You may have heard of the “exercise intensity domains” known as Moderate, Heavy, Severe, and Extreme. These intensity domains are distinguished from each other by different physiological responses to continuous effort.
The term physiological threshold refers to the boundaries or transitions between these different intensity domains. Training and the environment (both internal and external) shape and influence their evolution, so they are not fixed.
We can use the 4 states of matter as an analogy. Below 0 degrees Celsius, water is in a solid state. Between zero and 100 degrees, it’s a liquid. And so on.
Depending on how hard you work during your effort (cycling, running, swimming, etc.), you will find yourself in different areas, and your physiological response will be different.
We could say that during moderate effort (like Zone 2, also known as low intentity training), the balance is at the cellular/muscular level. In other words, the muscles involved in the effort can take on the entire workload..
In the high range, the muscle recruited can no longer take on the load while maintaining a stable state. As a result, blood lactate levels rise and the slow component of VO2 becomes apparent. The entire organism is now responsible for maintaining this internal equilibrium.
In severe conditions, everything goes wrong. You can no longer increase your oxygen intake (while demand continues to grow until VO2max is reached), you lose your homeostasis (internal balance) and rapidly tend towards failure.
In the extreme range, the effort is so intense (usually <2 minutes) that your VO2max doesn’t even have time to kick in.
Here are some examples of sessions for each area, with the associated RPEs (difficulty).
The most important thing to understand is that these different efforts do not have the same cost for your body! Whether at metabolic, nervous or tissue level, each intensity has an associated LOAD that you need to consider.
If your training load exceeds your recovery capacity, you’re in trouble! So make sure you balance your training according to your needs and abilities.
Did you enjoy this post? Please share it with at least one friend who can benefit from it! And leave me a comment if you’d like to see more posts like this in the future 
The post What are Exercise Intensity Domains? appeared first on Upside Strength.