Time Domain Variance

You may wonder why we lift weights, do short sprints around 2min, and many workouts that range from 5 to 20+ minutes.  Why the different time domains?

Well, there are three metabolic energy pathways called phosphagen system, glycolysis and aerobic system.
These are the 3 ways the body produces and used energy.  To improve in all 3 areas, we need to work and train in all 3.

1. Phosphagen System

This is the short-term, high power output, that is anaerobic (not requiring oxygen), and only lasts a very short time, up to 10-30 seconds.  This system does not burn fat or carbs, but uses an energy source found in the muscles.  This energy source is limited, so it only last a short time.  We would see this in a 100m sprint or heavy lifting.

2. Glycolysis

Glycolysis is the predominant energy system used for all-out exercise lasting from 30 seconds to about 2 minutes.  It uses sugars stored in the blood or muscle (more readily available) along with oxygen.  As long as there is oxygen available, the energy is processed and the muscle works.  When the oxygen supply runs out, the muscle stops working at the same capacity that it did originally.

3. Aerobic System

This system uses oxygen and burns both sugars and fats.  Since this system takes longer to produce energy, it doesn’t normally kick in until after a couple minutes of work.  While the sugars will burn much quicker and produce a lot more energy that the other two systems, the fats produce even more energy than the sugars.  That is why it’s said you have to work for a certain amount of time before getting into your “fat burning” zone.

These 3 ways the body produces energy are important to understand.  We train to improve our body’s efficiency to produce oxygen for both medium and long workouts.  The short sprints or weight lifting normally increase the size of our muscles which would, in effect, increase the amount of high-output energy available.  We also need to understand these systems so that we can fuel our bodies properly.  That is why complex carbohydrates like grains and vegetables and healthy fats are so important to give us longer lasting energy.

Hope this helps.