Comparing Tests for Maximal Oxygen Consumption

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Maximal oxygen consumption (VO₂max) is an excellent indicator of a person’s physical fitness level. It can also be used for many other things including diagnostic tools for physicians. In this study, two different methods of collecting maximal oxygen uptake scores were compared. The first being the predicted VO₂max score attained via the Rockport test and the second being indirect calorimetry VO₂max score attained through cycle ergometer and an attached metabolic cart. Ten males and nine females of similar ages participated in both the Rockport and Indirect Calorimetry tests. It was found that the Rockport predicted tests significantly overestimated the VO₂max scores for males by 14% and females by 16% possibly due to the variability the test is subjected to. The Indirect Calorimetry was therefore deemed the more accurate test. It was also discovered that there were significant individual differences in the data due to many differing factors, including sex, body composition, heredity and physical prowess. Introduction:

Maximal oxygen consumption (VO₂max) refers to the maximum capacity of an individual body to transport and use oxygen during intense incremental exercise. VO₂max is achieved when the workload continues to increase but the oxygen uptake has halted and achieved a steady state or “plateau”. Achieveing a high VO₂max can be influenced by a multitude of intertwining physiological factors, including increased pulmonary, cardiovascular and neuromuscular functions, increased mitochondrial density and size, and increase capillary density reaching skeletal muscle [ (McArdle, Katch, & Katch, 2010) ]. Vo₂ max can be measured directly through several different methods. These include incremental tests to exhaustion using a treadmill, cycle ergometer, or rowing ergometer, collectively referred to as indirect calorimetry. Indirect calorimetry measures the amount of oxygen in the expired air. In this study a cycle ergometer was used alongside a metabolic cart to perform an all-out test with an incrementally increasing workload until reaching exhaustion. The metabolic cart uses the participants expired air to measure the volume, oxygen and gas concentrations within to provide a VO₂max score [ (McArdle, Katch, & Katch, 2010) ].

VO₂max can also be measured indirectly using predictive methods. These include many different submaximal tests including the Rockport test. The Rockport test predicts maximal oxygen uptake by evaluating the time taken to complete the walk, and the participant’s heart rate immediately following the walk, as well as their height, weight and age. This information can then be implemented into a formula and the VO₂max score can be calculated. It is predicted that both the predicted Rockport and the indirect calorimetry VO₂max test will produce similar maximal oxygen consumption scores for males and females. Purpose:

The purpose of this experiment was to compare the Rockport test (predicted value of VO₂max) to indirect calorimetry. Methods:
Rockport Test
Subjects embarked on a one mile walk for which they were instructed to walk as quickly as possible. At the end of the one mile the lab demonstrator was waiting with a stopwatch to record the time taken to complete the walk. After the test time was recorded, each subject recorded heart rate via pulse rate for one minute. Age, weight in kilograms and height in centimetres were taken from all participants. These values were then used for all participants to calculate a predicted VO₂max score. The equation used to calculate the predicted VO₂ max is as follows:

VO2max (ml/kg/min) = -0.062 x (weight in kg) – 0.286 x (age in years) – 1.5668 x (time for the mile walk in min) – 0.0969 x (heart rate in beats/min) + 87.6465 Males:
VO2max (ml/kg/min) = -0.093 x (weight in kg) – 0.388 x (age in years) – 1.7001 x (time for the mile walk in min) – 0.1311 x (heart rate in beats/min) + 109.6731 Indirect Calorimetry
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