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Bradley, N L.1; Stotz, P1; Goodman, D1
1Simon Fraser University, Burnaby, BC, Canada
(Sponsor: Don C. McKenzie, FACSM)
Postural stability is now considered an essential component of any motor act. One often notes a somewhat standardized anticipatory response to voluntarily induced destabilizing movements. However, little attention has been given to the effect of previous experience on balance response.
To determine whether or not ice hockey players, who practice and compete in an unstable environment, make non-standard anticipatory postural adjustments to deal with perturbations to stability. Junior ice hockey players (skilled) were compared to non-skaters (unskilled) to examine effects of previous experience on the balance response.
Skin surface electrodes were placed over the muscle bellies of gastrocnemius (GA), biceps femoris (BF) and erector spinae (ES) of 6 skilled and 6 unskilled subjects. A triaxial accelerometer was affixed to the ventral surface of the right hand. Subjects performed rapid bimanual shoulder flexions to 20 degrees (Small Perturbation, Ps) and 80 degrees (Large Perturbation, PL). The task was performed on both stable (barefoot) and unstable (in-line skates) surfaces. Muscle activation response time to the self-induced balance perturbation was calculated relative to the initiation of arm movement.
Significant effects were found for both Perturbation (p <0.01) and Perturbation by Skill level (p < 0.05). BF activated first more often in PL than Ps (51±9 vs. 31±7%) across groups and surfaces. However, skilled showed the same BF response to Ps as to PL (45±10 vs. 52±12%), while unskilled showed a much lower percentage in Ps than PL (16±10 vs. 50±12%).
Both groups (skilled and unskilled) primarily adopted a hip strategy to compensate for the perturbation. The unskilled subjects dealt with Ps differently than PL. This was not the case for the skilled subjects. It appears that extensive training on an unstable surface contributes to skilled subjects exhibiting a balance maintenance response for large perturbations which is also utilized in the face of small perturbations.
Supported by NSERC and CIHR CAR Grants 43276
©2003The American College of Sports Medicine
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