Exercise Heart Rate Research Articles

IDF21-0335 Does serum vitamin D level effects post exercise heart rate recovery in patients with diabetes mellitus?

Background: Vitamin D deficiency is very common irrespective of age, race, and geographic location. Studies showed that the prevalence of vitamin D deficiency is higher in people with diabetes than those without diabetes. Autonomic neuropathy is a common complication of diabetes mellitus. Autonomic dysfunction has been associated with all-cause mortality, cardiac disease morbidity, and mortality in diabetes. Heart Rate Variability (HRV) and Heart Rate Recovery (HRR) both are the measures of autonomic nervous system function.

Comparison of Ratings of Perceived Exertion and Target Heart Rate-Based Exercise Prescription in Cardiac Rehabilitation: A RANDOMIZED CONTROLLED PILOT STUDY.

Although ratings of perceived exertion (RPE) are widely used to guide exercise intensity in cardiac rehabilitation (CR), it is unclear whether target heart rate ranges (THRRs) can be implemented in CR programs that predominantly use RPE and what impact this has on changes in exercise capacity. We conducted a three-group pilot randomized control trial (#NCT03925493) comparing RPE of 3-4 on the 10-point modified Borg scale, 60-80% of heart rate reserve (HRR) with heart rate (HR) monitored by telemetry, or 60-80% of HRR with a personal HR monitor (HRM) for high-fidelity adherence to THRR. Primary outcomes were protocol fidelity and feasibility. Secondary outcomes included exercise HR, RPE, and changes in functional exercise capacity. Of 48 participants randomized, four patients dropped out, 20 stopped prematurely (COVID-19 pandemic), and 24 completed the protocol. Adherence to THRR was high regardless of HRM, and patients attended a median (IQR) of 33 (23, 36) sessions with no difference between groups. After randomization, HR increased by 1 ± 6, 6 ± 5, and 10 ± 9 bpm ( P = .02); RPE (average score 3.0 ± 0.05) was unchanged, and functional exercise capacity increased by 1.0 ± 1.0, 1.9 ± 1.5, 2.0 ± 1.3 workload METs (effect size between groups, ηp2 = 0.11, P = .20) for the RPE, THRR, and THRR + HRM groups, respectively. We successfully implemented THRR in an all-RPE CR program without needing an HRM. Patients randomized to THRR had higher exercise HR but similar RPE ratings. The THRR may be preferable to RPE in CR populations for cardiorespiratory fitness gains, but this needs confirmation in an adequately powered trial.

Validation and Usability Evaluation of Mobile Application to Monitor Real-Time Exercise Heart Rate Zone

A mobile application to monitor heart rate (HR) during an exercise called Chromozone was developed to enable a user to regulate exercise intensity using a color-coded system rather than numerical display in the most conventional device. In this study, the agreement of HR from Chromozone was compared against the HR dataset from a clinically accepted electrocardiogram (ECG) on different exercise intensity and to assess its reliability by intra-day repeated assessments. Additionally, the usability aspect of the Chromozone smartphone application was also assessed. Forty-two participants underwent self-selected exercise intensities (based on individual HR reserve) included for 5-min followed by a cool-down period (3-min). A 20-min rest period was given to the participant before repeating the same exercise protocol two more times. Chromozone was found to generate excellent criterion-concurrent validity (r = 0.998, p < 0.001) and acceptable bias of 1.96 bpm (Limits of Agreement; LoA: 3.07 to -3.51) for relative and absolute agreement, respectively. Similarly, relative (intraclass correlation coefficient test: 0.998, p < 0.001) and absolute (within-subject coefficient of variation: 1.95 ± 1.4%) reliability using Chromozone application shows an excellent consistency. Additionally, this study also showed that the usability level of the Chromozone application is beyond the satisfactory level. The outcome of this work provides strong support for Chromozone application as a valid and reliable exercise HR monitoring tool that could potentially help athletes, active individuals as well as the clinical population to monitor and regulate their exercise training regime more effectively.

Selected vs. Non-Selected Under-20 National Futsal Players: Differences between Physical Performance and Training Intensity Experienced in Training Camps.

