Measuring Aerobic Capacity

INTRODUCTION

Increasing the ability to perform repeated muscular actions for an extended duration of time is a goal of many training programs. Endurance performance is largely explained by three key factors: aerobic capacity, lactate threshold, and work economy. A great deal of research has therefore been devoted to the study of changes in measures in these areas in response to different interventions. Exercise scientists have developed many ways of measuring these variables and each has strengths and weaknesses, as well as different degrees of accuracy.

What does this page provide on measuring aerobic capacity?

This page explains what methods for studying changes in aerobic capacity and related measures are available, when they are used, why they are used, and how accurate they are. By the end, you will be able to critically appraise studies investigating these areas and understand their individual strengths and weaknesses.

Identifying key concepts - Measuring Aerobic Capacity

The following terms and concepts are key for an understanding of how aerobic capacity is measured:

1. Aerobic capacity – this is the maximum capacity for the body to utilize oxygen. The primary direct measure of aerobic capacity is VO2max.

2. Arterial-venous difference – this is the difference in oxygen content between the arterial blood and the venous blood. It provides an indication as to how much oxygen is removed from the blood in the capillaries as the blood circulates the body.

3. Cardiac output – this is the amount of blood pumped out of the heart per minute. It is calculated by reference to stroke volume (the volume of blood pumped from the heart with each beat) and heart rate.

4. Critical power – this is the maximum power that can be maintained for a very long period of time without fatigue. This represents the boundary between steady state and non-steady state exercise intensity domains.

5. Exercise-Induced-Arterial-Hypoxemia – this is when oxygen saturation levels drop below resting levels during exercise.

6. Time-to-exhaustion at vVO2-max – this is the duration for which the velocity associated with VO2max (vV02-max) can be maintained. The abbreviation tlimvVO2-max is commonly used.

7. VO2-max – this is the primary direct measure of aerobic capacity. It is usually measured in millilitres per kilogram of body weight per minute (ml/kg/min).

8. vVO2-max – this is the velocity at which VO2max occurs. It is determined by calculating the ratio between VO2-max (in milliliters per kilogram per minute) minus oxygen consumption at rest and the energy cost of running (in milliliters per kilogram of body mass per second).

MEASURING AEROBIC CAPACITY

Introduction

The primary direct measure of aerobic capacity is VO2-max. VO2-max is the maximum capacity for the body to utilize oxygen. It is usually measured in milliliters per kilogram of body weight per minute (ml/kg/min). There is a very strong correlation between endurance performance and VO2-max when measurements are taken for a cross section of the whole population (Butts et al., 1991). Surprisingly, however, VO2-max is a very poor predictor of endurance performance amongst homogenous groups of athletic individuals (Tam et al., 2012). Thus, we should not be surprised to find no correlation between VO2-max and personal best 10,000m times in a group of world-class distance runners. This is because aerobic capacity is just one variable amongst many that contribute towards endurance performance.

Measuring VO2-max

VO2-max is the maximum capacity of the body to utilize oxygen. This is why it is measured in milliliters per kilogram of body weight per minute (ml/kg/min). It is a measure of how much oxygen (in milliliters) that the body can take in and deliver to the muscles each minute, relative to bodyweight. VO2-max is typically assessed by using an incremental discontinuous steady-state exercise protocol in combination with pulmonary gas exchange apparatus. This involves the measurement of VO2 (i.e. oxygen uptake) during each incremental stage of a test. Increase in oxygen uptake is generally seen with most subsequent stages of a test. However, at some point during the test a plateau in oxygen uptake is occurs. At this stage, VO2-max is deemed to have been attained.

Unfortunately, the VO2-max plateau is not observable in all tests (Ferretti, 2014) and the incidence of this plateau appears to depend on the modality of exercise administration (Gordon et al., 2012). So in the absence of a clear VO2 plateau, it has been deemed necessary to use subsidiary criteria to establish whether VO2-max has been attained. These are:

(1) a lack of increase in heart rate between successive stages,
(2) a respiratory exchange ratio value of greater than or equal to one,
(3) blood lactate concentration higher than 10mM at maximal exercise, and
(4) a rating of perceived exertion on the Borg scale of at least 19/20.

