Increasing Speed - Interview with Jon Goodwin

Here is the beginning of a great interview with Jon Goodwin, that was done by Patrick Ward on his blog. 
http://optimumsportsperformance.com/blog/

Increasing Speed – Interview with Jon Goodwin
by Patrick on August 9, 2010

Last month I attended the NSCA National Conference and watched a lecture on sprint biomechanics given by Jon Goodwin. The lecture was easily the best of the weekend and I jotted down a lot of notes. Jon was nice enough to take time out of his busy schedule (as both a coach and researcher on sprint biomechanics) to do this interview and I am very excited to present it to you.
1. Thanks for taking the time out of your day to do this interview, Jon. Could you please tell the readers a little bit about yourself.

Essentially, I’m a frustrated athlete. Injury ended my involvement in athletics and like many, coaching was my next avenue to stay involved in the sport I loved. I started coaching in 1997 and from there my coaching interest progressed from athletics to strength and conditioning. Whilst this was going on I completed a BSc in Sport Rehabilitation and an MSc in Biomedical Engineering before progressing from teaching biomechanics at undergraduate level to validating both a BSc in Strength and Conditioning in 2006 and a distance learning MSc in Strength and Conditioning in 2008 at St Mary’s University College in the UK. I now run these programmes whilst continuing some coaching and starting studies towards a PhD in sprint mechanics.

2. Your presentation at the NSCA National Conference on sprint mechanics was excellent. In that presentation you talked a lot contact length and contact frequency in attaining high velocity. Can you please talk a little bit about this? More specifically, why is contact frequency so important and what can we do about it?

The mechanical relationship here is real simple and governed by real simple rules.

Firstly, obeying simple laws of mechanics our motion is only altered by forces. We are subjected to 2 important forces when we run – gravity vertically and air resistance mostly horizontally. If not for these 2 forces we would just continue throught the air at a constant velocity forever. The job of running at max velocity is then to apply forces in such a way that we overcome the changes in motion that these forces create. i.e. when we land we need to arrest the downward velocity we have accrued during freefall and also overcome the loss of horizontal velocity we are subjected to due to air resistance.

Next, we need to think about when we are able to apply the forces that can do these jobs. The answer to that is simple too. The only time we can express these forces actively is when we have a surface to push against. i.e. when we are on the ground.

So now we’re left to consider; what are the variables we have access to while the athlete is on the ground? What things can a coach enable an athlete to change to apply force in a more effective way to allow faster top running velocities?

There are 2 variables we have access to here.

The first is contact length, the distance travelled by the centre of mass whilst the athlete is in contact with the ground. This is controlled by how long your legs are and how far you reach in front of your mass and/or push off behind.

The second is contact time, the time you take in contact with the ground. This is controlled by how long it takes the athlete to apply enough impulse (force x time) to halt their downward velocity and reaccelerate themself back into the air for the next flight phase.

You should be able to see here, we have the components of our standard equations for velocity; a displacement and a time taken to cover that displacement. This leaves us with a fundamentally important relationship for speed (and acceleration and agility) coaches to keep in mind.

Velocity = Contact length / contact time

Obviously our leg length isn’t something we’re actively going to change (not ethically anyway) and wide contact positions such as reaching in front or pushing off a long way behind have been demonstrated to become progressively more ineffective mechanically. Whilst there is likely to be some plasticity in contact length, possibly controlled by athletes strength around the hip, contact length probably only offers small opportunities for change. i.e. getting stronger might enable you to handle longer contact lengths (so allowing faster velocities) but we certainly aren’t going to cue athletes technically to reach out in front or push off further behind.

Contact time on the other hand has been shown to be a huge variable of importance. The primary thing faster sprinters do differently is they generate much higher peak leg extension forces on the ground and they do it much more quickly. This means they can overcome gravity and project themselves back in to the air in less time (air time being virtually almost constant across runners of different ability). With this capability they are able to cover their contact length in less time. So what happens to our equation? Contact time gets smaller, so velocity gets larger. This is the primary mechanism by which faster sprinters travel at faster velocities than slower ones.

read the rest here...