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Stretch imposed on active muscle elicits positive adaptations in strain risk factors and exercise‐induced muscle damage
Author(s) -
Kay Anthony David,
Rubley Bethanee,
Talbot Chris,
Mina Minas,
Baross Anthony William,
Blazevich Anthony John
Publication year - 2018
Publication title -
scandinavian journal of medicine and science in sports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.575
H-Index - 115
eISSN - 1600-0838
pISSN - 0905-7188
DOI - 10.1111/sms.13251
Subject(s) - isometric exercise , eccentric , muscle architecture , medicine , muscle stiffness , delayed onset muscle soreness , eccentric training , creatine kinase , strain (injury) , range of motion , tendon , muscle damage , muscle atrophy , physical medicine and rehabilitation , anatomy , physical therapy , atrophy , stiffness , materials science , physics , quantum mechanics , composite material
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.