Heart rate recovery fast-to-slow phase transition: Influence of physical fitness and exercise intensity.

BACKGROUND: Postexercise heart rate (HR) recovery presents an exponential decay, with two distinct phases: a fast phase, characterized by abrupt decay of HR, and determined by parasympathetic reactivation; and a slow phase, characterized by gradual decay of HR, and predominantly determined by sympathetic withdrawal. Although several methods have been proposed to assess postexercise HR recovery, none of those methods selectively assesses the time of transition from the fast to the slow phase of the HR recovery curve (HRRPT ), and the magnitude of decay prior to (HRRFP ) and after this point (HRRSP ). Therefore, the aim of the present study was to propose a method to identify HRRPT , HRRFP , and HRRSP and to verify the effects of exercise intensity and physical fitness on such parameters. METHODS: Ten healthy young participants (24 ± 3 years; 23.6 ± 1.7 kg/m2 ) randomly underwent two exercise sessions (30 min of cycling), at moderate (MI) and high intensity (HI); followed by 5 min of inactive recovery. HR was continuously recorded during the sessions. The algorithm for HRRPT analysis was written in Python and is freely available online. RESULTS: HRRPT and HRRSP were increased in HI session compared with MI (81 ± 24 vs. 60 ± 20 s; 8 ± 10 vs. 1 ± 5 bpm; p = .04), and there was no difference in HRRFP between sessions (49 ± 15 vs. 46 ± 10 bpm; p = .17). In addition, HRRPT for MI exercise session was significantly and negatively associated with VO2max (r = -0.85, p < .05). CONCLUSION: The method herein presented was sensitive to exercise intensity, and partially responsive to aerobic fitness. Next studies should perform the pharmacological and clinical validations of the method.

Power spectrum analysis of cardiovascular variability during passive heating in conscious rats.

The cardiovascular system plays a direct role in the maintenance of body temperature. Whether passive heating alters cardiovascular autonomic modulation in conscious rats is still unknown. This study investigated the effects of passive heating on systolic blood pressure variability (SBPV) and heart rate variability (HRV) in conscious rats and the involvement of the renin-angiotensin system in the passive heating effects on SBPV and HRV. Fourteen male Wistar rats were randomly assigned to the control group or the losartan treatment group. A catheter was implanted in the left carotid artery to record pulsatile arterial pressure (PAP), and a telemetry sensor was implanted in the abdominal cavity to measure body temperature (Tbody). After recovering from surgery, the animals were subjected to a passive heating protocol (35°C; 30min) in resting conditions, during which Tbody, tail skin temperature and PAP were measured. The mean arterial pressure, systolic and diastolic blood pressure, heart rate, double product (i.e., the product of systolic blood pressure by heart rate), SBPV and HRV were calculated from the PAP. SBPV and HRV were analyzed in terms of both time and frequency domains. Increases in the thermoregulatory and cardiovascular parameters were observed during passive heating in both groups, and those increases were reflected in the higher time and frequency domains of the SBPV. However, passive heating was not effective in altering HRV. Passive heating altered SBPV but not HRV in conscious rats when they were treated with losartan.

Water intake accelerates parasympathetic reactivation after high-intensity exercise.

UNLABELLED: It has been shown that water intake (WI) improves postexercise parasympathetic recovery after moderate-intensity exercise session. However, the potential cardiovascular benefit promoted by WI has not been investigated after high-intensity exercise. PURPOSE: To assess the effects of WI on post high-intensity parasympathetic recovery. METHODS: Twelve recreationally active young men participated in the study (22 ± 1.4 years, 24.1 ± 1.6 kg.m(-2)). The experimental protocol consisted of two visits to the laboratory. Each visit consisted in the completion of a 30-min high-intensity [~80% of maximal heart rate (HR)] cycle ergometer aerobic session performing randomly the WI or control (CON, no water consumption) intervention at the end of the exercise. HR and RR intervals (RRi) were continuously recorded by a heart rate monitor before, during and after the exercise. Differences in HR recovery [e.g., absolute heart rate decrement after 1 min of recovery (HRR60s) and time-constant of the first order exponential fitting curve of the HRR (HRRτ)] and in postexercise vagal-related heart rate variability (HRV) indexes (rMSSD30s, rMSSD, pNN50, SD1 and HF) were calculated and compared for WI and CON. RESULTS: A similar HR recovery and an increased postexercise HRV [SD1 = 9.4 ± 5.9 vs. 6.0 ± 3.9 millisecond, HF(ln) = 3.6 ± 1.4 vs. 2.4 ± 1.3 millisecond(2), for WI and CON, respectively; p < .05] was observed in WI compared with CON. CONCLUSION: The results suggest that WI accelerates the postexercise parasympathetic reactivation after high-intensity exercise. Such outcome reveals an important cardioprotective effect of WI.

