Ever had shin splints or know someone who did? What exactly is a shin splint?
A "shin splint" is a term often used to describe pain on the front of the lower leg. Shin splints are small tears in the interface between the tendon and bone (the fibers are called Sharpey fibers). The tendon weaves its way into the bone forming a very strong connection. When you run or jump too long or too much, you can tear this connection.
But, pain on the front of the lower leg can also be something more ominous: a stress fracture. A stress fracture is a tiny bone break so small you cannot see it on xray until the bone begins to heal. Stress fractures happen when the physical demand placed on the bone exceeds the bone's ability to repair itself.
Bone is one of several tissues in the body which transform themselves from physical load. Two types of cells in bone are responsible for this remarkable makeover:
- Osteoblasts
- Osteoclasts (I call them blasters and clasters)
Blasters produce new bone and clasters tear down existing bone. When bone is exposed to a physical load, as in jogging, clasters go to work carving out new tunnels for more bone while the blasters start churning out new bone cells. As long as the blasters stay ahead of the clasters, all is well. When the clasters win, you lose.
From the athletes we have seen with this problem, I think a better name for a stress fracture might be a distress fracture. Imagine having pain in your lower leg, it hurts when you run or sometimes even walk, hurts at night, you're tender to touch over your lower leg but your Xray is negative. You take 4-6 weeks off from doing the things you love only to find, upon resuming activity, your leg still hurts perhaps even more than prior to taking the time off. You try non-steriodal medications, ice, heat, massage, rest, more rest, magnets, orthotics, but you still cannot run.
The answer to healing a stress fracture and restoring your running ability is to jump start the blasters. You need more bone formation than destruction. But resting does not boost blaster activity. Remember, bone is dynamic and responds to a consistently applied stimulus (as do all other tissues of the body). Put a person in bed for six weeks, and you will see a dramatic drop in bone density. If you have a stress fracture, the last thing to do is rest for long periods of time. In most cases, the advice to rest is well intended. The thinking is that if you stop the offending activity, running, then your bone will heal. But, how does the bone ever regain the strength it needs to withstand the pounding of running if you are sitting on the sidelines?
The are two keys to helping bone heal:
- One is to match the bone's capacity with its need. You must reduce, not completely eliminate, what is referred to as ground reaction force (GRF). GRF is the load produced when your foot hits the ground while walking or jogging. This force can exceed 4 times your body weight for running and up to 11 times body weight for jumping*.
- The second key is maintaining adequate protein in your diet and body fat levels. One the most common problems, more so in female runners, is a low protein and fat diet which can manifest itself in more severe cases as an eating disorder (Visit Dr. Ed Tyson for expert advice and information). The low body fat levels interfere with the production of key hormones that help maintain bone density. A female runner should have at least 12% body fat while males need slightly less at about 6%. If your body fat goes below these levels, you will be at risk for other medical problems. While training to come back from an injury, you will need approximatley .5 - 1 gram of protein / lb. of body weight. So, for a 150 lb. athlete, protein intake would be 75 grams per day. For a reference point, a chicken breast the size of a deck of cards is about 20 grams of protein (a great resource for nutritional advice is Real Life Nutrition).
So what do you do if you have been diagnosed with a stress fracture? Do you have to stop running? It all depends on how badly your bone has been injured and whether you can reduce the GRF enough to stimulate bone formation. Some people can use an insert or shock absorbing shoes (Nike Shox, Z-Coil) and find that they can continue to run while others need to train in a gravity controlled device (Newton Speed Trainer). This technology allows you to regulate, in small increments, the amount of ground reaction force while you run. Your training then becomes a blaster booster. But, while this sounds simple, the process can be difficult. You rarely have a smooth, unfettered run back to full body weight. Since bone responds to load, if the training load is a little too great, your bone may hurt. The good news is, in nearly every case, you can adjust the load and keep training. Week by week you will know exactly how close you are to full body weight and, more importantly, you will feel positive and hopeful.
So, the next time you hear the term "shin splints" remember, shin splints can be a stress fracture. Stress fractures need proper nutritional support (protein and fat) and the application of controlled physical load. Do these things, and you have a great chance of beating a stress fracture.
Make today count.
Doug Kelsey
Author. Teacher. Therapist.
* reference:
Nigg, B. M., G. K. Cole, and G. Bruggemann. Impact forces during heel-toe running. J. Appl. Biomech. 11: 407-432, 1995.
Ramey, M.R. and Williams, K.R. (1985). Ground Reaction Forces in the Triple Jump, international Journal of Sports
