What actually happens to your body as a result of “Zone 2” training?

Zone 2 is a term that is mentioned a lot in endurance sports. What exactly happens in your body during Zone 2 training? And why is it so important for endurance athletes?

Zone 2 training is typically done at an intensity of around 60-75% of your maximum heart rate or around 55-75% of your FTP. This means you are working at a relatively low intensity, where you are still able to hold a conversation. Despite the low intensity, Zone 2 training has been shown to have significant benefits for endurance athletes.

The Science

One of the primary benefits of Zone 2 training is an increase in mitochondrial density. Mitochondria are the powerhouses of our cells and are responsible for producing ATP, the energy currency of our bodies. By doing Zone 2 training, you are increasing the number of mitochondria in your cells, which allows for better utilisation of oxygen and improved endurance performance.

Additionally, Zone 2 training can improve your fat-burning capabilities. During exercise, your body uses both fat and carbohydrates for fuel. As you increase the intensity of your exercise, your body starts to rely more on carbohydrates and less on fat for fuel. By doing Zone 2 training, you are training your body to become more efficient at using fat for fuel, which can help you conserve your carbohydrate stores for when you need them most.

Another benefit of Zone 2 training is the improvement in your cardiovascular system. By training at a lower intensity, you are improving the efficiency of your heart and lungs, which allows for better oxygen delivery to your muscles. This can lead to improved endurance performance and a decreased risk of cardiovascular disease.


Research studies have shown significant improvements in endurance performance as a result of Zone 2 training. For example, a study published in the International Journal of Sports Physiology and Performance found that cyclists who performed Zone 2 training for six weeks saw a 7.1% increase in power output at lactate threshold, as well as a 4.5% increase in VO2max.

In another study published in the Journal of Applied Physiology, researchers found that Zone 2 training increased muscle capillarization, or the number of tiny blood vessels surrounding muscle fibres, by up to 13%.

Finally, a study published in the European Journal of Applied Physiology found that after six weeks of Zone 2 training, participants saw a 16% increase in maximal fat oxidation, or the rate at which the body can use fat for fuel.


In conclusion, Zone 2 training is an essential part of any endurance athlete’s training program. By training at a lower intensity, you are improving your mitochondrial density, fat-burning capabilities, and cardiovascular system, all of which can lead to improved endurance performance. So, if you want to take your cycling to the next level, be sure to incorporate Zone 2 training into your routine.

At AeroFin Performance, we offer personalised coaching packages tailored to your specific needs and goals. Our packages start at £80 per month and include regular communication with your coach, customised training plans, and access to our performance testing equipment. Contact us today to start your journey towards improved performance and success in your endurance sport.



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