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Predictive Maximal Oxygen Uptake Test sample essay

The aim of this study was to assess the validity, reliability and physiological underpinnings of an actual VO2max test in comparison to a predictive maximal oxygen uptake test. Eight male subjects with the following physical characteristics, mean and standard deviation age 19.75 ± 0.71 year; weight 72.15 ± 11.93 kg; height 1.77 ± 0.11 m performed an incremental treadmill test (53.24±7.15), starting at 8.km.h-1, increasing by 2.km.h-1 every 3 minutes with a constant increment of 1%. The subject’s heart rate, rating of perceived exhaustion and expired air were collected during the final 60seconds of each 3-minute stage.

A multi-stage fitness test (50.17±7.76) was also completed until volitional exhaustion. The subject’s heart rate was taken prior to each test and heart rate and blood lactate were taken post each test. Using a predictive equation (54.14±6.27) the athlete’s VO2max was also calculated. The conclusion of this investigation showed that the multi-stage fitness test under-predicted VO2max results and the predictive equation over-predicted VO2max results, though the multi-stage fitness test was the more relatively accurate form of measurement despite its disregard of body mass.

Literature review

There is a plethora literature that discusses the validity reliability and physiological foundations of a predictive Vo2 max testing some areas of which still huge amounts of discussion around (Basset and Howley,. 1997). Vo2 max is the maximal volume of oxygen can be obtained and utilized by the body each minute and is achieved when an athlete participates in an endurance exercise (Quinn,. 2011). It can also be described as Vo2 max is achieved when the work rate is increased, but oxygen consumption (Vo2) does not increase or has reached a plateau (Morcrow et al,. 2000). It is usually expressed in absolute terms as litres of oxygen per minute ( LO2min-1) or in relative terms as millimetres of oxygen per kilogram of body weight per minute (mlO2 kg-1 min-1). VO2 max in absolute terms does not take in to account body weight; a heavy person can be expected to use more oxygen than a lighter person per minute. Doing this places everyone on a scale relative to body weight therefore making the tests for maximal oxygen testing reliable (Fleck and Kraemer,. 1997).

When the intensity of the exercise increases oxygen consumption also increases in an exact proportion until a point is reached when it fails to rise despite the increased workload. VO2max is an important variable that sets the upper limit for endurance performance an athlete cannot operate above 100% VO2max, for extended periods (Basset and Howley,. 2000). Aerobic capacity, maximal oxygen uptake or VO2 max is regarded by most as the best single measurement of cardiorespiratory endurance and aerobic fitness. This is because it represents aerobic power and is seen as the best objective laboratory measure of cardiorespiratory endurance capacity (Wilmore et al,. 2008). Studies show that the more oxygen you use during high levels of exercise the more ATP can be produced. This is often the way elite athletes provide a rough guide for high levels of athletic performance (Jones,. 2007).

However there are people that disagree for instance Hayward (2002) states that because maximal exercise involves both aerobic and anaerobic components, the VO2 max will be overestimated since the contribution of the anaerobic component is not known . Testing for Vo2 max is an essential way of providing important information about the physical capacity of the cardiovascular, pulmonary and neuromuscular systems of an athlete (Jones and Poole, 2005). There is a lot of debate surrounding why maximal oxygen uptake eventually fails to rise once VO2 max is achieved. This debate is referred to by Basset and Howley as “Classical” verses “Contemporary” viewpoints. In their journal article they critically analyse. They discuss the two theories surrounding the “VO2 plateau”, theorises in 1920 by A.V. Hill. He proposed that there is an upper limit to oxygen uptake , that there are inter-individual differences in this variable, and that VO2max is limited by the circulatory and/or respiratory systems.

They demonstrated that oxygen uptake increases linearly with running speed, but in some subjects it eventually “reaches a maximum beyond which no effort can drive it,” a phenomenon now referred to as the VO2 plateau However recently this theory has been questioned by Timothy Noakes and his colleagues, on the bases that that the absence of a VO2 plateau in some subjects is proof that oxygen delivery is not a limiting factor for VO2max. This view fails to recognize that the plateau is not the principal evidence for a cardiorespiratory limitation, Basset and Howley, did conclude that the classical Vo2 max paradigm of A. V. Hill is the correct theory (Basset and Howley,. 1997). Despite consistent research on this concept (the plateau effect), it is common for participates to complete a maximal exercise test and still fail to demonstrate a plateau in VO2 (Castle,. 2011). For this reason criteria have been used by scientists to characterise the oxygen uptake measured.

