Muscular Performance of the Elbow Flexor and Extensor Muscles in Children With Myopathies: A Case-Control Study.

Abstract

Background and purpose: Children with myopathies often experience muscle weakness in their lower limbs. However, the upper limbs are also affected and, at the same time, play a key role in daily living activities as well as in transfers and assisted mobility using auxiliary devices. The objective was to assess the performance of the elbow flexor and extensor muscles through static and dynamic contractions in children with myopathies and in their typical peers.

Methods: This was a case-control study. Seven children with different myopathies participated and were matched with typical children by sex and age (1:2). The muscle performance of elbow flexors (EFL) and elbow extensors (EEX) was assessed using an isokinetic dynamometer using isometric and isokinetic contractions at a speed of 120°s-¹. The analyzed variables were peak torque (PT), total work (W), power (P), time to peak torque (TPT), acceleration time (AT), and deceleration time (DT). The raw variables were compared between groups using linear regression with mixed effects. A significance level of p < 0.05 was adopted.

Results and discussion: Children with myopathies showed significantly lower values of PT, W, and P for both elbow muscle groups (p < 0.05) compared to typically developing children; TPT showed no difference between groups; and AT and DT were higher in children with myopathies than in typical ones (p < 0.05). Children with myopathies exhibited deficits in muscle performance, suggesting that the elbow muscles adopt atypical motor strategies, indicating impaired neuromuscular control. The isokinetic dynamometer is a device that can provide relevant information about muscle performance in this group of diseases.