By Rob Bridges

Background and what’s involved in lab testing

Following on from my previous article on ‘Lactate thresholds made simple’, this article looks into the benefits of lab testing and why as a triathlete these tests can be very useful to aid performance.

Lab testing has long been used for profiling elite athletes for performance benefits, especially in endurance sports. Many amateur athletes have taken part in studies looking into specific areas amongst performance, thus creating more knowledge in the sport science world. However, there is much to be gained from amateur athletes having a performance profile test just like an elite athlete would.

Being specific to triathlon, lab testing can very easily be done on the bike (stationary) and run (treadmill), where both follow a similar protocol of a sub max test (ramp test) and max test (VO2 max). For the sub max test athletes are tested until they reach LT2 (anaerobic threshold), a standard test would be to start at a low speed (run) or power (bike) and increase this speed/power every 3-4 minutes until LT2 is reached. A small sample of blood is taken at the end of each stage to track lactate in the blood. This usually lasts around 20-30 minutes.

For the max test athletes are tested to the limit, this test usually lasts around 8-10 minutes where the gradient (run) or power (bike) is increased every 15-30seconds until exhaustion. This is a good way to determine your max heart rate and VO2 max.

For both tests athletes wear a respiratory mask to test for Oxygen (O2) and Carbon dioxide (C02) levels.

After the test a trained physiologist will analyse the data where they are accurately able to give an overview of your physical markers which in turn will help you and your coach understand how to move forwards more accurately in your training.

What physical markers am I actually looking at?
There are many physical markers that can be looked into after a lab test. In terms of endurance performance all are very useful. I have split the different physical markers into sections below.

Thresholds
During a lab test we look out for 2 significant changes in blood lactate, these are called LT1 and LT2 (please see my previous article for more info on lactate thresholds – HERE). Once you know these 2 markers your coach can set you very specific sessions related to your physiology. Without a proper lab test you are sort of just guessing. Obviously, you have tests that you can do which estimate your LT2, such as FTP or CP (Critical Power) for the bike or a 10k run. However, these aren’t as accurate as a lab test.

To determine LT1 at home is a lot more difficult and to be honest it’s almost impossible. LT1 is argued to be sustainable for around 3 hours of activity. LT1 for a triathlete of any level or race is a key marker in triathlon performance. Even elite athletes who race Sprint and Olympic distance will look to improve their LT1 just as much as their LT2.

These markers are useful for training but they are also useful for racing as you will know (based on HR or power) what you can physiologically achieve within a race. You and your coach are then able to have a more in-depth discussion about your race plan based on physical parameters

VO2 max
VO2 max is measured in millilitres of oxygen used in one minute per kilogram of body weight (mL/kg/min) and is generally termed as your performance ceiling. You will have probably seen many elite athletes stating very high VO2 max’s, and although linked to endurance performance VO2 max it is not the be all and end all. Once you have determined your V02 max you need to look at what % of Vo2 max your LT1 and LT2 occur at. Typically, these don’t go much beyond 80% and 90% respectively. Therefore, if they are at this level you would need to aim to move your V02 max on. If they are below then you need to concentrate your efforts on improving your thresholds.

Substrate utilisation
We can calculate Substrate utilisation from gaseous exchange (how much O2 and CO2 you expend). This is basically how much fat and carbohydrates you burn during exercise. At low intensity you burn predominantly fats and the higher the intensity the higher the % of carbohydrates you will burn. As a triathlete we want to train our bodies to focus more on burning fats. For example, a 70kg athlete who has 15% body fat has over 80,000 kcals of stored fat, compared to just 2,000 kcals of carbohydrate.

From a lab test we can work out how much fat and carbs you burn at a given heart rate (or speed or power). Therefore, we can work out very accurately how many carbs you need for a long ride or how many carbs you need for a race. As stated before, training your body to use predominately fats is essential for Olympic distance races and above. There is no easy fix for this, it requires consistent low intensity training. You can speed up the process by training when fasted but this something you need to do carefully and with supervision of a coach or nutritionist.

Running economy
Running economy (RE) is usually measured in millilitres of oxygen per kg of body weight per km (ml/kg/km). Therefore, this shows the amount of energy (oxygen) that you use to run at a given submaximal speed. The lower the value, the better.
RE is often over-looked but is a very important marker of performance, especially in triathlons with a 10k run or further. Paula Radcliffe famously focused on running economy rather than V02 max, her running economy got as low as 175! Even an elite triathlete will very rarely get under 200.
There are many ways to improve economy such as: consistent mileage, running drills, running strides, flexibility and mobility work and working on running mechanics.

An example of an athletes run data and how I would develop them

40-year-old male (70kg) age grouper, good swimmer and strong biker. Looking to finish in top 10 of age group at Staffordshire 70.3. Running is the weakness and fades late into a race. Experience of 6 years of training and racing.

V02 max– A high V02 max, this gives him a high aerobic ceiling. This is not the limiting factor of his running.

Thresholds- LT1 and LT2 occur at 70 and 80% of V02 max. Typically these can’t be moved beyond 80 and 90%. Therefore, there is huge potential to develop his thresholds. Lots of tempos at LT1 and reps at LT2 or just above. Very limited running needed beyond 5km pace.

Running economy- this is quite high (remember lower is better) for an athlete with 6 years of racing and training experience. This athlete needs to focus on consistent low intensity running plus running drills, strides and mechanics. Gym work, to build strength, will help maintain his running pace late into a race.

Substrate utilisation- high percentages of CHO (carbohydrates) burnt at LT1 and LT2, and high CHO g/min. For example, if this athlete were to run off the bike at LT1 (an experienced athlete could do this) they would complete this in 1:37hrs. Therefore, they would burn 1,397kcal of CHO just in the run leg of a 70.3. They would need 13 xendurance gels (27g/ per gel) just to maintain CHO levels on the run. It is likely they would have depleted stores during the swim and bike leg. This is very high and a focus on fat oxidation is required. Consistent low intensity training will help with this. There is also a potential of training while fasted to improve fat oxidation rates.

Based on this data its simple to see why this athlete fades late into a race. Running economy and fat oxidation rates are the key areas for improvement as well as developing thresholds. Without a lab test it would be quite difficult to pinpoint his strengths and areas of improvement.

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