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Monthly Archives: August 2015

heelstrike

By Alex Hutchinson MONDAY, SEPTEMBER 9, 2013

There was a time, a few years ago, when research into footstrike and biomechanics and running shoes seemed fresh and exciting. We were all eager to put old assumptions to the test and try out new ideas. These days, it feels like the bloom is off the rose. Clear, unambiguous answers about the “best” way to run have — surprise, surprise — remained elusive, and I get the sense that many people have decided they have enough information to make up their minds, and no longer need to keep asking new questions.

On the bright side, this might mean that’s possible to look at interesting research without the distraction of having each new study hyped as either “proving” or “disproving” the benefits of barefoot running. For example, a new study published in Medicine & Science in Sports & Exercise, from researchers in Spain, with the seemingly provocative title “Rearfoot Striking Runners Are More Economical than Midfoot Strikers,” has some interesting insights.

One of the main criticisms of studies that try to compare midfoot (and/or forefoot — the two categories are lumped together in the study, and I’ll do the same for the rest of this post) strikes with rearfoot strikes is that they often involve asking people from one category to force themselves to run in an unfamiliar way for a short period of time, then draw conclusions based on this limited sample. Alternately, other studies assemble different groups of midfoot and rearfoot strikers, but with such diverse characteristics that it’s hard to draw any conclusions from the comparison. The strength of the new Spanish study is in addressing these concerns: they assembled two very homogeneous groups of sub-elite distance runners, with 10 midfoot strikers and 10 rearfoot strikers. The groups were very closely matched in age, running experience, training volume, BMI, VO2max, HRmax, and fitness, with average half-marathon bests of 1:10:59 and 1:10:21 (all runners in both groups had run between 1:06 and 1:14, and all had completed a half-marathon in the six weeks prior to the study).

The main finding of the study is that, at three different submaximal paces, the rearfoot strikers were more economical (i.e. burned less energy) than the midfoot strikers. At 8:47/mile, they were 5.4% more economical; at 7:26/mile they were 9.3% more economical; and at 6:26/mile they were 5.0% more economical, though the difference was no longer statistically significant at the fastest speed. This isn’t a huge surprise (several other studies have reached similar conclusions), but it’s an interesting data point for this particular set of subjects.

The question now is: why? Rodger Kram, the director of the University of Colorado’s Locomotion Lab, suggests that, while midfoot strike allows you to store more energy in the “springs” of your ankle, it also requires more metabolic energy to generate the higher required muscle tension. The conclusion from a presentation at ASB by Allison Gruber, Brian Umberger and Joseph Hamill of UMass-Amherst was that these two factors balance each other out in the gastrocnemius, but the extra energy requirements dominate in the soleus (those are the two muscles that make up the calf).

All this is interesting stuff that could give rise to all sorts of debates and discussions — so feel free to fire away in the comments. But first, I’d like to highlight a more minor point that I find particularly intriguing. Check out this graph showing the step length and step rate of the runners:

cadence_and_footstrike_0

One unfortunate thing is that they don’t break out the results for the two groups — the reason being that they were essentially identical, with no differences observable between the two groups. Still, I would have liked to see the actual data, with individual variation shown.

The reason this is intriguing is that there’s a common set of assocations that links minimalism to midfoot/forefoot striking to shorter stride/higher cadence to lower loads on the joints. And certainly, if you take a habitually shod runner and ask them to run barefoot, it makes sense that they’ll shorten their stride as they adjust to the lack of cushioning. But in this particular group of runners, at least — a very fit, experienced and well-trained group — their footstrike pattern had no bearing on their cadence across the full range of paces. It’s tempting to assume that these runners had enough experience that they’d already converged on an efficient cadence, independent of the effects of footstrike. Of course, that may not be true of less experienced runners.

I’d also like to note that, consistent with every single study done with runners of every ability, cadence increases as a function of speed: the faster they run, the quicker their steps. For these particular very fast and very fit runners, they hit 180 steps per minute (i.e. step rate of 3.0 Hz) at about 5 m/s, or 5:22 per mile. By (not so) incredible coincidence, that’s also roughly where I hit 180 steps per minute. If you tried to force them to run at 180 when they were jogging at 9:00/mile (on the left of the graph), they’d be uncomfortable — and less efficient. Again, runners with differing levels of experience (and ability and body size) will have different cadence curves, but it will always be a curve rather than a straight horizontal line: the faster you go, the quicker your steps.

 

Taken from http://www.runnersworld.com/sweat-science/heel-strike-uses-less-energy-than-midfoot-strike

Pronation is the way the foot rolls inward when you walk and run. It is part of the natural movement that helps the lower leg deal with shock. Some people pronate more (overpronation) or less (underpronation) than others.

Though this is not bad in itself, it does affect the way you run and it may increase the likelihood of injury. This makes your pronation pattern an important factor in choosing the right running shoes.

WHAT IS PRONATION?

Pronation occurs at the joint below the ankle, the subtalar joint. It describes the inward rolling motion of the foot just after it lands on the ground. This moment is called initial contact, which is part of the stance phase of the gait cycle.

Running shoes are designed today specifically for different pronation patterns. When you pick your next pair of running shoes, your pronation type is a very important factor in your choice.

NEUTRAL PRONATION

You are likely to be a neutral pronator if the soles of your shoes show wear in an S-shaped pattern, from the outer (lateral) heel to the big toe. When you have a normal pronation pattern you can run in a wide variety of shoes, but specialised neutral running shoes offering cushioning and support are most suitable. The GEL-NIMBUS is the leading cushioning model for neutral runners.

Pronation pattern of a neutral runner

Pronation pattern of a neutral runner

 

UNDERPRONATION

Underpronation, also known as supination, is when the foot doesn’t pronate much. The outer or lateral side of the heel hits the ground at an increased angle, and little or no normal pronation occurs, resulting in a large transmission of shock through the lower leg. This lateral loading of the foot continues for the entire stance phase of gait, further affecting running efficiency.

Underpronation (also known as supination)

Underpronation (also known as supination)

 As underpronators tend to be susceptible to shock-related injuries like stress fractures, you should choose a neutral running shoe with plenty of cushioning, for example the GEL-CUMULUS.

 

OVERPRONATION

Overpronation is when the foot rolls in excessively, or at a time when it should not, for instance late in the stance phase of gait. In this case much weight is transferred to the inner or medial side of the foot, and as the runner moves forward the load is borne by the inner edge rather than the ball of the foot. This destabilises the foot, which will attempt to regain stability by compensating for the inward movement. In a kind of chain reaction, this in turn affects the biomechanical efficiency of the leg, especially the knee and hip.

Overpronation

Overpronation

 The shoes of an overpronator will show extra wear on the inside of the heel and under the ball of the foot, especially the big toe.

Overpronators should consider choosing maximum support or structured cushioning shoes. Running shoes in both of these categories will help your feet distribute the impact of running more effectively. The GEL-KAYANO is a leading structured cushioning shoe.

 

 

Taken From www.asics.com.au

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