Realizing your full potential, being the best you can be—it’s something many people strive for. It doesn’t matter if it’s in your career, relationship, or favorite video game. Trying to become the best you can be is universally understood. In sport—it’s the main objective. It doesn’t matter what you play, the number one goal is always the same. To get better. 

Unfortunately, the human body, our physiology, isn’t entirely understood. New theories and methods are endlessly tested to find the ultimate equation to maximize athletic performance. The pieces of the puzzle aren’t all in place—but it’s coming together. The picture is becoming clearer. 

We understand the general principals governing how our bodies work. This allows us to create effective programs and workouts, but we still don’t know enough about individual variability to address the unique training needs of every person. 

The dynamic relationship of our energy systems (anaerobic and aerobic for the sake of this article) is a good example of something we don’t entirely understand. The research is still underway. But, luckily we know enough to move us in the right direction. 

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

Correct – It depends on other factors. Good job. 

The sections below outline the relationship between the two main contributors to endurance performance—aerobic capacity (Vo2max) and anaerobic capacity (VLamax).

FTP, VLa Max, VO2 Max

What are Vo2max and VLamax?

Vo2max (ml/kg/min): 

This is 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.

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. Clear as mud, right?

You’ll remember from a recent article about the Sweet Spot vs. Zone 2 debate in which I detail the change in lactate production from aerobic to anaerobic energy production:

In exercise where lots of oxygen is present (aerobic) your body will produce more pyruvate and less lactate. When you continue to push yourself into the higher power zones and above your lactate threshold, oxygen levels in the cells will decrease and you will go into anaerobic energy production, thus producing increased lactate and decreased pyruvate.  Continue to push harder and the levels of lactate produced will continue to increase while pyruvate levels decrease. I.e. the fuel ‘mixture’ of fat (pyruvate) to carbohydrate (lactate) changes as an athlete works closer to their individual lactate threshold.

So, we’re always producing pyruvate and lactate, but as the oxygen levels in the cells decrease, i.e. you start to push the pedals harder, the body will convert more pyruvate to lactate and your lactate concentrations will increase. Since we can’t easily measure pyruvate, but can lactate, we have VLa Max… Capeesh?

Why Does it Matter for Performance?

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. “Shayne, this is the most confusing article EVER, dude”. Hang on a sec, here’s are example…

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 VLa of .7 mmol/s/l and cyclist 2 has a VLa of .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.

So, to K.I.S.S. – IF you need to produce lots of power for a short duration, THEN having a higher VLa is desired, BUT IF you need to go long and keep power down forever, THEN having a lower VLa is desired.

How you train will have a significant impact on how your energy systems adapt and interact. Obviously the way your systems function can be improved—that’s why you train. 

But what’s the right balance of training to optimize your adaptation?

No matter what event you’re training for—you will rely on all of your energy systems. 

“Designing a workout to induce just one specific biological adaptation is impossible. Most of the time there is a major effect (class effect) coupled with minor effects whether desired or not.” 

– Olbrecht, “The science of winning”
FTP, VLa Max, VO2 Max.

What Does it Mean for Training?

A basic principle of physiology that’s important to understand when considering how to improve your performance is the dimmer switch effect. A dimmer switch allows you to adjust it across a spectrum of levels based on your needs. The energy systems of your body operate in a similar way. 

See, your body uses three different systems to get energy (yes, I am combining the 2 CP systems, nerd!). All three are always on but the amount each contributes depends on the energy demands of activity. 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.


Let’s use fireworks…so, your Creatine Phosphate (CP) system is like a firecracker producing a lot of energy, but for a very short amount of time. Next up is your anaerobic system (VLa) which is more like a sparkler producing a fair amount of energy, but for just a few minutes. Lastly is your aerobic system (VO2) which is like a lighter, producing enough energy to get the job done, and will continue to burn low and slow as long as there is fuel in the tank.

Huh, huh, huh huh FIRE! FIRE!

Sorry, I had to… Back on topic, Shayne! C’mon, man!

Low intensity exercise requires less energy allowing us to use our slowest, most efficient energy system with only small contributions from the other two. As your exercise intensity changes, the contribution ratio of each energy system also changes.  More intensity means more energy in less time. Your aerobic system will start to contribute less as your anaerobic system turns up. 

The dominant system or systems, the ones that are “stressed”, will experience training adaptation. Any system that isn’t needed will not be trained and will experience a decrease in functional capacity. 

How you train changes the amount each system will adapt. By emphasizing endurance training you’re going to up regulate aerobic contributions and down regulate anaerobic contributions—and vice versa. Focusing on speed and intensity will improve anaerobic functioning but limit your aerobic system. 

To find the right balance, you need to strategically vary your training sessions. Identify your training goals to help you determine the types of sessions to emphasize in your programming. 

If you’re training for endurance events the vast majority of your training should emphasize your aerobic energy system—around 80% of all training. The results of this are two-fold—your anaerobic system gets weaker and your aerobic system gets stronger.

Nutritional Suggestions

As an athlete with a higher anaerobic contribution, you should consume more carbohydrate before and during exercise. If you rely more on carbs and glycolysis, your blood sugar levels are going to decrease more quickly. During competition using a carbohydrate supplement will help maintain your blood sugar.

Another word of advice, if you have a very high intensity workout planned for the day, make sure you’re eating a carbohydrate-rich meal before and after your workout. This will ensure you have enough glucose to get through the workout, as well as replenish glycogen stores afterwards.

Regular dietary habits can also impact substrate use during exercise. If you have a high-fat diet, your body promotes systems that use fat more than carbohydrate. During exercise this translates to less glucose use and longer workouts. So, if you are trying to improve your aerobic capacity, eating more fat and less carbohydrate throughout the day, as well as doing some workouts fasted is a way to ‘bio-hack’ the system and get you greater results in less time.

FTP, VLa Max, VO2 Max


Properly adjusting training intensities to fit your overall training goals will result in an overall more effective program. While there are some nutritional suggestions, our performance abilities will be reflected largely by our choice in training. Make sure you’re applying Specificity and Progressive Overload to whatever system/s you’re trying to improve. Lastly, as one system becomes up-regulated (improves), the other will become down-regulated (worsen), and there are just a few genetic ‘freaks’ that are good at everything. If you are struggling with moving up in the ranks, you may want to adjust your training to further improve your strengths, and change what events / races you want to ‘peak’ for… Or maybe you want to try and improve your weaknesses instead… We can’t lose the art of coaching in all this ‘sciencey’ stuff after all!

Recommended Posts

No comment yet, add your voice below!

What are your thoughts?