A new version of test called the functional strength measurement developed for children with cerebral palsy is a feasible, reliable, and valid method of measuring functional strength, a study shows.
The study, “Functional strength measurement in cerebral palsy: feasibility, test–retest reliability, and construct validity,” was published in the journal Developmental Neurorehabilitation.
Cerebral palsy refers to a group of developmental disorders that affect movement and posture. Impairments in movement is one of the core characteristics of the disease, and can include spasticity (a condition in which certain muscles are continuously contracted), and reduced coordination and muscle strength.
Research has shown that muscle strength — not spasticity — has the largest impact on motor function in children with cerebral palsy. As such, it is vital to be able to measure muscle strength in these patients.
A hand-held dynamometer is the preferred way to measure isometric muscle strength, which is strength measured during an isometric contraction, or when the muscle is activated but does not change length.
However, in children with cerebral palsy, it is also essential to measure functional strength because it allows physicians to determine the impairment a child faces in doing everyday activities such as sports.
“Functional strength has been shown to be an important predictor of independent walking,” the authors wrote.
The functional strength measurement (FSM) measures functional strength in both the lower and upper extremities in typically developing children between the ages of 4 and 10.
The FSM consists of eight items that match the activities that children in this age group commonly do. Four items are related to the upper limb and four to the lower limb. Additionally, four of these items measure muscle power, and four measure the number of repetitions in 30 seconds.
It is not known whether the FSM is an appropriate measure of functional strength in children with cerebral palsy due to the physical constraints these children face.
To address this, researchers conducted a study to evaluate the feasibility, reliability, and validity of using FSM in 37 children with cerebral palsy at a rehabilitation center in the Netherlands.
They found that the original FSM system needed some adaptations for these patients, and one item was removed from the original protocol. This led to the development of a new standardized protocol called FSM-CP.
Next, researchers evaluated test-retest reliability, which measures test consistency — the reliability of a test measured over time. FSM-CP’s test-retest reliability was considered high for all items.
Finally, the team measured the correlation between FSM-CP scores and hand-held dynamometer scores when evaluating isometric muscle strength, which showed mostly moderate correlations between measures of the two tests.
“The FSM-CP is feasible, reliable, and valid to use in children with CP [cerebral palsy]. The FSM-CP can be considered as a helpful tool in clinical practice of physical examination of children with CP,” the authors wrote.
However, they advise that, in clinical practice, “both isometric and functional strength should be tested because they provide relevant and different information.”