Simple SummaryIn sports training, the physical profiles and performances between selected and non-selected players are not identical. The players’ specific characteristics, such as exercise performance, locomotion profiles, and physical exertions during training sessions, can be used to identify the successful achievement in sports. However, such information has not been revealed in futsal. This study followed a prospective cohort design between 2018 and 2019. In our study, under-20 male Taiwan national futsal players were assessed for their physical fitness in two separate time periods. The perceived responses of physical exertion, exercise heart rate responses, and locomotion profiles were recorded during each training camp. Quantitative data during eighteen training camps/competition periods were collected for comparison. Our findings demonstrated that the selected players had a superior performance in 15 m Sprint and 30 m Sprint, exercise HR responses, and locomotor demands compared to the non-selected players. Coaches and their staff could consider the information of the present study for identifying selected players.The aim of this study was two-fold: (i) analyze the variations in the physical fitness of selected and non-selected under-20 male national futsal players; and (ii) analyze the variations in training intensity monitored during training camps. Thirty-three Taiwan under-20 national futsal players were monitored for training intensity during 18 training camps. They were divided into two groups: selected (n = 14) and non-selected (n = 17) players. The physical assessments included the following measures: body mass, distance covered at Yo-Yo intermittent recovery test Level 1, final velocity at 30-15 Intermittent Fitness Test (30-15 IFT), standing long jump, maximum heart rate (HR), and 1-min sit-up. The training intensity was monitored using the rate of perceived exertion (RPE), HR at different intensity zones, and locomotor demands measured at different speed thresholds. The results revealed that the selected players were significantly faster in the 15-m sprint with ball (p = 0.001) and 30-m sprint (p = 0.001). Additionally, the selected players presented significantly greater HRaverage and time spent above 90% maximum HR during the three-to-six-day training camps (p < 0.05) compared to the non-selected players. Interestingly, the NS demonstrated a greater number of sprints during the training camps (p = 0.001), while the selected players presented greater distance/minute and average speed (p = 0.001). A regression analysis showed that the distance/minute and average speed was a significant predictor of maximum HR in the selected players. As conclusions, the physical fitness outcomes are different between the selected and non-selected national futsal players. The selected players spent more time in high intensity HR demands in training sessions.

Monitoring of Maximum Oxygen Intake of Breathing and Heart Rate in Exercise Training Based on Regression Equations.

In order to provide a new reference method and basis for the physical testing study in healthy adults aged 40∼and 49, this paper proposes a regression equation-based monitoring study of exercise training breathing and heart rate. Sixty four subjects (30 males and 34 females), aged 40∼and 49 years, were selected. First, the subjects were screened by relevant health test and medical questionnaire to exclude the subjects with exercise contraindications and high-intensity exercise; then, the incremental load test was directly measured by gas analysis, and then, the subjects who completed the maximum oxygen intake test were tested twice, the corresponding heart rate value was recorded, and walking time were averaged for calculation. We show that the regression analysis of each index yielded regression equations and cross-validation regression equations show correlation statistics for measured and inferred maximum oxygen intake of RLOOCV = 0.826 and SEELOOCV = 0.378 (L/min). The equation can effectively speculate on the maximum oxygen intake of 40∼in healthy adults aged 49, with the advantages of efficient, low cost, fast, and convenient.

Chronotropic index during 6-minute walk and acute respiratory events in COPDGene

BackgroundLower heart rate (HR) increases during exercise and slower HR recovery (HRR) after exercise are markers of worse autonomic function that may be associated with risk of acute respiratory events (ARE). MethodsData from 6-min walk testing (6MWT) in COPDGene were used to calculate the chronotropic index (CI) [(HR immediately post 6MWT – resting HR)/((220 – age) – resting HR)] and HRR at 1 min after 6MWT completion. We used zero-inflated negative binomial regression to test associations of CI and HRR with rates of any ARE (requiring steroids and/or antibiotics) and severe ARE (requiring emergency department visit or hospitalization), among all participants and in spirometry subgroups (normal, chronic obstructive pulmonary disease [COPD], and preserved ratio with impaired spirometry). ResultsAmong 4,484 participants, mean follow-up time was 4.1 years, and 1,966 had COPD. Among all participants, CI-6MWT was not associated with rate of any ARE [adjusted incidence rate ratio (aIRR) 0.98 (0.95–1.01)], but higher CI-6MWT was associated with lower rate of severe ARE [0.95 (0.92–0.99)]. Higher HRR was associated with a lower rate of both any ARE [0.97 (0.95–0.99)] and severe ARE [0.95 (0.92–0.98)]. Results were similar in the COPD spirometry subgroup. ConclusionHeart rate measures derived from 6MWT tests may have utility in predicting risk of acute respiratory events and COPD exacerbations.

