Heart Rate Dynamics after Exercise in Cardiac Patients with and without Type 2 Diabetes

4-week stretching program after submaximal strength exercise affects performance but not heart rate variability and lactate clearance. An exploratory study

Previous research has demonstrated that stretching can enhance athletic performance and induce cardiovascular adaptations. This study aims to assess whether a 4-week preventative stretching routine can enhance heart rate variability and heart rate recovery, faster blood lactate clearance, and improve performance following submaximal strength exercises. Twenty-four healthy adults were recruited and randomly allocated to either the experimental group or the control group. Both groups engaged in submaximal strength exercises (5 sets to voluntary failure at 60% of 1RM) comprising bench press and back squat exercises under baseline conditions and after stretching protocol. The experimental group followed the Stretching Protocol, while the control group adhered to their regular training routine. ANOVA analysis revealed a significant pre-post interaction effect between groups in the variable of squat repetitions, although no notable pre- or post-differences were observed in heart rate variability, heart rate recovery, blood lactate concentration, or bench repetitions in either group. A 4-week preventative stretching program does not appear adequate to enhance lactate clearance and cardiovascular adaptation after submaximal strength exercises in resistance-trained individuals compared to the control group. However, it is plausible that such a stretching routine may mitigate muscle fatigue, though further investigation is warranted to substantiate this hypothesis.

Progressive resistance training ameliorates deteriorating cardiac autonomic dysfunction, subclinical inflammation and endothelial dysfunction in type 2 diabetes mellitus: A randomized control trial

BACKGROUND AND AIMS

To investigate the effect of resistance training (RT) on outcomes of cardiac autonomic control, biomarkers of subclinical inflammation, endothelial dysfunction, and angiotensin II in T2DM patients with CAN.

METHODS

Fifty six T2DM patients with CAN were recruited in the present study.After baseline assessment of all outcome variables, patients were randomly allocated into two groups - RT (n = 28) and Control (n = 28). The experimental group underwent 12 weeks of RT and the control group received usual care. RT was performed at an intensity of 65%-75% of 1 RM, 3 times/week for 12 weeks. RT program included 10 exercises of major muscle groups in the body. Cardiac autonomic control parameters, subclinical inflammation and endothelial dysfunction biomarkers, and serum angiotensin II concentration were assessed at baseline and after 12 weeks.

RESULTS

Parameters of cardiac autonomic control showed significant improvement after RT (p < 0.05). Interleukin-6, interleukin-18 were significantly reduced while endothelial nitric oxide synthase was significantly increased post-RT (p < 0.05).

CONCLUSIONS

Findings of the present study suggest that RT has the potential to enhance deteriorating cardiac autonomic function in T2DM patients with CAN. RT also seems to have an anti-inflammatory role and it may also play some role in vascular remodeling in these patients.

TRIAL REGISTRATION

CTRI/2018/04/013321, Registered prospectively on 13th April 2018, Clinical Trial Registry, India.

Acute glycaemic management before, during and after exercise for cardiac rehabilitation participants with diabetes mellitus: a joint statement of the British and Canadian Associations of Cardiovascular Prevention and Rehabilitation, the International Council for Cardiovascular Prevention and Rehabilitation and the British Association of Sport and Exercise Sciences

Type 1 (T1) and type 2 (T2) diabetes mellitus (DM) are significant precursors and comorbidities to cardiovascular disease and prevalence of both types is still rising globally. Currently,~25% of participants (and rising) attending cardiac rehabilitation in Europe, North America and Australia have been reported to have DM (>90% have T2DM). While there is some debate over whether improving glycaemic control in those with heart disease can independently improve future cardiovascular health-related outcomes, for the individual patient whose blood glucose is well controlled, it can aid the exercise programme in being more efficacious. Good glycaemic management not only helps to mitigate the risk of acute glycaemic events during exercising, it also aids in achieving the requisite physiological and psycho-social aims of the exercise component of cardiac rehabilitation (CR). These benefits are strongly associated with effective behaviour change, including increased enjoyment, adherence and self-efficacy. It is known that CR participants with DM have lower uptake and adherence rates compared with those without DM. This expert statement provides CR practitioners with nine recommendations aimed to aid in the participant's improved blood glucose control before, during and after exercise so as to prevent the risk of glycaemic events that could mitigate their beneficial participation.

