How carbon-plated super shoes broke marathon records

HostIf you look at the times for the marathon lately, it feels like something broke. People are running faster than we ever thought they could. It used to be that shaving a few seconds off a record took years of hard work. Now, records are falling by minutes at a time. And it all seems to point back to what they have on their feet. What's actually going on inside those thick, chunky shoes?

GuestIt really comes down to how much energy we waste with every step. For a long time, the best racing shoes were basically thin strips of rubber. They were light, which is good, but they didn't do much else to help you move. These new super shoes are the opposite. They look like big moon boots. The secret is a mix of a very special foam and a stiff plate made of carbon. The foam is the real star here. It's a type of plastic that's incredibly light but also very squishy and bouncy. When your foot hits the ground in a normal shoe, most of that force just turns into heat and disappears. But this foam acts like a spring. It squishes down and then pops back up, giving a lot of that energy right back to the runner’s leg so they don't have to work as hard to keep moving.

HostSo it's basically like running on a trampoline? But if the shoe is that soft, wouldn't you just wobble all over the place?

GuestYeah, and that's why the carbon plate is in there. If you just had a big block of that bouncy foam, it would be like trying to run on a pile of marshmallows. You would lose your balance and your foot would twist. The carbon plate runs through the middle of the foam like a spine. It's very stiff, so it gives the shoe its shape and keeps it steady. But it does something else, too. It's curved, sort of like a spoon. When you roll onto your toes to push off, the plate helps the shoe keep its form. It stops your big toe from bending as much as it usually would while you run.

HostWait, why would we want to stop the toe from bending? Is that not how we're built to move?

GuestWell, it's natural, but it's actually a huge waste of fuel. Every time your toe bends, the muscles in your foot and calf have to work to keep you stable. That burns energy that could be used to push you forward instead. By keeping the foot flatter and more stiff, the plate lets the shoe do the work instead of your muscles. It acts like a little lever. So you're getting a boost from the bouncy foam and you're also saving energy because your muscles don't have to work as hard to hold your foot in place. When you add those two things together, runners can go at a faster pace for a lot longer before they get tired.

HostSome people call this cheating, though. It almost sounds like putting a motor in a shoe. Are these records even real anymore?

GuestIt's definitely the biggest jump in gear we have ever seen in the sport. Some people hate it because they feel like it's cheating the history of the marathon. But the shoes don't run for you. You still have to have an incredible heart and lungs to finish that race. What the shoes do is change the math of how tired your body gets. And here is the really interesting part: they help your legs stay fresh. In the old, thin shoes, the pounding of the road would just shred your muscles. By the end of a race, your legs felt like lead. With these shoes, the foam soaks up so much of that shock that runners aren't nearly as beat up. They can train harder, more often, because they get back on their feet much faster than they used to.

HostSo you're saying they can run fifty miles a week instead of forty because they're not as sore.

GuestThe foam in these shoes keeps getting lighter and more snappy every single year, so we probably haven't even seen the fastest times humans can reach yet.

HostThose chunky moon boots turned the road from something that breaks us down into a surface that actually pushes us back up.