Warning: A non-numeric value encountered in /home/public/export/export_srwxml.php on line 32

Warning: Cannot modify header information - headers already sent by (output started at /home/public/export/export_srwxml.php:32) in /home/public/includes/include.inc.php on line 5344
1.1 1 xml info:srw/schema/1/mods-v3.2 Liebermann D G author Goodman D author 2007 English The present study examined the effect of continuous vision and its occlusion in timing of pre-landing actions during free falls. When vision is occluded, muscle activation is hypothesized to start relative to onset of the fall. However, when continuous vision is available onset of action is hypothesized to be relative to the moment of touchdown. Six subjects performed 6 randomized sets of 6 trials after becoming familiar with the task. The 36 trials were divided in 2 visual conditions (vision and blindfold) and 3 heights of fall (15, 45 and 75 cm). EMG activity was recorded from the gastrocnemius and rectus femoris muscles during the falls. The latency of onset (L(o)) and the lapse from EMG onset to touchdown (T(c)) were obtained from these muscles. Vertical forces were recorded to assess the effects of pre-landing activity on the impacts at collision with and without continuous vision. Peak amplitude (F(max)), time to peak (T(max)) and peak impulse normalized to momentum (I(norm)) were used as outcome measures. Within flight time ranges of approximately 50-400 ms, the results showed that L(o) and T(c) follow a similar linear trend whether continuous vision was available or occluded. However, the variability of T(c) for each of the muscles was larger in the vision occluded condition. Analyses of variance showed that the rectus femoris muscle started consistently earlier in no vision trials. Finally, impact forces were not different in vision or blindfold conditions, and thus, they were not affected by minor differences in the timing of muscles prior to landing. Thus, it appears that knowing the surroundings before falling may help to reduce the need for a continuous visual input. The relevance of such input cannot be ruled out for falls from high landing heights, but cognitive factors (e.g., attention to specific cues and anticipation of a fall) may play a dominant role in timing actions during short duration falls encountered daily. Adult Analysis of Variance Biomechanics *Blindness *Electromyography Humans Joints/physiology Lower Extremity/physiology Male Movement/*physiology Muscle Skeletal/*physiology Orientation *Vision Ocular PMID:16600637 exported from refbase (https://refbase.nfshost.com/show.php?record=37), last updated on Mon, 31 Dec 2012 14:30:20 +0000 text http://www.ncbi.nlm.nih.gov/pubmed/16600637 http://www.ncbi.nlm.nih.gov/pubmed/16600637 10.1016/j.jelekin.2006.01.011 16600637 Liebermann+Goodman2007 2007 continuing periodical academic journal 17 2 212 227 1050-6411 1