Analysis of Dynamic System of Exercise Load Condition Monitoring Based on Characteristic Parameters

According to the algorithm of time difference and threshold value, this paper selects the more valuable data for motion state recognition and selects the characteristics, respectively selects the data of the combined acceleration and the combined angular velocity, and uses the data of the pitch angle and the roll angle more novelly. In the aspect of data preprocessing, the sliding segmentation window method is used for feature processing, and the time domain and frequency domain features of the data are extracted. A total of 108 dimensional features are extracted. In order to improve the calculation performance, PCA technology is used for data dimensionality reduction. In this paper, we collected data on changes in physiological parameters of 24 experimenters before and after exercise, collected 14 self-evaluated severely fatigued volunteers and self-evaluated severely stressed volunteers’ resting heart rate and blood pressure data as unhealthy data samples, and collected physiological data of 14 healthy experimenters as unhealthy data samples. For healthy samples, three sets of experiments were set up to analyze the changes of exercise heart rate, exercise blood pressure and exercise body temperature, and the effectiveness of fusion of physiological data to improve the performance of exercise recognition and the analysis of the health status of physiological parameters that introduce exercise interference. The experimental results show that during exercise, monitoring changes in systolic blood pressure is more meaningful than monitoring changes in diastolic blood pressure; it verifies the effectiveness of improving the performance of exercise recognition by fusion of physiological parameters. The addition of physiological data can effectively improve the recognition rate of exercise. The recognition rate has been increased from 93.7% to 96.3%; the effectiveness and applicability of the algorithm in this paper are analyzed through design experiments, and the results show that the recognition accuracy of the algorithm in this paper is above 87%. This result has a good classification recognition rate for a small sample.

Day-to-day Variation of The Heart Rate, Heart Rate Variability, and Energy Expenditure During FIFA 11+ and Dynamic Warm-up Exercises.

There seems to be a scarcity in literature investigating day-to-day warm-up (WU) variations. We investigated day-to-day variation of psychophysiological responses during Fédération Internationale de Football Association (FIFA) 11+ and dynamic warm-up (DWU) exercises. Twenty-one male collegiate soccer players were randomly assigned to the FIFA 11+ (n = 10) or DWU group (n = 11). Each group performed the assigned WU protocol on three different occasions with a 48-h interval in between. The inter-day variation of the heart rate (HR), time distribution of HR zones, heart rate variability (HRV), estimated energy expenditure (EE), blood lactate (BL) concentration, and the Borg rating of perceived exertion (RPE) were recorded. A two-way repeated measures of analysis of variance was used to compare the differences in chosen variables [group (2) × day (3)]. The coefficient of variation was used to determine the dispersion of the variables over the sessions. The interclass correlation coefficient (ICC) with a two-way random model and a single measure (ICC2,1) was used to determine inter-day reliability. There were no significant differences in time spent at particular HR zones and EE in both groups. The FIFA 11+ exercises showed high reliability of exercise duration, average HR (HRaverage), minimal HR (HRmin), peak HR (HRpeak), and post-exercise RPE. In the DWU group, high reliability was found only in HRaverage, HRpeak, and post-exercise RPE. The FIFA 11+ exercises showed similar EE, exercise HR patterns, BL, and RPE compared to the DWU. The FIFA 11+ program is an intense WU protocol with a characteristically low variation of day-to-day exercise HR and RPE responses.

