title: Effects of load mass carried in a backpack upon respiratory muscle fatigue.
abstract: OBJECTIVE
  The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20 kg, causes respiratory muscle fatigue.
  
  
  METHODS
  Eight males performed four randomised load carriage (LC) trials comprising 60 min walking at 6.5 km h(-1) wearing a backpack of either 0 (LC0), 10 (LC10), 15 (LC15) or 20 kg (LC20). Inspiratory (PImax) and expiratory (PEmax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60 s of each trial.
  
  
  RESULTS
  Group mean PImax and PEmax were unchanged following 60-min load carriage in all conditions (p > .05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p < .05) with changes not different between trials (p > .05).
  
  
  CONCLUSIONS
  These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20 kg in a backpack for up to 60 min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.
authors.affiliation: a School of Sport, Exercise and Health Sciences , Loughborough University , Loughborough , UK.|b Sport, Outdoor and Exercise Science , University of Derby , Derby , UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Faghy
authors.affiliation: c Department of Sport and Exercise Sciences , University of Chichester , Chichester , UK.
authors.forename: Sam
authors.initials: S
authors.lastname: Blacker
authors.affiliation: d English Institute of Sport , Loughborough High Performance Centre , Loughborough , UK.
authors.forename: Peter I
authors.initials: PI
authors.lastname: Brown
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D015331:Cohort Studies; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D011897:Random Allocation; D012132:Respiratory Muscles / Q000502:physiology*; D035441:Thoracic Wall / Q000502:physiology; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
keywords: Respiratory muscle fatigue; chest wall loading; chest wall restriction; exercise performance; load carriage