Endurance training is not about suffering. It’s about budgeting.

The currency is your energy, and the income tax department is your recovery.

When training to get stronger and fitter across the board, it helps to think of stress as different buckets. The trick is figuring out which ones to fill, which ones to keep half-empty, and which ones will tip over and drown your recovery if you’re not careful.

When it comes to endurance training, there are really only three inflection points worth remembering. Think of them as: easy, medium, and hard.

1. The first point is VT1, or the first ventilatory threshold. Training just under this lands you in Zone 2, the sweet spot for building a big aerobic engine. The best part? You can pile on volume here without wrecking tomorrow’s workout. A quick test: if you can rattle off a 15-word sentence without huffing and puffing, you’re in the right zone.

2. The second point is VT2, also known as lactate threshold. This sits at the top of Zone 3 and feels like that sustainable-but-gritty pace you can hold for 30–60 minutes before the wheels come off. For most people, this is the best return on investment. If you don’t have hours o spend on training, a couple of solid sessions here and you’ll notice the difference.

3. Finally, there’s VO₂ max or the maximum amount of oxygen your body can use. This is peak aerobic stress that corresponds roughly with your mile pace or an 8–10 minute all-out effort. Push much harder than this and you’re mostly just suffering for bragging rights.

Now, why bother slicing training this way? Because not all stress is created equal. Understanding the cost benefit ratio of training under each bucket helps apportion the limited training time we have to getting better. A marathoner clocking 12 hours a week has very different needs than someone with a couple of spare evenings. Chances are, you’re the latter.

So if you’ve only got two hours a week for endurance work, here’s a tidy little recipe:

1. 10 minutes near vVO₂ max

2. 50 minutes at VT2 (split into 2–3 smaller sessions)

3. 60 minutes at VT1 (again, in one go or broken up)

Note: endurance doesn’t have to mean running. Biking, rowing, ski-erging, or any other form of self-inflicted cardio will do, though your zones will shift depending on the toy.

At the end of the day it’s all about individual recovery. Ten minutes of high-intensity speed work might be gold for one person and a death sentence for another.  A good program factors for current ability and evolves slowly over time. Endurance training isn’t about proving how much misery you can endure; it’s about smartly rationing stress so you actually get fitter instead of just more tired.