Understanding FTP: VLa Max vs. Vo2 Max – What triathletes need to know

Written by Chris De Nil from Tri Connect Coaching https://www.sported.ae/coaches/chris-de-nil/

1 September 2020

Why are we all chasing the magical FTP number? Yes I did as well, but my way of looking at FTP has totally changed since I did the Inscyd test and the results were a real eye opener!

Realizing your full potential, being the best you can be—it’s something many people strive for. Trying to become the best you can be is universally understood. In sport—it’s the main objective.

In endurance events, it’s understood that our Vo2max is an indicator of how well we perform. But, what if someone has the same Vo2max as you – who’s going to win?

It depends on other factors. What are those?

In today’s world of cycling and among triathletes, one number reigns supreme: FTP. Pride and maybe an obsession, will have many athletes pay coaches good money to improve it.

Everybody talks about FTP [functional threshold power], and everyone wants to improve it. But if I walk up to any coach and ask about the mechanism or physiology – “what is under the hood” that creates FTP and how can you change it, most coaches can’t answer. If we understand where power comes from, then we can understand how to improve it. But is FTP, the only number we should be looking at — or is it even the most important one?

That is where Inscyd’s Power Performance Decoder comes into play: I did the test myself and all you need is a few all out efforts (20sec, 3min,6min,12min) with power data. Send me the fit. files and you are on your way to better understanding your physiology.

Once tests are completed, INSCYD breaks down where power comes from.

What INSCYD quantifies for riders includes:

• VO2 Max / aerobic capacity
• VLaMax / glycolytic capacity
• Anaerobic threshold (FTP)
• Economy / efficiency
• Composition of power output (aerobic vs glycolytic vs creatine phosphate)
• Fat and carbohydrate combustion
• Fatigue and recovery

Lets start with an overview of the metabolic systems used in endurance sports:

There are three metabolic systems that help a muscle produce energy. By energy here, we mean the energy needed for locomotion. The three sources of this energy are:

1) Breaking down creatine phosphate – this is a fast source of energy and only lasts a few seconds.

2) Glycolysis (aka anaerobic system) – where you transfer glucose or carbohydrate into pyruvate or lactate.

3) Aerobic metabolism – where you use oxygen to burn things – you burn the pyruvate or lactate to make fuel, or burn what comes out of the beta oxidation.

These are the only way energy or power is produced on the bike. Power is provided by a composition of these three systems simultaneously. The shorter the duration and the higher the intensity, the more you tend to use your glycolytic and creatine phosphate (anaerobic) systems. The longer you go and the lower the intensity, the more you are depending on your aerobic systems. However, how much you depend on one system or another can differ dramatically between athletes, even for the same efforts. This isn’t necessarily given by genetics, but it depends on the athlete’s training.

Our energy systems can be divided into two key categories: aerobic and anaerobic. And both our total strength as an endurance athlete and our rider type are a function of the relative balance between these two systems. How they interact may tell us more about our FTP or threshold strength than a simple power number.

Each one supplies energy at a different rate and a different quantity. The fastest system supplies the least amount of energy; while the slowest system produces the most- this is your aerobic system. Your anaerobic system is somewhere in the middle.

Now for the next step let’s look into more depth the relationship between the two main contributors to endurance performance—aerobic capacity (Vo2max) and anaerobic capacity (VLamax).

Understand what is Vo2max and VLamax?

Vo2max (ml/kg/min):

This is your aerobic capacity. Vo2max, or maximal oxygen consumption, refers to the amount of oxygen someone can use during max effort exercise. This is widely considered the gold standard for evaluating cardiorespiratory fitness. VO2max = your maximum aerobic oxygen uptake. The oxygen uptake itself though is not something we are interested in. The question we are trying to answer is: how much power/ATP can you produce in your aerobic metabolism.

VLamax (mmol/s/l):

This is anaerobic capacity, or the maximum rate of energy production by the glycolytic system. It is sometimes designated by the term VLamax or maximum production of lactate. In reality this is the maximum rate of production of pyruvate and lactate but since lactate is what is measured “La” has been used for this term. VLaMax = the maximal lactate production rate. VLaMax is a marker for the maximal capacity for performance of your glycolytic system. Every time you produce lactate in the glycolytic system, there’s a production of ATP attached to that.

If you have short time effort, e.g. 100m sprinter/50m freestyler in swimming, they will need to maximise their VLaMax because they need high glycolytic energy production. You will see tremendous differences in VLaMax for different types of athletes.

It will also change a lot throughout the year depending on what training you’re doing. E.g. if you’re training weights in the gym, you may see it rise. Triathletes who finish their off-season having spend a lot of time weight training in the gym may have elevated VLaMax compared to their on season.

How VO2max and VLaMax influence FTP:

FTP (functional threshold power) is the modern power training term for anaerobic threshold. It’s the maximum intensity you can hold without accumulation of lactate, or the fatigue that goes along with that phenomenon. It’s related to your 10km running speed or your 1-hour time trial performance. Your VO2max and your VLaMax determine approximately 97% of your FTP. This is because your aerobic system defines how much lactate you can combust. Your glycolytic system determines how much lactate you produce. When it comes down to it, Vo2max and VLamax are comparisons of your aerobic and anaerobic systems. The relative strengths of these two systems will determine your performance capabilities.

