Ever wondered why some training programmes work for some athletes and not for others? Why some people are genetically gifted athletes? Why there is a fixed set of intervals for all athletes? Why certain drugs work for some and not others? Do compression socks work? What the hell does a VO2 max test tell you, is it just useless information? Is lactate friend or foe? I delve into the sport science world and try to find the answers to train smarter and hopefully become a better athlete. This page is written in my own thoughts and words with a cross-pollination from several other sites and links to the original articles. Some of it might sound like a rant but it is written to make you think. So if you read it without a open mind then your in the wrong place. Enjoy and open your mind.

Wednesday, March 2, 2011

How valid is a VO2 test and results?

VO2 max: is the value of the total amount of oxygen used by the body at maximal intensity. It is the oxygen used by the muscle, heart, respiratory system and the brain. The maximum amount of oxygen that the body can use is expressed as a VO2 value.

Traditionally VO2 is used as an assessment for training intensities of which percentage of VO2 Max is most commonly used. Which is based on the VO2 Max and give a performance ability to compare against other athletes.

There are two ways in which we can view VO2 max.
  • The typical traditional view: VO2 is the limiting factor to human performance, to improve VO2 max we need to train at or near VO2 max. 
  • The alternative view: The weakness of either the cardiac system, the respiratory system or the muscular system will limit the VO2 performance. Finding the weakest link and training the weakest system will improve the efficiency of VO2. 
If we then view VO2 max from the alternative view, then to have the highest VO2, if simplified we require the respiratory system to collect oxygen and transfer it to the blood stream, extract the CO2 from the blood and transport it back to the outside world. The body requires a efficient cardiac system to pump the oxygen and CO2 around the body to and away from the muscle, and finally the muscles require mitochondria which loves oxygen for energy.

Sport where more muscle is involved will have a higher VO2, e.g. cross country skiing versus cycling, as there is a greater requirement for blood getting delivered around the body etc. Assuming technique does not hinder performance (as the extra muscle required to compensate for balance and coordination in technique require more energy) then the harder you go, the greater the requirement for oxygen and VO2 will go up. The faster you go the more you will push one of the limitations in your body which will limit you from reaching a higher VO2 performance.

A higher VO2 means your body requires more oxygen, but is a higher VO2 value always a good thing? Retesting for VO2 max where your VO2 has decreased for the same speed or wattage is often looked at negatively, rather it should be seen as a good thing as the lower VO2 at the same LBP is now more efficient so in theory you should be able to push longer with a more efficient system.

Some problems with VO2 tests:

There are various protocols developed to test VO2 max and each will give a different VO2 value for the same athlete. The problem is that if a VO2 test was truly physiological then you should get the same VO2 value every time for that sport. Some individuals during supra maximal test reached higher VO2 max result than during a standard incremental one (Hawkins et al).

With the VO2 test you are really only getting feed back on the respiratory system and the amount of oxygen that the body can use, and one variable of the cardiac system, i.e. heart rate. The entire test is based on VO2 and at what heart rate this occurs, in some VO2 test (that has been done on me) lactate was not even taken so you do not even have the metabolic feed back. The main problem with only having heart rate for the cardiac system is you have one variable and only know how fast the heart is beating, there is absolutely no information on stroke volume or cardiac output! Yes we could use formulas to calculate Cardiac output (VO2 Max= CO x (a-v) O2 difference), but most VO2 tests last 6 to 12 min and with such a short test time the intensity steps may be to big, too quick and in this case we could miss physiological markers. FeO2, CO2, Lactate, SpO2 etc all have a lag time of about 30 seconds, which means we will miss certain bio markers! Using a device like a physioflow which is non invasive gives you live feed back on hemodynamics and gives a fuller picture of the whole body’s reaction. With live hemodynamics we have information on Left Ventricle function,, Ventricular Ejection time, Stroke volume etc.

More practical and useful information can be gained from a VO2 test by looking at changing body position, RPM, stride length, breathing patterns to see if this changes the O2 and CO2 relationship. How many athletes know their breathing rate at LBP or even race pace? Or their breathing Tidal Volume? Why is this important? This information can be used to plan breathing training with a SpiroTiger to improve core stability, breathing coordination, diaphragm strength, and if you want to explore breathing training further even gas exchange.

A VO2 max test looks for a plateau to find the VO2 max value, Tim Noakes, 2008, demonstrated that in most test this plateau does not occur. Knowing when a test will end, i.e., the length of the test also will effect the outcome value (Baden et al). The first time I do a new fitness test is always the hardest, (e.g. a 60 second jumps test measuring sustained power) because I don’t know what to expect, in a follow up test I know how to pace so I have changed the results with out likely actually really improving). Lactate threshold can be completely missed, probably overestimated during a VO2 max (even standard Lactate test the so called anaerobic point is over estimated in most cases). Athletes training at the same percentage of VO2 max with similar VO2 max values can have huge variants in training outcomes (Scharhag-Rosenberger et al). The entire VO2max protocol needs to be reviewed.

Once again with a training program where training zones are based on VO2 max percentages, we do not have a clue what we are training. What is the cardiac system doing? what system in the body are we stressing? At what point is the Left Ventricle function being challenged which will affect stroke volume? With out looking at the body as a whole we do not have a clue. Rethinking the VO2 protocol to follow physiological reactions would be one step in the right direction. A Lactate Balance Point or Zone test (LBP developed by FaCT) with lactate for metabolic changes combined with VO2 for pulmonary information and cardiac feed back on hemodynamics gives more information than a VO2 max test EVER will. Unfortunately our coaches and physiologist are traditionalist and follow what they were taught in University and these ideas will take time to be accepted until they look at how we can train the body as a whole and instead of training speed, power, endurance rather think train muscle, cardiac, respiratory and how these system react during speed, power, endurance and when they fatigue so that we understand how much overreaching is required.

The LBP idea and testing using respiratory and hemodynmic devices is part of FaCT's continued research. FaCT Canada is actively engaged in researching and continuously testing more reliable ways of assessing the body, currently they are looking how CO2 can be used as a biomarker by using a capnometer. To read more in depth discussions go to their site at FaCT. There is a in depth article on The Fallacy of Vo2max and %VO2max on the site Science of Running.

Drifting slightly off the VO2 subject, this is simply me thinking loud. We often wonder why we get different outcomes with research studies on training ideas and altitude training (or even VO2 training zones) etc where we have responders and non responders to the training load. If research really wanted to have a controlled group, they could simply do a full assessment where they find which people in a control group have what limitation. And when at the end of a study they have there responders and non responders they will more likely have a clearer picture of why certain subjects responded in certain ways because they were limited by there cardiac system or ability for muscle to utilize the fuel given to it etc. At least this is how I would do a controlled physiological study.