The Science
The Data
Individuals with the lowest VO2 max scores (<25 ml/kg/min) face roughly 4x the mortality risk over 10 years compared to those with the highest scores (45+). Even modest improvements from the lowest category produce significant reductions in death risk.[1]
Mortality risk decreases substantially with each increase in VO2 max level
VO2 Max Benchmarks by Age (ml/kg/min)
Use the tables below to see how your VO2 max score maps to a fitness classification for your age and sex. The goal is to reach the Good or Excellent range. Research shows that moving out of the lowest scores produces the greatest reduction in mortality risk.
Men
| Age | <25 | 25-30 | 30-35 | 35-40 | 40-45 | 45+ |
|---|---|---|---|---|---|---|
| 20-29 | Very Low | Low | Low | Below Avg | Average | Excellent |
| 30-39 | Very Low | Low | Below Avg | Average | Good | Excellent |
| 40-49 | Very Low | Low | Below Avg | Average | Good | Excellent |
| 50-59 | Low | Below Avg | Average | Good | Excellent | Superior |
| 60-69 | Below Avg | Average | Good | Excellent | Superior | Superior |
| 70-79 | Average | Good | Excellent | Superior | Superior | Superior |
Women
| Age | <25 | 25-30 | 30-35 | 35-40 | 40-45 | 45+ |
|---|---|---|---|---|---|---|
| 20-29 | Very Low | Low | Below Avg | Average | Excellent | Superior |
| 30-39 | Very Low | Below Avg | Average | Good | Excellent | Superior |
| 40-49 | Low | Below Avg | Average | Good | Excellent | Superior |
| 50-59 | Below Avg | Average | Good | Excellent | Superior | Superior |
| 60-69 | Average | Good | Excellent | Superior | Superior | Superior |
| 70-79 | Good | Excellent | Superior | Superior | Superior | Superior |
Benchmarks derived from ACSM normative data and the Mandsager et al. (2018) fitness classifications.
The Studies
VO2 max is not just a fitness metric -- it is one of the most powerful predictors of how long you will live and how well you will live. The research on this is extensive and unambiguous.
- Strongest Mortality Predictor: The Mandsager et al. study (2018) found that the risk reduction associated with high cardiorespiratory fitness exceeds that of addressing hypertension, diabetes, or smoking cessation. Moving from the lowest fitness group to just below-average reduced mortality risk by approximately 50%.[1]
- No Upper Limit of Benefit: Unlike many health markers where benefits plateau, the JAMA study found no ceiling on the mortality benefit of higher VO2 max. Even "elite" fitness levels (top 2.5%) continued to show lower mortality compared to "high" fitness, suggesting that more cardiovascular fitness is always better.[1]
- Massive Returns from Small Gains: The Cooper Center Longitudinal Study showed that the greatest mortality reduction occurs when moving from "low" to "moderate" fitness -- the first improvements matter the most. This means that even sedentary individuals who start a modest exercise program can expect significant health benefits.[2]
- Protects Against Chronic Disease: Higher VO2 max is independently associated with reduced risk of cardiovascular disease, type 2 diabetes, certain cancers, dementia, and depression. The Kodama meta-analysis found consistent protective effects across all of these conditions.[3]
The Plan
Zone 2 vs Zone 5: Understanding the Difference
- Zone 2 (Low-Intensity Aerobic): This is the intensity at which your body primarily burns fat for fuel and builds mitochondrial density. It improves the efficiency of your cardiovascular system, increases capillary density in muscle tissue, and builds your aerobic base. Think of it as building the engine.
- Zone 5 (High-Intensity / VO2 Max): This is maximal or near-maximal effort that pushes your cardiovascular system to its absolute limit. It stimulates increases in stroke volume (the amount of blood your heart pumps per beat) and directly raises your VO2 max ceiling. Think of it as increasing the engine's horsepower.
- Why You Need Both: Zone 2 builds the aerobic foundation that lets you recover from and sustain Zone 5 efforts. Zone 5 pushes the upper limit of your cardiovascular capacity. Without Zone 2, your recovery suffers and Zone 5 training becomes unsustainable. Without Zone 5, your VO2 max ceiling won't rise as quickly. The combination is more effective than either alone.[5]
The Right Intensity for Zone 2
Zone 2 training should be performed at what's often called "conversation level" -- meaning the intensity at which you could still hold a conversation with somebody, but with noticeably labored breathing. You should be able to speak in full sentences, but you wouldn't want to give a speech. If you're gasping for air, you're going too hard. If you can talk effortlessly without any breathlessness, you're not going hard enough.
Heart Rate Guide: Zone 2 is typically 60-70% of your maximum heart rate. A rough estimate of max heart rate is 220 minus your age. So for a 40-year-old, Zone 2 heart rate would be approximately 108-126 beats per minute.
The Talk Test: If you're exercising with someone (or on the phone), you should be able to carry on a conversation with some effort. Breathing is elevated and noticeable, but you're not out of breath. This is the simplest and most practical way to gauge Zone 2 intensity.
Key Principle: Zone 2 should be performed at a difficulty level where you can easily recover and do it again tomorrow. If a session leaves you exhausted or sore the next day, you went too hard. The goal is consistency over intensity -- doing this 3 times per week, week after week, for months and years.
Preferred Zone 2 Options
- Uphill Hike / Incline Treadmill: The best choice for most people. Walking at a brisk pace on a moderate incline (8-15% grade) naturally puts most people right in Zone 2 without the joint impact of running. Set a treadmill to 3.0-3.5 mph at 10-12% incline and adjust until you hit the conversation-level effort. Outdoor hill walking works equally well.
