title: Force-velocity relationship of leg extensors obtained from loaded and unloaded vertical jumps.
abstract: OBJECTIVE
  Resent research has suggested that loaded multi-joint movements could reveal a linear force-velocity (F-V) relationship. The aim of the present study was to evaluate the F-V relationship both across different types of vertical jumps and across different F and V variables.
  
  
  METHODS
  Ten healthy subjects performed maximum various vertical jumps that were either loaded or unloaded by constant external forces of up to 30 % of their body weight. Both the maximum and averaged F and V data were recorded.
  
  
  RESULTS
  The observed F-V relationships proved to be strong (median correlation coefficients ranged 0.78-0.93) and quasi-linear. Their F- and V-intercepts and the calculated maximum power (P) were highly reliable (0.85 < ICC < 0.98), while their concurrent validity with respect to their directly measured values was on average moderate-to-large. The obtained F-V relationships also revealed that (1) the assessment of maximum F and P could be somewhat more reliable and valid than the assessment of maximum V, (2) natural countermovement jumps should be employed rather than the jumps performed from a fixed squat position, while (3) both maximum and averaged F and V variables could be used despite revealing markedly different regression parameters.
  
  
  CONCLUSIONS
  The data generally reveal a reliable, valid, strong and quasi-linear F-V relationship across variety of vertical jumps and the recorded F and V variables. Therefore, we conclude that the loaded vertical jumps could be developed into a routine method for testing the force, velocity, and power generating capacity of leg extensors.
authors.affiliation: Faculty of Sports and Physical Education, The Research Center, University of Belgrade, Belgrade, Serbia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Cuk
authors.forename: Milos
authors.initials: M
authors.lastname: Markovic
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Nedeljkovic
authors.forename: Dusan
authors.initials: D
authors.lastname: Ugarkovic
authors.forename: Milos
authors.initials: M
authors.lastname: Kukolj
authors.forename: Slobodan
authors.initials: S
authors.lastname: Jaric
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D009068:Movement; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*