As part of her doctoral defense, CERG researcher Guri Kaurstad held a lecture today outlining the various factors responsible for determining maximal oxygen uptake (VO2max) and aerobic fitness. She additionally compared elite athletes to sedentary healthy individuals and chronic heart failure patients to identify any differences in limitations between these populations. She concluded that the three most important determinants of aerobic fitness are VO2max, lactate threshold and work economy – however the relative importance of each of these depends on the type, intensity and duration of the activity.
Powering a body is a complex process. You need oxygen from the air, and it has to travel efficiently from the lungs to the muscles through the alveoli and bloodstream, finally ending up in the mitochondria – the cell’s powerhouses. VO2max is determined by oxygen supply and demand. Thus it matters for aerobic fitness since it sets the upper limit for oxygen utilization.
But VO2max is just once piece of the puzzle. Lactate threshold is based on the oxidative capacity of the muscles, and can increase without necessarily being accompanied by an increase in VO2max. Since the lactate threshold determines what percentage of VO2max can be maintained for prolonged periods, it too has an important influence on aerobic fitness. One might imagine two individuals with an equally high VO2max, but differing LTs – they would start out equally strong, but over time, the one with the lower LT would fall behind from being unable to sustain the same intensity.
Work economy is the third major determinant of aerobic fitness. It is a measure of the oxygen cost for a given aerobic workload – essentially how much “bang for your buck,” when it comes to the oxygen needed for a given power output. Again, if you imagine two individuals with an equally high VO2max, the one with the more efficient work economy will fare better by putting the same amount of “resources” to greater use.
Unsurprisingly, elite athletes take an interest in what limits their aerobic fitness. Once you identify the limiting step – or so the argument goes – you can figure out a way to improve it, and thereby maximize your fitness with targeted training. For untrained healthy individuals and chronic cardiovascular disease patients, the need to know the limiting step to one’s fitness may initially seem less important. However, as research ties aerobic fitness to longevity and future health outcomes, the question is becoming increasingly pertinent for everyone.
Written by Hanna Sofie Ellingsen at CERG.