BASES (1997) suggested additional criteria to assess whether Vo2max had been achieved: (a) collecting blood lactate concentration 4-5 minutes after exercise, (b) a final heart rate within 10beats.min-1 of the age predicted maximum, (c) receiving a final RER value of 1.15 or above, (d) perceived exhaustion – 19-20 on the Borg RPE Scale, or finally (e) subjective fatigue and volitional exhaustion (Howley et al,. 1995). Blood lactate concentrations are typically found to be significantly higher than resting values at work rates of 55-70% VO2 max, this means it is a good indicator of maximal effort (Spurway and Jones, 2007).The lactate thresholds and critical power measurements have generally been used to predict performance in endurance events lasting longer than 20 minutes but are associated (Powers and Howley, 2009). It is believed that athletes that score 8mmol.L-1 4-5 minutes after exercise have achieved Vo2 max. However there is also literature that suggests this varies from individual to individual. RER (respiratory exchange ratio) values are also a method of assessing Vo2 max.

The respiratory exchange ratio (RER) is simply the ratio between the carbon dioxide production and the oxygen consumption. This value is a ratio and thus does not have a unit. The RER is calculated before any unit’s conversion, weight normalization, or effective mass correction. RER is the ratio of the volume of carbon dioxide you exhale versus the volume of oxygen you consume at a given exercise intensity. A lower RER means that you are consuming more oxygen relative to carbon dioxide released and thereby breaking down more fats (a nearly unlimited fuel source) rather than carbohydrates (a limited fuel source). As exercise intensity increases, your body must rely more and more on carbohydrates as a fuel source. An RER over 1.00 means you are burning primarily carbohydrates. Lactate (LT) typically corresponds with RER of 1.0. With endurance training, you would expect your RER value at a given intensity to come down as your body improves its ability to utilize fat as a fuel source, thereby saving limited glycogen (carbohydrate) stores (Poole et al,. 2007).

Reliability and validity is of paramount importance when undertaking physiological research. If a measure is reliable, the test scores for each subject should be relatively the same over repeated measurements making the outcomes consistent therefore providing quality research (Brandon et al,. 2012). Validity refers to whether a study measures or examines what it claims to measure or examine, in this studies case validly would require no false data had been inserted to help the interests of the assessor (Vaughn and Daniel,. 2012 ). To this end it is important that appropriate tests were selected. The traditional treadmill test using the Douglas bag method is perceived as gold standard in techniques most suited to determining a steady state gas exchange, of course this is due to its reliability and validity (James et al,. 2007).

It is widely recognised that laboratory experiments of Vo2max are the most valid physiological indicators of a subject’s cardiovascular function (Cooper et al., 2005). To make sure that this test is valid and reliable and the equipment is not effected certain factors need to be taken in to account such as temperature and humidity. The Multi- stage fitness test (MSFT) was developed as a convenient and inexpensive maximal field test to predict VO2 max. This test aims to provide a continuous incremental exercise until exhaustion.

There is a wealth of literature on the reliability and validity of this test and it is regarded as a pretty efficient assessment of VO2 max testing (Legar and Lambert,.1982). There are different methods for predicting the Vo2 of a particular person without carrying out exercises tests, but instead through analyses of personal characteristics. Attributes such as age will directly affect the capability of cardiorespiratory fitness, hence their existence in the equation formed. An equation is completely reliable as the foundations are set for every subject. If then found to represent actual tested scores the validity of the equation is apparent.

Methods

The experiment protocol was approved by the ethics committee of The University of Durham and all subjects gave their expressed written consent and completed a medical questionnaire prior to their participation within the study. Subjects were required to take part in two different tests then provide a blood sample 5 minutes prior to testing. Before the tests began basic information was taken 1st from the subjects such as height (cm) mass (Kg) and age (years). And then information was taken from the lab itself these included Temperature (oC), Humidity (%) and the Pbar (mmhg). Polar accurex heart rate monitors (OY, Finland) were attached to each subject while at rest. Blood lactate was taken approximately 5-minutes after both tests (lactate pro – Arkray, Japan).

Maximal Test of Volitional Fatigue

Subjects were told to run on a treadmill until they could no longer carry on running. Before the test started the subject was allowed 5 minutes of jogging and stretching to prepare. The test began at workload of 8∙km∙h⁻1 for 3 minutes then the intensity was increased by 2∙km∙h⁻1. During the last minute of each of the 3 minute stage the expired air was collected in to Douglas bags and the rating of perceived exertion from the RPE scale was recorded.

