Casting light on mechanical properties of lower and upper extremity muscles in children with spinal muscular atrophy and healthy peers

Objective: This study aimed to compare the mechanical properties of upper and lower extremities between children with spinal muscular atrophy types 1 and 2 and healthy peers. Methods: The study included children with spinal muscular atrophy types 1 and 2 (n = 21) and healthy controls (n = 25) aged between 1 and 4 years. Mechanical properties of the biceps brachii, triceps brachii, rectus femoris, and gastrocnemius muscles were assessed using a digital myotonometer. Results: Muscle stiffness values of the right (d = 1.42) and left (d= 1.15) biceps brachii, right (d = 1.14) and left (d= 0.97) triceps brachii, and left rectus femoris (d = 0.85) were significantly higher in children with spinal muscular atrophy. Elasticity values of the right (d = 1.42) and left (d = 1.53) biceps brachii, right (d = 1.54) and left (d = 1.19) triceps brachii, left rectus femoris (d = 0.93), and right gastrocnemius (d = 0.92) were also significantly higher in children with SMA. No significant differences were observed between the groups in any of the evaluated resting muscle tone measurements (P > .05), except for the right biceps brachii muscle (d = 0.97). Conclusion: Our study revealed that mechanical properties of the upper and lower extremity muscles in children with spinal muscular atrophy types 1 and 2 differ compared to their healthy peers. Clinicians and researchers may be able to better understand the underlying causes of spinal muscular atrophy and develop more effective treatments by having a better understanding of changes in muscle stiffness and flexibility.