Endurance training has significant benefits. It:

- Improves mitochondrial function (starting at about 20 minutes).
    - Allows your muscles' ability to use fatty acids as fuel (you use up intramuscular triglycerides and start pulling from adipocytes—somatic fat cells—after 30 to 45 minutes).
    - Raises the level of energy output before switching to lactate.
    - Protects against metabolic dysfunction.
- Increases aerobic capacity.

The most effective way to train for improved endurance is
long bouts of easy, steady-state exercise. For the best
results, you must:

- Stay _below_ your lactate threshold i.e. zone 2 training.[^1]
- Spend _at least_ 20 minutes at a time in zone 2.
- Accrue 3 or more hours a week of total training time.

[^1]: Different models of activity have varying numbers of zones and different criteria that define them. Here, what we're looking for is that your working hard enough that you can feel the exertion but you can still carry on a normal conversation while doing it.