Biomechanics of Foot Strikes & Applications to Running Barefoot or in MinimalFootwear
- 03-27-2012, 12:35 AM
Biomechanics of Foot Strikes & Applications to Running Barefoot or in MinimalFootwear
From the Department Human Evolutionary Biology at Harvard University. They have been investigating the biomechanics of endurance running, comparing habitually barefoot runners with runners who normally run in modern running shoes with built-up heels, stiff soles and arch support.
Here is a summary of their findings:
"Our research asked how and why humans can and did run comfortably without modern running shoes. We tested and confirmed what many people knew already: that most experienced, habitually barefoot runners tend to avoid landing on the heel and instead land with a forefoot or midfoot strike. The bulk of our published research explores the collisional mechanics of different kinds of foot strikes. We show that most forefoot and some midfoot strikes (shod or barefoot) do not generate the sudden, large impact transients that occur when you heel strike (shod or barefoot). Consequently, runners who forefoot or midfoot strike do not need shoes with elevated cushioned heels to cope with these sudden, high transient forces that occur when you land on the ground. Therefore, barefoot and minimally shod people can run easily on the hardest surfaces in the world without discomfort from landing. If impact transient forces contribute to some forms of injury, then this style of running (shod or barefoot) might have some benefits, but that hypothesis remains to be tested."
- 03-27-2012, 12:36 AM
Forefoot Striking & Impact Forces
For millions of years, it is likely that runners landed with no single, specific foot strike, and rather landed with a variety of foot strikes including forefoot, midfoot and heel strikes, but we suspect that the most common form of foot strike was a forefoot strike. Midfoot strikes were probably also more common than they are today. These kinds of strikes (i.e. landing first on the lateral ball of the foot) lead to lower impact forces which may lead to lower rates of injury. We hypothesize and there is anecdotal evidence that forefoot or midfoot striking can help avoid and/or mitigate repetitive stress injuries, especially stress fractures, plantar fasciitis, and runner's knee. We emphasize, however, that this hypothesis on injury has yet to be tested and that there have been no direct studies on the efficacy of forefoot strike running or barefoot running on injury.
Produces Minimal Impact Force with No Impact Transient
Heel Strike in Shoes:
Produces Significant Impact Transient
Other Advantages of Forefoot Striking Barefoot or in Minimal Footwear
•It strengthens the muscles in your foot, especially in the arch. A healthy foot is a strong foot, one that pronates less and is less liable to develop a collapsed arch.
•It may cost less energy to forefoot strike because you use the natural springs in your foot and calf muscles more to store and release energy. Running barefoot or in minimal footwear (usually lighter than traditional running shoes) means that there is less mass to accelerate at the end of the runner's leg with each stride. Running barefoot has been shown to use about 5% less energy than shod running (Divert et al., 2005; Squadrone and Gallozzi, 2009).
•Barefoot running feels great! Your feet have lots of sensory nerves. And because there is minimal impact forces on landing it can be very comfortable provided you develop calluses on your feet (see below).
Disadvantages of Forefoot Striking Barefoot or in Minimal Footwear
•Thick-soled shoes are much more forgiving when running over glass, sharp objects, ice and so on.
•If you have been a heel striker, it takes some time and much work to train your body to forefoot or midfoot strike, especially because you need stronger feet and calf muscles. Runners may be at greater risk of developing Achilles tendonitis when they switch from heel striking to forefoot or midfoot striking (see training tips below).
•Whatever you do, don't overdo it! If you have been a heel striker most of your life, it will take lots of work to switch to forefoot striking. If you develop lasting pain, stop and consult a physician.
•Minimal Shoes. A great way to learn to forefoot strike is to try it first barefoot on a hard but smooth surface like a tennis court, a track or even a smoothly paved road. Your body will quickly tell you what to do! But until you develop good form and build up calluses on your feet, you’ll want to wear minimal footwear to forefoot strike. There are many minimal shoes with several features that allow you to forefoot strike:◦No built up heel. If the heel is too large, then you’ll have to overpoint your toes, which might cause pain and damage to the foot.Tips on Proper Forefoot or Midfoot Strike Form
◦A flexible sole and no arch support. A stiff sole and arch support will prevent the natural flattening of the arch, preventing the muscles and ligaments of the foot from functioning as they were meant to. If you can’t easily twist and bend the sole of the shoe, then it is probably too stiff. At first this will work out and tire the muscles of your foot, but eventually with progressive training the muslces will strengthen.
