Conscious Drive to Stiffen the Leg Spring - Motor Strategies for an Internal Challenge

Mervyn Travers, James Debenham, William Gibson, Amity Campbell, Garry Allison

2013

Abstract

This study investigated the kinematic and muscle activity profiles at the ankle under two hopping conditions that consciously altered leg stiffness. Nine healthy volunteers performed multiple trials of bilateral hopping on a custom built sleigh under two conditions – preferred (PC) and short contact (SC). Leg stiffness, peak EMG, time to peak EMG and co-activation ratios for the medial gastrocnemius (MG), soleus (Sol) and tibialis anterior (TibAnt) muscles were compared across conditions. SC hopping resulted in increased leg stiffness. Importantly, Sol onset shifted from 86ms post-contact during PC to 14ms post-contact for SC. Similarly, MG onset was 41ms post-contact during PC and 22ms pre-contact for SC. Significantly earlier onsets of Sol and MG represent a shift into the feed-forward window which was not reflected by TibAnt. Comparisons revealed no significant differences in co-activation ratios (p>0.05) suggesting that increased leg stiffness during SC hopping was not a result of increased co-activation. Instead a dynamic strategy pairing pre-activation with an increased rate of activity of the agonist muscles to develop force in time for contact with the surface was observed. We suggest that the optimal strategy to consciously drive increased leg stiffness occurs via a feedforward response.

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Paper Citation


in Harvard Style

Travers M., Debenham J., Gibson W., Campbell A. and Allison G. (2013). Conscious Drive to Stiffen the Leg Spring - Motor Strategies for an Internal Challenge . In - icSPORTS, ISBN , pages 0-0


in Bibtex Style

@conference{icsports13,
author={Mervyn Travers and James Debenham and William Gibson and Amity Campbell and Garry Allison},
title={Conscious Drive to Stiffen the Leg Spring - Motor Strategies for an Internal Challenge},
booktitle={ - icSPORTS,},
year={2013},
pages={},
publisher={SciTePress},
organization={INSTICC},
doi={},
isbn={},
}


in EndNote Style

TY - CONF
JO - - icSPORTS,
TI - Conscious Drive to Stiffen the Leg Spring - Motor Strategies for an Internal Challenge
SN -
AU - Travers M.
AU - Debenham J.
AU - Gibson W.
AU - Campbell A.
AU - Allison G.
PY - 2013
SP - 0
EP - 0
DO -