The movement of the center of mass (COM) during human walking has been hypothesized to follow a sinusoidal pattern in the vertical and mediolateral directions. The vertical COM displacement has been shown to increase with velocity, but little is known about the mediolateral movement of the COM. In our evaluation of the mediolateral COM displacement at several walking speeds, 10 normal subjects walked at their self-selected speed and then at 0.7, 1.0, 1.2, and 1.6 m/s in random order. We calculated COM location from a 15segment, full-body kinematic model using segmental analysis. Mediolateral COM displacement was 6.99 +/-1.34 cm at the slowest walking speed and decreased to 3.85 +/-1.41 cm at the fastest speed (p < 0.05). Vertical COM excursion increased from 2.74 +/-0.52 at the slowest speed to 4.83 +/-0.92 at the fastest speed (p < 0.05). The data suggest that the relationship between the vertical and mediolateral COM excursions changes substantially with walking speed. Clinicians who use observational gait analysis to assess walking problems should be aware that even normal individuals show significant mediolateral COM displacement at slow speeds. Excessive vertical COM displacement that is obvious at moderate walking speeds may be masked at slow walking speeds.Abbreviations: ANOVA = analysis of variance, COM = center of mass, fps = frames per second, SS = self-selected.
Abstract-This study identified clinical (e.g., etiology) and demographic factors related to prosthesis use in persons with upper-and lower-limb amputation (ULA and LLA, respectively) and the effect of phantom limb pain (PLP) and residual limb pain (RLP) on prosthesis use. A total of 752 respondents with LLA and 107 respondents with ULA completed surveys. Factors related to greater use (hours per day) for persons with LLA included younger age, full-or part-time employment, marriage, a distal amputation, an amputation of traumatic etiology, and an absence of PLP. Less use was associated with reports that prosthesis use worsened RLP, and greater prosthesis use was associated with reports that prosthesis use did not affect PLP. Having a proximal amputation and reporting lower average PLP were related to greater use in hours per day for persons with an ULA, while having a distal amputation and being married were associated with greater use in days per month. Finally, participants with LLA were significantly more likely to wear a prosthesis than those with ULA. These results underscore the importance of examining factors related to prosthesis use and the differential effect that these variables may have when the etiology and location of amputation are considered.
We surveyed 54 female dancers in two professional ballet companies. A total of 27 fractures were reported in 17 dancers. Metatarsal fractures were the most common (63%), followed by fractures of the tibia (22%) and spine (7%). Dancers who danced greater than 5 hours per day were significantly more likely to have a stress fracture than those dancing less than 5 hours per day. Dancers in the stress fracture group also had a significantly longer duration of amenorrhea than those in the group with no stress fractures. No significant difference was found between the dancers who had stress fractures and those who did not with regard to any of the other variables examined. These data suggest that prolonged amenorrheic intervals and heavy training schedules may predispose ballet dancers to stress fractures. Of the 17 dancers with stress fractures, only 1 had neither of these risk factors.
The FFI appears to be a reasonable tool for low functioning individuals with foot disorders. It may not be appropriate for individuals who function at or above the level of independent activities of daily living.
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