Human Senses - S1.E6 ∙ Balance
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TVTranscript
00:00It keeps us standing, it helps us move and it tells us which way is up.
00:07It's our sense of balance.
00:10And I'm going to give mine a workout that's out of this world.
00:13This lane is used by the Russians to train their cosmonauts.
00:20In a short while it's going to drop like a stone and I'm going to experience weightlessness.
00:32I'm on board what's called the Vomit Common and after a steep climb we're going into free
00:37fall.
00:39My first one, I'm so nervous.
00:43How on earth am I going to cope with an environment that my sense of balance was never designed for?
00:49No!
01:07Tonight we're going to discover the secrets of our sense of balance.
01:11How we can do this and even this.
01:14But then this makes us fall over.
01:19You feel really sick.
01:21Everything's just turning and turning about until you just fall to the ground.
01:26I'm Nigel Marvin and I'm going to reveal why everything we do is an incredible challenge
01:31for our sense of balance.
01:35I'll discover how we keep track of exactly how our bodies are moving even when the world
01:40is spinning around us.
01:44And what it takes to bring it all crashing down.
01:50I've spent my whole life studying animals but there are very few that can tell me about
01:56our strange human sense of balance.
02:00We're one of a very select club of creatures that get about on just their hind legs.
02:08There are only two kinds of animals that spend much of their lives performing that tricky
02:13balancing act of walking on two feet.
02:16Us and a few flightless birds.
02:21And neither of us has the ideal design for it.
02:28If you wanted to design an animal to balance on two legs you wouldn't necessarily end up
02:33with a human being or an ostrich.
02:39An ostrich has to work really hard not to topple over.
02:42A lot of its body weight is hanging over the front of its legs.
02:48Our body mass on the other hand is easier to handle with a nice upright torso with all
02:53our weight directly over our legs.
02:58But our problem is a big heavy head at the top that can tip us over.
03:04And if walking on two legs isn't hard enough we go and make things even more difficult.
03:10What makes life really tough for our human sense of balance is the crazy things we do
03:15with our bodies.
03:23Unlike any other animal we take pleasure in devising bazookas.
03:28Unlike any other animal we take pleasure in devising bizarre ways to test our sense of balance.
03:38And because we do all this it's a monumental challenge to keep track of where we are at all times.
03:50The world can be a pretty confusing place.
03:54Which way are we moving? Which way are we spinning? Which way is the right way up?
04:01What exactly is going on?
04:06In order to keep control you have to know how your body is moving through space.
04:11And when you're a stuntman like Mark Cass being aware of your own movements is vital to the job.
04:18Mark I mean your coordination, your balance systems, you've got to use them with pinpoint accuracy haven't you?
04:24As we're doing now.
04:26Yeah absolutely. I mean it's really important for every stuntman to have good body coordination,
04:31know where they are in space. Otherwise it could be a matter of life or death.
04:35As if you're spinning in a car or dropping from a helicopter.
04:38Absolutely.
04:41So how do we sense which way our body is moving?
04:45For that basic information we rely on a set of special balance organs deep within the ear.
04:53This series of tubes and chambers, no bigger than a pea, monitors every move made by our head.
05:00So, when we take off.
05:06Or skip to a halt.
05:10Or go into a spin.
05:15These movements are sensed within the inner ear.
05:20The tubes are full of fluid.
05:22Inside the tubes there are tufts of microscopic hair cells.
05:27When we move our heads the fluid moves and the hair cells are bent.
05:31They send nerve signals to the brain.
05:34The tubes point in three different directions and that's how we can sense movement in three dimensions.
05:41Some moves, well they get the whole system going.
05:45Is this it Mark? Here you go.
05:49The balance sensors in the ear tell us one other vital thing.
05:52Which way is up?
06:10And which way is down?
06:19Thanks Mark, well done.
06:21You don't have to throw your body around that violently to test your balancing systems.
06:26Sometimes even standing upright can be a challenge.
