Effects of contract–relax, static stretching, and isometric contractions on muscle–tendon mechanics

Kay, A. D., Husbands-Beasley, J. and Blazevich, A. J. (2015) Effects of contract–relax, static stretching, and isometric contractions on muscle–tendon mechanics. Medicine & Science in Sports & Exercise. 47(10), pp. 2181-2190. 0195-9131.

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Item Type:	Article
Abstract:	Introduction: Loading characteristics of stretching techniques likely influence the specific mechanisms responsible for acute increases in range of motion (ROM). Therefore, the effects of a version of contract–relax (CR) proprioceptive neuromuscular facilitation stretching, static stretching (SS), and maximal isometric contraction (Iso) interventions were studied in 17 healthy human volunteers. Methods: Passive ankle moment was recorded on an isokinetic dynamometer, with EMG recording from the triceps surae, simultaneous real-time motion analysis, and ultrasound-imaging-recorded gastrocnemius medialis muscle and Achilles tendon elongation. Subjects then performed each intervention randomly on separate days before reassessment. Results: Significant increases in dorsiflexion ROM (2.5°–5.3°; P < 0.01) and reductions in whole muscle–tendon stiffness (10.1%–21.0%; P < 0.01) occurred under all conditions, with significantly greater changes detected following CR stretching (P < 0.05). Significant reductions in tendon stiffness were observed after CR stretching and Iso (17.7%–22.1%; P < 0.01) but not after SS (P > 0.05), whereas significant reductions in muscle stiffness occurred after CR stretching and SS (16.0%–20.5%; P < 0.01) but not after Iso (P > 0.05). Increases in peak passive moment (stretch tolerance) occurred after Iso (6.8%; P < 0.05), CR stretching (10.6%; P = 0.08), and SS (5.2%; P = 0.08); no difference in changes between conditions was found (P > 0.05). Significant correlations (rs = 0.69–0.82; P < 0.01) were observed between changes in peak passive moment and maximal ROM under all conditions. Conclusions: Although similar ROM increases occur after Iso and SS, changes in muscle and tendon stiffness are distinct. Concomitant reductions in muscle and tendon stiffness after CR stretching suggest a broader adaptive response that likely explains its superior efficacy in acutely increasing ROM. Although mechanical changes appear tissue-specific between interventions, similar increases in stretch tolerance after all interventions are strongly correlated with changes in ROM.
Uncontrolled Keywords:	Proprioceptive neuromuscular facilitation, range of motion, stretch tolerance, tendon stiffness, ultrasonography
Creators:	Kay, Anthony D, Husbands-Beasley, Jade and Blazevich, Anthony J
Faculties, Divisions and Institutes:	Faculties > Faculty of Health & Society > Sports, Exercise & Life Sciences Research Centres > Centre for Physical Activity and Life Sciences
Date:	1 October 2015
Date Type:	Publication
Page Range:	pp. 2181-2190
Journal or Publication Title:	Medicine & Science in Sports & Exercise
Volume:	47
Number:	10
Number of Pages:	10
Language:	English
DOI:	https://doi.org/10.1249/MSS.0000000000000632
ISSN:	0195-9131
Status:	Published / Disseminated
Refereed:	Yes
URI:	http://nectar.northampton.ac.uk/id/eprint/10564

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