Kay, A. D. and Blazevich, A. J. (2009) Isometric contractions reduce plantar flexor moment, Achilles tendon stiffness, and neuromuscular activity but remove the subsequent effects of stretch. Journal of Applied Physiology. 107, pp. 1181-1189. 8750-7587.
| Item Type: | Article |
|---|---|
| Abstract: | The effects of isometric contractions and passive stretching on muscle-tendon mechanics and muscle activity were studied in 16 healthy human volunteers. First, peak concentric and passive ankle joint moment data were recorded on an isokinetic dynamometer with electromyographic monitoring of the triceps surae; real-time motion analysis of the lower leg and ultrasound imaging of the Achilles-medial gastrocnemius muscletendon junction were simultaneously conducted. Second, the subjects performed six 8-s maximal voluntary isometric contractions (MVICs) before repeating the passive and active trials. Although there was no decrease in isometric joint moment after MVICs, peak concentric moment was significantly reduced (11.5%, P _ 0.01). This was accompanied by, and correlated with (r _ 0.90, P _ 0.01), significant reductions in peak triceps surae electromyographic amplitude (21.0%, P _ 0.01). Achilles tendon stiffness (10.9%, P _ 0.01) and passive joint moment (4.9%, P _ 0.01) were also significantly reduced. Third, the subjects performed three 60-s static plantar flexor stretches before being retested 2 and 30 min after stretch. The stretch protocol caused no significant change in any measure. At 30 min after stretching, significant recovery in concentric moment and muscle activity was detected at dorsiflexed joint angles, while Achilles tendon stiffness and passive joint moment remained significantly reduced. These data show that the performance of MVICs interrupts the normal stretchinduced losses in active and passive plantar flexor joint moment and neuromuscular activity, largely because concentric strength and tendon properties were already affected. Importantly, the decrease in Achilles tendon stiffness remained 30 min later, which may be an important etiological factor for muscle-tendon strain injury risk |
| Uncontrolled Keywords: | triceps surae; force deficits; tissue mechanics; electromyography |
| Subjects: |
Q Science > QP Physiology > QP301 Exercise and sports physiology R Medicine > RC Internal medicine > RC1200 Sports Medicine |
| 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: | 30 July 2009 |
| Date Type: | Publication |
| Page Range: | pp. 1181-1189 |
| Journal or Publication Title: | Journal of Applied Physiology |
| Volume: | 107 |
| Language: | English |
| ISSN: | 8750-7587 |
| Status: | Published / Disseminated |
| Refereed: | Yes |
| URI: | http://nectar.northampton.ac.uk/id/eprint/2115 |
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