06:32Getting around on two legs means we need to know what virtually every inch of the body is doing.
06:38So walking is an incredible challenge.
06:46Most of the time we're actually balancing on one foot.
06:50As we move almost every muscle in our body is involved in a furious battle to stop us from toppling over.
07:02So besides the balance organs in the ear we need sensors in our limbs and torso to let the brain know what the body is doing.
07:12Within a fraction of a second the brain sends out millions of signals to the muscles to make corrections that keep us balanced.
07:21But we're actually born without any ability to balance upright at all.
07:27We have to learn it through trial and error.
07:34And it takes years before the information between our limbs and our brain is processed fast enough so it all happens smoothly.
07:42Eventually walking becomes second nature.
07:45But it's such a complex operation that even the tiniest change can upset everything.
07:51Like puberty.
07:57With our bodies growing so fast the nerve circuitry in our brains can't keep up with the changes to the body.
08:05The wrong signals are sent to the limbs and so for a while we're gawky and clumsy.
08:19When you realise just how difficult walking is it's no surprise that anything a little bit more tricky takes a phenomenal amount of effort.
08:27It's not just our bodies we have to balance on our two legs, we also pick things up and carry them around.
08:35Doing this creates an even greater challenge for our sense of balance.
08:39The secret of our success is that we actually prepare ourselves before we do it.
08:46Take a look at this. We've set up a little workout.
08:49We're going to run 10 laps around the track.
08:52It's just as easy as a little exercise.
08:55We're going to run until we stop.
08:59And then run again.
09:01And then run again.
09:03And again.
09:05Take a look at this, we've set up a simple test with a suitcase, some weights and a group
09:13of unsuspecting volunteers.
09:17First the suitcase is filled with around 12 kilos of weight.
09:25The volunteers are asked to pick up the suitcase and repeat the movement a few times.
09:31Then we take them out of the studio and ask them a question that has nothing to do with
09:35the experiment.
09:36So it's actually an observational test, did you notice the colour of the cameraman's t-shirt?
09:43Erm, no.
09:44And while the volunteer is preoccupied, we replace the weighted suitcase with an empty
09:50one.
09:51So we'll go back to the studio.
10:01Because they don't know that a switch has been made, they automatically balance themselves
10:06for a heavy case.
10:17So they falter, but they don't fall over.
10:22Amazingly it takes just a fraction of a second for our sense of balance to detect what's
10:28wrong, adjust and keep us upright.
10:36With our top heavy design, moving around on two legs is a fantastic balancing act.
10:44We use sensors in the ear and throughout the body to guide constant minute adjustments
10:49to thousands of muscles.
10:51But there's one other vital component to our sense of balance.
10:59To see that vital component in action, I've come here to the Circus Centre in San Francisco.
11:11It's awe-inspiring what these acrobats can do and some of these manoeuvres, they take
11:15years of training.
11:17But I've come to see a stunt that will test even their sense of balance to the absolute
11:22limit.
11:24We've asked these acrobats to perform one of the most difficult stunts in their repertoire,
11:29the human tower.
11:30It's going to take four people, nerves of steel and a very strong foundation.
11:37And you're the base man, you know, that's a pretty tough job, what do you have to do?
11:42Well basically I have to be the floor, or at least do my best to be the floor.
11:47So I have to be as solid and as strong as possible and provide the people on top of
11:52me the best foundation that I can.
11:53So let's see this in practice then, let's see what you and your friends can do.
11:57Okay.
11:58It's a team work, everybody should be working together, back strong, legs strong, keep a
12:05tight, stay tight, okay?
12:11Good luck.
12:12Alright, let's do it.
12:13Thank you Terry.
12:14You okay?
12:15Are we ready?
12:16Yeah.
12:17I'm just going to hang on.
12:20As each person is added to the tower, the problems multiply.
12:25If the tower is to stay standing, everyone has to stay as perfectly still and upright
12:30as possible.
12:31Shoulder and back, legs, special legs.
