Northampton Electronic Collection of Theses and Research

Concentric muscle contractions before static stretching minimize, but do not remove, stretch-induced force deficits

Kay, A. D. and Blazevich, A. J. (2010) Concentric muscle contractions before static stretching minimize, but do not remove, stretch-induced force deficits. Journal of Applied Physiology. 108(3), pp. 637-645. 8750-7587.

Item Type: Article
Abstract: The effects of concentric contractions and passive stretching on musculotendinous stiffness and muscle activity were studied in 18 healthy human volunteers. Passive and concentric plantar flexor joint moment data were recorded on an isokinetic dynamometer with simultaneous ectromyogram (EMG) monitoring of the triceps surae, real-time motion analysis of the lower leg, and ultrasound imaging of the Achilles-medial gastrocnemius muscle-tendon junction. The subjects then performed six 8-s ramped maximal voluntary concentric contractions before repeating both the passive and concentric trials. Concentric moment was significantly reduced (6.6%; P < 0.01), which was accompanied by, and correlated with (r < 0.60–0.94; P < 0.05), significant reductions in peak triceps surae EMG amplitude (10.2%; P < 0.01). Achilles tendon stiffness was significantly reduced (11.7%; P < 0.01), but no change in gastrocnemius medialis muscle operating length was detected. The subjects then performed three 60-s static plantar flexor stretches before being retested 2 and 30 min poststretch. A further reduction in concentric joint moment (5.8%; P < 0.01) was detected poststretch at 90% of range of motion, with no decrease in muscle activity or Achilles tendon stiffness, but a significant increase in muscle operating length and decrease in tendon length was apparent at this range of motion (P < 0.05). Thirty minutes after stretching, muscle activity significantly recovered to pre-maximal voluntary concentric contractions levels, whereas concentric moment and Achilles tendon stiffness remained depressed. These data show that the performance of maximal concentric contractions can substantially reduce neuromuscular activity and muscle force, but this does not prevent a further stretch-induced loss in active plantar flexor joint moment. Importantly, the different temporal changes in EMG and concentric joint moment indicate that a muscle-based mechanism was likely responsible for the force losses poststretch
Uncontrolled Keywords: triceps surae; joint moment; tendon stiffness; electromyography
Subjects: Q Science > QP Physiology > QP301 Exercise and sports physiology
Creators: Kay, Anthony D and Blazevich, Anthony J
Publisher: American Physiological Society
Faculties, Divisions and Institutes: University Faculties, Divisions and Research Centres - OLD > Faculty of Health & Society > Sports, Exercise & Life Sciences
University Faculties, Divisions and Research Centres - OLD > Research Centre > Institute of Health and Wellbeing > Centre for Physical Activity and Chronic Disease
Faculties > Faculty of Health & Society > Sports, Exercise & Life Sciences
Research Centres > Centre for Health Sciences and Services
Research Centres > Centre for Physical Activity and Life Sciences
Date: March 2010
Date Type: Publication
Page Range: pp. 637-645
Journal or Publication Title: Journal of Applied Physiology
Volume: 108
Number: 3
Language: English
DOI: https://doi.org/10.1152/japplphysiol.01135.2009
ISSN: 8750-7587
Status: Published / Disseminated
Refereed: Yes
URI: http://nectar.northampton.ac.uk/id/eprint/2553

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