Why exercise drains some people and energizes others

HostWe have all seen that person who finishes a long run and looks like they just had a big cup of coffee, while the rest of us feel like we need a three-hour nap just to recover. It feels like a bit of a trick, as if some people have a secret battery that the rest of us didn't get. Why is it that the same walk or the same gym session can leave one person ready to go and leave another person totally wiped out?

GuestIt really comes down to how your body handles a crisis. We usually think of a workout as a good thing, but to your cells, a hard push is just a lot of stress. Your heart is racing, your muscles are tearing, and your body has to decide how to pay for all that work. For some, the body clears the bill and has plenty of energy left over. For others, the workout puts them into a kind of debt that takes hours or even days to pay back.

HostBut if I'm in debt, shouldn't I just get richer the more I work out? I mean, shouldn't it get easier every single time I do it?

GuestYou would think so, but it's not a straight line. There's this idea of a stress bucket. Think of everything in your life—your job, not sleeping well, even a small cold—as water filling up a bucket. A workout is just more water. If your bucket is already nearly full, even a short jog makes it overflow. When that happens, your body doesn't feel energized. It feels attacked. People who get that big boost of energy often have more room in their bucket, so the extra work doesn't tip them over the edge.

HostSo it's less about the workout itself and more about what I did the rest of the day?

GuestThat's a huge part of it, but we also have to look at your tiny internal power plants. Every cell in your body has these little parts that turn food and air into fuel. Scientists call them mitochondria. When some people start a new habit, their bodies are very fast at building more of these power plants. They see the hard work and get to building right away. After a few weeks, they have way more fuel ready to go. But some of us are what you might call low responders. Our bodies are just a bit slower to build those new plants. We feel all the strain of the work, but we don't get the new fuel as quickly. It makes the whole thing feel like a slog because the payoff is lagging behind the effort.

HostThat sounds like I'm just born with a bad engine. Is it all just down to the luck of the draw with my genes?

GuestIt's not a life sentence, but it does mean you can't just copy what someone else is doing. If you have the type of body that takes longer to build those power plants, you have to be much more careful with the dose. Think of it like a suntan. Some people can sit out all day and look great. If I do that, I just get a burn. It doesn't mean I can't go outside; it just means I need a different amount of sun. People who feel drained often are just taking too big a dose of exercise for what their body can handle right now.

HostHmm, that makes sense. But what about that mental buzz? Some people seem to get a high from it that I just never feel.

GuestWell, that's the brain stuff. When you move, your brain is supposed to let out these feel-good chemicals. They're like your own built-in drug store. They help dull the pain and make you feel a bit of a glow. But if your body is already feeling a bit of low-level heat or swelling—maybe from a bad diet or just a lot of stress—those happy chemicals get drowned out. Instead of a glow, all your brain hears are the alarm bells from your muscles saying they're tired and sore.

HostI always thought that runner's high was something only marathon runners got. You're saying even a regular person should be feeling that?

GuestYou don't need to run twenty miles to get it, but you do need to hit a certain sweet spot. If you go too hard, the stress of the workout is so high that it kills the mood. But if you find that middle ground, your body releases things that are actually a lot like the chemicals that make people feel relaxed and happy. Some people get a huge hit of that, and for them, exercise is a mood-booster. For others, the brain is just more sensitive to the pain than the reward.

HostIs there any way to flip that switch, or are we just stuck with how our brains are wired?

GuestYou can actually train it. There's even new stuff coming out about the tiny bugs living in our gut. It sounds weird, but those bugs send signals to the brain through a long nerve. Some of those bugs love it when we move, and they send happy signals. If your gut is out of balance, you might not be getting those signals. So even your lunch from yesterday could be changing how you feel about your morning run. Scientists are even finding that the way we think about the movement matters, as just expecting to feel tired can make the body produce more of the chemicals that cause that heavy, drained feeling.

HostThat stress bucket is usually fuller than we think, but it helps to know that an afternoon slump is often just the body trying to balance the books.