Endurance 101 - Edition 13 - Building a Bigger Engine for Real Endurance
- Active Living Active Living
- 12 hours ago
- 7 min read
Welcome to another Endurance 101 Blog 🏃♂️🚴♀️🏊♂️
There are countless ways to train for speed and endurance in running, cycling, swimming, and just about any endurance sport where you’re spending 60+ minutes pushing into higher heart rate zones during an event. Intervals, tempo work, long slow distance, threshold sessions — the methods are endless.
But here’s the reality: in order to perform well in those higher zones on race day, you actually need to build the capacity to be there. And that’s where most athletes get it wrong.
We’ve all had that race. You start out feeling incredible. The legs feel light. The energy is high. The crowd is buzzing. Then suddenly — boom 💥 — your heart rate jumps into yellow… then red… and before you know it, the wheels come crashing down. What felt amazing in the first 10–15 minutes turns into survival mode far too early.
After many years of coaching and learning (sometimes the hard way), I’ve come to trust heart rate training because it doesn’t lie.
It translates across good days and bad days.
When you’re tired, stressed, under-recovered, or slightly off — your heart rate responds accordingly. It protects you from overloading the system based purely on ego or “feel.” Training by heart rate allows us to adjust intelligently instead of guessing.
If you pay attention to the prompts on your watch, you’ve probably noticed things like the adjusted heart rate max, or the trusted heart rate dial — little cues that guide your training and keep you in the right zone.
And that brings us to one of the most asked questions in endurance sport…
“Coach, why are we always running in blue and green?”
On your watch (whether it’s Garmin or Suunto) that means: ( if you are using another brand watch just translate the % on the table below into your 5 zones.)
🔵 Blue = Aerobic Base
🟢 Green = Controlled Endurance / Tempo
Here’s the truth:
Endurance is built here — in your 🔵 Blue and 🟢 Green zones.
Yes, it will probably feel slower than you expect… or slower than you want. You will probably walk more than you think needed That’s normal. And that’s the point. Building that part of your engine means you can actually run up that hill...not die half way and then having to pull yourself, your head and personality up the remainder of it. AND yes - some days you will feel like that dial is betraying you, by either going up or down too fast or slow. Reality is it takes practice to run like that and discipline. BUT applying this....you will see that
THEN over time, this steady, patient work turns into real speed.
Fast pace only matters if you can sustain it, and true sustainable pace is forged in the Blue zone, with plenty of Green zone miles. Run here consistently, and your engine grows—so when it’s time to push, you go faster without feeling like you’re dying. Also we do need sessions in that dreaded🔴Red and 🟠Yellow zones where it feels like our lungs might explode and our muscles might spontaneously combust. BUT Endurance Is Not Built in 🔴Red and 🟠Yellow.
ALTHOUGH.....
🔴 Red feels productive. 🔴 Red feels impressive.
🔴 Red makes good Strava captions.
But endurance?
That’s built in Blue and Green. Maybe you are new to this whole endurance thing and you don't totally understand why you need to do this. Because when you go out - you chase that endorphins but then tomorrow you cannot get to that heart rate target point or you are just too tired..... Understand that this is why.....
When I ask you to stay in 🔵 Blue and 🟢 Green, we are:
Strengthening your heart muscle and your arterial walls
Increasing stroke volume
Improving oxygen delivery
Expanding capillary networks
Increasing mitochondrial density
Improving fat utilisation - very important LOL
Raising your lactate threshold gradually - aka....it takes you longer to get into that " muscle BURN" zone
In simple terms?
We’re building a bigger engine.
What Happens When Blue & Green Expand?
Here’s the magic.
The wider your 🔵 Blue and 🟢 Green zones become:
The longer it takes for your heart rate to drift into 🟠 Yellow (Threshold)
The even longer it takes to spike into 🔴 Red (VO₂ Max)
That means:
The pace that used to push you into Yellow…Now sits comfortably in Green.
The pace that used to send you gasping into Red…Now only nudges Yellow.
And what happens?
👉 You run faster.
👉 It feels controlled.
👉 You don’t feel like you’re dying.
That’s aerobic development at work.
The Real Win
When Blue and Green are strong:
Your long runs feel smoother.
Your recovery improves.
Your intervals hit harder.
Your race pace feels sustainable.
You don’t panic at 8km.
You don’t fall apart at 15km.
You don’t explode when the pace lifts.
Because it takes longer for you to reach the danger zones.
The Coach Truth
Everyone wants speed.
Very few people want to build the base that allows speed to last.
Blue and Green are not “easy.”
They are strategic.
They are disciplined.
They are patient.
And they are the reason you eventually run fast without it feeling like you’re dying.
And when you do hit Yellow or Red in a race?
You’ll have the engine to handle it.
That’s why we train there.
Not because it’s comfortable.
But because it works. 💙💚
The Nerd Side of Heart Rate Zones (Yes, We’re Going There)
Alright runners, it’s time to put on your lab coats… or at least pretend like you’re in one while sweating through your run.
Let’s dive into the science behind the colours you see on your watch — and why your body actually thanks you for respecting them.
Because somewhere between “just go run” and “why am I dying at 4km?” is the science that actually makes you better.
As a coach, I’ve heard it all:
“Coach, I ran hard the whole time.”
“I don’t believe in slow running.”
“Intervals are the only thing that makes me feel fit.”
And my personal favourite after a tough session:
👉 “But did you die?”
Exactly.
Hard work always pays off… even if your personality doesn’t always feel like cooperating.
