title: Delayed onset of electromyographic activity of the vastus medialis relative to the vastus lateralis may be related to physical activity levels in females with patellofemoral pain.
abstract: The aims of this study were to examine group differences in muscle activation onset of the vastus medialis (VM) in relation to the vastus lateralis (VL) and pain level during stair ascent in females with patellofemoral pain (PFP) who maintain high and moderate levels of physical activity; to determine the association between physical activity level and muscle activation onset. Forty-three females with PFP and thirty-eight pain-free females were recruited and divided into four groups based on their level of physical activity: females with PFP (n=26) and pain-free females (n=26) who practiced a moderate level of physical activity and females with PFP (n=17) and pain-free females (n=12) who practiced an intense amount of physical activity. Participants were asked to ascend a seven-step staircase and the VM and VL activation onset was determined. Females with PFP who practiced high level of physical activity demonstrated delayed onset of VM (4.06ms) compared to healthy females (-14.4ms). Conversely, females with PFP who practiced moderate level of physical activity did not present VM delay (-2.48ms) in comparison to healthy females (-9.89ms). Furthermore, physical activity significantly correlated to the muscle activation onset difference (p=0.005; R=0.60). These findings may explain why controversial results regarding VM and VL muscle activation onset have been found.
authors.affiliation: Department of Physiotherapy, University of State of Sao Paulo, UNESP, Presidente Prudente, SP, Brazil.
authors.forename: Ronaldo Valdir
authors.initials: RV
authors.lastname: Briani
authors.affiliation: Department of Physiotherapy, University of State of Sao Paulo, UNESP, Presidente Prudente, SP, Brazil.
authors.forename: Danilo
authors.initials: D
authors.lastname: de Oliveira Silva
authors.affiliation: Department of Physiotherapy, University of State of Sao Paulo, UNESP, Presidente Prudente, SP, Brazil.
authors.forename: Marcella Ferraz
authors.initials: MF
authors.lastname: Pazzinatto
authors.affiliation: Department of Physiotherapy, University of State of Sao Paulo, UNESP, Presidente Prudente, SP, Brazil.
authors.forename: Amanda Schenatto
authors.initials: AS
authors.lastname: Ferreira
authors.affiliation: Department of Bioengineering, University of São Paulo, USP, São Carlos, SP, Brazil.
authors.forename: Deisi
authors.initials: D
authors.lastname: Ferrari
authors.affiliation: Department of Physiotherapy, University of State of Sao Paulo, UNESP, Presidente Prudente, SP, Brazil. Electronic address: micolis@fct.unesp.br.
authors.forename: Fábio Mícolis
authors.initials: FM
authors.lastname: de Azevedo
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D009043:Motor Activity / Q000502:physiology*; D010146:Pain / Q000175:diagnosis / Q000503:physiopathology; D046788:Patellofemoral Pain Syndrome / Q000175:diagnosis* / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000502:physiology / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
keywords: Knee pain; Muscle activity; Onset; Quadriceps