title: Assessing contractile ability of the quadriceps muscle using ultrasound imaging.
abstract: Muscle dimension changes on ultrasound imaging (USI) indicate contractile activity. Quadriceps force and rectus femoris (RF) dimensions were examined to assess USI for estimating contraction level. In 15 healthy males, mean age 24.8 years, isometric quadriceps force was measured in 90° knee flexion during submaximal and maximal voluntary contractions (MVCs) and at MVC in extension. Mid-thigh cross-sectional area (CSA), depth and width, and surface electromyography (EMG) of RF were recorded. Muscle width decreased curvilinearly as both force and EMG increased. At MVC, width was 3.2 ± 0.5 cm, 25% smaller than at rest (4.4 ± 0.7 cm), and similar to MVC in extension (-23%). CSA decreased linearly to -18% at MVC. RF thickness increased by only 10% (at 30% to MVC). Similar width changes at MVC in flexion and extension indicate the clinical potential of USI for assessing quadriceps contractility. Sensitivity is limited to assessing strength to within 25% of MVC in young males.
authors.affiliation: School of Health Sciences, University of Southampton, Highfield Campus, Building 45, Southampton, Hampshire SO17 1BJ, UK.
authors.forename: Sinead
authors.initials: S
authors.lastname: Delaney
authors.forename: Peter
authors.initials: P
authors.lastname: Worsley
authors.forename: Martin
authors.initials: M
authors.lastname: Warner
authors.forename: Mark
authors.initials: M
authors.lastname: Taylor
authors.forename: Maria
authors.initials: M
authors.lastname: Stokes
mesh_terms: D000293:Adolescent; D000328:Adult; D019412:Anatomy, Cross-Sectional; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction; D007717:Knee / Q000502:physiology; D008297:Male; D011187:Posture / Q000502:physiology; D052097:Quadriceps Muscle / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000502:physiology*; D015203:Reproducibility of Results; D012146:Rest; D013848:Thigh / Q000033:anatomy & histology; D014463:Ultrasonography; D055815:Young Adult