HJ: First, could you briefly explain the kind of experiment you conducted recently?


AM: There are clothes made to fit the human body, but the problem is that they often restrict movement. Clothes that limit how my body moves make me crazy! When you're riding a bike and can't move the way you want to, it can be really frustrating.

So, I thought it would be great to have clothes that move with the body. I realized that skin stretches and contracts significantly. If clothing could stretch as much as skin then movement would feel effortless.  At first, I tried marking my skin with a pen to see how many centimeters it would stretch.


ON: So, you've actually tried that experiment before?


AM: Yes, I did, but I couldn't understand it that well. I also had a limited range where I could reach with the pen, so I wondered how it worked for other people.


ON: Exactly. You can only mark the parts of your body that you can see.


AM: I started to think about how skin stretches and what clothes should be like, and instead of relying on just a feeling, I thought it would be better to measure it.


HJ: A quick question here. What do you usually do, Oghihara-sensei?


ON: I do a variety of things. I originally became interested in walking and wanted to know how humans manage to walk so skillfully. The human body is complex, made up of about 200 bones and hundreds of muscles that allow us to move in space.

The reason we can do this is because our nervous system performs calculations to move our muscles efficiently. That's why we can walk, whether it's on stairs or anywhere else. Since I originally studied mechanical engineering, I believed that if we could better understand how the body works, we could improve machines and also help patients who have trouble walking, or people whose motor abilities decline with age.

It's an important theme both in engineering and medicine, and I started researching walking during my student years.

From there, I began investigating various aspects of the relationship between the human body and movement, and this time, thinking about how the body interacts with skin and clothing is something I hadn't considered before talking with Mike. But it's really interesting, so I've been experimenting with it.

Earlier, Mike mentioned that he used to mark his body with a pen, but when measuring human or animal movement, there's something called motion capture. We attach markers to the body, detect their position using multiple cameras, and measure 3D movements. You see motion capture on TV, especially during Olympic years.

AM: Thanks to that, I was finally able to measure how much the skin stretches.


ON: By attaching those markers to the body, we could accurately measure how the skin stretches and contracts. We did electronically and mechanically what Mike tried doing by marking his body with a pen.

As Mike said, what was surprising was how much the skin stretches and contracts. We haven't gotten detailed numbers yet, but it stretches up to about twice its original size in some places. When a joint bends, the skin stretches gently and then contracts back. But it doesn't sag excessively, does it? That's what we found interesting during the initial experiment.


AM: While talking with Oghihara-san, we discussed creating a long chain-like line and connecting it to measure stretch mathematically. I didn't originally think that way, but the overall movement of the body is fascinating.

Even though our skin does amazing things, we usually aren't conscious of it at all.


ON: Right, we don't think about it. But because skin stretches and contracts so much, we can bend and reach, giving us such a large range of motion. If our skin were made of fabric, we wouldn't be able to bend at all.


ON: It's something we take for granted, but I'm reminded of it.


AM: There are stretchy materials in clothing, but when you use a lot of them, I don't like the rubber band-like way they feel. They also deteriorate quickly.


ON: I see.


AM: After a year or two, they lose their elasticity. And now, both in clothing and manufacturing industries we are in an era where we need to make things that last longer. I thought, if we could make clothes that allow for easier movement without using stretchy materials, that would be ideal. But first, I didn't know how much skin actually stretches.


ON: That's where the whole process began.

HJ: So, considering how much skin stretches, are there many people studying this topic?


ON: In the past, I've seen experiments where grids were drawn on the body to measure how much it stretches and contracts, mainly to analyze foot deformation.

In the medical field, for example, when creating artificial skin or performing skin grafts, how much the skin can stretch and contract is important to consider. I'm not very familiar with that area, but when you mention it, it's definitely important. It's so obvious that we usually don't pay attention to it in daily life.

It's true that skin has a surprising amount of elasticity.

I think it's because we don't fully understand the precise mechanisms of living organisms. It's not just about structure but also how the brain controls everything. But still, the structure is fascinating.


HJ: So, structure is key, right?


ON: Yes, exactly. For example, in cats the thumb is parallel to the other fingers, so they can't hold things. We humans can use chopsticks because of something called thumb opposition, where the thumb can face the other four fingers. This is a characteristic of primates. Even if a cat's brain developed and could control its movements, without the right structure, it can't perform certain tasks. So, structure is essential for creating sophisticated movements.


HJ: Sometimes, we see videos of dogs standing on two legs. Is it structurally possible for them to walk like that?


ON: It's not impossible, but it's definitely pushing their limits. It's like asking us to walk on all fours. We could do it, but it would be uncomfortable. Our bodies are simply structured for two-legged walking.


