There are many reasons why we choose to cycle, but there’s no denying that keeping in good shape is a big plus point.
As well as strengthening your heart, lungs, muscles and providing you with lots of health benefits, cycling is also a rather good way to knock off any excess flab, by burning fat for fuel as you ride. But if fat burning is your main goal, how hard should you be riding to maximise fat loss?
The scientific consensus is that you should ride at your ‘Fatmax’ intensity – ie the intensity that maximises the rate of fat burning. For the majority of cyclists with reasonable fitness, the Fatmax intensity is thought to occur at around 70 per cent of maximum heart rate or within ± five beats per minute of this figure.
Elite cyclists may have a Fatmax nearer to 80 per cent of maximum heart rate while beginner/unfit cyclists will probably have their Fatmax at around 65 per cent of their maximum heart rate. However, a study into Fatmax and training intensity by German scientists brings these assumptions into dispute.
In the study, researchers set out to discover the riding intensity that produced the maximum amount of fat burning during longer-intensity (one-hour) rides in 16 reasonably fit male cyclists.
To do this, each rider first underwent an incremental test to exhaustion to find out his maximal oxygen uptake (aerobic) capacity – also known as VO2 max.
They then used conventional Fatmax calculations to determine the riding intensity that should have produced the highest rate of fat burning in the cyclists – around 60 per cent of VO2 max (roughly equivalent to 70 per cent maximum heart rate).
All the cyclists then completed three separate one-hour riding trials. One of these was at the calculated Fatmax intensity (60 per cent VO2 max), while one was at a significantly lower intensity (52 per cent VO2 max) with the third at a much higher intensity (70 per cent VO2 max).
As well as collecting expired air from the cyclists to determine how much fat they were burning in each trial, the researchers also recorded the cyclists’ heart rates and levels of blood lactate (a measure of muscular fatigue).
In a nutshell
As expected, the heart rates and blood lactate measurements matched the riding intensities – they were lowest in the low-intensity trial and highest in the high-intensity trial. What surprised the researchers, however, was that the rate of fat burning was exactly the same at each of the three riding intensities. In other words, there was simply no evidence of an optimum ‘Fatmax intensity’ for burning fat.
It’s important to stress that this is just one study with a relatively small group of subjects. However, if these results are repeated in subsequent studies, the whole Fatmax theory could be thrown into question, with obvious implications for riding intensity prescription.
Given that the rate of fat burning was sustained at just 52 per cent of VO2 max, perhaps the take-home message could be that it’s better to ride for longer at a slower pace to maximise the amount of fat burned while keeping the total training load low.
Riders performing higher intensity workouts can relax in the knowledge that they are still burning the same amount of fat per hour as in lower-intensity workouts. As to why the amount of fat burned remained the same, one possible explanation is that at 52 per cent of VO2, these riders had already reached their Fatmax. This would mean that any extra energy required had to be supplied from carbohydrates.
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Int J Sports Med. 2013 Sep 10. [Epub ahead of print].
This article was first published in the November 21 issue of Cycling Weekly. Read Cycling Weekly magazine on the day of release where ever you are in the world International digital edition, UK digital edition. And if you like us, rate us!