Paired changes in electromechanical delay and musculo-tendinous stiffness after endurance or plyometric training

When measured in vivo electromechanical delay (EMD) depends mainly on the elastic properties of the muscle–tendon unit. Recent studies have shown changes in stiffness of the triceps surae (TS) following a period of training. To confirm the influence of musculo-tendinous stiffness on EMD, this study...

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Bibliographic Details
Published in:European journal of applied physiology 2009-01, Vol.105 (1), p.131-139
Main Authors: Grosset, Jean-Francois, Piscione, Julien, Lambertz, Daniel, Pérot, Chantal
Format: Article
Language:English
Subjects:
Biological and medical sciences
Biomechanical Phenomena
Biomechanics
Biomedical and Life Sciences
Biomedicine
Electromyography
Female
Fundamental and applied biological sciences. Psychology
Human Physiology
Humans
Male
Mechanics
Muscle Contraction - physiology
Muscle, Skeletal - physiology
Muscular system
Occupational Medicine/Industrial Medicine
Original Article
Physical Endurance - physiology
Physics
Sports Medicine
Stress, Mechanical
Tendons - physiology
Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports
Young Adult
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Summary:When measured in vivo electromechanical delay (EMD) depends mainly on the elastic properties of the muscle–tendon unit. Recent studies have shown changes in stiffness of the triceps surae (TS) following a period of training. To confirm the influence of musculo-tendinous stiffness on EMD, this study investigates paired changes in these two parameters after a training period. Two types of training known to induce opposite changes in stiffness were analysed. EMD and musculo-tendinous stiffness were measured on adult subjects before and after 10 weeks of endurance ( n  = 21) or plyometric ( n  = 9) trainings. EMD was defined as the time lag between the TS M-wave latency and the onset of muscle twitch evoked at rest by supramaximal electrical stimulations of the posterior tibial nerve. Quick release tests were used to evaluate the musculo-tendinous stiffness of the ankle plantar flexors. The stiffness index was defined as the slope of the relationship between angular stiffness and external torque values. Endurance training, known to preferentially activate the slow, stiffer muscle fibers, leads to a decrease in EMD and to an increase in stiffness index. Following plyometric training, which specifically recruits fast, more compliant fibers, EMD and the stiffness index exhibited adaptations directionally opposite to those seen with endurance training. When pooling the data for the two subject groups, a correlation was found between changes in EMD and changes in musculo-tendinous stiffness indexes. Thus, changes in EMD values are proposed to indirectly link to changes in musculo-tendinous stiffness for subjects involved in muscle training.
ISSN:1439-6319
1439-6327
DOI:10.1007/s00421-008-0882-8