompanied by cardiovascular drift, while a small number of studies have reported conflicting results regarding whether a longer duration delays HRV recovery. “Modality” has been defined multiple ways, with limited evidence suggesting exercise of a greater muscle mass and/or energy expenditure may delay HRV recovery. STI responses during exercise and recovery have seldom been reported, although limited data suggests that intensity is a key determining factor. Concurrent monitoring of HRV and STI may be a valuable non-invasive approach to investigate autonomic stress reactivity; however, this integrative approach has not yet been applied with regards to exercise stressors.

Short-Term Heart Rate Recovery is Related to Aerobic Fitness in Elite Intermittent Sport Athletes

Watson, AM, Brickson, SL, Prawda, ER, and Sanfilippo, JL. Short-term heart rate recovery is related to aerobic fitness in elite intermittent sport athletes. J Strength Cond Res 31(4): 1055-1061, 2017-Although heart rate recovery (HRR) has been suggested as a measure of fitness, minimal data exist among athletes. The purpose of this study was to determine if HRR is related to aerobic fitness in elite athletes and whether this relationship is influenced by sex or body composition. Eighty-four collegiate athletes (45 male athletes) underwent body fat percentage (BF%) determination by dual-energy x-ray absorptiometry and maximal treadmill testing followed by 5 minutes of recovery. V[Combining Dot Above]O2max and heart rate (HRmax) were determined, and HRR was calculated as a percentage of HRmax at 10 seconds, 30 seconds, and 1, 2, 3, 4, and 5 minutes after test completion. After stratifying by sex, participants were grouped as high fit or low fit based on V[Combining Dot Above]O2max median split. Heart rate recovery was compared between sexes and fitness level at each time point. Multivariable regression analysis was used to identify independent predictors of HRR using V[Combining Dot Above]O2max, BF%, and sex as covariates. Heart rate recovery did not differ significantly between sexes and was faster among high-fit participants at 10 and 30 seconds, but at no other time. V[Combining Dot Above]O2max was significantly correlated with HRR at 10 and 30 seconds (r = -0.34, p < 0.001 and r = -0.28, p = 0.008) only. After controlling for BF% and sex, V[Combining Dot Above]O2max remained significantly associated with HRR at 10 seconds (p = 0.007) but not at 30 seconds (p = 0.067) or any time thereafter. Aerobic capacity is related to faster HRR during the first 30 seconds only, suggesting that only very short term HRR should be used as a measure of aerobic fitness in intermittent sport athletes.

A Submaximal Running Test With Postexercise Cardiac Autonomic and Neuromuscular Function in Monitoring Endurance Training Adaptation

Vesterinen, V, Nummela, A, Laine, T, Hynynen, E, Mikkola, J, and Häkkinen, K. A submaximal running test with postexercise cardiac autonomic and neuromuscular function in monitoring endurance training adaptation. J Strength Cond Res 31(1): 233-243, 2017-The aim of this study was to investigate whether a submaximal running test (SRT) with postexercise heart rate recovery (HRR), heart rate variability (HRV), and countermovement jump (CMJ) measurements could be used to monitor endurance training adaptation. Thirty-five endurance-trained men and women completed an 18-week endurance training. Maximal endurance performance and maximal oxygen uptake were measured every 8 weeks. In addition, SRTs with postexercise HRR, HRV, and CMJ measurements were carried out every 4 weeks. Submaximal running test consisted of two 6-minute stages at 70 and 80% of maximum heart rate (HRmax) and a 3-minute stage at 90% HRmax, followed by a 2-minute recovery stage for measuring postexercise HRR, HRV, and CMJ test. The highest responders according to the change of maximal endurance performance showed a significant improvement in running speeds during stages 2 and 3 in SRT, whereas no changes were observed in the lowest responders. The strongest correlation was found between the change of maximal endurance performance and running speed during stage 3, whereas no significant relationships were found between the change of maximal endurance performance and the changes of postexercise HRR, HRV, and CMJ. Running speed at 90% HRmax intensity was the most sensitive variable to monitor adaptation to endurance training. The present submaximal test showed potential to monitor endurance training adaptation. Furthermore, it may serve as a practical tool for athletes and coaches to evaluate weekly the effectiveness of training program without interfering in the normal training habits.

