Body weight Carrying excess weight puts an obvious strain on the feet, especially the plantar fascia because of its function as a shock absorber, but what is considered excess weight? The standard measure of healthy weight in the medical community is the body mass index, or BMI, which is calculated as weight (kg)/height² (m²). According to the World Health Organization, a healthy BMI is between 18 and 24, a BMI between 25 and 29 is overweight, and a BMI greater than 30 is obese (World Health Organization, 2024). Studies show that obese people are more likely to develop plantar fasciitis, due to the additional strain placed on the plantar fascia from both the excess weight bearing down on the feet and the abnormal weight distribution on the sole of the foot. Excess weight and obesity can also cause deviations to a normal gait, in which the weight of the body is consistently applied to the sole of the foot in an unbalanced way, affecting the normal function of the plantar fascia. Pregnant women also present with acute episodes of plantar fasciitis in late pregnancy because of the excess strain an awkward distribution of bodyweight can put on the feet. Flat feet “Flat feet” is the common term used to describe feet with little to no longitudinal arch. Flat feet can be caused by genetics, making them a condition since birth, or they can occur over time as a degenerative process. Flat feet can also occur as the result of an injury or as a secondary effect of a musculoskeletal disease like muscular dystrophy. Whatever the cause, the body’s natural support system for the sole of the foot is compromised in the case of flat feet, and those who have them can be prone to developing plantar fasciitis. The rubber band-like tension of normal plantar fascia is very decreased or absent in the case of flat feet. The windlass mechanism described in Section 1 becomes unachievable in flat feet. A study published by the National Library of Medicine in 2018 compared the plantar fascia of 52 young adult participants, half of them having normal feet and the other half having flat feet. We can assume, because of the age of the participants, that the ones with flat feet were born that way, and it was not a condition acquired by age or injury. The density of the plantar fascia was measured by ultrasound, and it was noted that the participants with flat feet also had significantly thicker plantar fascia than those with normal feet. The participants with flat feet also demonstrated significantly less dorsiflexion of the ankle in range-of-motion tests (Park et al., 2018). We already learned previously that inhibited dorsiflexion is a primary cause of plantar fasciitis. High arches Though not as thoroughly researched as the incidence of flat feet with plantar fasciitis, some studies have found that having very high arches can also be a precursor to developing plantar fasciitis. Flat feet and high arches are both structural abnormalities of the feet that can affect the normal function of the plantar fascia. In the case of high arches, there is too much rubber band-like tension in the plantar fascia. Additionally, it can be difficult to find footwear that provides adequate support for high arches, which can cause strain and inflammation (see the following activity). How high are your arches? For this exercise, you will use your own feet to understand the mechanics and structure of the arch of the foot. Make a wet-blot print of your foot to determine the height of your arches. For this exercise, you will need a few blank sheets of printer paper and a washcloth or hand towel large enough to cover the entire sole of your foot. Wet and wring out the washcloth or towel, and place it down on a hard surface
floor. Place one of the sheets of paper next to it. Press your bare foot into the wet washcloth, lift it, then press it onto the sheet of paper to make a blot of your footprint. (If you do not get a good blot footprint, you may have to make the washcloth wetter). Look at the blot footprint that your foot made and notice the width of the blot where your arch would be. How does your blot print compare to the diagram (Figure 3)? Is it very narrow, indicating a high arch that made little to no contact with the floor, or is it very wide, indicating a flatter foot? Make blot prints of both feet and compare them to each other. Are they similar, or different? If they are different, has there been an injury to one of your feet or ankles, and how does the blot print of that foot look different? Knowing what kind of arches you have will help you determine what kind of support you need in your footwear to keep your plantar fascia in a healthy state. Try this exercise again with other members of your household to compare footprints. Figure 3
Poor support and footwear Footwear choices can also have a significant effect on the health of the plantar fascia, especially if there is not consistent and adequate support for the health of the feet. Most physicians caution patients who have suffered from episodes of plantar fasciitis from ever going barefoot, even indoors at home, because of the lack of support and the way the foot can pronate when the arch is completely unsupported. Shoes that offer very little arch support may also cause similar problems, like the popular ballet flats or flip-flops, especially if they are worn while standing or walking for long periods of time. As mentioned previously, runners can experience bouts of plantar fasciitis when their running shoes are worn out. “To prevent heel pain, replace old shoes with excessive or uneven wear on soles and heels. Replace athletic shoes every 350 to 500 miles. To test the support of the heel, press the sides of the sneaker together and make sure they do not collapse” (Comprehensive Foot Centers, 2017). Wearing high-heeled shoes, as is the expectation for many professional women, can also be problematic because of the tightness this can create in the muscles of the calf. When the heel of the foot is excessively elevated, the gastrocnemius and soleus are engaged because the primary function of these muscles is to move the ankle into plantar flexion. When high heels are worn every day, the muscles of the calf can become chronically hypertonic, which can dramatically limit the ability of the ankle to move into dorsiflexion. As we learned previously, limited dorsiflexion is one of the primary causes of plantar fasciitis. For jobs or other activities that require standing for long periods of time, shoes that provide adequate support
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