No abstract

Muscular activation, as well as neuromuscular fatigue, varies as a function of relative BFR intensity. Therefore, the individual determination of vascular restriction levels is crucial before engaging in BFR exercise.

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.

Low work capacity and V˙O2peak commonly are described phenomena in Down syndrome. This is accompanied by chronotropic incompetence and a high incidence of obesity. Although many causes of low work capacity in Down syndrome have been proposed, little scientific support exists. Our working hypothesis is that autonomic dysfunction is the major contributor to the low levels of work capacity in this population.

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 (a1). 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 a1 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.Résumé : Comparativement aux hommes du même âge, les femmes présentent une plus grande variabilité de l'intervalle RR. Une meilleure stimulation parasympathique en matière de régulation cardiaque n'est pas seulement plus importante chez les femmes, mais leur confère aussi une protection en périodes de stress cardiaque. Même si les femmes semblent disposer d'un meilleur profil autonome du coeur après la fin d'un exercice, il y a très peu d'études sur ce sujet. Cette étude analyse la réponse autonome du coeur des participants masculins et féminins au cours de la première phase de récupération d'un exercice physique d'intensité supramaximale. Vingt-cinq individus âgés de 20 à 33 ans (12 femmes, 13 hommes) participent au test de Wingate d'une durée de 30 s. Des enregistrements ECG permettent d'obtenir un ensemble de pointes RR avant le début du test et 5 min après la fin du test, au repos couché et dans une condition de contrôle respiratoire. On fait des analyses linéaires (analyse spectrale) et des analyses non linéaires (analyse des fluctuations redressées ou DFA) sur les mêmes ensembles de pointe RR. Au repos, les femmes présentent une puissance plus faible des basses fréquences (LF) brutes, mais une plus grande puissance des hautes fréquences (HF) normalisées. Dans ces conditions, le ratio LF/HF des femmes est aussi plus faible que celui des hommes (p < 0,05), mais l'exposant d'échelle (a 1 ) à court terme n'e...