The effects of everyday concurrent tasks on overground minimum toe clearance and gait parameters

Deaths and injuries resulting from falls are a significant problem for older adults. Over half of falls during walking result from a trip, and these are likely to begin when the foot contacts the ground at the point of minimum toe clearance (MTC) during the swing phase where the foot most closely approaches the ground. MTC is commonly investigated using a limited number of points and on a treadmill, which cannot account for flooring irregularities, speed changes, and direction changes of overground gait. This paper presents a new method of calculating 3D overground MTC that accounts for flooring variations and utilizes hundreds of points on each shoe. These methods are applied to 10 unimpaired adults during habitual gait: (1) without a concurrent task, (2) while carrying a 9-kg laundry basket, (3) while carrying a tray with a full glass of water on it, and (4) while answering standardized conversational questions. Results indicated that steps were slower and shorter during concurrent tasks while MTC changes were dependent on task type (higher for basket, lower for questions, and unchanged for water). Task-related MTC changes were independent of spatiotemporal gait changes. Thus, MTC during overground gait, particularly while concurrent tasks are being performed, may be an independent fall risk factor that merits further investigation in subjects at-risk of falls. The relationships between MTC, gait parameters, and older age or fall risk should be explored further in at-risk subjects and circumstances to elucidate potential tripping mechanisms.