IMAT | How To Find Your Maximum Aerobic Heart Rate Using A Different Approach – Mike Trees

November 19, 2022 | By DLake

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Ever tried that Maffetone 180-age formula to calculate your max aerobic training heart rate, only to think, “Uh, this feels a little too… slow?” If so, you’re not alone—especially if you’re an older runner. Let’s talk about a tweak that might just be your answer.

Introducing: IMAT (Individual Maximum Aerobic Training Heart Rate)

IMAT is a more personalized way to figure out your max aerobic training heart rate, and it’s based on your actual max heart rate rather than a general formula. So if the Maffetone MAF Test and MAF heart rate zones approach has been leaving you feeling like you’re sandbagging it, IMAT might be a better fit.

Here’s the lowdown:

What’s IMAT, Anyway?

This was derived from Mike Trees (@run.nrg), our podcast co-host and coaching partner.

IMAT = Max Heart Rate – 40

Yep, it’s that simple. Your max heart rate (Max HR), minus 40. This formula comes from Mike Trees (@Run.nrg on Instagram) as an alternative for those who feel a little constrained by the Maffetone 180-age method.

Here’s an example to bring it to life:

For someone like Mike, at age 58, the Maffetone 180-age formula gives a target aerobic HR of 123 bpm. That’s based on a max HR of 163 (using the traditional 220-age formula). But here’s the catch: Mike’s real max HR is actually 173 bpm, not 163.

So, using IMAT, his max aerobic training heart rate becomes:

173 – 40 = 133 bpm

That’s a whole 10 beats higher than Maffetone’s formula—and it actually feels right for him.

This isn’t a total departure from the Maffetone approach. It’s just a tweak that makes it a bit more… you. If you know your true max HR, IMAT offers a better fit, respecting the Maff principles while dialing things in to your actual physiology.

Caution: This Test Isn’t for Everyone

Before you dive into finding your max heart rate, a quick heads-up: this test is no joke. Getting an accurate max HR reading is intense—borderline brutal. You’re pushing yourself to your limit here, and that’s not something to take lightly. So, let’s go over who shouldn’t be jumping into this just yet.

To tackle this test safely and accurately, here’s what you need:

• A Solid Fitness Base: You should already be doing regular cardio and have a good aerobic foundation. If you’re just starting or haven’t been running regularly, this might be too much too soon.
• Some Hard Sessions Under Your Belt: If you haven’t done intense intervals or a hard tempo session in a while, ease into those first. Sprinting all-out without recent experience can increase your risk of injury.
• Good General Health: If you’re recovering from an illness, have heart issues, or are dealing with any nagging injuries, hold off. This test requires you to be in decent shape to avoid any health scares.
• Mental Preparedness: Hitting your true max HR takes grit. You’ll be pushing into that uncomfortable zone where every step feels like a mini-battle. If you’re not mentally up for it, it’s better to wait until you are.
• Freshness Matters: Don’t try this on the tail end of a hard training week or after a series of tough workouts. Your body needs to be fresh and recovered, ideally with a rest day or an easy day beforehand, so you’re ready to give 100%.

The bottom line? Don’t rush into this unless you’re fully prepared. It’s an intense test, and for it to be safe and effective, you need the right mix of fitness, freshness, and mental readiness.

So, How Do You Find Your Max Heart Rate?

If you’re ready to go beyond the “220 minus age” calculation, here are two DIY methods for finding your true max HR out in the wild:

1. The 600/400/Hill Method (Most Accurate Field Test)
   Try to have a track, straight flat section and a hill available for this.
   
   • Warm Up: Start with a solid jog to get the blood flowing – 10 – 15 minutes is good. Then do 4 windups/run thoughts (hard 20-30 second sprints) with 30 seconds rest each. Rest a full 3 minutes. (walk around and jog slowly)
   • Sprint 1000m All Out: Push as hard as you can for the full distance.
   • Rest 60 Seconds
   • Sprint 400m All Out: Go again, this time for 400m. This will hurt and suck
   • Rest 30 Seconds
   • Hill All Out: Go again, this time but up a hill for 30-40 seconds. This will hurt and suck
   • Check your highest sustained heart rate after you finish: Note it.
   • Recovery: Easy Run Down
   • Hill All Out: Go again, up a hill for 30-40 seconds — all you can do it. This will hurt and suck.
   • Check your highest sustained heart rate after you finish. Note it. If it is lower, do it again one more time. If it is the same, you’re done. If it is higher, do it again one more time.
   • The goal is to get the same hr twice that’s your max. Only repeat the hills 3x times as you will be quite tired.
2. The 5K Race Method (Less Accurate, but a Good Backup)
   • Use the highest heart rate recorded during a full-out 5K race (if done on a hot and humid day, even better!). A regular training run won’t cut it; you’ve gotta be going all-out, to the point where you feel like you could barely walk afterward. If you’re feeling even a little okay after, you probably didn’t hit your max HR.

Neither of these is perfect, but they’re more reliable than “220 minus age.” For true accuracy, of course, a lab test is the gold standard. But if you’re like most of us who don’t have that kind of access, these two methods should get you close.

Try It Out and See How You Feel

If you’re curious about IMAT and this resonates with you, give it a try! Play around with the formula and see how it feels in your training. Just remember: endurance training isn’t a one-size-fits-all thing. This approach respects the foundations of aerobic training while adjusting to your body.

Oh, and if you find this helpful, spread the word to your running crew—sometimes, small tweaks like these can be a game-changer.