Voluntary and magnetically evoked muscle contraction protocol in males with Duchenne muscular dystrophy: Safety, feasibility, reliability, and validity. Issue 2 (9th June 2021)

• Record Type: Journal Article
• Authors: Trost, Joyceann P.; Chen, Mo; Stark, Molly M.; Hodges, James S.; Richter, Sara; Lindsay, Angus; Warren, Gordon L.; Lowe, Dawn A.; Kimberley, Teresa J.
• Is Part Of: Muscle & nerve. Volume 64:Issue 2(2021)
• Page Start: 190
• Page End: 198
• Publication Date: 2021-06-09
• Subjects: dystrophin -- magnetic stimulation -- outcome measures -- surface electromyography -- torque; Neuromuscular diseases -- Periodicals; Muscles -- Periodicals; Nerves -- Periodicals; 616.74
• DOI: 10.1002/mus.27323
• Languages: English
• ISSNs: 0148-639X

Abstract

Abstract: Introduction/Aims: Clinical trials addressing treatments for Duchenne muscular dystrophy (DMD) require reliable and valid measurement of muscle contractile function across all disease severity levels. In this work we aimed to evaluate a protocol combining voluntary and evoked contractions to measure strength and excitability of wrist extensor muscles for safety, feasibility, reliability, and discriminant validity between males with DMD and controls. Methods: Wrist extensor muscle strength and excitability were assessed in males with DMD (N = 10; mean ± standard deviation: 15.4 ± 5.9 years of age), using the Brooke Upper Extremity Rating Scale (scored 1‐6), and age‐matched healthy male controls (N = 15; 15.5 ± 5.0 years of age). Torque and electromyographic (EMG) measurements were analyzed under maximum voluntary and stimulated conditions at two visits. Results: A protocol of multiple maximal voluntary contractions (MVCs) and evoked twitch contractions was feasible and safe, with 96% of the participants completing the protocol and having a less than 7% strength decrement on either measure for both DMD patients and controls ( P ≥ .074). Reliability was excellent for voluntary and evoked measurements of torque and EMG (intraclass correlation coefficient [ICC] over 0.90 and over 0.85 within and between visits, respectively). Torque, EMG, and timing of twitch‐onset measurements discriminated between DMD and controls ( P < .001). Twitch contraction time did not differ significantly between groups ( P = .10). Discussion: Findings from this study show that the protocol is a safe, feasible, reliable, and a valid method to measure strength and excitability of wrist extensors in males with DMD.