Hemodynamic Adaptations to Regular Exercise in People With Spinal Cord Injury

Objective

To investigate the real-time cardiovascular response to the progressive overload exercise in different levels of spinal cord injury (SCI), and to find out whether regular exercise has effect on these cardiovascular responses.

Methods

The study enrolled 8 able-bodied individuals in the control group plus 15 SCI subjects who were divided into two groups by their neurological level of injury: high-level SCI group (T6 or above) and low-level SCI group (T7 or below). Also, subjects were divided into exercise group and non-exercise group by usual exercise habits. We instructed the subjects to perform exercises using arm ergometer according to the protocol and checked plethysmograph for the real time assessment of blood pressure, heart rate, and cardiac output.

Results

Six subjects were included in high-level SCI group (3 cervical, 3 thoracic injuries), 9 subjects in low-level SCI group (9 thoracic injuries), and 8 able-bodied individuals in control group. During arm ergometer-graded exercise, mean arterial pressure (MAP) was significantly lower in high-level SCI subjects of non-exercise group, compared with high-level SCI subjects of exercise group. In addition, HR was significantly higher in low-level SCI group compared with control group.

Conclusion

There are significant differences in mean arterial pressure of high-level SCI group according to usual exercise habits. We discovered that even in non-athlete high-level SCI, regular exercise can bring cardiac modulation through blood pressure control.

Developing an Adapted Cardiac Rehabilitation Training for Home Care Clinicians: PATIENT PERSPECTIVES, CLINICIAN KNOWLEDGE, AND CURRICULUM OVERVIEW

PURPOSE

There is limited evidence that home care clinicians receive education on the core competencies of cardiac rehabilitation (CR). This article describes the development and implementation of a CR training program adapted for home care clinicians, which incorporated the viewpoints of homebound patients with cardiovascular disease.

METHODS

Literature and guideline reviews were performed to glean curriculum content, supplemented with themes identified among patients and clinicians. Semistructured interviews were conducted with homebound patients regarding their perspectives on living with cardiovascular disease and focus groups were held with home care clinicians regarding their perspectives on caring for these patients. Transcripts were analyzed with the constant comparative method. A 15-item questionnaire was administered to home care nurses and rehabilitation therapists pre- and posttraining, and responses were analyzed using a paired sample t test.

RESULTS

Three themes emerged among patients: (1) awareness of heart disease; (2) motivation and caregivers' importance; and (3) barriers to attendance at outpatient CR; and 2 additional themes among clinicians: (4) gaps in care transitions; and (5) educational needs. Questionnaire results demonstrated significantly increased knowledge posttraining compared with pretraining among home care clinicians (pretest mean = 12.81; posttest mean = 14.63, P < .001). There was no significant difference between scores for nurses and rehabilitation therapists.

CONCLUSIONS

Home care clinicians respond well to an adapted CR training to improve care for homebound patients with cardiovascular disease. Clinicians who participated in the training demonstrated an increase in their knowledge and skills of the core competencies for CR.

Effectiveness of Moderate Intensity Interval Training as an Index of Autonomic Nervous Activity

The purpose of this study was to examine the effects of moderate intensity interval training from the change of the autonomic nervous activity. Ten male volunteers aged 21-22 years were studied. After 10-minute rest in a seated position, the subjects were asked to perform the strength of moderate cycling exercise in ergometer. Cycling rate was done in 50 times/min. Load resistance of the ergometer was set to 2.0 kgm. Subjects paused the exercise when the heart rate becomes 120 beats/min. Subjects have resumed the exercise when the heart rate returns to the value at rest. This trial was repeated twice. The experiment was ended when the heart rate of the subjects has returned to resting level. When the heart rate during exercise is maintained to less than 120 beats/min, sympathetic nerve activity during exercise did not work actively compared to the baseline. Vagus nerve activity after exercise cessation exceeds the baseline. It is clarified that the exercise as well as activating the vagus nerve activity stimulates the total autonomic nervous activity. It has revealed that at the time of interval training at moderate load the vagus nerve activity can be carried out.

