Tendon injuries in runners are all different, yet may all have one defining similarity. It’s common knowledge amongst orthopedic professionals that eccentric activity increases the load to a tendon. For those who are unaware, our muscles can produce force as they shorten (raising a weight overhead) or as they lengthening (lowering the arm). Both activities fire the same muscle groups, but each motion causes specific muscles to either shorten or lengthen.
Common tendon injuries occur to the Achilles, patellar, and high hamstrings tendons.
Eccentric activity is always a lengthening contraction of a muscle and increases tendon tensile load. Injury can result to the tendon for a few reasons. For some, not enough rest or too much too soon can result decreased tolerance to load. For others, weakness or range of motion restrictions cause excessive eccentric activity and result in loads that are above tissue threshold. Some injuries are a result from your footwear. A simple change of shoes from high to low drop can cause excessive Achilles tendon load through midstance. If a single or repetitive load is applied above tissue threshold an injury results. At a tissue level we know what causes an overused tendon. The trick is to identify the source of excessive eccentric load and fix it.
The gait cycle revolves around two phases: deceleration and acceleration. Both are critical and each can cause various injuries. Deceleration occurs on the front half of the gait cycle. With every foot strike our body is required to control the interaction the ground. Instantaneous to foot contact our body loads downward, decelerating to the pavement. Our muscles lengthen eccentrically to not only shock absorb, but to also load for our acceleration phase–push off. For the sake of this article we are evaluating the front half of the gait cycle–the loading or deceleration phase. This phase is dominated by eccentric-rotational movement.
If we can’t control our spin to earth there are significant downstream costs.
If we can’t control our spin to earth there are significant downstream costs. Our joints, muscles, and tendons will be yanked through excessive, damaging movement as our foot progresses from initial contact to push off. A weak core, hip, knee, and ankle are all to blame, but it’s always nice to have a jumping off point. I’ll typically throw our proximal muscles under the bus and scold the core and hips. It’s not uncommon to see an Achilles Tendinitis patient develop symptoms due to their inability to control their collision with the ground. An uncontrolled landing literally wrings the Achilles like a rag. A weak chain of muscles allows for excessive eccentric movement. Remember, eccentric movement only happens in the front half of our stride. Also recall that eccentric movements increases tendon load.
For those suffering from tendon issues, begin pointing your finger at the front end of your stride and correlate with poor control during loading. It doesn’t matter if your pain is at the Achilles, knee, or in the butt (or for our train wrecks all three). Improving your ability to meet the demands of initial contact through midstance is crucial. There’s no substitute for rest, either. Tendons are notoriously slow healing and will likely require some finagling (yes, finagling) of your program. Unlike muscles, tendons are non-contractile tissue. They serve as anchors for your muscle to contract and produce force. Since muscles shorten and lengthen in a ratcheting fashion they require oxygen. Oxygen is transported via blood. My point? Blood is a good thing, that is, if it stays in your body. Your muscles are deeply routed streams and neighboring tributaries of blood vessels that transport blood. With increased vascularity comes faster healing. Tendons don’t contract though.. they’re just anchors–anchors with poor blood flow. Tendons get enough blood to survive and that’s it. Enter your frustration with slower healing.
Take a look at this video demonstrating how our body loads eccentrically at initial contact. With poor control comes increased load to joints, muscles, and tendons.
If you’re suffering from a tendinitis or tendinosis you’ll need to look to the chains of muscles responsible for controlling landing forces. Start with proximal muscles that control for movement. Core and hip strengthening are always a great place to start and remember, BE PATIENT!