At 21:00 tonight, Quan Hongchan and Chen Yuxi staged the "Splash Disappearance Technique" again in Paris, and won gold and silver without any suspense! With a standard tumbling action and a near-perfect splash, the Chinese diving team once again showed its absolute strength.
Standard! Agence France-Presse
In addition to diving, spins are also common in competitive gymnastics, trampoline and other events, and the high score criteria include perfect flips in the air, and finally landing firmly or holding down the splash. In addition to the ability to control body posture, vision is also one of the important conditions to assist the athlete to find the right position and prepare for a precise landing during the flight phase.
So, where exactly are the athletes looking when they are somersaulting in the air?
Visuals are important, but the first half is not the focus
Let's take a look at the world as the player sees when he does the most basic backflip, which is the process of jumping and rotating 360° backwards around the lateral axis of the body before landing on the ground. A smooth landing of this movement requires visual aids, especially in the second half of the flip.
One study used lights on and off to control the gymnast's vision, comparing backflips in different conditions. The results showed that athletes landed more stably with the lights on and only the second half of the day than when they couldn't see anything or only turned on the lights in the first half of the race. This means seeing your surroundings in the second half of a backflip to help you orient and prepare for landing.
Since vision is important, researchers then recorded in detail the backflip posture of the 11 gymnasts, the position of their heads, and the direction of their gaze. From the take-off to the time of landing on the trampoline, the camera at the athlete's forehead captures the scene like this:
1-5 is the process from take-off to fall, the upper row is recorded by the side camera (the blue line indicates the direction of the line of sight), and the lower row is the image recorded by the player's forehead camera (the red dot indicates the fixation position)丨Reference[1]
In the first half, the gymnast's eye movements are different from the take-off to the ground where the body is basically parallel to the ground (Figure 1-2 above). Four of the athletes looked up immediately after the jump, staring at the ceiling; 4 athletes looked down in the first half of the movement; Three more people closed their eyes immediately after jumping.
Combined with previous research, vision in the first half of a backflip may be less important for controlling movements.
In the second half of the journey, keep an eye on the landing point
But in the second half of the race, all the athletes' eye movements are very similar, all glued to a fixed point on the trampoline and remain fixed until they land.
That is, after reaching position 3 above, the athlete's eyes will move significantly upwards until they find a fixed fixation point on the trampoline, which usually occurs when the entire backflip is 60% complete (Figure 4 above). At this point, the athlete's forehead camera appears on the far left of the image below.
From the time the fixation is found to the time it falls back to the trampoline, the red dot indicates the fixation position丨References[1]
Then, as the body gradually turns back to an upright position, the head is also rotated back, and the image in the camera shifts from the trampoline to the mat in front of it. At the same time, the athlete's eyes are turned in the opposite direction to the head, and the gaze keeps moving downward, so that the gaze position remains at the red dot in the picture above until it lands back on the trampoline.
During the entire backflip, the athlete's gaze stays on the red dot for more than 300 milliseconds, which is achieved by counteracting the head rotation with the downward turn of the eyeball. As for the location of this fixing point, it is located on average 143 cm in front of the landing site. Although the landing spot is slightly different from time to time, most athletes will keep their eyes on the red cross in the middle of the trampoline and the front edge of the bed.
In this study, gymnasts at the national level started to focus on the fixed point at 47.1% of the time they completed the backflip, while the gymnasts at the higher level started at 52.9% with a delay of 78 milliseconds. This may be due to the fact that top athletes require less visual orientation time and are more stable in their movements and require fewer adjustments.
Of course, the movements in a real game are much more complex than a single backflip, but athletes often try to keep their eyes fixed on a specific location, such as a trampoline, the floor on a gymnastics field, or the surface of a diving pool, using the information provided by vision to adjust their body posture to better perform aerial maneuvers and locate landing points.
Direction of gaze during more complex turns (black line)丨Reference[4]
Keep an eye on it, is it born or practiced?
The above phenomenon of moving the eye to counteract head movements is similar to the innate vestibulo-eye reflex, which is one of the important reflexes that keep the vision stable when people are moving.
If you hold the camera to your forehead while walking, you will notice that the recorded image is very shaky and you can't distinguish the object in front of you. In fact, the reason why the eye is basically stable is that the human body automatically turns on the "anti-shake function": the receptors in the inner ear are used to distinguish the direction and amplitude of movement, and this information is transmitted to the muscles around the eyes through the reflex pathway, so that the eye ball and the head move in the opposite direction, counteracting the shaking caused by walking.
头向一侧转动时，眼睛自动转向另一侧 | Solvelearningdisabilities
In addition, there are many other adjustment systems that connect the eyes, head, and body to help people maintain a smooth, clear, and smooth vision of the object of interest during a variety of movements, as well as to position the body and adjust posture.
Eye movements are not controlled by a simple reflex or brain instruction, but are the result of multiple sensory inputs, calculations, and complex processing. In some cases, the various systems act in contradictory directions to the eyeball, and active control is needed to determine the dominant function.
Therefore, the natural function of the human body is enough to maintain visual coordination when doing simple movements, but for the control of complex movements such as backflips, it takes long-term and repeated exercises to hone each system in order to finally achieve perfect results.
bibliography
[1] Natrup J, Bramme J, de Lussanet MHE, Boström KJ, Lappe M, Wagner H. Gaze behavior of trampoline gymnasts during a back tuck somersault. Hum Mov Sci. 2020;70:102589.
[2] Davlin CD, Sands WA, Shultz BB. The role of vision in control of orientation in a back tuck somersault. Motor Control. 2001; 5(4):337-46.
[3] Natrup J, de Lussanet MHE, Boström KJ, Lappe M, Wagner H. Gaze, head and eye movements during somersaults with full twists. Hum Mov Sci. 2021;75:102740.
[4] von Laßberg C, Beykirch KA, Mohler BJ, Bülthoff HH. Intersegmental eye-head-body interactions during complex whole body movements. PLoS One. 2014; 9(4):e95450.
Source: WeChat public account "Guohu"
Author: Dai Tianyi
Editors: Deng Rumeng, Li Xianghe (intern)
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