In this second interview between Simon Wegerif and Dr Phil Maffetone they cover the MAF method. Including how this training method can improve performance, fat burning efficiency and your heart rate variability (HRV).

Simon photoDr Phil Maffetone LCHF



Dr Phil has been prescribing the Maximum Aerobic Function (MAF) training method for decades. It involves calculating your own personal MAF heart rate and performing all training at or below that rate. In more recent years this has become easy to measure and perform and is now very widely accepted, more so than the lactate threshold approach.

The interview discusses how, when first developing the MAF method, initially working with runners, Dr Phil and his athletes quickly observed the benefits, including;

  • Maintaining gait efficiency (if the gait changes it impacts running economy).
  • Reduced aches and pains, fatigue factor (during workout and next morning) and muscle soreness.
  • Athletes built endurance to run for longer and the ability to recover faster.
  • Within a month or two athletes were running PBs in races.

Key takeaways from this interview include;

  • The MAF HR is also a HR that can be sustained throughout an endurance event. For example, one study showed Tour de France riders spent 70% of their ride at or below their MAF threshold. But you need to train muscles to do this.
  • In another case Dr Phil followed 223 seasoned runners through a 3-6 month base building period. During this time they only trained at MAF rate, no speed work. At end of base building period 76% ran a PB in 5k first time out, many others ran a PB the next time.
  • MAF training develops fat burning for two reasons;
    • Intensity level is relatively low, so stress is relatively low. Higher stress impairs fat burning.
    • When training at lower level, MAF HR, this allows aerobic muscle fibres to develop and support anaerobic muscles fibres. As you develop more aerobic fibres you have the ability to burn more fat.
  • Many athletes when trying the MAF method report that it feels too easy! Things elaborated on in Dr Phil’s response include;
    • Stressing the aerobic system doesn’t hurt like it does if you stress anaerobic system. Over stressing the body leads to the immune system, gut and intestinal tract being adversely affected and increasing the risk of inflammation. These will also be seen in reduced HRV.
    • Many people have poor functioning aerobic systems, you need to find the level to build that system up whilst gaining aerobic benefits.
    • If you start at too high a level you lose many training benefits and are forced to use the anaerobic system.
    • You will get faster and faster at the same HR, improving efficiency (your HRV will also improve during this time).
    • Too much high intensity work opens you up to poor health, injuries and ultimately lack of improvement.
    • Complaints of training too slowly quickly start to evaporate as athletes develop aerobic capacity!

Train fast to race fast = myth. Train slow to race fast! Otherwise you don’t enlist aerobic system, which for anything over a mile is essential for 99% of energy.

Get lots more information, including calculating you own MAF rate at, we particularly liked this new white paper An Introduction to MAF.