Blog

Evidence-based guides to VO2 max training, testing, and the interval protocols, tools, and apps that raise your number.

Whoop vs Garmin: Which Is Better for VO2 Max and Training?

Whoop vs Garmin for VO2 max accuracy, recovery, GPS, screen, and price. Which one fits your training.
What Is Interval Training? Benefits, Types, and How to Start

What interval training is, the main types, the science-backed benefits, and a simple way to start at any fitness level.
Cardiovascular Endurance: What It Is and How to Build It

What cardiovascular endurance is, how it is measured by VO2 max, why it predicts longevity, and a proven weekly plan to build it.
Samsung Galaxy Watch VO2 Max: How It Works and How Accurate It Is

How the Samsung Galaxy Watch estimates VO2 max via Samsung Health and the BioActive sensor, the outdoor run it needs, its accuracy, and how it compares to Garmin, Apple Watch, and Coros.
Fitbit Cardio Fitness Score by Age: Chart and What's Good

Your Fitbit Cardio Fitness Score is a VO2 max estimate. By-age charts for men and women, what is good at each decade, and how Fitbit's levels map to the numbers.
Fitbit Air VO2 Max: Does It Track It, and How to See Your Score

Does the Fitbit Air track VO2 max? Yes, as your Cardio Fitness Score. How it estimates it without GPS, why yours might not show, and how it compares to the Charge 6.
Amazfit VO2 Max: How Zepp Estimates It and How Accurate It Is

How Amazfit watches estimate VO2 max via the Zepp app from outdoor GPS runs and wrist heart rate, how accurate it is, and how it compares to Garmin, Apple Watch, and Coros.
Polar VO2 Max: The Fitness Test, OwnIndex, and How Accurate It Is

How Polar estimates VO2 max via the at-rest Fitness Test (OwnIndex) and Running Index, how accurate each is, and how it compares to Garmin, Apple Watch, and Coros.
Coros VO2 Max: How EvoLab Estimates It and How Accurate It Is

How Coros watches estimate VO2 max via EvoLab from outdoor runs, the 25-minute run it needs, its accuracy, and how it compares to Garmin, Apple Watch, and Whoop.
Oura VO2 Max: How Cardio Capacity Works and How Accurate It Is

How the Oura Ring estimates VO2 max via Cardio Capacity, the walking test it uses, its accuracy, and how it compares to Apple Watch, Garmin, and Whoop.
VO2 Max Training Plan: The Science of an 8-Week Program That Works

The science behind an 8-week VO2 max plan, why weeks should undulate with a deload and taper, and the research-built plan inside PEAKVO2 you can start free.
VO2 Max App: What to Look For and the Best One for iPhone

What a good VO2 max app should do, training versus tracking apps, and the best pick for iPhone and Apple Watch.
Norwegian 4x4 for Beginners: How to Start Safely

How hard intervals should feel, how often to train, how to scale it down, and a 4-week on-ramp to the full Norwegian 4x4.
30/30 Interval Training: The 30-Second Workout for VO2 Max

Alternate 30 seconds hard with 30 seconds easy to keep near VO2 max. How to do it, how many rounds, and the interval timer you need.
PEAKVO2 vs VO2Max Training: The Closest Comparison

The two most similar VO2 max apps, compared line by line: field tests and pricing versus Zone 2 and training-load analytics.
PEAKVO2 vs VO2Max Hiit Workout: Wrist Training or a Free Phone App?

A free, customizable protocol app for iPhone and iPad versus a wrist-native VO2 max app with heart rate zones and tracking. What each does and who each fits.
PEAKVO2 vs VO2boost: Which VO2 Max App Fits Your Training?

A running-focused VO2 max app with HR-triggered voice coaching versus an Apple Watch VO2 max app across any activity. What each does and who each fits.
PEAKVO2 vs VO2 Max Pro: Track It or Train It?

A VO2 max tracker with fitness age and percentile benchmarks versus the training app that raises the number. What each does and who each fits.
PEAKVO2 vs True VO2 Max: Measure It or Train It?

A lab-like VO2 measurement app with indoor and weather-corrected estimates versus guided VO2 max interval protocols on your wrist. What each does and who each fits.
PEAKVO2 vs Seconds Interval Timer: Timer or Training App?

The classic build-your-own interval timer versus a purpose-built VO2 max training app. What each does, the price, and who each fits.
PEAKVO2 vs Peak Interval: Ready-Made Protocols or a Custom Builder?

A customizable interval timer with an AI Coach and 5-zone heart rate versus a ready-made VO2 max protocol app. What each does and who each fits.
PEAKVO2 vs a Free Online Interval Timer: App or Browser?

A free browser interval timer versus a native VO2 max app for iPhone and Apple Watch. What each does and when each fits.
PEAKVO2 vs Nike Training Club: Which One Fits Your Goal?

A free library of trainer-led video workouts versus a purpose-built VO2 max interval app. What each does and who it fits.
PEAKVO2 vs N4x4: One Protocol or a Full Library?

