Picture the scenario, it’s January and the gym is packed with people who have just signed up after making new year's resolutions. All the equipment is occupied by sweaty people gasping for breath as they work themselves into the ground.

Come March, the gym will be relatively empty because the new members couldn't stick with it. Often, they were exercising much harder than needed— at an intensity or training zone that requires significant recovery and adequate nutrition. Athletes rarely touch this level of intensity and even then, have teams of specialists and doctors managing their training. They’ll be typically doing 30% of their volume at a high intensity. No wonder the newbies couldn't make it to March.

Athletes and their teams understand training zones.

In part 2, we’ll be looking at training zones and how:

• A training zone corresponds to an underlying physiological environment.
• Training zones stimulate different muscle fiber types that have unique fuel metabolism.
• Programming training by zones can lead to long term muscle and metabolism adaptations in the body.
• Long term adaptations are essential to human longevity and health-span. This is important, as improvements in overall fitness or VO₂ max bring about huge reductions in all-cause mortality, as discussed earlier.

Understanding training zones and their importance to health

An important concept to grasp: the ability of a person determines how the intensity of exercise will affect that person.

For example, a relatively fit person exercising at a moderate intensity would be hard for an unfit person and then easy for a Tour de France rider.

These three people would all be in different training ‘zones’ but all could be producing the same output i.e. watts or speed.

This is shown in the figure below, where the graphs show lactate and fat oxidation levels for a professional cyclist, an active person and one with type 2 diabetes, as a function of power output.

When blood lactate exceeds 2 on the graphs, that individual is making the transition from zone 2 to zone 3, from utilising fat as a fuel to utilising glucose. As we can see this happens at under 150 watts for a diabetic and over 300 watts for a professional cyclist; meaning they are cycling at double the speed of the diabetic before they switch to zone 3.

An unfit person can be in anaerobic metabolism while a fit person is in aerobic metabolism at the same power output. Each training zone produces a different physiological environment and therefore places different levels of stress on a person's metabolism and organs (including muscles)