The influence of footwear sole hardness on slip initiation and falls in young adults

Unrestricted The overall objective of this dissertation was to determine the influence of footwear sole hardness on slip initiation and falls. To achieve this goal, three separate studies were undertaken. The purpose of the first study was to determine the influence of sole hardness on peak utilized coefficient of friction (COFu) during walking. Ground reaction forces, full body kinematics, and subjective ratings of footwear slipperiness were obtained from 56 young adults while wearing hard and soft soled shoes. Peak COFu was significantly less when wearing hard soled shoes compared to when wearing soft soled shoes. The decrease in peak COFu was attributed to a decrease in total body center of mass (COM) acceleration prior to and immediately following initial contact. The purpose of the second study was to determine the influence of sole hardness on the probability of slip initiation. Forty young adults were randomized into hard and soft sole groups. Peak COFu was obtained during a non-slippery floor condition while slip probability was assessed during a slippery floor condition. Despite the lower COFu in the hard sole group, the proportion of slip events was found to be greater than the soft sole group. The purpose of third study was to investigate the influence of sole hardness on the probability of slip-induced falls. Slip characteristics and fall probability during a slippery floor trial were compared between hard and soft sole groups. The proportion of fall events in the hard sole group was not statistically different than the proportion of fall events in the soft sole group. In addition, no differences were observed between shoe groups for slip distance, average heel and COM slipping velocity. Collectively, the results of this dissertation support the premise that individuals wearing shoes with hard soles are at greater risk for slip initiation, but not greater risk of falls.; Although individuals demonstrate gait adaptations to reduce the friction demand when wearing hard soled shoes that are perceived to be more slippery, these behavioral adaptations do not appear to decrease the risk of slips.无限制：本学位论文的总体研究目标为明确鞋底硬度对滑倒起始及跌倒发生的影响。为实现该研究目标，共开展三项独立实验。 第一项实验旨在探究鞋底硬度对行走过程中峰值利用摩擦系数（peak utilized coefficient of friction, COFu）的影响。研究招募56名青年受试者，让其分别穿戴硬底鞋与软底鞋进行行走测试，采集地面反作用力（ground reaction forces）、全身运动学数据（full body kinematics）以及受试者对鞋底滑度的主观评分。结果显示，穿戴硬底鞋时的峰值利用摩擦系数显著低于穿戴软底鞋时的水平。峰值利用摩擦系数的降低，归因于初始接触瞬间前后全身质心（center of mass, COM）加速度的下降。 第二项实验旨在明确鞋底硬度对滑倒起始概率的影响。将40名青年受试者随机分为硬底鞋组与软底鞋组。在非滑地板面条件下采集受试者的峰值利用摩擦系数，随后在滑地板面条件下评估其滑倒概率。尽管硬底鞋组的峰值利用摩擦系数更低，但研究发现硬底鞋组的滑倒事件占比高于软底鞋组。 第三项实验旨在探究鞋底硬度对滑倒引发跌倒的概率的影响。对比两组受试者在滑地板面测试中的滑倒特征及跌倒发生概率。结果显示，硬底鞋组的跌倒事件占比与软底鞋组相比，无统计学意义上的显著差异。此外，两组受试者在滑倒距离、平均足跟及质心滑倒速度方面均未观察到显著差异。 综上，本学位论文的研究结果支持如下前提：穿戴硬底鞋的个体滑倒起始风险更高，但跌倒风险并未随之升高。尽管受试者在穿戴被感知为滑度更高的硬底鞋时，会通过调整步态来降低摩擦需求，但这类行为调整似乎并未降低滑倒风险。