title: Runners maintain locomotor-respiratory coupling following isocapnic voluntary hyperpnea to task failure.
abstract: BACKGROUND
  Evidence has long suggested that mammalian ventilatory and locomotor rhythms are linked, yet determinants and implications of locomotor-respiratory coupling (LRC) continue to be investigated. Anecdotally, respiratory muscle fatigue seen at the end of heavy exercise may result in an uncoupling of movement-ventilation rhythms; however, there is no scientific evidence to substantiate this claim.
  
  
  OBJECTIVE
  We sought to determine whether or not fatigue of the respiratory muscles alters locomotor-respiratory coupling patterns typically observed in highly trained individuals while running. A related query was to examine the relationship between the potential changes in LRC and measures of running economy.
  
  
  METHODS
  Twelve male distance runners ran at four submaximal workloads (68-89 % VO2peak) on two separate days while LRC was quantified. One LRC trial served as a control (CON), while the other was performed following an isocapnic voluntary hyperpnea to task failure to induce respiratory muscle fatigue (FT+). LRC was assessed as stride-to-breathing frequency ratios (SF/fB) and degree of LRC (percentage of breaths occurring during the same decile of the step cycle).
  
  
  RESULTS
  Hyperpnea resulted in significant declines in maximal voluntary inspiratory (MIP) and expiratory (MEP) mouth pressures (ΔMIP = -10 ± 12 cm H2O; ΔMEP = -6 ± 9 cm H2O). There were no differences in minute ventilation between CON and FT+ (CON, all speeds pooled = 104 ± 25 L min(-1); FT+ pooled = 106 ± 23 L min(-1)). Stride frequency was not different between trials; however, breathing frequency was significantly greater during FT+ compared to CON at all speeds (CON pooled = 47 ± 10 br min(-1); FT+ pooled = 52 ± 9 br min(-1)), resulting in smaller corresponding SF/fB. Yet, the degree of LRC was the same during CON and FT+ (CON pooled = 63 ± 15 %; FT+ pooled = 64 ± 18 %).
  
  
  CONCLUSIONS
  The results indicate that trained runners are able to continue entraining breath and step cycles, despite marked changes in exercise breathing frequency, after a fatiguing hyperpnea challenge.
authors.affiliation: Human Performance Laboratories, Department of Kinesiology, Indiana University, Bloomington, IN, USA. stickfordas@appstate.edu.
authors.forename: Abigail S L
authors.initials: AS
authors.lastname: Stickford
authors.affiliation: Human Performance Laboratories, Department of Kinesiology, Indiana University, Bloomington, IN, USA.
authors.forename: Jonathon L
authors.initials: JL
authors.lastname: Stickford
authors.affiliation: Human Performance Laboratories, Department of Kinesiology, Indiana University, Bloomington, IN, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Tanner
authors.affiliation: Human Performance Laboratories, Department of Kinesiology, Indiana University, Bloomington, IN, USA.
authors.forename: Joel M
authors.initials: JM
authors.lastname: Stager
authors.affiliation: Human Performance Laboratories, Department of Kinesiology, Indiana University, Bloomington, IN, USA.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Chapman
mesh_terms: D005684:Gait / Q000502:physiology*; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D012119:Respiration; D012132:Respiratory Muscles / Q000502:physiology*; D056152:Respiratory Rate / Q000502:physiology*; D012420:Running / Q000502:physiology*
keywords: Endurance athletes; Entrainment; Respiratory muscle fatigue; Running economy; Stride frequency