Acute effect of ultramarathon on systolic and diastolic cardiac function: Systematic review and meta-analysis.

BACKGROUND: Ultramarathon running poses physiological challenges, impacting cardiac function. This systematic review and meta-analysis explore the acute effects of single-stage ultramarathon running on cardiac function. METHODS: Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations were followed. Searches covered Medline, Embase, CINAHL, SPORTDiscus, Web of Science, Central Cochrane, and Scopus. Random effects meta-analyses assessed left ventricular (LV) and right ventricular (RV) variables, expressed as mean differences (MD) with 95% confidence intervals (CI). RESULTS: Among 6972 studies, 17 were included. Post-ultramarathon reductions were found in LV end-diastolic diameter (LVEDD) (-1.24; 95% CI = -1.77, -0.71 mm), LV end-diastolic volume (LVEDV) (-9.92; 95% CI = -15.25, -4.60 ml), LV stroke volume (LVSV) (-8.96 ml, 95% CI -13.20, -4.72 ml), LV ejection fraction (LVEF) (-3.71; 95% CI = -5.21, -2.22%), LV global longitudinal strain (LVGLS) (-1.48; 95% CI = -2.21, -0.76%), E/A (-0.30; 95% CI = -0.38, -0.22 cm/s), .E' (-1.35 cm/s, 95% CI -1.91, -0.79 cm/s), RV fractional area change (RVFAC) (-3.34, 95% CI = -5.84, -0.84%), tricuspid annular plane systolic excursion (TAPSE) (-0.12, 95% CI = -0.22, -0.02 cm), RV global longitudinal strain (RVGLS) (-1.73, 95% CI = -2.87, -0.59%), with increases in RV end-diastolic area (RVEDA) (1.89, 95% CI = 0.63, 3.14 cm2), RV Peak A' (1.32 cm/s, 95% CI 0.20, 2.44), and heart rate (18.24, 95% CI = 15.16, 21.32). No significant differences were observed in LV end-systolic diameter (LVESD), LV end-systolic volume (LVESV), RV end-diastolic diameter (RVEDD), RV Peak E', and RV Peak S'. CONCLUSIONS: Evidence suggests immediate impairment of systolic and diastolic cardiac function post-ultramarathon running.

Post-exercise heart rate variability recovery: a time-frequency analysis.

OBJECTIVE: Most studies investigating the effects of non-pharmacological interventions, such as physical training (PT), on cardiac autonomic control, assessed the HRV only in resting conditions. Recently, a new time-frequency mathematical approach based on the short-time Fourier transform (STFT) method has been validated for the assessment of HRV in non-stationary conditions such as the immediate post-exercise period. The aim of this study was to evaluate the effects of the PT on post-exercise cardiac autonomic control using the time-frequency STFT analysis of the HRV. METHODS: Twenty-one healthy male volunteers participated in this study. The subjects were initially evaluated for their physical exercise/sport practice and allocated to groups of low physical training ((Low)PT, n = 13) or high physical training (H(igh)PT, n = 8). The post-exercise HRV was assessed by the STFT method, which provides the analysis of dynamic changes in the power of the low- and high-frequency spectral components (LF and HF, respectively) of the HRV during the whole recovery period. RESULTS: Greater LF (from the min 5 to 10) and HF (from the min 6 to 10) in the post-exercise period in the H(igh)PT compared to the (Low)PT group (P < 0.05) was observed. CONCLUSION: These results indicate that exercise training exerts beneficial effects on post-exercise cardiac autonomic control.

Pulmonary oxygen uptake kinetics during exercise in subclinical hypothyroidism.