A focused free Norwegian 4x4 app versus a full VO2 max protocol library with field tests. What each does and who each fits.
PEAKVO2 vs Intervals Pro: Which Interval App Should You Get?

A purpose-built VO2 max training app versus a customizable build-your-own interval timer. Features, price, and who each fits.
PEAKVO2 vs IntervalCoach: Plan the Training or Run It?

An AI coach that plans and adapts your training versus the app that runs VO2 max sessions on your wrist. What each does and who each fits.
The Benefits of HIIT: What High-Intensity Interval Training Actually Does

The evidence-backed benefits of HIIT: faster VO2 max gains, better metabolic health, time-efficient fat loss, and the honest limits.
PEAKVO2 vs SmartWOD: Which App Fits Your Training?

A VO2 max interval training app versus a CrossFit WOD timer and generator. What each does and who it fits.
PEAKVO2 Features: What the Interval Training App Does

Eight guided protocols, color-coded phases with live heart rate, Apple Watch, Live Activities, Apple Health sync, an activity heatmap, and built-in calculators.
The Norwegian 4x4 App: Run the Protocol Without Watching a Clock

The app that runs the Norwegian 4x4 for you: automatic intervals and recoveries, heart rate zones, and a haptic tap at every switch.
HIIT Workout Plan: A 6-Week Plan You Can Actually Follow

A structured 6-week HIIT plan, three sessions a week, from a gentle on-ramp to the Norwegian 4x4. Exact sessions and heart rate targets.
Why Does My Heart Rate Stay Elevated After Intervals?

Why heart rate stays high after hard intervals, how long is normal, how fast recovery should be, and when to worry.
Best VO2 Max Training Apps: Compared by What You Need

A criteria-based comparison of guided-protocol apps, interval timers, coached plans, and VO2 max trackers, and the use case each fits.
The Apple Watch Interval Training App Built Around VO2 Max

Wrist-based timing, haptic cues, automatic phase changes, and eight ready-to-run VO2 max protocols. Runs on Apple Watch, no phone needed.
Hyrox vs CrossFit: The Real Differences and Which Suits You

Standardized endurance race versus constantly varied high-intensity training. What each rewards, which is harder, and how to train for either.
HIIT vs Steady-State Cardio: Which Is Better for Your Goal?

Which raises VO2 max faster, which burns more fat, which is more sustainable, and why the best cardio uses both.
Beep Test Score by Age: Average and Good Levels (Chart)

Average and good beep test levels for men and women by decade, youth PACER standards, and the VO2 max each level represents.
How to Increase VO2 Max Without Running

The best non-running methods to raise VO2 max, the interval protocols that work on any of them, and which carry a higher ceiling than running.
How Long Does It Take to Improve VO2 Max? A Week-by-Week Timeline

The first changes in 2 to 3 weeks, meaningful gains at 6 to 8 weeks, a realistic year, and how fast you lose it if you stop.
Do Breathing Exercises Increase VO2 Max? What the Research Says

The honest answer on whether breathing exercises raise VO2 max, what respiratory muscle training actually improves, and what moves the number.
Whoop VO2 Max: How It Works, How Accurate It Is, and My Own Data

How Whoop estimates VO2 max, what the accuracy numbers mean, and a real trend from a year of training.
REHIT Workout: The 10-Minute Protocol That Raises VO2 Max

Two all-out 20-second sprints in a 10-minute session. The research behind reduced-exertion HIIT and the exact protocol.
Fitbit VO2 Max: Where to Find It, How Accurate It Is, by Model

Where the Cardio Fitness Score lives, how each model estimates VO2 max including the new Fitbit Air, and how to raise it.
Stamina vs Endurance: The Real Difference, Explained Simply

Clear definitions of stamina, endurance, cardio, and conditioning, a comparison table, and the one measurable engine that drives all four.
Why Did My VO2 Max Drop? 6 Reasons and How to Get It Back

The six real reasons a VO2 max falls, which are just wearable noise, and how to get it back.
Tabata vs Norwegian 4x4: Which Interval Protocol Is Better?

The two most cited interval protocols compared head to head: research, VO2 max gains, time cost, and which one fits your goal.
How to Build Endurance and Stamina: The Complete Guide

The 80/20 method, the aerobic engine behind both endurance and stamina, cited evidence, and a realistic timeline for building lasting fitness.
How to Build Endurance for Running: The 80/20 Method with Heart Rate Targets

The 80/20 method with real heart rate targets, a run/walk timer preset, and a realistic timeline for building running endurance.
Circuit Training: How to Build, Time, and Progress a Circuit Workout

Work and rest times by goal, five ready-to-run circuits with timer presets, and what the research says about circuits and VO2 max.
Heart Rate Zones Explained: What Your Heart Rate Should Be in Each Workout

The five HR zones, your max heart rate, and the target HR for the work and recovery phases of HIIT, Tabata, and the 4x4.
Hybrid Athlete Training: How to Build Strength, Muscle, and a Big Engine

