Head And Eye Stabilization
An underrated fundamental movement skill
One of the most important physical tasks for any animal is stabilizing the head so the eyes can focus on a target. This is easy enough in a static environment. But during dynamic activity, it's a major challenge. For example, imagine flying through the air at high speed and keeping your eyes locked on a running rabbit. Here’s a demo of the head stabilization skills you will need to catch dinner:
How does the hawk do this? The details are highly complex but we know in a very general sense that the visual system is communicating very quickly with the vestibular system and the muscles that control posture.
Birds are especially good at this. Here's a fun video of a kingfisher, keeping its head rock steady even at its body wobbles around on a reed:
Even chickens are impressive. This looks like CGI:
After seeing this I immediately wondered why chickens bob their heads back-and-forth while walking. The answer has something to do with head stabilization. As their body advances forward, the head stays motionless in space for a millisecond or two, so the eyes can stay remain focused on potential food targets on the ground. At some point the head needs to catch up with the body, so it darts forward quickly in advance of the body so it can hang our for another millisecond until the body catches up, and and so forth.
It's not just birds who have good head stabilization. Here’s an example of a cheetah running after a moving target. The whole spine undulates but the head is amazingly steady:
Keeping the head stable serves a dual purpose – the eyes get a better view, and the vestibular organs remain level, so their sensory information is easier to interpret, making balance easier.
In humans, this latter point is especially important, because we have huge heads balanced on long vertical spines. Any deviation of the head away from a neutral position can have large effects on full body balance.
It's pretty easy to feel the postural effects of having the head look in a different direction from where the body is moving. Try walking in a perfectly straight line, as if you were on a narrow pathway. Then slowly turn your head to scan the horizon left or right. You may notice that it becomes harder to keep a straight line, or that your trunk muscles stiffen to help you do so. It’s even harder if you look upward, or turn the head with more speed.
Even when you walk while looking straight ahead, the head must differentiate from the trunk to stabilize the gaze, because the trunk is rotating and tilting a little bit from side to side. As people age, the head starts to move along with trunk, which may be part of the reason they walk more slowly and with smaller steps, which reduces the acceleration of the head.
The major takeaway here is that head stabilization associated with visual tracking is a very fundamental movement skill that is involved in a wide range of different activities. Here are some ideas for incorporating visual targeting challenges in to your exercise.
While walking or running, scan the horizon left to right and up to down, as if you were on the look out for predators.
If you are doing sprint training, try going as fast as you can in a straight line while looking left or right. If you play a sport like soccer or American football, this is something you will be doing very often in a game.
When you’re doing an agility drill, add a visual challenge, such as the need to track the movements of a ball or an opponent. (The most popular versions are called playing tag or catch.)
There are some activities where gaze stabilization points the way to good technique. In tennis and golf, one of the fundamentals of a good swing is keeping the head steady while the shoulders move. Dancers improve their balance in a spin by keeping their eyes fixed on a specific point. Technique in lateral shuffling gets better if you try to keep the eyes level. When I practice my movement around the squash court, I will sometimes make sure the flow of visual information remains steady and smooth. This means I am minimizing unnecessary accelerations of the head, making it easier to track the ball and stay in balance. This requires coordinated action from head to toe.
I’m sure I’m only scratching the surface of this topic here, so if you have any ideas you'd like to share, please do so in the comments.