Speedendurance.com

Speed is the Result of Net Forces Acting on the Ground

Posted: 03 Jan 2010 12:14 PM PST

I really like this quote from Charlie Francis when it comes to the debate over stride rate vs stride frequency. The answer, according to Ralph Mann (and others) at the USATF NPEP, is ground contact. Specifically, the reduction of ground contact time.

Charlie Francis quotes from his latest manual:

Too many coaches are coaching the speed right out of their athletes. Some believe that it is stride frequency and others believe that it is stride length that causes speed.

The answer is neither. They are both measurements of speed but not the cause of speed. Speed is the result of net forces acting on the ground.

It is how fast the body is moving over the ground that matters. Apply more force and you will have an increase in stride length and stride frequency.

Let's dissect this quote a bit further… Here are a couple of random semi-related topics for discussion that agrees (or disagrees!) with Francis.

Dwain Chambers on Beating Usain Bolt

Dwain Chambers keeps bringing up this topic on his strategy when trying to beat Usain Bolt. Remember, he actually trained in Jamaica with Glen Mills and Usain and I credit Dwain for having a positive attitude.

From:

http://speedendurance.com/2008/12/02/dwain-chambers-on-usain-bolt-asafa-powell-stride-length-and-stride-frequency/

Chambers, who says that "attention to detail" in coaching has been the key to Jamaica becoming the sprint capital of the world, is confident of beating Bolt in 2009. "Usain can do the 100 metres in 41 strides," Chambers said.

"I would take 43 or 44. But I have better stride frequency: 4.96 per second compared to 4.65. To beat him I need to maintain my frequency and improve my stride. Beijing was his time to shine, but he’s only human."

In another case, here is a YouTube video of Dwain on a radio talk show. For those who are impatient, fast forward to the final 30 seconds where he discusses stride rate and stride frequency.

Tyson Gay & Usain Bolt – First 3 steps

Here's an interesting Youtube video of Tyson and Usain side by side, in super slow mo. Take a look how the first 3 steps are identical in cadence (stride frequency) as if they were doing a marching military drill.

Then Tyson appears to have a faster cadence, while Usain has longer strides. However, Bolt is covering the ground at a much faster speed, and eventually wins.

Is it fair to say Usain is applying more force to the ground?

SFU-Penn State Longer Toes Study

The Vancouver Sun gave the bottom half of Page 1 on Nov. 13 to a story from a SFU study that finds longer toes may give sprinters a leg up on other runners. Sabrina Lee (no relation), a post-doctoral fellow at SFU and Penn State researcher Stephen Piazza found that longer toes and a unique ankle structure give sprinters a "burst of acceleration" over others.

You can read the various articles here and here.

Long toes provide sprinters the advantage of maintaining maximum contact with the ground just a little bit longer than other runners.

‘We wanted to see how much acceleration we could get out of the model when we changed the tendon lever arm and the length of the toes,’ said Piazza. ‘What we found is that when the Achilles tendon lever arm is the shortest and the toes are longest, we get the greatest acceleration.’

This is a bit of a contradiction to the ground contact theory, especially during the latter stages of a 400 meters.