12:36It's a hair raising test for their sense of balance.
12:42Every detail supplied to the brain by the sensors in the inner ear and the limbs is
12:47crucial.
12:48Stomach.
12:49But it's actually something else that's keeping Alec's team standing.
12:57Neither the movement sensors in their heads or their limbs can stop the really minute
13:01wobbles.
13:02For that, they need their eyes.
13:06Their eyes tell them when they're swaying even slightly, because they can see the rooms
13:10moving.
13:13So how well will they manage without their eyes?
13:16To find out, they've agreed to build the tower again, but once they're up, we're going to
13:21turn out the lights.
13:25They won't be able to see anything, but we'll be able to, with the help of this thermal
13:30imaging camera.
13:31Okay, Alec, this is the moment of truth.
13:34Are you steady?
13:38The troop is going to attempt a tower of three.
13:41Okay, are you steady now?
13:45There we are, a tower of three.
13:51Okay, totally controlled, totally poised.
13:55Okay, three, two, one, go.
14:03Can these masters of balance keep the tower standing in complete darkness?
14:07I hear the feet shuffling already.
14:10You've gone, that didn't take very long.
14:18Bad luck, but I reckon this is still a world record.
14:21As far as we know, no one has ever maintained a tower of three in the dark, because it's
14:26so difficult to balance without the help of your eyes.
14:31As far as I'm concerned, that really is pretty good proof that the balance sensors in our
14:36ears and in our limbs, they collect the basic information.
14:40But when it comes to really precise manoeuvres, they need a little help from our eyes.
14:47In fact, we all rely on vision when it comes to keeping our balance.
14:52Standing on one leg is a bit tricky, but with eyes open, most of us can do it for quite
14:56a while.
14:57But what happens when you close your eyes?
15:10You quickly discover how much vision is keeping you upright.
15:38Our sense of balance is an extraordinary combination of three separate sensory systems
15:43in our ears, our limbs and our eyes.
15:54When they're all working together in harmony, we can even stay upright in the most testing
15:59situations.
16:09But all of the time, our balance system operates right at the limit, so even the slightest
16:15malfunction can send us crashing to the floor.
16:25When we move around, the inner ear is normally superb at sensing the movement, but it's
16:31actually quite a delicate system.
16:37These junior school children from West London have volunteered to be thrown off balance.
16:44Games which involve running about and making quick turns are no problem, but change the
16:48movement slightly and it's a very different story.
16:58If you keep spinning round and round, the fluid in your balance organ starts to move
17:03round and round too.
17:05The problem starts when we stop.
17:26Well at first you feel like you're moving around with the earth, but when you stop the
17:30earth seems to move round without you.
17:37We may have stopped spinning, but the fluid in the ear is still moving, so the brain thinks
17:42we're still turning round and round.
17:44We feel really sick, everything's just turning and turning about until we just fall to the
18:00ground.
18:01But it's not just children's games that throw us off balance, the over 18's have ways too.
18:14The world moves in a mysterious way if the signals from the balance centres in our brain
18:19are disrupted or delayed in any way, and there's a liquid that's very good at doing just that
18:25– alcohol.
18:29If we drink enough alcohol, it starts to disrupt the nerve signals in the cerebellum.
18:35That's the brain's balance centre.
18:38It's the part of the brain that coordinates all our movements and our muscles particularly
18:42in the legs, and once you start affecting the cerebellum, the tendency is to sway all
18:47over the place.
19:03Alcohol slows down the nerve signals from the brain to the legs, which destroys our
19:07sense of balance.
19:09So before the advent of the breathalyser, the test for drunk drivers was walking the
19:13line.
19:19But alcohol can have a second effect on our sense of balance.
19:23Drink enough of it and it even starts to mess with the balance organs in our inner ear,
19:28which creates a very unpleasant sensation.
19:32It's called the screaming horizontals.
19:34It's when you put your head back, particularly if you have your eyes closed as well, that
19:38suddenly the room seems to take off.