- Stair Master / Step Mill: An excellent option that provides steady, controllable Zone 2 effort. Set a moderate pace and maintain it. The consistent stepping motion is easy to sustain and low impact compared to running.
- Easy Cycling: Stationary or outdoor cycling at a steady, moderate effort. Keep resistance and speed at a level where you're working but comfortable.
- Easy Jogging: For those comfortable with running, a slow, easy jog at conversation pace works well. Many runners go too fast on easy days -- slow down more than you think you need to.
Zone 5: Tabata Training
Tabata training is a specific high-intensity interval protocol developed by Dr. Izumi Tabata and colleagues at the National Institute of Fitness and Sports in Tokyo. The original 1996 study demonstrated that this protocol improved both anaerobic capacity (28% increase) and VO2 max (14% increase) in just 6 weeks -- results that traditional steady-state cardio could not match in the same timeframe.[6]
The Protocol: 20 seconds of all-out maximum effort followed by 10 seconds of rest, repeated for 8 rounds. Total working time: 4 minutes. That's it. If you can do more than 4 minutes at the prescribed intensity, you are not going hard enough.
Key Point: The 20-second work intervals must be performed at absolute maximum effort -- 100% intensity. This is not "hard." This is everything you have. You should feel like you physically cannot continue by rounds 6-8. If the last few rounds don't feel brutal, increase your resistance or speed.
Preferred Zone 5 Options
- Air Bike (Assault Bike / Echo Bike): The best choice for Tabata training. The air bike provides unlimited resistance that scales with effort -- the harder you push, the more resistance you get. It engages both upper and lower body simultaneously, is low-impact on joints, and makes it nearly impossible to cheat on intensity. Tabata on an air bike: 20 seconds all-out sprint, 10 seconds easy spin, 8 rounds.
- Rowing Machine: An excellent alternative. The rowing machine also provides full-body engagement with scalable resistance and low joint impact. Tabata on a rower: 20 seconds maximum-effort rowing, 10 seconds easy rowing or rest, 8 rounds. Focus on power per stroke rather than stroke rate.
- Sprinting at a Track: If you don't have gym equipment, sprint intervals at a track work well. Run at maximum effort for 20 seconds, walk or rest for 10 seconds, repeat 8 times. Be cautious of hamstring and joint injury risk, especially if you haven't sprinted recently. Always warm up thoroughly.
- Burpees: A no-equipment option that can be done anywhere. Perform burpees at maximum speed for 20 seconds, rest 10 seconds, repeat 8 rounds. While effective for driving heart rate up, the technique breakdown at maximum effort can be a concern. Prioritize speed but maintain form.
Sample Weekly Schedule
Here's how a typical week of cardiovascular training might look. This can be combined with your strength training schedule (covered on the Strength page).
- Monday: Zone 2 -- 30 minutes incline treadmill or stair master
- Tuesday: Strength training (see Strength Plan)
- Wednesday: Zone 2 -- 30 minutes incline treadmill or stair master
- Thursday: Zone 5 -- Tabata protocol (4 min working, ~15 min total with warm-up/cool-down)
- Friday: Zone 2 -- 30 minutes incline treadmill or stair master
- Saturday: Rest or light activity (walk, hike)
- Sunday: Rest
This schedule totals approximately 90 minutes of Zone 2 training and one Tabata session per week. Combined with the minimum effective dose strength training, your total weekly exercise commitment is roughly 2-3 hours. This is sustainable, effective, and backed by the evidence.
Sample Zone 2 Workout
Duration: Approximately 30 minutes of sustained Zone 2 effort.
Example (Incline Treadmill): Walk at 3.2 mph, 11% incline for 30 minutes. Adjust speed and incline to maintain conversational-level effort.
Example (Stair Master): Set to level 5-7 (varies by machine) and maintain steady pace for 30 minutes.
Recovery: You should feel mildly fatigued after the session but fully recovered within an hour. If you feel wiped out, reduce the intensity next time. Remember: you need to be able to do this again tomorrow.
Sample Zone 5 Workout
Warm-up: 5 minutes of easy cycling or rowing at conversational pace.
Tabata Protocol: 8 rounds of 20 seconds all-out / 10 seconds rest (4 minutes total).
Cool-down: 3-5 minutes of easy movement and stretching.
Total Time: Approximately 12-15 minutes including warm-up and cool-down.
Important: Although the Tabata portion is only 4 minutes, this will be your entire workout for the day. A properly executed Tabata session is so demanding that additional training is counterproductive. Your body needs the rest of the day (and potentially the next day) to recover. Do not combine Zone 5 training with strength training or Zone 2 training on the same day.
References
- Mandsager K, Harb S, Cremer P, Phelan D, Nissen SE, Jaber W. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open. 2018;1(6):e183605.
- Blair SN, Kohl HW, Paffenbarger RS, Clark DG, Cooper KH, Gibbons LW. Physical fitness and all-cause mortality: a prospective study of healthy men and women. JAMA. 1989;262(17):2395-2401. (Cooper Center Longitudinal Study)
- Kodama S, Saito K, Tanaka S, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. JAMA. 2009;301(19):2024-2035.
- Ross R, Blair SN, Arena R, et al. Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign. A Scientific Statement From the American Heart Association. Circulation. 2016;134(24):e653-e699.
- Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform. 2010;5(3):276-291.
- Tabata I, Nishimura K, Kouzaki M, et al. Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Med Sci Sports Exerc. 1996;28(10):1327-1330.