Original Article
International Journal of Obesity (2007) 31, 1456–1463; doi:10.1038/sj.ijo.0803546; published online 26 June 2007
Inspiratory muscle activity during incremental exercise in obese men
M Chlif1, D Keochkerian1, Y Feki2, A Vaidie3, D Choquet1,4 and S Ahmaidi1
- 1EA 3300 'APS and Motor Patterns: Adaptations-Rehabilitation', Faculté des Sciences du Sport, Sport Science Department, Picardie Jules Verne University, Amiens Cedex, France
- 2Laboratoire de Physiologie de la Nutrition, Faculté des Sciences de Tunis, Tunis, Tunisia
- 3Department of Nutritional and Physical Rehabilitation, Corbie's Hospital, Corbie, France
- 4Department of Cardiac Rehabilitation, Corbie's Hospital, Corbie, France
Correspondence: Professor S Ahmaidi, Faculté des Sciences du Sport, Allée P. Grousset, Campus Universitaire du Bailly, F-80025, Amiens Cedex. France. E-mail: mehdi.chlif@u-picardie.fr; said.ahmaidi@u-picardie.fr
Received 2 August 2006; Revised 5 November 2006; Accepted 6 November 2006; Published online 26 June 2007.
Abstract
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 (TT0.1). We studied 17 obese subjects (mean age
s.d.; 4913 years) and 14 control subjects (4216) during an incremental, maximal exercise test.
Methods:
Measurements included anthropometric parameters, spirometry, breathing patterns and inspiratory muscle activity. TT0.1 was calculated using the equation TT0.1=P0.1/PImax 
TI/TTOT (where P0.1 is mouth occlusion pressure, PImax is maximal inspiratory pressure and TI/TTOT is the duty cycle).
Results:
At same levels of maximal exercise (%Wmax) (20, 40, 60, 80, 100% Wmax), obese subjects showed higher P0.1 (P<0.001) and P0.1/PImax (P<0.001) values than controls. TT0.1 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. TT0.1 may be useful in our understanding concerning the benefits of endurance training.
Keywords:
dyspnoea, maximal inspiratory pressure, neural drives, respiratory muscle capacity, exercise
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