Does osteoporosis predispose falls? a study on obstacle avoidance and balance confidence

Contains fulltext : 96832.pdf (publisher's version ) (Open Access)BACKGROUND: Osteoporosis is associated with changes in balance and physical performance and has psychosocial consequences which increase the risk of falling. Most falls occur during walking; therefore an efficient obstacle avoidance performance might contribute to a reduction in fall risk. Since it was shown that persons with osteoporosis are unstable during obstacle crossing it was hypothesized that they more frequently hit obstacles, specifically under challenging conditions. METHODS: Obstacle avoidance performance was measured on a treadmill and compared between persons with osteoporosis (n = 85) and the comparison group (n = 99). The obstacle was released at different available response times (ART) to create different levels of difficulty by increasing time pressure. Furthermore, balance confidence, measured with the short ABC-questionnaire, was compared between the groups. RESULTS: No differences were found between the groups in success rates on the obstacle avoidance task (p = 0.173). Furthermore, the persons with osteoporosis had similar levels of balance confidence as the comparison group (p = 0.091). The level of balance confidence was not associated with the performance on the obstacle avoidance task (p = 0.145). CONCLUSION: Obstacle avoidance abilities were not impaired in persons with osteoporosis and they did not experience less balance confidence than the comparison group. These findings imply that persons with osteoporosis do not have an additional risk of falling because of poorer obstacle avoidance abilities

THE NUCLEAR ENCOUNTER PROBABILITY

This Letter dicusses the nuclear encounter probability as used in ion channeling analysis. A formulation is given, incorporating effects of large beam angles and beam divergence. A critical examination of previous definitions is made

A study of channeling patterns from strained Si1-xGex/Si bilayers close to (011) axes

This paper characterises the angular intensity distribution of MeV protons transmitted through strained Si1-xGex/Si bilayers close to the axis. The ring-like intensity distribution produced by the front layer axis when it is aligned close to the beam direction is projected either towards or away from the rotated back layer axis. The resultant transmitted angular intensity distribution depends on both the bilayer tilt angle and the interface rotation angle. Previously unobserved intensity distributions through such structures are simulated using a Monte Carlo channeling code, and similar behaviour is also observed in channeling patterns recorded from thinned, strained Si1-xGex/Si bilayers

Characterization of strain in crystal bilayers using ion-channeling patterns

This paper describes the experimental and theoretical simulation, the observation and the quantification of strain present in crystal bilayers using ion-channeling patterns produced-by a focused 3 MeV proton beam. The dechanneling effects of strain are first experimentally simulated using different rotation angles between two individual, 0.3-mu m-thick, [100] silicon crystals. The patterns produced when both crystals are aligned close to the [100] axis, with a small rotation angle at the interface, are considered in detail using Monte Carlo computer simulations. Previously unobserved effects occurring in channeling patterns are discussed and general conditions under which different behavior is observed are described. Channeling patterns recorded through a thinned Si0.85Ge0.15/Si crystal bilayer are then used to characterize the interface rotation angle dong several off-normal axes