Atrial Fibrillation: The Science behind Its Defiance

Atrial fibrillation (AF) is the most prevalent arrhythmia in the world, due both to its tenacious treatment resistance, and to the tremendous number of risk factors that set the stage for the atria to fibrillate. Cardiopulmonary, behavioral, and psychological risk factors generate electrical and structural alterations of the atria that promote reentry and wavebreak. These culminate in fibrillation once atrial ectopic beats set the arrhythmia process in motion. There is growing evidence that chronic stress can physically alter the emotion centers of the limbic system, changing their input to the hypothalamic-limbic-autonomic network that regulates autonomic outflow. This leads to imbalance of the parasympathetic and sympathetic nervous systems, most often in favor of sympathetic overactivation. Autonomic imbalance acts as a driving force behind the atrial ectopy and reentry that promote AF. Careful study of AF pathophysiology can illuminate the means that enable AF to elude both pharmacological control and surgical cure, by revealing ways in which antiarrhythmic drugs and surgical and ablation procedures may paradoxically promote fibrillation. Understanding AF pathophysiology can also help clarify the mechanisms by which emerging modalities aiming to correct autonomic imbalance, such as renal sympathetic denervation, may offer potential to better control this arrhythmia. Finally, growing evidence supports lifestyle modification approaches as adjuncts to improve AF control.

Recovery levels after eccentric and concentric loading in maximal force

[Purpose] The aim of this study was to compare the differences in recovery periods after maximal concentric and eccentric exercises. [Subjects and Methods] Twenty-two participants voluntarily participated and were divided into two groups: the athlete and sedentary groups. An incremental treadmill running test was performed until exhaustion. During the subsequent passive recovery session, heart rate and venous blood lactate level were determined every 3 minutes until the venous blood lactate level reached 2 mmol/l. The same test protocol was implemented 15 days later. [Results] Both groups showed significantly shorter running durations in concentric exercise, while significant differences were found between the athlete and sedentary groups in terms of venous blood lactate level responses. In addition, there were significant differences between the athlete and sedentary groups in terms of running duration and heart rate in concentric and eccentric exercises. [Conclusion] The present study revealed no difference between the athlete and sedentary groups in terms of recovery durations after eccentric and concentric loadings, although the athletes demonstrated faster recovery in terms of HR compared with the sedentary group. It was thought that concentric exercises cause greater physiological responses.

Endurance training induces structural and morphoquantitative changes in rat vagus nerve

ABSTRACT Introduction: Many nervous system tissues and cells suffers positive changes when faced to exercise training. However, data on vagus nerve adaptation from exercise-induced study is absent. Objective: To analyze the effect of an endurance training on the vagus nerve morphology of rats. Methods: Wistar rats (6 months of age) were divided into two groups: control group (CG, n=8), and aerobic trained group (AT, n=8). AT was submitted to a treadmill training program of five times per week during 12 weeks. The maximum speed stipulated in the training protocol corresponded to 60% of the mean maximum intensity achieved by the group in the test of maximum effort. Results: Twelve weeks of treadmill training resulted in left ventricular hypertrophy in the AT group com-pared to CG. There was a significant increase in the area of both the myelinated and unmyelinated axons, and in the area of myelin sheath with training. The number of neurotubules and neurofilaments in myelinated fibers of aerobic trained group was significantly greater than CG (p≤0.05). Conclusion: Endurance training promoted significant increase in morphometric parameters of the vagus nerve in the same way it affect somatic nerves.

Autonomic adaptation after traditional and reverse swimming training periodizations

The objective of the present study was to analyze the autonomic response of trained swimmers to traditional and reverse training periodization models. Seventeen swimmers were divided in two groups, performing a traditional periodization (TPG) or a reverse periodization (RPG) during a period of 10 weeks. Heart rate variability and 50 m swimming performance were analyzed before and after the training programs. After training, the TPG decreased the values of the high frequency band (HF), the number of differences between adjacent normal R-R intervals longer than 50 ms (NN50) and the percentage of differences between adjacent normal R-R intervals more than 50 ms (pNN50), and the RPG increased the values of HF and square root of the mean of the sum of the squared differences between adjacent normal R-R intervals (RMSSD). None of the groups improved significantly their performance in the 50-m test. The autonomic response of swimmers was different depending on the periodization performed, with the reverse periodization model leading to higher autonomic adaption. Complementary, the data suggests that autonomic adaptations were not critical for the 50-m swimming performance.

