International references
1 - Indirect tests
In the laboratory, the most widely used have been described by I. Astrand - on a cyclergometer - and by Jansson - the Harvard step test.
heart rate
In some people, oxygen uptake may increase relatively faster than heart rate when exercise becomes very intense
These tests assess VO2 max from the linear relationship between oxygen uptake and heart rate. The advantage of these tests is their simplicity and their low material cost.
Their major drawback is due to the approximation of the estimate. Indeed, these evaluations do not take into account the two individual variables of heart rate :
- its non-linear progression at the end of the exercise in certain subjects ; the VO 2 max is in this case underestimated (fig. 1) ;
VO2 max
VO2 max for men's national teams
- extrapolation of the theoretical maximum heart rate as a function of age. We often forget that Astrand's formula (HR max = 220 - age) is valid at w 10 beats minutes ( !) ; again, there may be an underestimation or overestimation of the assessment.
Last note on these tests : an evaluation cannot be used in a training follow-up. Its imprecision makes any qualitative and quantitative analysis of training during the season uncertain.
VO2 max
VO2 max for women's national teams
In the field there are many tests evaluating the VO2 max. Their major interest is the group assignment.
The Cooper test has long been used the most because of its simplicity : it involves running the longest distance on the track in 12 minutes. VO2 max is estimated from the formula : VO2 max = (distance x 0.022) - 10.69, expressed in ml.min-1 kg-1. This test is easily carried out for athletes with endurance qualities : runners, triathletes, cyclists, Nordic skiers ..., but the result underestimates all those who are not used to continuous efforts and who start too quickly then walk and start again, or on the contrary those who start too slowly and finish quickly.
This drawback no longer exists in the progressive tests which emerged from 1980 : Léger and Boucher, Bru, Brue and Chanon tests.
Lactatemia
Lactatemia: the main advantage of micro blood sampling at the ear is its painless nature
These tests differ in their protocol but they are based on the same principle : the athlete must follow a progressively increasing rhythm - every one or two minutes - imposed by a magnetic strip or a bicycle until he picks up. From a reference table and the last level reached, the VO2 max is evaluated.
Thus, the Léger and Boucher shuttle test is the easiest to perform, because a space of around thirty meters - gymnasium, schoolyard, dry lawn, road, track, etc. - is sufficient for back and forth between two lines 20 meters apart . The first level is walked then the speed increases every minute. The rhythm is given by a magnetic tape. The last level reached corresponds to an estimate of VO2 max very close to reality - less than 5% error in our personal experience.
This test also has the advantage of being able to be performed by children or the elderly. It is particularly suitable for poorly trained athletes or non-specialists of long distances. For the latter, it is better to use the version of the test Around on the track or similar tests : Brue, Chanon, Bru ...
2 - Direct measurement of VO2 max
It requires expensive equipment (more than 250,000 F ), whether they are fixed or portable analyzers (type k4, from Cosmed). Even if it means investing in this price range, it is essential to have specific ergometers : treadmill reaching 30 km / h , Orion or Technogym type ergocycle, Concept II type rower ... The mouthpiece is preferable to the mask because the risk of leaks is less during maximum efforts. The protocol will always be triangular, that is to say by gradually increasing the exercise power, but it may differ in its realization depending on the objectives sought.
If the sole measurement of VO2 max interests the athlete (in technical-tactical sports for example), it is not necessary to stop during the event. The following protocol can therefore be used on a treadmill : warm-up of 10 min at 8 km / h-1, then increase by 1 km / h-1 every minute until the athlete himself stops. This test is similar to progressive field tests and has the same purpose : the measurement of VO2 max. On the other hand, it is impossible to precisely determine the anaerobic threshold that can be used for training in this type of test.
If one needs to determine with precision the anaerobic threshold (the case of "endurance" sports, but also of all sports where jogging is used in preparation), it is necessary to use protocols with stages making it possible to reach a stable cardiovascular, pulmonary and metabolic state (therefore stages of 3 min minimum) and stops between stages intended to carry out a blood micro-sample for the measurement of lactatemia. For example, at Insep, we start the warm-up at 8 or 10 km / h - 12 km / h-1 for good marathoners - then in 4-minute steps, increasing each time by 2 km / h with intermediate rests of one minute. On ergocycles, the protocol is identical, the power increment being 100, 175, 250, 300, 350, 400, 450 watts (see bibliography).
