Evaluation of musculotendinous stiffness in prepubertal children and adults, taking into account muscle activity

• Published in: Journal of applied physiology (1985) 2003-07, Vol.95 (1), p.64-72
• Main Authors: Lambertz, Daniel, Mora, Isabelle, Grosset, Jean-Francois, Perot, Chantal
• Format: Article
• Language: English
• Subjects: Adult; Adults; Algorithms; Anthropometry; Biological and medical sciences; Child; Children & youth; Elasticity; Electromyography; Ergometry; Female; Fundamental and applied biological sciences. Psychology; Humans; Isometric Contraction - physiology; Leg - anatomy & histology; Male; Muscle Contraction - physiology; Muscle, Skeletal - anatomy & histology; Muscle, Skeletal - growth & development; Muscle, Skeletal - physiology; Muscular system; Puberty - physiology; Striated muscle. Tendons; Tendons; Tendons - anatomy & histology; Tendons - growth & development; Tendons - physiology; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00885.2002

1 Département de Génie Biologique, Centre National de la Recherche Scientifique Unité Mixte de Recherche 6600, Université de Technologie, F-60205 Compiègne cedex; and 2 Laboratoire Activités Physiques et Sportives et Conduites Motrices, EA 3300, Université de Picardie Jules Verne, F-80025 Amiens, France Submitted 25 September 2002 ; accepted in final form 28 February 2003 Musculotendinous (MT) stiffness of the triceps surae (TS) muscle group was quantified in 28 prepubertal children (7–10 yr) by using quick-release movements at different levels of submaximal contractions. Surface electromyograms (EMG) of each part of the TS and of the tibialis anterior were also recorded. A stiffness index, defined as the slope of the angular stiffness-torque relationship (SI MT-Torque ), was used to quantify changes in MT stiffness with age. Results showed a significant decrease in SI MT-Torque with age, ranging from 4.02 ± 0.29 to 2.88 ± 0.31 rad -1 for the youngest to the oldest children. Because an increase in stiffness with age was expected due to the maturation of elastic tissues, overactivation of the TS was suspected to contribute to the higher SI MT-Torque values found in the youngest children. TS EMG-torque analyses confirmed that neuromuscular efficiency was significantly lower for the 7- or 8-yr-old children compared with 10-yr-old children, notably due to a higher degree of tibialis anterior coactivation found in the youngest children. Thus the stiffness index originally defined as the slope of the angular stiffness-EMG relationship increased significantly with age toward adult values. The results underlined the necessity to take into account the capacities of muscle activation to quantify changes in elastic properties of muscles, when those capacities are suspected to be altered. triceps surae; muscle activation; electromyogram 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 ).