1st Joint ESMAC-GCMAS Meeting - Análise de Marcha

situated between the safety harness and the overhead track was used to measure the forces
exerted through the harness. The horizontal displacement of the heel marker at the moment of
contact with the floor was used to define the onset of a slip event. Slip termination was defined
when the heel marker stopped its forward displacement or the contralateral leg contacted the
ground. The determination of a fall was made if the load cell data revealed that the peak force
exerted through the harness was greater than 25% of body weight. Slip distance and the peak
heel velocity during the slip event were compared between shoe conditions using independent
t-tests. Fall probability was compared between shoe conditions using a Chi-square test.
Results
On average, the self-selected fast walking speed of the hard and soft soled shoe groups were
similar (Table 1). All subjects in both groups experienced a slip event. Eight of twenty subjects
(40%) in the hard soled shoe group experienced a fall, while six of the twenty subjects (30%)
in the soft soled shoe group experinced a fall (Table 2). The proportion of fall events in the
hard soled shoe group was not statistically different than the proportion of fall events in the
soft soled shoe group (X 2 = 0.440, P = 0.51). In addition, no statistically significant differences
were observed between shoe groups for slip distance or average slip velocity (Table 1).
Table 1. Slip characteristics between groups. Mean (SD)
Hard Shoe Group Soft Shoe Group P value
Walking velocity (m/sec) 1.9 (0.2) 1.9 (0.2) 0.10
Slip distance (cm) 39.9 (28.7) 40.8 (30.9) 0.92
Slip velocity (cm/sec) 187.5 (98.1) 203.2 (109.4) 0.64
Table 2. Fall proportions between groups
Fall Recovery Total
Hard Shoe Group 8 (40%) 12 (60%) 20
Soft Shoe Group 6 (30%) 14 (70%) 20
Discussion
The results of this study demonstrate that the probability of a slip-induced fall was not
influenced by footwear sole hardness. In particular, no difference in the proportion of fall
events between two shoe groups was observed. In addition, slip parameters thought to
influence fall potential (i.e., slip distance and velocity) did not differ between shoe groups.
These findings do not support the premise that persons wearing harder soled shoes are at
greater risk for a fall once a slip is initiated. It is likely that recovery from a slip event is more
related to one’s ability to generate an effective response strategy.
References
[1] Courtney TK, Sorock GS, Manning DP, Collins JW, Holbein-Jenny M. (2001), Ergonomics, 44, 1118-1137.
[2] Brady RA, Pavol MJ, Owings TM, Grabiner MD. (2000), Journal of Biomechanics, 33, 803-808.
[3] You JY, Chou YL, Lin CJ, Su FC. (2001), Clinical Biomechanics, 16, 167-173.
[4] Lockhart TE, Kim S. (2006), Gait & Posture, in press.
[5] Cham R, Redfern MS. (2001), Journal of Biomechanics, 34, 1439-1445.
[6] Redfern MS, Bidanda B. (1994), Ergonomics, 37, 511-524.
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