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Muscle and tendon lengthening behaviour of the medial gastrocnemius during ankle joint rotation in children with cerebral palsy.

Kalkman, BM, Bar-On, L, Cenni, F, Maganaris, CN, Bass, A, Holmes, G, Desloovere, K, Barton, GJ and O'Brien, TD (2018) Muscle and tendon lengthening behaviour of the medial gastrocnemius during ankle joint rotation in children with cerebral palsy. Experimental Physiology. ISSN 1469-445X

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Abstract

NEW FINDINGS: What is the central question of this study? Which structures of the medial gastrocnemius muscle-tendon unit contribute to its lengthening during joint rotation and thus receive the stretching stimulus? What is the main finding and its importance? We show, for the first time, that muscle and tendon lengthen in a different manner in children with cerebral palsy compared with typically developing children during a similar amount of muscle-tendon unit lengthening or joint rotation. This indicates possible differences in mechanical muscle and tendon properties attributable to cerebral palsy, which are not evident by assessment of muscle function at the level of a joint. ABSTRACT: Children with cerebral palsy (CP) commonly present with reduced ankle range of motion (ROM) attributable, in part, to changes in mechanical properties of the muscle-tendon unit (MTU). Detailed information about how muscle and tendon interact to contribute to joint rotation is currently lacking but might provide essential information to explain the limited effectiveness of stretching interventions in children with CP. The purpose of this study was to quantify which structures contribute to MTU lengthening and thus receive the stretch during passive ankle joint rotation. Fifteen children with CP (age, in mean ± SD, 11.4 ± 3 years) and 16 typically developing (TD) children (age, in mean ± SD, 10.2 ± 3 years) participated. Ultrasound was combined with motion tracking, joint torque and EMG to record fascicle, muscle and tendon lengthening of the medial gastrocnemius during passive ankle joint rotations over the full ROM and a common ROM. In children with CP, relative to MTU lengthening, muscle and fascicles lengthened less (CP, 50.4% of MTU lengthening; TD, 63% of MTU lengthening; P < 0.04) and tendon lengthened more (CP, 49.6% of MTU lengthening; TD, 37% of MTU lengthening; P < 0.01) regardless of the ROM studied. Differences between groups in the amount of lengthening of the underlying structures during a similar amount of joint rotation and MTU displacement indicate possible differences in tissue mechanical properties attributable to CP, which are not evident by assessment at the level of a joint. These factors should be considered when assessing and treating muscle function in children with CP, for example during stretching exercises, because the muscle might not receive much of the applied lengthening stimulus.

Item Type: Article
Uncontrolled Keywords: 0606 Physiology, 1116 Medical Physiology, 1106 Human Movement And Sports Science
Subjects: R Medicine > RD Surgery
Divisions: Sport & Exercise Sciences
Publisher: Wiley
Related URLs:
Date Deposited: 02 Oct 2018 10:13
Last Modified: 02 Oct 2018 12:18
DOI or Identification number: 10.1113/EP087053
URI: http://researchonline.ljmu.ac.uk/id/eprint/9394

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