Medial gastrocnemius muscle stiffness cannot explain the increased ankle joint range of motion following passive stretching in children with cerebral palsy

Abstract

Stretching is often used to increase or maintain the joint range of motion (ROM) in children with cerebral palsy (CP), but the effectiveness of these interventions is limited. Therefore, our aim was to determine the acute changes in muscle-tendon lengthening properties that contribute to increased ROM after a bout of stretching in children with CP. Eleven children with spastic CP [age 12.1 (3 SD) years, 5/6 hemiplegia/diplegia, 7/4 gross motor function classification system level I/II] participated. Each child received three sets of five × 20 s passive, manual static dorsiflexion stretches separated by 30 s rest, with 60 s rest between sets. Before and immediately after stretching, ultrasound was used to measure medial gastrocnemius fascicle lengthening continuously over the full ROM and an individual common ROM pre- to post-stretching. Simultaneously, three-dimensional motion of two marker clusters on the shank and the foot was captured to calculate ankle angle, and ankle joint torque was calculated from manually applied torques and forces on a six degrees-of-freedom load cell. After stretching, the ROM was increased [by 9.9 (12.0) deg, P = 0.005]. Over a ROM common to both pre- and post-measurements, there were no changes in fascicle lengthening or torque. The maximal ankle joint torque tolerated by the participants increased [by 2.9 (2.4) N m, P = 0.003], and at this highest passive torque the maximal fascicle length was 2.8 (2.4) mm greater (P = 0.009) when compared with before stretching. These results indicate that the stiffness of the muscle fascicles in children with CP remains unaltered by an acute bout of stretching.

Comprehensive evaluation of gait, spasticity, and muscle morphology: A case report of a child with spastic paresis treated with Botulinum NeuroToxin‐A, serial casting, and physiotherapy

“…However, we found no changes in muscle morphology, indicating that changes in passive ankle ROM during gait were not because of morphological changes in the GM. This finding is also supported by recent studies of Pothrat et al and Kalkman et al in which changes in φ FoSo did not correspond to length changes of the triceps surae muscles …”

“…Possibly, treatment resulted in a more flexible foot that could be fitted more easily (pain‐free) into an AFO. This result is similar to that of recent studies showing limited long‐term effects of stretching interventions, with increases in joint ranges being accounted for by increased tolerance . While the child was better able to tolerate her AFO in the short term, it is questionable whether increasing foot flexibility is desirable and therefore whether treatment with serial casting following BoNT‐A was the best long‐term solution.…”

“…This finding is also supported by recent studies of Pothrat et al and Kalkman et al in which changes in φ FoSo did not correspond to length changes of the triceps surae muscles. 29,30 Instead, it is likely that increased foot flexibility contributed to observed changes in gait. Using a simple approach, we showed that flexibility of the foot greatly contributed to apparent ankle ROM, especially at 9 wk post-treatment.…”

“…This result is similar to that of recent studies showing limited long-term effects of stretching interventions, with increases in joint ranges being accounted for by increased tolerance. 30,47 While the child was better able to tolerate her AFO in the short term, it is questionable whether increasing foot flexibility is desirable and therefore whether treatment with serial casting following BoNT-A was the best long-term solution. In our patient's case, stretch reflex hyperactivity, rather than passive muscle properties, was very likely a strong determinant of her gait deviations.…”

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

“…With the exception of the ultrasound measurements, the same experimental set-up was used by Kalkman et al (2018) and between the MTJ and the marker on the calcaneus, respectively. A hand-held force sensor load-cell was used to measure net joint torque at the footplate during passive stretch.…”