Effects of a Multidisciplinary Body Weight Reduction Program on Static and Dynamic Thoraco-Abdominal Volumes in Obese Adolescents

The objective of this study was to characterize static and dynamic thoraco-abdominal volumes in obese adolescents and to test the effects of a 3-week multidisciplinary body weight reduction program (MBWRP), entailing an energy-restricted diet, psychological and nutritional counseling, aerobic physical activity, and respiratory muscle endurance training (RMET), on these parameters. Total chest wall (V-CW), pulmonary rib cage (V-RC,V-p), abdominal rib cage (V-RC,V-a), and abdominal (V-AB) volumes were measured on 11 male adolescents (Tanner stage: 3-5; BMI standard deviation score: >2; age: 15.9 +/- 1.3 years; percent body fat: 38.4%) during rest, inspiratory capacity (IC) maneuver, and incremental exercise on a cycle ergometer at baseline and after 3 weeks of MBWRP. At baseline, the progressive increase in tidal volume was achieved by an increase in end-inspiratory V-CW (p < 0.05) due to increases in V-RC,V-p and V-RC,V-a with constant V-AB. End-expiratory V-CW decreased with late increasing V-RC,V-p, dynamically hyperinflating V-RC,V-a (p < 0.05), and progressively decreasing V-AB (p < 0.05). After MBWRP, weight loss was concentrated in the abdomen and total IC decreased. During exercise, abdominal rib cage hyperinflation was delayed and associated with 15% increased performance and reduced dyspnea at high workloads (p < 0.05) without ventilatory and metabolic changes. We conclude that otherwise healthy obese adolescents adopt a thoracoabdominal operational pattern characterized by abdominal rib cage hyperinflation as a form of lung recruitment during incremental cycle exercise. Additionally, a short period of MBWRP including RMET is associated with improved exercise performance, lung and chest wall volume recruitment, unloading of respiratory muscles, and reduced dyspnea.