• helenbayne

Defeating Gravity

Weightlifting is one of those iconic Olympic sports that few people pay attention to outside of the Games. I have dabbled in the sport recreationally over the past few years and, as I work towards my goal of a bodyweight clean and jerk, I have a new appreciation for the strength and technical prowess of the elite competitors that lift ~2.5 times their body weight.


The sport of weightlifting demands that athletes lift a heavy barbell from the ground to overhead in two different types of lifts. In the snatch, the arms need to lock out overhead in a single movement, whereas in the clean and jerk the athlete first lifts the bar onto the shoulders and then presses it overhead.


In a classic paper in the British Journal of Sports Medicine in 1970, D. W. Grieve described weightlifting as the “art of defeating gravity”. The moment in each of these videos when the athlete’s feet leave the ground makes this apparent. Can you imagine not only lifting this weight off the ground, but managing to achieve a brief moment of flight? Another thing to watch out for in these clips is how the athlete manipulates the motion of (a) the barbell through the air and (b) their bodies around the barbell to complete the lifts. The path that the bar travels is not a straight vertical line, there is a small amount of forwards and backwards motion as the athlete negotiates the various phases. As the barbell is lifted off the ground, past the knees (the first pull) and up to mid-thigh level (the transition phase) it typically moves backwards towards the lifter. As the hips and knees extend rapidly (the second pull), the bar moves up and forwards. It continues in this direction for the first part of the turnover phase as the athlete starts to move under the bar. As the bar reaches its maximum elevation it again moves backwards and then descends until the catch, ending directly above the middle of the athlete’s feet for optimal stability.

In performing these manoeuvres, the athlete is doing mechanical work on the bar – applying a force that moves an object a certain distance. This gives the bar kinetic energy (EK), which is a function of its mass (m) and velocity (v) and can be calculated with this simple equation: EK = ½.m.v^2. The bar also gains potential energy because of its change in height. Vertical velocity peaks at the end of the second pull, and there is a common misconception that the bar effectively becomes a projectile at this point, slowing down only under the force of gravity while the athlete moves under it in time to receive the load on its way down. However, the lifter actually still needs to do some work on the bar after maximum velocity in order to successfully complete the lift. The secret to optimising an individual athlete’s performance is to develop the necessary kinetic energy with just enough vertical velocity and therefore maximise the mass of the barbell. Dr Kristof Kipp discussed this in detail in a recent online presentation, which is highly recommended viewing for those who want to dig deeper into the physics.


The competitors that you will see at the Olympics operate with near perfect technique. Sometimes a useful way to explain good mechanics is to look at an example of an athlete that is less proficient. So, I present to you my own novice attempt at a 59 kg clean (~95% of my max), displaying the path of the bar and its vertical velocity with a graph of the vertical displacement and velocity below.



You’ll notice that this is a power clean (meaning that I don’t catch the bar in the full squat position that you’ll see in the Olympics). Receiving a heavy load in a deep squat requires lower body strength that I don’t have in order to stand up (working on it!).


Now for some critical self-assessment:


The bar path is generally the correct shape. However, I’d like to extend the period where it’s traveling towards me for a little longer. This will enable me to get into a stronger position at the end of the transition, so that the bar finishes closer to my hips instead of just above the knees as I start the second pull. I can improve the first pull by keeping my hips lower / slowing the rate of knee extension, which would make the slope of the backwards bar path off the floor a bit more gradual and should also help the transition phase.


The maximum vertical velocity of the bar is 2.2 m/s and this happens when the bar is at a height of just over 1 m. The bar travels a further 40 cm to a maximum height of 1.41 m (~83% of my standing height), of which 25 cm can be attributed to projectile motion and the remainder requires additional work on the bar. Elite weightlifters performing maximum lifts will hit velocities of between 1.65 – 1.85 m/s and achieve up to 30 cm of bar elevation after maximum velocity. This suggests that I could theoretically lift a heavier bar, resulting in a lower velocity and maximum height. However, I might not (yet) have the (i) technical skill to move under the bar more quickly, and (ii) the confidence and/or strength to receive the bar in a deeper squat position.


While I continue to work on my own form, I will be admiring the supreme Olympic weightlifters competing in Tokyo. Unfortunately, there aren’t any South African representatives at these Games, but that will hopefully change in future as programmes like Lifting Dreams take the sport to new communities.



References

- Bottcher J, Deutscher E. Biomechanische ergebnisse zur bewegungstechnik im gewichtheben (reißen) [Biomechanical results on movement technique in weight lifting (tearing)]. Leistungssport [Competitive sports]. 1999; 29, 55–62. Retrieved from https://leistungssport.net/jahresuebersicht/

- Chavda S., et al. Weightlifting: An applied method of technical analysis. Strength and Conditioning Journal. British Journal of Sports Medicine. 2021. doi: 10.1519/SSC.0000000000000614

- Garhammer J. Power production by Olympic weightlifters. Medicine and Science in Sports and Exercise. 1980; 12, 54-60.

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