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Running Injuries from Over-Striding

Most running injuries are caused by the high impact of your foot hitting the ground, which is determined most by the length of person's natural stride (Scan J Med & Sci in Sports, May 30, 2018). Unnecessarily high impact can be caused by over-striding. Contrary to common belief, it is not important whether you land on the front of your foot or the heel. However, the more you over-stride, the more likely you are to land on your heel. Landing on the front of your foot does not prevent injuries, it is only a marker that you are not over-striding. A study of the 2017 IAAF World Championships showed that 54 percent of the men and 67 percent of women landed on their heels (Journal of Biomechanics, May 22, 2019). This proportion was the same for the top and bottom runners, and did not change much through the entire marathon. However, the top four men were heel-strikers, from Kenya, Ethiopia, Tanzania, and Great Britain, and they landed on their heels for the entire race.

Running at a six minute per mile pace, your foot hits the ground with a force equal to three times your body weight. This force is transmitted up your legs to your hips and back, and done repetitively, it can shatter bones and tear muscles and tendons (Br J Sports Med, Apr 2016;50(8):450-7; Br J Sports Med, Aug 2007; 41(8):469–480). Runners who are injured frequently are likely to benefit most by shortening their strides, which then coincidentally increases likelihood of their landing on the front part of their feet, rather than on their heels.

Stride Length, Speed and Injuries
How fast you can run is determined by the length of your stride times the rate that your feet hit the ground. However, you cannot run faster by consciously trying to increase your stride length. Many runners try to extend their strides in the mistaken belief that it will help them to run faster. When you try to take longer strides than what feels natural to you, you lose energy and run more slowly. Furthermore, you increase your chance of injuring yourself because it slows your cadence and increases the force of your feet striking the ground.

Your most efficient stride length is determined by what feels most comfortable to you. Your foot hits the ground with great force. The tendons in your legs absorb some of this energy and then contract forcibly after your heel hits the ground so you regain about 60 to 75 percent of that as stored energy. When you try to take a stride that is longer than your natural one, you lose a great deal of this stored energy, tire much earlier and move your legs at a slower rate. When most athletes run as fast as they can, they run at close to the same stride rate. For example, a video at the New York City Marathon showed that the top 150 runners had the same cadence, taking 92 to 94 steps a minute. The difference between the top runners and the others is that the best runners took longer strides. The key to running faster in races is to make your leg muscles stronger so you can contract them with greater force so they drive you forward with a longer stride.

Making Your Leg Muscles Stronger
The only safe way to increase your stride length is to strengthen your leg muscles to help them contract with greater force. To make a muscle stronger, you have to damage the muscle fibers so they will be stronger when they heal. Competitive runners strengthen their legs so they have longer natural strides by:
• doing interval training (running very fast short bursts), two or three times a week
• running up and down hills once or twice a week

You can also strengthen your legs by using strength training machines, but you should do leg presses or knee and hip extensions only on the same days that you run fast. You cannot do strength training on recovery days because it will delay healing of your muscle fibers that were damaged from the previous day's intense running. Most runners are better off not using strength machines on their legs because running very fast damages muscles and so does using strength machines. The combined load of running fast and using machines increases your risk for major injuries.

My Recommendations
If you are a regular runner, realize that you can become stronger and faster, and gain more health benefits, if you try to pick up the pace during some of your runs. However, this can increase your chances of injuries. You can help to protect yourself from injuries by:
• stopping a workout immediately if you feel localized pain that does not go away as soon as you slow down
• taking shorter strides
• avoiding running fast on consecutive days
For more on running injuries, see my reports on Flat Feet, Pigeon Toes and Bow Legs
Runner's Knee
Stress Fractures

June 2nd, 2019
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
 
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