MAF Training review – Part 6 When You Need MAF

My previous articles about the MAF Method discourage using the age-related formula for low heartrate training. But in this post I’m taking a more positive angle because there’s a reason people went to Phil Maffetone and he was able to help them. So while, I’m not a fan of the age-related formula, I am a fan of building good endurance which relates to what Maffetone refers to as MAF – Maximum Aerobic Function. While I’m not going to advocate using his formula, I am going to detail and explain the circumstances where a block of endurance training could be useful.

A parkrunner I know is a very capable runner yet, in a decade of running, his progress has been very limited. In fact, he’s barely knocked a minute off his parkrun time. When we first met he’d been running again for perhaps six months. He’d been a talented youngster, quit and now returned to running as he approached forty. It hadn’t taken much training to achieve a twenty minute parkrun yet in all the running since he has barely scraped under nineteen minutes. Despite training five days per week, six at one stage, he really hasn’t made much progress.

His years of running have been blighted by Achilles’ problems. Whenever he starts to train harder with speedwork his Achilles becomes sore and limits his running. He then backs off the pace until long after the Achilles has healed, only to restart the speedwork and go through the same issues. Until recently he was able to run a 19:30 parkrun at full effort but over the last year he’s developed a hamstring injury and is struggling to break twenty minutes. On the tougher local courses, he can’t even break twenty-one minutes!

If he could go to Phil Maffetone, I’m sure MAF would get him back to health and restructure his training to help him improve. I’d still argue against using the age-related MAF formula because he’s over fifty and training at 125 (further five beat reduction for recent injury) isn’t going to produce decent longterm results. Yet, as you’ll see in the next section, he’s clearly not getting the aerobic development Maffetone would encourage and is running around almost every day of the week at heart-rates which are too high.

A typical week’s training when you need MAF

He typically runs five days per week – three midweek, a parkrun on Saturday which is always a faster effort, a Sunday run which is his longest of the week while the Wednesday run tends to be slightly shorter. He gives himself two rest days which, being on Monday and Friday, space the week’s training out nicely. All in it’s not a bad training structure to follow. Here’s the heart-rate graphs from those five days of training.

I’ve put a yellow line to indicate where a heart-rate of 150 occurs and you can see that on every run he is reaching and surpassing it for a decent portion of the time. In fact, at parkrun the heart-rate reaches 170+ and most days he’ll be hitting the 160s at some stage of the running. He’s not just exceeding 150bpm but exceeding it significantly on almost every run.

I consider the overall amount of time spent running each week to be an issue. Totalling about 25 miles per week in 3hr 20mins it’s not enough for a distance runner. Of course everybody leads different lives and has different priorities so I can’t be too critical. Yet at less than an hour the Sunday run isn’t long enough and it should surely be possible to find more time for it. If he was an 800m runner, an hour might be long enough but he isn’t; he describes himself as a 5K / 10K runner. Apart from a couple of ten mile races and a half marathon; 10Ks have been the furthest distance raced in all these years. This overall lack of training volume is part of the problem.

The average pace for the week is 7:45/mile and the Wednesday run is the slowest at 8:11/mile. Given a parkrun time that is just breaking twenty minutes, Jack Daniels’ VDOT tables suggest Easy runs should be somewhere around 8:30/mile pace. So again, alongside the evidence of the high daily heart-rates, we’re getting an indication that there isn’t enough genuinely easy running taking place.

There’s two more problems these stats don’t reveal. On each of the training runs he stops to cross roads which give him one to three minutes recovery on any run. There’s over nine minutes of stops built into these runs. It may seem picky but anyone who has done distance training knows a break is refreshing. If you’re running anaerobically those breaks allow you to recharge the batteries and keep pushing (too) hard. Now you may argue it’s impossible not to stop but, with good timing and route choices it can be avoided. I often go weeks without needing to stop on any of my runs simply by running on roads with low levels of traffic, early in the morning and being flexible about when and where I cross roads. I will happily run an extra fifty paces up a road to let traffic die down before crossing it. But obviously do the safe thing.

The other unseen problem in these graphs is there’s some decent hills on the routes. He’s trying to maintain the same pace up and down them but that pushes the effort up which explain some of the higher heart-rates.

Graphing all those runs differently we can see the time spent in a MAF-HR zone of 130 or less; a middle zone of 131-150 which is usually safe for older runners to train at and a 150+ zone where the training effect is large but also takes time to recover from.

