WHAT CAUSES ACHILLES TENDINOPATHY?
Defined as an “overuse” injury due to stress caused by an accumulation of forces.
- Very common injury, especially in runners–accounts for about 10% of running injuries.
- Most common in male recreational runners aged 35-45
Believed causes of acute achilles tendinitis include:
- Inflexibility of achilles tendon
- Insufficient gastrocnemius strength or flexibility
- functional over-pronation, producing a whipping action on the achilles tendon as the heel goes from varus on heel strike, to valgus in midstance.
- Number of years running, training pace, stretching habits.
- Recent change in shoe wear, and poor running shoes.
- Recent increase in training, especially if it includes hill running.
- Eccentric loading of a fatigued muscle-tendon unit from over-training, or running on uneven terrain, or hard surfaces.
Excessive Pronation — an upward rotation of the rear foot during the stance phase of the running cycle, which may bow or twist the tendon. The hypothesis is that thousands of repeated foot strikes involving excess pronation can cause damage to the achilles.
Insufficient ankle muscle strength–specifically the calves and tibialis anterior, and primarily eccentric strength. The tendon is unable to cope with the repeated eccentric contractions which the calf muscles must perform as the foot makes contact with the ground. The repetitive high forces produced may cause excessive stress to the tendon. This is an important factor. If the plantar flexors and anterior tibialis are weak, risk of injury increases. Eccentric strength tends to be lacking, thus resulting in poor control of dorsiflexion and pronation during the foot- down and cushioning phases of running. When these movements are not controlled, partcularly the velocity of pronation, then this can cause an excessive whipping of the achilles tendon as the foot strikes the ground, and the knee rolls forward over the foot.
Dysfunctional hips—If the gluteus maximus and the hip abductors don’t control the hip sufficiently during the cushioning phase, then the hip may drop laterally on the swing-leg side, or the pelvis could tilt backwards. Either of these would result in a greater inward rotation force on the knee, which would in turn cause a greater inward rotation of the tibia, which then inwardly rotates the ankle, thus increasing the degree of velocity of pronation. This is a perfect example of how the whole leg-chain is dependent on all the links working correctly. If the hips lack stability, this will influence other forces down the chain negatively against the achilles tendon. And what stabilizes the hips? Yep, it’s the gluteals, which are already under-active in over 80% of the population (see “Poor pelvic alignment”)
It’s important to understand that achilles tendinopathy is often seen in patients with sedentary lifestyles, thus supporting my argument that muscular imbalances and anatomical dysfunctions play the biggest role in causing the affliction. Having said that, it’s important to avoid over-training, especially if you are anatomically predisposed towards injury, by using the principle of gradual progression, with only a 5-10% increase in weekly mileage for runners, coupled with adequate recovery time. However, the anatomical faults MUST be addressed.
I would advise avoiding surgery if possible, as the success rate is only about 66%, and progressive calcaneal bone loss has been found a year after surgery. Perhaps a better alternative is heavy eccentric calf muscle training, in which one study found 82% of patients achieved full recovery to their previous activity level.
Some researchers found that the safest achilles tendons were longer and more slender than average. Short/thick tendons aren’t as economical. Kenyan runners are prime examples of long/slim achilles tendons.
In closing, I strongly suggest the importance of ankle mobility. Work on plenty of calf flexibility, and attempt to correct any hip mobility issues, including, of course, gluteal function.
Shane Shiels
