You may have heard many elite athletes undertaking a VO2max and lactate threshold tests.. but what exactly are they?
They are performance tests you under take on the treadmill. They usually consist of 2 sections:
Repeated 3 minute efforts of increasing speed taking breath samples and blood samples at the end of each one.
One all out effort - the treadmill increases in speed or gradient each minute until you can no longer keep up, and then breath and blood samples are taken.
VO2max Testing
VO2 stands for volume of Oxygen. VO2max is the measure of the maximum amount of oxygen a person can use. This is not to be confused with the maximum amount of air a person can breath in, which is called total lung capacity, the average in a human being 6L.
Total amount of air breathed in = Total Lung Capacity
Total amount of oxygen used by the body = VO2max
Oxygen is used in addition to food (glucose) by your muscles and organs to create energy during exercise, therefore the more oxygen your body can use, the harder it can work and the faster it can run. Oxygen comversion to energy can be illustrated by this simple equation:
Glucose + Oxygen → Carbon dioxide + Water + Energy (as ATP)
VO2max is calculated in an 'absolute' unit and converted to be relative to your body weight (kg) so people can be compared. It is then expressed per minute, resulting in the unit mlO2∙kg-1∙min-1 (ml of oxygen per kg of body weight per minute).
My absolute value recorded in my recent test was 4.59 L/min. This means my body was
able to extract 4.59 L of Oxygen from the air, every minute. To convert this to VO2max and equat for my bodyweight my peak V̇O2max is 69 ml O2∙kg-1∙min-1 (the dot above the V means per minute).
There is a linear relationship between exercise intensity and oxygen uptake until the cardiovascular system can no longer meet the demands of the muscles. This means that V̇O2max can be use as a predictor of endurance performance and aerobic fitness in elite athletes (albeit not a very good one, but we will get onto the later), but also a good predictor of an aging persons ability to complete everyday tasks which can be vital for an older person to maintain their ability to complete basic but necessary tasks such as getting up and down the stairs the later they get in life.
The graph below shows the range in VO2max for males from 25-75 years of age.
V̇O2max isn't a good predictor of running performance as it only measures how much oxygen your body can use, not how efficient the body is at using that oxygen. For example, one runner may have a V̇O2max of 70 (good oxygen uptake) but a 5km time of 20 minutes (poor oxygen utility) while another runner may have a V̇O2max of 60 (lower oxygen uptake) but a 5km time of 15 minutes (good oxygen utility). This is why measuring blood lactate levels have greater accuracy for predicting performance than V̇O2max.
Lactate Threshold Testing
If lactate levels are raising in your blood as you exercise then you will not be able to sustain that speed for very long. This is because you are working anaerobically (without oxygen) which means your are working too hard and require too much energy (ATP) for aerobic (with oxygen) energy production. The muscles are not able to produce ATP quick enough through the pathways that use oxygen, therefore they start using the pathways that dont use oxygen. Using these pathways results in the by product called lactic acid being produced along side hydrogen ions which turn your blood acidic (lower pH). The acidic blood and muscles reduces the efficiency of your cells to produce more energy and thus causing fatigue.
So, how do we measure lactic acid production? ..By finding your Lactate Threshold (LT), Lactate Turn Point (LTP), and Peak Lactate.
To measure these, you run on the treadmill at a certain speed. After 3 minutes your blood lactate is recorded by a small pinprick on the finger or ear. You will then run slightly quicker on the treadmill for another 3 minutes and the lactate will be recorded again. These increments in speed will continue until you reach your LTP.
Lactate threshold (LT):
The first small sharp increase in lactate is defined as the lactate threshold (LT). This is the point where you will start to produce more lactic acid as your body moves from using almost all aerobic energy pathways to then needing to introduce some anaerobic energy pathways. You can tolerate this moderate intensity well, sustaining that speed for for a long time. The LT will be close to your predicted marathon pace.
From my results we can see a clear increase in La levels (~2-3 mmol.L-1) indicated by the green arrow. Therefore, my LT (green arrow) is ~17 km/hr or ~10.5 mph (approx. 144 beats per min and 75% of my V̇O2max).
Lactate turn-point (LTP):
Lactate turn-point is defined as the intensity where a second, steeper increase in
lactate is observed increasing to above 4mmol. With increasing exercise intensity
your body's ability to clear and reuse lactate can't keep up with the rate at which
lactate is being produced and ultimately it then starts to accumulate in a non-linear
fashion. My lactate turn-point (red arrow) was 18.5 km/hr or 11.5
mph (approx. 154 beats per min and 85% of my V̇O2max). The LTP can be sustained for 30-60mins, and therefore, should be close to your predicted 10km pace.
Peak Lactate:
This is the highest amount of lactate in your blood during exercises i.e your blood lactate once you hit maximum effort. The higher you can get this measure before reaching fatigue the better your body is at functioning with very acidic blood levels, and thus the longer you can sustain a pace. This is recorded by measuring your blood lactate at the very end of the maximal test (VO2max test). Mine was 13.71 mmol.L-1, however it was recorded 5-10 mins after the test so it could be slightly higher than this.
However, this means that the paces you hit during LT and LTP are not 100% accurate to the as some athletes can tolerate increased lactate levels and keep maintaining the high intensity for longer. It has been shown that elite runners can perform an entire 10km race at velocities significantly greater that their LTP compared to sub elite athletes because they are able to run at higher levels of lactate and larger fractions of their V̇ O2max without fatiguing.
To make LT and LTP useful to us, it is used alongside HR. We match these together like on the graph above. Therefore, if I want to train at my LT I would wear my HR monitor and keep my HR somewhere around 144bpm. I could choose to use the speed I was running at on the treadmill (17 km/hr) but running outside isn't equivalent to running on a treadmill due to external variables like hills and wind, and I could easily creep into the LTP trying to run 17km/hr up a long hill into a head wind!
With all this information you can get your most accurate training zones (more accurate than ones given to you from your training watches). These can be a useful guide for planning your sessions.
The key with performance testing is to test again after a period of training to see if your scores have increased confirming you are getting quicker and your training plan is effective. If you re-test and there isn't much change (or you are worse!) you will need to rethink your training plan to push these numbers up. Note these numbers are unlikely to change significantly if you are already an experiences high level athlete so you may be looking for small tweaks that can give you a small percentage increase.
I hope that clarifies the performance tests and shows the value they can add to your training.
I will be retesting again in April, so I hope to see some improvements in my scores!
James McMurray
Sport and Exercise Health Science BSc
Physiotherapy BSc
References:
My Testing report by Victoria Tidmas, v.tidmas@herts.ac.uk
Delgado BJ, Bajaj T. Physiology, Lung Capacity. [Updated 2023 Jul 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK541029/
Lima-Silva, A. E., Bertuzzi, R. C., Pires, F. O., Barros, R. V., Gagliardi, J. F.,
Hammond, J., ... & Bishop, D. J. (2010). Effect of performance level on pacing
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Schrack JA, Simonsick EM, Ferrucci L. The energetic pathway to mobility loss: an emerging new framework for longitudinal studies on aging. J Am Geriatr Soc. 2010 Oct;58 Suppl 2(Suppl 2):S329-36. doi: 10.1111/j.1532-5415.2010.02913.x. PMID: 21029063; PMCID: PMC3057770.
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