Estimation of Cardiorespiratory Fitness6



  1. Participants of this study were involved in the estimation of aerobic capacity estimation. Direct and indirect methods are employed to estimate the aerobic capacity of 175 participants (males). Direct measurement, Jackson’s equation, and Åstrand-Rhyming Cycle Test were studied, and the correlation between the three was determined. From the results, both Jackson’s equation and Åstrand-Rhyming Cycle Test had positive significant correlation with the direct measure of VO2 max. The correlation coefficients of Jackson’s equation and Åstrand-Rhyming Cycle Test were estimated to be around 0.49, 0.52 and 0.55 respectively. Hence ,three methods can be used in the estimation of VO2 max. Jackson’s equation had a stronger relationship with the measured VO2 max. Physical activity was expected to increase cardiorespiratory fitness while the increase in BMI and age were found to result in reduced aerobic capacity. The results are used to answer the following How do the three methods of estimating aerobic capacity compare?, How is the validity of the data collected affected? and What is the relationship between age and aerobic capacity?.


Cardiorespiratoryfitness is described as the efficiency and ability of thecardiovascular system (heart, vessels and lungs) to perform theirfunction, that is, supply muscles tissues with oxygen and nutrientsthrough blood circulation. Healthy cardiorespiratory fitness ensuresthat the body muscles and cells receive required nutrients and oxygenwith minimum delay, hence increasing the metabolic activities. It isconcerned with the maximum uptake of oxygen in the body. When theheart raises the amount of blood it pumps in every single beat, theblood supplies to muscle tissues increases. It is important formaintaining fitness and help in the prevention of complications suchas congestive heart failure, heart attack, coronary artery andatherosclerosis. Therefore, various physiological processes in thebody are boosted because they get adequate and reliable nutrients andoxygen supply hence the sensitivity and the response of the bodytowards various internal and external changes becomes more efficient.Thus, an individual gains the capability of responding effectively toemergencies. Furthermore, the heart will be in a position to supportintensive physical activities (Greenberg, J. S. Et Al. 2004Giles-Brown, L. 2006, 87).

This experimentis focused on the methods of estimating cardiorespiratory fitness. Inorder to determine and individuals’ cardiorespiratory fitness(aerobic capacity), maximum oxygen uptake (VO2 peak) iscalculated. MAUD, P. J., &amp FOSTER, C. (2006) defines maximumoxygen uptake as the maximum point of oxygen consumption beyond whichis associated with no or slight increase when the work rate isincreased. Therefore, VO2 max shows the capability of anindividual to get oxygen supply oxygen as well as its utilization bythe muscles during physical exercise. Oxygen uptake is proportionalto the amount of workload associated with physical exercise andindividual undertakes. VO2 max is used to analyze themaximum capability of the human body to supply and utilize oxygen aswell as its associated ability to support prolonged physicalactivity. The measurement of VO2 max can be done throughdirect and indirect methods.

Comment Directmeasurement, Jackson’s equation, and Åstrand-Rhyming Cycle Test

Directmeasurement of VO2 max is the most accurate method henceis used as gold standard for VO2 max measurement.Equipment such as treadmill is used in this measurement as thesubject is instructed to run on the treadmill while the work load isconstantly increased until there is no increase in oxygen uptake.Direct VO2 max measurement requires expensive equipment,trained supervision, controlled conditions and high motivation of thesubjects. These are the disadvantages that have discouraged use ofdirect methods (KOLKHORST, F. W., &amp BUONO, M. J. 2004).

Indirect methodsof measuring VO2 max were developed in order to overcome thedisadvantages associated with direct methods. Indirect predictions ofVO2 max have been made possible by: linear correlation ofoxygen uptake with work load and linear relationship between oxygenuptake and heart rate. Two indirect measurement methods have beendeveloped submaximal exercise testing and non-exercise testing.Submaximal exercise testing is considered the best estimationtechnique as it is safe to any individual regardless of their age,health status or disabilities (MACKINNON, L. T. 2003). Estimation ofVO2 max by submaximal exercise testing is facilitated by

  1. Linear relationship between heart rate, oxygen uptake and workload

  2. Constant mechanical efficiency among various individuals

  3. Similar maximum heart rate of all subjects of a particular age

Åstrand-Rhyming Cycle Test is submaximal exercise test method usedin the estimation of CRF. Åstrand-Rhyming Cycle Test bases on theresponse of heart rate to submaximal work. This method exposes thesubjects to reduced health risks.

