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Neuromuscular aspects of eccentric knee extensor actions: effects of electrical stimulation, age, gender and training
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
1998 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The overall aim of this thesis was to study the effects of electrical stimulation, age, gender and training on the torque- and EMG-velocity relationships during eccentric knee extensor muscle actions in man. An isokinetic custom-built dynamometer was evaluated and used throughout the thesis.

During maximal voluntary efforts eccentric torque output was similar to isometric and did not change with velocity. Superimposing electrical stimulation onto a maximal effort caused a specific increase in eccentric torque output. Submaximal electrical stimulation alone also produced a relatively higher eccentric than concentric torque. These results indicate the presence of a neural tension-regulating mechanism during maximal voluntary eccentric muscle actions in man.

The hypothesis that such a mechanism would be more pronounced in children than adultswas not corroborated by the results from children, pre- and postpuberty. The adult pattern of interdependence between torque, EMG and muscle action type seemed to be established before puberty in both males and females. Comparisons between genders indicated a higher eccentric to concentric ratio of electromechanical eficiency at high velocity in postpuberty and adult females.

Training with either pure eccentric or concentric maximal isokinetic muscle actions resulted in mode and velocity specific adaptations, particularly for eccentric training, in peak torque, muscle cross-sectional area, electromechanical efficiency and cross education, that is increase in strength of the contralateral leg. On the other hand, no or only minor training effects were seen on mean torque, muscle fibre morphology, eccentric to concentric EMG ratios and antagonist muscle activity.

The expression of net eccentric torque output during maximal voluntary eccentric knee extensor actions have shown several distinct features separating it from concentric and isometric actions. Clarification of the underlying neuromuscular mechanisms remains a challenge for future research.

Place, publisher, year, edition, pages
Department of Neuroscience, Karolinska Institutet , 1998.
National Category
Physiology
Identifiers
URN: urn:nbn:se:gih:diva-401ISBN: 91-628-3200-X (print)OAI: oai:DiVA.org:gih-401DiVA: diva2:766
Public defence
1998-12-04, 00:00
Opponent
Supervisors
Available from: 2008-06-04 Created: 2008-06-04 Last updated: 2011-05-12

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf