Shin Splints – The Distance Runner’s Epidemic
By Rick Morris
It’s the words that I dread and yet have become very accustomed to hearing – Coach; I have a pain in my lower leg! I dread hearing those words because shin splints, an injury to the muscles, connective tissues, fascia or bones of your lower leg are a potentially chronic injury that is, for the most part an avoidable problem. Shin splints have nearly reached epidemic proportions among distance runners.
Some researchers have estimated that as many as one in five of today’s distance runners have various degrees of shin splint injuries. There are few runners that have not felt that unwelcome ache on the front of their shins. In fact, most studies agree that from 6% to 16% of all injures reported by runners are shin splints. A recent study reported that shin splints are the most common cause of leg injuries to athletes of all sports.
Why have shin splints become so prevalent in modern runners? Why did runners in the past have fewer problems with shin splints? I believe the blame can be placed squarely on the shoulders of two fairly recent changes in the running world – over engineered running shoes and a lack of proper conditioning among distance runners.
What are Shin Splints?
Before we get into the causes of shin splints, it might be a good idea to clarify exactly what shin splints are and what they aren’t. In the past shin splints was a generic term used to refer to virtually any pain or injury in the lower leg. They were loosely organized into one of several categories that described the location of the injury. The categories were called anterior (front of leg), posterior (back of leg), medial (inside of leg), and lateral (outside of leg).
Most athletes and many coaches still use the term “shin splints” when describing lower leg injuries, but health professionals no longer use the term because it is too vague. Shin splints are now separated into 4 categories. The current categories are: medial tibial stress syndrome, tibial periostitis, anterior compartment syndrome, and stress fractures.
Medial Tibial Stress Syndrome
Medial tibial stress syndrome (MTSS) is the most common form of shin splints. Pain from this injury is located along the inner part of your lower leg. The posterior tibial muscle is located on the back of your lower leg bone. It wraps around the inner part of your ankle and attaches to the top of the arch of your foot.
A primary function of this muscle is to support and hold up the arch of your foot. Each stride you take places stress on the tendons and connective tissues of this muscle. The stress travels up the muscle to its origin on the back/inside of your lower leg. This inside area of the muscle and attachments are where the pain of this injury is felt.
Excessive pronation (rolling inward of the foot) is a major risk factor for MTSS. When your foot pronates, this muscle must work harder to hold up the arch of your foot. In addition to excessive pronation, other risk factors include: heel striking, high arches, running on your toes, overtraining, running on slanted surfaces and running in worn out shoes. Running on hard surfaces can also be a factor, but this is not a common cause of this injury. Running on very soft surfaces, such as grass or sand, can actually be more of a factor because of the potential increase in pronation.
There is a covering of the lower leg bone called the periosteum. The impact of your foot striking a very hard running surface can irritate the front of your shin bones. This irritation can be transferred to the periosteum which results in pain and inflammation. The pain from this form of shin splints is usually felt on the front of your shin bone, directly under the skin. It usually starts about 3 inches above the ankle and extends up the bone for 2 to 3 inches. The primary risk factors for this injury are running on hard surfaces such as concrete or running with heavy, high impact strides.
Anterior Compartment Syndrome
The muscles on the front of your lower leg are encased within a “compartment” made of membranous walls. As you exercise, these muscles can become enlarged as they swell with blood. The compartment resists this swelling and pressure builds up within the compartment. This restricts blood flow to the muscles, which results in pain. The pain is usually located on the front of the lower leg, just to the outside of the shin bone. The muscle usually involved in the tibialis anterior muscle, which is responsible for flexing or raising the front of your foot.
Risk factors include: overtraining, rapid increases in training volume, a small anterior compartment, worn shoes and running on hard surfaces. In addition, there are mechanical risk factors involved. Calf muscles that are too tight will cause the muscles on the front of your lower leg to work harder to flex your foot. These increases the stress put on them and increases the chance of suffering this injury. This added stress happens at two phases of your running stride.
The first is at toe off. Immediately after toe off, your foot flexes so that your toes will clear the ground during knee lift. The second is just before, during and just after foot contact. At this point, the anterior muscles are working to slow down and stop the downward motion of the front of your foot.
Runners that over stride or land heavily on their heels are especially vulnerable to this injury because the anterior muscles must work especially hard to stop the downward “slapping” motion of the front of the foot.
Stress fractures are small cracks or micro fractures in the lower leg bone. These fractures are caused by the repetitive low grade impacts of running and other activities such as dancing and aerobics. A couple of theories have surfaced to explain why these fractures occur.
- Overload Theory – When muscle contract they pull and put stress on the areas in which they connect to the bone. This stress may cause the bone to “bend” slightly with each impact. It is thought that this repeated bending and straightening may cause the cracks to appear.
- Fatigue Theory – As muscle fatigue during they become less efficient at supporting the bones, which is one of their functions. The decreased amount of support to the bones may be a cause of the stress fractures.
Pain from a stress fracture is usually localized to a small portion of the bone. This is opposed to other forms of shin splints which are more spread out. Diagnosis of a stress fracture must be confirmed with an X-Ray or a bone scan. If left untreated, a stress fracture can progress to a full fracture.
Causes of Shin Splints
As you have seen, each of the four types of shin splints carries their own causes and symptoms. But these are only symptoms. What is really causing the epidemic of shin splints? I mentioned earlier that I believe problem start with lack of conditioning and over protective running shoes. I developed that opinion though many years of coaching and running, but does the scientific community agree with me? There isn’t a lot of definitive information that points to a direct cause, but some recent studies back up the fact that lack of conditioning is a primary cause of MTSS.
The primary muscles involved in shin splints your ankle dorsi flexors, plantar flexors. The primary purpose of these muscles are to move your foot away from (plantar flex) your shin and towards your shin (dorsi flex). That is not their only duty. They get involved in lateral ankle motions, rotary ankle motions, foot stabilization and also in preventing excessive pronation.
A study done at the Geelong Foot Clinic in Victoria, Australia, looked at the conditioning or endurance of the plantar flexor muscles. The researchers found that “…athletes with MTSS have endurance deficits of the ankle joint plantar flexor muscles, Rehabilitation of athletes with MTSS should comprise training designed to enhance endurance of the lower limb musculature, including the ankle joint plantar flexors.”
How did this weakness of lower leg muscles come about in today’s distance runners? I think it is at least partially caused by the over marketed and over engineered modern running shoe. Today’s show manufacturers are constantly pushing the latest shoe that provides tons of cushioning and completely supports your foot. That sounds great except for one rather critical thing. The shoes are so supportive they are like a cast on your foot. As a result, the muscles in your lower leg no longer have a job to do. They don’t need to work as hard to stabilize your foot. They do less work during your running stride. So, your lower leg muscles get weaker and weaker. The result – a higher incidence of shin splints.
Reversing the Trend
So, how do you stop the shin splint epidemic? There is nothing you can do to complete prevent MTSS, but you certainly do something to reduce your chances of suffering from shin splints. If you strengthen your lower leg muscles and improve their endurance you have a great chance of eliminating this debilitating injury from your running life. How do you do that? Perform the lower leg strengthening exercises outlined below on a consistent basis and you will be on your way to eliminating this debilitating injury from your running life.
The Alphabet Drill
This is a simple but effective drill for strengthen all of your lower leg muscles. This is drill is simple to perform and can be done anywhere, even when at work. Simply sit in a chair or on a bench and with your foot held above the floor and your toes pointed out, trace all of the letters of the alphabet with your toes. This simple exercise will use nearly every muscle in your lower leg. Repeat this three times with each foot.
With your foot dorsi flexed (front of foot pulled up towards your shin) walk on your heels for about 50 meters. Keep your foot dorsi flexed throughout this drill. Don’t let your toes of the front of your foot touch the ground.
Stand in a “ready” position with your knees slightly flexed. Rapidly shuffle laterally to the right for twenty meters, then sprint forward for twenty meters. Now rapidly shuffle laterally to the left for 20 meters before backpedaling quickly for twenty meters to your starting point, completing the “box”. Don’t stop during this drill. Keep moving from one phase to the next. Repeat this 3 to 5 times.
One Leg Wobble Board Squats
Stand facing away from a bench or step with your rear foot supported on the bench. Place your front leg on a wobble board. Now perform a one leg squat while balancing on the wobble board. Keep your rear foot on the bench so you are in a basic running stride position. Don’t let the knee of your forward leg move in front of your knee. Do twenty repetitions on each leg.
Perform 100 meter barefoot strides. Begin running at a moderate pace and smoothly accelerate to full speed at about 50 meters. Continue at full speed until 80 meters and then “coast” smoothly through the final 20 meters. Repeat 5 to 10 times. The best location for barefoot strides is on an artificial turf field because of the consistent and resilient surface. If you do this on a grass field be very careful of rock, stick and other debris. Don’t do these barefoot strides on a hard surface unless you are an experienced and conditioned barefoot runner.
Home Treatment of Shin Splints
Despite proper condition, you may still suffer from shin splints. If you get them or already have them, what do you do? The first step you should take in treating minor shin splints is to decrease or stop training volume. Apply ice for the first 48 hours followed by heat for the next 48 hours. The ice will decrease inflammation and will help with pain. The heat will promote healing. Keep training volume down until pain free running is possible. If pain is severe or if symptoms persist, stop running and seek professional help. If you suspect a stress fracture, see your doctor immediately. You cannot self treat a stress fracture. If you have a stress fracture, your doctor will probably prescribe 6 weeks of rest.
How can you tell the difference between MTSS, compartment syndrome and a stress fracture. Compartment syndrome will usually present at a dull ache and/or dumbness in the large muscle on the front/outside of your lower leg. MTSS usually occurs on the front/inside portion or just behind the inside of your shin bone. The pain of MTSS is normally not localized and spreads two to four inches up your shin.
Stress fractures are also usually in the inside portion of your shin bone and is more localized to one small location. There may be a small bump at the location of a stress fracture. A test we used back in the old days was to use a tuning fork. Get the tuning fork vibrating and place the handled directly on the point of pain. If a stress fracture is present the tuning fork should cause extreme pain – knock you on your behind type of pain. Stress fractures are hard to diagnose, so if you even suspect one, see your doctor to be sure.
Endurance of the ankle joint plantar flexor muscles in athletes with medial tibial stress syndrome: a case-control study, Madeley LT, Munteanu SE, Bonanno DR, J Sci Med Sport 2007 Dec;10(6):356-62
Medial tibial stress syndrome. The location of muscles in the leg in relation to symptoms, Beck BR, Osternig LR, J Bone Joint Surg Am. 1994, Jul;76(7):1057-61
Biomechanical Risk Factors in the Development of Medial Tibial Stress Syndrome in Distance Runners, Tweed JL, Campbell JA, Avil SJ, J Am Podiartr Med Assoc, 2008 November-December;98(^):436-444