title: Influence of obstructive sleep apnea syndrome in the fluctuation of the submaximal isometric torque of knee extensors in patients with early-grade osteoarthritis.
abstract: OBJECTIVE
  The aim of this study was to investigate whether obstructive sleep apnea (OSA) alters the fluctuation of submaximal isometric torque of the knee extensors in patients with early-grade osteoarthritis (OA).
  
  
  METHODS
  The study included 60 male volunteers, aged 40 to 70 years, divided into four groups: Group 1 (G1) - Control (n=15): without OA and without OSA; Group 2 (G2) (n=15): with OA and without OSA; Group 3 (G3) (n=15): without OA and with OSA; and Group 4 (G4) (n=15) with OA and with OSA. Five patients underwent maximal isometric contractions of 10 seconds duration each, with the knee at 60° of flexion to determine peak torque at 60°. To evaluate the fluctuation of torque, 5 submaximal isometric contractions (50% of maximum peak torque) of 10 seconds each, which were calculated from the standard deviation of torque and coefficient of variation, were performed.
  
  
  RESULTS
  Significant differences were observed between groups for maximum peak torque, while G4 showed a lower value compared with G1 (p=0.005). Additionally, for the average torque exerted, G4 showed a lower value compared to the G1 (p=0.036). However, no differences were found between the groups for the standard deviation (p=0.844) and the coefficient of variation (p=0.143).
  
  
  CONCLUSIONS
  The authors concluded that OSA did not change the parameters of the fluctuation of isometric submaximal torque of knee extensors in patients with early-grade OA.
authors.affiliation: Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, BR.
authors.forename: Andressa
authors.initials: A
authors.lastname: Silva
authors.affiliation: Departamento de Esportes, Universidade Federal de Minas Gerais, Belo Horizonte, MG, BR.
authors.forename: Marco T
authors.initials: MT
authors.lastname: Mello
authors.affiliation: Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, BR.
authors.forename: Paula R
authors.initials: PR
authors.lastname: Serrão
authors.affiliation: Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, BR.
authors.forename: Roberta P
authors.initials: RP
authors.lastname: Luz
authors.affiliation: Departamento de Psicobiologia, Universidade Federal de São Paulo, São Paulo, SP, BR.
authors.forename: Lia R
authors.initials: LR
authors.lastname: Bittencourt
authors.affiliation: Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, BR.
authors.forename: Stela M
authors.initials: SM
authors.lastname: Mattiello
mesh_terms: D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007717:Knee / Q000502:physiology*; D010003:Osteoarthritis / Q000503:physiopathology*; D016059:Range of Motion, Articular; D020181:Sleep Apnea, Obstructive; D019415:Torque