But smart work? That pays off faster.
The 5 Heart Rate Zones (With Colours You’ll Actually See on Your Watch)
Most watches — use a 5-zone system that aligns very closely with this structure:
Zone | Colour | % Max HR | What It’s For |
Zone 1 | ⚪ Grey | 50–60% | Recovery |
Zone 2 | 🔵 Blue | 60–70% | Aerobic base |
Zone 3 | 🟢 Green | 70–80% | Tempo |
Zone 4 | 🟠 Orange | 80–90% | Threshold |
Zone 5 | 🔴 Red | 90–100% | VO₂ Max |
Now let’s unpack what that actually means — and why most runners are training wrong.
⚪ Zone 1 – Grey (Recovery)
This is the “I could do this all day” pace.
You can chat. You can breathe. You can question your life choices calmly.
Purpose:
Flush out fatigue
Increase circulation
Help your body absorb hard training
This is what normally gets prescribe the day after intervals when everyone thinks they need to “prove” something or when we say...go for a walk!
You don’t get fitter by smashing every run. You get fitter by recovering from the smash.
🔵 Zone 2 – Blue (Aerobic Base)
Ah. The magical, misunderstood zone.
This is where real endurance is built.
Comfortable. Conversational. Sustainable.
And yes — it often feels “too easy.”
Which is exactly why people avoid it.
What Zone 2 does:
Strengthens your heart (bigger stroke volume)
Improves oxygen delivery
Builds mitochondria (your energy factories)
Increases fat-burning efficiency
Raises your lactate threshold over time
Here’s the powerful part:
When you consistently train in Zone 2, the pace that used to put you in Zone 3 starts sitting comfortably in Zone 2, and in works down to every zone.
That’s what we mean when we say it “widens the zone.”
You run faster… at the same heart rate.
No drama. No redlining. Just progression.
Speed built without an aerobic base is temporary.
Speed built on a strong aerobic base? That sticks.
🟢 Zone 3 – Green (Tempo)
This is comfortably uncomfortable.
Talking becomes broken sentences.
This is also what I call “the grey zone trap.”
Because many runners accidentally live here.
Zone 3 is:
Too hard to recover properly
Too easy to create serious adaptation
It has its place — structured tempo work, steady state efforts — but it should be intentional.
If every “easy run” drifts into green, we need to talk.
🟠 Zone 4 – Orange (Threshold)
This is where things get spicy.
Breathing is heavy. Conversation is limited. You’re working.
This zone improves:
Lactate tolerance
Speed endurance
Race pace control
This is where 10km to half marathon pace work usually lives.
You don’t stay here long — but you visit regularly.
Hard? Yes.
Necessary? Also yes.
And if you finish a threshold set gasping and questioning your existence, I’ll probably say:
“But did you die?”
Exactly. Moving on.
🔴 Zone 5 – Red (VO₂ Max)
Short. Sharp. Brutal.
This is interval territory:
400m repeats
Hill sprints
2–3 minute max efforts
This zone:
Improves maximal oxygen uptake
Builds top-end speed
Recruits fast-twitch fibres
Strengthens mental grit
You cannot live here.
You visit. You work. You recover.
Then you go back to Blue.
Why Most Runners Plateau
Because they train like this:
Too much 🟢 Green
Not enough 🔵 Blue
Random 🔴 Red
But it’s not structured.
Elite endurance athletes spend roughly 70–80% of their training in low-intensity zones (Grey + Blue).
Not because they’re lazy.
Because it works.
Intervals – Where They Fit
Intervals are controlled stress.
Work + recovery.
They:
Raise VO₂ max
Improve running economy
Increase lactate clearance
Build mental resilience
But intervals without aerobic base are like putting a turbo on a lawnmower engine.
It makes noise. It doesn’t last.
Build the engine first.
How It All Fits Together
Think of it like building a house:
⚪ Grey = Maintenance 🔵 Blue = Foundation 🟢 Green = Structure 🟠 Orange = Performance layer 🔴 Red = Finishing power Sometimes we use RPE...and here is what it translates to.
Zone | Colour | % HRR | Typical Feeling / RPE (1–10) | Notes |
Zone 1 | ⚪ Grey | 50–60% | 1–2 | Very easy, recovery pace, you could chat all day. “Netflix pace.” |
Zone 2 | 🔵 Blue | 61–70% | 3–4 | Comfortable, conversational, building aerobic endurance. Bottom Sweet spot for long runs. |
Zone 3 | 🟢 Green | 71–80% | 5–6 | Moderate effort, talking is possible but not easy. Upper Effort for long runs, Tempo feel, threshold prep. |
Zone 4 | 🟠 Orange | 81–90% | 7–8 | Hard effort, talking in short sentences. Lactate threshold work. Legs start to feel it. |
Zone 5 | 🔴 Red | 91–100% | 9–10 | Max effort, can barely speak. Intervals / VO₂ max. Short, sharp, brutal. |
If the foundation is weak, everything cracks.
And no, motivation is not the secret ingredient.
Consistency is...
Hard work always pays off — even if your personality complains the entire way. Final Coach Truth
You don’t need every run to feel epic.
You need:
Discipline over dopamine
Patience over ego
Structure over chaos
🏃♂️ Run slow enough to run fast later.
💪 Build the base.
🛠️ Do the work.
And next time a session feels tough…?
You know what I’m going to say:
❗ “But did you die?”
Exactly. ✅
Now… lace up! 👟🔥
Comments