Hi there, please excuse the geek in me coming out in this one but your body really is amazing and the way it works it truly fascinating.
There are 3 energy systems that allow us to exercise. The first 2 are known as anaerobic systems and operate in the early phases of high-intensity exercise from the body's own stores of energy within the muscle. The 3rd system is known as the aerobic system and operates via a pathway involving oxygen, this means the intensity of the exercise must reduce in order to allow oxygen to the muscle requiring us to breath as we exercise.
There are 2 key points in the measurement of the energy systems use, the first lactate or ventilatory threshold and the second lactate or ventilatory threshold. What we see at these points is the change in intensity of exercise producing a greater amount of lactate, what we perceive as the 'lactic acid burn' and the second is the point at which too much waste product has accumulated in the blood and the intensity of exercise has to reduce.
Interestingly these thresholds can be measured in a lab via blood sample but also by measuring the percentage of oxygen expelled when compared to carbon dioxide. For us mere mortals who operate outside the lab, the first ventilatory threshold can be easily understood by the talk test. The point at which you can no longer hold a conversation easily. The second threshold is simply the point where you can't keep going at that pace/rate/intensity. The burpees, squat jumps, double unders all need to slow down, that's the second point. As coaches, we will play around with how much time we spend in each of these spaces, with the ultimate goal of improvement NOT bullying I promise!
All in all, there are 5-6 zones typically referred to in and around these thresholds all expressed as percentages of max heart rate without the need for a lab. Just so you know the next time you look at your screenshot after that run with your percentage of the run expressed across the different zones, there is a fair bit of science going into that screenshot. The other important piece to note here is that there isn't always a need to operate at the highest intensity ie. run, row, ride the fastest you can every time, in fact, most well-researched plans will be consistent with an 80% volume at low intensity and a 20% volume of work at high intensity. So please if you are starting out, just remember 80% slow at a rate you can still talk and 20% at a rate you can't and we should be somewhere on our way to improvement.
Who would have thought energy and exercise could be so interesting :) right??
Yours in health
Sean Cornish
