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In vivo operating lengths of the gastrocnemius muscle during gait in children who idiopathically toe‐walk

Harkness‐Armstrong, C, Maganaris, CN, Walton, R, Wright, DM, Bass, A, Baltzopoulos, V and O'Brien, TD In vivo operating lengths of the gastrocnemius muscle during gait in children who idiopathically toe‐walk. Experimental Physiology. ISSN 0958-0670 (Accepted)

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Harkness-Armstrong et al., 2021 (accepted version) - in vivo operating lengths of the gastrocnemius muscle during gait in children who idiopathically toe-walk.pdf - Accepted Version
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Abstract

New Findings
• What is the central question of this study?
• What are the in vivo operating lengths of the gastrocnemius muscle in children who idiopathically toe-walk?
• What is the main finding and its importance?
• We show, for the first time, that children who idiopathically toe-walk operate at more plantarflexed positions but at longer fascicle lengths than typically developing children during gait. However, these ranges utilised during gait correspond to where children who idiopathically toe-walk are optimally strong. This should be considered when prescribing clinical treatments to restore typical gait.
Abstract
Children who idiopathically toe-walk (ITW) habitually operate at greater plantarflexion angles than typically developing (TD) children, which might result in shorter, sub-optimal, gastrocnemius fascicle lengths. However, currently no experimental evidence exists to substantiate this notion. Five children who ITW and 14 TD children completed a gait analysis, whilst gastrocnemius fascicle behaviour was simultaneously quantified using ultrasound. The moment-angle (hip, knee and ankle) and -length (gastrocnemius) relationships were determined from isometric maximum voluntary contractions (MVC) on an isokinetic dynamometer combined with ultrasound. During gait, children who ITW operated at more plantarflexed angles (Δ = 20°; p = 0.013) and longer muscle fascicle lengths (Δ = 12mm; p = 0.008) than TD children. During MVC, no differences in the peak moment of any joint were found. However, peak plantarflexor moment occurred at significantly more plantarflexed angles (-16 vs. 1°; p = 0.010) and at longer muscle fascicle lengths (44 vs. 37mm; p = 0.001) in children who ITW than TD children. Observed alterations in the moment-angle and -length relationships of children who ITW coincided with the ranges used during gait. Therefore, the gastrocnemius muscle in children who ITW operates close to the peak of the force-length relationship, similarly to TD children. Thus, this study indicates that children who ITW present with substantial alterations in the gastrocnemius muscle functional properties, which appear well adapted to the characteristic demands of equinus gait. The absence of proximal joint weakness also supports the notion that idiopathic toe-walking is truly an ankle joint pathology. These findings should be considered when prescribing clinical treatments to restore typical gait.

Item Type: Article
Uncontrolled Keywords: 0606 Physiology, 1106 Human Movement and Sports Sciences, 1116 Medical Physiology
Subjects: Q Science > QP Physiology
R Medicine > RJ Pediatrics
R Medicine > RJ Pediatrics > RJ101 Child Health. Child health services
Divisions: Sport & Exercise Sciences
Publisher: Wiley
Date Deposited: 28 Jun 2021 11:21
Last Modified: 28 Jun 2021 11:30
DOI or Identification number: 10.1113/ep089658
URI: https://researchonline.ljmu.ac.uk/id/eprint/15182

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