Title

Stretch imposed on active muscle elicits positive adaptations in strain risk factors and exercise-induced muscle damage.

Document Type

Journal Article

Publication Title

Scandinavian journal of medicine & science in sports

Medical Subject Headings

Adaptation, Physiological; Adult; Creatine Kinase; Female; Humans; Knee; Male; Muscle Strength Dynamometer; Muscle Stretching Exercises; Muscle, Skeletal; Myalgia; Oxygen Consumption; Range of Motion, Articular; Risk Factors; Tendons; Young Adult

ISSN

1600-0838

Volume

28

Issue

11

First Page

2299

Last Page

2309

PubMed ID

29943872

Publisher

Wiley

Place of Publication

United Kingdom

School

Centre for Exercise and Sports Science Research (CESSR) / School of Exercise and Health Sciences

RAS ID

27268

Comments

Originally published as: Kay, A. D., Rubley, B., Talbot, C., Mina, M., Baross, A. W., & Blazevich, A. J. (2018). Stretch imposed on active muscle elicits positive adaptations in strain risk factors and exercise‐induced muscle damage. Scandinavian Journal of Medicine & Science in Sports. 28(11), 2299-2309. Original article available here.

Abstract

INTRODUCTION: Stretching highly-contracted plantar flexor muscles (isokinetic eccentric contractions) results in beneficial adaptations in muscle strain risk factors; however its effects in other muscle groups, and on architectural characteristics and exercise-induced muscle damage (EIMD), are unknown.

METHODS: The influence of a 6-week knee extensor training program was studied in 26 volunteers (13 control; 13 experimental). Before and after the training program, passive and maximal isometric and eccentric knee extensor moments and range of motion (ROM) were recorded on an isokinetic dynamometer with simultaneous ultrasound imaging of vastus lateralis (VL). On a separate day, EIMD markers (creatine kinase [CK], delayed onset muscle soreness [DOMS]) were measured before and 24 hours after a 20-minute downhill run. The 6-week training program was performed twice-weekly where five sets of 12 stretches (3 seconds per stretch) were imposed on maximally contracted knee extensor muscles.

RESULTS: Significant (P < 0.05) increases in eccentric (29.5%) and isometric (17.4%) moments, ROM (5.2°), stretch tolerance (55.4%), elastic energy storage (73.0%), VL thickness (7.8%), pennation angle (9.0%), and tendon stiffness (8.7%) occurred. No change (P > 0.05) in passive muscle-tendon stiffness (-9.4%) or resting fascicle length (-0.7%) occurred. The downhill run resulted in substantial DOMS and significant increase in CK concentration before the training program (107.6%); however, DOMS was eliminated from the knee extensors and a significantly smaller increase in CK (-70.0%) occurred post-training.

CONCLUSION: Positive adaptations in functional and physiological variables confirm that imposing stretch on maximally contracted muscle provides beneficial adaptations likely to mitigate EIMD and injury risk and enhance functional performance.

DOI

10.1111/sms.13251

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