Changes in brain functional connectivity and muscle strength independent of elbow flexor atrophy following upper limb immobilization in young females

• Published in: Experimental physiology 2024-09, Vol.109 (9), p.1557-1571
• Main Authors: Seo, Freddie, Clouette, Julien, Huang, Yijia, Potvin‐Desrochers, Alexandra, Lajeunesse, Henri, Parent‐L'Ecuyer, Frédérike, Traversa, Claire, Paquette, Caroline, Churchward‐Venne, Tyler A.
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Arm; Atrophy; Brain; Brain - diagnostic imaging; Brain - physiopathology; brain plasticity; Elbow; Elbow - physiopathology; Excitability; Female; Females; functional magnetic resonance imaging; Humans; Immobilization; Immobilization - adverse effects; Isometric Contraction - physiology; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Motor skill learning; Muscle contraction; muscle disuse; Muscle strength; Muscle Strength - physiology; Muscle, Skeletal - physiopathology; Muscular Atrophy - physiopathology; Nervous system; Neural networks; Neuroimaging; Neuromuscular system; Skeletal muscle; Upper Extremity - physiopathology; Young Adult
• ISSN: 0958-0670; 1469-445X; 1469-445X
• DOI: 10.1113/EP091782

Muscle disuse induces a decline in muscle strength that exceeds the rate and magnitude of muscle atrophy, suggesting that factors beyond the muscle contribute to strength loss. The purpose of this study was to characterize changes in the brain and neuromuscular system in addition to muscle size following upper limb immobilization in young females. Using a within‐participant, unilateral design, 12 females (age: 20.6 ± 2.1 years) underwent 14 days of upper arm immobilization using an elbow brace and sling. Bilateral measures of muscle strength (isometric and isokinetic dynamometry), muscle size (magnetic resonance imaging), voluntary muscle activation capacity, corticospinal excitability, cortical thickness and resting‐state functional connectivity were collected before and after immobilization. Immobilization induced a significant decline in isometric elbow flexion (−21.3 ± 19.2%, interaction: P = 0.0440) and extension (−19.9 ± 15.7%, interaction: P = 0.0317) strength in the immobilized arm only. There was no significant effect of immobilization on elbow flexor cross‐sectional area (CSA) (−1.2 ± 2.4%, interaction: P = 0.466), whereas elbow extensor CSA decreased (−2.9 ± 2.9%, interaction: P = 0.0177) in the immobilized arm. Immobilization did not differentially alter voluntary activation capacity, corticospinal excitability, or cortical thickness (P > 0.05); however, there were significant changes in the functional connectivity of brain regions related to movement planning and error detection (P