BACKGROUND: Patients with subclinical hypothyroidism (SCH) have lower exercise tolerance, but the impact on oxygen uptake (VO2) kinetics is unknown. This study evaluated VO2 kinetics during and after a constant load submaximal exercise in SCH. METHODS: The study included 19 women with SCH (thyrotropin (TSH)=6.87±2.88 µIU/mL, free thyroxine (fT4)=0.97±0.15 ng/dL) and 19 controls (TSH=2.29±0.86 µIU/mL, T4=0.99±0.11 ng/dL) aged between 20 and 55 years. Ergospirometry exercise testing was performed for six minutes with a constant load of 50 W, followed by six minutes of passive recovery. The VO2 kinetics was quantified by the mean response time (MRT), which is the exponential time constant and approximates the time needed to reach 63% of change in VO2 (ΔVO2). The O2 deficit-energy supplied by anaerobic metabolism at the onset of exercise-and O2 debit-extra energy demand during the recovery period-were calculated by the formula MRT×ΔVO2. Values are mean±standard deviation. RESULTS: In the rest-exercise transition, patients with SCH showed slower VO2 kinetics (MRT=47±8 sec vs. 40±6 sec, p=0.004) and a higher oxygen deficit (580±102 mL vs. 477±95 mL, p=0.003) than controls respectively. In the exercise-recovery transition, patients with SCH also showed slower VO2 kinetics (MRT=54±6 sec vs. 44±6 sec, p=0.001) and a higher oxygen debit (679±105 mL vs. 572±104 mL, p=0.003). The VO2 kinetics showed a significant correlation with TSH (p<0.05). CONCLUSIONS: This study demonstrates that women with SCH have the slowest VO2 kinetics in the onset and recovery of a constant-load submaximal exercise and highlights that this impairment is already manifest in the early stage of the disease.

Association of lower urinary tract symptoms and maximal oxygen uptake (VO2max) in men aged 50 to 59 years: a case-control study.

OBJECTIVE: To determine the association of lower urinary tract symptoms (LUTS) with maximal oxygen uptake (VO2max), flexibility, physical activity level, and anthropometric variables. METHODS: A case-control study has been conducted in which LUTS was the outcome and VO2max, flexibility, physical activity level, and anthropometric variables the exposure variables. We evaluated 100 men aged between 50 and 59 years, assigning 49 to the case group and 51 to the control group. The patients underwent the following: physical activity level assessment using the International Physical Activity Questionnaire; LUTS assessment using the International Prostate Symptom Score Questionnaire; anthropometric assessment measuring body mass index, waist-to-hip ratio, and waist circumference; VO2max assessment through the Polar Fitness Test; and flexibility assessment using the Sit and Reach test. Multivariable analysis using a logistic regression model was performed for the assessment of odds ratio (OR) and 95% confidence interval (95% CI). RESULTS: In bivariable analysis, a statistically significant association was identified for LUTS with physical activity level (OR = 0.375, 95% CI = 0.167-0.841, P = .02); with VO2max (OR = 0.206, 95% CI = 0.086-0.495, P <.001); and with flexibility (OR = 0.309, 95% CI = 0.130-0.337, P = .01). However, the multivariable analysis indicated that VO2max was the only statistically significant variable associated with LUTS (OR = 0.303, 95% CI = 0.105-0.875, P = .027). CONCLUSION: In men aged between 50 and 59 years, an association between inadequate VO2max with LUTS was found.

Absence of parasympathetic reactivation after maximal exercise.

The ability of the human organism to recover its autonomic balance soon after physical exercise cessation has an important impact on the individual's health status. Although the dynamics of heart rate recovery after maximal exercise has been studied, little is known about heart rate variability after this type of exercise. The aim of this study is to analyse the dynamics of heart rate and heart rate variability recovery after maximal exercise in healthy young men. Fifteen healthy male subjects (21·7 ± 3·4 years; 24·0 ± 2·1 kg m(-2) ) participated in the study. The experimental protocol consisted of an incremental maximal exercise test on a cycle ergometer, until maximal voluntary exhaustion. After the test, recovery R-R intervals were recorded for 5 min. From the absolute differences between peak heart rate values and the heart rate values at 1 and 5 min of the recovery, the heart rate recovery was calculated. Postexercise heart rate variability was analysed from calculations of the SDNN and RMSSD indexes, in 30-s windows (SDNN(30s) and RMSSD(30s) ) throughout recovery. One and 5 min after maximal exercise cessation, the heart rate recovered 34·7 (±6·6) and 75·5 (±6·1) bpm, respectively. With regard to HRV recovery, while the SDNN(30s) index had a slight increase, RMSSD(30s) index remained totally suppressed throughout the recovery, suggesting an absence of vagal modulation reactivation and, possibly, a discrete sympathetic withdrawal. Therefore, it is possible that the main mechanism associated with the fall of HR after maximal exercise is sympathetic withdrawal or a vagal tone restoration without vagal modulation recovery.

