Changes in stretch reflexes and muscle stiffness with age in prepubescent children

• Published in: Journal of applied physiology (1985) 2007-06, Vol.102 (6), p.2352-2360
• Main Authors: Grosset, Jean-Francois, Mora, Isabelle, Lambertz, Daniel, Perot, Chantal
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - physiology; Age; Aging - physiology; Biological and medical sciences; Biomechanics; Child; Children & youth; Correlation analysis; Elasticity; Engineering Sciences; Female; Fundamental and applied biological sciences. Psychology; Humans; Male; Mechanics; Muscle Contraction - physiology; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Muscular system; Puberty; Reflex, Stretch - physiology; Reflexes; Stress, Mechanical
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.01045.2006

1 Département de Génie Biologique, Université de Technologie, Compiègne cedex; and 2 EA 3300, Laboratoire Activités Physiques et Sportives et Conduites Motrices, Université de Picardie Jules Verne, Amiens, France Submitted 12 September 2006 ; accepted in final form 6 March 2007 Musculo-articular stiffness of the triceps surae (TS) increases with age in prepubescent children, under both passive and active conditions. This study investigates whether these changes in muscle stiffness influence the amplitude of the reflex response to muscle stretch. TS stiffness and reflex activities were measured in 46 children (7–11 yr old) and in 9 adults. The TS Hoffmann reflex (H reflex) and T reflex (tendon jerk) in response to taping the Achilles tendon were evaluated at rest and normalized to the maximal motor response (M max ). Sinusoidal perturbations of passive or activated muscles were used to evoke stretch reflexes and to measure passive and active musculoarticular stiffness. The children's H max -to-M max ratio did not change with age and did not differ from adult values. The T-to-M max ratio increased with age but remained significantly lower than in adults. Passive stiffness also increased with age and was correlated with the T-to-M max ratio. Similarly, the children's stretch reflex and active musculoarticular stiffness were significantly correlated and increased with age. We conclude that prepubescent children have smaller T reflexes and stretch reflexes than adults, and the lower musculoarticular stiffness is mainly responsible for these smaller reflexes, as indicated by the parallel increases in reflex and stiffness. prepubescent children; Hoffmann reflex; T reflex; stretch reflex; musculoarticular stiffness Address for reprint requests and other correspondence: C. Pérot, Université de Technologie de Compiègne, Département Génie Biologique CNRS UMR-6600, F-60205 Compiègne cedex, France (e-mail: chantal.perot{at}utc.fr )