Metabolic system, what’s the deal?

Yes, I realize I have neglected my readers for a few days, since I have been writing so much for different projects that my fingers turned blue, almost.

And to make up for the few days of waiting I will start with some good comforting biomedical news: for the first time doctors in South-Africa have succeeded in a penis transplant. This remarkable feat might stuck you as odd, but it has been tried before, unfortunately in vain.

Each year around 250 men in Africa loose their penis due to things that go wrong after (or during?) a circumcision. I know, on a big scale of things, that is not a lot and probably insignificant anyhow, but don’t forget that it was easier to transplant a human heart. The first one succeeded, also in in South Africa, by Dr.Christian Barnard back in 1967!


Metabolic systems.

Metabolic systems are necessary for the supply of energy to all organs. In sport and exercise we are mainly interested in the metabolic systems of the skeletal muscle.

There are two important systems:
aerobic: if there is a continuous and sufficient supply of oxygen, this is our main energy provider. It’s the system giving you the energy right now, or as a matter of fact almost 24 hours a day, 365 days a year. The moment you start running up the stairs, lifting weights, sprinting or cycling uphill, the oxygen supply is insufficient and you start using the anaerobic system as a back-up (yes, there is also the alactic anaerobic system, consisting of ATP and Creatine-Phosphate for immediate ATP-resynthesis , but this system is not measured).

This results in the production of lactic acid which is the signal that this intensity cannot be maintained for a long time.

Although there is still an on-going scientific discussion, we are assuming this happens at a specific intensity or level of exertion, and it can be measured. The heart rate at which we start to produce lactic acid is maybe not the only cause of fatigue, but at least a good biomarker for anaerobic fatigue.
Remember however, that we always produce lactic acid, even in complete rest. But in rest the lactate clearance capacity is in balance with the continuous production of lactate, so the resting level of lactate is more or less constant at around 1 mmol/L.

It is called the aerobic-anaerobic threshold or lactate threshold. So if your endurance is insufficient, your threshold might be 140 BPM or lower. When you have a good endurance your threshold can be at 170 BPM or higher. Basically: the higher your threshold, the later you start producing lactic acid and the longer you can maintain an exercise at a higher intensity level.
It’s not easy to shift this threshold upward by training. It might go up a few points but never 20 points. The lactate threshold reflects your aerobic fitness.

It should also be mentioned that working under the threshold does not mean that the work is 100% aerobic nor does working above the threshold mean that the work is 100% anaerobic, it’s always a mixture of aerobic and anaerobic processes supplying energy.
It is an indicator that the production of lactate starts to surpass the lactate clearance rate

This threshold is the foundation of the heart rate zones as shown by the Omegawave system. It indicates with which heart rate you have to train in order to train the right metabolic system.

The threshold is interesting in the longer term development of aerobic fitness. It is not very useful to measure on a daily base which is why it is not displayed by the Omegawave system. Compare it to the patrol tank of your car. The size of your tank will not change even when you drive a lot. What does change however is your fuel level which is displayed on your dashboard.

Our body has the advantage of having two fuel systems (aerobic and anaerobic). They complement each other but are relatively independent of each other.

Metabolic system                              Aerobic                                                     Anaerobic
main fuel                                             fats and carbohydrates                         only carbohydrates
dependent on oxygen supply          yes                                                             no
capacity (total amount of energy) very high                                                   low
power (energy per time unit)         low                                                             high
breakdown products                        carbon dioxide and water                     lactate
aerobic-anaerobic threshold          under                                                         over

For daily training, the status of the aerobic and the anaerobic system is much more important than the lactate threshold. They change on a daily base depending on the kind of workout you do, the exercises, the intensity, the volume and the rest periods. With some exercises only one system is tapped into: if you jog slowly for an hour with a heart rate of 130 BPM, while your threshold is 160 BPM, you will only use your aerobic system. If you run 400 meters at full speed with a maximum heart rate of 190-200, and your threshold is 160, you will mainly use your anaerobic energy supply system. During most workouts however both systems are used simultaneously.