As an endurance athlete, the %Vo2 you can maintain is directly related to how strong your anaerobic energy system is. The stronger your anaerobic system is, the more it will contribute at any given intensity. This makes you reach threshold faster—reducing your endurance capacity. These two combined determine what your FTP is. If you want to increase your FTP, you are better off understanding what your VO2max and/or VLaMax are to decide which you need to work on. In endurance sport, people often train to change their FTP or prescribe training programmes without understanding the mechanics behind it. If you have a high VO2max it will lift up your FTP power. If you have a high VLaMax it will decrease your FTP power.

• Example – Think about two cyclists with the same aerobic capacity; Let’s say 55ml/kg/min, and identical lactate buffering abilities. Cyclist 1 has a VLaMax of 0.7 mmol/s/l and cyclist 2 has a VLaMaxof 0.2mmol/s/l. During exercise, cyclist 1 will experience blood lactate accumulation faster than cyclist 2 because of their higher VLa. As a result cyclist 1 will fatigue at a lower percentage of their Vo2max than cyclist 2. HOWEVER, cyclist 1 will crush cyclist 2 in a sprint, or short steep hill climb.

• If you don’t know what is behind the FTP, you can’t really establish a precise and focused training programme.

• Decreasing VLaMax and increasing VO2max would require different training programmes

IF you need to produce lots of power for a short duration, THEN having a higher VLamax is desired, BUT IF you need to go long and keep power down forever, THEN having a lower VLamax is desired.

Another key point in performance: Substrate Utilisation

As a triathlete you probably don’t need to sprint, so you probably won’t be that interested in your VLaMax. However, the reason why you should care is because if your VLaMax is higher it means that you need a substrate to do that. The only substrate your body can use to produce lactate in glycolysis is glucose. This means the higher your glycolytic system is trained (i.e. the higher your VLaMax), the higher your glucose utilisation is. This is also true in endurance conditions. So if you have a high VLaMax it means that your metabolism depends more on glucose and you burn more of this fuel and use less fat.

If you had the same two athletes with the same FTP but different VO2max and VLaMax and they ride at the same pace, the athlete with the higher VLaMax will be oxidising more carbohydrate than the other. Whenever your metabolism is producing a lot of energy and lactate, you are not burning fat. Let’s say you do a hard interval session, and then 6min recovery in between the intervals. You assume you’re burning a lot of fat. However, in the 6 minute recovery for intervals, you’re not burning fat. You’re doing it just to burn lactate. Whenever there is a lot of lactate production, you’re not using fat. It’s much easier for your muscles to use primary fuels, so whenever it’s there your body will use that.

Training implications:

Percentage of FTP comes from percentage of lactate threshold. It works in terms of a practical application. However, there is a systematic limitation because your FTP is not directly related to one single metabolic system. In gym training, you base your intensity for squats on your one repetition maximum in squatting. You don’t base it on your one rep maximum in the bench press because it’s a different muscle system. This is the problem with basing your training on your FTP – it’s not a clear link to just one metabolic system. When you train at a percentage of your FTP, you cannot understand how much stress you put on your aerobic system or your glycolytic system. For example if you put 10 people on the same training programme based on % of FTP, 5 people will develop in one direction, and 5 in the other. This is because the actual training of their aerobic and glycolytic systems will be completely different.


INSCYD returned an eight-zone Training Zone chart, with room for customizable zones as well. While the threshold is identical to my TrainingPeaks setup, and zones 1-3 are quite similar, the lactate shuttling was a new one for me. At the low end, 215w, is my ideal output for clearing lactate, while recovery I thought of as just going as easy as possible to take a break, not anymore. While familiar with the idea of ‘flushing’ out efforts, I guess I never thought about generating a certain amount of watts to combust or burn through lactate. So, I may pay more attention to pedaling in that 215w range after hard efforts in training. The top end of lactate shuttling is the intensity at which lactate accumulates at same rate as I can metabolize it.

INSCYD also delivers a detailed report for eight training zones, with a wattage target and upper and lower limits for each. As a longtime TrainingPeaks user some of the zones looked very familiar to me: recovery, base, ‘medio’ (which I would call tempo), anaerobic threshold (which I would call FTP or just threshold). But some were new to me, such as FATmax, aerobic maximum, high anaerobic and lactate shuttling.

INSCYD defines each of these zones based on testing (and modeling), not just percentages of FTP power, the way many training applications do. But while the INSCYD system measures or calculates a variety of things, it does not prescribe anything in terms of training. That is left entirely up to the coach.

With the INSCYD report you can now determine target wattages for over-under threshold intervals, based on lactate accumulation and combustion rates.

INSCYD can also create a virtual athlete with projections based on tweaking various metrics, giving coach and rider targets to shoot for.

And, like with any system of measurement, a primary benefit of INSCYD is recording multiple testing sessions over time to track improvements or losses.

INSCYD’s website is www.inscyd.com if you are interested in learning more or to book your special introductory offer for the INSCYD test please have a look at www.triconnectcaoching.com

Posted on 8th Sep 2020