Performance of the aerobic metabolism
The processing of the aerobic metabolism is characterized by two fundamental notions: the power and the endurance.
Evaluation of the aerobic power
By definition, a power represents an amount of energy consumed or produced during an unit of time. It is usually measured in Watt, but can be evaluated by various ways.
The consumed power comes directly from the amount of used oxygen.
VO2 = Consumed oxygen flow (litres/min)
In aerobic effort, the consumed oxygen (VO2) increases proportionally to the intensity of effort, but over a particular intensity value (critical intensity), it doesn't increase anymore. It's the lactic anaerobic metabolism which (possibly and momentarily) allows over passing the critical intensity (final sprint for example).
VO2 evolution as a function of intensity of effort:
VO2 maximum = Maximum oxygen flow (litres/min)
It represents the maximum consumed power. It can be experimentally measured with physical efforts using at least 2/3 of the muscular mass.
VO2max = Weighted maximum oxygen flow (ml/min/kg)
It's the VO2 maximum divided by the body mass. It represents the aerobic potential. It varies from 40 ml/min/kg for a sedentary adult to more than 80 ml/min/kg for a high level sportsman.
A high VO2max is a necessary condition (but not sufficient) to get good performances.
The produced power is the consequence of the consumed power.
MAP = Maximum Aerobic Power (W)
It's the power produced at VO2 maximum. It can't be maintained more than 6 to 8 min depending on level.
Power/Weight = Effective potential (W/kg)
It's the ratio between MAP and body mass. It represents the real potential to obtain the best performances but only for the sports where the weight is involved.
In the main aerobic sports (running, cycling, swimming, rowing, etc.), the produced power allows the movement of the athlete. The speed obtained is easily measured.
MAS = Maximum Aerobic Speed (km/h)
It's the critical moving speed corresponding to the VO2 maximum. It is used instead of MAP which is more difficult to measure (running, swimming, etc.).
The energetic yield is the ratio between the produced power and the consumed power. It's a number between 0 and 1 because the metabolism consumes more than it produces.
For running, the yield is evaluated with MAS and VO2max. Within previous unities, we have:
VO2max / MAS = 3.5 ± 5%
The error margin represents the yield variation (running efficiency). It should not be neglected because runners having identical VO2max can have slightly different MAS and therefore clearly different performances.
Evaluation of the aerobic endurance
The evaluation of the aerobic endurance consists to analyse the decrease of the aerobic power during time.
For running, that is equivalent to measure the mean speed on a given distance and to compare it to the MAS. By dividing the mean speed by the MAS, we define a percentage %MAS which decreases with the distance.
For runners having a good MAS, the following table is experimentally defined:
|Track distances||%MAS required|
|400 m||145 to 155|
|800 m||120 to 125|
|1 000 m||105 to 115|
|1 500 m||101 to 111|
|2 000 m||98 to 102|
|3 000 m||95 to 100|
|5 000 m||90 to 95|
|10 000 m||85 to 90|
|20 000 m||80 to 88|
|42 195 m||75 to 84|
More precisely, in the races using essentially the aerobic metabolism (2000 m and upper races), the evolution of %MAS gives the following curves.
%MAS evolution for three levels of endurance:
Drawn using a logarithmic time scale, the preceding curves become lines from which the falling gradient AEI can be calculate to evaluate the aerobic endurance.
AEI = Aerobic Endurance Index
It's the value got from the formula:
AEI = ( 100 - %MAS ) / ( Log7 - LogT )
This index allows getting the following levels:
Out of technical aspects depending on sport, power (mainly) and endurance (secondly) are therefore the two fundamental elements to consider to improve the aerobic performances.
Even if endurance is less important than power, it should not be overlooked because it can eventually compensate a slight lack of power.
For example, two runners whose MAS is 18 and 19 km/h respectively, can reach 37 min on 10 000 m, because the first has a high endurance and the second a mean endurance.
Basic rules to improve aerobic performances
To develop aerobic power, you must train in intensities near the critical intensity. It's impossible to develop power when training in too low intensities.
To develop aerobic endurance, you must train on long periods at intensities more and more important. It's impossible to develop endurance when training on too short periods.
Do not forget you can easily lose what you hardly got. If you stop your training for two or three weeks, you will lose all what you got during several months.