Fernando Pereira

Reduced exercise capacity in persons with Down syndrome: cause, effect, and management.

Persons with Down syndrome (DS) have reduced peak and submaximal exercise capacity. Because ambulation is one predictor of survival among adults with DS, a review of the current knowledge of the causes, effects, and management of reduced exercise capacity in these individuals would be important. Available data suggest that reduced exercise capacity in persons with DS results from an interaction between low peak oxygen uptake (VO2peak) and poor exercise economy. Of several possible explanations, chronotropic incompetence has been shown to be the primary cause of low VO2peak in DS. In contrast, poor exercise economy is apparently dependent on disturbed gait kinetics and kinematics resulting from joint laxity and muscle hypotonia. Importantly, there is enough evidence to suggest that such low levels of physical fitness (reduced exercise capacity and muscle strength) limit the ability of adults with DS to perform functional tasks of daily living. Consequently, clinical management of reduced exercise capacity in DS seems important to ensure that these individuals remain productive and healthy throughout their lives. However, few prospective studies have examined the effects of structured exercise training in this population. Existent data suggest that exercise training is beneficial for improving exercise capacity and physiological function in persons with DS. This article reviews the current knowledge of the causes, effects, and management of reduced exercise capacity in DS. This review is limited to the acute and chronic responses to submaximal and peak exercise intensities because data on supramaximal exercise capacity of persons with DS have been shown to be unreliable.

Walking economy of adults with down syndrome

This study intended to investigate walking economy (WE) in response to different treadmill speeds and grades in adults with Down syndrome (DS) and in non-disabled controls. Eighteen participants (14 males; 4 females) with DS (33.6+/-7.6 years) and 16 non-disabled (12 males, 4 females) controls (33.3+/-8.0 years) performed submaximal (2.5 km . h (-1) and 4 km . h (-1) at 0% grade; 4 km . h (-1) at 2.5% and 5% grade, for 5 min each) and maximal treadmill tests with metabolic and heart rate measurements. Oxygen uptake (VO(2)) was not different between groups at rest or during the slowest treadmill speed. However, at faster speeds and increased grades, adults with DS presented lower WE than controls (p<0.0001). Subsequent analyses revealed that, despite showing higher delta VO(2) response to the selected speed increments (p<0.0001), individuals with DS produced similar VO(2) increase as controls to grade variations. Therefore, adults with DS exhibit lower WE than non-disabled controls at a speed faster than their preferred walking speed. Additionally, in comparison to controls, individuals with DS show a greater change in energy expenditure with a change in walking speed. In conclusion, lower WE in individuals with DS is mainly related to their inability to adapt efficiently to positive variations in walking speed.

Medidas de composição corporal em adultos portadores de Síndrome de Down

The purpose of the present study was to determine the general level of agreement between the body mass index (BMI), adiposity estimates, waist circumference (WC) assessments, and percentage body fat (BF) measurements by bioelectrical-impedance spectroscopy (BIS) analyses in 20 adult males with Down syndrome (33.5 ± 6.5 years old). BIS was selected as a criterion measure after comparing its estimates with those of dual-energy X-ray absorptiometry (DXA) performed on 10 participants. There were no significant differences between %BF reported by BIS and DXA (p = 0.339) and both measures were moderately correlated (r = 0.71, p = 0.0019). Additionally, %BF estimated by BMI calculations and that obtained by BIS assessments were not significantly different (22.7 ± 4.9% e 23.3 ± 4.6%; t[19] = 0.819, p = 0.219, respectively). Both the BMI and WC were significantly correlated with %BF determined by BIS (p < 0.0001). Furthermore, BMI was significantly associated with %BF measured by BIS (χ2 = 9.7; p = 0.002). As for BMI, WC measurements were significantly associated with %BF obtained by BIS (χ2 = 8.9; p = 0.003). Thus, our main finding is that, both the BMI and WC provide good estimates of body fatness levels in adult males with Down syndrome.

Between-day variability of net and gross oxygen uptake during graded treadmill walking: effects of different walking intensities on the reliability of locomotion economy

There have been few studies of clinical relevance conducted on the reliability of walking economy. This study was designed to determine if walking economy reproducibility increases as a function of walking intensity, and if there is any advantage in expressing walking economy as net oxygen uptake (VO2) rather than gross VO2 for reproducibility purposes. Sixteen participants (9 males, 7 females; mean age, 22.3 +/- 4.3 years) performed resting, submaximal, and maximal protocols on 2 different days, under identical circumstances, within a 7 day period. The submaximal protocol consisted of five 5 min walks (4 km.h-1) at treadmill grades of 0%, 2.5%, 5.0%, 7.5%, and 10%. Findings indicate that increments of 2.5% in treadmill grade effectively increased gross and net VO2 during walks. The reliability of net and gross measures increased as a function of walking relative intensity, reporting intraclass correlation coefficients ranging from 0.89-0.94 and 0.87-0.91, respectively, and mean coefficients of variation (CV) from 7.3%-3.6% and 8.8%-4.4%, respectively. There were no significant differences between the CV for gross and for net VO2 across the spectrum of walking relative intensities. In conclusion, there is no advantage of expressing walking economy as net VO2 instead of gross VO2 for reproducibility purposes, and a single treadmill testing session at a constant speed of 4 km.h-1 is reliable for estimating group and individual walking economy, particularly at higher percent grades.

Sexual dimorphism in the osmopressor response following water ingestion

Compared with men, women exhibit a greater magnitude of increase in resting blood pressure after drinking a single water bolus of 500 ml. Accordingly, our study provides direct evidence of sexual dimorphism in the haemodynamic response to water intake.