這篇跑步的文章很不錯:Heel Striking, Overstriding, and Cadence

來源: 閑情 2018-07-17 10:19:13 [] [博客] [舊帖] [給我悄悄話] 本文已被閱讀: 次 (18946 bytes)

Heel Striking, Overstriding, and Cadence

The running industry is often caught up in a whirlwind of rumors; drugs in our sport, how running is “bad for your knees”, and that it is bad to run with your heel striking first.

We cannot do much about the first one, that is up to the drug federations, and we will keep battling the out of date myth that running is bad for your knees, but we can show you that if you are a heel striker you do not need to adjust your running stride, nor do you need to stop being a heel striker IF you are not overstriding and your cadence is high enough.

Now:

If you want to transition from running with a heel strike to a midfoot or forefoot strike, that is okay too, but a heel strike itself is not the reason you have injuries like shin splints or IT band syndrome. If you want to find the best running shoes for a heavy heel strike, we are big fans of choosing a shoe that is comfortable to you, rather than relying on a particular shoe to fix a problem

Today we are going to explain to you what is a heel strike and why heel striking is not as bad as you think, how to determine your ideal running cadence, and how to prevent overstriding, which is most likely the real reason you keep getting injured.

This article comes with a warning though, you will have to be prepared to explain this over and over again to running friends who ask you about a heel strike vs. a forefoot strike.

Ready to become the master?

Heel striking is bad for runners right? Wrong! Overstriding is bad for runners, and here is how to increase your running cadence and stop overstriding so you can stop getting injured all the time!

What Does a Running Stride Involve?

In last week’s article, Introduction To Running Biomechanics, we took a look at the individual components that make up a single stride, collectively referred to as the Gait Cycle.

We considered two phases: the Stance Phase (during which your foot is in contact with the ground) and the Swing Phase (during which the same foot is off the ground).

We divided the stance phase up into four stages:

Initial contact

When the foot of the front leg first touches the ground

Braking/absorption

The body making a controlled landing and absorbing elastic energy to use later in propulsion

Midstance

The moment when the supporting leg takes maximum load as the body passes over it

Propulsion

The ankle, knee and hip all extending (triple extension) to push the body up and forwards using the elastic energy absorbed during braking, up to the moment when the foot leaves the ground (toe off).

This marks the beginning of the Swing Phase, a passive stretch reflex mechanism that fires the now non weight-bearing leg forwards, until the Gait Cycle for that particular leg starts once again with initial contact.

Now:

Although running depends on whole body interaction, being aware of the individual components of the Gait Cycle can help you appreciate how slight modifications to your running form can have a knock on effect that can lead to overall improvement in performance and less susceptibility to injury.

The key words in that sentence are your running form.

Despite claims made by marketed running styles like Chi, Pose and Evolution, differences in our biological make-up strongly suggests that what works for one runner will not necessarily work for everybody.

The fact that elite, world class runners possess different running styles strengthens the argument against a one-style-fits-all approach.

However, there are some elements common to almost all successful running styles, and we are going to dive in deeper to those today.

Is Landing with a Heel Strike Running Bad?

Over the last couple of years, the rise in popularity for barefoot running and minimalistic shoes has fueled debate over what part of the foot should touch the ground first – the heel, the midfoot or the forefoot.

In the excellent article “Is there an Ideal Footstrike for Runners?,” John Davis puts aside claims made by supporters and opponents of minimalistic footwear and instead takes a look at what scientific studies to date tell us about different footstrike styles.

As you will see from his article, much of the data seems to contradict itself, advantages being uncovered only to later reveal disadvantages.

But get this:

What studies do suggest is that the issue is not so much what part of your foot touches the ground first, but how close that initial contact is to underneath your hips, i.e. your centre of mass.

What does that mean?

Let us explain:

Does Running With a Heel Strike Cause Injuries?

Over the last couple of years, the heel strike (also known as a rearfoot strike) has been increasingly labelled as the chief perpetrator of running injury.

Check this out:

Consider the results of a study done by Pete Larson at the 2009 Manchester City Marathon.

Using a high speed camera, Larson filmed runners at the 10km and 32km points of the race, and later classified them according to their foot strike.

