Clean vs. Free Takeoff
Many coaches think that a free takeoff means an athlete's foot leaves the ground before their pole strikes the back of the box and that it is essential for a successful jump. However, there a few 6-meter vaulters, the current world record holder included, who consistently step under at take-off.
It has become apparent that the term “free take-off” has been hijacked and associated with the wrong biomechanical action. I would like to propose we revisit this term and better define what it means.
A Free Take-off
Free take-off is better defined as carrying and lowering the pole in the run-up so that the athlete can move freely and independently of the pole. The pole should not lever an athlete's center of gravity forward causing them to be off-balance, lean forward, or stride out as they launch off the ground. If an athlete carries and lowers the pole independently to their center mass, they can better accelerate like a long jumper and launch with more upward momentum, thus increasing both the length and speed of their swing.
In short, a free take-off means you are “free” from being influenced by the weight of the pole.
A Clean Take-off
A clean take-off is better defined as the athlete’s foot leaving the ground before the pole strikes the back of the box. In many circles, this is known as an outside step and it allows the athlete to jump up vertically be in a taller position at take-off.
Keep them Separated
Keeping the terms “clean take-off” and “free take-off” separate is important for coaches and athletes alike. An athlete can certainly have a clean take-off and still be influenced by the weight of the pole, just as another can remain freely independent of the pole and step under.
If world records are being set while stepping both outside and under, then having a clean take-off is not as crucial to the success of the vault as a free take-off, as long as your final step is within an acceptable range (not too far out or under).
Clean Take-off Issues
If possible, athletes should strive for a more outside take-off for a couple of reasons - it is easier on the back and the shoulder of the top hand, and it allows the vaulter to jump up vertically and in a taller position as the tip of the pole strikes the box. However, having a clean take-off may not be the best action for every athlete. One must be able to jump up vertically at the proper angle in order to keep their momentum upward throughout the vault.
The alternative to a clean take-off is for the athlete to step under. Although not ideal, a slightly bent pole while the athlete’s foot is still on the ground can assist the vaulter vertically, albeit at a price - namely a lower plant and shorter swing.
Free Take-off Issues
Sergei Bubka, the former 35x world record holder, World, and Olympic Champion said he was able to keep free from the influence of the pole during the run-up, some of the time.
Indeed, the free take-off may be the most difficult action to master in the pole vault, and as an athlete progresses to longer and heavier poles it becomes problematic. Elite athletes must fully adopt a technique that allows them to remain balanced, centered, and free from the weight of the pole, which can greatly influence speed and launch vectors.
The Equation
Success in the pole vault can come down to a simple equation you can find in any physics book. The equation for calculating potential energy (PE) and kinetic energy (KE) respectively are:
PE = mgx
KE = 1/2 mv^2
where m is mass (calculated from the weight), g is the acceleration of gravity, x is the height off the ground, and v is velocity. Physics states that kinetic energy will equal potential energy, so you can just make the equations equal to each other like this:
mgx = 1/2 mv^2
If you solve for x (height), you get
x = (1/2 v^2)/g
This equation says a lot!
First, notice that mass no longer appears in the equation. In fact, there are only two things left - speed and gravity. Obviously, gravity is constant thus your absolute height will be determined by how fast you run!
Of course, the better your technique the less energy you will lose throughout the vault, but a generality can be made here. Assuming it was possible for two vaulters to have the exact same technical skills, the one that jumps the highest is the one that can run the fastest.
That is why it is so important to perfect your balance throughout the run-up. Your final velocity, balance, position, and launch vectors as you leave the runway are all you can bring to the equation. In a sense, the pole vault is no different than any other event in track and field, where the primary objective is to minimize the loss of energy once airborne.
This article only addressed the difference between clean and free take-off. In the next article, I will present various techniques athletes use to maintain balance through the run, pre-launch, and take-off.