title: Ground contact time as an indicator of metabolic cost in elite distance runners.
abstract: Differences in running economy at common speeds have been demonstrated between male and female distance runners, as well as between middle-distance (MD) and long-distance (LD) specialists. Whether measures of foot ground contact time (tc), known to be proportional to the mass-specific cost of locomotion, follows the same running economy relationships in these groups is unknown.
  
  
  OBJECTIVE
  This study examined if differences in tc and selected gait kinematic variables exist between elite male and female distance runners, as well as between elite MD and LD specialists, as running speed increases.
  
  
  METHODS
  Twelve male and six female elite distance runners completed multiple 30-s trials on a treadmill at common competitive racing velocities. Wireless triaxial 10-g accelerometers, sampling at 1024 Hz, were securely attached to the laces of each shoe. Values of tc, swing time, stride length, and stride frequency were determined from accelerometric output corresponding to foot strike and toe-off events obtained from a minimum of 20 consecutive steps of each foot. A proportional estimate of metabolic cost was obtained by using 1/tc.
  
  
  RESULTS
  Women displayed shorter tc, swing time, and stride length with greater stride frequency compared with men at common speeds; however, these differences were largely negated by normalizing to standing height. At common speeds, women demonstrated smaller measures of tc compared with men, suggesting an increased metabolic cost, paralleling published oxygen uptake data. MD specialists displayed smaller increases in 1/tc as speed increased, compared with LD specialists.
  
  
  CONCLUSIONS
  Elite distance runners demonstrate ground contact measures that suggest that known differences in running economy between sexes and event specialties may be a result of differences in running gait.
authors.affiliation: Harold H. Morris Human Performance Laboratory, Department of Kinesiology, Indiana University, Bloomington, IN 47405, USA. rfchapma@indiana.edu
authors.forename: Robert F
authors.initials: RF
authors.lastname: Chapman
authors.forename: Abigail S
authors.initials: AS
authors.lastname: Laymon
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Wilhite
authors.forename: James M
authors.initials: JM
authors.lastname: McKenzie
authors.forename: David A
authors.initials: DA
authors.lastname: Tanner
authors.forename: Joel M
authors.initials: JM
authors.lastname: Stager
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005080:Exercise Test; D005260:Female; D005528:Foot / Q000502:physiology*; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*; D012737:Sex Factors; D013997:Time Factors