VO2-max Criteria

At least two of these subsidiary criteria are required to be met at the end of the test in order to have sufficient confidence that VO2max was attained (Howley et al., 1995). We should have an awareness of these criteria when reading research pertaining to the assessment of VO2max. If mention is not given to the attainment of these criteria it may be prudent to treat the findings of a study with an element of caution.

Douglas Bag Method

The assessment of aerobic capacity involves the measurement of oxygen uptake or VO2. Quantification of oxygen uptake is achieved through pulmonary gas exchange measurement. There are two main methods of pulmonary gas exchange measurement. The traditional method is to use Douglas Bags for the collection of expired air. Semi-automated pulmonary gas exchange measurement systems along with software to determine pulmonary gas exchange parameters are also now available. However, the traditional Douglas Bag approach is still widely regarded as the gold standard and validation of alternative systems usually involves comparison against Douglas Bags.

Breath-by-Breath Analysis

The prolonged duration associated with expired gas collections into Douglas Bags means this technique is most suited to determining steady state gas exchange. Conversely, online systems are advantageous in that they can provide valuable information over very short time frames. For example, through breath-by-breath analysis we can measure the rate at which oxygen uptake increases in response to an abrupt transition from rest, or a low work rate, to a higher constant work rate. Both methods may therefore be useful in different circumstances. The rate of increase in oxygen uptake is commonly referred to as VO2 kinetics or oxygen uptake kinetics.

Indirect measures of aerobic capacity

Many performance-based field tests have been developed to predict aerobic capacity by indirect measurements. These include tests such as the multi stage fitness test (often referred to as the bleep test) and the yo-yo test. These two examples involve running back and forth, keeping time to intermittent beeps, which gradually become more frequent, necessitating faster running speeds as individuals progress in the test. The requirement is to keep up with the beep for as long as possible, and so they are tests to volitional exhaustion.

While performance-based tests of this nature have been shown to predict VO2-max with a reasonable degree of accuracy, the exact same problem exists here as with using VO2-max to predict endurance performance. VO2-max is a good predictor of endurance performance in a cross-section of the general population but a very poor predictor of performance in a homogenous group of highly-trained endurance athletes. Similarly, if an accurate measure of VO2max is deemed to be worth obtaining in a group of endurance athletes, then we should measure it directly rather than estimate it on the basis of field tests. Situations where it may be acceptable to use these performance based field tests might include testing in sports where heterogeneity is expected in terms of endurance levels and aerobic development.

Critical Power and Critical Velocity

One important exception to the idea that performance-based tests have limited value in the assessment of endurance athletes is the critical velocity or critical power test. Critical Power was first defined as the maximum power that can be maintained for a very long period of time without fatigue (Monod & Scherrer, 1965). Although that definition seems qualitative in nature, critical power has since been defined in more quantitative terms as the power-asymptote of the hyperbolic relationship between power output and time-to-exhaustion.

An asymptote of a curve is a line such that the distance between the curve and the line approaches zero as they tend to infinity. It has been proposed that this means critical power represents the boundary between steady state and non-steady state exercise intensity domains (Vanhatalo et al., 2011). However, critical power is often misinterpreted as a purely mathematical construct that lacks physiological meaning and only in recent years has this concept begun to emerge as valid and useful technique for monitoring endurance fitness (Vanhatalo et al., 2011).

Predicting Marathon Performance

Theoretically, critical power is representative of the maximal workload that can be maintained indefinitely (Monod & Scherrer, 1965; Moritani et al., 1981). In practice, a test of critical velocity in running has been shown to accurately predict marathon performance (Florence & Weir, 1997). In order to determine critical velocity subjects were required to perform a series of four randomly ordered treadmill runs at velocities ranging from 3.6 – 6.0m/s. They were required to continue each run until volitional exhaustion and a minimum of 20 minutes rest was given in between each run. This is consistent with established guidelines for conducting critical velocity or critical power tests, with standard procedure being to perform 3 – 5 work bouts at a power loading of sufficient intensity to elicit exhaustion within 1–10 minutes (Housh et al. 1990).

