The Benefits of Polarized Training

By Siegfried Mortkowitz

The most common advice for building cycling fitness is to take slow and steady rides, which usually entails three or even four months of long, low-intensity rides to gradually strengthen your aerobic base and build up your stamina. It works but it requires having three, four or even six hours available every day for those long rides. However, a recent study from Ghent University in Belgium found that training at different intensities, or training zones, was more effective than riding at one intensity over long periods.

The researchers looked at the amount of time cyclists spent in three different zones: Zone 1, below aerobic threshold where you can easily ride for hours; Zone 2, between aerobic threshold and anaerobic threshold or easy-hard; and Zone 3, above anaerobic threshold where the suffering begins. Those who spent the most time in Zones 1 and 3 instead of Zone 2 enjoyed significant gains in their anaerobic power. This strategy is called polarized training, which involves alternating between hard and easy days or hard and easy riding periods. Polarized training calls for working at the extremes of riding intensity, that is, you switch from very intense to relaxed riding.


According to exercise physiologist Paul Laursen, of the training service lab Plews and Prof, “Your [fitness] ‘base’ comes down to your mitochondrial capacity. Research shows that while longer, lower-intensity exercise increases the number of mitochondria in your cells, high-intensity training makes those mitochondria more powerful.” Mitochondria are membrane-bound cell organelles (singular: mitochondrion) that generate most of the chemical energy needed to power the biochemical reactions in your cells. In simpler words, they are the powerhouses of the cell because they help turn the energy we take from food into energy that the cell can use. So, having powerful mitochondria in your cells makes you a more powerful cyclist.

In addition, when you do a set (or especially multiple sets) of high-intensity intervals, your heart rate stays elevated even during your “recovery” periods, that is, when you are cycling at a comfortable pace. This benefits your aerobic energy systems, especially as your training session progresses. So, interval training increases cycling endurance, even if you’re already fit. “Our research has found that when well-trained cyclists performed two interval sessions a week for three to six weeks, their VO2 max, peak aerobic-power output, and endurance performance improved by 2 to 4 per cent,” Laursen said.

He noted that the best way to build endurance is to mix the distribution of your training intensity so that about 80 per cent of your rides are at Zone 2 intensity, in terms of heart-rate zones, and about 20 per cent are at high and very-high intensities or a blend of zones 3 to 5 throughout the week. These intervals should range from 30 seconds to 5 minutes at very high intensity, which makes your fast-twitch sprint fibres more resistant to fatigue over time.

“Performing three to six of these leg-burning efforts, allowing one to two minutes of recovery in between, can have impressive effects,” Laursen said. And you can increase the number of reps and their intensity as you get more fit. It is best to carry out these sessions twice a week, with at least one day of recovery in between. And remember to always eat a balanced diet, get enough sleep and listen to your body. It will tell you when enough is enough.