What Limits Vo2 Max?

Vo2 max is the maximum capacity of an individuals body to use and transport oxygen during exercise. Vo2 stands for the maximum volume consumption of oxygen. To measure an individual’s vo2 max accurately the subject will undertake an athletic test usually on a treadmill or cycle ergometer, as the intensity of the workout increases the intake of oxygen and the concentration of carbon dioxide exhaled is monitored. The workload it gradually increased until there is a steady reading of both of these factors. This then shows the participants vo2 max level. However, an individual’s Vo2 max can be limited due to a mixture of different restrictions and developments within the individual. These limitations can also have independent and dependant variables, such as, age, race or fitness.

When researching into the limiting factors of the vo2 results two theories have been presented as the main limitations, the utilization theory and the presentation theory. The utilisation theory states that a lack of sufficient oxidative enzymes within the cell structure will limit how much oxygen is diffused and in turn affect the vo2 max scores. Oxidative enzymes are the enzymes which are the catalyst for the oxidisation reaction. Regular training can improve oxidative of the enzymes, which means an improved oxygen utilisation. This would create a better vo2 score as there is more oxygen being created.

The presentation theory does not support the idea of the utilisation theory limiting the vo2 max results but suggests that it is more to do with how effectively the oxygen is delivered around the body. As the persons heart rate rises and the volume of blood being circulated increases the demand for oxygenised blood also increases. These two theories can be seen as supply and demand.

A review of these two theories by Saltin and Rowell (1980) states that the utilisation (supply) theory is the more significant limiting factor. Studies show a relationship between an increase in oxidative enzymes and an increase in vo2 max results. One study by Costill DL, Thomas R, Robergs RA, Pascoe D, Lambert C, Barr S, Fink WJ (1991) measured the effects of a swim program on aerobic function. While oxidative enzymes were increased throughout the program, vo2 max increased until the last six weeks of the program

The state of health of cardiovascular, pulmonary and respiratory systems would be a major if not one of the main limitations of a vo2 max. The cardiovascular is compiled of the heart, blood and blood vessels it also includes the pulmonary circulation which is the movement of blood from the heart, to the lungs, and back to the heart again. The respiratory system includes the airways and lungs where a gas exchange happens due to the diffusion of oxygen and carbon dioxide. The health of all of these systems will influence the results of a vo2 max test. A typically bad cardiovascular system will worsen the scores of a vo2 max test, during exercise the heart rate responds by increasing, as does the demand in delivery of oxygen around the body, therefore, an unhealthy heart would be less able to transport as much oxygen into the body in comparison to a less healthy one. In addition to this if the connection between the lungs and heart is weak, the pulmonary circuit, it is likely to have the same response and trend in terms of the results of the vo2 max (Miller, Levine 2004). However it may not be the cardiovascular system with the problem, it could all come down to ones respiratory system, for example if an athlete has a small lung capacity they will not have the advantages of an athlete with a bigger lung capacity. Although it is all dependant on the lungs ability to diffuse the oxygen into the blood stream, as even though someone can have a smaller lung capacity if they diffuse ninety six per cent of the oxygen and the athlete with the greater lung capacity only diffuses fourth five per cent, the smaller lung capacity has actually overall got a higher vo2 max. This means it all comes down to the body’s ability to diffuse and transport oxygen around the body, the more it can transport the higher an athlete’s vo2 max is.

Another limitation could be the gender of the athlete. It is speculated that males will typically have higher maximum oxygen consumption in comparison to females. Research by Heywood, V (1998) shows that the average vo2 max for a typical untrained healthy male is approximately 35-40 ml/kg/min which mean millilitres of oxygen per kilogram of bodyweight per minute. However, a typical healthy female will only reach an approximate score of 27-31 ml/kg/min. these scores are of course only averages and the outcomes can differ due to variables in the group of participants. This could be something such as the age of the males or females used, as the scores will generally deteriorate at a certain age. Also, the general fitness of the group could also be a variable as a more athletic person would average better than a non-athlete. Therefore an elite performer would have excessively higher oxygen consumption then an untrained participant, Tim Noakes (2001) studied sports where endurance is an important component in an athlete’s performance, such as rowing, swimming and running. Noakes found that elite male runners can generate up to 85 ml/kg/min, and female elite runners can generate about 77ml/kg/min.

A person’s age would also play a part in influencing a vo2 test result. It can be said that the vo2 max decreases with age after a certain point of maturity. A large cross section study by Jackson , Beard , Wier, Ross , Stuteville and Blair (1995,1996) shows that the average decline of vo2 max is accepted as around one per cent each year or is better said as ten per cent each decade after the age of twenty five, this is when it said that most bodies start to deteriorate. The study shows that men’s vo2 max generally decreases at a slower rate than women’s with a 0.46 ml/kg/min (1.2%) for males and a decrease of 0.54 ml/kg/min (1.7%) for females. This would happen due to the aging process which causes many health problems. In accordance to vo2 max scores this would more likely respiratory and heart conditions which affect the vo2 max results.

The decrease in vo2 max levels, however, does not always come directly from the aging process but more the increases in body weight which in some cases happens as people get older. The vo2 max is also a reflection on the body mass of a person, so in effect as the body weight of a person increases the vo2 max generally worsens and deteriorates.

Training is an important part of an athlete’s life, Pollock (1973) found that aerobic training can on average increase vo2 max by fifteen to twenty per cent; this is if the athlete does a thirty minute aerobic training session at seventy five per cent of their aerobic ability three times a week for six months. However the result he got is only an average meaning that some people will respond better or worse it is all on the athlete’s ability on how high their vo2 max can go. Resistance training and intense anaerobic training have little or no effect on vo2 max readings, however improvements that did occur were only in participants that already had a low level of fitness (Kraemer, Deschenes , Fleck 1988). Resistance training alone does not improve vo2 max (Dudley, Fleck 1987). A considerable amount of training needs to be performed before an athlete can reach their maximum potential vo2 max, however when it is reached they do not have to train at the same intensity to maintain their optimum level (Hickson, Foster, Pollock, Galassi, Rich 1985).

Wilmore JH and Costill DL. (2005) states that altitude can also be a factor which can affect a person’s vo2 max scores. Test performed by this source shows that a person’s vo2 max results decreases as altitude increases above one thousand six hundred meters. For every one thousand meters that the person climbs above that, the athlete’s maximum oxygen intake decreases by a further approximate 8 to 11 per cent. The decrease is due to a reduction in the volume of blood plasma, which in turn decreases the heart rate and stroke volume. This is due to a decrease in the maximum cardiac output and therefore lowering the vo2 scores.

As proven vo2 max has a lot of limitations, firstly the utilisation and presentation theories are the two which are considered to be main limitations. It has been shown that there are many other factors that can influence the results of a vo2 max test such as age, gender, health and training. However, the research used in this paper is outdated and therefore cannot be considered to be one hundred per cent reliable to date.

 

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