Research article summary (published 30 Jan 2007):

Leg stiffness modulation during exhaustive stretch-shortening cycle exercise.

Full Abstract

The present study examined the effects of muscle activity modulation on leg stiffness during an exhaustive stretch-shortening cycle (SSC) exercise in eight male subjects. Reaction force, electromyography (EMG) of the soleus (Sol), gastrocnemius (Ga) and vastus lateralis (VL) muscles and sledge seat position were recorded during the SSC exercise, consisting of 100 maximal intermittent drop jumps followed by a continuous submaximal jumping until exhaustion, on a sledge apparatus. Metabolic loading was determined by measuring blood lactate (La). No change was found in leg stiffness during the maximal jumps, whereas the subsequent submaximal jumping induced a significant reduction by 27+/-12% (P<0.05). Leg stiffness was closely related to the EMG ratio between the braking and push-off phases in Sol (r=0.81, P<0.05) and particularly in Ga (r=0.98, P<0.001) (but not in VL, r=0.64, NS) at the end of the submaximal jumping. Furthermore, the post-exercise La was significantly associated with the EMG ratio at the end of the submaximal jumping in Sol (r=-0.88, P<0.01) and Ga (r=-0.98, P<0.001). These results indicate that activity modulation between the braking and push-off phases in the triceps surae muscle, particularly in Ga, plays an important role in leg stiffness adjustments during fatiguing SSC exercise. It is suggested that efficient activity modulation (i.e. high EMG ratio) of the triceps surae muscle during an intensive fatiguing SSC exercise may postpone the exhaustion and development of metabolic fatigue.

Author information

Author/s: Kuitunen, S (S); Kyröläinen, H (H); Avela, J (J); Komi, P V (PV);

Affiliation: Department of Biology of Physical Activity, Neuromuscular Research Center, University of Jyväskylä, Jyväskylä, Finland. sami.kuitunen(-atsign-)sport.jyu.fi

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Scandinavian journal of medicine & science in sports (Scand J Med Sci Sports), published in Denmark. (Language: eng)

Reference: 2007-Feb; vol 17 (issue 1) : pp 67-75

Dates: Created 2007/02/19; Completed 2007/04/03; Revised 2008/11/21;

PMID: 17305941, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adaptation, Physiological - physiology Adult Electromyography Exercise - physiology Humans Lactates - blood Leg - physiology Male

Movement - physiology Muscle Contraction - physiology Muscle Fatigue - physiology Muscle, Skeletal - physiology Physical Endurance - physiology Physical Exertion - physiology Statistics, Nonparametric Stress, Mechanical

Associated Chemicals: Lactates (0)

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