Welcome to the positive corner of the internet. Every weekday, we help you make sense of the complex world of wellness by analyzing the headlines, simplifying the latest research, and providing quick tips designed to help you stay healthier in under 5 minutes. If you were forwarded this message, you can get the free daily email here.
Today’s Health Upgrade
Can your workouts pass down “fit” genes to your children?
Why your energy crashes (and how to fix it)
Maybe you should start sprinting
On Our Radar
Can Your Workouts Shape Your Future Children? Here's What New Science Found
What if your workout didn’t just benefit your health, but also influenced the potential of your future kids?
A new study found that exercise might send powerful signals through your sperm that could improve the metabolic health and endurance of your offspring.
Researchers put male mice through endurance training and then bred them. Their offspring, without doing a single workout, were born with better endurance capacity and healthier metabolic profiles than those fathered by sedentary males. Even wilder: when scientists injected embryos from sedentary fathers with just one microRNA elevated by exercise, the offspring showed the same endurance advantages.
The trained-dad offspring ran significantly farther and exhibited stronger metabolic responses. In contrast, none of these effects were observed in female offspring, and none carried over to the next generation of male grand-offspring.
But there’s one very big catch: the most impressive results were found in mice, not humans. We don’t focus on much animal research, but when there’s a finding like this and plans for human research, it’s worth exploring how exercise could shape future generations.
The researchers did take a peek at humans by examining sperm from 8 active men and 24 sedentary men, and a tiny sample showed correlations in microRNA levels, but zero evidence of inherited fitness.
The scientists think intense training may alter microRNAs in sperm that help “pre-program” energy systems in mouse embryos. But experts also flagged major hurdles: sperm RNAs are tiny compared to eggs (raising dilution problems), and we don’t yet understand how these molecules would cross the blood–testes barrier in humans. Translation: this is a breakthrough in mechanistic science, and very early.
This is science worth watching, but it reinforces something powerful: your workouts already reshape your biology in ways we understand, and maybe in ways we’re only beginning to uncover.
Together With Laird Superfoods
Why Your Energy Crashes (And The Simple Science-Based Solutions To Fix It)
If you've ever wondered why some days you feel energized after a meal and other days you feel sluggish, the answer might be hiding in one simple idea: how well your body switches between fuels. According to research, this ability to switch is one of the clearest signs of metabolic health.
Your metabolism works best when it can smoothly switch between fuel sources based on what you're eating and doing. And before you worry about needing a significant change, there are simple and surprising ways to boost your metabolic health.
A landmark review defined "metabolic flexibility" as your body's ability to toggle between burning carbs and burning fat depending on the situation. After you eat, a healthy metabolism ramps up carb burning; during fasting or exercise, it shifts toward fat. But in people with obesity or type 2 diabetes, this switch becomes sluggish — they burn a blend of fuels all the time, which is associated with more hunger, lower energy, and impaired glucose control.
So, how does the system actually work? You really have three fuel options: Glucose (your go-to after a meal), fatty acids (your primary fuel during exercise or fasting), and ketones (your backup fuel, produced when carbs are low).
If you want to improve your metabolic flexibility, here’s what works: move your body daily (even a walk counts), lift weights, get enough sleep, and avoid constant grazing. Or, you can sneak in foods that can help you switch fuel sources.
Your brain can run on ketones just fine, and your body naturally creates them during overnight fasting, exercise, or extended carb restriction. This is normal physiology; not a hack, just how the body is designed to adapt to changing conditions.
If you’ve ever gone too long between meals and felt your brain grinding to a halt, you’ve experienced what happens when your body struggles to switch fuels. That’s where one simple tool might help: MCTs.
Instead of needing a strict keto diet or long fasting window, MCTs give your body a small, gentle dose of ketones; the same “backup fuel” your brain uses when glucose starts to dip. In human studies, even a modest amount of MCTs raised ketone levels within an hour or two, providing a cleaner, steadier energy source.
The good news? You can get those MCTs by adding them to your morning coffee.