All subjects were kept under close observation in case they showed any signs of over exertion that may have given cause for concern. Subjects were also provided with encouragement in order to motive them to achieve a good maximal measure. The subjects were given 5 minutes to recover after they finished running and blood samples were taken to measure their lactate levels. Whilst this was happening all air was extracted from the Douglas Bags using a dry gas meter (Harvard Apparatus, UK) minimising any ambiguity among results. The subject took a moment to become accustomed with equipment.

Multistage Fitness Test (MSFT)

The MSFT was conducted on a 3G rubber crumb Astro turf with a box of cones set 20×20 metres apart to give the individuals enough room to run in sets of four, this was made deliberately in order to create an element of competition encouraging subjects to work maximally. The individual was asked to complete a series of shuttle runs between the two parallel lines in accordance with an audible bleep. The tape dictated that subjects started running at an initial running velocity of 8.5 km/hrs. (2.36 ms-1), which increases by 0.5 km/hr (0.14 ms-1) (Léger and Lambert, 1982). The increased running speed represents the increased intensity.

The test stops when the subject gives up or they fail to maintain running speed or in other words reach the line before the beep. Subjects are given two verbal warnings too hit the line but on their third miss they are asked to forfeit the test. The subjects results are recorded as the number of levels they have completed (e.g. level10.7or 13.2). You then use the table to convert this into their aerobic capacity. Predictive Equation

This equation was used to predict maximal oxygen uptake:
Predicted Vo2max (ml.kg.min-1) =
(0.133 x Age) – (0.005 x Age2) + (11.403 x Gender) + (1.463 x PA-R Score) + (9.17 x Height (m)– (0.254 x Body Mass) + 34.142 Table 1: Physical characteristics of subjects (mean ± standard deviation) | All Subjects (N=8)|

Age (Yr)| 19.75± 0.71|
Heght (m)| 1.77± 0.11|
Mass (kg)| 72.15± 11.93|
Gender | All males |

Results

The mean and standard deviation have been calculated in order to make it easier to understand the results.

Figure 1: See that this graph displays the comparisons between VO2 max results attained from the three tests. It also shows each method for collecting the maximal oxygen uptake scores. It shows that the scores deviate from each other quite obviously. The predicative equation is the highest value and MSFT being the lowest value. There is a greater difference in VO2max between the treadmill and MSF tests. Predictive equation has the highest mean results whilst MSFT has the lowest however it does have the highest SD values and predicative has the lowest.

Figure 2: This bar chart shows the mean and standard deviation between maximum heart rate recorded when both incremental treadmill test and the MSFT. You can see that there is a higher maximum heart rate for the treadmill test. You can also see that there is a significant difference in the SD for MSFT from the size of the error bars.

Figure 3: This chart shows the mean and standard deviation values for blood lactate after each physiological test. Higher blood lactate scores were seen for the MSFT. Both tests proved to get there subjects blood lactate scores above 8mmols. The error bars are also further apart for MSFT.

Discussion

In this study an effort was made to question the reliability and validity the foundations of two physiological tests against that of a predictive equation for maximal oxygen uptake assessments. There were a number of key findings in Léger LA and Lambert J research they concluded that the 20-m shuttle run test is valid and reliable test for the prediction of the VO2 max of male and female adults, individually or in groups, on most gymnasium surfaces however does consistently underestimates Vo2 max when compared to Incremental treadmill tests. This is backed up in figure 1, where MSFT has the lower values than the treadmill test. Limitations to this study may include contradictions to the validity of the study when research from Hayward (2002) states that tests that require subjects to perform there maximal capacity involve both aerobic and anaerobic components, the VO2 max will be overestimated since the contribution of the anaerobic component is not know because of this the validity of the test making it void.

Studies show that taking blood lactate after or during treadmill or MSFT are both valid ways of measuring VO2 max. Secondly in figure 2 Shows that there is a greater distribution in SD for heart rate for the multi stage fitness test than for the Lab based test and in most cases the participants didn’t meet the requires amount for VO2 max (±10bpm from maxHR). This could suggest that VO2 max for this test was not achieved; this of course makes validity an issue for this test. However just because one criteria for VO2 max was not met doesn’t mean it wasn’t achieved. Furthermore In figure 3 it is clear to see that all subjects achieved8mmol.L-1 of blood lactate indicating that all subjects achieved VO2 max.

However the multistage fitness test shows higher lactate values than the laboratory tests. There is literature to suggest that this is not an unusual phenomenon, this is because of the nature of the test. Due to the turning and changes of acceleration it requires more fast twitch muscle fibres force the body to work anaerobically creating a higher blood lactate. To conclude laboratory-based VO2max testing is the most valid and reliable form of VO2 measurement however due to finance and equipment requirements, is often not feasible. Therefore, in conclusion, and following analysis of the study and the results produced, it is recommended that the MSFT is used as an appropriate field-based method of measurement due to its accessibility, reasonable validity and practicality.

