title: Facilitation of quadriceps activation is impaired following eccentric exercise.
abstract: Contracting the knee flexor muscles immediately before a maximum voluntary contraction (MVC) of knee extension increases the maximal force that the extensor muscles can exert. It is hypothesized that this phenomenon can be impaired by muscle fiber damage following eccentric exercise [delayed onset muscle soreness (DOMS)]. This study investigates the effect of eccentric exercise and DOMS on knee extension MVC immediately following a reciprocal-resisted knee flexion contraction. Electromyography (EMG) was recorded from the knee extensors and flexors of 12 healthy men during knee extension MVCs performed in a reciprocal (maximal knee extension preceded by resisted knee flexion), and nonreciprocal condition (preceded by relaxation of the knee flexors). At baseline, knee extension MVC force was greater during the reciprocal condition (P < 0.001), whereas immediately after, 24 and 48 h after eccentric exercise, the MVC force was not different between conditions. Similarly, at baseline, the EMG amplitude of the quadriceps during the MVC was larger for the reciprocal condition (P < 0.001). However, immediately after, 24 and 48 h postexercise the EMG amplitude was similar between conditions. In conclusion, eccentric exercise abolished the facilitation of force production for the knee extensors, which normally occurs when maximum knee extension is preceded by activation of the knee flexors.
authors.affiliation: Department of Physical Education and Sport Science, University of Bojnord, Bojnord, Iran; Department of Health Science and Technology, Center for Sensory-Motor Interaction (SMI), Aalborg University, Aalborg, Denmark.
authors.forename: N
authors.initials: N
authors.lastname: Hedayatpour
authors.forename: L
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.forename: D
authors.initials: D
authors.lastname: Falla
mesh_terms: D000328:Adult; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D063806:Myalgia / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000473:pathology / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult