K.L. Mills, V.C. Kollar, S.L. Eliason, E.C. Thomas, S.R. Sheahan, & B.K. Higginson

Gonzaga University, Spokane, WA

The kinematics of obstacle clearance during anterior load carriage have been well studied. However, the effect of visual impairment during obstacle clearance is less understood. Likewise, few studies have examined changes in kinetic measures during obstacle clearance and none have included both kinetic and kinematic measures. PURPOSE: This study investigated kinetic and kinematic changes in obstacle clearance during anterior load carriage in a younger, working-age population. Loads of differing size but the consistent mass were used to examine the effect of visual impairment due to anterior load carriage on stability during obstacle clearance. METHODS: Seventeen subjects (age: 20.5 ± 1.09 yr) able to carry loads up to 15% of their body weight participated in this study. Subjects performed 20 passes over a breakaway obstacle set at 40% of greater trochanter height for three conditions: a control trial with no anterior load (CTL), a visually obstructive anterior load (OBS), and a non-visually obstructive anterior load (NON-OBS). Both loads were 15% of the subject’s body weight. Kinematic measures included step time (ST), step distance (SD), and toe clearance (TC). The kinetic measure used was loading rate (LR) examined in both lead and trail limbs. With each pass, 2-D sagittal plane videography captured ST, SD, and TC, while a runway force plate was used to quantify LR. All measures were compared using a repeated measures ANOVA. RESULTS: SD was significantly shorter in OBS compared to the CTL (1.145± 0.084cm, p=.000) and NON-OBS (1.362± 0.133cm, p=.000). However, ST and trail limb LR were significantly less in the CTL than OBS (0.435±0.071s, p=.000 and 1818.2±412.8N/s, p=.001, respectively). No significant differences were found between CTL and OBS for TC (0.177 ± .056cm, p=.019). The test for within subjects effects found no differences between any conditions for lead limb LR (p=.499). CONCLUSION: Overall visual impairment does induce a change in obstacle clearance strategy observed in both kinematic and kinetic parameters. Of these observed changes, SD appears to be most influenced by visual impairment.

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