This type of protocol makes it possible to determine the level of the anaerobic threshold from the ventilatory and lactic thresholds, which makes it a directly usable parameter. The criteria for obtaining the VO2 max are : exhaustion of the athlete, a maximum heart rate which stagnates, a respiratory quotient greater than 1.10 and a lactateemia greater than 8 mmoll-1
Carrying out this test is long (approximately 45 minutes for trained athletes) and expensive. But it is the only one that makes it possible to adjust training speeds for high-level athletes.
The value of VO2 max in a trained athlete is not different between the continuous protocol without intermediate stop and the step protocol with stops.
All results should be interpreted against existing references (Tables I and II) and in relation to the subject itself and its objectives.
Thus, a VO2 max of 55 mlmin-1 kg-1 in a footballer does not need to be improved, as the forms of training intended to do so would hardly be supported by the player. Indeed, in the previous scenario, the player would have to perform exercises of the type 5 times 500 m once or twice a week at the maximum aerobic speed (i.e. the speed at which VO2 max), with a recovery time roughly equal to the race time !
On the other hand, it may be useful to include in a marathoner's program, once or twice a week, sessions of 5 to 10 times 1000 m in 3 minutes - with 3 minutes rest - if his VO2 max reaches 20 km / h-1 (that is to say 3 min per 1000 m ) and caps at 65 mlmin-1kg-1, and if he wishes to progress in the marathon.
The major disadvantage of VO2 max is that it does not progress much during a season, except to develop it specifically, as described above. On the other hand, the progression of the anaerobic threshold is more spectacular and corresponds to an achievable training for any athlete, on condition of not running faster than the speed reached at the anaerobic threshold during jogging from 30 minutes to 1 h 30 performed two to three. times per week. This determination is made on the basis of the ventilatory and lactic thresholds. The heart rate reference reached at the anaerobic threshold can be used in the field by the heart rate monitor, and the heart rate not to be exceeded is the HR at the anaerobic threshold.
stress test protocol
This is also the only case of rational use of the cardio frequency meter.
IV - Conclusion
The stress tests used by athletes are numerous, more or less sophisticated and difficult to interpret. We have shown the main limitations, which does not prevent us from using them. But we must always keep in mind that they must be directly interpretable and usable on the field by the coach and the athlete.
V - Lexicon
V02 max : Maximum oxygen consumption obtained during an exhaustive exercise. It is expressed in milliliters of oxygen consumed per minute of exercise and per kilogram of body weight : mil.min-1 kg-1.
Maximum aerobic power (PMA) : This term is synonymous with V02 max, but it also expresses the power of exercise - in watts, joules or kilogram meters - at which V 02 max is reached .
Maximum aerobic speed (MAS) : This term refers to the speed on a treadmill or in the field - running, cycling, Nordic skiing, swimming - at which the V 02 max is reached . The three terms V02 max, PMA and VMA are practically synonymous, but be careful : the V 02 max can vary without the power of the exercise changing, and conversely, the V 02 max can remain stable, while the PMA or the VMA increase or decrease !
Anaerobic Threshold : Maximum level of exercise at which a stable metabolic state is maintained, which, in theory, allows exercise to be maintained as long as energy reserves exist. There are three methods of determining the threshold.
1) The ventilatory anaerobic threshold corresponds to a stable state of gas exchange for a respiratory quotient of 1. The onset of dyspnea felt during jogging corresponds to this threshold.
2) The lactic threshold corresponds to a lactatemia of 4 mmol.l -1, the maximum value where the lactic acid produced by the muscle is metabolized.
3) The cardiac threshold is not constant. It corresponds to the stabilization of the heart rate at the end of the exercise.
Aerobic Capacity : Percentage of maximum aerobic power reached at the anaerobic threshold. It varies from 60 to 90% depending on the sports specialties.
Ventilation rate : Product of the tidal volume by the respiratory rate, it can reach 230 I.min-1 in sports such as rowing or Nordic skiing.
Respiratory quotient (RQ) : Ratio of carbon dioxide consumption to oxygen consumption. The RQ is 0.75 at rest, 1 at the anaerobic threshold and greater than 1.10 when the V 02 max is reached .
Lactatemia : Value of the concentration of lactic acid in the blood, expressed in mmol.l-1. At rest, the values are less than 1 mmol.l-1, approximately 4 mmol.l-1 at the anaerobic threshold, 8 to 10 mmol.l-1 at the maximum aerobic power and up to 25 mmol.l-1 Iors of a rowing regatta or a 400 meters .
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