MAF Training Method: Phil Maffetone's Low Heart Rate Approach

The MAF method — Maximum Aerobic Function, developed by Dr. Phil Maffetone — is one of the most well-known approaches to aerobic base training. It centres on one idea: train below a specific heart rate ceiling to develop your aerobic system, and don't go above it. The simplicity is the point.

What is the MAF Method?

The MAF method is an approach to training that prioritises aerobic development above everything else. The core principle: keep your heart rate at or below your "MAF heart rate" for the majority of your training. No exceptions for hills, no "just a little faster", no racing friends on easy days.

Maffetone argues that most endurance athletes are chronically over-trained in their anaerobic system and under-trained aerobically. By forcing athletes to slow down, the MAF method allows the aerobic system to develop fully — which ultimately produces faster race times with less injury and burnout.

The 180 Formula: How to Calculate Your MAF Heart Rate

Maffetone's 180 Formula gives you a single heart rate number — your MAF ceiling:

Start with 180
Subtract your age
Adjust based on your health and training history:

Adjustment	Condition
Subtract 10	Recovering from major illness, surgery, or on regular medication
Subtract 5	Injured, have regressed in training, get more than 2 colds/year, or have allergies
No change	Training consistently for 2+ years without problems
Add 5	Training consistently for 2+ years with measurable improvement and no injuries

Example: A 35-year-old runner who has been training consistently for 3 years without injury:

180 − 35 + 5 = 150 bpm (MAF heart rate)

Your training zone is then MAF minus 10 to MAF. In this example: 140-150 bpm.

How MAF Training Works in Practice

Once you know your MAF heart rate, the rules are simple:

Every training run stays at or below your MAF heart rate
Walk when you need to — on hills, when you start out, whenever your HR hits the ceiling
Warm up gradually — the first 10-15 minutes should bring your HR up slowly to your MAF range
Cool down — the last 10 minutes should be easy, letting your HR drop

The MAF Test

Maffetone recommends a monthly test to track progress: run a set distance (typically 5km or a few miles) at your MAF heart rate and record the time. Over months, your pace at that heart rate should get faster. This is the clearest evidence that your aerobic system is developing.

The MAF test is essentially measuring the same thing as tracking pace at a given heart rate, or monitoring cardiac drift — they're all ways to quantify aerobic efficiency.

What to Expect When You Start

Honest warning: the first few weeks of MAF training can be humbling.

You will be slow. If you've been running most of your miles at moderate intensity, staying under your MAF heart rate might mean running 1-2 minutes per km slower than usual. Some runners need to walk up hills.
It will feel too easy. You'll finish runs feeling like you didn't do anything. That's the point.
Other runners will pass you. Your ego will take a hit. Accept it.
Progress is slow at first. The first 4-6 weeks might show little improvement. Stick with it.

After 6-12 weeks, most runners start seeing their pace improve at the same heart rate. After 3-6 months, the improvement is typically significant — often 30-60 seconds per km faster at the same MAF heart rate.

MAF vs. Zone 2 Training: What's the Difference?

MAF training and Zone 2 training are conceptually similar — both prioritise low-intensity aerobic work. The main differences:

Aspect	MAF	Zone 2
HR ceiling	180 − age (single number)	60-70% of max HR (range)
Intensity mix	100% below MAF (purist approach)	80/20 polarised (allows hard sessions)
Hard sessions	Not until base is fully built	1-2 per week from the start
Approach	More prescriptive	More flexible

Neither is objectively better. MAF is stricter and works well for runners who need a clear rule to stop themselves going too hard. Zone 2 / polarised training is more flexible and allows some intensity, which many runners find more sustainable and enjoyable.

Who Benefits Most from MAF?

Runners who do every run at the same moderate intensity — MAF forces a genuine easy pace
Injury-prone runners — the low intensity reduces musculoskeletal stress
Runners coming back from a break — MAF rebuilds the aerobic base gradually
Ultra and marathon runners — where aerobic efficiency is the primary performance limiter
Older runners — aerobic fitness responds well at any age, and recovery demands less at lower intensities

Criticisms and Limitations

MAF training has its critics, and some of the criticisms are fair:

The 180 Formula is a rough estimate — it doesn't account for individual variation in heart rate. Some people's MAF number will be too high, others too low.
No speed work means no neuromuscular adaptation — running fast requires practising running fast. Pure MAF training doesn't develop this.
It's slow to show results — runners used to feeling like they "worked hard" may lose motivation.
It ignores heart rate zone nuance — a single number is simpler but less precise than a properly calibrated zone model.

A Practical Approach

For most runners, a blend works best: use the MAF heart rate as your easy-run ceiling, but don't avoid all intensity. Run 80% of your training at or below MAF, and use the other 20% for tempo runs, intervals, or races. This gives you the aerobic base benefits while maintaining the speed and running economy that come from harder sessions.

Track your MAF pace over time. If it's improving, the system is working. If it's stagnating after several months, you might need more training volume, better recovery, or a reassessment of your MAF number.