Background—Children with autistic spectrum disorders (ASDs) are frequently hampered by motor impairment. It limits them from regularly practicing physical activities and results in a lower physical fitness even though low cardiorespiratory fitness is one of the most important predictors of all-cause mortality. This study aimed to investigate the cardiorespiratory fitness of boys with ASD compared to typically developed children. Methods—forty male children participated. Twenty were control children (CONT—10.0 ± 1.6 years) and 20 were ASD children (ASD—10.7 ± 1.2 years; intellectual quotient > 70). All participants completed an incremental exercise test on a treadmill. An evaluation of motor characteristics by three tests was conducted (muscular strength; explosive power; flexibility). Assessments of daily physical activity were obtained by questionnaires (PAQ-C) and by actigraphy. Results—in the ASD group, aerobic capacity values (VO_2peak), effort duration and maximal speed were significantly lower compared to CONT (p < 0.05). Flexibility, explosive power and muscular strength were significantly lower in ASD compared to CONT (p < 0.05). Similarities between all children were observed for physical activity evaluation by actigraphy and with the PAQ-C. Conclusions—children with ASD had lower cardiorespiratory fitness than CONT despite similar physical activity levels. Our results suggested that the difference may be due to motor discrepancies.

Background Down syndrome (DS) is a risk factor for metabolic syndrome and cardiovascular disease. The greater oxidative stress described in DS can increase this risk owing to its potential deleterious effects on insulin sensitivity. We hypothesized that metabolic syndrome or its markers, at rest and during exercise, are more pronounced in young adults with DS. Design The study design is that of a controlled study. Methods Thirteen physically active young adults with DS, after overnight polysomnography, plasma-lipid profile, and insulin-resistance [Homeostasis Model Assessment Insulin Resistance (HOMA-IR)] assessments, underwent a sub-maximal progressive treadmill exercise (10 min at 30 and 50%, and 20 min at 75% of Vo_{2 max}), allowing for maximal fat-oxidation rate and blood-oxidative stress determinations. They were compared with 15 healthy control participants (C). Results Vo_{2 max} of DS participants was lower than that of C (60.8 ±2.4 versus 44.4 ± 3.3 ml/kg/min; P < 0.001) but was close to the predicted value (95 ±6%). In DS participants, as expected, oxidative stress was greater than in C (+ 15%; P < 0.001) at rest and all through the exercise protocol. Although a greater fat mass (DS: 19.9 ±1.3%; C: 13.5 ±0.9%; P < 0.001), and a lower insulin sensitivity (HOMA-IR in DS: 1.09±0.16; in C: 0.64±0.13; P < 0.05) was observed for DS participants, a metabolic syndrome could not be shown. Maximal fat-oxidation rate was lower in DS participants (394.2 ±69.9 versus 486.1 ±134.8mg/min in C; P < 0.01), but it was in the normal range. Conclusion Despite greater oxidative stress and lower insulin sensitivity, the DS group involved in our study did not display clear metabolic abnormalities. The young age and lifestyle of this group might, partially, have accounted for this apparently healthy metabolic status.