It’s clear he’s running hard five days per week with heart-rates hitting the 150+ mark. You would think the two rest days would be enough but they aren’t. What’s actually happening is the muscles are being trained anaerobically. The days after the rest days (Tuesday and Saturday) are faster runs because the muscles are refreshed but all that allows is for him to go out hard and reinforce the anaerobic training. There is no aerobic development. One of the benefits of day-in, day-out training is it leaves the legs somewhat fatigued to the point where they have to go slower and that helps the aerobic development.

The main consequences of this approach are that he’s getting injured and not improving.

What good training looks like

Injuries were the sort of thing Maffetone was happy to dive in and sort out. As I have stated repeatedly, I’m not a believer in the age-related formula but I am a believer in what Maffetone was trying to get his clients to do which is stay healthy and get faster by building an aerobic base through good endurance training.

My own training during this period saw me run nearly double the training our Needs MAF runner was managing. I was just shy of fifty miles taking 6hr 24mins yet we had the same average pace for the week at 7:45/mile. Despite all this extra mileage I’d been training every day for almost three years without illness or serious injury. While I picked up a couple of glute strains along the way (which came from trying too hard in speedwork) neither lasted more than a week and I was still able to run. While our parkrun times are similar, my base endurance is improving and I am positioning myself to go faster in the longterm.

You can see I run every day but only push harder on two days (Tuesday and Friday). There’s a few little glitches on my heart-rate monitor particularly Wednesday which highlights the problem of accuracy with heart-rate training but otherwise I’m comfortably well below 150HR on my recovery days. My Sunday long run sometimes scrapes into the red but the training effect I’m interested is in building endurance on those runs. Even a good ninety minute run is still only a hard, aerobic effort. Where the Needs MAF runner has to take two rest days every week, I’m getting out there and running on them too.

Another intriguing detail of our training weeks is that we accumulate the same amount of 150+ ‘red zone’ training time but my extra running accumulates time and fitness in the supporting zones while allowing the body to recover from the harder sessions. If I tried to run hard every day like he does, I’m sure I would be getting injured too.

We’re both fifty years old and Maffetone would like us to be doing all our training to a heart-rate of 130 or below. I don’t believe in that but I do total over an hour of my weekly running at this level and it’s usually in the first couple of miles of the runs while my body warms up. This is important – I’m listening to my body to get an indication of how it feels and whether I can push hard. Maffetone talks about doing warm-ups in his book but the people who think he’s only about low heart-rate training miss this.

On days following a harder effort I find my legs don’t want to do too much and it is a struggle to get the heart-rate up. My legs can be glycogen-depleted so I just jog along to aid recovery. If I tried, I could probably push to higher levels especially if I’d had a day off but I don’t try to push it every day and that was Maffetone’s message.

80-20 training

Much of Maffetone’s work occurred in the 80s and 90s when heart-rate monitors were still new. The science of exercise physiology has progressed a lot in recent years. What we now know, due to the work of Stephen Seiler, is that elite athletes tend to split their training into 80% below lactate threshold and 20% above it.

Throughout this post I’ve referenced a HR of 150bpm. Be careful – 150HR is not THE definitive value to use; it’s the data that was available to me. That the Needs MAF runner trains somewhere around this level most days shows it is probably somewhere around his own.

One hundred and fifty is close to where my lactate threshold heart-rate usually lies and I calculate I have a 76-24% split above and below it. That’s within the bounds of 80-20 training. On the other hand, the Needs MAF runner’s training split comes in at 54-46%. It begins to explain why he’s failing to make progress and getting injured when he starts to do even more intense work!

Arguably it may be wrong to use 150HR to split his training but it’s clear he’s training too hard every day because his body is letting him know through injuries and lack of progress. You can also see when he runs 30secs/mile slower on Wednesdays, he has lower heart-rate so it would be easy for him to include more genuinely easy-paced runs. Doing that, as Maffetone outlined is the key to staying healthy and injury-free.

Although I’ve been explaining all this using data you don’t need a heart-rate monitor to know whether your training is going well. Just a bit of common sense and listening to your body will tell you. When it creaks and groans it’s time to back off.


My six posts on MAF training are among the most detailed and honest articles about it on the internet and well worth reading. I’m trying to help runners get past the idea that training to a single number on a heart-rate monitor is the answer to all their problems. Good training involves scheduling the right mix of sessions at the right times. A block of endurance training like Maf suggests is just one part of what you need. My years of training and coaching allow me to know what to do and when to do it to help runners get fitter, faster and healthier. If you too would like me to help you then please contact me with details of your running and how you think I can help you.

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