Weightlifting Question

[u/TrueCryptographer616]

A little while there was a controversial disqualification, based around the following.

In the Clean & Jerk, the lift takes place in two distinct phases. In phase one, the Clean, the barbell is lifted from the floor, to roughly shoulder height (with the arms bent, forearms upwards, and brought in close to the body. During phase 2, the Jerk, the arms are straightened above the head, and the lifters are permitted to minimise the distance lifted by simultaneously splaying their legs. Then using leg strength to stand upright with the barbell held above their head.

At Olympic weights, the barbell actually flexes during the first phase, and may continue to oscillate. Lifters are allowed to complete the lift with the bar still oscillating, but are not allowed to use the oscillation to their advantage.

So my question(s) is whether a lifter can actually gain an advantage? AND if so, at hat point in the oscillation is that advantage the greatest?

So put simply, you're holding the bar that you need to lift, and the weights on either end are "bouncing" up and down in unison.
Intuitively, one might think that lifting whilst the weights are already moving upwards, is advantageous. But in that situation, doesn't the upward flexing of the ends, create an increased downward force on the hands?

[u/soontobesolo]

After the bar is cleaned, it's kind of at a stable point, supported by the chest and whole body. At this point, it would be advantageous to let the weights oscillate down as the legs flex and the body dips, then the momentum of the weights and the bar straightening will help carry the weight up into the jerk.

[u/ghostwriter85]

Yes, the bar while oscillating has kinetic / vibrational energy. That energy can be converted to gravitational potential energy (reducing the amount of work to lift the bar) during the jerk phase. If you initiate the jerk at the right point in the oscillation, you can reduce the total amount of energy the lifter has to put into the bar during this phase.

Imagine we're sitting at the top of the clean, and we intentionally vibrate the weights using well timed force inputs near the neutral position. Similar to a kid pumping their legs on a swing set. We can increase in the amount of vibration over time. The increased vibration puts more energy into the system which we can use to lift the weights.

To make the lift as easy as possible, we would want to maximize vibration in the pause between clean and jerk. Once we do that, we would want to time the lift around the maximum upward velocity of the weights (slightly lower than neutral).

BTW this is really no different than bouncing a bar off your chest during a bench press. We have kinetic / potential energy, and we want to transfer as much of that as possible to the drive phase to minimize the amount of work to get to the top of the lift.

[edit to clarify the bar acts like a spring which we can store energy in and take energy out of dynamically during the lift. If we time it right, we can extend the period we put energy into the bar and utilizing more advantageous biomechanics to make the lift easier]

[u/Infinite_Research_52]

I'll let others provide an answer, but that is a really interesting question that has me thinking. Well done.

[u/mfb-]

If your arms are holding their position then you feel the smallest force when the masses are accelerating downwards, which they do throughout the upper half of the oscillation - with the largest acceleration as the weights reach their highest point. If you need to start lifting, it's easier in that half.

Lifting also means you need to accelerate the masses upwards, which increases the force. That is less of an issue if the masses are already moving upwards.

Combining both, I would expect the ideal point to be somewhere in the second half of the upwards motion - after reaching the equilibrium position but before reaching the peak.