Post-Exercise Hypotension and Reduced Cardiac Baroreflex after Half-Marathon Run: In Men, but Not in Women

We examined whether trained women exhibit similar cardiovascular and cardiac baroreflex alterations after a half-marathon compared to men. Thirteen women (39.1 ± 9.3 years; 165 ± 6 cm; 58.2 ± 7.5 kg; maximal aerobic speed (MAS): 13.7 ± 2.2 km·h^-1) and 12 men (45.7 ± 10.5 years; 178 ± 7 cm; 75.0 ± 8.3 kg; MAS: 15.8 ± 2.2 km·h^-1) ran an official half-marathon. Before and 60-min after, cardiovascular variables, parasympathetic (heart rate variability analysis) modulation and cardiac baroreflex function (transfer function and sequence analyses) were assessed during supine rest and a squat-stand test. Running performance was slower in women than in men (120 ± 19 vs. 104 ± 14 min for women and men, respectively). However, when expressed as a percentage of MAS, it was similar (78.1 ± 4.6% and 78.2 ± 5.4% of MAS for women and men, respectively). Before the run, women exhibited lower mean blood pressure (BP), cardiac output (CO) and stroke volume (SV) compared to men, together with higher parasympathetic indexes. After the race, parasympathetic indexes decreased in both sexes, but remained higher in women. Reduced SV, systolic BP and cardiac baroreflex were observed in men but not in women. Contrary to men, a competitive half-marathon did not trigger post-exercise hypotension and a reduced cardiac baroreflex in women.

Associations Between Heart Rate Recovery Dynamics With Estradiol Levels in 20 to 60 Year-Old Sedentary Women

It is hypothesized that estradiol levels, as well as aging, influence cardiac autonomic function in women. The main aim of this study was to test the correlations between heart rate recovery (HRR) dynamics, as a proxy of cardiac autonomic function, with estradiol levels and age in women. This cross-sectional study involved 44 healthy women. Heart rate (HR) data were obtained beat-by-beat during the entire experiment. Maximal incremental exercise testing (IET) on a cycle ergometer was performed followed by 6 min of recovery. During the IET recovery period, the overall HRR dynamics were evaluated by exponential data modeling (time constant "τ") where shorter τ indicates faster HRR adjustment. Considering the cardiac autonomic complexity, HRR dynamics were also evaluated by delta (Δ) analysis considering different HR data intervals. The relationship between HRR dynamics, estradiol levels and age was tested by Pearson product-moment correlation. The overall HRR dynamics (i.e., τ) were statistically correlated with age (r = 0.58, p < 0.001) and estradiol levels (r = -0.37, p = 0.01). The Δ analysis showed that the slower overall HRR associated with aging was a consequence of slower dynamics occurring within the 45-210 s interval, indicating slower sympathetic withdrawal. In conclusion, aging effects on HRR in women seems to be correlated with a slower sympathetic withdrawal. In addition, the cardioprotective effect previously associated with estradiol seems not to influence the autonomic modulation during exercise recovery periods in women.

Accuracy of the Garmin 920 XT HRM to perform HRV analysis

Heart rate variability (HRV) analysis is widely used to investigate autonomous cardiac drive. This method requires periodogram measurement, which can be obtained by an electrocardiogram (ECG) or from a heart rate monitor (HRM), e.g. the Garmin 920 XT device. The purpose of this investigation was to assess the accuracy of RR time series measurements from a Garmin 920 XT HRM as compared to a standard ECG, and to verify whether the measurements thus obtained are suitable for HRV analysis. RR time series were collected simultaneously with an ECG (Powerlab system, AD Instruments, Castell Hill, Australia) and a Garmin XT 920 in 11 healthy subjects during three conditions, namely in the supine position, the standing position and during moderate exercise. In a first step, we compared RR time series obtained with both tools using the Bland and Altman method to obtain the limits of agreement in all three conditions. In a second step, we compared the results of HRV analysis between the ECG RR time series and Garmin 920 XT series. Results show that the accuracy of this system is in accordance with the literature in terms of the limits of agreement. In the supine position, bias was 0.01, - 2.24, + 2.26 ms; in the standing position, - 0.01, - 3.12, + 3.11 ms respectively, and during exercise, - 0.01, - 4.43 and + 4.40 ms. Regarding HRV analysis, we did not find any difference for HRV analysis in the supine position, but the standing and exercise conditions both showed small modifications.

Caffeine delays autonomic recovery following acute exercise

BACKGROUND

Impaired autonomic recovery of heart rate (HR) following exercise is associated with an increased risk of sudden death. Caffeine, a potent stimulator of catecholamine release, has been shown to augment blood pressure (BP) and sympathetic nerve activity; however, whether caffeine alters autonomic function after a bout of exercise bout remains unclear.

METHODS

In a randomized, crossover study, 18 healthy individuals (26 ± 1 years; 23.9 ± 0.8 kg·m(-2)) ingested caffeine (400 mg) or placebo pills, followed by a maximal treadmill test to exhaustion. Autonomic function and ventricular depolarization/repolarization were determined using heart rate variability (HRV) and corrected QT interval (QTc), respectively, at baseline, 5, 15, and 30 minutes post-exercise.

