Effects of shoe inserts and heel height on foot pressure, impact force, and perceived comfort during walking
Introduction
Surveys of shoe choice have shown that 37–69% of women wear high-heeled shoes on a daily basis (The Gallup Organization, 1986; Frey et al., 1993). Wearing high-heeled shoes modifies gait kinematics and kinetics (Esenyel et al., 2003; Snow et al., 1992; Mandato and Nester, 1999; Voloshin and Loy, 1994; Kerrigan et al., 1998). Previous studies have demonstrated that walking in high-heeled shoes alters lower-extremity joint function (Esenyel et al., 2003), raises the peak pressure in the forefoot (Snow et al., 1992; Mandato and Nester, 1999), and shifts peak pressures from the third, fourth and fifth metatarsal heads to the first and second (Soames and Clark, 1985; Snow et al., 1992; Eisenhardt et al., 1996). In addition, wearing high-heeled shoes for walking generates a force spike at the initial ground contact (i.e., impact force) and the force is then transmitted up to the skeleton as a “shock wave” (Voloshin and Loy, 1994). This shock wave appeared to damage soft tissues, which may result in leg and back-pain complaints (Wosk and Voloshin, 1981; Voloshin and Wosk, 1982) and eventually lead to degenerative joint disorders (Kerrigan et al., 1998). Despite concerns regarding their adverse effects on human musculoskeletal system, employment criteria and/or fashion customs encouraged the continuous use of high-heeled shoes. Studying the impact of high heels on kinetic changes and perceived discomfort provide a basis for designs that minimize adverse effects.
Engineering efforts to reduce foot loading caused by peak pressure and impact force, and to improve shoe comfort, involved designing shoe inserts with different shapes (Light et al., 1980; Chen et al., 1994; Hodge et al., 1999; Lee et al., 2004). The use of inserts is effective in redistributing the pressure beneath the foot and absorbing energy in terms of reducing impact force. Various inert designs demonstrate different kinetic modification during gait. For example, a heel pad is effective in reducing heel pressure and the magnitude of the heelstrike impact (Light et al., 1980; Jorgensen and Ekstrand, 1988). An arch support was designed to resist depression of the foot arch during weight bearing through skeletal support, thereby decreasing tension in the plantar aponeurosis (Kogler et al., 1996). A metatarsal pad has been found to reduce forefoot pressure and transfer weight bearing to the longitudinal and metatarsal arches (Lee et al., 2004). Finally, a total contact insert (TCI) provided pressure relief in the heel and forefoot regions (Lord and Hosein, 1994; Chen et al., 2003). These studies, however, focused on inserts in flat or running shoes. No study, insofar as we have examined, attempted to identify insert effectiveness in high heels.
The purpose of this study was to determine whether increasing heel height and the use of various types of shoe inserts would result in changes in foot pressure distribution, impact force, and perceived comfort during walking. The types of shoe inserts used in the current study included heel cup, arch support, metatarsal pad, and TCI.
Section snippets
Participants and materials
Ten healthy females volunteered for this study. The average age of the subjects was 23 years (range 20–28), average weight was 50 kg (range 47–53), and average height was 160 cm (range 156–162). None of the subjects had suffered an injury to the lower extremity during the preceding year. Four subjects had worn high-heeled shoes two-to-five times per week for at least 1 year. The other six had relatively limited experience. Written consent was obtained from each subject before commencement of the
Results
The assumption of homogeneity is examined and not violated. Fig. 5 illustrates the comparisons of peak pressures in different foot regions and Table 1 lists the comparisons of impact forces for each test condition. ANOVA results indicated a significant heel height effect on peak pressure of the medial forefoot (; ), the heel (; ), and the midfoot (; ) regions, and impact force (; ). Post hoc comparisons using Tukey's HSD
Discussion
The results supported our hypotheses that increasing heel height would change pressure distribution under the plantar surface and increased impact force and perceived discomfort during walking. All inserts were effective in altering pressure distribution. Both heel cup and TCI effectively attenuated impact force. All inserts except for the metatarsal pad were effective in reducing subjects’ perceived discomfort.
The results showed that increasing heel height shifted pressure from the heel and
Conclusion
Increasing heel height increases medial forefoot pressure, impact force, and perceived discomfort during walking. A custom-made insert with a heel-cup or an arch-support mechanism for high-heeled shoes would be effective for reductions of heel pressure and impact force or medial forefoot pressure, and for an improvement in footwear comfort. In particular, a TCI, combined with a heel-cup and an arch-support mechanism, could reduce heel pressure by 25% and medial forefoot pressure by 24%,
Acknowledgements
This study was supported by a grant from the National Science Council, ROC (Project No. NSC-92-2213-E-011-041). The authors also wish to acknowledge Mr. Liu Wen-Long, an orthotic technician from the Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, for his assistance with the fabrication of the custom-made inserts.
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