Neuromuscular Dysfunction and Cortical Impairment in Sleep Apnea Syndrome

Purpose Lower muscle strength and endurance have been reported in severe obstructive sleep apnea (OSA). Increased intracortical inhibition previously reported at rest in OSA suggests central neuromuscular impairments in these patients. We hypothesized that (i) OSA patients demonstrate reduced knee extensor strength and endurance due to central impairments and (ii) continuous positive airway pressure (CPAP) treatment improves neuromuscular function in these patients. Methods Twelve OSA patients and 11 healthy controls performed intermittent knee extensions until task failure before and after 8 weeks of CPAP treatment or control period. Maximal voluntary contraction (MVC), voluntary activation (VA) and corticospinal excitability and inhibition assessed by single- and paired-pulse transcranial magnetic stimulation (TMS) were measured before and during the fatiguing task. Results Time to exhaustion was lower in OSA (before CPAP treatment: 1008 ± 549 s; after CPAP treatment: 975 ± 378 s) compared to controls (before control period: 1476 ± 633 s; after control period: 1274 ± 506 s; p = 0.017). OSA patients had reduced MVC and VATMS compared to controls throughout the fatiguing task as well as increased intracortical inhibition (all p 0.05 for all parameters). Conclusion This study demonstrates that severe OSA patients have cortical impairments which are likely contributing to their reduced knee extensors strength and endurance. Both cortical impairments and neuromuscular function are not improved following 8 weeks of CPAP treatment. Corresponding author: Dr. Samuel Verges, Laboratoire HP2 (U1042 INSERM), Univ. Grenoble Alpes, UM Sports Pathologies, Hôpital Sud, Avenue Kimberley, 38 434 Echirolles - France. E-mail: sverges@chu-grenoble.fr This work has been funded by the Fond de dotation AGIR pour les maladies chroniques and by the Fonds de dotation Recherche en Santé Respiratoire. MM, MG, SB, TLRM, BW, RT, PL and SV have nothing to disclose. JLP reports grants and personal fees from Philips, RESMED, Fisher & Paykel, grants from Fondation de la Recherche Médicale, Direction de la Recherche Clinique du CHU de Grenoble, Fonds de dotation "Agir pour les Maladies Chroniques", personal fees from Astra Zeneka, SEFAM, Agiradom, outside the submitted work. The results of the present study do not constitute endorsement by the American College of Sports Medicine. The authors declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 6 March 2018 © 2018 American College of Sports Medicine

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