Sports Shoe and Shoe Guidelines

In addition to a good fit, the following factors are of particular importance to the Achilles tendon:

• Heel Cushioning and Heel Height. As with most things, moderation is important. Too little or too much heel cushioning is bad for the Achilles tendon.  The same is true for heel height. The heel of most running shoes is slightly cushioned and slightly elevated, which is fine. 
  
  Not Too Little. Racing flats, heelless spikes, worn out shoes, moccasins with no cushioning, heel heights lower than 1/2" - 5/8" (12-15 mm), and shoes with cushioning that is too soft are bad extremes on the no cushioning, no height side. Cushioning is too soft if the heel sinks lower than the front of the foot. Too little cushioning and heel height overly strains and stretches the Achilles tendon.
  
  
  
  Not Too Much. The greater a shoe’s cushioning and heel height, the less stretching the Achilles tendon does with each stride and the smaller the calf muscles’ range of motion. Less stretching and a smaller range of motion can be temporarily helpful when recovering from an injury, but permanent use of added cushioning and heel height reduces the length of the Achilles tendon, which can lead to later injury. Too short a range of motion promotes calf muscle shortening, disproportionate weakness in the parts of the calf muscle that are not stretched with each step, and possibly a general weakening of the calf muscle. High heels are the worst.
  
  
• Anti-Pronation (Majority) Anti-pronation shoes and running shoes prevent excessive pronation during walking and running, decreasing the amount of extra muscle activity around the subtalar joint (just below the ankle), ankle, and Achilles tendon. Pronation is the rotation of the foot inward and downward with each step or stride, putting weight on the inside of the foot. Pronation is a normal part of each step or stride, excessive pronation is the potential problem.
  
  Excessive pronation is also known as hyper mobile feet. Anti-pronation is also known as motion control. Anti-pronation shoes have firm midsoles, board lasting, rigid heel counters, and non-flared heels. The midsole of a shoe extends from the tip of the toe to the back of the heel and from side to side, it is between the outersole (bottom of the shoe – the part that touches the ground) and the slip or board lasting (the part of the shoe that your foot stands on).
  
  If the upper part of a running shoe is connected directly to the midsole it is called slip lasting, if the upper part is connected to an additional layer of material on top of the midsole it is called board lasting. Board lasting provides greater anti-pronation than slip lasting. The heel counter is the plastic piece of a shoe in back of and to either side of the heel. It is designed to prevent excessive motion of the subtalar joint (the joint just below the ankle).
  
  Heel flare is the difference between the width and back of the bottom of the outersole beneath the heel and the width and back of the top of the midsole beneath the heel. If the bottom is smaller than the top it is a negative flair and is more anti-pronation. The firmness of a heel counter can be tested by squeezing it between two fingers, the more difficult it is to squeeze, the firmer the heel counter, and the more effective its anti-pronation.
  
  The overall anti-pronation quality of a shoe’s midsole, lasting, and heel counter can be tested by holding a shoe with one hand at the widest point in the shoe and one hand at the heel and then twisting the shoe as though the ankle were leaning inward. The more difficult it is to twist, the more anti-pronation the shoe.
  
  
• Anti-Pronation (Exceptions) For most people who over pronate, motion control shoes are appropriate, but they are not appropriate for everyone. Check with a physician to be certain
  • Excessive pronation can lead to Achilles tendon injuries, but the reverse can also be true: tight or short Achilles tendons can cause over pronation. If the pronation is caused by something other than tight or short Achilles tendons, then a motion control shoe will probably be helpful. If Achilles tendon tightness is causing the pronation, then motion control shoes are probably not appropriate. 
  • Motion control shoes are also inappropriate for people who under pronate. 
    
    
• Flexible Sole at the Forefoot (not too stiff). Although midsoles should be firm, they should not be so firm that the shoes do not bend comfortably at the forefoot with each stride. If the shoe is too stiff the heel may slip a little out of the heel counter, negating some of the shoe’s anti-pronation qualities.
  
  
• Correct Arch Support.  Flat feet (feet with low arches) and high arched feet are each associated with a higher likelihood of Achilles tendon injuries. Both types of feet benefit from adequate arch support, either built into the shoe or inserted

Orthotic Guidelines

If the shoe guidelines have not helped enough, consult with a physician about orthotics. Orthotics should be full length (rather than ending at the arch), and made of flexible (rather than hard material). Full length is important because 70% of the time that a foot is on the ground during a stride, the weight is on the forefoot. People with Achilles tendon concerns should discuss orthotic features relating to: cushioning, heel height, degree of arch support, and anti-pronation with their physician. Working with a professional is important because orthotics often require expert readjustment before they are completely effective.