Sprinting: Projection, Switching and Reactivity
Before diving into specifics of technique and coaching cues, it’s important to first understand that sprinting and acceleration technique can be broken down into three components: projection, switching and reactivity. These three components provide a lens from which to view top speed and acceleration.
Projection refers to how an athlete is projecting themselves, or their centre of mass, through space and concerns the magnitude and direction of the forces being put into the ground. Are they moving upwards, forwards, to the side?
Switching refers to the exchange of the thighs. As one thigh, knee and foot drives down towards the ground, the other thigh, knee and foot drives upwards. This causes the thighs to switch places — the front thigh drives down towards the ground and the rear thigh swings forward.
Reactivity refers to the ground reaction forces that take place when an athlete’s foot touches the ground and concerns how quickly an athlete lands, absorbs and then produces the forces needed to project themselves in a given direction.
When we look at an athlete’s sprinting/acceleration mechanics through the lens of projection, switching and reactivity it becomes easier to understand what’s going on and to provide effective instruction.
The three components are not independent of one another, they form an integrated whole with each component having an impact on the others. Analysing projection, switching and reactivity can help guide training as it provides feedback on key areas of sprinting and acceleration performance.
Some questions I usually consider when analysing sprinting and acceleration are:
Is the athlete projecting themselves forwards, upwards, backwards, sideways and where do we want them to be projecting?
Are the forces being applied in the correct places and directions?
Are enough forces being placed into the ground?
Could the athlete project themselves more forcefully?
Is the athlete switching the legs aggressively?
How high is the heel recovery?
Is the switch punch like with a low heel recovery or is it cyclical with a high heel recovery? Which do we want?
Technical Point: The aim is to be smooth, fast and aggressive when switching the thighs and to go from a punching action with a low heel recovery when accelerating to a more cyclical like action with a higher heel recovery when sprinting in a fully upright position.
How long is the ground contact time?
How long do we want the ground contact time to be?
Is the athlete stiff upon landing?
Technical Point: Ground contact times will be longer during acceleration and shorter during top speed. Stiffness upon landing is key to reactivity, an athlete doesn’t want to waste time or force by flexing at the knee. As soon as the foot hits the floor the aim is to take off and project forward. This is why sprinters perform lots of reactive/elastic training. Reactivity is particularly important during top speed mechanics due to the short ground contact times involved in top speed mechanics.
This article is an excerpt from Jon's e-book The Basics of Speed and Acceleration for Team Sport Athletes which you can download for free on the resources page