The Jacksonequation is used in non-exercise testing and it involves the use ofcalculations that bases on self-reported characteristics of theparticipants in estimating VO2 max. There is no physicalactivity needed in this method. Questionnaire on the physicalactivity rating (PA-R) questions are given to the participants thatenable them to provide self-report of physical activity. Thequestionnaire score and variables such as age, gender, BMI and heightare used to calculate VO2 max (MACKINNON, L. T. 2003).

This experimentwas done to study and compare the three methods of estimatingcardiorespiratory fitness as well as how cardiorespiratory fitness isaffected by age and BMI of an individual.


  1. How do the three methods of estimating aerobic capacity compare?

  2. How is the validity of the data collected affected?

  3. What is the influence of BMI and physical activity on aerobic capacity?

  4. What is the relationship between age and aerobic capacity?

  5. How can the limitations of the experiment be addressed in order to improve the validly of data collected?


About 175 malesof various ages ranging from 19 to 41 were involved in theexperiment. The characteristics of the participants are presented inthe following table.

Participant characteristic









Systolic BP(mmHg)

Diastolic BP (mmHg)

standard deviation














DirectMeasure of VO2 max

Before the test,the individuals were given Physical Activity Readiness Questionnaireso as to make sure that they have no medical situations that exposethem to medical risks during this test. They were then subjected to 5minutes warm up followed by a run on the treadmill at a constantspeed. The treadmill was subjected to a constant incremental speedevery minute until the participants reached their exhaustion(Kaminsky, L. A. 2014, 36). The expired gas was collected in orderto determine its oxygen and carbon (IV) oxide content. Fick equationbelow was then employed to calculate VO2 max.

VO2max = MaxQ x (a-vO2 diff)

Where: Q (cardiacoutput)= Heart rate (HR) x Stroke Volume (SV)

(a-vO2 diff) is the difference between arterial oxygen content andvenous oxygen content.

Åstrand-RhymingCycle Test

This is anexercise testing method that involves the individual cycling atvarious work rates and their respective heart rates recorded. Theresources required for this method include the cycle ergometer, heartrate monitor, weighing scales and stopwatch. At the beginning of theexperiment, the weight of each individual is taken and recorded bythe assistant. The individual is allowed to pre-exercise activity.The work rates in kg-m/min are set in descending order. The heartrate while cycling at 60 rpm is recorded at the beginning. The heartrate is measured after every one min in order to attain steady value.The assistant stopped the individual after cycling for 6 minutes andhis/her work rate wattage is measured and recorded. The rpm valuesrecorded when cycling are converted to speed in km/h and then towatts provided that the speed&gt16 km/h. The estimates of maximumoxygen uptake are calculated using the weight, heart rate and thework rate of each individual (Kaminsky, L. A. 2014, 85). The resultswere recorded in a table.

Jacksonequation method

According to thesecond method used in this experiment is the predicting of VO2max without the need for exercise testing. This was achieved by theapplication of the NASA JSC method of VO2 max prediction.This method uses questionnaire on the exercise history, age, weightand height in the calculation of VO2 max where weight andheight are used to calculate BMI. After finding the BMI of eachindividual, the formula below is employed to calculate VO2max

Where male is onewhile female is zero,

BMI=weight(kg)/square of height

PA-R=questionnaire score

The participantsused in this experiment had age ranging from 19 to 41 years old, butmost of the individuals were in their early twenties. Only maleparticipants were involved in the experiment, and their height rangedfrom 1.62 to 1.99 meters. 175 individuals in total participated inthe data collection.


Table 1


Jackson et al., Equation

Åstrand-Rhyming Cycle Test

measured VO2 max

Mean (ml/kg/min)




Standard deviation (ml/kg/min)




The graphs below illustrate the correlation between the three methodsof estimating cardiorespiratory fitness and the relationship of VO2max obtained using NASA-JSC equation.

The r value andp-value for the correlation between the direct measure and Jackson’sequation and direct measure and Åstrand-Rhyming Cycle Test arepresented in Table 2 below showing clearly the correlation betweenthe three methods results which vary slightly.

