Go Slow to Go Fast? Why Zone 2 Training Works

If your easy winter rides feel like a waste of time and you’re tempted to make every session a sufferfest, this one’s for you. Zone 2 training — long, steady efforts at an easy-to-moderate intensity — is everywhere in endurance coaching conversation right now. The “off-season” or base training phase is when you will see large amounts of Z2, and for good reason.   

The pitch is simple: ride easier, more often, and for longer — you’ll build more efficient mitochondria, learn to use fat, and get “fitter”. The reality is a little more nuanced, but the bottom line remains: slowing down, done intentionally, is a powerful way to get faster.

What Is “Zone 2”?
Zone 2 in layman's terms is defined as a “conversational pace," meaning you can talk comfortably but are not breathing hard. It’s roughly 60–70% of max heart rate or a sustained pace around the upper end of “easy” on the RPE scale (like 4/10). In power terms for cyclists, it often maps to ~55–75% of FTP (functional threshold power), depending on how your zones are set and your level of training/fitness.

Erring on the lower end of Zone 2 would be wise for athletes newer to training or coming off a break, but you will see many elite riders spending more time at the upper end… where terms like “Endurance Plus” or “FatMax” can be found.

The Short-n-Sweet Physiology Lesson
Endurance adaptations from steady aerobic work are vital to the overall capacity of an endurance athlete. To revisit my trusty “pyramid analogy”, endurance training builds the width and depth of the lowest levels, allowing you to build a stronger, higher pyramid on top. The adaptations take time though, it’s easier (or quicker) to build power and speed but the deep adaptations from endurance can take months…and years. 

Okay, so a brief on the adaptions, which include but are not limited to: increases in mitochondrial content and function, mitochondria size and density, improved capillary density, a shift toward better fat oxidation, etc. — all of which let you produce work more efficiently for longer. (2)

Fat oxidation (the body’s ability to use fatty acids as fuel) tends to be higher at low-to-moderate intensities — that’s the classic physiology: low-moderate intensity → greater fatty acid availability and usage versus high intensity. (1)

How To Do Zone 2 (And How Not To)

1. Use Zone 2 to build an aerobic base. 
   Prolonged low-intensity training supports greater gains and increases in the intensity later. Endurance adaptations take time, so be patient and increase over time.
   
   
2. It should be easy, but not too easy.
   ​ Zone 2 is not necessarily a “dog walk”, it’s intentionally keeping your pace up. Think of it as “keeping the chain tight” (for my cyclists). You want to keep things moving but comfortable. 
   
   
3. Harder is not better.
   Just as I said not to keep it too easy, it is a bigger pitfall to make it too hard. Many athletes think they’re in Zone 2 but are actually drifting higher, as they press the pedals just a bit more so they can feel like they’re working hard — compromising the training stimulus, goals, and impacting recovery.
   
   
4. Fuel it like you mean it.
   A big mistake is to neglect your fueling needs during this time. Many athletes think that because the work is easier, it doesn’t require the same attention to fueling. Even at 60-70%, you are still using a large amount of carbohydrates, with most athletes probably burning through 600-800 calories an hour. Even if only ½ of that is carbs, that’s 75-100g of carbs an hour being used for energy. This is how to do it.
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5. Implementing it. 
   Structure: 2–4 days per week during base season, depending on # of days training and volume goal.
   Tools: heart rate (60-75% Max HR), Power (55–75% FTP), or RPE (4-5/10). 

Bottom line
Zone 2 training builds the aerobic engine, improves mitochondrial function, and teaches the body to use fuel more effectively — it’s not a magic bullet, but it’s a key tool for the long haul. The best athletes use it to accumulate volume and complement their training. The smartest endurance athletes? They’re not just training hard, they’re training smart.

References

1. Achten, J., & Jeukendrup, A. E. (2004). Optimizing fat oxidation through exercise and diet. Nutrition, 20(7–8), 716–727. https://doi.org/10.1016/j.nut.2004.04.005
2. 2. Granata, C., Jamnick, N. A., & Bishop, D. J. (2018). Training-induced changes in mitochondrial content and respiratory function in human skeletal muscle. Sports Medicine, 48(8), 1809–1828. https://doi.org/10.1007/s40279-018-0893-y