The bigger, the stronger? Insights from muscle architecture and nervous characteristics in obese adolescent girls

International audienceBACKGROUND: Young obese youth are generally stronger than lean youth. This has been linked to the loading effect of excess body mass, acting as a training stimulus comparable to strength training. Whether this triggers specific adaptations of the muscle architecture (MA) and voluntary activation (VA) that could account for the higher strength of obese subjects remains unknown. METHODS: MA characteristics (that is, pennation angle (PA), fascicle length (FL) and muscle thickness (MT)) and muscle size (that is, anatomical cross-sectional area (ACSA)) of the knee extensor (KE) and plantar flexor (PF) muscles were evaluated in 12 obese and 12 non-obese adolescent girls (12-15 years). Maximal isometric torque and VA of the KE and PF muscles were also assessed. RESULTS: Results revealed higher PA (P<0.05), greater MT (P<0.001), ACSA (P<0.01), segmental lean mass (P<0.001) and VA (P<0.001) for KE and PF muscles in obese girls. Moreover, obese individuals produced a higher absolute torque than their lean counterparts on the KE (224.6 +/- 39.5 vs 135.7 +/- 32.7 Nm, respectively; P<0.001) and PF muscles (73.3 +/- 16.5 vs 44.5 +/- 6.2 Nm; P<0.001). Maximal voluntary contraction (MVC) was correlated to PA for the KE (r = 0.46-0.57, P<0.05-0.01) and PF muscles (r = 0.45-0.55, P<0.05-0.01). MVC was also correlated with VA (KE: r = 0.44, Po0.05; PF: r = 0.65, P<0.001) and segmental lean mass (KE: r = 0.48, P<0.05; PF: r = 0.57, Po0.01). CONCLUSIONS: This study highlighted favorable muscular and nervous adaptations to obesity that account for the higher strength of obese youth. The excess of body mass supported during daily activities could act as a chronic training stimulus responsible for these adaptations

The accuracy of bioelectrical impedance to track body composition changes depends on the degree of obesity in adolescents with obesity

International audienc

Effect of Exercise Duration on Subsequent Appetite and Energy Intake in Obese Adolescent Girls

There is a growing interest regarding the effect of exercise on appetite and energy intake in youth. While the role of exercise intensity has been a primary focus of study, the effect of exercise duration on subsequent food intake has not been fully examined in obese adolescents. On three separate mornings in a randomly assigned order, obese adolescent girls (n = 20) aged 12-15 years old were asked to perform a rest session (control, CON) or two cycling sessions for 20 (EX20) or 40 min (EX40) set at their ventilatory threshold. Absolute and relative energy intake were measured from an ad libitum lunch meal 30 min after rest or exercise and appetite feelings assessed using visual analogue scales throughout the day. Hunger, satiety, and prospective food consumption were not significantly different between conditions. Absolute energy intake (kcal) did not differ between conditions, while relative energy intake on EX40 (571 +/- 381 kcal) was significantly lower than during CON (702 +/- 320 kcal; p < .05) and EX20 (736 +/- 457 kcal; p < .05). Fat ingestion (in grams) was significantly lower on CON (7.8 +/- 3.2 g) compared with EX20 (10.3 +/- 4.6 g; p < .01). Protein intake (in grams) was higher on EX20 (37.0 +/- 16.6 g) compared with both CON (29.5 +/- 11.7 g; p < .01) and EX40 (33.1 +/- 10.9 g; p < .05). However, the percentage of total energy derived from each macronutrient was not different between conditions. Obese adolescent girls do not compensate for an acute bout of exercise set at their ventilatory threshold by increasing energy intake, regardless of the exercise duration

Effects of aquatic exercise on appetitive responses in adolescents with obesity: An exploratory study

Aquatic exercise has been suggested as a beneficial modality to improve weight loss, cardiorespiratory fitness and quality of life in adolescents with obesity; however, its impact on appetite control in youth remains unknown. The aim of this preliminary study was to examine the effect of an acute aquatic exercise session on energy intake (EI), appetite feelings and food reward in adolescents with obesity. Twelve adolescents with obesity (12–16 years, Tanner stage 3–5, 9 males) randomly completed two conditions: i) control (CON); ii) aquatic exercise session (AQUA). One hour before lunch, the adolescents stayed at rest outside the water in a quiet room for 45 min on CON while they performed a 45-min aquatic exercise session on AQUA. Ad libitum EI and macronutrients were assessed at lunch and dinner, subjective appetite feelings taken at regular intervals, and food reward measured before and after lunch. Paired T-test showed that EI was not different between CON and AQUA at lunch (1333 ± 484 kcal vs 1409 ± 593 kcal; p = 0.162) and dinner (528 ± 218 kcal vs 513 ± 204 kcal; p = 0.206). Total daily ad libitum EI was significantly higher on AQUA (1922 ± 649 kcal) compared with CON (1861 ± 685 kcal; p = 0.044) but accounting for the exercise-induced energy expenditure, relative energy intake did not differ (2263 ± 732 kcal vs 2117 ± 744 kcal, p = 0.304). None of the appetite feelings (hunger, fullness, prospective food consumption and desire to eat) and food reward dimensions were significantly different between conditions. These preliminary and exploratory results suggest that an acute aquatic-exercise session might not induce energy compensatory responses in adolescents with obesity

Improved walking energy efficiency might persist in presence of simulated full weight regain after multidisciplinary weight loss in adolescents with obesity: the POWELL study

International audienc