AM: There's also the argument that humans tend to suffer from back pain, so is standing on two legs really ideal?


ON: True, some say that back pain is a result of walking on two legs because it puts a strain on the spine. On the other hand, the human spine has a slight S-shape, unlike the C-shaped spine of four-legged animals, which helps us walk upright. Our spine is somewhat adapted for upright walking.


AM: So, the spines of four-legged animals aren't curved like an S?


ON: Exactly. It's actually not easy to walk efficiently with an S-shaped spine. Additionally, human arms are relatively short compared to our legs.


AM: Humans used to walk on all fours, but now we walk on two legs. What do you think the future holds? Is there a better way of walking?


ON: Evolution doesn't happen with a specific goal in mind; it's more of an outcome based on circumstances. So, what happens next depends on the environment and a lot of chance. Honestly, we don't really know.


AM: It depends on what kind of pressures we face, right?


ON: Yes, exactly. Humans developed civilizations that overcome some natural pressures.

Take sickness, for example. In the past, people would die from certain diseases, and only those with resistance would survive. That's part of how evolution works. But now we have technology and culture that combat those pressures.

This technology changes the direction of evolution, which makes things even more complicated.


AM: So, could that stop evolution altogether?


ON: I'm not sure about that.

The history of humanity is shaped by how we've adapted to our environment through evolution. While we don't fully understand it, our bodies have adapted to walk on two legs, and that's a fact.

Our bodies are highly adapted for bipedal walking, but whether that's the best form is uncertain. After all, walking on two legs does cause some problems. For example, our pelvis is bowl-shaped, supporting the organs above it.

On the other hand, dogs, cats, and even other primates don't have that structure. That's why humans are more prone to conditions like hernias, where organs can protrude through weak spots in muscle or tissue.

ON: Humans are the only primates that have developed bipedal walking as a unique mode of movement, and our bodies have many adaptations for this. On the other hand, primates evolved in the trees.

That's why humans also have a wide range of motion in our shoulders and around our legs.


AM: So, our shoulders move so freely because we adapted to moving in trees?


ON: Cats and dogs can't rotate their shoulders as much as humans. Living in trees expanded the range of motion in our shoulders, which in turn allowed our bodies to grow larger and enabled us to hang from branches.

A wide range of motion in the shoulders is actually a significant characteristic of ours.

There's a study that shows chimpanzees can throw overhand, but their control isn't great. When they want to throw accurately, they throw underhand. Humans, on the other hand, can throw overhand. Of course, being able to throw accurately from overhand involves the brain and how it controls movements.


AM: That's fascinating.

When you compare humans to other animals, you can start to see our unique features.

AM: I sometimes think about how people in the past, like Japan's old couriers (hikyaku), covered incredible distances in a single day, or how I've heard stories of people carrying large items on their heads without holding them with their hands.

There are many things people in the past could do that we can no longer do today.


ON: I feel that this is more due to differences in lifestyle than biological differences. If our survival depended on it, we'd probably be able to do those things too.

Carrying heavy items on the head is actually mechanically efficient. When you carry things in your arms, the weight's gravitational pull is away from the center of your body, which causes you to lean forward.

To counterbalance that, you have to use muscle strength, which is tiring. But when you carry things on your head, it's mechanically easier.


AM: It's easier?


ON: Movement often follows what's easiest for the body, and physical efficiency plays a part. But for humans, movement is also shaped by culture. In other words, people do something a certain way because everyone else does.

I think cultural factors do influence how we move.

While carrying things on the head might be easier, in today's Japan, there's an unspoken understanding that people just don't do that.


AM: If someone carried a bag on their head today…


ON: In Japan people would probably think, "What's wrong with that guy?"


AM: For example, in the past people used to have larger jaws. But when pottery was invented and people started boiling food, they no longer needed such large jaws to eat.

So, I've heard that human jaws have gradually become smaller. It's interesting to think about the relationship between the things we make and our bodies.

It takes quite a few years for the body to undergo any real change.


ON: Yes, that's true.


AM: Now that I think about it, we're making all kinds of things, but some of them don't really suit our bodies.

Like the way using a computer can cause eye strain from blue light.


ON: There are many artificial objects that aren't well suited to humans. For example, when cars were first made, comfort wasn't even considered, and safety wasn't a priority.


AM: Just that they worked was probably amazing.


ON: Yes, initially, the fact that they moved was enough. Over time, though, measures were taken to make cars more comfortable and safer, leading to the vehicles we have today. Traffic accidents have decreased, and passenger comfort has greatly improved.

