Thursday 18 October 2012

Running Cues and Perceptual Load


One of the things I do on a weekly basis is assist people with their running technique. I have commented quite a lot on running posture, foot placement and efficiency. Now I’d like to comment on how we might go about changing those running patterns and the impact that subjective and objective feedback has on the runner’s perception.

If you’ve been running for many years, you’ll probably have some pretty old, inefficient patterns, whether that is from an injury itself or otherwise. One thing is for sure it will add up in the body to some fairly loaded areas..

The body learns through motor patterns over a long period of time. The key word is that they are learned, hence the nervous system adapts to these movements whether they are faulty or not. These motor patterns are for the most part autonomous once they are learned. Think about when you go for an easy morning run – there’s probably not a lot of conscious thinking going on with regards to technique. You simply go out the door and your brain says run that motor program that means put one foot in front of the other. Beyond that, it’s autonomous

Considering these patterns are autonomous you can see how hard it is to change running technique especially when fatigue sets in. What I’m getting at is you can’t simply tell someone to lean forward from the ankles and all will be solved with their foot strike!

We know from research performed by an Australian physio, Dr Lorimer Mosely whose focus looks at the way the central nervous system (CNS) processes stimuli received from the body that you cannot unlearn a motor pattern, you can however, learn a pattern in preference to the old pattern. Once you learn that pattern it must be reinforced time and time again for it to be the dominant pattern.

What typically occurs to runners as they drop into fatigue their form starts to return to their old pattern. As I like to say “the body always goes to the path of least resistance” whether that is functional or not. If you have learnt a pattern and hold it once fatigued then you have learnt it in preference to your old. I guess that’s the saying ‘old habits die hard!’

So, how do we introduce concepts in terms of running technique? Firstly you will need objective feedback from someone who you trust or understands basic running biomechanics. Subjectivity doesn’t work when it comes to running technique – your perception of how you look will be skewed by years of running in a certain way. Secondly you will need to use that objective feedback and integrate that into your perception. Put simply, once you have a got a technique point or cue – how does that feel to you, what are your perceptions of that cue? Once you have got that feeling, go over and over. You need to give yourself little reminders as to how that feels as you won’t always have that objective feedback on say, a morning run.

Perceptual Load

Once you have a certain technique in your brain (this is where you are developing that motor pattern) it might be helpful to compare it to your old one. A good biomechanic friend of mine refers to this as old way versus new way. Essentially you are trying to gather information in your brain about the difference in motor patterning of two slightly different forms of running. You should be able to feel the difference between the two.

Where to start

Where you start with running technique very much depends on how you currently run and any injuries arising from this. Having said that two key areas I like to start with are

1.     Pelvis
2.     Arms

Pelvis

As discussed in my running posture post this is the foundation of efficient running technique and ideal foot strike positions. If you don’t have this then the rest of the body follows. Ideally, a neutral to slight anterior tilt gives the body good stability through the SIJ and enough clearance to allow hip flexion to propel the body in a horizontal plane with minimal oscillations.

How you ‘cue’ that or how you teach that is a matter of personal preference, as long as the runner understands what is trying to be achieved. This is their perception coming in again. After various running distances and paces give feedback and allow them to feed back, can they grasp the technique? Compare it to the old technique – often this allows them to feel the difference (perception again).

All this should change your foot strike position, your thoraco lumbar position and your stiffness/efficiency through the pelvis.

Arms

One of the big reasons to go to the arms is that they have more fine motor control during running than the legs. Leg position is influenced by the pelvis and arm position as we’ll discuss.  It is much easier to control the arms on the run and something that is in our peripheral vision constantly giving us a reminder.

If the arms take a longer route than they have to – it will be slower. One of two things will happen; Your swing phase prior to foot strike will be slower or you may find yourself spending more time or loading one side more that the other. It can also encourage more rotation than is necessary though the lower thoracic spine – this often creates loading pain around T12.

The teaching portion is the same, so long as the runner understands the ‘cueing’. The objective feedback allows them to formulate an idea and process it in the CNS, again their perception plays a large role in this. Another point to consider is how many teaching cues you want to give? For most, in my experience, one is enough if it makes a good change, two is saturation point – more than this and the CNS simply cannot comprehend the adjustments required ‘on the run’

How long does it take to develop a new motor program?

This gets into some fairly deep territory so I’d rather let the neuroscientists be the experts here. On a superficial level though, the more you practice a motor program the more it will be reinforced. For most it will take a few weeks to go from a cognitive stage to an associative stage (where the programs are being developed and refined). The autonomous stage will take a lot longer!

In closing, make sure the technique adjustment you make is for the better before you drive home a faulty motor pattern – it is so much harder to change than to start correctly!


Thursday 4 October 2012

Running, Foot Placement and Stride Length


Stride Length

With all the rage about foot strike during running and stride length, one might ask, ‘can we increase our stride length without overstriding?’

The short answer is yes! Following is a short commentary on the practical application.

The most efficient stride is one which lands close to its centre of mass (COM), thus eliminating deceleration forces associated with overstriding. Landing outside the centre of mass relies more on ‘muscling through’ the movement rather than letting gravity and momentum carry you through the stride pattern. There is a deceleration followed by an acceleration through the stride, effectively placing increased demands on the lower limb; namely the calf musculature.

Shortening your stride may achieve a foot strike closer to the COM, but how do you achieve an increase in speed without sending your nervous system into overdrive?

Let’s take a closer look; If we increase a slight forward lean from the ankles (for example a 5-10 degree lean) in conjunction with a slight anterior tilt of the pelvis we are able to take a bigger stride, increasing our ‘air ‘ time, thus allowing our foot to land inside/close to our COM. The important concept here is the ‘air’ time with a forward lean. If you simply take a larger stride without a corresponding change in pelvic mechanics and forward lean there will be an increase in knee extension and most likely increased heel collision forces. The second factor here is that knee extension and overstriding increase deceleration/acceleration time. This equates to more time on the ground – the slowest part of the gait cycle!

A slight forward-lean increases our hip extension and thus our corresponding hip flexion on the contralateral leg. As the torso creates a forward-lean the hip extension drive will be in a slight upward and horizontal motion. This motion creates movement with fewer oscillations ie; there will be less energy going vertically and less energy overcoming deceleration forces as you collide with the ground. In other words, most of your energy will be going forward.

Further to this, hip extension increases recruitment through the large gluteus maximus and hamstring muscles - this creates stability through the sacro-iliac joint (SIJ).  Better joint stiffness through the SIJ also creates a more stable base from which to move from.

Fig 1. Two very different running examples. The pace is consistent yet not fast when compared to shorter track races. The front runner displays  better hip extension and minimal overstride. You can see the second runner has greater front leg knee extension creating a large heel strike, This also creates decreased load through the hip extensors (glute max, hamstring)

Will this change where I land on my foot?

A change in landing position on the foot is often observed, however this is secondary to the change in stride length and the mechanics leading up to this. Whether you land on the forefoot is less important. It is more important to have an efficient stride pattern, depending on where you start from of course. Consideration should also be given to your relative speed with regard to where you land on your foot. To illustrate this point, imagine running a 100m race – most, if not all would land on their forefoot. If you stretch that out to 400m, you would probably find increases in mid to rear foot landing in the last part of the race for slower speeds, stretch that out 5k then 10k and you can see the point. Speed does effect your foot position to a large degree. Where the elite differ from us is that they run 10km at faster speeds than many of us can run for 400m. The world record for 10km stands at 26.17, which equates to a margin over 63 sec per 400m for 25 laps!! If you or I were running at that speed we would probably be on our forefoot too!

Fig 2. A classic example of a slight forward lean. Notice the hip extension and projected landing position (within centre of mass) and also towards the midfoot. The pace is about 55 sec per 400m during a 1500m race! The pace may well dictate whether you land on your forefoot or not!

The question might be; Do the best runners simply run in this position due to pace alone or has this position allowed them to train efficiently and adapt to this pace?

What do we define as efficient?

So what is efficient when it comes to running technique and how do we define it? Consider the following points:


  • ·       More ‘air’ time – more time in the swing phase decreases time on the ground, therefore less loading;

  • ·       Stability – A sight anterior tilt of the pelvis will engage more of the intrinsic stabilisers and allow greater hip extension (using the powerful mobilisers off a stable base!);

  • ·       Greater contribution from the large muscles reduces impact on the smaller muscles (calves) which generally fatigue more quickly;

  • ·       Reduced Oscillations – Reduced oscillations with regard to energy direction. You want your energy going in the right direction – forward (not up and down)

This is one of many ways to improve running technique. It is certainly not the only way! It is however an area of hot interest!