title: Muscle activation and coactivation during five-time-sit-to-stand movement in patients undergoing total knee arthroplasty.
abstract: Quadriceps weakness is prevalent with knee osteoarthritis (OA) and after total knee arthroplasty (TKA). To compensate for quadriceps dysfunction, patients often alter movement strategies. Little is known about muscle coordination during sit-to-stand (concentric) and stand-to-sit (eccentric) movements in the acute postoperative period. This investigation characterized the distribution of muscle activation between the concentric and eccentric phases during a five-time-sit-to-stand (FTSTS) movement in late stage OA and one month after TKA. Patients and healthy participants performed a FTSTS while recording bilateral ground reaction forces (GRFs) and electromyography (EMG). Concentric and eccentric ensemble averages of the GRF and EMG were calculated for the concentric and eccentric phases. Coactivation indices, integrated EMG, and GRF were calculated for each limb and phase. Patients demonstrated higher eccentric coactivation than the healthy group. Postoperative loading was higher in the nonsurgical limb. Postoperative quadriceps activity was lower in the concentric phase and higher in the eccentric phase than the healthy group. Higher coactivation in the patients resulted from sustained distribution of quadriceps activity throughout the eccentric phase. This indicated an inability to coordinate muscle firing when rapidly lowering to a chair and occurred despite unloading of the surgical limb. Although these patterns may serve as a protective strategy, they may also impede recovery of muscle function after TKA.
authors: Department of Mechanical and Materials Engineering, University of Denver, United States; Department of Physical Medicine and Rehabilitation, University of Colorado Anschutz Medical Campus, United States. Electronic address: bradley.davidson@du.edu.
authors: Bradley S
authors: BS
authors: Davidson
authors: Dana L
authors: DL
authors: Judd
authors: Abbey C
authors: AC
authors: Thomas
authors: Ryan L
authors: RL
authors: Mizner
authors: Donald G
authors: DG
authors: Eckhoff
authors: Jennifer E
authors: JE
authors: Stevens-Lapsley
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D053581:Muscle Strength Dynamometer; D020370:Osteoarthritis, Knee / Q000503:physiopathology* / Q000601:surgery*; D011184:Postoperative Period; D052097:Quadriceps Muscle / Q000503:physiopathology* / Q000601:surgery; D016896:Treatment Outcome; D016474:Weight-Bearing / Q000502:physiology
keywords: Coactivation; Electromyography; Osteoarthritis; Quadriceps strength; Sit to stand; TKA