But that doesn't mean it's the end. At first, products are developed with only one aspect in mind, and then they improve over time. That's how we've arrived at where we are in modern civilization, I think.

AM: Sometimes I wonder if it might be better to go back to older ways, like with shoes.


ON: Yes, some say barefoot is better.


AM: While it's important to protect our feet on construction sites, when walking on regular streets, shoes like sandals that let our feet move more naturally and breathe might be better, using foot muscles more efficiently.


ON: But if you asked us to go barefoot now, it would be too painful, and we wouldn't be able to walk.

It's the same with the way we walk. We've become accustomed to wearing shoes all the time.


AM: Have our foot muscles changed too?


ON: Yes, the muscles, and the skin wouldn't be able to handle it anymore. Plus there are our sensory receptors. The soles of our feet have sensors that detect how much pressure is being applied, but those sensors have become so sensitive that walking barefoot would hurt.


AM: So, there's the idea of re-examining a bit. Something like sandals provide some protection but also allow the feet to move freely and naturally.

AM: Styrofoam plastic was invented and started being used for take-out meal containers. Unlike paper, it retained heat, and sauce didn't spill onto your pants. People thought it was a magic material, amazing, and the "future". But then people started throwing it out of windows, turning it into plastic garbage. Now we're going back to using paper again. It's hard to judge if a new tool is really progress.


ON: I completely agree. Recently, I feel like things like the internet and social media have become burdens on society. We end up knowing things we didn't need to know, which can make people unhappy.

Also, the fact that everyone remembers everything, and records of it remain, can lead to unhappiness.


AM: Would it be better to re-look at things a bit?


ON: There are many things that make me wonder if they really align with human nature as biological beings.


AM: Since we don't fully understand the body's functions, it's hard to judge what's necessary for our bodies or what fits them best.


ON: That's why we study body movements. Of course, from my perspective, it's not necessarily about product design. But understanding human biological characteristics, especially those related to movement or the body, can help in designing products. That's the case with this research project as well.

I thought it was important to study how the skin stretches.

HJ: By learning more about the body, like how much skin can stretch, could it lead to something useful or interesting?


ON: I don't specifically think about it in terms of product design.

When your foot hits the ground, it changes shape slightly and that leads to a chain of movements that affect the bones above it. Variations in how this chain of movement unfolds can lead to knee issues. If knee problems prevent someone from going outside, their quality of life declines. For example, if movement happens in a certain way, it could make someone more prone to knee problems.

By carefully observing the body's movements and their variations, we can identify those at higher risk for developing conditions like osteoarthritis. With severe knee pain, people often undergo major surgery to replace the knee. If we understand the mechanics of body movements better, we can intervene earlier in those who are more susceptible.

HJ: By the way, are you fast at running?


ON: I'm slow.


HJ: Is there a way to run faster?


ON: A way to run faster?

I can't really answer that.

There isn't a lot of commonality among fast runners in the 100-meter dash. You can identify common traits in slower runners, but not so much with fast ones. For example, Usain Bolt's running form isn't particularly elegant.


AM: So, not everyone can run fast in the same way.


ON: Exactly. Each person's body is different, and people develop their own techniques for running well. It's hard to find commonalities among the top performers. It's the same with playing musical instruments.

A long time ago, there was a professor who studied the differences between skilled and unskilled musicians. We measured the movements of musicians, and while it's easy to spot what unskilled people are doing wrong, it's much harder to find common traits among skilled players. The more skilled they are, the less visible those commonalities become, as each person develops their own unique style.

That's why researching highly skilled individuals is difficult. For Olympic athletes, for instance, each one has a dedicated trainer who works with them individually. They receive training tailored to their specific needs. Science tries to find universal commonalities, so from a scientific perspective, highly skilled individuals are tricky subjects.

That's why I'm more interested in clinical cases or health issues where people are struggling. Maybe it's because I'm not particularly good at sports myself.


AM: The way our bodies move has changed over time. When I was a kid, I loved swimming, and I spent a lot of time playing in the ocean. I did swimming practice for years. At first I moved my arms in a wide crawl stroke, but my high school coach told us that keeping my arms closer to my body made us faster.

When I told my grandfather, he said, "We didn't swim like that in the past. So that's how people swim nowadays." Has swimming evolved?


ON: I think so.


AM: It seems like running has evolved too. People used to run one way, but now they run differently.


ON: I think coaching methods and teaching styles have changed. Olympic times keep improving. But part of that is also due to technology.

The materials in shoes have changed, improving their elasticity. In swimming, water resistance has decreased, which has definitely made a difference.

But we still don't fully understand what the ideal technique is.


AM: Even though our bodies are unchanged.