[Polar S810 as an alternative resource to the use of the electrocardiogram in the 4-second exercise test]. / Polar S810 como recurso alternativo ao eletrocardiograma no teste de exercício de 4 segundos.

BACKGROUND: The 4-second exercise test (T4s) evaluates the cardiac vagal tone during the initial heart rate (HR) transient at sudden dynamic exercise, through the identification of the cardiac vagal index (CVI) obtained from the electrocardiogram (ECG). OBJECTIVE: To evaluate the use of the Polar S810 heart rate monitor (HRM) as an alternative resource to the use of the electrocardiogram in the 4-second exercise test. METHODS: In this study, 49 male individuals (25 +/- 20 years, 176 +/-12 cm, 74 +/- 6 kg) underwent the 4-second exercise test. The RR intervals were recorded simultaneously by ECG and HRM. We calculated the mean and the standard deviation of the last RR interval of the pre-exercise period, or of the first RR interval of the exercise period, whichever was longer (RRB), of the shortest RR interval of the exercise period (RRC), and of the CVI obtained by ECG and HRM. We used the Student t-test for dependent samples (p < or 0.05) to test the significance of the differences between means. To identify the correlation between the ECG and the HRM, we used the linear regression to calculate the Pearson's correlation coefficient and the strategy proposed by Bland and Altman. RESULTS: Linear regression showed r(2) of 0.9999 for RRB, 0.9997 for RRC, and 0.9996 for CVI. Bland e Altman strategy presented standard deviation of 0.92 ms for RRB, 0.86 ms for RRC, and 0.002 for CVI. CONCLUSION: Polar S810 HRM was more efficient in the application of T4s compared to the ECG.

Escalas de Borg e omni na prescrição de exercício em cicloergômetro / Escalas de Borg e omni na prescrição de exercício em cicloergômetro

As escalas de percepção de esforço de Borg e OMNI são amplamente validadas para identificação da intensidade do exercício. O estudo teve como objetivo testar a correspondência entre as categorias das Escalas de Borg (6-20) e OMNI-Ciclismo na prescrição de exercícios em cicloergômetro e propor uma nova tabela de conversão entre as escalas.Vinte seis homens (17-41 anos de idade), praticantes de Ciclismo Indoor, pedalaram por 3 minutos, em 6 cargas auto selecionadas correspondentes às categorias de percepção de esforço 9, 11, 13, 15, 17, 19 para Borg, em uma sessão e 2, 4, 5, 7, 8 e 10 para OMNI, emoutra sessão. Ao final de cada estágio, a frequência cardíaca (FC) e a potência (W) foramregistradas. Calculou-se a correlação de Pearson entre as escalas. A correspondência entreas categorias das escalas foi testada pela ANOVA para medidas repetidas, seguida do testede Tuckey (p < 0,05). Foi encontrada alta correlação entre as duas escalas (r = 0,87; P < 0,05)e diferença significativa na FC para as três primeiras categorias. Quanto a W, encontrou-sediferença significativa apenas nas duas primeiras categorias. A conversão testada mostroucorrelação significante. Entretanto, há diferenças significantes na FC para as três primeirascategorias e na W para as duas primeiras. A seguinte correspondência foi proposta: Borg11, 13, 15, 17 e 19; para OMNI 2, 4, 7, 8 e 10.

The Borg and OMNI scales of perceived exertion have been widely validated for the identification of exercise intensity. The objective of this study was to test the agreement between the categories of the Borg (6-20) and OMNI-Cycle scales for the prescription of cycle ergometerexercise and to propose a new conversion table. Twenty-six male indoor cyclists (17-41 years) pedalled for 3 min at six self-selected increasing loads. These loads corresponded to categories 9, 11, 13, 15, 17, and 19 of the Borg scale in one session, and to categories 2, 4, 5, 7, 8, and 10of the OMNI scale in the other session. At the end of each stage, heart rate (HR) and power (W) were recorded. Pearson?s correlation coefficient between scales was calculated. Agreement between the categories of the scales was tested by ANOVA for repeated measures, followed bythe Tukey test (p < 0.05). The correlation between the two scales was high (r = 0.87, p < 0.05). Significant difference between the two scales was observed for HR in the first three categories. W differed significantly only in the first two categories. The conversion tested showed a significant correlation. However, there were significant differences in HR in the first three categories and in W in the first two. The following agreement is proposed: Borg 11, 13, 15, 17, and 19 correspondingto OMNI 2, 4, 7, 8, and 10.