19:40The world starts to lurch and it makes you feel quite sick and disoriented.
19:48The alcohol in the blood gets into the inner ear, affecting the tiny hair cells which sense
19:53movement.
19:54That tricks the brain into thinking that movements are much more exaggerated than they are.
20:02So a small move feels like a complete 360 degree headspin.
20:09I'm a little bit dizzy to be perfectly honest, but apart from that, not too bad.
20:24We rely on our separate balance systems to work together to keep us upright, but what
20:30happens if they're each telling us different things?
20:58Out here in the North Sea, it's hard work putting one foot in front of the other, let
21:02alone keeping down lunch.
21:06These conditions, they really aren't great for a pleasure cruise, but they are perfect
21:12if you want to learn about seasickness.
21:16Even though I'm being chucked around, the sensors that make up my sense of balance are
21:20all working perfectly well.
21:23So why do I feel queasy?
21:25And why, if I go below deck, is it even worse?
21:33Who better to explain why than former Rear Admiral Frank Golden?
21:38Frank, so why is it people feel more seasick below deck?
21:43The fluid in the inner ear is sloshing around, telling the brain that there's violent movement
21:47taking place, but sadly that's not being confirmed by the eyes.
21:51The eyes really are perceiving everything as fairly static.
21:55I'm looking at a man who's barely moving, but my inner ear can sense that the boat is
21:59crashing up and down.
22:01The different components of my sense of balance just can't agree, making me feel awful.
22:06Is it the same principle when people try to read in a moving car and get car sick?
22:11Absolutely identical situation, another conflict of sensory information going to the brain.
22:16Yeah, this, I'm sorry, I'm feeling a little bit nauseous, can we go up on deck?
22:24Back on deck, I can see the horizon bouncing around, which confirms just how much we're
22:29moving about.
22:32Now all the parts of my balance system are telling me the same thing, and I feel much
22:37better.
22:38Believe it or not, there's another situation that tests our sense of balance even more
22:45than these rough seas.
22:47We make life hard by throwing ourselves around like no other animal on the planet.
22:54Even our ability to walk upright is a massive achievement for our sense of balance.
23:00But we don't stop there, we're always testing how far we can go, and we push ourselves even
23:08further by going where no creature on earth was ever meant to go, by venturing into the
23:15weightlessness of space.
23:21But if our sense of balance is so precarious, how on earth will I deal with weightlessness?
23:27To find out, I've come to Star City in Russia.
23:31This is a Russian jet plane that's been modified for a very special purpose.
23:36When this thing gets into the air, it does something that's extraordinary.
23:44For decades the Russians have been using zero gravity flights to prepare cosmonauts
23:49for life in space.
23:54The conditions are so severe, unless your body is up to scratch, you aren't allowed
23:59to fly.
24:02How am I?
24:05Like a cosmonaut, thank you.
24:10Now I've passed the medical, there's no turning back.
24:14Every little kid wants to experience what it's like to be an astronaut floating in space.
24:19This is going to be a very special flight, I'm nervous about it.
24:23Some people in this plane, they get so sick they've got to go to hospital and be on a
24:28drip because they lose so much fluid when they're being sick.
24:37To create zero gravity, the pilot has to execute an enormous arc at 25,000 feet.
24:47First the plane makes a steep climb at full throttle, then the power's cut and the plane
24:54arcs over into a dive, and everything on board becomes weightless.
25:03The steep climbs and nose dives are so ferocious that according to some cosmonauts, a trip
25:09on the Vomit Comet is tougher on our sense of balance than space itself.
25:13This is going to be like learning to walk again, my first one, I'm so nervous.
25:23Wow, look at this, I can't feel my arms, I'm feeling so, it's like I don't know where my
25:35hands and arms are, and I'm feeling, ah, squeezy too.
25:41Will my balance systems ever, ever get used to this, oh my goodness.
25:50To find out if they will, I'll be lifting off several more times.