Fernando D. Pereira

Effects of Combined Aerobic and Resistance Exercise Training in Adults With and Without Down Syndrome

OBJECTIVE To determine whether adults with Down syndrome (DS) could improve their submaximal and peak exercise capacity, as for adults without disabilities, after 12 weeks of combined (aerobic and resistance) exercise training. DESIGN Prospective study comparing the effects of a 12-week combined exercise program on submaximal and peak exercise capacity of adults with and without DS. SETTING University facilities. PARTICIPANTS Participants with DS (n=13; mean ± SD age, 36.5±5.5y) and participants without disabilities (n=12; mean age, 38.7±8.3y). INTERVENTIONS Combined exercise training for 12 weeks. Endurance training was performed 3 days a week for 30 minutes at 65% to 85% of peak oxygen consumption (Vo₂peak). Resistance training was prescribed for 2 days a week and consisted of 2 rotations in a circuit of 9 exercises at 12-repetition maximum. MAIN OUTCOME MEASURES Submaximal and maximal graded exercise tests with metabolic and heart rate measurements. Walking economy and Vo₂peak were considered the main outcomes. RESULTS Participants with DS and those without disabilities showed similar values for body mass index and relative fat mass at pre- and posttraining periods. Walking economy and Vo₂peak overall were lower in participants with DS than participants without disabilities (P<.05). Training improved walking economy and Vo₂peak in participants with DS and those without disabilities (P<.05); additionally, the magnitude of changes induced by training was similar between groups. CONCLUSIONS Overall, a 12-week combined exercise regimen induced gains of similar magnitude between adults with and without DS for submaximal and peak exercise capacity.

Sex differences in linear and nonlinear heart rate variability during early recovery from supramaximal exercise.

Women demonstrate greater RR interval variability than men of similar age. Enhanced parasympathetic input into cardiac regulation appears to be not only greater in women, but also protective during periods of cardiac stress. Even though women may have a more favorable autonomic profile after exercise, little research has been conducted on this issue. This study was designed to examine the cardiac autonomic response, in both male and female participants, during the early recovery from supramaximal exercise. Twenty-five individuals, aged 20 to 33 years (13 males and 12 females), performed a 30-s Wingate test. Beat-to-beat RR series were recorded before and 5 min after exercise, with the participants in the supine position and under paced breathing. Linear (spectral analysis) and nonlinear analyses (detrended fluctuation analysis (DFA)) were performed on the same RR series. At rest, women presented lower raw low frequency (LF) power and higher normalized high frequency (HF) power. Under these conditions, the LF/HF ratio of women was also lower than that of men (p<0.05), but there were no differences in the short-term scaling exponent (α1). Even though both sexes showed a significant modification in linear and nonlinear measures of heart rate variability (HRV) (p<0.05), women had a greater change in LF/HF ratio and α1 than men from rest to recovery. This study demonstrates that the cardiac autonomic function of women is more affected by supramaximal exercise than that of men. Additionally, DFA did not provide additional information about sexual dimorphisms, compared with conventional spectral HRV techniques.

Heart Rate Recovery and Variability Following Combined Aerobic and Resistance Exercise Training in Adults with and without Down Syndrome.

Persons with Down syndrome (DS) are at high risk for cardiovascular morbidity and mortality, and there is compelling evidence of autonomic dysfunction in these individuals. The main purpose of this study was to determine whether a combined aerobic and resistance exercise intervention produces similar results in cardiac autonomic function between adults with and without DS. Twenty-five participants (13 DS; 12 non-DS), aged 27-50 years, were included. Aerobic training was performed 3 days/week for 30 min at 65-85% of peak oxygen uptake (VO(2peak)). Resistance training was prescribed for 2 days/week and consisted of two rotations in a circuit of 9 exercises at 12-repetition-maximum. There was a significant improvement in the VO(2peak) and muscle strength of participants with and without DS after training. Heart rate recovery improved at 1 min post-exercise, but only in participants with DS. Both groups of participants exhibited a similar increase in normalized high frequency power and of decrease in normalized low frequency power after training. Therefore, 12 weeks of exercise training enhanced the heart rate recovery in adults with DS, but not in those without DS. Contrasting, the intervention elicited similar gains between groups for cardiovagal modulation.

Effects of cigarette smoking on cardiac autonomic function during dynamic exercise

Abstract The purpose of this study was to investigate the acute effect of cigarette smoking on cardiac autonomic function in young adult smokers during dynamic exercise. Fourteen healthy young smokers (21.4 ± 3.4 years) performed peak and submaximal exercise protocols under control and smoking conditions. Resting and submaximal beat-to-beat R-R series were recorded and spectrally decomposed using the fast Fourier transformation. Smoking resulted in a significant decrease in work time, [Vdot]O2peak and peak O2 pulse (P < 0.05). Heart rate increased at rest and during submaximal exercise after smoking (P < 0.05). The raw high frequency and low frequency power were significantly reduced by smoking, both at rest and during exercise (P < 0.05). The low to high frequency ratio was higher after smoking (P < 0.05). The normalised low frequency power was also significantly increased by smoking, but only at rest (P < 0.05). These data demonstrate that the tachycardic effect elicited by smoking is accompanied by acute changes in heart rate spectral components both at rest and during exercise. Therefore, the cardiac autonomic control is altered by smoking not only at rest, but also during exercise, resulting in reduced vagal modulation and increased sympathetic dominance.

