title: Chest wall motion after thixotropy conditioning of inspiratory muscles in healthy humans.
abstract: Inspiratory muscle conditioning at a lower or higher lung volume based on the principles of muscle thixotropy causes acute changes in end-expiratory chest wall and lung volumes. The present study aimed to demonstrate the time course of effects of this conditioning on both end-expiratory chest wall volume and thoracoabdominal synchrony. We measured chest wall motion with respiratory induction plethysmography at 0.5, 1, 2, 3, and 6 min after conditioning at three different lung volumes in 15 healthy men. After conditioning at total lung capacity - 20% inspiratory capacity, increases in end-expiratory chest wall volume were significant at 0.5, 1, and 2 min (P < 0.05), being most obvious at 0.5 min (Delta 0.24 +/- 0.20 liter). After conditioning at residual volume, reductions in end-expiratory chest wall volume were significant at any time point (P < 0.05), being most obvious at 0.5 min (Delta 0.16 +/- 0.08 liter). Conditioning at functional residual capacity had little effect on the volume. Spirometric inspiratory capacity at 6 min after conditioning at residual volume (2.68 +/- 0.35 liter) was higher than the baseline value (2.53 +/- 0.31 liter, P < 0.05). Reductions in the phase angle, quantified by the Konno-Mead diagram, occurred after conditioning at residual volume at any time point (P < 0.05), being most obvious at 2 min (Delta 3.47 +/- 3.02 degrees). In conclusion, there is a 6-min time course of changes in end-expiratory chest wall volume after conditioning. More synchronous motion between the rib cage and abdomen occurs after conditioning at residual volume.
authors.affiliation: Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555 Japan. masahiko@med.showa-u.ac.jp
authors.forename: Masahiko
authors.initials: M
authors.lastname: Izumizaki
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Ohshima
authors.forename: Michiko
authors.initials: M
authors.lastname: Iwase
authors.forename: Ikuo
authors.initials: I
authors.lastname: Homma
mesh_terms: D000328:Adult; D045853:Exhalation / Q000502:physiology; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D009129:Muscle Tonus / Q000502:physiology; D010991:Plethysmography; D012115:Residual Volume; D015656:Respiratory Mechanics; D012132:Respiratory Muscles / Q000502:physiology*; D035441:Thoracic Wall / Q000502:physiology*; D014109:Total Lung Capacity