Cardiorespiratory Fitness

Maximal oxygen uptake can be defined as the amount of 02 that a person can extract from the atmosphere and then transport and use in tissues (Kent 2006). McArdle et al (2006) explains that V02 max represents the greatest amount of oxygen a person can use to produce ATP aerobically during endurance or high intensity exercise. Therefore it is a measure of aerobic energy production. V02 max provides useful information about long-term energy system capacity, representing a fundamental measure in exercise physiology and serves as a standard to compare performance estimates of aerobic capacity and endurance fitness (McArdle et al, 2006).

Maximal oxygen consumption is dependent on the oxygen transport systems ability to deliver blood and capacity of cells to take up and utilise oxygen in energy expenditure, (Noonan and Dean, 2002). Powers and Howley (2003) illustrate that V02 max is closely linked to the functional capacity of the cardiovascular system to deliver blood to the working muscle during maximal and submaximal workloads. ACSM (2005) state that Maximal oxygen uptake (V02 max) is accepted as the standard measure of Cardiorespiratory Fitness.

ACSM (2005) explain that across a population V02 fitness levels significantly vary forming differences in maximal cardiac output, therefore explaining that V02 max is closely related to the functionality of the heart. Furthermore Jonathan and Timmis (2002) clarify that exercise testing is the greatest diagnostic value in patients with immediate risk of coronary artery disease. Therefore Mitchell et al (1957) conclude that the test may be of enormous value when in the critical evaluation of normal and abnormal cardiovascular function.

Typically V02 max provides appropriate information to participants in fitness programs, (Powers and Howley 2003) ACSM (2006) illustrate that when direct measurement of V02 max is not feasible, submaximal and maximal exercise tests can be used to estimate V02 max. ACSM (2006) describe the correlation between directly measuring V02 max and the V02 max estimated from physiological responses to submaximal exercise. Meir and Girbson (2004) demonstrate that submaximal and maximal tests are used to predict V02 max from a standardised protocol.

Powers and Howley (2003) additionally state that V02 max can be extrapolated from subject’s age predicted heart rate from submaximal tests. Powers and Howley (2003) explain that one the most common approaches used in estimating V02 max is to take the final stage in the test and apply the formula for converting grade and speed to V02 in ml. kg-1. The basis of a submaximal exercise testing is to determine the heart rate response to one or more submaximal work rate and then use the results to predict V02 max.

However, submaximal tests are based on the linear relationship between heat rate and work rate and that maximal work load is indicative to maximal V02. Noonan and Dean (2000) evaluate that although maximum exercising is considered the gold standard for testing maximal aerobic activity performance may be limited to fatigue of muscle and pain therefore contradicting the test. Submaximal testing overcomes some of the limitations that maximal exercise testing offers. McArdle et al (2006) suggest that there are various criteria to achieve V02 max. They suggest that blood lactate levels that reach 8 to 10 mmol.

litre show significant maximal exercise effort. Also once near age predicted maximum heart rates suggest that subject has reached close maximum intensity. Robergs and Landwehr (2002) confirm that age predicted heart rate (220-Age) provides a prediction of V02 max. Meir (2004) suggests that HRmax should be greater than or equal to age predicted maximal value. Powers and Howley (2003) explain that the main criterion for achieving V02 max is the levelling off of the V02 (0. 103. This shows that the null hypothesis that submaximal tests cannot be a valid predictor of maximal V02.

The relationship between the V02 max predicted was greater than observed V02 max with a mean difference of 13. 42 ± 6. 09 l/kg/min-1. There were no differences between sedentary and active subjects. Figure 2 shows submaximal VO2 max and maximal VO2 correlation, although the graph is a linear correlation, there were two anomalies which do not correlate the graph. Subject 1 and subject 5 showed no linear correlation. Fig 2) A comparison between Submaximal predictor of V02 max and Maximal observation of V02 max. Discussion:

From the results we can see that the Bruce treadmill protocol for predicting V02 max was overestimated. The results showed that there was no significance p;0. 103, therefore showing that in this particular study there was no correlation between submaximal predicted V02 and maximal observed V02. There are several errors within this protocol. Powers and Howley (2003) illustrate the errors within estimation of V02 max, explaining that standard errors occur within the equation to work out V02 max. Meir and Gibson (2004) explain that the metabolic equation for working out predicted V02max is based on steady state measures.

Therefore they suggest that if used to calculate V02 max from a maximal exercise stage V02 will be over estimated. Meir and Gibson (2004) explain this may be largely due to the unaccounted contribution of aerobic energy to the maximal work load. Therefore this suggests that there is a significant error in using the prediction formula formulated by Bruce 1971. Noonan and Dean (2000) evaluate that although maximum exercising is considered the gold standard for testing maximal aerobic activity performance may be limited to fatigue of muscle and pain therefore contradicting the test.

Meir and Gibson (2004) explain that when a protocol relies on 85% of the age-predicted HRmax as a main criterion may carry significant individual variability. Meir and Gibson (2004) therefore explain that in younger individuals the equation to predict Age predicted HRmax= 220-Age is overestimated. Power and Howley (2003) explain that for some individuals a submaximal end point of 85% can be maximal work for some and for others very light work. As estimated HR max = 220-age may be higher than as some people may have an actual low heart rate.

However there are other error which may have been introduced as Heart rate can be affected by various factors such as body temperature, hydration state, anxiety and stress, (Meir and Gibson 2004). Astrand et al (2003) also explains that excitement, related emotional stress can markedly elevate heart rate at a submaximal work rate without affecting maximal work loads. Astrand et al (2003) suggests that a disadvantage with protocol is that the subject is hampered by the equipment whilst the test is running. Powers and Howley (2003) suggest that the treadmill protocols accommodate everyone to elite to sedentary.

However, there maybe some limitations in the measurements attained whilst running or walking with the Douglas bag whilst testing for V02. (Powers and Howley, 2003). However, Astrand et al (2003) explained that the Douglas bag, to measure expired air is theoretically sound. Astrand et al (2003) illustrates that at low intensities those who tend to run will have a higher energy cost than those walking at that same intensity. Therefore the energy demand will be different. McArdle et al (2006) explains that subjects may terminate the test for a variety of reasons, exhaustion, psychological and motivational factors can influence this decision.

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