At the 10K mark, his results for 936 runners were as follows:

Heel strike: 88.9%; midfoot: 3.4%; forefoot: 1.8%; asymmetrical 5.9%

At the 32K mark, Larson identified 286 runners of the above runners, displaying the following:

Heel strike: 93% (87.8% were also heel striking at 10k.). Forefoot: 0%

In light of these performance results, how can heel striking be regarded as inefficient?

The answer could well be in what we saw earlier: running efficiency is not so much a question of what part of the foot touches the ground first, but how close initial contact is to underneath the hips, i.e. your centre of mass.

A heel strike that lands close to the hips and on a bent knee causes no significant over-braking or over-loading to the knee.

It is what coaches often refer to as a “glancing” or “proprioceptive” heel strike and should not be primary cause for concern or preoccupation.

Get this:

This is the heel-strike sometimes seen in elite athletes, a classic example being that of American long distance specialist Meb Keflezighi, silver medalist in the 2004 Olympics men’s marathon, winner of the 2013 Boston Marathon.

running cadence

Meb Keflezighi in the 2010 Boston Marathon
(Courtesy of Peter Larson)

If Meb can heel strike and get away with it, I think we can too! Remember to listen to the interview with Meb’s Coach, Bob Larsen for more insights into training with Meb.

What is Overstriding and How Do I Know If I am Overstriding?

In contrast to the above is the act of overstriding, where the foot comes into contact with the ground well ahead of the hips.

More often than not with overstriding, it is the heel that strikes first but what is more important is the fact that, as seen in the photo below, the knee is straight and locked out.

Overstriding is commonly associated with the creation of greater braking forces and excessive impact.

Research has shown that a more extended knee contact angle can increase the forces experienced by the body and therefore increase injury potential.

heelstriking-overstriding-and-cadence

Overstriding runner
(Courtesy of Peter Larson)

What does this mean?

If you are overstriding, landing with your leg straight, knee locked out, you are sending a strong shockwave up your leg, which increases your risk of injury. From hamstring to achilles, and especially shin splints, overstriding is more likely to get you injured than any other aspect of your running form.

Still confused?

Listen to this podcast episode with Max Prokopy of UVA Speed Clinic, who explains what overstriding can cause and how to stop overstriding (and getting injuries) with a few simple changes you can make during your runs.

This is interesting:

Runners who overstride take fewer steps per minute (at a given running speed) than runners who do not over-stride.

In other words, they have a lower stride-rate.

In the 2011 paper “Effects of step rate manipulation on joint mechanics during running”, researchers from the University of Wisconsin-Madison investigated whether they could reduce impact forces in runners by increasing their stride rate.

By monitoring load changes following +/-5% and +/-10% modifications to stride rate, the researchers concluded:

Subtle increases in step rate can substantially reduce the loading to the hip and knee joints during running and may prove beneficial in the prevention and treatment of common running-related injuries.

How do Runners Increase Run Cadence?

Another word for stride rate is cadence. It is measured in strides per minute (spm).

You can easily determine your own cadence by counting the number of times your left foot hits the ground whilst running for 30 seconds.

Let's imagine yours was 40.

Double that to get the total for 60 seconds (80); then double it again to get the total for both feet (160).

Your cadence (for that particular running speed) is therefore 160spm.

Here’s the deal:

A cadence of less than 160spm is typically seen in runners who overstride.

It is important that we make a distinction between jogging and running.

Jogging (including warming up) is performed at a lower speed and is bound to involve a lower cadence.

Though some one-size-fits-all running styles pitch an optimum cadence that should be maintained at all speeds, even elite athletes are seen to drop their cadence slightly for different running paces.

Did you know?

Your height may also play a part in your stride rate, it may be limiting your stride frequency and max running cadence.

Is there a best running cadence?

Once again, you have to be careful what you read.

As the subject of cadence has become more main-stream, so too has the emergence of the “magic” optimum stride-rate of 180spm.

The reason for this is as follows: at the 1984 Olympics, famous running coach Jack Daniels counted the stride rates among elite distance runners.

Of the 46 he studied, only one took less than 180spm (176spm). Daniels also noted that in his 20 years of coaching college students, he never had a beginner runner with a stride rate of over 180spm.

Unfortunately, Daniels’ studies have been misquoted and as a result lead to all too frequent claims that everybody should be running at 180spm.

These claims ignore the fact that Daniels noted stride rates of at least 180spm, not exactly 180spm.

