title: Effects of plyometric and weight training on muscle-tendon complex and jump performance.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effects of plyometric and weight training protocols on the mechanical properties of muscle-tendon complex and muscle activities and performances during jumping.
  
  
  METHODS
  Ten subjects completed 12 wk (4 d.wk(-1)) of a unilateral training program for plantar flexors. They performed plyometric training on one side (PT; hopping and drop jump using 40% of 1RM) and weight training on the other side (WT; 80% of 1RM). Tendon stiffness was measured using ultrasonography during isometric plantar flexion. Three kinds of unilateral jump heights using only ankle joint (squat jump: SJ; countermovement jump: CMJ; drop jump: DJ) on sledge apparatus were measured. During jumping, electromyographic activities were recorded from plantar flexors and tibial anterior muscle. Joint stiffness was calculated as the change in joint torque divided by the change in ankle angle during eccentric phase of DJ.
  
  
  RESULTS
  Tendon stiffness increased significantly for WT, but not for PT. Conversely, joint stiffness increased significantly for PT, but not for WT. Whereas PT increased significantly jump heights of SJ, CMJ, and DJ, WT increased SJ only. The relative increases in jump heights were significantly greater for PT than for WT. However, there were no significant differences between PT and WT in the changes in the electromyographic activities of measured muscles during jumping.
  
  
  CONCLUSIONS
  These results indicate that the jump performance gains after plyometric training are attributed to changes in the mechanical properties of muscle-tendon complex, rather than to the muscle activation strategies.
authors.affiliation: Department of Life Science, University of Tokyo, Meguro, Tokyo, Japan. kubo@idaten.c.u-tokyo.ac.jp
authors.forename: Keitaro
authors.initials: K
authors.lastname: Kubo
authors.forename: Masanori
authors.initials: M
authors.lastname: Morimoto
authors.forename: Teruaki
authors.initials: T
authors.lastname: Komuro
authors.forename: Hideaki
authors.initials: H
authors.lastname: Yata
authors.forename: Naoya
authors.initials: N
authors.lastname: Tsunoda
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kanehisa
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Fukunaga
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging / Q000293:injuries* / Q000502:physiology; D000328:Adult; D004576:Electromyography; D005528:Foot; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007564:Japan; D008297:Male; D009068:Movement / Q000502:physiology*; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000293:injuries* / Q000502:physiology; D013647:Task Performance and Analysis; D014463:Ultrasonography; D014891:Weight Lifting / Q000502:physiology*