Exercise Testing Protocols Essay Example Paper

Published: 2021-09-02 04:00:13
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Exercise Testing Protocols Essay Introduction
Different exercise protocols prompt different physiological mechanisms before VO2max. This investigation aims to analyse and compare four different tests, both constant load and incremental, in order to determine the most valid and accurate for assessing VO2max. Ten subjects completed four different maximal VO2max tests over a four-week period, with various physiological variables being recorded immediately prior to volitional exhaustion (VO2, RER, lactate and HR).Mean scores for each variable for each test were compared to conclude that in contradiction to current literature, the incremental treadmill test did not elicit the highest VO2, but the incremental cycle ergometer test. Exercise economy and lactate build up were two variables having major implications upon the validity of the four protocols. It is probable that none of the four tests presented a totally accurate VO2max. Several flaws were noted in the data collection procedure and extension studies should be used to support the conclusions drawn.Introduction This investigation involves the comparison of four different exercise tests and their validation in providing quantitative results of VO2max. The tests involved are the: ‘constant load cycle-ergometer test’; ‘incremental cycle-ergometer test; multi-stage fitness test and the incremental treadmill test. These tests are all very common in clinical and field fitness testing, therefore the conclusions drawn from this investigation will have direct, practical implications and applications to ‘real world’ sport.During periods of exercise Hill and Lupton (1923) noted that subjects require additional oxygen to compensate for the additional ATP production and hydrolysis, in relation to rest. They also noted that a plateau occurs in the rate of oxygen consumption (VO2) even though exercise intensity increases, leading them to the assumption that there is a maximal rate of oxygen consumption and utilisation, or VO2max. Hill and Lupton (1924) concluded that circulatory and pulmonary systems being unable to provide sufficient O2 to mitochondria caused VO2max.Later work by Saltin and Strange (1992) supports this view. During regular exercise it is improbable that VO2max will be achieved and so the highest rate of O2 consumption recorded during exercise is known as VO2peak. More contemporary research by Tim Noakes (1996) contradicts Hill and Lupton’s (1923) theory. He claims that a plateau in VO2 does not always occur, and so he believes a linear relationship between exercise intensity and VO2 is more accurate. Noakes would argue that muscular/peripheral factors are to blame for any incidents of plateau, and that VO2 is not limited.He believes the functions of muscles simply prevent VO2 from increasing further, and therefore VO2max does not exist. The discrediting of Hill and Lupton’s work by Noakes is based upon the view that Hill only demonstrated experiments that illustrated a plateau and that he did not supply enough experimental evidence to support the theory of the VO2 plateau. The debate between the causes of VO2max as being central/circulatory or peripheral/muscular is generally weighted towards the ‘central’ argument.According to Wagner (1992), the O2 supply to mitochondria is dependent upon the diffusion gradient, and with Honig et al (1992) proving that the surface area of mitochondria is five hundred times that of the capillaries, the diffusion gradient supports Hill and Lupton’s theory of circulatory limits to VO2. The more recent beliefs of Noakes are widely criticised by many existing physiologists who claim that Noakes based his ideas on the work of Myers et al (1990) who said that only thirty three percent of subjects showed a plateau when tested, and that Myers et al only used six subjects, and so it is in fact Noakes’ work that is unsupported.Froelicher et al (1974) have conducted studies showing variable percentages of subjects actually eliciting a VO2 plateau during exercise, which would support Myers et al (1990). Froelicher et al however, attributed the variances to the protocols used, rather than the inexistence of VO2max, contradicting Myers et al, and moreover, Noakes. Noakes used the absence of a plateau in many cases to promote the idea that VO2 is not limited and would continue to increase with exercise intensity if muscular function did not prevent subjects from continued exercise.Rowell (1986) provides evidence to discredit Noakes by claiming that a plateau is not the only determinant of VO2max, and that Noakes has neglected other physiological indicators that would suggest a maximal VO2. BASES (1997) published a criterion to act as a ‘checklist’ to aid physiologists in the identification of VO2max. The criterion comprises of: a plateau in VO2; a final respiratory exchange ratio (RER) > 1. 