Up to 90% of all children diagnosed with CP have difficulty walking. Thus, one of the major goals of rehabilitation therapy is to improve children’s walking ability.
“[T]here is a need to improve the efficacy of current treadmill training paradigms [to improve] walking function in children with CP. This requires a thorough understanding of the underlying motor learning mechanisms in children with CP during locomotor training,” researchers wrote.
One of the methods that can be used to evaluate motor learning is the analysis of errors and subsequent aftereffects. These errors arise when the brain detects “a discrepancy between the predicted and actual leg movement, due to, for instance, an external perturbation.”
After detecting this discrepancy, the brain tries to”adjust the motor commands to reduce this discrepancy,” usually leading to an aftereffect that can be reflected, for instance, in taking larger steps.
In this study, researchers set out to investigate whether the size and variability of these errors could play a role in motor learning in children with spastic CP.
Eleven children and adolescents ages 7-16 with spastic CP — three quadriplegic (muscle impairment in all limbs) and eight diplegic (leg muscle impairment) — were recruited through the Rehabilitation Institute of Chicago to participate in the study.
All were asked to wear a load cell on the right leg above the ankle while walking on a treadmill. Three different types of force perturbations — abrupt, gradual and noisy — were applied to the load cell in three different testing sessions. Gait parameters were recorded by two custom-designed 3D sensors placed on each leg during treadmill walking.
Initial analysis revealed that children with spastic CP adapted to force perturbations by developing an aftereffect in which the length of their steps increased after load release. Interestingly, investigators also found the aftereffect lasted longer when a gradual load was applied and error size was smaller, and less when an abrupt load was used and error size was larger.
Results also showed that higher error variability — achieved by applying different magnitudes of force perturbations — seems to facilitate motor learning and extend the duration of the aftereffect in children with spastic CP during treadmill training.
“Results from this study suggest that gradual application of a swing phase resistance load may be more effective in inducing long-term retention of increased step length in children with CP. [These findings] may be used to develop a robotic training paradigm [to improve] walking function of children with CP [in the future],” researchers concluded.