Exercise training improves breathing strategy and performance during the six-minute walk test in obese adolescents.

OBJECTIVES: We aimed to examine ventilatory responses during the six-minute walk test in healthy-weight and obese adolescents before and after exercise training. METHODS: Twenty obese adolescents (OB) (age: 14.5±1.7 years; BMI: 34.0±4.7kg·m(-2)) and 20 age and gender-matched healthy-weight adolescents (HW) (age: 15.5±1.5 years; BMI: 19.9±1.4kg·m(-2)) completed six-minute walk test during which breath-by-breath gas analysis and expiratory flow limitation (expFL) were measured. OB participated in a 12-week exercise-training program. RESULTS: Comparison between HW and OB participants showed lower distance achieved during the 6MWT in OB (-111.0m, 95%CI: -160.1 to 62.0, p<0.05) and exertional breathlessness was greater (+0.78 a.u., 95%CI: 0.091-3.27, p=0.039) when compared with HW. Obese adolescents breathed at lower lung volumes, as evidenced by lower end expiratory and end inspiratory lung volumes during exercise (p<0.05). Prevalence of expFL (8 OB vs 2 HW, p=0.028) and mean expFL (14.9±21.9 vs 5.32±14.6% VT, p=0.043, in OB and HW) were greater in OB. After exercise training, mean increase in the distance achieved during the 6MWT was 64.5 meters (95%CI: 28.1-100.9, p=0.014) and mean decrease in exertional breathlessness was 1.62 (95%CI: 0.47-2.71, p=0.05). Obese adolescents breathed at higher lung volumes, as evidenced by the increase in end inspiratory lung volume from rest to 6-min exercise (9.9±13.4 vs 20.0±13.6%TLC, p<0.05). Improved performance was associated with improved change in end inspiratory lung volume from rest to 6-min exercise (r=0.65, p=0.025). CONCLUSION: Our results suggest that exercise training can improve breathing strategy during submaximal exercise in obese adolescents and that this increase is associated with greater exercise performance.

Ventilatory responses to exercise training in obese adolescents.

The aim of this study was to examine ventilatory responses to training in obese adolescents. We assessed body composition, pulmonary function and ventilatory responses (among which expiratory flow limitation and operational lung volumes) during progressive cycling exercise in 16 obese adolescents (OB) before and after 12 weeks of exercise training and in 16 normal-weight volunteers. As expected, obese adolescents' resting expiratory reserve volume was lower and inversely correlated with thoraco-abdominal fat mass (r = -0.74, p<0.0001). OB presented lower end expiratory (EELV) and end inspiratory lung volumes (EILV) at rest and during submaximal exercise, and modest expiratory flow limitation. After training, OB increased maximal aerobic performance (+19%) and maximal inspiratory pressure (93.7±31.4 vs. 81.9±28.2 cm H2O, +14%) despite lack of decrease in trunk fat and body weight. Furthermore, EELV and EILV were greater during submaximal exercise (+11% and +9% in EELV and EILV, respectively), expiratory flow limitation delayed but was not accompanied by increased V(T). However, submaximal exertional symptoms (dyspnea and leg discomfort) were significantly decreased (-71.3% and -70.7%, respectively). Our results suggest that exercise training can improve pulmonary function at rest (static inspiratory muscle strength) and exercise (greater operating lung volumes and delayed expiratory flow limitation) but these modifications did not entirely account for improved dyspnea and exercise performance in obese adolescents.