Entrainment of vastus medialis complex activity differs between genders.
BACKGROUND
That the vastus medialis oblique (VMO) is a functional unit of the vastus medialis (VM) is disputed. Delayed VMO activation predicts patellofemoral pain, which has higher rates in women.


METHODS
Single MUs and surface electromyogram (EMG) were collected from the VMO and VM of 9 men and 9 women. Men were tested once; women were tested during 5 menstrual phases. Coherence was assessed for motor unit (MU) firings within and between the VM and VMO using multilevel logistic models to determine statistical significance.


RESULTS
Compared with women, men have 741% (MU pairs) and 256% (MU-EMG pairs) greater odds of common drive (0-5 Hz) coherent oscillations. MU pairs from the VMO and the dual VM/VMO complex have 228% and 212% greater odds of coherent oscillations in the beta band (15-35 Hz) compared with VM pairs.


CONCLUSIONS
The VM and VMO are neurologically different muscles; control of the VM complex is sexually dimorphic.
Department of Kinesiology and Health Education, University of Texas at Austin, Austin, Texas, USA.|US Army Research Laboratory-Human Research and Engineering Directorate, Aberdeen Proving Ground, RDRL-HRS-B, Maryland, USA.
Matthew S
MS
Tenan
Department of Exercise and Sport Science, Department of Nutrition, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 21005-5425, USA.
Anthony C
AC
Hackney
Department of Kinesiology and Health Education, University of Texas at Austin, Austin, Texas, USA.
Lisa
L
Griffin
D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D015331:Cohort Studies; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008597:Menstrual Cycle / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D012727:Sex Characteristics; D055815:Young Adult
gender differences; knee; menstrual cycle; motor unit; quadriceps; vastus medialis oblique