15; a final heart rate within 10bpm of predicted maximum; post-exercise blood lactate concentration > 8mmol/l; subject fatigue or volitional exhaustion and finally a perceived exertion rating of 19 or greater on a 6-20 Borg Scale.VO2max is often regarded as the most important aspect of fitness due to its benefit to such a wide variety of sports and exercises. Demarie et al (2000) stated that the percentage of VO2max maintained during training is linked to the rate at which physiological adaptations occur. Therefore, the accurate calculation of maximal oxygen uptake is essential for the applied use of designing the most effective training programme to benefit individual athletes.There are many different tests employed by exercise physiologists, sports coaches and physical trainers to assess VO2max in athletes, but as earlier references to the work of Froelicher et al (1974) illustrates, the protocol for testing VO2max can often influence the results obtained, and whether VO2max or VO2peak is represented. Therefore it is essential that valid and accurate tests be used when assessing VO2max, if the results are to have any reliable and practical function or relevance. This investigation involves the comparison of four exercise tests, each designed to provide accurate VO2max values.The comparison is of validity and therefore, by definition, do the results obtained actually reflect VO2max or are they influenced by physiological responses at high intensity exercise. Research into the physiological demands of these tests and into previous studies involving these tests, is therefore, quite pertinent to this study. Although all tests used in this investigation have the same objective, there are two types of test employed, incremental and constant load, and for each there are different strengths and weaknesses in terms of validity.Incremental tests, according to Kuipers et al (2003), have a weakness in that stage duration can influence the results. Long stage duration can lead to premature fatigue and volitional exhaustion before VO2max (Crouter et al (2001), therefore, results show VO2peak and are invalid. However Kuipers et al (2003) also say that stage durations between one and six minutes do not influence VO2 plateau and so the tests in this investigation, all of which remain in this time frame, should be immune to such influences.The notion of differences in VO2max values elicited by different tests, is confirmed by Basset and Boulay (2003), who proved that incremental treadmill tests provide significantly higher values than incremental cycle-ergometer tests. Suggesting that cycle-ergometer tests do not accurately reflect VO2max, but reflect VO2peak, hence there could be debate over the validity of VO2max values obtained from them. Kirchoff and Sill (1967) compliment these thoughts with studies providing similar results. Crouter et al’s (2001) research on premature fatigue could explain this trend.The demands of cycle-ergometer tests are focused entirely on the legs and so lactate build up is concentrated there, hence fatigue of the legs may precede VO2max. Hawley et al (1992) claimed that in their study involving cycle-ergometer tests, 63% of subjects did not reach VO2 plateau due to premature fatigue and volitional exhaustion, caused by acidosis in the legs. Premature volitional exhaustion could also be an invalidating factor of the MSFT, proposed by Leger and Lambert (1982) and developed by Ramsbottom et al (1988).This test comprises of 20m shuttle runs being completed at a gradually increasing pace, set by an audiotape. Several shuttles are completed before a verbal cue from the tape alerts subjects of progression to an increased intensity stage of several more shuttles. With verbal cues preceding the next increment, it has been recognised that subjects do not run until absolute exhaustion, instead many discontinue at a pre-determined target or at the end of a level to avoid the next increment (Wilkinson et al 1998).If such behaviour should lead to sub-optimal performance, then VO2max values translated from the test are not truthful and therefore invalid. This is a predictive VO2max test, which by definition introduces some doubt to the reliability of the test, coupled with sub-optimal performance, the results become unreliable. Another variable of the tests that could influence the value of VO2max obtained is exercise economy (Costill et al 1971).During treadmill exercise, Pokan et al (1995) noticed that mechanical or neuromuscular constraints led to the flattening of tidal volume and maximal pulmonary ventilation as a result of exercise economy. The MSFT will probably be the most affected by exercise economy variances because the ergometers used in the other tests somewhat inhibit inter-subject economy variances, enhancing reliability. This investigation will provide an in-depth discussion into the validity of four VO2max tests.There is ongoing debate in exercise physiological circles into the exact causes of VO2max and the results from this investigation could provide support for the arguments proposed by Hill (1923) or those by Noakes (1995). This study could possibly have an indirect influence on the conclusion of this debate. More practical applications of this test relate to the development of fitness-programmes, which can be dependent upon accurate fitness testing methods. More accurate programmes designed from this research could lead to advancements in the fitness of individual athletes and therefore athletic performance.
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