Factors Associated with Age-Related Declines in Cardiorespiratory Fitness from Early Adulthood Through Midlife: CARDIA.

This study aimed to describe maximal and submaximal cardiorespiratory fitness from early adulthood to midlife and examine differences in maximal fitness at age 20 yr and changes in fitness overtime by subcategories of sociodemographic, behavioral, and health-related factors. Data include 5018 Coronary Artery Risk Development in Young Adults participants (mean (SD) age, 24.8 (3.7) yr; 53.3% female; and 51.4% Black participants) who completed at least one maximal graded exercise test at baseline and/or the year 7 and 20 exams. Maximal and submaximal fitness were estimated by exercise duration and heart rate at the end of stage 2. Multivariable adjusted linear-mixed models were used to estimate fitness trajectories using age as the mechanism for time after adjustment for covariates. Fitness trajectories from ages 20 to 50 yr in 5-yr increments were estimated overall and by subgroups determined by each factor after adjustment for duration within the less favorable category. Mean (95% confidence interval) maximal fitness at age 20 and 50 yr was 613 (607-616) and 357 (350-362) s; submaximal heart rate during this period also reflected age-related fitness declines (126 (125-127) and 138 (137-138) bpm). Compared with men, women had lower maximal fitness at age 20 yr (P < 0.001), which persisted over follow-up (P < 0.001); differences were also found by race within sex strata (all P < 0.001). Differences in maximal fitness at age 20 yr were noted by socioeconomic, behavioral, and health-related status in young adulthood (all P < 0.05), which persisted over follow-up (all P < 0.001) and were generally consistent in sex-stratified analyses. Targeting individuals experiencing accelerated fitness declines with tailored intervention strategies may provide an opportunity to preserve fitness throughout midlife to reduce lifetime cardiovascular disease risk.

The reliability, validity and sensitivity of an individualised sub-maximal fitness test in elite rugby league athletes

ABSTRACT We aimed to examine the reliability, validity and sensitivity of an individualised sub-maximal fitness test (SMFTIFT60). Nineteen elite rugby league players performed a one-week test-retest of SMFTIFT60. Typical Errors and ICCs were: small (<3.5%) and extremely high (>0.90) for accelerometer-derived variables; moderate (<2.5% points) and moderate to very high (0.71–0.89) for exercise and recovery heart rate (HRex and HRR, respectively). Convergent validity correlations with the 10-week pre-season change in 30–15 Intermittent Fitness Test performance were large for changes in SMFTIFT60 HRex (r = −0.57) and HRR (0.60), and very large for changes in accelerometer measures (range: −0.71 to −0.79). For sensitivity, within-player dose–response relationships between SMFTIFT60 HRex and prior 3-day training loads were negative and ranged from moderate (session ratings of perceived exertion [sRPE-TL], r = −0.34), to large (high-speed running distance, −0.51; acceleration load, −0.73) and very large (heart rate Training Impulse [TRIMP], −0.83). All other relationships were unclear or trivial to small. Physiological and accelerometer-derived measures from the SMFTIFT60 are reliable and valid for the assessment of fitness in rugby league players. Only HRex appears sensitive to acute changes in training load. The SMFTIFT60 could be a useful monitoring tool in team sports

Cardiac Heart Rate Dependence on Mitochondrial Deuterium 2H Content

Mitochondrial cardiac ATP production efficiency in beef hearts has been known to decrease with increasing systemic deuterium 2H levels since the 1980’s. Recently ketogenic diets which are known to decrease deuterium levels in humans were found to decrease both the resting and exercise heart rates in a volunteer. Furthermore, resting heart rates were found to systematically vary with the deuterium content from the previous meal consumed by six volunteers. A cardiac model is proposed showing extreme sensitivity of heart rate on the deuterium loading of the ATP synthase nanomotors. A predicted increase in heart rate by 28% is expected with a 5% decrease in ATP production. This finding strongly suggests that high deuterium levels in the fatty acids contribute to the diastolic dysfunction in heart failure not already attributed to direct structural damage, i.e., heart failure with preserved ejection fraction.