References
Andrew M. Jones . (2007). Middle- and long Distance Running . In: Edward M. Winter, Andrew M. Jones, R.C. Richard Davison, Paul D.Bromley, Tom H. Mercer Sport and exercise physiology testing Guidelines . Cornwall: Bases . 147- 154. Australian Sports Commission (2000). Physiological Tests for elite Athletes . Leeds: Human Kinetics . 114. Bassett DR Jr, Howley ET. (2000). Limiting factors for maximum oxygen uptake and determinants of endurance performance.. medicine and science in sport exercise . 1 (32), 70-84. Bassett DR Jr, Howley ET. (1997). Maximal oxygen uptake: “classical” versus “contemporary” viewpoints.. medicine and science in sport exercise . 1 (5), 591- 603 . Brandon Vaughn, Hwa-Young Lee, Akihito Kamata. (2012). Reliability . In: Gershon Tenenbaum, Robert C. Eklund, Akihito Kamata Measurement in sport and exercise psychology. Leeds : Human Kinetics . 25-32. Brandon K.Vaughn, Sarah R. Daniel . (2012). Validity . In: Gershon Tenenbaum, Robert C. Eklund, Akihito Kamata Measurement in sport and exercise psychology. Leeds : Human Kinetics . 33-39. Cooper, S-M., Baker, J. S., Tong, R. J., Roberts, E. and Hanford, M. (2005). The repeatability and criterion related validity of the 20m multistage fitness test as a predictor of maximal oxygen uptake in active young men, British Journal of Sports Medicine, 39, (4), 1 -7. David C. Poole, Daryl P. Wilkerson, Andrew M. Jones. (2007). Validity of criteria for establishing maximal O2 uptake during ramp exercise tests. European Journal of Applied Physiology. 112 (203), 403-410. David V.B. James, Leigh E. Sandals, Dan M. wood and Andrew M. Jones . (2007). Pulmonary Gas Exchange . Sport and Exercise Physiology Testing Guidelines . 2 (11), 101-111. Edward T. Howley, David R. Bassett JR., and Hugh G.Welch . (1995). Criteria for maximal oxygen uptake: review and commentary. Exercise Science . 27 (9), 1292- 1301 Elizabeth Quinn. (2011). What Is VO2 Max?. Available: http://sportsmedicine.about.com/od/anatomyandphysiology/a/VO2_max.htm. Last accessed 22nd nov 2012. James R. Morrow, Jr, Allen W. Jackson, James G.
Disch and Dale P.Mood (2000). Measurment and Evaluation in human performance . 2nd ed. Leeds : Human Kinetics . 228. Steven J. Fleck, William J. Kraemer . (1997). Muscle Physiology . In: Rick Frey, Scott Wikgren, Krisine Enderle Designing resistance training programs. 2nd ed. Leeds : Human Kinetics . 55-56 Howley, E. T., Bassett, D. R. and Welch, H. G. (1995). Criterion for maximal oxygen uptake: review and commentary, Medicine and Science in Sport and Exercise, 27, (9), 1292-1301. Jack H.Wilmore David L.Costill W. Larry Kenney (2008). Physiology of sport and Exercise . 4th ed. Leeds : Human Kinetics . 108-109. Jones, A. M. and Poole, D. C. (2005). Introduction to oxygen uptake kinetics and historical development of the discipline In: A. M. Jones and D. C. Poole (Ed.) Oxygen Uptake Kinetics in Sport, Exercise and Medicine. London: Routledge. Chapter 1, pp. 1-37. Léger, L.A. and Lambert, J., 1982, ‘A maximal multistage 20m shuttle run test to predict VO2max’, European Journal of Applied Physiology, Vol 49, p1-5. Léger LA, Lambert J.. (1982). A maximal multistage 20-m shuttle run test to predict VO2 max.. European journal of applied physiology and occupational physiology. 49 (1), 1-12. Neil Spurway and Andrew M. Jones (2007). Sport and Exercise Physiology Testing Guidlines . Oxton: Routledge. 113-118. Scott K. Powers and Edward T. Howley (2009). Exercise Physioogy: Theory and Application to Fitness and Performance . 7th ed. New York: Mc Graw Hill, Higher Education . 435-437. Richard Vincent Castle. (2011). Why is there still so much confusion about VO2. A re-examination of the work of A.V. Hill. 1 (1), 31-36. Vivian H. Hayward (2002). Advanced fitness assessment and exercise prescription . 4th ed. Leeds : Human Kinetics . 56-57.

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