Vastus lateralis motor unit firing rate is higher in women with patellofemoral pain

Alessio Gallina, Michael A. Hunt, Paul W. Hodges, S. Jayne Garland

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
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Objective: To compare neural drive, determined from motor unit firing rate, in the vastus medialis and lateralis in women with and without patellofemoral pain.

Design: Cross-sectional study.

Setting: University research laboratory.

Participants: Women (N=56) 19 to 35 years of age, including 36 with patellofemoral pain and 20 controls.

Interventions: Not applicable.

Main Outcome Measures: Participants sustained an isometric knee extension contraction at 10% of their maximal voluntary effort for 70 seconds. Motor units (N=414) were identified using high-density surface electromyography. Average firing rate was calculated between 5 and 35 seconds after recruitment for each motor unit. Initial firing rate was the inverse of the first 3 motor unit interspike intervals.

Results: In control participants, vastus medialis motor units discharged at higher rates than vastus lateralis motor units (P=.001). This was not observed in women with patellofemoral pain (P=.78) because of a higher discharge rate of vastus lateralis compared with control participants (P=.002). No between-group differences were observed for vastus medialis (P=.93). Similar results were obtained for the initial motor unit firing rate.

Conclusions: These findings suggest that women with patellofemoral pain have a higher neural drive to vastus lateralis but not vastus medialis, which may be a contributor of the altered patellar kinematics observed in some studies. The different neural drive may be an adaptation to patellofemoral pain, possibly to compensate for decreased quadriceps force production, or a precursor of patellofemoral pain.
Original languageEnglish
Pages (from-to)907-913
Number of pages7
JournalArchives of Physical Medicine and Rehabilitation
Issue number5
Early online date10 Feb 2018
Publication statusPublished - 1 May 2018


  • Knee joint
  • Neurophysiological
  • Pain syndrome
  • Patellofemoral
  • Quadriceps muscle
  • Recruitment
  • Rehabilitation


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