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Most outdoor and many indoor walking environments present abrupt elevation changes of 1.25 cm (0.5 in) or more. Such bumps can disrupt walking as well as travel on small wheels (e.g., skates or skateboards), yet serious accidents from tripping are reasonably infrequent given how much walking is done. Data are presented from walkway profile surveys and factors affecting human ambulatory behavior. Relevance to industry Falls on the same level produce a substantial portion of workplace injuries. Improved understanding of the role of perception and expectation in such falls can lead to improved strategies for preventing injuries.

Stereophotogrammetry was used to investigate the functional relations between the articular surface geometry, contact patterns, and kinematics of the glenohumeral joint. Nine normal shoulder specimens were elevated in the scapular plane by using simulated muscle forces in neutral rotation (NR) and starting rotation (SR). Motion was quantified by analyzing the translations of the geometric centers of the humeral head cartilage and bone surfaces relative to the glenoid surface. In both NR and SR, the ranges of translations of the center of the humeral head cartilage surface were greatest in the inferior-superior direction (NR 2.0 +/- 0.7 mm, SR 2.9 +/- 1.2 mm). Results of this study also show that joints with less congruence of the articular surfaces exhibit larger translations, and elevation in SR yields greater translations than in NR. Kinematic analyses with the humeral head bone surface data yielded larger values of translation than analyses that used the cartilage surface data, suggesting that similar overestimations may occur in radiographic motion studies. Results of this study demonstrate that small translations of the humeral head center occurred in both SR and NR. The proximity of the origin of the helical axes to the geometric center of the humeral head articular surface confirmed that glenohumeral elevation is mainly rotation about this geometric center with small translations.