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Discharge properties of abductor hallucis before, during and after an isometric fatigue task.

Discussion in 'Biomechanics, Sports and Foot orthoses' started by CraigT, Jun 11, 2013.

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  1. CraigT

    CraigT Well-Known Member


    Members do not see these Ads. Sign Up.
    Good work from Pod Arena contributor Luke Kelly that I don't think Newsbot picked up on...

    http://jn.physiology.org/content/early/2013/05/10/jn.00944.2012.abstract

    Discharge properties of abductor hallucis before, during and after an isometric fatigue task.
    Luke A Kelly1, Sebastien Racinais2, and Andrew G. Cresswell3,*
    + Author Affiliations

    1Aspetar, Qatar Orthopaedic & Sports Medicine Hospital
    2Aspetar, Qatar Orthopaedic and Sports Medicine Hospital
    3The University of Queensland
    ↵* The University of Queensland a.cresswell@uq.edu.au
    Submitted 7 November 2012. Revision received 13 May 2013. Accepted 14 May 2013.
    Abstract
    Abductor hallucis is the largest muscle in the human foot, and is comprised of relatively few motor units. It has been described as a postural muscle, aiding in stabilization of the longitudinal arch. The purpose of this study was to describe the discharge properties of abductor hallucis motor units during ramp and hold isometric contractions, as well during fatigue. Intramuscular electromyographic recordings from abductor hallucis were made in five subjects and 42 single motor units were decomposed. Data was recorded from 60% maximum voluntary contraction (MVC) isometric ramp contractions, performed before and after a sub-maximal, isometric contraction to failure (mean force 41.3±15.3%MVC, mean duration 233±116s). Motor units were recruited from 10.3 - 54.2% MVC. No significant difference was observed between recruitment and de-recruitment thresholds or their respective discharge rates for both the initial and post fatigue ramp contractions (all P>0.25). Recruitment threshold was positively correlated with recruitment discharge rate (r=0.47, P<0.003). All motor units attained similar peak discharge rates (14.0±0.25pps) and were not correlated with recruitment threshold. Thirteen motor units could be followed during the fatigue task. A decline in discharge rate and an increase in discharge variability occurred in the final 25% of the task (both P<0.005). Abductor hallucis is known to have a low number of motor units, relative to its physiological cross sectional area. We have shown that these motor units discharge relatively slowly and are considerably resistant to fatigue. These characteristics may be effective for generating and sustaining substantial levels of force for prolonged periods.


    Can you clean up the link please admin?



    PS- This was missed- in the Journal of Neurophysiology- but the paper on laser for Plantar Fasciitis was pick up in the 'JOURNAL OF RAFSANJAN UNIVERSITY OF MEDICAL SCIENCES AND HEALTH SERVICES' (!!!!!!)
     
  2. HansMassage

    HansMassage Active Member

    Observation: When in contact with the ground force, resists external rotation of the foot. When hypertonic and not in contact with ground force causes distortion of the joint. Therefore reduction of posture distortion that causes excessive external rotation of the lower extremity should reduce hypervigilance in the abductor hallucis and thus bunion pain.
    Hans Albert Quistorff, LMP
    Antalgic Posture Pain Specialist
     
  3. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    Anatomical Location of Motor Points of the Abductor Hallucis Muscles
    José Scarpa et al
    The FASEB Journal
    vol. 29 no. 1 Supplement 864.2

     
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