Influence of age and gender on cardiovascular response to isometric exercise in apparently healthy individuals

Objective Static exercises are an integral aspect of patient rehabilitation and are employed in advanced strength and endurance training programmes. Exercise is a form of self-induced stress leading to circulatory and respiratory changes, therefore, this study sought to determine the influence of age and gender on the cardiovascular responses of apparently healthy individuals to isometric/static exercises. Methodology Sixty apparently healthy individuals (30 males and 30 females) participated in this study. Their ages ranged between 21–50 years and were grouped into 21–30 years, 31–40 years and 41–50 years. Each participant carried out and maintained 30% of maximal isometric voluntary contraction (MIVC) using hand grip for 1, 2 and 3 minutes respectively, with 30-minutes rest period. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were measured and recorded, at rest, and during each of the sustained contractions. Results There was a statistically significant increase (p &lt;0.05) in the mean SBP, DBP and HR at rest and with every increase in duration (that is, from 1 minute to 3 minutes) of static handgrip contraction, maintained at 30% MIVC in the 3 groups; except for HR for group one (that is, 21–30 years). There was no gender difference (p &gt;0.05) in SBP and DBP of the participants within the 3 groups, although male participants, particularly in group 2 had higher SBP. There was also a statistically significant increase in the HR of female participants compared to the males in group 2. Isometric contraction for 3 minutes produced the greatest change (increase) in cardiovascular parameter across all the groups but more marked among participants in group 2 (that is, 31–40 years). Conclusion The study concluded that submaximal (30% MIVC) isometric upper limb exercise increase blood pressure and heart rate in both sexes, with greatest values when the exercise was sustained for 3 minutes. Hence, efforts should be made to monitor cardiovascular parameters prior to prescribing safe level of isometric exercise. Also, 3 minutes of static/isometric exercises may be avoided, particularly during the rehabilitation of patient with cardiovascular disease.

Racial Differences On Post Exercise Heart Rate Recovery In Healthy Sedentary Adult Males-- A Meta-Analysis Study

Introduction: Post-exercise heart rate recovery (PEHRR) is the measure of parasympathetic function of heart which decreases the heart rate as the person stops exercising. The post exercise heart rate recovery is easily measurable index of heart parasympathetic activity. The post – exercise heart rate recovery is computed as peak heart rate minus the heart rate measured after 1 min of termination of exercise. The risk of cardiovascular disease in individual with African background is greater as compared to Caucasians and Asian population. The aim of this study was to analyze the difference in post exercise heart rate recovery in individuals from different ethnic backgrounds. Methods: A thorough literature search was carried out on PubMed, Google Scholar and PakMediNet with articles published between 2007 till 2021. The articles with post – exercise heart rate recovery in male adults with different ethnic backgrounds were included. A total of 8 studies were included after meeting the inclusion criteria for the meta-analysis. The studies that measured heart rate recovery after 1 minute of termination of exercise were included. Results: Out of 174 subjects 51 individuals were Africans, 104 were Asians and 19 were Caucasians. The post exercise heart raterecovery was not found to be statistically significant between the individuals from different ethnic groups (p value-0.258). Conclusion: The post – exercise heart rate recovery is not influenced by the racial differences. Further research on larger scale assessing the impact of parasympathetic activity in terms of heart rate recovery in individual from different ethnic background is required as very limited data is available till date.

Atrial-paced, exercise-similar heart rate envelope induces myocardial protection from ischaemic injury.