Cardiac autonomic function during submaximal treadmill exercise in adults with Down syndrome

This study determined whether the cardiac autonomic function of adults with Down syndrome (DS) differs from that of nondisabled persons during submaximal dynamic exercise. Thirteen participants with DS and 12 nondisabled individuals performed maximal and submaximal treadmill tests with metabolic and heart rate (HR) measurements. Spectral analysis of HR variability was performed on the last 256 consecutive R-R intervals obtained under the following conditions: (1) rest, (2) submaximal treadmill exercise (at constant relative intensity below the ventilatory threshold) and (3) recovery. Participants with DS presented lower chronotropic response than those without DS to peak and submaximal exercise (p<0.05). Nevertheless, the fractional utilization of peak HR during treadmill walking was similar between groups (∼60% peak HR). Even though there were no between-group differences at rest or during recovery, the participants with DS showed a higher LF/HF ratio during exercise (p<0.05). Similarly, the LF power of participants with DS during exercise was greater than that of nondisabled participants (p<0.05). In contrast, both groups exhibited similar HF power at each physiological condition. In conclusion, these findings suggest that adults with DS demonstrate appropriate vagal withdrawal, but heightened sympathetic modulation of HR variability at ∼60% of their peak HR. Despite this, the absolute change in HR from rest to exercise was attenuated in these individuals compared to persons without disabilities. This indicates that DS may be associated with poor cardiac responsiveness to changes in autonomic modulation during exercise at intensities below the ventilatory threshold.

Heart rate recovery after exercise in adults with the Down syndrome.

The main purpose of this study was to evaluate heart rate recovery (HRR) in patients with the Down syndrome (DS) after peak dynamic exercise and compare their responses to those of nondisabled subjects of similar age, gender, and body mass index. Eighteen participants with the DS (14 men, 4 women; mean age 33.6 +/- 7.6 years) and 18 nondisabled controls (14 men, 4 women; mean age 33.8 +/- 8.5 years) performed peak treadmill tests with metabolic and heart rate measurements. Compared to controls, subjects with the DS presented lower peak values of heart rate, oxygen uptake, and minute ventilation (p <0.05). In contrast, the 2 groups attained similar respiratory exchange ratio values at peak exercise. Even after controlling for the effects of reduced peak heart rate and body mass index, participants with the DS showed slower HRR than controls at 1 minute (DS: 25.3 +/- 7.2 beats/min; controls: 34.1 +/- 12.1 beats/min) and 2 minutes (DS: 36.3 +/- 5.8 beats/min; controls: 53.6 +/- 14.1 beats/min) of recovery (p <0.05). In conclusion, adults with the DS had reduced HRR (at 1 and 2 minutes of recovery) compared to nondisabled controls, and this was independent of their lower chronotropic response to peak exercise. Additionally, despite showing attenuated HRR from peak exercise, adults with the DS did not present increased cardiovascular risk by general diagnostic criteria (HRR >12 and 22 beats/min, respectively).

Fractal scaling properties of heart rate dynamics in persons with Down syndrome

It has been shown that the fractal scaling properties of heart rate dynamics, in healthy aging, differ from that seen in heart disease and this favors the use of fluctuation measures as diagnostic tools. The purpose of this study was to evaluate the fractal heart rate dynamics in adults with Down syndrome (DS) under different physiological conditions (rest, exercise and post-exercise recovery) and compare their responses with those of nondisabled individuals. Fourteen participants (10 males; and 4 females) with DS and 13 nondisabled (9 males, and 4 females) controls performed maximal and submaximal treadmill tests with metabolic and heart rate measurements. Detrended fluctuation analysis was performed on the last 256 consecutive R-R intervals obtained under the following conditions: (1) standing rest, (2) submaximal treadmill exercise and (3) standing post-exercise recovery. Participants with DS presented lower chronotropic response than controls to peak and submaximal exercise (p<0.05). The short-term scaling exponent (α(1)) was greater in the DS group at rest (1.29±0.06 vs 1.07±0.08), during exercise (1.24±0.09 vs 0.99±0.08) and recovery (1.31±0.06 vs 1.21±0.06) (p<0.05). Furthermore, the fractal scaling distance score (I1-α(1)I) of participants with DS was also greater than that of controls under each physiological condition (p<0.05). This confirmed their greater fractal distance from the healthy value of 1.0. In conclusion, adults with DS show a breakdown of scale-invariant organization in heart rate dynamics towards Brownian noise and this is similar to that described in healthy aging.

Cardiovascular and autonomic effects of water ingestion during postexercise circulatory occlusion.

As with water ingestion, the activation of the muscle metaboreflex leads to heightened muscle sympathetic nerve activity. Thus, we hypothesized that water ingestion might enhance the pressor effect of the muscle metaboreflex activation. We examined the effect of water ingestion (50 vs. 500 mL) on the cardiovascular and autonomic responses to static handgrip followed by postexercise circulatory occlusion (PECO) in 19 healthy participants (29.2 ± 8.6 years). Beat-to-beat blood pressure, baroreflex sensitivity (BRS), and R-R intervals were recorded in both conditions (pre- and postingestion). Changes in stroke volume and cardiac output were assessed using Modelflow. Cardiac autonomic regulation was investigated by spectral heart rate variability (HRV); baroreflex control of heart rate was assessed by the sequence method. Water ingestion did not increase the pressor effect induced by PECO. Even though 500 mL of water elicited an overall bradycardia, paired by an increase in the high-frequency HRV, there were no differences between conditions for the decrease in BRS or the resetting of the baroreflex to operate at higher blood pressure. Nevertheless, after the ingestion of 500 mL of water, there were no significant correlations between the percent change in cardiac output and that of BRS, from rest to PECO. This contrasts with that seen in the 50 mL condition (r = -0.68, p < 0.05). Contrasting with our hypothesis, 500 mL of water did not increase the pressor effect induced by PECO. Nevertheless, we found that water ingestion may influence the mechanisms by which the muscle metaboreflex elicits an increased cardiac output during PECO.