Exercise-induced depression of the diaphragm motor evoked potential is not affected by non-invasive ventilation

Respir Physiol Neurobiol. 2007 Mar 15;155(3):243-54. doi: 10.1016/j.resp.2006.06.007. Epub 2006 Jun 23.


Whole body exercise is followed by a depression of the diaphragm motor evoked potential (MEP). It is unknown whether the change is due to diaphragm activity or whole body exercise. To test the hypothesis that exercise-induced MEP depression was related to diaphragm activity, we performed two experiments. The first examined the effect of whole body exercise, performed with and without the use of non-invasive ventilation (NIV). NIV resulted in significant unloading of the diaphragm (pressure time product 101+/-68 cm H(2)O/s/min versus 278+/-95 cm H(2)O/s/min, p<0.001). Both conditions produced significant MEP depression compared to the control condition (% drop at 5 min, after exercise and exercise with NIV: 29 and 34%, p=0.77). Study 2 compared exercise with isocapnic hyperventilation. At 20 min the MEP had fallen by 29% in the exercise session versus 5% with hyperventilation (p=0.098). We conclude that the work of breathing during whole body exercise is not the primary driver of exercise-induced diaphragm MEP depression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Air Pressure
  • Carbon Dioxide / pharmacology
  • Data Interpretation, Statistical
  • Diaphragm / physiology*
  • Electric Stimulation
  • Electromyography
  • Evoked Potentials, Motor / physiology*
  • Exercise / physiology*
  • Exercise Test
  • Female
  • Femoral Nerve / physiology
  • Humans
  • Hyperventilation / physiopathology
  • Male
  • Oxygen Consumption / physiology
  • Phrenic Nerve / physiology
  • Respiration, Artificial*
  • Supine Position
  • Transcranial Magnetic Stimulation


  • Carbon Dioxide