Dimensiones integrantes de la imagen de destino turístico

As well as the height of the heel, footwear in the “high heeled” genus can be further classified dependent upon the shape and style of the material added below the foot heel, or the design style or material of the upper. The heel categories include: wedge, stiletto, block, tapered, blade etc. (Figure 4 and Figure 5), whilst upper types include: sandals, open toed, close toed, with and with out straps, with and with out arch support provided by the upper in the midfoot (Figure 6). Each of these variations has the potential to affect the foot biomechanics of the wearer. For example, a wedge heel and stiletto heel each have different contact areas with the floor and the foot. This could affect load transmission to the foot but also the stability of the wearer. Uppers with or without material to brace the toes or mid foot will provide different levels of constraint on movement of the foot inside the shoe. Thus, understanding upper style and properties as well as heel height and heel style are all relevant to foot biomechanics, foot health and comfort.

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Figure 4: Comparison of the most common heel shapes.

Figure 5: Types of high heel.

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Figure 6: Types of Upper Design

(Top left: sandal or strappy, top middle: open toed pump, top right: closed toed pump, bottom left: ankle strap, open toes, bottom centre: ankle strap closed toed pump, and bottom right: closed-toe

pump with arch support)

Besides heel height, the two aspects of the heel that are most likely to affect the foot are the contact area between the sole of the heel and the ground, and the position and shape the foot is manipulated into by the shoe. Some researchers have also observed that ground contact area under the heel and forefoot can affect plantar pressure [23, 43]. However, few studies of “high heeled” footwear detail or even mention these features when describing the footwear they investigated. The failure to adequately and precisely specify the footwear tested is a significant barrier to understanding the relationship between footwear design and effects on foot biomechanics. Without detailed characterisation of the footwear geometry and materials, as well as independent control of these features across multiple experimental conditions, it is impossible to know what aspect

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of the footwear design is responsible for any observed effects on feet or gait (e.g. changes in plantar pressure). Likewise, providing information on the sagittal plane angle at which the heel of the foot is raised from the ground is not common.

Not defining the sagittal plane angle seems an important omission in much of the footwear literature given that Hicks [31] proposed that the onset of the windlass might occur when the hallux is extended by 10 degrees, not when the heel or toe were raised a predefined height above the forefoot (whilst the windlass relates to the plantar fascia, the concept is transferable to the multiple long and short muscles inserting into the plantar surface of the toes). One explanation for this omission is the difficulty in defining the shape of the footbed posterior to the last contact point, due to the many components that are combined to create the final shape. Footwear lasts have a number of features affecting midfoot orientation including: last depth, heel seat length, and heel seat angle, but the footbed can also have characteristics which will affect the final position of the rearfoot.

To further add to the complexity in defining and investigating high heeled footwear in a transparent way it is important to acknowledge that heel wedge angle [36, 70], upper design and materials [71], heel seat length [36], heel cup [72], arch support[72], last flare

[73] and insoles [72] might also affect foot biomechanics and gait (these features are explained in more detail later in this chapter). Furthermore, many other shoe features, including heel flare [74] and toe spring angle [75], affect wearers walking in non-high heeled footwear, and it is reasonable to assume they will also affect wearers of high heels. Thus, all features of the footwear should be defined when investigating footwear effects on gait so that the footwear being tested is fully characterised and understood. However, with the

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large number of possible variables and the possibility that future investigations discover a new footwear feature to be important, to provide a truly definitive list of features may not be possible. Thus an investigator should strive to report as many footwear features as possible and all remaining footwear features should be kept identical to ensure any confounding effects are minimised.

In summary, this thesis is concerned with the effects of heel height and related footwear design features on the foot. Heel height is not consistently defined nor reported in the prior literature. On the assumption that the effect of shoe heel height on foot behaviour is of interest, “effective heel height” seems the most appropriate definition to adopt. The effective heel height is the difference in height between the plantar surface of the forefoot and the plantar surface of the heel. What constitutes a “high” heel has likewise not been well defined, often because of poor reporting of the shoes being investigated. Since previous research has recommended that shoes over 5.06 cm should not be worn to reduce the risk of injury [27], for the purpose of this thesis a high heeled shoe will be considered as a shoe which has an effective heel height of 5cm or more, until such time that results suggest otherwise.