Laird Superfood Sweet & Creamy Creamer with Adaptogens delivers naturally occurring MCTs from coconut to give your brain that alternative fuel source when glucose isn’t cutting it, plus adaptogens like chaga and lion’s mane to support your stress response and focus. The product was founded by Laird Hamilton and Gabby Reece, who took their legendary passion towards health and poured it into simple solutions that aid wellness and longevity.
No dairy, no seed oils, no blood sugar rollercoaster. It’s just using nutrition science to offer clean, steady energy.
For the next 72 hours, Laird is offering Pump Club members an exclusive deal for new customers: Save 35% on your first order with code PUMPCLUB and get free shipping.
But this is limited to the first 500 new customers or 72 hours, whichever comes first.
And if you want it before Christmas, the last day to order is December 14th. Prefer long-term savings? You can also subscribe and save 20% forever.
Instant Health Boost
The Hidden Reason Sprints Make You Fitter (It's Not What You Think)
The real benefits of sprinting might not come from the burning in your legs. Instead, when you push the intensity threshold, it triggers a stress signal inside your cells that tells your body to rebuild stronger. And according to new research, that signal is entirely different from what you get with your usual cardio.
Sprint intervals spark a unique “clean-up and rebuild” response inside your cells that lower-intensity cardio can’t match.
Scientists compared four 30-second all-out sprints with a steady-state moderate cardio session. They didn’t just measure heart rate or calories. They took muscle biopsies, performed advanced imaging to assess mitochondrial shape, and analyzed thousands of cellular markers. That allowed them to watch in real time how each type of exercise reshaped the tiny energy factories inside your cells.
Sprint intervals give your cells a quick, intense challenge, the kind that forces your body to wake up and adapt. Because as effort shoots up, your energy systems work overtime, and your cells briefly shift into “upgrade mode.”
That’s not to say less intense cardio doesn’t have benefits. Moderate cardio builds more mitochondria and increases metabolic enzymes. Sprint training, on the other hand, made existing mitochondria more efficient by upgrading protein quality-control pathways and respiratory function.
To think of it differently, one builds the machinery, while the other upgrades the software.
You don’t need to choose between sprints and steady cardio: you benefit more by combining them. A weekly mix of one short sprint session (2-4 minutes of true hard work) and one or two moderate-intensity sessions supports both mitochondrial quantity and quality. If you’re going to sprint, don’t go from zero to 100. Warm up well, build gradually, and then push the intensity. From there, your cells will do the heavy lifting.
Better Today
Take any of these tips from today’s email and put them into action:
1. How Your Workouts Might Be Able To Shape Your Future Children's Fitness
A new study found that male mice that regularly performed endurance training fathered offspring with greater endurance capacity and healthier metabolic profiles, even though the offspring never exercised. Researchers even replicated the effect by injecting a single exercise-elevated microRNA into embryos, though the benefits appeared only in male offspring and didn't carry over to the next generation. It suggests incredible potential, but human evidence remains extremely limited.
2. Why Your Energy Crashes After Some Meals (And How MCTs Could Help Your Body Switch Faster)
"Metabolic flexibility" is your body's ability to toggle between burning carbs and fat, and it is one of the clearest markers of metabolic health. People with sluggish switching experience more hunger, lower energy, and impaired glucose control. MCTs can help raise ketone levels within 1-2 hours, providing your brain with an alternative fuel source when glucose levels dip without requiring a strict keto diet.
3. Sprints Upgrade Your Mitochondria Differently Than Slower Cardio
New research using muscle biopsies and advanced cellular imaging found that sprint intervals (four 30-second all-out efforts) trigger a unique "clean-up and rebuild" response that makes existing mitochondria more efficient, while moderate cardio builds more mitochondria and increases metabolic enzymes. The takeaway: combining one short sprint session (2-4 minutes of hard work) with one or two moderate sessions weekly supports both mitochondrial quantity and quality.
—
Publisher: Arnold Schwarzenegger
Editors-in-chief: Adam Bornstein and Daniel Ketchell