Table 2


Spearman`s rank Correlation coefficient

2-tailed significance P value

Direct measure and Jackson`s equation



Direct measure and Åstrand-Rhyming Cycle Test



Based on the result from the experiment, lower VO2 max wasassociated with older participants e.g. the individual with thehighest measured VO2 max value, 72.94 ml/kg/min, was amongthe youngest, 19 years old while the oldest individual, 41 years, hadVO2 max of 46.00 ml/kg/min. The individual with thehighest VO2 max (Jackson equation), 72.00 ml/kg/min, hadBMI of 20.89 while the individual with VO2 max of 30.00ml/kg/min had BMI of 28.40.


This study was objectively conducted to study the relationshipbetween direct measurement and indirect estimation of VO2max. Based on the results correlation coefficient, the direct measureof Vo2 max correlated significantly with indirect estimation of VO2max. The direct measure and Jackson’ ethod has strong relationshipwhile the relationship between the direct measure and Åstrand-RhymingCycle Test was moderat (Schwellnus, M. 2008).. The strongrelationship between direct measure and Jackson method may be due tothe environmental conditions within the laboratory are easilycontrolled. Therelatively higher correlation coefficient for Åstrand-Rhyming CycleTest (submaximal test) may have been resulted from activation ofgreater quantity of Type II muscle fibresWhich is associated with increased fatigue compare to theJacksons equation. Physical exercise in the submaximal exercisetesting may result in anaerobic energy sources and thus affectingmaximum oxygen uptake since VO2 max becomes reduced. Dueto this reason, the VO2 max of submaximal exercise testingwas the lowest among the three. Jackson’s equation andÅstrand-Rhyming Cycle Test are valid methods of estimating VO2max, but the former is more suitable due to its strong correlationwith direct measure of VO2 max (Schwellnus, M. 2008).

The maximumoxygen uptake can be affected by the cardiorespiratory fitness of theparticipants involved in this experiment. The participants who havehigh cardiorespiratory fitness therefore may have a higher VO2max value compare to those with lower CRF. Such individuals arephysically active and healthy. Physical activity increased themetabolic activities of the participants thus the demand for moreoxygen and nutrients to sustain such activities was created(Rosenfeld, S. A. 1997, 56). As the body ages, its ability toundertake aerobic exercises reduce because body undergoes certainchanges. Naternicola, explains that approximately 10 percent of theaerobic capacity is reduced after every 10 years. This is because, asone ages, his/her body’s to perform various functions continues todeteriorate. (Naternicola, N. L. 2015, 34). Reduced metabolicactivity of the body is associated with low heart rate and hence theamount of blood pumped by the heart with each heartbeat reduced.Eventually, the VO2 max capacity of the individual reduces(Neeraja, K. P. 2006, 75).

There werelimitations associated with this study e.g. the Physical ActivityRating questions in the questionnaire using in the Jackson’sequation may have been under- or over-overestimated. Therefore, theaccuracy scores of the questionnaire are altered with and thusreducing the validity of the data collected using Jackson’sequation. The resulting VO2 max values as equallyaffected. Information such as health condition, genetic heredity,whether they are on medication or not, etc. may not be well presentedby the participants (Naternicola, N. L. 2015, 147). Only maleparticipants were used in this study thus affecting the reliabilityof the data collected as it was characterized with biasness. Anotherlimitation of the experiment was that it could not bring out thecardiorespiratory fitness difference between males and females as itonly involved males in the study.

Guidance throughthe PA-R questions should be provided to the participants in order toreduce chances of over estimating or underestimating values. Goodaccount of the lifestyle should also be taken as they affect theenergy consumption and activity of tissues and cells. So as toenhance understanding of the variation in the CRF between males andfemales and enhance the reliability of the information provided bothmale and female participants should be included.


Despite theabove-mentioned challenges and limitations, the experiment enhancedthe understanding of the estimating methods of aerobic capacity.There is a significant correlation of direct measurement of VO2max with the indirect estimation methods i.e. Jackson’s equationand Åstrand-Rhyming Cycle Test. Jackson’s equation has a strongerrelationship with direct measure than the Åstrand-Rhyming Cycle Testmethod. Increase in BMI and age of individual reduces the maximumoxygen uptake of the body while physical activity enhances thecardiorespiratory fitness and consequently, VO2 max. Theinformation on the factors that affect CRF and its benefits to thebody enables an individual to involve in practices that enhancestheir CRF for enhanced health and body performance.


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