Physiological Testing and Training Terminology
You will probably have come across lots of sciency words and phrases over the course of your triathlon training. Coaches, fellow triathletes, magazines and websites will all use these.
Unfortunately, it is very common for these phrases to be misused or misunderstood. So, to help you avoid these pitfalls, below is a short, straightforward guide to the main phrases and words you’re likely to come across.
We have broken this terminology down into sections:-
Physiology - deals with terms used by sports scientists and the physiology of performance
Swimming - deals with terms used in swimming sessions and training
Cycling - deals with cycling-specific metrics and terms
Running - deals with running-specific metrics and terms
Planning and Training Load
In this section, we are dealing with PHYSIOLOGY. This includes a little information about the key terms you may hear in a physiology lab test. This is meant to be a practical description if you want to find out more about each of the areas there will be more in-depth articles available.
Physiology Lab Testing Session
1. Physiology
Below there is a list of some of the key terms and metrics that might be seen from a physiology lab assessment, some of these terms are pretty common and we use them outside of the lab as well. For instance, VO2max is a very common term, and many devices you have at home may provide you with an estimation of this, but they are all still estimations, the most reliable means of obtaining this information is via a lab test.
Ramp Test
These are a type of test used to determine VO2max. There are various protocols for this, but most will last 8 - 15 minutes, start at low power or speed, and increase quickly at regular intervals. Depending upon the protocol used, this increase usually occurs between every 15 sec to 1min. The rate of increase is usually 15 - 20w per minute or 0.8 - 1.2km/h. This will be affected by the athlete's weight and the athlete's expected performance level.
The test continues until the athlete can no longer hold the required power or speed.
To establish VO2max, a metabolic cart will be used to collect and analyse expired air; this means the athlete wears a facemask similar to the one in the images above.
For more information on VO2max, check out our more detailed explanation here
Step Test or Incremental Test
These are a type of test used to determine LT1 & LT2 as well as economy/efficiency and MRFO. There are a variety of different protocols for this but most will last 20 - 60min, and will start at low power or speed, and will increase at regular intervals (usually 2 - 6min). The rate of increment is usually 10 - 30w per stage or 0.8 - 1.2km/h. This will be affected by the weight of the athlete and the expected performance level of the athlete.
Different labs will use these tests in different ways, so it's not always possible to say when these will finish. Some testers will run this until the athlete cannot complete a stage, others will have a defined point at which they stop the test. This is very much up to the lab performing the test but can make it difficult to compare data between labs.
At the end of each stage, a blood lactate sample is usually taken and at some point, the metabolic cart will be used to collect expired air for analysis.
VO2max, Power at VO2max & Velocity at VO2max
The maximum rate at which oxygen can be taken up and used by the body during exercise. It is commonly recognised as the upper limit for performance in endurance events. It is one of the three main limiters to endurance performance along with economy/efficiency and Fractional Utilisation.
VO2max is expressed in absolute terms in millilitres of O2 per minute (ml/min) or litres per minute (l/min), and related to body weight as (ml/kg/min) commonly abbreviated to ml/kg.
pVO2max is the lowest steady-state power that will elicit VO2max. Most often using an incremental or ramp test, it can be extrapolated from submaximal stages.
vVO2max is the velocity that elicits VO2max, it can be calculated by using running economy, and VO2max data
These can both be used in training prescription and for evaluation of training adaptation.
Maximum Aerobic Power (MAP)
Often obtained during a VO2max short ramp test, it is the average of the power from the highest minute completed (usually the last minute, but sometimes at the end of a test power will drop slightly before the test is terminated). It will be higher than pVO2max.
NOTE: A key area for cycling is the position you perform the tests in. If you race on a Timetrial bike then you should perform the tests in that position. Using a position that is different from your main one, will lead to results that may not mean much in the real world.
Lactate Threshold 2 (LT2)
This is the 2nd significant change in blood lactate in an incremental test. It marks the boundary where the body begins to exclusively use carbohydrate as a fuel, and there is a significant increase in hydrogen ion production which inhibits muscle function leading to fatigue. Many publications, broadcasters, athletes and social media posts refer to this as the point where you 'begin to fill with lactate'. This is completely false. Lactate is produced and cleared all the time, as part of the process to metabolise carbohydrates. It does not cause pain or prevent you from performing. It is however closely connected with the increase in hydrogen ions which will cause those feelings and sensations. Therefore we use blood lactate curves as a surrogate for actually measuring an increase in acidosis.
There are a number of methods to detect this point, and there are a number of slightly different but practically related terms that attempt to describe a similar point. These include
OBLA (Onset Blood Lactate Accumulation)
Ventilatory Threshold
MLSS (Maximum Lactate Steady State)
FTP (Functional Threshold Power) - for more on this see the separate title below
CP (Critical Power)
Anaerobic Threshold
There can be a lot of variation between labs tests and protocols so it is important to maintain your process as consistent as possible, use the same lab and same equipment as much as possible. Another issue we have seen in recent times in cycling is that the power values don't match what you achieve in the real world. Often this is because power meters, despite claiming very high accuracy, don't all agree with each other. So if the test you are performing uses a different power meter to the one you use on your bike, then there is room for error. If you use a pedal-based system, we would suggest using this in the test to compare the data, that way you will know if there is a discrepancy. Some labs use smart trainers, so you can use your own bike, however, you still want the power from your bike, as smart trainers can vary significantly. There is a reason why the SRM bike, which is the gold standard, costs 20 times the price of a decent smart trainer!
Lactate Threshold 1 (LT1)
The point blood lactate begins to rise above baseline in an incremental test. There are several definitions of how to detect this point, including using specific values of lactate and a set increase above the baseline. Baseline means that there is no significant increase in lactate. When fats are being used as the dominant fuel source, lactate is produced and cleared at roughly the same rate so lactate levels remain fairly constant (~1.0-mmol/l). As carbohydrate is increasingly used, these levels will begin to rise. This is an important variable for ultra-endurance athletes such as Ironman triathletes or anyone performing over multiple hour events as this is likely to be around the intensity the athlete will be able to sustain.
This can also be known as the Aerobic Threshold
FatMax or Maximum Rate of Fat Oxidisation (MRFO)
This is the maximum rate of fat oxidisation (g/min, g/hr, kcal/min or kcal/hr). It is usually assessed in an incremental test and required the use of the metabolic cart to collect expired air. Using the O2 and CO2 data for each work rate, the required contribution of fat and carbohydrate can be calculated.
In research studies, this is usually required to be assessed in a fasted state (i.e. no calories consumed prior to exercise, and normally performed in the morning). However, in the real world, we do not perform events in a fasted state, so from a practical perspective, we normally ask athletes to consume their normal pre-event meal, 2 - 3hrs prior to the test. We want to know the effect on race day, not for a research project.
We are also interested in the workload (power/speed) that this occurs at and the relative intensity this corresponds to. This can provide important information for fuelling, training modality and adaptions.
This is particularly important for long-distance athletes as it will provide important information that can affect pacing strategies, fuelling strategies and influence the training plan.
If an athlete is dependent on large volumes of carbs even at relatively low intensity or power/pace, then even with a great fuelling plan it will be very difficult to meet the energy requirements in events over 5-6hrs.
More on how this impacts performance and training here.
