title: Mechanical alterations during interval-training treadmill runs in high-level male team-sport players.
abstract: OBJECTIVE
  To examine mechanical alterations during interval-training treadmill runs in high-level team-sport players.
  
  
  METHODS
  Within-participants repeated measures.
  
  
  METHODS
  Twenty high-level male field-hockey players performed six 30-s runs at 5.53±0.19ms-1corresponding to 115% of their velocity associated with maximal oxygen uptake (vVO2max) with 30-s passive recovery on an instrumented treadmill. Continuous measurement of running kinetics/kinematics and spring-mass characteristics were performed and values were subsequently averaged over 20s (8th-28ths) for comparison.
  
  
  RESULTS
  Contact time (+1.1±4.3%; p=0.044), aerial time (+4.1±5.3%; p=0.001), step length (+2.4±2.2%; p<0.001) along with mean loading rates (+7.1±10.6%; p=0.026) increased from the first to the last interval, whereas step frequency (-2.3±2.1%; p<0.001) decreased. Both centre of mass vertical displacement (+3.0±6.0%; p<0.001) and leg compression (+2.8±9.7%; p=0.036), but not peak vertical forces (0.0±4.1%; p=0.761), increased with fatigue. Vertical stiffness decreased (-2.8±6.9%; p=0.012), whereas leg stiffness did not change across intervals (p=0.149).
  
  
  CONCLUSIONS
  During interval-training treadmill runs, high-level team-sport players modified their mechanical behaviour towards lower vertical stiffness while preserving a constant leg stiffness. Maintenance of running velocity induced longer step lengths and decreased step frequencies that were also accompanied by increased impact loading rates. These mechanical alterations occurred early during the set.
authors.affiliation: ISSUL, Institute of Sport Sciences, Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland; Aspetar - Orthopaedic and Sports Medicine Hospital, Athlete Health and Performance Research Centre, Doha, Qatar. Electronic address: oliv.girard@gmail.com.
authors.forename: Olivier
authors.initials: O
authors.lastname: Girard
authors.affiliation: ISSUL, Institute of Sport Sciences, Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland.
authors.forename: Franck
authors.initials: F
authors.lastname: Brocherie
authors.affiliation: Laboratory of Human Motricity, Education Sport and Health (LAMHESS), University of Nice Sophia Antipolis, Nice, France.
authors.forename: Jean-Benoit
authors.initials: JB
authors.lastname: Morin
authors.affiliation: ISSUL, Institute of Sport Sciences, Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland.
authors.forename: Grégoire P
authors.initials: GP
authors.lastname: Millet
mesh_terms: D000328:Adult; D056352:Athletes; D001696:Biomechanical Phenomena; D005080:Exercise Test / Q000379:methods*; D000072696:High-Intensity Interval Training / Q000379:methods*; D006688:Hockey; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D012420:Running / Q000502:physiology*; D055815:Young Adult
keywords: High-intensity interval training; Injury prevention; Instrumented treadmill; Leg-spring behaviour; Running kinematics; Team sports