Noninvasive assessment of the tension-time index of inspiratory muscles at rest in obese male subjects

Int J Obes (Lond). 2005 Dec;29(12):1478-83. doi: 10.1038/sj.ijo.0803030.


Objective: The aim of this study was to investigate the effect of excessive mechanical load caused by obesity on the inspiratory muscle performance in obese men at rest.

Methods: We therefore measure at rest spirometric flows and the noninvasive tension time index of inspiratory muscle (TTmus = PI/PImax x TI/TTOT) in eight obese male subjects (body mass index (BMI) > 30) and 10 controls.

Results: Spirometric flow (FEV1% pred, FVC% pred) and maximal inspiratory pressure (PImax) were significantly lower in obese subjects compared to controls (P < 0.001). The mean TTmus was significantly higher in obese subjects than in controls (0.136 +/- 0.003 vs 0.045 +/- 0.01). The increase in TTmus was primarily due to an increase in the ratio of mean inspiratory pressure to maximal inspiratory pressure (PI/PImax) and the duty cycle (TI/TTOT). We found a significant negative relationship between PImax and BMI (r = -0.74, P < 0.001), a positive correlation between TTmus and BMI (r = 0.80, P < 0.001) and a negative correlation between TTmus and forced expiratory volume in 1 s (r = -0.85, P < 0.001).

Conclusion: Excessive mechanical load caused by obesity imposes a great burden on the inspiratory muscle, which may predispose such subjects to respiratory muscle weakness at rest.

MeSH terms

  • Adult
  • Body Mass Index
  • Female
  • Forced Expiratory Volume
  • Humans
  • Inspiratory Capacity
  • Male
  • Middle Aged
  • Muscle Fatigue / physiology*
  • Obesity / physiopathology*
  • Respiration Disorders / etiology
  • Respiration Disorders / physiopathology*
  • Respiratory Muscles / physiopathology*
  • Time Factors
  • Vital Capacity