title: Changes in running mechanics and spring-mass behaviour during a 5-km time trial.
abstract: Research into the biomechanical manifestation of fatigue during exhaustive runs is increasingly popular but additional understanding of the adaptation of the spring-mass behaviour during the course of strenuous, self-paced exercises continues to be a challenge in order to develop optimized training and injury prevention programs. This study investigated continuous changes in running mechanics and spring-mass behaviour during a 5-km run. 12 competitive triathletes performed a 5-km running time trial (mean performance: ̴17 min 30 s) on a 200 m indoor track. Vertical and anterior-posterior ground reaction forces were measured every 200 m by a 5-m long force platform system, and used to determine spring-mass model characteristics. After a fast start, running velocity progressively decreased (- 11.6%; P<0.001) in the middle part of the race before an end spurt in the final 400-600 m. Stride length (- 7.4%; P<0.001) and frequency (- 4.1%; P=0.001) decreased over the 25 laps, while contact time (+ 8.9%; P<0.001) and total stride duration (+ 4.1%; P<0.001) progressively lengthened. Peak vertical forces (- 2.0%; P<0.01) and leg compression (- 4.3%; P<0.05), but not centre of mass vertical displacement (+ 3.2%; P>0.05), decreased with time. As a result, vertical stiffness decreased (- 6.0%; P<0.001) during the run, whereas leg stiffness changes were not significant (+ 1.3%; P>0.05). Spring-mass behaviour progressively changes during a 5-km time trial towards deteriorated vertical stiffness, which alters impact and force production characteristics.
authors.affiliation: Research and Education Centre, ASPETAR - Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. oliv.girard@gmail.com
authors.forename: O
authors.initials: O
authors.lastname: Girard
authors.forename: G P
authors.initials: GP
authors.lastname: Millet
authors.forename: J
authors.initials: J
authors.lastname: Slawinski
authors.forename: S
authors.initials: S
authors.lastname: Racinais
authors.forename: J P
authors.initials: JP
authors.lastname: Micallef
mesh_terms: D000293:Adolescent; D056352:Athletes; D054874:Athletic Performance / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult