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!

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