Physics (Sprint Velocity)

Velocity is the change in distance over the time it takes to for the change in distance to occur. For example if I were to start running from stationary position (Initial Distance ‘Di’) and run 40 yards (Final Distance ‘Df’) in 4.4 seconds my average velocity for the entire run would be the change in distance (40yards) divided by the time it took to travel that distance (4.4 seconds).

Average Velocity = change in distance (Df-Di) / time (t)

Average Velocity = (40-0)/(4.4) = 9.09 yards/second

 

Average velocity of a distance of that length doesn’t really tell the coach a whole bunch. Yes, it tells us what velocity we have to average to run a 4.4 second 40 yard dash, but sprinting rarely (typically never) occurs at a constant velocity. We are usually either slowing down or speed up and rarely maintaining a speed.

So, to make this more applicable we may want to look at distance splits and the corresponding velocities. The way we can do is this simple, we can look at the same 40 yard run, but this time in 10 yard splits.

 

Why is this beneficial? This can tell the coach whether or not the athlete is accelerating through the entire 40 yards and not ever actually reaching top speed (velocity keeps increasing), it can tell the coach what splits (phases of the sprint) the athlete struggles the most with (poor initial velocities compared to other athletes), and it can also inform the coach whether or not the modality they are testing might be using (a sled or overspeed work) is too heavy or too light.

 

Once we have found the velocity split times we can use these numbers to help us determine the athlete’s rate of acceleration.

 

split times of best 100m sprints (acceleration and velocity can be calculated from above times)

 

Acceleration = (Change in velocity)/Time

 

The changes in acceleration over the splits can tell the coach how fast the velocities are changing, but doesn’t give the coach feedback on top speeds achieved. The differences between acceleration and velocity are important to note, because acceleration is influenced by the changes in velocity, but the speeds of the actual velocity are not necessarily affected by the changes in acceleration.

Example

 

Athlete A: Goes from running 6 yards/second to 8 yards/second in 0.5 seconds

Acceleration = change in velocity / time

Acceleration = (8yards/second – 6 yards/second) / 0.5

Acceleration = (2yards/second)/0.5

Acceleration =4 yards/second/second

 

Athlete B: Goes from running 4 yards/second to 6 yards/second in 0.5 seconds

Acceleration = change in velocity / time

Acceleration = (6yards/second – 4 yards/second) / 0.5

Acceleration = (2yards/second)/0.5

Acceleration =4 yards/second/second

 

Same acceleration for both athletes, but different tops speeds!

 

 

 

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