In exercise physiology there are 3 main exercise domains marked by specific physiological changes. The three domains are called the moderate, heavy and severe domains and we break these domains into 4 training zones which we use for our daily training programs.
Zone 1 #
Zones 1 is in your moderate domain.
The benefits of training in the moderate domain are:
- Building higher mitochondrial density in muscle
- Greater capillary network
- Improved beta oxidation (fat burning)
- Improved mental toughness
- Increases endurance and VO₂.
A major benefit of volume training is increased mitochondrial density. This increase enables the body to utilize more oxygen and contributes to an increased VO₂ and by extension endurance performance.
Training in the moderate domain also burns a higher proportion of fat compared to higher intensity levels. Our bodies are always using sugar as an energy source, but in the moderate domain our body will convert fat molecules to glucose to fuel our energy needs. High volume training in the moderate domain improves beta oxidation efficiency and improves your body’s capacity to use energy efficiently and effectively.
Zone 2 #
Zone 2 is at the low end of the heavy domain.
The heavy domain is a very wide physiological range that extends from the top end of zone 1 to the low end of zone 4.
In volume training we try to avoid exercising in zone 2 because you will mostly accumulate fatigue without any additional training benefit of the higher intensity level. In zone 2, you don’t achieve greater physiological benefits associated with zone 1 and you aren’t exercising at a high enough intensity to gain any benefits associated with zone 3. Therefore, easy training should be kept in a zone 1 heart rate range to minimize the fatigue and improve post-exercise recovery.
Zone 3 #
Zone 3 is part of what is called the heavy domain. It is a physiological range where increases in heart rate and intensity levels result in linear increases in lactic acid production, but lactic acid will remain stable if intensity level is held constant. This means you can exercise at a reasonably high intensity level, produce lactic acid, and maintain that level of exertion for extended periods of time (≈1hr+).
There are several benefits to zone 3 training in the heavy domain, which include:
- Increased VO₂
- Increase maximal lactate steady state
- Increased lactic acid tolerance
- Improved endurance
- Improved mental fortitude
The main purpose for training in this zone is to push through lactic acid build up for extended periods of time which will improve lactic acid tolerance and can increase the top level of your zone 3 threshold.
Zone 4 #
Zone 4 is your severe domain. It is a domain that begins when lactic acid production at a constant intensity level becomes unstable and ends at maximal effort intensity. It represents a physiological state where the body cannot clear lactic acid production as quickly as it’s produced, resulting in very high fatigue.
Depending on the intensity level, individuals can exercise in zone 4 for as little as 30 seconds to as long as ≈45min.
Zone 4 training will produce the largest increases in VO₂ Max compared to zone 1, 2, and 3, but will also produce the greatest amount of fatigue.
When training in this zone it is very important to undertake proper warm-up, cooldown and recovery protocols to minimize muscle damage and maximize exercise benefits.
