title: Diaphragm Recruitment Increases during a Bout of Targeted Inspiratory Muscle Training.
abstract: The extent to which the diaphragm is targeted during a bout of inspiratory muscle training (IMT) is unknown. The purpose of this study was to characterize the relative activation patterns of the diaphragm and extradiaphragmatic inspiratory muscles during a bout of IMT and to determine whether diaphragmatic recruitment can be increased by giving subjects specific diaphragmatic breathing instructions (IMTdi).
  
  
  
  Ten healthy men were instrumented with surface EMG electrodes on the sternocleidomastoid (EMGscm), scalenes (EMGsca), parasternal intercostals (EMGpic), and seventh intercostal space (EMG7ic). A multipair esophageal electrode catheter measured crural diaphragmatic EMG (EMGdi) and transdiaphragmatic pressure (Pdi). Trial 1 of IMT involved 25 dynamic inspiratory maneuvers at 40% of maximal inspiratory mouth pressure using a variable flow resistive loading device where subjects were free to choose their own inspiratory muscle recruitment strategy. Trial 2 involved the same procedures, but subjects were given specific instructions to actively recruit their diaphragm. Cervical magnetic stimulation of the phrenic nerves verified the absence of diaphragmatic fatigue before commencing the second trial.
  
  
  
  Compared with IMT, IMTdi resulted in a significant increase in EMGdi (56 ± 12 vs 73 ± 10%max, P = 0.002) and Pdi swings (39 ± 14 vs 64 ± 17 cm H2O, P < 0.0001) and a decrease in EMGsca (52 ± 21 vs 36 ± 22%max, P = 0.04). There was no difference in EMG7ic (26 ± 19 vs 33 ± 21%max, P = 0.36), EMGpic (31 ± 24 vs 25 ± 15%max, P = 0.22), and EMGscm (58 ± 21 vs 45 ± 24%max, P = 0.08) when comparing IMT versus IMTdi, respectively.
  
  
  
  Simple diaphragmatic breathing instructions can significantly increase the recruitment of the diaphragm during IMT compared with a bout of IMT where individuals are free to choose their own inspiratory muscle recruitment strategy.
authors.affiliation: 1Centre for Heart Lung Innovation, Providence Health Care Research Institute, University of British Columbia, St. Paul's Hospital, Vancouver, BC, CANADA; 2Department of Physical Therapy, University of British Columbia, Vancouver, BC, CANADA; 3School of Kinesiology, University of British Columbia, Vancouver, BC, CANADA; and 4Division of Respiratory Medicine, Department of Medicine, University of British Columbia, Vancouver, BC, CANADA.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Ramsook
authors.forename: Ryan
authors.initials: R
authors.lastname: Koo
authors.forename: Yannick
authors.initials: Y
authors.lastname: Molgat-Seon
authors.forename: Paolo B
authors.initials: PB
authors.lastname: Dominelli
authors.forename: Nafeez
authors.initials: N
authors.lastname: Syed
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ryerson
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Sheel
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Guenette
mesh_terms: D000328:Adult; D001945:Breathing Exercises; D003964:Diaphragm / Q000502:physiology*; D004576:Electromyography; D006801:Humans; D008297:Male; D011312:Pressure; D012132:Respiratory Muscles / Q000502:physiology*; D055815:Young Adult