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Addition/correction to book

Posted by Scott R on 1/28/01 at 18:20 (037604)

Calf Muscle Flexibility, Center of Gravity, and Effective Shoe Length

The next two paragraphs are difficult to understand, but not nearly as difficult as they were to write.

When people are walking, they are basically 'tipping over' the front of the foot of their trailing leg with each step. The other foot swings forward to catch them falling forward as they 'tip over'. Objects with a low center of gravity and/or a wide support base are well known to be harder to tip over. If a person is harder to 'tip over' as a result of having a long foot and/or a low center of gravity, then the increased amount of force from momentum that the body has to generate during walking in order to tip itself over translates into more tension force in the plantar fascia.

It is well known that when the center of gravity of an object is closer to the edge of its support base, then the object is much easier to tip over than if the center of gravity were above the center of the support base. In fact, if the center of gravity passes outside of the support base, the object tips over on its on without an outside force or momentum being necessary. Walking causes the hips (the approximate center of gravity) to travel forward to be over the front of the foot to make it easier to tip over. If the center of gravity stayed above the center of the foot, it would require more momentum to force the body to tip over the front of the foot. That force translates into more tension in the plantar fascia. Since the knees do not bend forward, the only way for the hips to move forward to be over the front of the foot (before tip over occurs) is for the foot to bend back at the ankle. In other words, a lack of flexibility in the calf muscles will prevent the ankle from bending sufficiently, which will prevent the hips from travelling far enough forward during walking to allow an easy tip over, which will require more momentum to force the tip over, which will translate into more tension in the plantar fascia. I know the last step in that chain of reasoning requires faith, but that's the best I can do after 4 years of trying to explain it.

A short foot, a high center of gravity, and good flexibility in the calf muscles are interconnected to reduce the tension in the fascia when walking. An improvement in one will compensate for deficiencies in the others. Incidentally but importantly, tension in the Achilles tendon is likewise increased for the same reasons. In the discussion above, the Achilles tendon and plantar fascia are two links in a chain that extends from the ball of the foot to the hips.

Shoes that do not bend under the ball of the foot as easily as toes do naturally are effectively increasing the length of the foot. As explained above, this increases tension in the plantar fascia.

If women gain weight in their thighs and hips and men gain weight in their chest and belly, then a woman's lowered center of gravity could help explain why heavy women are 6 times more likely than heavy men to get heel pain. The observation that heavy women are so much more prone to heel pain cannot be explained merely by women's shoes because thin women are only 2 or 3 times as likely as thin men to get heel pain, and they are probably more likely than heavy women to wear awful shoes. But the combination of women's shoes and being overweight could have a combined negative effect that exceeds some threshold above which there is a cascade of additional cases of heel pain (which would make my center-of-gravity explanation unnecessary).

Heel lifts help the foot tip over, so that they reduce tension in the fascia in those that have limited flexibility in the calf muscles. But I view them as only a temporary emergency aide. A dependency on them can result if the calf muscles lose their flexibility from not being stretched with each step. Switching from high heels to barefeet at the end of the day can likewise be very harmful.

Fixing Stiff Shoes

As described in the previous section, I believe shoes that are stiff in the ball of the foot and prevent the toes from bending back easily and naturally are an important cause of many cases of heel pain, plantar fasciitis, heel spurs, and Achilles tendonitis. I've used 3 methods to deal with stiff shoes. The first was a heel lift to help me 'tip over' the front of the shoe when walking, but heel lifts have two drawbacks that are described in other sections. The second was to use a knife to cut a series of slits across the bottom of my running shoes and boots (across the width of the shoe, not the length). The slits are nearly through the entire sole (risking water leakage) and spaced 1/4' apart. There are 10 slits in each of my tennis shoes and 30 in my boots. This was a Life-Saverô. It was very difficult and dangerous to do even with a utility knife. Both pairs now bend back easily, but still not as easily as my toes. I have also used a concrete block to keep the toes of the shoes bent back overnight to improve their flexibility. A string, rope, or thick tape can also be used to keep shoes bent back overnight.

Re: Addition/correction to book

Julie on 1/29/01 at 03:05 (037626)

Bravo, Scott. I need to read this several more times to take it in thoroughly, but it strikes me as a masterly and illuminating explanation. And it's very clear. Thank you.

Julie

Re: Addition/correction to book

Julie on 1/29/01 at 03:05 (037626)

Bravo, Scott. I need to read this several more times to take it in thoroughly, but it strikes me as a masterly and illuminating explanation. And it's very clear. Thank you.

Julie