Attention readers: I have published a significantly revised and updated article on midpoint Achilles tendonitis. I strongly recommend you read that instead! The information below is incomplete and out of date! Click here to go to the updated Achilles tendonitis article.
Note: if you are looking for information on insertional Achilles tendonitis, see this article
We're shifting gears a bit today. As high school and college cross country seasons approach, lots of runners are hitting their peak mileage right about now. At the same time, there's a lot of runners who wish they could be out there hitting the road every day, but are sidelined by injury. This will the the first post in a series on injuries: their cause, prevention, and treatment. In the past 10-20 years, there have been some very important changes in the way the medical community approaches and treats many common running injuries. In a few cases, highly effective treatments have been discovered that were not known even a decade or two ago. Unfortunately, many physicians and physical therapists don't stay on top of the injury research that's being published in several of the major medical journals, so the clinical implementation of these scientifically proven treatments is lagging. At the same time, many treatments that enjoy wide acceptance have not withstood a scientifically rigorous examination. While few are harmful, wasting time on ineffective treatments is something neither the patient nor the doctor wants. At the same time, I realize that treatment based solely on scientifically proven methods is often limited. I've also amassed a fairly large bag of "tricks" either through experimentation or advice from fellow runners. In truth, it's usually a combination of "tricks" and "treatment" that get you healthy and running again. I'll do my best to keep it clear what is scientifically rigorous and what is hocus-pocus-magic. This is quite a large undertaking, so (much to your delight, I'm sure) I'm going to break with my usual long-winded posts and break this series up in to smaller and more numerous posts, each on a specific injury and its causes, prevention, and treatment. Today's topic: Achilles tendonitis.
Introduction and Background
Injuries to the Achilles tendon are often cited as one of the "big five" most common running injuries (the others being plantar fasciitis, patellofemoral pain syndrome (runner's knee), medial tibial stress syndrome (shin splints), and iliotibial band syndrome). Whether to label Achilles injuries as "tendonitis" is controversial. The suffix -itis implies the main problem is inflammation, as is the case in conditions like appendicitis, gingavitis, etc. But Achilles tendon issues often present without any signs of cellular inflammation, especially in chronic cases. Some podiatrists prefer the label "tendonosis," which implies a more general dysfunction in the Achilles. Some even differentiate between tendonitis and tendonosis when diagnosing Achilles tendon injuries. Regardless, "tendonitis" is the most common term, and it's the term I'll be using in this post. However, it is important to remember that the root problem behind Achilles injuries is not inflammation--it is real, physical damage to the fibers of the tendon.
Before we delve into Achilles tendonitis, I need to give a quick primer on concentric and eccentric muscle contractions. Concentric contractions are simple. It's when the joint movement is in the same direction as the muscle's contraction. Using your biceps to curl a dumbbell up towards your shoulders is a concentric contraction. In contrast, an eccentric contraction is when a muscle is working to oppose the motion of a joint. Slowly lowering the dumbbell you've curled up to your shoulder is an eccentric motion. If you were to completely relax your biceps, the weight would quickly slam down. Your biceps work eccentrically to slow down the motion. Most "down" motions are eccentric contractions working to oppose gravity: the down phase of a pushup, lowering a barbell down while doing a bench press, and the down phase of a squat all involve eccentric muscle contractions. These contractions are stressful on muscles and are responsible for most injuries and muscle soreness--it's why running down a long hill several times will often make your quads more sore than if you'd ran up it.
The Achilles tendon is the biggest and strongest of all the tendons in the body. It connects the gastrocnemius and soleus muscles to the calcaneus, or heel bone, and allows them to perform their main task: plantar flexing the foot. Its role in running is essential--it allows the calf muscles (the gastrocnemius and soleus) to elastically store energy via the stretch-shortening cycle, which is released upon toe-off. The tendon itself also stores energy by functioning as a very stiff spring. And I do mean very stiff--upon loading with 120 pounds of force, it only lengthens by a few millimeters. In fact, its stiffness tops that of suspension springs in high-end sports cars--it would take over 900 pounds of force to stretch your Achilles an inch!
The Achilles tendon connects the calf muscles--both the gastrocnemius and the soleus--to the heel. Some doctors and researchers refer to both muscles as one unit: the triceps surae