The study investigates the role and mechanisms of clinically translatable exercise heart rate (HR) envelope effects, without dyssynchrony, on myocardial ischaemia tolerance compared to standard preconditioning methods. Since the magnitude and duration of exercise HR acceleration are tightly correlated with beneficial cardiac outcomes, it is hypothesized that a paced exercise-similar HR envelope, delivered in a maximally physiologic way that avoids the toxic effects of chamber dyssynchrony, may be more than simply a readout, but rather also a significant trigger of myocardial conditioning and stress resistance. For 8 days over 2 weeks, sedated mice were atrial-paced once daily via an oesophageal electrode to deliver an exercise-similar HR pattern with preserved atrioventricular and interventricular synchrony. Effects on cardiac calcium handling, protein expression/modification, and tolerance to ischaemia-reperfusion (IR) injury were assessed and compared to those in sham-paced mice and to the effects of exercise and ischaemic preconditioning (IPC). The paced cohort displayed improved myocardial IR injury tolerance vs. sham controls with an effect size similar to that afforded by treadmill exercise or IPC. Hearts from paced mice displayed changes in Ca2+ handling, coupled with changes in phosphorylation of calcium/calmodulin protein kinase II, phospholamban and ryanodine receptor channel, and transcriptional remodelling associated with a cardioprotective paradigm. The HR pattern of exercise, delivered by atrial pacing that preserves intracardiac synchrony, induces cardiac conditioning and enhances ischaemic stress resistance. This identifies the HR pattern as a signal for conditioning and suggests the potential to repurpose atrial pacing for cardioprotection.

Comparison of coronary flow reserve feasibility and values in different stress echocardiography protocols: dobutamine, dipyridamole, exercise and rapid pacing

Abstract Background and aims To compare the feasibility of Coronary Flow Velocity Reserve (CFVR) assessment in the left anterior descending (LAD) artery in four types of stress echocardiography (SE): dobutamine (DOB), dipyridamole (DIP), rapid pacing (PAC) and bicycle exercise (EXE). Methods and results We subjected 369 patients (mean age: 67±11 years) to SE with DOB (up to 40 mcg/kg/min, n=230), DIP (0.84 mg/kg, n=73), PAC (n=22) or EXE (n=44). CFVR was measured as the ratio of peak diastolic coronary flow velocity (CFV) during exercise, pharmacological stress or pacing and peak diastolic CFV at rest in distal or mid LAD. The feasibility was excellent during PAC (100%), DOB (95%) and DIP (95%) and lower during EXE (73%, p&amp;lt;0.01 vs other groups) when assessed in all consecutive patients. When assessed in patients having readable LAD flow at rest the feasibility achieved even higher values, being however still lowered in EXE group, see Figure 1. In multivariate analysis only the EXE protocol was a predictor of LAD flow loss during SE, with OR = 8.23 (95% CI 2.17 – 31.33), p=0.0019. CFVR was lower with PAC (1.8±0.4) as compared to DIP (2.2±0.6, p=0.0061) and DOB (2.2±0.6, p=0.0025), but similar to EXE (2.0±0.6, p=0.178), and correlated best with the peak heart rate in EXE and PAC, see Figure 2. Conclusion CFVR in LAD can be obtained during all forms of SE, but the feasibility is significantly higher with PAC and pharmacological tests as compared to EXE, which was identified in our study as the independent predictor of the loss of LAD flow recording at the peak of stress test. Moreover, CFVR values were the lowest in PAC group which however encompassed the older patients with more advanced coronary artery disease. Significant correlation between HR and CFVR observed in EXE and PAC suggests that in this type of SE cut-off value of CFVR should be probably indexed to maximal HR achieved. Funding Acknowledgement Type of funding sources: None. Figure 1Figure 2

Modeling of Metabolic Equivalents (METs) during Moderate Resistance Training Exercises

Energy expenditure through metabolic equivalent (MET) prediction during resistance exercises in humans can be modeled by using cardiorespiratory parameters. In this study, we aimed to predict MET during six moderate-intensity resistance training sessions consisting of three different exercises. Eleven participants were recruited into two groups; an untrained (n = 5; with no resistance training experience) and a trained group (n = 6; with 2 months resistance training experience). Each participant completed six training sessions separated with a rest interval of 1–2 days. While wearing a mask for indirect calorimetric measurements using Cortex Metalyzer 3B, each participant performed training sessions consisting of three types of dumbbell exercises: shoulder press, deadlift, and squat. The metabolic equivalents (METs), respiratory exchange ratio (RER), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), blood lactate (BL), and Borg rate of perceived exertion (RPE) were measured. The MET was predicted using generalized estimating equations (GEE) for repeated measure data collected during exercise and rest periods. It was observed that during exercise period, RER, HR, SBP, and BL for the training group (QIC = 187, 95% CI = −0.012~0.915, p = 0.000*~0.033*) while RER, HR, SBP, DBP, and RPE (QIC = 48, 95% CI = −0.024~0.422, p = 0.000*~0.002*) during resting period for untrained group significantly predicted MET for moderate-intensity interval resistance training. It is concluded that the cardiorespiratory variables are significantly related to MET. During exercise, RER and HR significantly predicted MET for both groups along with additional parameters of SBP and BL for the training group. While during the resting period, RER, HR, SBP, DBP, and RPE related significantly for untrained and BL for training group respectively.

