Inspiratory muscle activity during incremental exercise in obese men

Objective: The aim of this study was to assess overall inspiratory muscle activity during incremental exercise in obese men and healthy controls using the non-invasive, inspiratory muscle tension-time index (T-T0.1). We studied 17 obese subjects ( mean age +/- s.d.; 49713 years) and 14 control subjects ( 42716) during an incremental, maximal exercise test. Methods: Measurements included anthropometric parameters, spirometry, breathing patterns and inspiratory muscle activity. T-T0.1 was calculated using the equation T-T0.1=P-0.1/P(Imax)xT(I)/T-TOT (where P-0.1 is mouth occlusion pressure, P-Imax is maximal inspiratory pressure and T-I/T-TOT is the duty cycle). Results: At same levels of maximal exercise (%W-max) (20, 40, 60, 80, 100% W-max), obese subjects showed higher P-0.1 (P<0.001) and P-0.1/P-Imax (P<0.001) values than controls. T-T0.1 was thus higher in obese subjects for each workload increment and at maximal exercise (P<0.001). Conclusions: During exercise, patients with obesity show alterations in inspiratory muscle activity as a result of both reduced inspiratory strength (as measured by maximal inspiratory pressure) and increased ventilatory drive ( as reflected by mouth occlusion pressure), which prone obese subject to respiratory muscle weakness. Our results suggest that impaired respiratory muscle activity could contribute to a decrease in exercise capacity. T-T0.1 may be useful in our understanding concerning the benefits of endurance training.