The purpose of this study was to determine the effect of heel lifts on ground reaction force patterns in subjects with structural leg-length discrepancies (LLDs). Eighteen subjects with LLDs ranging from 4.8 to 22.2 mm participated in this study. Subject age range was from 20 to 63 years. A force platform was used to obtain ground reaction force data for four conditions. Data were collected prior to fitting of the heel lift and after a three-week break-in period. Data were analyzed by use of a two-factor within-subject analysis of variance for repeated measures. Before heel-lift fitting, maximum lateral force was greater in the short leg than in the long leg. After heel-lift fitting, maximum vertical force was greater within both legs, and maximum medical force was greater in the long leg than in the short leg. The results suggest that although heel lifts are used to achieve pelvic levelness, the use of heel lifts also resulted in increased ground reaction forces, which may cause increased joint stresses within the lower extremities.
The relationship between variations in wheelchair racers’ frontal area in erect, flexed, and rotated upper trunk positions and coasting efficiency was investigated in two experiments. The first involved three male racers with national and international racing experience, and the second involved four men and three women with national or international racing experience. In both experiments, frontal area changed significantly across the three positions. Concurrently, reductions in frontal area coincided predictably with reductions in the percent of initial velocity loss experienced during the coast-down tests across the postural conditions within both experiments. Through ANOVA with repeated measures, the flexed position demonstrated significantly better coasting efficiency than the erect condition in Experiment 1. In Experiment 2, the rotated condition demonstrated significantly better coasting efficiency than the erect condition. Generally, the results support the contention that wheelchair coasting efficiency can be improved by adopting upper torso positions that reduce the racer’s frontal area.
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