Repetitive/overuse motion represents the most common form of injury associated with running. Although the repetitious one-foot-in-front-of-the-other nature of running is mostly to blame, several factors contribute greatly toward making these types of injuries so commonplace with runners. These factors include running surfaces that are too hard, poor fitting shoes, shoes that are too old or worn out, increasing mileage too quickly and reduced shock absorption due to poor lower extremity biomechanics.
The most damaging force placed on a runner is the “shock” caused by the heel striking the ground. In fact, many of the joints of the lower extremities play an important role in reducing the “shock” experienced with running. Therefore, these joints need to be firm, but springy so that they can absorb the shock rather than transfer it further up the body. The most important shock-absorbing joint complex is the foot. The many bones and joints of the foot must work in concert to prevent “jarring” of the body. Excessive “jarring” related to stiff, inflexible joints of the feet often contribute to foot pain (plantar fascitis), and knee problems, as well as hip and low back pain.
When the joints of the feet fail to absorb the shock of running, the muscles of the legs, hips, pelvis and low back are often forced to work overtime to dampen these damaging forces. The increased effort of these muscles can cause chronic muscle damage over time leading to pain and reductions in performance.
Repetitive “rubbing” of sensitive soft-tissues or
chronic muscle tightness can initiate an injury cascade that will eventually lead to significant dysfunction and pain.
Both of these situations deprive the soft-tissues of much needed oxygen due to a decrease in full muscle contraction and complete relaxation. This reduces the “pumping” action that normally occurs within healthy muscle tissue. A decrease in tissue oxygenation triggers fibroblastic activity – the primary mechanism involved in the formation of scar tissue. Unfortunately, as more fibrous tissue is created, muscle oxygenation, flexibility and strength are further reduced. This cycle continues until both structure and function have been degraded to the point that symptoms occur – usually stiffness, pain or weakness. In other words, repetitive motion injuries can develop over months or years before the first symptom is ever experienced!
As the condition progresses, the “stickiness” of the muscles and tendons can extend into the spaces between the soft tissues forcing them to become “stuck” to one another. When this happens around a nerve it can cause an irritation of the nerve known to doctors as a peripheral nerve entrapment. This can lead to numbness, tingling or burning the legs and feet.