Aerobic and Anaerobic- What You Need to Know
Aerobic and anaerobic are two words that many in the endurance coaching world including myself bound around on a daily basis, yet for the aspiring triathlete these can cause confusion at first. The terms refer to how the body generates energy, imagine a six year old at sports day, belting across the school field towards the finishing line. When they finish their run they will likely be breathing heavily, exhausted from the 25M sprint they have just completed. When they move into secondary school and start running the 1500 on the track and cross country they soon realise something, if they want to run longer distances they have to slow down. Once they run longer distances at a lower intensities they are not nearly as out of breath at the end of the effort. They may be exhausted and collapse in a heap with sore legs and no energy left, but their lungs will not burn in the same way as before, they will not be recovering from what is known as an oxygen debt. The reason you experience an oxygen debt after short efforts is due to the body relying primarily on its anaerobic system heavily for short, hard efforts, this is where your body creates energy without oxygen. I won’t go into the science of how it works here, but what you need to know is that the anaerobic system can only function for around 2 minutes before the athlete accumulates a large oxygen debt and has to slow dramatically, this is our fight or flight reaction that allows us to escape from danger. Many predators in the animal kingdom rely on their anaerobic system heavily as they sprint after prey, if the gazelle manages to slip from the cheetahs grasp or zig zag enough to tire the cheetah, it can avoid becoming lunch as the cheetah has created an enormous oxygen debt it must recover from, akin to the six year old who has sprinted full pelt over a short distance and has nothing left at the end. On the other side of the equation we have aerobic fitness, this is energy created using oxygen. This is much more efficient and is one of the leading reasons for our dominance as a species, where our prey relied predominantly on their anaerobic system to escape danger, we were able to keep them in sight and slowly run them into exhaustion as they were unable to hold the pace that we were over longer distances. As triathletes we are focused almost entirely upon the aerobic system, as it is very rare that we will be putting the hammer down and become predominantly anaerobic when racing even a sprint distance triathlon as we will need time to recover from this effort. The exception to this is in draft legal triathlon where you may launch an attack off the front of the pack to try to bridge to the next group, which upon joining you will be able to sit in the wheels of for a minute or so while your body recovers from the oxygen debt. This is the reason that so much triathlon training is done at an “all day” pace, to ensure we are building and strengthening our aerobic system and not our anaerobic system. The mistake that many athletes make is doing all of their training way too fast and making very little headway on the aerobic development side of things. You may be able to run a very quick 5K, but that doesn’t necessarily translate into a great marathon experience, I can vouch for that one personally! This is where things get confusing, I am a fairly gifted anaerobic athlete, I can push myself harder and go deeper than many others over shorter periods, but tend to suffer over especially long efforts. Normally when I mention that I have a strong anaerobic system and that 5K is my best distance to an athlete a metaphorical finger is waved in my face. “Aha! But a 5K is over 2 minutes, so it’s not an anaerobic effort”. This is of course true, but what people don’t always realise is that your body is never generating energy on a 100% aerobic or anaerobic basis. If that were the case a 100M sprinter could run with his mouth gaffer taped shut and still hit the same time as his rivals. Anaerobic energy is created in addition to the energy that is being generated aerobically, you are using anaerobically generated energy while reading this. It is only an incredibly tiny fraction of the energy being created (think several decimal places), but is it ticking over like a pilot light, ready to leap into action at a moment’s notice. To illustrate this more clearly here is a graph created using WKO4 (more information here) that visualises the energy systems used by an athlete at different timeframes. The data is collated using the athlete’s best performances at the time periods listed on the X axis, with the maximum power than can sustain for that period on the Y axis. I use these graphs to help athletes gain a better understanding of their individual physiologies to help us understand where we need to focus our training effort. Today we want to focus on the green and the blue lines, the green line represents aerobic contribution, the blue line anaerobic. If we start to the left of the chart we can see that at 1 second there is very little contribution from the aerobic system as the body has not started increasing the rate at which it pumps oxygen to the muscles yet, but using glycosides the body can create energy within the muscles and get us moving immediately. As we look closer towards the 10 second mark the aerobic system is really starting to get up to speed now, additional oxygen has been absorbed from the lungs and is being pumped to the muscles to get them fired up. For this athlete, it is
