The Almighty VO2max: Part 1

This physiological parameter, more than any other it seems, gets the most attention in endurance sports. It is certainly important, but it is only a piece of the puzzle which will be explained in future posts. It is one of the three primary predictors of endurance performance. The other are two are your percent of VO2max at lactate threshold (think of this as the fastest pace you can maintain for 1-2 hours without blowing up) and efficiency or economy (related to your “form”, but this is so much more than that!, as this is based on how much energy it takes for you to exercise).

What is VO2max?

VO2max is the abbreviation for “maximal oxygen consumption” and is reported in liters of oxygen per minute (l/min) or milliliters of oxygen per minute per kilogram (ml/min/kg or ml/kg/min) which is normalized (or standardized) based on body mass (weight). This value represents the greatest amount of oxygen your body can use (during cellular respiration) to synthesize energy (adenosine triphosphate, ATP) from food to generate muscle force and thus exercise. I skipped over a lot of steps, but that’s OK.

VO2max is important because it sets the upper limit of how much energy (ATP) you can synthesize from oxygen and food to exercise. Energy is key! The more energy (ATP) you can provide, the more force you can generate, the faster you can go. An analogy here is a vehicle. The engine uses gasoline (food) and oxygen to produce torque (force) to spin the wheels (exercise). An engine with a lot of horse power is bigger with more pistons (think a V8 or V12 engine compared to a V4 or V6 engine), usually has larger pistons, and also a bigger air intake. This engine is able to consume a lot of gasoline (food) and a lot of oxygen to produce a lot of horse power. The greater the horse power, usually the higher the maximal speed. If you limit the gasoline or air intake, the maximal horse power goes down and so does maximal speed. Just like our bodies, there are more factors involved related to performance (weight, aerodynamics, heat, etc.). But hopefully that analogy gets the point across. The higher the VO2max, the more energy you are able to synthesize from oxygen and food, the more force you can produce, and the faster you can go.

What are some VO2max values?

Here is a table from Powers & Howley, 2012 showing differences in VO2max between men and women and at different ages with values rounded to the nearest whole in ml/kg/min.

Did you notice how VO2max declines with age? This is partially due to a decline in maximal heart rate, which I will post on in the future.

Did you notice that men have higher VO2max values than women? This is because men typically have a less body fat and greater muscle mass (more muscle means more oxygen can be consumed to produce force), larger hearts (pump more oxygen rich blood to the muscles), and a higher haemoglobin concentration (able to carry more oxygen in the blood).

Endurance training increases VO2max and thus runners, cyclists, and cross-country skiers usually have higher values. World-class endurance athletes typically have values greater than 70 ml/kg/min, with some males reaching values greater than 90 ml/kg/min!

Why Should I care?

Here is a figure to depict why having a VO2max is important to endurance sports.

*Endurance training may improve efficiency, which we are ignoring for this example.

*Endurance training may improve efficiency, which we are ignoring for this example.

You can see here that the healthy, active person has a VO2max of 50 ml/kg/min and when exercising at this value is at 100% of their VO2max. This active person will only be able to exercise at this intensity for a few minutes. But when the elite person is exercising at 50 ml/kg/min, this is only 62% of their VO2max and would likely be considered a moderate effort for this person. In fact they would race closer to 85% of their VO2max which would be 59.5 ml/kg/min. So the speed the elite person could race at for at least an hour, the active person couldn’t even hold this speed for more than a few minutes!

 Are VO2max intervals the same as “anaerobic” intervals?

This gets complicated and tricky since coaching terminology is not always the same. But read on so you understand how these relate. VO2max intervals require an intensity and duration for you to reach VO2max. Usually they are between 3-6 minutes long with a rest break that is equal to or longer than the interval itself. These are hard!

Anaerobic means “without oxygen.” Think about this for just a bit and what you just read above. … VO2max intervals are actually mostly aerobic! When exercising at your VO2max, you are maxing out your aerobic system, meaning you are generating close to the maximum amount of energy (ATP) possible from food (almost entirely glucose at this intensity) to produce force to exercise. Can I keep going? Yes, but not for long. Can I go faster? Probably, but not for long. How? Because you use “stored” energy (ATP) that does not require oxygen at that given moment. In other words, you are relying on non-oxidative metabolism. (Note: This stored energy was originally generated using oxygen though.) But there is a limited capacity. It’s like using a nitro in a race car game. You are already at top speed but need to go faster. Nitro! Boom! Speed!…. But wait? I only have two more nitros! … So why is this type of interval exercise sometimes called “anaerobic”? When exercising at VO2max you are supplementing energy regeneration through non-oxidative pathways and this is why it is can be referred to as “anaerobic.” By performing this type of exercise, you are working on increasing or maintaining VO2max, as well as increasing or maintaining your body’s ability to supplement ATP using non-oxidative energy pathways. So bigger engine, and more nitros!

Contact me if you have any questions or want to know more!

Read Part 2 here!

 

References and further scientific reading

  • Bassett DR, Howley ET. Maximal oxygen uptake: “classical” versus “contemporary” viewpoints. Med Sci Sport Exerc. 1997;29(5):591-603.
  • Joyner MJ, Coyle EF. Endurance exercise performance: the physiology of champions. J Physiol. 2008;586(1):35-44. 
  • Levine BD. VO2max: what do we know, and what do we still need to know? J Physiol. 2008;586(1):25-34. 
  • Poole DC, Jones AM. Oxygen uptake kinetics. Compr Physiol. 2012;2:933-996.
  • Powers SK, Howley ET. Exercise Physiology: Theory and Applications to Fitness and Performance, 8th Edition. 2012; McGraw Hill: New York, NY.