Running exercise with end-expiratory breath holding up to the breaking point induces large and early fall in muscle oxygenation.

The goal of this study was to assess the effects of repeated running bouts with end-expiratory breath holding (EEBH) up to the breaking point on muscle oxygenation. Eight male runners participated in three randomised sessions each including two exercises on a motorised treadmill. The first exercise consisted in performing 10-12 running bouts with EEBH of maximum duration either (separate sessions) at 60% (active recovery), 80% (passive recovery) or 100% (passive recovery) of the maximal aerobic velocity (MAV). Each repetition started at the onset of EEBH and ended at its release. In the second exercise of the session, subjects replicated the same procedure but with normal breathing (NB). Arterial oxygen saturation (SpO2), heart rate (HR) and the change in vastus lateralis muscle deoxy-haemoglobin/myoglobin (Δ[HHb/Mb]) and total haemoglobin/myoglobin (Δ[THb/Mb]) were continuously monitored throughout exercises. On average, the EEBHs were maintained for 10.1 ± 1.1s, 13.2 ± 1.8s and 12.2 ± 1.7s during exercise at 60%, 80% and 100% of MAV, respectively. In the three exercise intensities, SpO2 (mean nadir values: 76.3 ± 2.5 vs 94.5 ± 2.5%) and HR were lower with EEBH than with NB at the end of the repetitions; whereas, the mean Δ[HHb/Mb] (12.6 ± 5.2 vs 7.7 ± 4.4µm) and Δ[THb/Mb] (-0.6 ± 2.3 vs 3.8 ± 2.6µm) were, respectively, higher and lower with EEBH (p < 0.05). This study showed that performing repeated bouts of running exercises with EEBH up to the breaking point induced a large and early drop in muscle oxygenation compared with the same exercise with NB. This phenomenon was probably the consequence of the strong arterial oxygen desaturation induced by the maximal EEBHs.

Mechanisms of Exercise Capacity Improvement after Cardiac Rehabilitation Following Myocardial Infarction Assessed with Combined Stress Echocardiography and Cardiopulmonary Exercise Testing.

Cardiac rehabilitation (CR) is indicated in all patients after acute myocardial infarction (AMI) to improve prognosis and exercise capacity (EC). Previous studies reported that up to a third of patients did not improve their EC after CR (non-responders). Our aim was to assess the cardiac and peripheral mechanisms of EC improvement after CR using combined exercise echocardiography and cardiopulmonary exercise testing (CPET-SE). The responders included patients with an improved EC assessed as a rise in peak oxygen uptake (VO2) ≥ 1 mL/kg/min. Peripheral oxygen extraction was calculated as arteriovenous oxygen difference (A-VO2Diff). Out of 41 patients (67% male, mean age 57.5 ± 10 years) after AMI with left ventricular ejection fraction (LVEF) ≥ 40%, 73% improved their EC. In responders, peak VO2 improved by 27% from 17.9 ± 5.2 mL/kg/min to 22.7 ± 5.1 mL/kg/min, p < 0.001, while non-responders had a non-significant 5% decrease in peak VO2. In the responder group, the peak exercise heart rate, early diastolic myocardial velocity at peak exercise, LVEF at rest and at peak exercise, and A-VO2Diff at peak exercise increased, the minute ventilation to carbon dioxide production slope decreased, but the stroke volume and cardiac index were unchanged after CR. Non-responders had no changes in assessed parameters. EC improvement after CR of patients with preserved LVEF after AMI is associated with an increased heart rate response and better peripheral oxygen extraction during exercise.

