![]() ![]() The twisties are like this, and often happen under pressure. You're moving way too fast, you're totally lost, you're trying to THINK but you know you don't usually have to think to do these maneuvers, you just feel them and do them. You have to focus on making you foot press the pedal at the right angle, turn the steering wheel just so, shift gears. Suddenly, in the middle of driving on the freeway, right as you need to complete a tricky merge, you have totally lost your muscle memory of how to drive a car. Then sometimes, in stressful situations, you start thinking too much about how to do the familiar thing and you lose it completely: At first everything you do is unnatural and requires deep concentration to learn but once you've got it down, you can do it instinctively, without thinking or even paying that much attention. Your brain remembers how your body feels doing the trick and you gain air awareness. Once you've practiced a trick enough, you develop the neural pathways that create kinesthesia which leads to muscle memory. (In diving, a coach yells "OUT" and you kick your body straight and pray). When training new flips and twists, you need external cues to learn how it feels to complete the trick correctly. ![]() When you're flipping or twisting (or both!) it is very disorienting to the human brain. On Twitter, former gymnast and diver Catherine Burns explained that Biles was likely experiencing a case of "the dreaded twisties". I didn't want to risk the team a medal for, kind of, my screw ups, because they've worked way too hard for that. I just felt like it would be a little bit better to take a back seat, work on my mindfulness. To avoid this, she could open up into a layout position fractionally before landing to slow down her rotation before she makes contact with the ground.Yesterday, world champion gymnast Simone Biles removed herself from the women's team final at the Olympics after not doing one of the planned two-and-a-half twists on her vault and stumbling on the landing. Biles chooses the middle option (pike) – in the video below you can see how she even “over rotates” this vault in competition and needs to take a big step back after landing. Conversely, the tucked position would produce the smallest moment of inertia and highest rotational speed. In the layout position, moment of inertia is highest and the speed of rotation will be at its lowest. These three positions illustrate the concept of moment of inertia, which represents the resistance of an object to rotation. “Piking” means that she bends at the hips and keeps her knees straight, as opposed to a “layout” (extended hips and knees), or “tucked” (flexed hips and knees) position. In Simone Biles’ latest ground-breaking vault, she performs 2.5 somersaults (starting from her hands on the vault table and landing on her feet) in a piked position. So, the direction and speed at which the gymnast leaves the vault table will determine how high and how far they travel, and ultimately how much time they will have in the air to complete the twists and somersaults. ![]() In a vault, the take-off height will always be higher than the landing height, and there is not a lot that the gymnast can do to manipulate this variable – they will always want to be fully extended at the point of take-off and at initial contact with the ground. This trajectory is determined by three factors: (i) how high the centre of mass is at take-off compared to landing, (ii) the angle of projection of the centre of mass, and (iii) speed of the centre of mass at take-off. Even though the movement of the limbs can alter the direction and speed of rotation of the body (more on that in the next section), the trajectory (flight path) of the athlete’s centre of mass is fixed once they are in flight. Air resistance on the body of a gymnast in a competition hall is almost zero, so gravity is really the only force that can change the motion of the gymnast once they take-off from the vault table and it pulls them downwards towards the Earth. The only forces that act on an object (including a human body) in flight are gravity and air resistance. ![]()
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