67. TRAINING AT FATMAX WITHOUT ANY LAB TEST

Photo by Michael Ender on Unsplash

‘Fatmax is the intensity at which the maximum rate of fat oxidation is elicited’.

This is usually expressed in power output or heart rate range (for example 220-240 W or 130-140 bpm). Many cyclists want to know their fat max to train at this intensity. Why? The training specificity principle states that closer the training routine to the desired outcome, better the adaptations obtained. Following this principle, if we train at fatmax intensity we are stimulating maximally the fat metabolism and this could improve the ability to use fats as fuel during exercise and so durability.

Why training at fatmax and becoming better to use fats as fuel could improve durability?

We saw that durability is linked (in part) to preserve muscle glycogen levels and carbohydrates availability. Even in very lean individuals, fats are a virtually unlimited energy store while carbs are not.

Energy stored (kcal) in the body. Calculations are based on Maunder et al. 2018 (1) and consider a 70kg man with a 10% body fat

So, being capable to use as much as possible fats (the unlimited resource) during exercise could make spare carbohydrates/glycogen (the limited resource), and increase durability.

It is important to acknowledge that, while this approach seems intuitively reasonable and widely used on the field, no study has yet demonstrated this.

In a previous ‘in depth' post (read more here), we saw that fatmax should occur approximately at ~60-70% FTP/second threshold or 65-75% Heart Rate max. How did we make this estimation? From a big dataset (2) used by Ed Maunder and Colleagues (Auckland University of Technology) which highlighted that in 201 lean trained males fatmax was elicited at 56±8 %of VO2max. Considering that VO2max is ~120% of power at second threshold/FTP, with some simple math we derived that:

Fatmax = ~60-70% FTP/second threshold or 65-75% Heart Rate max

However this was just a calculation without a direct measure. Does it really hold true?

Can we be sure that we are training at Fatmax without any lab test?

Data from a hot off the press study published by Meixner and Colleauges (University of Würzburg) on Translational Sports Medicine in 2025 can help to answer this question. (1)

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WHAT DID THEY DO?

• They recruited 50 trained amateur cyclists (VO2max: 54)

• The cyclists performed an incremental step test (100 W + 25 W every 3min) to detect and compare the intensities (power) at which the following physiological markers occur:

  • Fatmax

  • 72% of Maximum Heart Rate

  • 82% of Maximum Heart Rate

  • First Ventilatory Threshold (VT1)

  • Blood Lactate Concentration = 1.5 mmol/L

  • Blood Lactate Concentration = 2mmol/L

  • Blood Lactate Concentration = 2.5 mmol/L

  • Blood Lactate Concentration = baseline + 0.5 mmol/L

  Before the incremental test started, participants ingested 35 grams of carbs, so the measurements were taken in a similar nutritional scenario of a training session on the road.

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WHAT DID THEY FIND?