The next cycle of Stronger, Leaner & Healthier You trainings program:

It is time to get focused on what next week will bring to you. Our next cycle is building on the gains you have made in the previous months and you are going to put strength at work gearing up for the CrossFit Open. We are going to make an concerted effort to develop the aerobic system with a bias on power endurance

If you want to read up on Stronger, Leaner & Healthier You program click here

A post with all details of next batch of wods will be published on Monday, below explains why we do the things we do at ChalkBox.


To answer that question we need to understand the role it plays. The aerobic system is the energy pathway used by our bodies to produce energy (ATP) in the presence of oxygen (hence, aerobic) and it is responsible for long term energy production. To create ATP this system utilises both sugars AND fats and because of this the aerobic system has a huge capacity to generate energy. The downside being that this huge energy generating capacity comes at the expense of power and it cannot create energy as fast as the anaerobic systems, this is because the aerobic system needs oxygen (the anaerobic do not) and there are many more chemical steps that take place in aerobic energy production.

What can we develop?

As the aerobic system relies on the presence of oxygen, it is therefore limited by oxygen supply and oxygen utilisation. You can think of oxygen supply as the ability of the cardiovascular system (heart, lungs, vascular network) to supply oxygen to muscles and cells. Whilst oxygen utilisation refers to the ability of the muscles and cells to actually use the oxygen efficiently. When the rate of oxygen demand exceeds it's supply/utilisation, we turn to the anaerobic systems for energy, and if we operate anaerobically for too long we fatigue and have to slow down.

By developing the areas of oxygen supply and utilisation we can develop our aerobic system.


The true power of the Aerobic System

When we discussed strength as base of your fitness pyramid we purposefully left out the aerobic system. We already spend a lot of time developing this area but were in a strength biased cycle.

The aerobic system forms the base of the energy systems pyramid, without a strong base we cannot support the layers on top. This means that if we have a poorly developed aerobic system then the anaerobic systems will not be able to function optimally.

During anaerobic periods of work we produce metabolic by-products, the faster these by-products accumulate the quicker you fatigue and experience the crash. Once this happens your body relies on the aerobic system to clear out these by-products and re-stock the mechanisms of anaerobic metabolism, basically your ability to recover! This 'recovery' refers to intra workout recovery (mid wod), recovery between sets or recovery between training sessions. 

This essentially means that without a strong aerobic system our anaerobic systems are also limited."...the faster your aerobic system can produce energy the less we have to rely on the anaerobic systems and the better conditioning you have. Not only that, but more aerobic power means that the anaerobic systems can re-charge much faster so they can contribute more power when you need them."

"But CrossFit is anaerobic right?"


Whilst we have three main energy generating systems that are required for different intensities of work, it is never a case of a single energy pathway being active and the others dormant, they work synergistically, all operating at the same time. 

  • During an all out max effort period of work, crossover to aerobic dominance occurs after approximately 20-30 seconds.

  • During sub maximal (but intense) effort: Crossover to aerobic dominance occurs after approximately 60-75 seconds.

So unless you have a very short, super intense period of work, you are primarily using your aerobic energy system to generate energy. So the vast majority of workouts that we do, or the majority of sports you play, are powered by the aerobic system. 

To perform well in CrossFit, 5km races, triathlons, tough mudders and so on we need a strong aerobic system with the ability to buffer anaerobic energy production when workouts require you to push onto into the anaerobic pathways.

"So, seriously, are we doing long, slow distance?!"


Developing our aerobic systems is more complex than just doing long, slow distance. As well as developing the aerobic system we will also keep developing your overall strength.