Document Detail

Fast unilateral isometric knee extension torque development and bilateral jump height.
MedLine Citation:
PMID:  17019308     Owner:  NLM     Status:  MEDLINE    
PURPOSE: We hypothesized that the initial rate (first 40 ms) of unilateral knee extensor torque development during a maximally fast isometric contraction would depend on the subjects' ability for fast neural activation and that it would predict bilateral jumping performance. METHODS: Nine males (21.8 +/- 0.9 yr, means +/- SD) performed unilateral fast isometric knee extensions (120 degrees knee angle) without countermovement on a dynamometer and bilateral squat jumps (SJ) and countermovement jumps (CMJ) starting from 90 and 120 degrees knee angles (full extension = 180 degrees ). The dynamometer contractions started either from full relaxation or from an isometric pre-tension (15% maximal isometric torque, Tmax). Torque time integral for the first 40 ms after torque onset (TTI-40, normalized to Tmax) and averaged normalized rectified knee extensor EMG for 40 ms before fast torque onset (EMG-40) were used to quantify initial torque rise and voluntary muscle activation. RESULTS: TTI-40 without pre-tension (range: 0.02-0.19% Tmax per second) was significantly lower than TTI-40 with pre-tension, and both were significantly (r = 0.81 and 0.80) related to EMG-40. During jumping, similar significant positive relations were found between jump height and knee extensor EMG during the first 100 ms of the rise in ground reaction force. There also were significant positive linear relations between dynamometer TTI-40 and jump height (r = 0.75 (SJ 90), 0.84 (SJ 120), 0.76 (CMJ 90), and 0.86 (CMJ 120)) but not between dynamometer Tmax and jump height (-0.16 < r < 0.02). CONCLUSION: One-legged TTI-40 to a large extent explained the variation in jump height. The ability to produce a high efferent neural drive before muscle contraction seemed to dominate performance in both the simple single-joint isometric task and the complex multijoint dynamic task.
Cornelis J de Ruiter; Daniel Van Leeuwen; Arjan Heijblom; Maarten F Bobbert; Arnold de Haan
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  38     ISSN:  0195-9131     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  2006 Oct 
Date Detail:
Created Date:  2006-10-04     Completed Date:  2006-12-08     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1843-52     Citation Subset:  IM; S    
Institute for Fundamental and Clinical Human Movement Sciences, Vrije University, Amsterdam, the Netherlands. C_J_de_Ruiter@FBW.VU.NL
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MeSH Terms
Exercise / physiology*
Isometric Contraction / physiology*
Knee / physiology*
Knee Joint / physiology*
Muscle Fatigue
Muscle, Skeletal / physiology*
Quadriceps Muscle / physiology*

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