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A developmental index of muscle strength and assessment of quadriceps function in children with spina bifida
1Institute for Developmental Research, Aichi Prefectural Colony, Kasugai, Japan.
Insights
A new Muscle Strength Index (MSI) was developed for children, independent of body weight. This index effectively assesses quadriceps strength and predicts ambulatory status in children with spina bifida.
Area of Science:
- Pediatrics
- Neurology
- Rehabilitation Medicine
Background:
- Assessing muscle strength in children requires accounting for developmental changes and body weight.
- Spina bifida can impact motor function, including quadriceps strength and ambulatory ability.
- Existing measures of muscle strength may not adequately capture functional status in pediatric populations with neuromuscular conditions.
Purpose of the Study:
- To develop a novel, body weight-independent index of muscle strength for children.
- To evaluate the quadriceps strength in children with spina bifida using this new index.
- To determine the relationship between the new muscle strength index and ambulatory status in children with spina bifida.
Main Methods:
- Measured maximum voluntary isometric knee extension torque in children with spina bifida and typically developing children.
- Developed a Muscle Strength Index (MSI) by normalizing torque residuals from a developmental regression line by body weight and standard deviation.
- Analyzed the correlation between MSI, body weight, neurologic level, and ambulatory ability in the spina bifida cohort.
Main Results:
- The developed Muscle Strength Index (MSI) is a unitless measure independent of body weight.
- Children with spina bifida showed increased torque with body weight, but MSI decreased significantly above 30 kg, indicating muscle weakness.
- MSI demonstrated a closer relationship with neurologic level and ambulatory ability compared to raw torque measurements.
Conclusions:
- The novel Muscle Strength Index (MSI) provides a reliable and sensitive measure of quadriceps strength in children.
- MSI is a valuable tool for assessing and predicting ambulatory status in children with spina bifida.
- This index can aid in monitoring disease progression and evaluating interventions in pediatric neuromuscular disorders.
Abstract:
This study was designed to develop a new index of muscle strength for children that was independent of body weight thus accommodated their developmental changes and to assess the quadriceps strength influencing ambulatory status in children with spina bifida. Maximum voluntary strength in isometric knee extension was measured from 60 children with spina bifida and 92 normal children. The measured strength was described in terms of torque. A muscle strength index (MSI) was defined as a unitless measure independent of the subject's body weight (i) by normalizing the residual of the maximum torque from the developmental regression line for normal children by body weight and, furthermore, (ii) by dividing the normalized residuals by their standard deviation among normal children. Children with spina bifida demonstrated a tendency to increase in maximum quadriceps torque with body weight; however, spina bifida children with a body weight above 30 kg showed a progressive decrease in MSI below a normal limit of muscle weakness. The MSI was closely related to both neurologic level and ambulatory ability compared with the maximum torque. These findings suggest MSI provides useful and detailed information for assessing and predicting ambulatory ability in children with spina bifida.