SIMULATION OF THE RELATIONSHIP BETWEEN EXERCISE AND CARDIOPULMONARY FUNCTION AT HIGH ALTITUDE

ABSTRACT Introduction: Due to various uncertain and unexpected factors in life such as diseases, natural disasters, traffic accidents, and congenital disabilities, the number and proportion of lower limb amputations are still rising for many reasons, so the research on lower limb prostheses is particularly important. Objective: This work aimed to study the relationship between altitude exercise and cardiopulmonary function. Methods: A model of abnormal changes in cardiopulmonary function was established, and then 40 plateau exercisers were selected, all of whom arrived in Tibet in March 2017. The relationship between pulmonary circulation volume and internal pressure in the chest was observed and compared. The relationship between cardiopulmonary sensory reflex and exercise (high altitude) breathing and heart rate was analyzed. A comparison of the cardiopulmonary function of subjects of different genders was implemented. Moreover, the influence of different altitudes on the subjects’ cardiopulmonary function and the subjects’ cardiopulmonary function changes before departure and during the first, second, and third week after departure were observed and compared. Results: I. As the pressure in the thoracic cavity increased, the subjects’ pulmonary circulation blood volume gradually decreased, and the decrease was most obvious in the stage of thoracic pressure −50 to 0. II. As the cardiorespiratory reflex coefficient increased, the subjects’ breathing and heart rate compensatory acceleration appeared. III. Tracking and monitoring of the subjects’ cardiopulmonary indicators revealed that with the increase in altitude, the subjects’ average arterial pressure, respiratory frequency, and heart rate all showed an upward trend, while the blood oxygen saturation value showed a downward trend. IV. No matter how high the altitude was, the average arterial pressure, respiratory rate, and heart rate monitored of the subjects under exercise were significantly superior to the indicator values under resting state. In contrast, the blood oxygen saturation value showed the opposite trend. V. The subjects’ average arterial pressure, respiration, and heart rate in the first week were higher than other periods, but the blood oxygen saturation was relatively lower. In the second and third weeks, the changes in cardiopulmonary function were relatively smooth (all P&lt;0.05). VI. The changes in the index of the cardiopulmonary function of subjects of different genders were small (p&gt;0.05). Conclusion: Through modeling, the results of the plateau environment on the cardiopulmonary function of the body were made clearer, and these research data provided theoretical references for the training of the sports field in the plateau area. Level of evidence II; Therapeutic studies - investigation of treatment results.

Exercise heart rate reserve and recovery as risk factors for sudden cardiac death

BackgroundLittle is known if heart rate responses during and after exercise test may be associated with the risk of sudden cardiac death (SCD). Our aim was to determine if exercise heart rate reserve and recovery, providing non-invasive indices, may predict SCD risk in general male population. MethodsWe evaluated the impact of delayed heart rate reserve and slow heart rate recovery and the risk of SCD in the Kuopio Ischemic Heart Disease prospective cohort study of randomly selected 1967 men aged 42–61 years at recruitment. Heart rate reserve was calculated as the difference between the maximal attained heart rate and resting heart rate, whereas heart rate recovery was defined as maximal heart rate minus the heart rate measured at 2 min of recovery, on a symptom-limited cardiopulmonary exercise testing. ResultsDuring a median follow-up interval of 25 years, 209 events of SCD occurred. The age and examination adjusted relative hazards of SCD were in the lowest third of heart rate reserve 3.86 (95% confidence interval (CI) 2.56–5.80, p < 0.001) and the lowest third of heart rate recovery 2.86 (95% CI 1.95–4.20, p < 0.001) as compared to men in the highest third of heart rate reserve and heart rate recovery, respectively. After adjusting for potential confounders, the respective relative hazards were 1.96 (95% CI 1.24–3.12) and 1.75 (95% CI 1.16–2.64). Each unit increment (1 beat/min) in heart rate reserve and heart rate recovery decreased the incidence of SCD by 1–2%. ConclusionsDelayed exercise heart rate reserve and slow heart rate recovery predicted the risk of SCD, suggesting that heart rate responses may be associated with an increased risk for SCD in general population.