MAF vs Zone 2: What's the Difference?

What is MAF Training?

MAF stands for Maximum Aerobic Function. Developed by Dr. Phil Maffetone over four decades of clinical work with endurance athletes, the MAF method uses the 180 Formula to calculate a personalized aerobic heart rate ceiling. The formula starts with 180 minus your age, then applies adjustments based on your health history, training consistency, injury status, and medication use. The result is an upper limit specific to you, not a generic number shared by everyone your age.

Your MAF training zone is the 10 bpm window below that ceiling. All easy runs, base-building sessions, and recovery workouts should stay within this range. Over months of consistent MAF training, your pace at the same heart rate improves, a measurable sign that your aerobic system is getting stronger. Six-time Ironman World Champion Mark Allen famously used this method to build the aerobic engine that powered his career.

What is Zone 2 Training?

Zone 2 is part of the traditional five-zone heart rate model. It is typically defined as 60-70% of your estimated maximum heart rate, calculated using formulas like Tanaka (208 - 0.7 x age). Zone 2 training targets the same goal as MAF: building aerobic fitness, improving fat oxidation, and increasing mitochondrial density. The difference is in how the target heart rate is determined.

Because Zone 2 is a percentage of an estimated max HR, it treats every person of the same age identically. A 35-year-old recovering from surgery and a 35-year-old competitive marathoner would get the exact same Zone 2 range. The formula has no mechanism to account for health status, training history, or current fitness level.

Why They Differ

The key difference is personalization. MAF adjusts for real-world factors: illness, injury, medication, training gaps, and competitive experience. For healthy, consistently training athletes, MAF and Zone 2 often land within 5-10 bpm of each other. But for athletes dealing with health challenges, returning from injury, or starting a new training program, the MAF number can be 15-25 bpm lower than Zone 2. That difference matters because training too high when your body needs recovery defeats the purpose of aerobic base building.

When to Use Each Approach

If you have a clean bill of health and have been training consistently for years, either approach will get you in the right ballpark. Zone 2 is simple to calculate and widely understood. If you have any health considerations, are returning from a break, or want a method that adapts to your individual situation, MAF is the better starting point. Many coaches use MAF for the initial aerobic base phase and then layer in Zone 2 and higher-zone work as fitness develops.