VO2max, the rate of oxygen uptake during maximal aerobic exercise, is widely known as a measurement of health and cardiovascular fitness. Consider it the size of the aerobic engine. VO2max is also an important value you can use to track and calculate overall fitness, fitness changes, energy efficiency, and calorie consumption.
When evaluating VO2max, values can be expressed in two ways, either in Relative or Absolute terms. Absolute VO2max measures the total amount of O2 taken in, not accounting for body weight. It is expressed in L/min or mL/min and is helpful in comparing sports where body weight (non-weight-bearing) is not taken into account or is absorbed, such as rowing. However, using absolute values is not always the best measuring stick, especially when comparing individuals of different body sizes and weight-bearing sports (running). This is the reason why we have a Relative measurement. Relative VO2max is expressed as mL/kg/min and takes into account body weight.
As Relative appears to be the more common of the two values typically discussed and is related to body weight, how can changes in Relative VO2max improve your performance? That depends on where the change is happening, what proportion is from cardiovascular system changes, and what may be from body composition changes. Additionally, the magnitude of improvements is influenced by ability level (less for elite vs. amateur).
Cardiovascular improvements that improve VO2max include things such as stroke volume, contractility, pre-load, muscle blood flow, and a host of other exercise-induced adaptations. Body weight and body composition changes are only part of the equation in improvement, but for some athletes, it can be the low-hanging fruit.
As many athletes seek healthy changes in body composition to improve sports performance, let’s do a quick example of how reducing kg may impact the value. As I mentioned, body weight will not affect absolute values. It will, though, have an impact on weight-bearing sports. For a sport such as running, a reduction in body weight may be related to lower ground force impact, higher velocity, and less calories/energy consumed.
Suppose we consider a fictional triathlete who scored a VO2max value of 45 mL/kg/min on a recent graded exercise test at a weight of 102 kg and wants to lose weight for the upcoming season. The athlete safely follows a sound diet and reduces his weight (mainly via a loss of fat mass) to 91 kg. This change increases his relative VO2max, which now goes from 45 to 50 mL/kg/min. A gain of 5 mL/kg/min – awesome, right? However, whether this increase will improve performance or the extent to which it improves performance is really more about how the body composition was changed via weight loss (1). Considering that VO2max is proportional to lean body mass (muscle) and inversely proportional to fat mass, body composition matters (2)!
What does all this mean?
An increase in VO2max is a good thing for endurance athletes to target, but how the value is created and measured matters. Losing lean muscle mass in order to reduce body weight may raise your Relative value but may not increase performance. If weight loss is part of your fitness journey, the best strategy for increasing VO2max is a loss of body fat mass while also targeting cardiovascular adaptations. Targeting both sides of the equation is a better bet for overall health and sports improvement. After all, a high VO2max may only be the by-product of the cardiovascular and body composition adaptations and not the reason for it.
I hope this explanation helps you understand VO2max measurements and how certain variables may impact the value.
Are you interested in getting your VO2max tested? See the Performance Lab page for more info, and message me to schedule!
~Coach Noel
1 – Radovanović, Snežana, et al. “The Impact of Body Weight on Aerobic Capacity.” PubMed, vol. 11, no. 1, Feb. 2014, pp. 204–09. pubmed.ncbi.nlm.nih.gov/24496365.
2 -Mondal, Himel, and Shailendra Kumar Mishra. “Effect of BMI, Body Fat Percentage and Fat Free Mass on Maximal Oxygen Consumption in Healthy Young Adults.” Journal of Clinical and Diagnostic Research, Jan. 2017, https://doi.org/10.7860/jcdr/2017/25465.10039.