physiology

The VO2max in fitness

It is the maximum oxygen consumption that a subject presents in the course of rhythmic, protracted and intense muscular activity, which engages large muscle masses (usually the lower limbs), breathing air, at sea level.

In practice it is the maximum quantity of O2 that can be captured - transported - used by the body and represents the ability of an individual to produce and use energy, generated by the aerobic oxidative system.

These two definitions, not exactly scientific, help us to understand the importance of VO2max as a parameter for assessing the cardiovascular fitness status of an individual.

The American Heart Association drafted in 1972 a table in which the various fitness levels are classified according to age, sex and relative VO2max.

We then begin to distinguish between absolute and relative VO2max :

The first expresses the ability to use oxygen in liters / minute, while the second considers in this ratio also the body weight and the expression is transformed into ml / Kg / min. The relative value is more suitable for evaluating individuals who do not have specific competitive or very high level requirements (ie all of us ic practitioners !!)

How to calculate the maximum oxygen consumption in your gym?

Let's start by saying that maximal and direct tests are the exclusive competence of medical personnel carried out in properly equipped centers. We can only carry out submaximal and indirect tests, which use the heart rate as a reference parameter (there is a mathematical correlation between% HRM and% VO2max) and which in any case do not exceed 80% of HRM. I want to clarify that this value is the maximum that the current legislation allows in the presence of a medical certificate issued by the general practitioner. Everyone draws their own conclusions.

I personally consider the YMCA bike protocol to be valid (Golding, Mavers, Sinning, 1989). This test uses only three or four phases with increasing intensity on a cycle ergometer and if during the execution the subject exceeds 85% of HRM the test is interrupted and only the available data are used. The first phase is the same for everyone, you start pedaling with a load of 25 watts, while the remaining loads vary depending on the cardiac response.

It should be noted that in trained subjects the values ​​will be overestimated, whereas in sedentary subjects they will be underestimated.

It is useful to know that in direct correlation with the relative VO2max the MET or metabolic equivalent is set which is defined as a multiple of the basal metabolism. The report can be expressed as follows:

1 MET = 3.5 mlO2 / Kg / min

This very important relationship, on the condition of knowing the basal metabolic rate of the subject under examination, gives us the exact measure of the energy expenditure required to carry out a specific work that lasts for a certain time.

This notional list will leave us indifferent and perhaps a little confused. An example could perhaps awaken the attention and make the concepts quickly expressed clearer.

Subject: Francesco Calise

age: 41 years

weight: 68kg

height: 174 cm

Fat mass: 6%

Fat mass: 4Kg (protocol Jackson et al.)

MBR reconstruction: 1996.8 Kcal / d (Keys and Grande protocol)

Absolute VO2max: 4.30 l / min

Relative VO2max: 63.2 ml / min / kg

MET: 18.06 (= VO2max rel (63.2) / 3.5)

We assume that the person indicated is going for 45 minutes. an activity that engages it at an average of 70% of the maximum heart rate (FCM) (a type class of ic) here is what we can get:

We know that 70% of FCM corresponds to 56% of VO2max, so the average metabolic commitment for the duration of the exercise will have been 56% of 18.06, that is 10.41 Met.

Basically for 45 minutes I will have sustained an energy consumption about 10 times higher than my MBR (basal metabolic rate), so here is the simple calculation to do:

[(199.8 / 24/60) x45] x10.41 = approximately 650 Kcal

of which 56% for sugars and the remaining 44% for fats (direct correlation with the average percentage of VO2max). Wanting to complicate our lives and going further with the calculations we get the grams of fat used during the exercise (without considering the work of our body for the restoration of stocks of liver and muscle glycogen)

(650x44%) / 9 (the Kcal contained in 1g of fat) = 31.8 g

At this point I would make two reflections.

The first is that the more you are trained (the constancy pays much more than the stoic one-off suffering) the more you consume at the same work intensity, the second is that with little knowledge you get data that at the fitness level are much more reliable ( because they are really personalized) compared to those indicated by very expensive heart rate monitors.

ESSENTIAL PRECISATION:

What is written is valid only for healthy subjects and in the absence of existing pathologies and assuming a non-protein respiratory quotient ....

... about this last topic, you have never heard in the gym sentences (often for the use of gentilesesso) like: "Finally, after so many sacrifices I lost X Kg but now I'm obviously a little more flabby, starting tomorrow I'll start to do something to firm up! ".

At this point the "devastation" took place !!!!

Training error added to feeding error, continue ...

Francesco Calise

Personal trainer, Schwinn Cycling instructor, postural gymnastics, yogafit and Mountain bike