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Methods for measurement of muscle function. Methodological aspects, reference values for children, and clinical
1Department of Clinical Neurophysiology, Faculty of Health Sciences, Linköping University, Sweden.
Insights
This study establishes reference values for isometric and isokinetic muscle strength in children, highlighting age and sex-related differences and the utility of functional tests for assessing muscle function.
Area of Science:
- Pediatric physical therapy
- Neuromuscular function assessment
- Child development
Background:
- Assessing muscle strength in children is crucial for understanding development and diagnosing conditions.
- Standardized reference values are needed for various muscle groups and age ranges.
- Different testing methods have varying applicability and reliability in pediatric populations.
Purpose of the Study:
- To establish reference values for isometric and isokinetic muscle force in children aged 3.5-15 years.
- To investigate age, sex, and limb dominance differences in muscle strength.
- To evaluate the reliability and utility of different muscle testing methods, including functional tests, in children, particularly those with Duchenne muscular dystrophy.
Main Methods:
- Isometric muscle force measurement using a hand-held dynamometer.
- Isokinetic muscle torque measurement for ankle dorsiflexors.
- Functional tests of motor ability.
- Electrical stimulation of the adductor pollicis muscle.
Main Results:
- Isometric muscle force in children aged 3.5-15 years showed acceptable reproducibility, with predicted values based on age and weight.
- Significant differences in muscle strength were observed between dominant and non-dominant limbs, and between sexes (boys stronger than girls from 9.5-11 years).
- Isokinetic dorsiflexor torque increased with age, with peak development between 12-15 years, and sex differences emerging in puberty. Functional tests were useful for Duchenne muscular dystrophy assessment, while isokinetic testing was unreliable in this cohort.
Conclusions:
- Isometric dynamometry provides reliable muscle strength data in children, with established reference values.
- Age and sex are significant factors influencing muscle strength development in children.
- Functional tests are valuable for assessing muscle function in severely impaired children, complementing other methods.
Abstract:
In children isometric muscle force can be measured with acceptable reproducibility by using a simple hand-held dynamometer. Reference values for 10 different muscle groups are given for children aged 3.5-15 years. If age and weight are known, the force can be predicted. The most pronounced differences between the dominant and the non-dominant side were found in the elbow flexors, 3 of the 6 age groups showing greater force on the dominant side, and in the wrist extensors, the 2 oldest age groups being stronger on the dominant side. Sex differences were present as early as 9.5-11 years of age, boys being stronger than girls. Isokinetic muscle torque of the dorsiflexors of the ankle increased with age. Reference values are given for peak torque in children 6, 9, 12, and 15 years of age. The most intense force development occurs between 12 and 15 years of age in boys, and earlier in girls. Sex differences appear in early puberty. In young children the dominant leg was the stronger at the highest velocities. In the older children the non-dominant leg was the stronger at low velocities. Isokinetic measurements are time-consuming and require experience, and should be regarded as complementary to isometric testing. In muscle groups that are too weak to overcome gravity isometric and isokinetic methods cannot be used. Functional tests of motor ability are especially useful in patients with severely impaired muscle function when other test methods are inadequate or difficult to evaluate. The natural course of Duchenne muscular dystrophy was followed in 16 boys by means of functional tests, isometric tests, isokinetic tests of concentric muscle contraction, and manual tests. Of these only the isokinetic method proved unreliable, possibly because of difficulty in activating the muscles at different speeds. The function of adductor pollicis was studied by supramaximal electrical stimulation of the ulnar nerve. Force-frequency curves and reference values for relaxation rate and half contraction time to tetanus for children aged 9, 12, and 15 years are presented. The half contraction time to tetanus was briefer in the older children than in the younger. The relative force developed at a stimulation of 10 Hz increased with age. Apart for the increase in muscle force with increasing age, no other differences emerged between the different age groups. No sex differences were found. The electrical stimulation test is rather painful, and only about 60% of the children persevered to the end of the test.(ABSTRACT TRUNCATED AT 400 WORDS)