RESULTS

Maximal HR (HRmax) was greater with caffeine (192 ± 2 vs. 190 ± 2 beat·min(-1), p < 0.05). During recovery, HR, mean arterial pressure (MAP), and diastolic blood pressure (DBP) remained elevated with caffeine (p < 0.05). Natural log transformation of low-to-high frequency ratio (LnLF/LnHF) of HRV was increased compared with baseline at all time points in both trials (p < 0.05), with less of an increase during 5 and 15 minutes post-exercise in the caffeine trial (p < 0.05). QTc increased from baseline at all time points in both trials, with greater increases in the caffeine trial (p < 0.05).

CONCLUSIONS

Caffeine ingestion disrupts post-exercise autonomic recovery because of increased sympathetic nerve activity. The prolonged sympathetic recovery time could subsequently hinder baroreflex function during recovery and disrupt the stability of autonomic function, potentiating a pro-arrhythmogenic state in young adults.

Improvements in heart rate recovery among women after cardiac rehabilitation completion

BACKGROUND

Heart rate recovery (HRR) after exercise cessation is thought to reflect the rate of reestablishment of parasympathetic tone. Relatively little research has focused on improved HRR in women after completing cardiac rehabilitation (CR) exercise training.

OBJECTIVE

We examined the influence of exercise training on HRR in women completing a traditional CR program and in women completing a CR program tailored for women.

METHODS

A 2-group randomized clinical trial compared HRR between 99 women completing a traditional 12-week CR program and 137 women completing a tailored CR program. Immediately upon completion of a symptom-limited graded exercise test, HRR was measured at 1 through 6 minutes.

RESULTS

Compared with baseline, improvement in 1-minute HRR (HRR1) was similar (P = 0.777) between the tailored (mean [SD], 17.5 [11] to 19.1 [12]) and the traditional CR program (15.7 [9.0] to 16.9 [9.5]). The amount of change in the 2-minute HRR (HRR2) for the tailored (30 [13] to 32.8 [14.6]) and traditional programs (28.3 [12.8] to 31.2 [13.7]) also was not different (P = 0.391). Similar results were observed for HRR at 3 through 6 minutes. Given these comparable improvements of the 2 programs, in the full cohort, the factors independently predictive of post-CR HRR1, in rank order, were baseline HRR1 (part correlation, 0.35; P < 0.001); peak exercise capacity, estimated as metabolic equivalents (METs; 0.24, P < 0.001); anxiety (-0.17, P = 0.001); and age (-0.13, P = 0.016). The factors independently associated with post-CR HRR2 were baseline HRR2 (0.44, P < 0.001), peak METs (0.21, P < 0.001), and insulin use (-0.10, P = 0.041).

CONCLUSIONS

One to 6 minutes after exercise cessation, HRR was significantly improved among the women completing both CR programs. The modifiable factors positively associated with HRR1 included peak METs and lower anxiety, whereas HRR2 was associated with insulin administration and peak METs. Additional research on HRR after exercise training in women is warranted.

Association of cardiovascular risk using non-linear heart rate variability measures with the framingham risk score in a rural population

Cardiovascular risk can be calculated using the Framingham cardiovascular disease (CVD) risk score and provides a risk stratification from mild to very high CVD risk percentage over 10 years. This equation represents a complex interaction between age, gender, cholesterol status, blood pressure, diabetes status, and smoking. Heart rate variability (HRV) is a measure of how the autonomic nervous system (ANS) modulates the heart rate. HRV measures are sensitive to age, gender, disease status such as diabetes and hypertension and processes leading to atherosclerosis. We investigated whether HRV measures are a suitable, simple, noninvasive alternative to differentiate between the four main Framingham associated CVD risk categories. In this study we applied the tone-entropy (T-E) algorithm and complex correlation measure (CCM) for analysis of HRV obtained from 20 min. ECG recordings and correlated the HRV score with the stratification results using the Framingham risk equation. Both entropy and CCM had significant analysis of variance (ANOVA) results [F (172, 3) = 9.51; <0.0001]. Bonferroni post hoc analysis indicated a significant difference between mild, high and very high cardiac risk groups applying tone-entropy (p < 0.01). CCM detected a difference in temporal dynamics of the RR intervals between the mild and very high CVD risk groups (p < 0.01). Our results indicate a good agreement between the T-E and CCM algorithm and the Framingham CVD risk score, suggesting that this algorithm may be of use for initial screening of cardiovascular risk as it is noninvasive, economical and easy to use in clinical practice.