If you want to train again the next day, you can use the Omegawave system to check which energy system has recovered from the previous training and which system you should avoid using since it did not recover from the previous training.
You can do this by checking the aerobic readiness and anaerobic readiness which reflect the actual status of each system.

Keep in mind that both systems do not recover at the same pace! The aerobic system recovers faster than the anaerobic system. Example: at the day of the finals of World Championships or Olympics, one can see the elite long distance runners running fast and long in the morning or at their warming up before their finals. Their aerobic system, which is a recovery system in itself, recovers very quickly especially in the well-trained super athletes. Running a hard anaerobic run, e.g. 400 or 800 meters right before the finals, will result in a unrecovered anaerobic system.

If you test yourself with the Omegawave system before, immediately after the workout and let’s say every 2, 3 or 4 hours after the workout, you will see the “famous” recovery curve or supercompensation curve. And this for each separate system! It might not always look like the smooth line you see in the books, but if you continue testing you will find it.

This supercompensation curve is very important as you are now able to adjust your daily workload or training to the actual status of your body, and this is what counts. In other words: it will show you your Windows of Trainability (more about this in the next article). Are the different physiological systems, and in this case metabolic system, ready to be tapped into again, or not yet?

From time to time you will find you have to adjust the workout because the Omegawave system suggests to do a different kind of training or different exercises and to change the intensity and/or volume from what you had in mind. Why is this?

1. If both systems are recovered, both can be trained again today.
2. If one or both systems have not completely recovered the Window of Trainability is  not fully opened. This does not mean you cannot train at all: you can choose to do some light technical work, work on drills and skills and not tap into your energy sources too deeply. So: a light workout with a very low heart rate.
3. If the aerobic system is not recovered, you could still work anaerobically or e.g. lift weights.
4. If the anaerobic system is not recovered, you can work aerobically with a heart rate below or just above the threshold, you can find this in the table with the heart rate zones.
5. Even if a system is not recovered you can still train that system. However keep in mind not to do this too often, it might lead to overreaching. This doesn’t have to cause a problem, as long as you monitor this and you realize that you are doing this. If not you will probably experience a loss of sharpness (feeling flat on a competition day), with an over-trained state or with injuries.
6. For some people it is disappointing to see the numbers of the aerobic and anaerobic system not increasing in the long term. Keep in mind that even after driving your car for 10 years, the size of the petrol tank is still the same. The body has a limited capacity for energy storage.

Never forget that the level of the metabolic system or aerobic and anaerobic readiness do not only depend on the intensity of the training, but also on the speed of your recovery. This explains why even after performing the same workout, the next day one athlete is completely recovered while the other (of the same level) still is not.
If you are always in the green, your metabolic recovery is fast….. great!

Realize that every measurement is just a snap shot, the long term overview of the measurements will give you a clearer picture of the dynamics of adaptation to training. Always keep an eye on your own baseline values, that is, the results of the past measurements, to interpret your current result.

Here’s an example of the development of aerobic readiness:

Dynamics of aerobic readiness in an athlete

Dynamics of aerobic readiness in an athlete

All measurements were made before the work out. If you look at the latest test on the right, you see the aerobic readiness is low (107). This is really low: the earlier 7 tests gave an aerobic readiness between 120 and 130. This significantly lower level of aerobic readiness in comparison with the earlier measurement, carries the warning of the aerobic system not being recovered at all. In other words: today be very cautious when doing an aerobic workout. There might be a price to pay. More about this in Cost of Adaptation.


About Henk Kraaijenhof

My name is Henk Kraaijenhof and I started this blog as a random collection of concepts, ideas, stories and events that are important or interesting to me in my work as an international performance consultant in a wide range of fields, and sometimes outside of my work. I will try to post a new entry every 3-4 days. Feel free to comment if you like.
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