Stretching of active muscle elicits chronic changes in multiple strain risk factors

Anthony D Kay, D Richmond, Chris Talbot, M A Mina, Anthony W Baross, Anthony J Blazevich

Research output: Contribution to JournalArticle

Abstract

Introduction: The muscle stretch intensity imposed during 'flexibility' training influences the magnitude of joint range of motion (ROM) adaptation. Thus, stretching whilst the muscle is voluntarily activated was hypothesized to provide a greater stimulus than passive stretching. The effect of a 6-week program of stretch imposed on an isometrically-contracting muscle (i.e. qualitatively similar to isokinetic eccentric training) on muscle-tendon mechanics was therefore studied in 13 healthy human volunteers. Methods: Before and after the training program, dorsiflexion ROM, passive joint moment, and maximal isometric plantar flexor moment were recorded on an isokinetic dynamometer. Simultaneous real-time motion analysis and ultrasound imaging recorded gastrocnemius medialis muscle and Achilles tendon elongation. Training was performed twice weekly and consisted of five sets of 12 maximal isokinetic eccentric contractions at 10[degrees][middle dot]s-1. Results: Significant increases (P<0.01) in ROM (92.7% [14.7[degrees]]), peak passive moment (i.e. stretch tolerance; 136.2%), area under the passive moment curve (i.e. energy storage; 302.6%), and maximal isometric plantar flexor moment (51.3%) were observed after training. While no change in the slope of the passive moment curve (muscle-tendon stiffness) was detected (-1.5%; P>0.05), a significant increase in tendon stiffness (31.2%; P<0.01) and decrease in passive muscle stiffness (-14.6%; P<0.05) was observed. Conclusion: The substantial positive adaptation in multiple functional and physiological variables that are cited within the primary aetiology of muscle strain injury, including strength, ROM, muscle stiffness, and maximal energy storage, indicate that the stretching of active muscle might influence injury risk in addition to muscle function. The lack of change in muscle-tendon stiffness simultaneous with significant increases in tendon stiffness and decreases in passive muscle stiffness indicates that tissue-specific effects were elicited.
Original languageEnglish
Pages (from-to)1388-1396
Number of pages9
JournalMedicine & Science in Sports & Exercise
Volume48
Issue number7
Early online date30 Jan 2016
DOIs
Publication statusPublished - 1 Jul 2016

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  • Activities

    • 1 Participating in a conference or workshop

    18th Annual Congress of the European College of Sport Science (ECSS)

    Tony Kay (Participant)

    28 Jun 20131 Jul 2013

    Activity: Participating in or organising a conference or workshopParticipating in a conference or workshopResearch

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