An Eighteen-Minute Submaximal Exercise Test to Assess Cardiac Fitness in Response to Aerobic Training

Romagnoli, M, Alis, R, Sanchis-Gomar, F, Lippi, G, and Arduini, A. An 18-minute submaximal exercise test to assess cardiac fitness in response to aerobic training. J Strength Cond Res 32(10): 2846-2852, 2018-We aimed to evaluate the utility of a submaximal heart rate recovery (HRR) test to monitor changes in cardiac fitness after aerobic training. Twenty healthy subjects were assigned to a control (n = 10) or a training (n = 10) group. Subjects in the training group performed 8 weeks of bicycle training, followed by 8 weeks of detraining. Heart rate recovery was assessed after exercises at 65% and 80% HRmax. The HRR test was performed at weeks 0 (W0), 4 (W4), 8 (W8), and 16 (W16) in the training group and at W0 and W8 in the control group. Heart rate recovery indices changed in response to training and detraining. Absolute HRR at 60, 120, and 180 seconds after exercise increased at both exercise intensities at W8 of training (p < 0.01, W8 vs. W0) and returned to the pretraining level after detraining (p > 0.05, W16 vs. W0). Time constants of fast HRR recovery (<1 minute) changed with training (p < 0.05-0.01, W8 vs. W0) and detraining (p > 0.05, W16 vs. W0) but only at 65% HRmax. At the end of the 3-minute recovery period, the predicted heart rate (HR) value (A0) and the HR recovered (Amax) from the monoexponential analysis changed with training (p < 0.05-0.01, W8 vs. W0) and detraining (p > 0.05, W16 vs. W0). We conclude that this novel submaximal HRR test is highly sensitive for monitoring cardiac fitness during training and detraining in healthy people. Because this test is simple, inexpensive, and the data are reliable and easy to analyze, we hope that it may be of interest to the sports science community.

Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring

The measurement of heart rate variability (HRV) is often considered a convenient non-invasive assessment tool for monitoring individual adaptation to training. Decreases and increases in vagal-derived indices of HRV have been suggested to indicate negative and positive adaptations, respectively, to endurance training regimens. However, much of the research in this area has involved recreational and well-trained athletes, with the small number of studies conducted in elite athletes revealing equivocal outcomes. For example, in elite athletes, studies have revealed both increases and decreases in HRV to be associated with negative adaptation. Additionally, signs of positive adaptation, such as increases in cardiorespiratory fitness, have been observed with atypical concomitant decreases in HRV. As such, practical ways by which HRV can be used to monitor training status in elites are yet to be established. This article addresses the current literature that has assessed changes in HRV in response to training loads and the likely positive and negative adaptations shown. We reveal limitations with respect to how the measurement of HRV has been interpreted to assess positive and negative adaptation to endurance training regimens and subsequent physical performance. We offer solutions to some of the methodological issues associated with using HRV as a day-to-day monitoring tool. These include the use of appropriate averaging techniques, and the use of specific HRV indices to overcome the issue of HRV saturation in elite athletes (i.e., reductions in HRV despite decreases in resting heart rate). Finally, we provide examples in Olympic and World Champion athletes showing how these indices can be practically applied to assess training status and readiness to perform in the period leading up to a pinnacle event. The paper reveals how longitudinal HRV monitoring in elites is required to understand their unique individual HRV fingerprint. For the first time, we demonstrate how increases and decreases in HRV relate to changes in fitness and freshness, respectively, in elite athletes.

Autonomic control of heart rate after exercise in trained wrestlers

The objective of this study was to establish differences in vagal reactivation, through heart rate recovery and heart rate variability post exercise, in Brazilian jiu-jitsu wrestlers (BJJW). A total of 18 male athletes were evaluated, ten highly trained (HT) and eight moderately trained (MT), who performed a maximum incremental test. At the end of the exercise, the R-R intervals were recorded during the first minute of recovery. We calculated heart rate recovery (HRR_60s), and performed linear and non-linear (standard deviation of instantaneous beat-to-beat R-R interval variability – SD1) analysis of heart rate variability (HRV), using the tachogram of the first minute of recovery divided into four segments of 15 s each (0-15 s, 15-30 s, 30-45 s, 45-60 s). Between HT and MT individuals, there were statistically significant differences in HRR_60s (p <0.05) and in the non linear analysis of HRV from SD1_30-45s (p <0.05) and SD1_45-60s (p <0.05). The results of this research suggest that heart rate kinetics during the first minute after exercise are related to training level and can be used as an index for autonomic cardiovascular control in BJJW.