I'm training for the San Francisco half marathon at the end of July, with only 4 weeks to prepare, and no running experience
For someone who has spent the past 15 years living in the world of basketball, force plates, and strength and power training, that's meant dusting off a side of exercise science I haven't spent nearly as much time applying recently.
In other words, I am putting the "C" back in strength and conditioning.
Over the next month, I'll be sharing some of the research that's shaping my own training.
We'll dive into endurance physiology, conditioning, recovery, running economy, and practical programming ideas that coaches can immediately apply, even if you never plan on running 13.1 (or dare I say more).
It only felt right to start with the topic that has completely taken over the endurance world, Zone 2.
What Is Zone 2?
Few training concepts have exploded in popularity quite like Zone 2.
Scroll through YouTube, listen to a longevity podcast, or follow endurance coaches on social media and you'll hear the same message over and over:
"Spend more time in Zone 2."
The claimed benefits are impressive.
- Better mitochondria.
- Better fat burning.
- Better endurance.
- Better metabolic health.
- Even a longer lifespan.
The problem is that many people don't actually know what Zone 2 is.
Why Is Zone 2 Popular?
The popularity of Zone 2 isn't just marketing. There are legitimate reasons why endurance coaches and physiologists value it.
Training in Zone 2 develops the aerobic engine that supports endurance performance.
Some of the biggest benefits include:
- Improved aerobic fitness ⮕ Sustain exercise for longer.
- Greater mitochondrial capacity ⮕ Build a stronger aerobic engine.
- Better fat oxidation ⮕ Spare glycogen during longer efforts.
- Lower training stress ⮕ Accumulate more volume with less fatigue.
- Improved recovery ⮕ Recover faster between sessions.
- Stronger endurance foundation ⮕ Support performance across sports.
Zone 2 is clearly beneficial for endurance training. However, whether it deserves the title of "best" is a much different question.
Zone 2 Isn't a Heart Rate
Many people think Zone 2 means staying between a certain heart rate.
Others think it's a running pace.
Others rely on whatever their watch tells them.
Physiologically, none of those define Zone 2.
Zone 2 is defined as exercising just below the first lactate threshold (LT1).
LT1 represents the highest exercise intensity where your body can still produce and clear lactate at approximately the same rate. Beyond this point, lactate begins to gradually accumulate because production starts to outpace clearance.
Importantly, lactate isn't the enemy.
Your muscles produce lactate all the time, even at rest. Lactate is actually a valuable fuel source and plays an important role in energy metabolism. The threshold simply marks the point where production begins to exceed clearance.
From a practical standpoint, Zone 2 is the highest sustainable aerobic intensity.
You're working hard enough to create a meaningful aerobic stimulus while keeping metabolic stress relatively low.
Its the right balance between aerobic work that is easily recoverable from.
Here's Where It Gets Complicated
This all sounds straightforward. Until you try prescribing it.
One of the biggest takeaways from a recent review in Sports Medicine is that Zone 2 is actually difficult to define precisely.
Why? Because LT1 is highly individual.
The authors presented three examples where LT1 occurred at just 23%, 45%, and 57% of peak power output.
In the examples presented, LT1 occurred at just 23% of peak power in one participant, 45% in another, and 57% in a well-trained individual. That's more than a twofold difference in external workload between individuals.
This highlights an important principle: as aerobic fitness improves, LT1 occurs at a higher exercise intensity, and vice versa.
In other words, two athletes could both be perfectly in Zone 2 while running at completely different paces, heart rates, and power outputs.
This is why blanket prescriptions like stay between 130 and 140 bpm, run a 12-minute mile, stay in Garmin Zone 2, etc. can be misleading.
They might work for one person. They might completely miss the mark for another.
So How Should You Program It?
The good news is that you don't need a lactate analyzer to benefit from Zone 2.
For most athletes, a practical definition works remarkably well.
Train at the highest sustainable aerobic intensity where you can still comfortably hold a conversation without progressive fatigue building over one hour or more.
Will that land everyone exactly at 1.8 mmol/L of blood lactate?
Probably not.
Does it need to? Probably not.
The goal isn't to chase a specific lactate number, but to accumulate high-quality aerobic work that is challenging enough to drive adaptation while remaining sustainable.
Coaches Takeaway
Aerobic fitness underpins almost every sport, improves recovery, supports work capacity, and benefits long-term health.
So from that perspective, I think Zone 2 deserves the attention it's receiving.
At the same time, I think we've become a little too obsessed with finding the perfect heart rate or the perfect training zone.
Physiology isn't that neat.
As coaches, we should understand the science, appreciate the limitations, and remember that our job isn't to perfectly measure every physiological variable. It's to consistently prescribe training that helps athletes improve.
That's exactly what I'll be exploring over the next month as I prepare for my half marathon.
If you've ever wanted to better understand conditioning beyond simply "go run," you're in the right place.
By the way, I am having fun with the process and sharing a ton of content on instagram, so make sure to follow along.
I hope this helps,
Ramsey
Reference: Storoschuk KL, Moran-MacDonald A, Gibala MJ, Gurd BJ. (2025). Much Ado About Zone 2: A Narrative Review Assessing the Efficacy of Zone 2 Training for Improving Mitochondrial Capacity and Cardiorespiratory Fitness in the General Population. Sports Medicine, 55, 1611-1624.
