yes / The present study introduces four event detection algorithms for defining touch-down and foot-off during stair descent and stair ascent using segmental kinematics. For stair descent, vertical velocity minima of the whole body center-of-mass was used to define touch-down, and foot-off was defined as the instant of trail limb peak knee flexion. For stair ascent, vertical velocity local minima of the lead-limb toe was used to define touch-down, and foot-off was defined as the local maxima in vertical displacement between the toe and pelvis. The performance of these algorithms was determined as the agreement in timings of kinematically derived events to those defined kinetically (ground reaction forces). Data were recorded while 17 young and 15 older adults completed stair descent and ascent trials over a four-step instrumented staircase. Trials were repeated for three stair riser height conditions (85 mm, 170 mm, and 255 mm). Kinematically derived touch-down and foot-off events showed good agreement (small 95% limits of agreement) with kinetically derived events for both young and older adults, across all riser heights, and for both ascent and descent. In addition, agreement metrics were better than those returned using existing kinematically derived event detection algorithms developed for overground gait. These results indicate that touch-down and foot-off during stair ascent and descent of non-instrumented staircases can be determined with acceptable precision using segmental kinematic data.

Yes / Falls on stairs are a common and dangerous problem for older people. This series of studies evaluated whether or not selected changes to the appearance of stairs could make them safer for older people to negotiate. Objectives: To determine the effect of (1) a step edge highlighter and its position and (2) an optimised horizontal–vertical (H–V) visual illusion placed on a step riser on gait safety during stair descent and ascent. Design: A series of studies using a repeated measures, laboratory-based design, investigating gait control and safety in independently mobile older people. Setting: The University of Bradford Vision and Mobility Laboratory. Participants: Fit and healthy older people aged 60 years of age or more, independently mobile, reasonably active and with normal healthy eyes and corrected vision. Interventions: A step edge highlighter in a variety of offsets from the stair edge and an optimised H–V visual illusion placed on the stair riser. The H–V illusion was provided on a staircase by horizontal step edge highlighters on the tread edges and vertical stripes on the step risers. Main outcome measures: Gait parameters that are important for safe stepping in ascent and descent, particularly toe clearance during stair ascent and heel clearance during stair descent. Results: The step edge highlighter increased the precision of heel clearance during stepping and its positioning relative to the tread edge determined the extent of heel clearance over the tread edge. Positioning the highlighter away from the tread edge, as is not uncommonly provided by friction strips, decreased heel clearance significantly and led to greater heel scuffs. Although psychophysics experiments suggested that higher spatial frequencies of the H–V illusion might provide greater toe clearance on stair ascent, gait trials showed similar increased toe clearances for all spatial frequencies. When a 12 cycle per step spatial frequency H–V illusion was used, toe clearance increases of approximately 1 cm (17.5%) occurred without any accompanying changes in other important gait parameters or stability measures. Conclusions: High-contrast tread edge highlighters present on steps and stairs and positioned flush with the edge of the tread or as near to this as possible should improve stair descent safety in older people. A H–V illusion positioned on the riser of a raised surface/walkway (e.g. kerbs) and/or the top and/or bottom of a stairway is likely to increase foot clearance over the associated step/stair edge, and appears not to lead to any decrement in postural stability. Thus, their use is likely to reduce trip risk and hence improve stair ascent safety. The effect of the step and stair modifications should be assessed in older people with visual impairment. The only other remaining assessment that could be made would be to assess fall prevalence on steps and stairs, perhaps in public buildings, with and without these modifications. / National Institute for Health Research, Public Health Research programme. PHR programme as project number 10/3009/06