Triple Extension, Vertical Displacement, Stride Length, and Ground Contact

You can’t talk about sprinting without mentioning all these KPI (key performance indicators) in the same breath. I am referring to Triple Extension, Vertical Displacement, Stride Length (& Air Time), and Ground Contact. They all go hand in hand.

One of the best examples are some illustrations from Charlie Francis’ book, which were created by Derek Hansen of Strengthpowerspeed.com and Runningmechanics.com (used with permission). We had met Charlie at a seminar hosted by “personal trainer turned Internet marketer” Alwyn Cosgrove in Southern California back in 2001. Charlie was still using hand drawn acetate slides, and Derek offered to convert them to computer generated graphics using Corel Draw! (we like to support our Canadian high-tech companies :)

I highly recommend reading some of Charlie’s works, then applying the knowledge to your training. If you still have issues with Charlie’s tainted drug image, then you can stop reading this article now. Thanks for stopping by!

If there is one KPI (key performance indicator) that can improve your sprinting speed, whether you are an Elite world class sprinter, or a Youth/Masters sprinter, I would emphasize Triple Extension.

(I’ll repeat) You can’t mention Triple Extension in the same breath without mentioning Muscle Excitation and Inhibition, Vertical Displacement, Stride Length, Air Time, Ground Contact, and increasing forces.

As your sprint times decrease, and your top end speed increases, you will need greater forces at ground contact, with a shorter ground contact time.

You will also need to excite the muscles faster for top speed sprinting, but at the same inhibit and relax the antagonist nerves and muscles as compared to an average sprinter.

Excitation and inhibition times are shorter, and with a more forceful ground contact, you will have a longer stride length and thus more “air time”.

As seen in the image above, an average sprinter will show a negative displacement as their center of gravity drops during “air time” or the flight phase. Remember, these guys only take about ~45 strides in a 100m sprint under 10 seconds. (NOTE: I can easily do 45 “bounds” for 100 meters, but it will be well over 10 seconds. Maybe 15 seconds or more. It’s all about covering ground as fast as a possible in a 100 meter sprint.)

The elite sprinter will demonstrate a rise in the center of gravity, which results in a higher hip height. Charlie called this positive displacement or “lift”.

But how is all this mastered? Yes, you guessed it…

Triple Extension…

(I’ll repeat the 3rd time to get my message across) You can’t leave out Vertical Displacement & Lift, Stride Length, Flight Time or Air Time, and Ground Contact in the equation. Why? To quote Charlie Francis, sprinting is the the ability to tolerate the shock of landing determines all that follows. This means properly executed biomechanics (i.e. triple extension & hip height) coupled with the forces striking the ground will result in a faster sprinter, or covering ground faster from increased stride length and fast cadence.

To quote Mike Hurst (read my Friday Five Interview with him here):

Triple Extension facilitates transfer of force through the body into the track and back. Collapsing at the hip, knee or ankle deflects the force and weakens the impulse on the track.

The hip height attained facilitates the level of extension seen at and just before landing in the pictures attached. This greater extension creates a stronger position to resist force deflection at the knee, leading to more efficient transmission of force and a better quality of impulse into and back from the floor.

One of the major factors in sprinting quickly is the ability to cope with landing shock and the resistance to the shock of landing makes all else happen.

If the knee of the supporting leg is bent, it can be more easily collapsed by landing shock. The straighter it is, the stronger a position the sprinter is in to resist “caving in”. The higher position you start from, the more airtime you have to accelerate and straighten the leg on the way back down before grounding contact.

Rapid conversion from landing to liftoff also has implications for tendon stiffness, hence the advocacy of training on soft surfaces (grass, dirt) – at least for volume sessions at sub-max velocity.

Me again.

I know what you are thinking. Usain Bolt is 6 feet 5 inches tall and has the advantage over theother shorter sprinters. But that should not deter you from being a great sprinter. Trinidad’s Mike Agostini, the former World’s Fastest Man from another era, was only 5 feet 7 inches tall, and he had the same stride length as 6 foot tall Armin Hary from Germany. See the image below with Mike on the right and Hary on the left.

Be sure to read and listen to Mike Agostini: The Forgotten World’s Fastest Man PODCAST