Mouth pressure twitches induced by cervical magnetic stimulation to assess inspiratory muscle fatigue.
This study aimed at determining whether twitch mouth pressure (TwPmo) induced by cervical magnetic stimulation (CMS) was sensitive to inspiratory muscle fatigue produced by whole body exercise (WBE) in normal subjects. Twenty subjects performed one or two of the following protocols: (i). cycling at 85% V(O(2),max) until exhaustion; (ii). inspiratory resistive load (IRL) breathing at 62% of maximal inspiratory pressure until task failure. In eight subjects, oesophageal (TwPoes), gastric (TwPga) and transdiaphragmatic (TwPdi) pressures were recorded. The TwPmo was significantly reduced (P<0.05) 20 min after both WBE and IRL, from 17.5+/-4.4 to 15.9+/-3.9 cmH(2)O and from 19.4+/-4.9 to 17.7+/-4.5 cmH(2)O, respectively. Subsequently to IRL, the TwPdi decrease was associated with a reduction in TwPoes/TwPga ratio; not after WBE. Independently of the mode of ventilatory loading, inspiratory muscle fatigue was detected. Thus, inspiratory muscle fatigue after WBE can be assessed in normal subjects with a noninvasive technique.
Delpech
N
N
Laboratoire d'Analyse de la Performance Motrice Humaine, UPRES EA 2253, Faculté des Sciences du Sport, Université de Poitiers, 4 allée Jean Monnet, 86000 Poitiers, France. nathalie.delpech@mshs.univ-poitiers.fr
Jonville
S
S
Denjean
A
A
D000328:Adult; D055590:Electromagnetic Phenomena; D004576:Electromyography; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D009055:Mouth; D018763:Muscle Fatigue / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology; D011312:Pressure; D012132:Respiratory Muscles / Q000502:physiology*