History clearly shows Haile Gebrselassie running 197spm en route to his world record time of 2:03:59 at the 2008 Berlin Marathon, and Abebe Bikila used a 217spm to become the first man to run a 2:12 marathon (2:12:13, Tokyo 1964).

What’s the bottom line?

As was suggested at the beginning of this article, differences in our biological make-up means what works for one runner will not necessarily work for all.

If you do one day become an elite distance runner (and we sincerely hope you do!) it is highly likely your race cadence will be over 180spm.

However, and this is the important part, your journey to 180spm and beyond needs to be gradual.

The average recreational runner has a cadence closer to 150-170 spm.

How quickly you progress and in what direction your running form develops will be affected by factors unique to you – your height, hip mobility, level of general fitness, to name a few.

The safest and most appropriate way to increase your cadence is in the University of Wisconsin-Madison paper we considered earlier: increase your cadence by 5% to 10% at a time.

How to Increase Your Running Cadence

We dedicated an entire separate article to increasing your stride frequency and step length to improve your speed if you want to read about this in further detail, but here are the steps to gradually increase running cadence to prevent ending up injured.

Determine your ideal running cadence

Using the counting your steps method described above, determine your current cadence for a speed you would use for a 5km+ race.

Let’s imagine it is 160spm.

Adding the 5% increase (10% could well be too much of a jump), your new target is 168spm.

Change your new cadence for short periods to start with

Start by adding short distances into your runs in which you try to maintain your new target.

This can be done through use of a metronome (available from Amazon or downloadable as an app for your phone). Be careful as many of these gadgets still regard 180spm as the “magic” number and will only provide beats of 180spm+.

Sites like JogTunes can be used to find music with beats per minute (bpm) to match your desired spm.

Otherwise, you can always just monitor your progress with a 30-second one foot count (then multiply it by 4).

Run on a treadmill to measure your cadence

Practicing your new stride rate on a treadmill can sometimes be handy as you can set the speed to stay the same.

Increase your running cadence by 5% at a time

Once you have can comfortably run your a 5km+ pace at your new stride per minute (without thinking about it – remember we are seeking unconscious competence), add another 5% and repeat the process.

Want to learn more?

所有跟帖: 

腳後跟著地疼痛能輕點,我試了下腳尖著地,腳疼得沒法跑了。 -貝加兒湖畔- 給 貝加兒湖畔 發送悄悄話 (0 bytes) () 07/17/2018 postreply 10:30:12

不管腳尖或者腳後跟接觸地麵,而應盡量用最大的麵積承受身體重心。 -閑情- 給 閑情 發送悄悄話 閑情 的博客首頁 (89 bytes) () 07/17/2018 postreply 11:18:49

看了你下麵的回帖才知道。如果你一開始跑步就出問題,還是跑步要領和姿勢不對。 -閑情- 給 閑情 發送悄悄話 閑情 的博客首頁 (0 bytes) () 07/17/2018 postreply 11:20:27

跑了有快一個月,可能剛開始跑太快姿勢也不好。這兩天太疼隻好走了,等稍好點我再試試 -貝加兒湖畔- 給 貝加兒湖畔 發送悄悄話 (0 bytes) () 07/17/2018 postreply 11:24:21

最好休息幾天。 -閑情- 給 閑情 發送悄悄話 閑情 的博客首頁 (405 bytes) () 07/17/2018 postreply 11:33:31

腳尖著地跑,還不如去上芭蕾呢, 還練小腿肌肉。 -Shanghaigirl98- 給 Shanghaigirl98 發送悄悄話 (169 bytes) () 07/17/2018 postreply 21:21:06

覺得在草地上跑最好,不用買昂貴的cushion 厚的跑鞋,愛怎麽跑怎麽跑。也不容易受傷,就是早上有露水。得傍晚。 -alpha123- 給 alpha123 發送悄悄話 (0 bytes) () 07/17/2018 postreply 12:11:07

草地要平整的,沒有石頭。否則人扭傷腳很危險 -閑情- 給 閑情 發送悄悄話 閑情 的博客首頁 (0 bytes) () 07/17/2018 postreply 12:32:27

我最喜歡在海邊沙灘上光腳跑,踩著退退進進的海水,絕對是一種享受。 -tryonetry- 給 tryonetry 發送悄悄話 tryonetry 的博客首頁 (0 bytes) () 07/17/2018 postreply 16:16:13

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