The 80/20 Method is one of the best ways to boost your cardio fitness (VO₂ max).
Spend 80% of your running time at low intensity. 2nd heart rate zone. You should be able to talk.
20% at high intensity. 5th heart rate zone. Close to your peak capacity.
This approach gives you the right balance. The easy runs build your base and let you recover, while the hard runs push your limits and raise your VO₂ max quickly.
How to Set Accurate Heart Rate Zones
Download EverMax.
Run a 30-minute all-out trial using Apple Watch (after warm-up).
Run solo — this ensures you're running at your own pace, not matching someone else's.
Maintain a steady effort throughout all 30 minutes. Don't exhaust yourself in the first 10 minutes. Your pace should be relatively consistent from start to finish.
Open your trial run in the EverMax app — it will automatically appear in your workout history.
Tap
under the Heart Rate chart.
The app will automatically calculate your heart rate zones.
Take new measurements every few months to properly reflect changes in performance.
Why a 30-Minute Trial Beats Standard Estimation for Heart-Rate Zones
Age formulas are too generic to be personal
Most apps like Strava, Garmin, Apple Fitness and Woop calculate zones using an age-based max-HR estimate (220−age, 208−(0.7×age)). That’s convenient, but research shows big person-to-person error and poor agreement across these formulas. In short: your birth year isn’t your physiology.
A 30-minute trial measures you, not your age
EverMax sets zones from lactate-threshold heart rate (LTHR), found via a solo 30-minute time trial. Because it’s anchored to your current threshold effort, zones better match how you actually perform — no guessing from a population formula.
Labs are the gold standard, but the field test is close
Direct lactate testing in a lab is great, just not accessible for everyone. The 30-minute field method has been shown to estimate HR at lactate threshold with no significant difference from lab criteria. That’s accurate enough for training decisions, without the appointment or cost.
How to Train in Zone 5
Zone 5 is high-intensity training where you're breathing very hard and can't speak. Your heart pumps near its maximum capacity, forcing your body to adapt.
High-Intensity Interval Training (HIIT), like the "Norwegian 4x4", is the best for Zone 5 training.
The Protocol
~10 minutes of easy jogging to warm up to prevent injury.
4 intervals of 4 minutes in Zone 5 (very hard effort - you're gasping for air).
3 minutes of easy jogging between intervals.
~10 minutes of easy jogging to cool down and facilitate recovery.
Total time: 28 minutes plus warm-up and cool-down.
Why This Protocol Dominates
The Norwegian 4x4 is the most extensively studied VO₂ max protocol. Research shows meaningful improvements in both men and women, and in both untrained individuals and well-trained athletes. It consistently outperforms moderate continuous training and other interval formats.