There is no single “perfect running form.” Everyone’s body is different and no single technique could be best for everyone. Here are some general tips:
•A good landing should feel gentle, relaxed and compliant. You typically land on the ball of your foot towards the lateral side. After the front of your foot lands, let the heel down gradually, bringing the foot and lower leg to a gentle landing as you dorsiflex your ankle under the control of your calf muscles. It's like when you land from a jump, flexing the hip, knee and ankle. Again, the landing should feel soft, springy, and comfortable. It's probably good to land with the foot nearly horizontal so you don't have to work the calves too much.
•Do not over stride (land with your foot too far in front of your hips). Over striding while forefoot or midfoot striking requires you to point your toe more than necessary, adding stress to the calf muscles, Achilles tendon, and the arch of the foot. It often feels as if your feet are striking the ground beneath your hips. It is similar to the way one’s feet land when skipping rope or when running in place (as runners sometimes do when waiting to cross a street).
•A good way to tell if you are landing properly is to run totally barefoot on a hard, smooth surface (e.g. pavement) that is free of debris. Sensory feedback will quickly tell you if you are landing too hard. If you run barefoot on too soft a surface like a beach, you might not learn proper form.
Experienced Barefoot Runner Forefoot Striking
Kenyan Adolescent Who Has Never Worn Shoes
Tips on Transitioning to Forefoot or Midfoot Striking
Forefoot striking barefoot or in minimal footwear requires you to use muscles in your feet (mostly in the arch) that are probably very weak. Running this way also requires much more strength in your calf muscles than heel striking because these muscles must contract eccentrically (while lengthening) to ease the heel onto the ground following the landing. Novice forefoot and midfoot strikers typically experience tired feet, and very stiff, sore calf muscles. In addition, the Achilles tendon often gets very stiff. This is normal and eventually goes away, but you can do several things to make the transition successfully:
•Build up slowly! If you vigorously work out any weak muscles in your body, they will be sore and stiff. Your foot and calf muscles will be no exception. So please, don’t overdo it because you will probably injure yourself if you do too much too soon. ◦Start by walking around barefoot frequently.◦First week: no more than a quarter mile to one mile every other day.•If you are currently running a lot, you don’t need to drastically reduce your mileage. Instead, supplement forefoot or midfoot striking with running the way that you normally ran before beginning the transition. Over the course of several months, gradually increase the proportion of forefoot or midfoot striking and reduce the proportion of running in your old style. Use the same 10% per week guideline in increasing the amount of running you do forefoot striking.
◦Increase your distance by no more than 10% per week. This is not a hard and fast rule, but a general guide. If your muscles remain sore, do not increase your training. Take an extra day off or maintain your distance for another week.
◦Stop and let your body heal if you experience pain. Sore, tired muscles are normal, but bone, joint, or soft-tissue pain is a signal of injury.
◦Be patient and build gradually. It takes months to make the transition.
•It is essential to stretch your calves and hamstrings carefully and regularly as you make the transition. Massage your calf muscles and arches frequently to break down scar tissue. This will help your muscles to heal and get stronger.
•Listen to your feet. Stop if your arches are hurting, if the top of your foot is hurting, or if anything else hurts! Sometimes arch and foot pain occurs from landing with your feet too far forward relative to your hips and having to point your toes too much. It can also occur from landing with too rigid a foot and not letting your heel drop gently.
•Many people who run very slowly find that forefoot striking actually makes them run a little faster.
•Land gently on your forefoot and gradually let the heel come down
•Stretch your calves and Achilles tendon
•Don’t do anything that causes pain
•Listen to your body and run totally barefoot to learn good form
•Buy minimal shoes that lack high heels and stiff soles
•Consult a doctor
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