European Journal of Applied Physiology

, Volume 111, Issue 10, pp 2547–2555

Repeated sprinting on natural grass impairs vertical stiffness but does not alter plantar loading in soccer players

  • Olivier Girard
  • Sébastien Racinais
  • Luke Kelly
  • Grégoire P. Millet
  • Franck Brocherie
Original Article

DOI: 10.1007/s00421-011-1884-5

Cite this article as:
Girard, O., Racinais, S., Kelly, L. et al. Eur J Appl Physiol (2011) 111: 2547. doi:10.1007/s00421-011-1884-5

Abstract

This study aimed to determine changes in spring-mass model (SMM) characteristics, plantar pressures, and muscle activity induced by the repetition of sprints in soccer-specific conditions; i.e., on natural grass with soccer shoes. Thirteen soccer players performed 6 × 20 m sprints interspersed with 20 s of passive recovery. Plantar pressure distribution was recorded via an insole pressure recorder device divided into nine areas for analysis. Stride temporal parameters allowed to estimate SMM characteristics. Surface electromyographic activity was monitored for vastus lateralis, rectus femoris, and biceps femoris muscles. Sprint time, contact time, and total stride duration lengthened from the first to the last repetition (+6.7, +12.9, and +9.3%; all P < 0.05), while flight time, swing time, and stride length remained constant. Stride frequency decrease across repetitions approached significance (−6.8%; P = 0.07). No main effect of the sprint number or any significant interaction between sprint number and foot region was found for maximal force, mean force, peak pressure and mean pressure (all P > 0.05). Center of mass vertical displacement increased (P < 0.01) with time, together with unchanged (both P > 0.05) peak vertical force and leg compression. Vertical stiffness decreased (−15.9%; P < 0.05) across trials, whereas leg stiffness changes were not significant (−5.9%; P > 0.05). Changes in root mean square activity of the three tested muscles over sprint repetitions were not significant. Although repeated sprinting on natural grass with players wearing soccer boots impairs their leg-spring behavior (vertical stiffness), there is no substantial concomitant alterations in muscle activation levels or plantar pressure patterns.

Keywords

Repeated sprint abilityFoot loadingSpring-mass model characteristicsElectromyographic activitySoccer

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Olivier Girard
    • 1
  • Sébastien Racinais
    • 1
  • Luke Kelly
    • 1
  • Grégoire P. Millet
    • 2
  • Franck Brocherie
    • 1
    • 3
  1. 1.ASPETAR, Research and Education CentreQatar Orthopaedic and Sports Medicine HospitalDohaQatar
  2. 2.ISSULUniversity of LausanneLausanneSwitzerland
  3. 3.Qatar Football AssociationQatar Olympic CommitteeDohaQatar