What 99% of Runners Get Wrong About Zone 2 (And the Simple Shift That Actually Works)
Estimated read time: 3.42 minutes (about as long as it takes me to explain to my mom why I need seven different running watches) 🤑
Hey Performance Nerds! Jonah here. 🤓
You might be sabotaging your performance—by obsessing over Zone 2.
New research analyzing 5,973 athletes just flipped the script: higher-intensity training delivered the same or better mitochondrial gains as Zone 2.
And get this: sprint intervals were 3.9x more efficient than endurance work.
Today, we’re breaking down:
🎯 Why Zone 2 obsession misses the point — and what to do instead
💪 What actually drives performance adaptations (hint: it's not your heart rate zones)
📊 The massive study that changes everything about training intensity
⚡️ How to train smarter with less obsession (and more results)
💬 Your training success is my priority.
If you’re hitting a wall, feeling off-track, or just have a question (seriously—no question is too small!), hit reply. I read every message and I’m genuinely here to help you keep crushing it.
🧬 Performance Sponsor:
SiS is now the official sponsor of Marathon Science. Their performance products—like fueling bars, hydration mixes, and recovery supplements—are trusted by pros and grounded in real sport science.
🎯 Get 15% off any SiS product at the Feed with code JONAH15 at checkout
🗓️ Valid to June 15th | One use per customer
🚨 The Zone 2 Myth That's Hijacking Your Training
Most runners treat Zone 2 like a magic zone for fat-burning and mitochondrial gains. “Stay in Zone 2 or lose your gains,” right?
Here’s the truth:
Training above Zone 2 doesn’t hurt your mitochondria—it might grow them even faster.
💣 The Science Bomb: 5,973 Athletes Can’t Be Wrong
A massive meta-analysis—353 studies, 5,973 athletes—looked at how training intensity affects mitochondrial gains.
🔬 The finding?
Zone 2 didn’t come out on top.
Augie tried staying in Zone 2 once… got bored, chased a squirrel, and hit Zone 5. Still set a PR. 🐿️💨
High-intensity intervals (Zone 4 & 5) were just as effective—and sometimes even better—for building mitochondria.
So no, cranking it up doesn’t kill your gains. It might actually multiply them.
⚡️ The Training Load Truth That Changes Everything
Researchers didn’t just look at total training, they looked at adaptation per hour (aka training efficiency).
💥 Result: Higher-intensity or faster runs delivered more gains in less time.
Translation: 6 hours of sprint work = 24 hours of Zone 2.
But here’s the twist: Training intensity helped—but consistency predicted performance even better.
✅ More consistent sessions > Zone 2 perfection
TL;DR: Your legs don’t care if you stayed at 145 bpm. They care if you showed up 5 days this week.
🧠 Why Consistency Crushes Heart Rate Obsession
The real key to endurance gains? Consistency over time—not obsessing over a heart rate number.
📉 Zone 2 isn’t magic, but it is sustainable. And that’s the real win: it lets you train more often, and frequency beats perfection every time.
You can have the “perfect” plan, but if you're skipping workouts or running on fumes, it won’t matter.
And let’s be real, your watch doesn’t always know how you feel. But you do.
✅ Your Weekly Training Plan
✅ Run 4–6x per week
4–5 easy runs (conversational pace = recovery-friendly)
1–3 hard workouts only when recovered (tempo, intervals, long run)
✅ Listen to your body
Your heart rate monitor = a tool, not a tyrant
🎯 Practical Summary: What Actually Drives Progress
The real performance driver? Consistent training load—not obsessing over 145 bpm.
🔬 A study of 5,973 athletes showed:
Mitochondrial gains were similar across all intensities (23–27%).
Training volume + frequency = results.
✅ Focus on:
3–6 runs/week
Mostly easy, some hard
Build volume over time
Trust your body over your watch
🧠 Your body adapts to stress, not heart rate math.
So if you hit 152 bpm? Relax. That’s still progress.
While Zone 2 zealots check their watches every 30 seconds... You’ll be too busy crushing PRs to care. 🏁
🚨 Puma’s New AI Super Shoe Took 10 Minutes Off My Marathon
Did you miss my post about how Puma’s New AI Super Shoe Took 10 Minutes Off My Marathon? You can find it below!
I won’t lie. These videos take me a while to make. If you find it helpful, share it on your story or with a friend. It helps me a ton!
Are You a True Running Nerd? Prove it.. 🧐
Welcome to the prove you’re a nerd section. Each week, I ask a question about a common running science myth.
Answer correctly, and you’ll be entered into a weekly raffle to win a package of Jonah’s favorite supplements.
Which supplement has been shown to boost performance the most in high-intensity events like 5Ks or HYROX races, where you're working above your lactate threshold? 🔥🏃♀️
Last Week’s Results: Lactate Truth! ⚡️🦵🧂
Whoa, science squad! Most of you blew past the old-school lactate myths like a runner hammering the final 400m. 💨🔥
The right answer? Lactate builds up faster than your body can clear it—a sign that fatigue is incoming fast thanks to rising metabolic stress. 🧪✅
But here’s the truth bomb: Lactate isn’t the bad guy. It’s actually a backup fuel source! The real issue is the hydrogen ion buildup that turns your muscles into jelly and your stride into survival mode. 😵🧬
Here’s how the poll shook out:
⬜️ A. Your body switches to burning only fat for energy 🥑 – 4 votes
🟩 B. Lactate builds up faster than your body can clear it 🧪 – 246 votes ✅
⬜️ C. Oxygen uptake immediately drops 🫁 – 6 votes
⬜️ D. Your heart rate decreases ❤️ – 0 votes
Bottom line? Lactate isn’t your enemy—it’s your misunderstood ally. If you want to hold on longer when the pace gets brutal, train your body's buffering systems.💣
Nerdy Finds of the Week 📚🧑🔬
This section includes my favorite research, podcasts or books about running/lifting science.
Podcast: Dr. Alan McCubbin: Carbohydrate Loading: Diving Into The Research // Fuelin Sessions
🔬 Core Finding
One day of high-carb eating (10g/kg) is enough to fully load muscle glycogen—no need for a 3-day marathon.
📊 Key Research Points
Athletes hit 90% glycogen increase after just 24 hours of loading.
Eating high carbs for 3 days didn’t boost storage beyond day one.
All muscle fibers (fast + slow) filled equally—no delay.
No "depletion phase" needed beforehand.
Women get same results when dosing carbs per kg, not by % of calories.
🛠️ Practical Applications
🍽️ 10g/kg carbs in 1 day ➜ Fully loaded muscles for race day.
🚫 Skip low-carb depletion ➜ No added benefit, just extra fatigue.
⏱️ 6–6.5g/kg 2 days out + 8–12g/kg 1 day out ➜ Smart taper strategy.
🍽️ Use grams per kg ➜ Women load just as well as men.
🎯 Bottom Line
Don’t overthink your carb load. One big day of eating (and resting) works just as well—and feels way better.
Don’t forget: You + Science = AWESOMENESS 😎
Yours in science,
Jonah
P.S. - We have a crew of 15,870+ nerds here who are running FAST using science.
Did you need running science advice or tips? 🏃♀️💨🧪
Reply with your question, Augie and I (pictured below) will get back to you with science-backed tips!
Enjoy the newsletter? Please forward to a pal. It only takes 18 seconds. Making this one took 11.23 hours.
Please email me directly if you’re interested in references for this week!