##### Speed is an interaction of stride length (the distance between each step), stride frequency (how many steps we take in a given time) and the power developed each time our feet come into contact with the ground!

So very basically, to get faster all we need to do is take bigger steps and move our feet quicker!!

Right???……………

What if we take Newton’s 3rd Law? (Stay with me on this!!)

For every action, there is an equal and opposite reaction (When body A exerts a force on body B, body B exerts a reactive force that is equal in magnitude and opposite in direction on body A)

To put it simply, when we stand up, our bodyweight exerts a force into the ground beneath us through our feet. If this force is not counteracted in some way by the ground we are standing on we simply sink through the ground……

Not really ideal is it??

So, to stop this from happening the ground pushes back against us with the exact same force and we stay standing up!………

SIMPLE

The same thing happens when we walk, run or sprint. Every time the foot contacts the ground the ground pushes back in the opposite direction with the same force applied by the foot contact. This is known as ground reaction force or GRF.

In walking, when the heel strikes the ground the resulting GRF acts against the direction we are walking and so works as a breaking force (i.e it works against us to slow us down) although this seems counteractive it works as a stabalising, protective loading mechanism for the ankles, hips and knees.

R= GRF acting through the heel to slow down movement for transition to toe off

As we move forward and push off through the ball of the foot, GRF changes and acts to propel us forward.

When we decide we need to get from A to B faster, we begin to increase our speed and transition through running on to sprinting. Now our aim is to eliminate or reduce the initial breaking force we use when walking and to maximize the force we develop when we contact the ground. In order to do this we need to strike the ground with the ball of the foot rather than the heel……… So how do we do that??

## SPRINT MECHANICS

This is where Stride Length (SL) comes into play.

Elite sprinters are characterized by greater stride frequency and short Ground Contact times rather than stride length, showing only average or slightly greater than average stride lengths.

Longer strides generate GFR with greater counteracting horizontal force. Over-striding is counterproductive and can increase energy cost of running by up to 30%.

Ideally our foot should contact the ground under or slightly in front of our hips for optimum direction of force production. If our foot strikes the ground too far in front of our body (over-striding) we strike the ground with the heel of the foot causing that breaking force to be applied as in walking. In order to prevent this we need to do 2 things –

• Change body position When we want to accelerate we need to change the position of our torso from straight up to leaning forward at an angle (optimally 45°) with the core engaged. This “lean” puts us in a position where we are forced onto the ball of the foot and have reduced the likelihood of contacting the ground with the heel.

•  Optimise Knee Drive and “Toe Up” Position – Effective knee drive and foot position (Toe-Up) puts sufficient stretch and tension through the glutes, quads, hamstrings and calf muscles and essentially PRE-LOADS them, allowing them to generate an elastic force (Stretch Shortening Cycle – we’ll discuss later in power development!!). When the ball of the foot contacts the ground the elastic tension is released. This coupled with forceful muscle contraction acts like a spring to drive the body forward

Look at it like this, imagine pulling the toe up and driving the knee is like loading a gun, when the foot hits the ground you’ve pulled the trigger, the resulting force propels the body forward just like the bullet leaving the gun.

If done properly this significantly reduces the energy cost of sprinting.

If we get a handle on these 2 points (body position and knee drive/toe up) we settle naturally into a stride length that suits our own anatomical structures (i.e height and limb/torso length).

Check out the exercises below for training body position, knee drive and foot position!!

### WALL DRIVES

– Knee up and toe up

– Low heel recovery

– Ball of foot strikes the ground behind the hips

– Drive foot back into the floor behind the body

-The aim with this exercise is to transition from left knee drive to right knee drive and back again with the core engaged with the torso tall keeping the knee drive, toe up technique.

-As this becomes easier we simply increase the speed at which we change between knee drives.

### BANDED DRIVES

-Same technique as the wall drives above.

-Set up in a 2 point stance.

-Drive into the resistance band to encourage explosiveness off the line.

-Maximise foot drive into the ground on the rear leg during knee drive.

### FALLING STARTS

-Stand tall with core engaged.

-Raise up onto the balls of the feet.

-Lean forward through the feet in a falling motion.

-Use explosive knee drive to recover and drive off the line.

-The main aim is to stay tall through the torso, keeping the core switched on preventing any breaking of the kinetic chain through flexion of the spine.

Now we’ve tackled mechanics,

Forward Lean

Knee Up/Toe Up

Foot Contact

WHAT NEXT???……….

As we said before, speed is about power development and we can only develop power when our foot comes into contact with the ground. So what should we be doing in training to ensure we take full advantage of proper mechanics so we can transform this into optimum power output on each foot strike??

## POWER DEVELOPMENT FOR SPEED

Without getting bogged down in muscle physiology lets take a very simplistic look at the Stretch Shortening cycle (SSC).

The SSC is an active stretch of a muscle immediately followed by a forceful contraction of the same muscle. Think of it as pulling an elastic band to full stretch and letting it go!!!

There are 2 types of SSC, fast and slow. Sprinting requires us to use the fast SSC. This means the pre-stretch of the muscle must be counteracted and reversed extremely fast by a forceful contraction of the same muscle with minimal ground contact time. If the pre-load is too slow or the contact time too long, the elastic tension we’ve built up simply dissipates as heat. This leaves us in a position where we rely solely on the contraction of the muscle without the help of the elastic recoil. Imagine we’ve just thrown the elastic band without stretching it first…. (Not that effective!!)

So what are the best exercises to use to help develop our fast SSC!!**

### HURDLE HOPS

-Keep the hurdles low to begin with. This will allow you to work on reversing the pre-load and minimize contact time under a relatively low pre-load (height).

-As you become more efficient at these you can increase the hurdle height, gradually increasing the pre-load.

-The main aim is to bound through the hurdles spending as little time on the ground as possible and being explosive over each hurdle.

### COUNTERMOVEMENT JUMPS

-The CMJ involves a quick squat or dip of the hips immediately prior to an explosive jump.

-The aim is to squat quickly and explode as high into the air as possible.

-Keep the focus on snapping the hips down and up to encourage a high speed movement. This movement acts to pre-load the elastic tension before the rapid transition to jumping.

### DROP JUMPS

• Drop jumps are characterized by dropping from a box (optimum box height varies from athlete to athlete) with 2 feet contacting the ground at the same time followed by an explosive jump.

• The aim is to contact the ground on the balls of the feet without the heels touching the ground, keeping minimal hip and knee bend (maximizing leg stiffness)

• Athletes should aim to spend as little time on the ground as possible and jump as high into the air as possible.

** Athletes should have attained a solid strength base and be functionally competent prior to commencing plyometric training. If you are unsure if you should be training plyometrics always check with a qualified strength and conditioning coach first!

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