Fatigue and muscle-tendon stiffness after stretch-shortening cycle and isometric exercise

Hechmi Toumi, Georges Poumarat, Thomas M. Best, Alain Martin, John Fairclough, Mike Benjamin

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

The purpose of the present study was to compare vertical jump performance after 2 different fatigue protocols. In the first protocol, subjects performed consecutive sets of 10 repetitions of stretch-shortening cycle (SSC) contractions. In the second protocol, successive sets of 10 repetitions of isometric contractions were performed for 10 s with the knee at 90° of flexion. The exercises were stopped when the subjects failed to reach 50% of their maximum voluntary isometric contractions. Maximal isometric force and maximal concentric power were assessed by performing supine leg presses, squat jumps, and drop jumps. Surface EMG was used to determine changes in muscle activation before and after fatigue. In both groups, the fatigue exercises reduced voluntary isometric force, maximal concentric power, and drop jump performance. Kinematic data showed a decrease in knee muscle-tendon stiffness accompanied by a lengthened ground contact time. EMG analysis showed that the squat and drop jumps were performed similarly before and after the fatigue exercise for both groups. Although it was expected that the stiffness would decrease more after SSC than after isometric fatigue (as a result of a greater alteration of the reflex sensitivity SSC), our results showed that both protocols had a similar effect on knee muscle stiffness during jumping exercises. Both fatigue protocols induced muscle fatigue, and the decrease in jump performance was linked to a decrease in the strength and stiffness of the knee extensor muscles.

Original languageEnglish (US)
Pages (from-to)565-572
Number of pages8
JournalApplied Physiology, Nutrition and Metabolism
Volume31
Issue number5
DOIs
StatePublished - Oct 1 2006
Externally publishedYes

Keywords

  • Contractile failure
  • EMG
  • Jump
  • Neural
  • Reflex activity

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Nutrition and Dietetics
  • Physiology (medical)

Fingerprint Dive into the research topics of 'Fatigue and muscle-tendon stiffness after stretch-shortening cycle and isometric exercise'. Together they form a unique fingerprint.

Cite this