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In vivo operating lengths of the gastrocnemius muscle during gait in children who idiopathically toe‐walk
Author(s) -
HarknessArmstrong Carla,
Maganaris Constantinos,
Walton Roger,
Wright David M.,
Bass Alfie,
Baltzopoulos Vasilios,
O'Brien Thomas D.
Publication year - 2021
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/ep089658
Subject(s) - fascicle , isometric exercise , gait , ankle , gastrocnemius muscle , moment (physics) , ultrasound , anatomy , physical medicine and rehabilitation , medicine , physical therapy , skeletal muscle , physics , radiology , classical mechanics
New FindingsWhat 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? 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 moment–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 = 12 mm; 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 . 37 mm; P = 0.001) in children who ITW than TD children. Observed alterations in the moment–angle and moment–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 idiopathic toe‐walking is truly an ankle joint pathology, and children who ITW present with substantial alterations in the gastrocnemius muscle functional properties, which appear well adapted to the characteristic demands of equinus gait. These findings should be considered when prescribing clinical treatments to restore typical gait.