What a hybrid athlete is and how to train strength, muscle, and endurance together without the interference effect.
What Is Hyrox? The Fitness Race Explained and What Decides Your Time

The full Hyrox format, the 8 stations, and finish times, plus the one factor that decides your time.
Hyrox Workouts: The 8 Stations, Sample Sessions, and How to Train Them

The 8 stations, sample Hyrox workouts, and the engine work that lowers your time.
Hyrox Training: How to Improve VO2 Max and Drop Your Time

Why your aerobic engine decides your Hyrox time and the exact VO2 max training to drop it, on iPhone and Apple Watch.
Interval Timer App for Workouts: How to Program HIIT, Tabata, EMOM, and Circuits

What makes an interval timer app worth using, plus how to program HIIT, Tabata, EMOM, and circuit workouts in the PEAKVO2 app on iPhone and Apple Watch.
Norwegian 4x4 Training Plan: Week-by-Week Guide with the PEAKVO2 App

An 8-week Norwegian 4x4 plan that takes you from first session to measurable VO2 max gain, with the exact PEAKVO2 app and Apple Watch setup.
HIIT Workouts for Women: 6 Sessions and How to Train Around Your Cycle

Six HIIT workouts for women plus cycle-phase training, modifications for over 40 and postpartum, and the full PEAKVO2 app setup.
HIIT Workouts for Fat Loss: 6 Sessions and What the Research Actually Says

Six HIIT workouts for fat loss with timer-driven structures, the honest research on HIIT vs steady-state, and how often to train.
Training for Muscular Endurance: Exercises, Programs, and the Science

The complete guide to muscular endurance. Exercises, programs for beginner through advanced, the physiology, and how to program sets, reps, and rest.
Endurance Training Workouts: 10 Sessions to Build Lasting Fitness

10 endurance workouts with exact parameters, a 4-week program, tracking methods, and common mistakes to avoid.
Beep Test for Soccer: Scores by Position, Standards, and Training Plan

Score standards by position, how elite leagues use the beep test, Yo-Yo comparison, and a 6-week training plan.
HIIT Treadmill Workouts: 6 Interval Sessions for Every Fitness Level

Six treadmill interval sessions with exact speeds and inclines. Beginner walk-run to advanced sprint protocols.
15 Best Exercises for HIIT Workouts (With Interval Structures)

15 exercises that work for HIIT, organized by category with interval structures, modifications, and sample workouts.
Tabata Workouts: What They Are and How to Do Them Right

The complete guide to Tabata training. 6 workouts, a 4-week plan, the original 1996 study, and how to get the most out of 4 minutes.
Interval Training for Running: Workouts, Programs, and Plans

Five running interval workouts, an 8-week program, and plans from 5K to half marathon with pace guidelines.
Interval Training for Beginners: What It Is and How to Start

What interval training is, why it works, and three beginner workouts to get started. Science-backed guide with a 6-week progression plan.
Best Fitness Tracker for VO2 Max: 6 Devices Compared

Apple Watch, Garmin, Whoop, Oura, Fitbit, and Polar compared. How each estimate works, validation studies, and which device fits your training.
VO2 Max for Women: What's Different and How to Train

How women's VO2 max differs, menstrual cycle and menopause effects, iron, and the best training approach.
VO2 Max Test: What to Expect, How to Prepare, and Is It Worth the Cost?

What to expect at a VO2 max lab test. Preparation, protocols, costs, results, and how lab tests compare to wearable estimates.
Lactate Threshold: Heart Rate, % of VO2 Max, and How to Raise It

Lactate threshold heart rate, % of VO2 max by training status, how to find yours, and the best training methods to raise it.
Zone 2 Training: The Complete Guide to Building Your Aerobic Base

The complete guide to zone 2 training. Heart rate zones, sample workouts, the science of aerobic base building, and why it matters for VO2 max.
How to Improve VO2 Max: The Complete Evidence-Based Guide

Every proven method to raise your VO2 max. HIIT protocols, zone 2 training, strength work, nutrition, recovery, and realistic timelines.
The Cooper Test: 12-Minute Run to Estimate Your VO2 Max

How the 12-minute run works, what your distance means, and how to estimate your VO2 max.
VO2 Max by Age: Chart of Normative Scores and What's Good

VO2 max chart by age and sex, what counts as a good score for each decade, and how to compare against elite athletes.
How to Improve Your Garmin VO2 Max Estimate

What your Garmin score means, how it's calculated, and the fastest way to raise it.
The Beep Test: Scores, Levels, and VO2 Max Estimation

How the 20m shuttle run works, what your score means, and how to estimate your VO2 max.
Norwegian 4x4 Protocol: Proven HIIT to Raise VO2 Max

The most researched HIIT protocol for improving VO2 max. Exact intervals, heart rate zones, science, and training plan.
How to Improve Your Apple Watch Cardio Fitness Score (VO2 Max)

What your score means, why it might be low, and the fastest way to raise it.