In performing a test of critical velocity in running, two pieces of information are required from each run in order to calculate critical velocity. These are: the distance run and the time to exhaustion. Having obtained this information, simply plot the points on a graph, and the slope of the line will represent an individual’s critical velocity.

MEASURING DETERMINANTS OF VO2-MAX

Introduction

There are two main determinants of VO2-max: cardiac output and arterial-venous oxygen difference. We can improve VO2-max either through increasing cardiac output or through increasing the arterial venous oxygen difference. So if a training intervention elicits an increase in VO2-max, either of these two variables could be primarily responsible. Unfortunately, however, neither Douglas Bags nor online systems that enable breath-by-breath analysis of pulmonary gas provide insight into these.

What is cardiac output?

Cardiac output refers to how much blood is pumped out of the heart per minute and is calculated by reference to both stroke volume (the volume of blood pumped from the heart with each beat) and heart rate.

What is arterial-venous oxygen difference?

Arterial-venous oxygen difference is the difference in oxygen content between the arterial blood and the venous blood. It provides an indication as to how much oxygen is removed from the blood in the capillaries as the blood circulates in the body.

The measurement of cardiac output using traditional methodologies is impractical during intense exercise. As such, there is limited high-quality data available relating to the relative contributions cardiac output and arterial-venous oxygen difference towards improvements in VO2-max. Despite such limitations, cardiac output is widely regarded as being the primary limiter of VO2-max.

Exercise-Induced-Arterial-Hypoxemia

Complications may arise as a result of excessively increased cardiac output in elite endurance athletes, including the phenomenon of Exercise-Induced-Arterial-Hypoxemia (EIAH). EIAH occurs when oxygen saturation levels drop below resting levels during exercise. EIAH can be characterized as mild, moderate or severe. These classifications have been defined in terms of levels of arterial oxygen saturation, with mild being 93-95% saturation, moderate being 88-93% saturation and severe being less than 88% saturation (Dempsey & Wagner, 1999). Severe EIAH can mean a reduction in oxygen saturation levels by <15% below resting levels during intense exercise.

It is thought to occur in highly-trained individuals because a large cardiac output results in the blood passing through the pulmonary capillaries at such a high rate that there is insufficient time for full oxygen diffusion to occur. If this is indeed the case, the phenomenon of EIAH may, at least in part, support the view that VO2-max is limited primarily by cardiac output rather than arterial-venous oxygen difference. Nevertheless, EIAH has largely been overlooked in the sports science literature. This is unfortunate, since it is possible to measure oxygen saturation in a non-invasive manner using pulse oximetry.

Measuring cardiac output

Introduction

Several techniques exist for the assessment of cardiac output. However, the use of traditional methodologies are impractical during intense exercise. As such, there is limited high quality data available relating to the relative contributions cardiac output and arterial-venous oxygen difference towards improvements in VO2-max. Methodologies for the assessment of cardiac output include the Fick Method, the Thermodilution Technique, inert gas rebreathing and pulse contour analysis.

Fick method

The Fick method is the gold-standard method for measuring cardiac output. The Fick Method computes cardiac output as follows:
Cardiac Output = VO2 / arterial-venous oxygen difference.

In practice VO2 is usually determined using pulmonary gas exchange measurement methods. Arterial-venous oxygen difference can be determined by comparing the difference between the oxygen concentration of blood taken from the femoral, brachial or radial artery and the oxygen concentration of blood taken from the pulmonary artery. The pulmonary artery is used as an indicator of venous oxygen concentration. This method is invasive, as it requires the use of a pulmonary artery catheter to sample mixed venous blood. However, in practice, arterial-venous oxygen difference is usually determined using the Fick Principle.

The Fick principle states that the blood flow to an organ (in this case the heart) can be calculated using a marker substance, on the assumption that: (1) the amount of marker substance taken up by the organ per unit time, (2) the concentration of marker substance in arterial blood supplying the organ, and (3) the concentration of marker substance in venous blood leaving the organ are all known. The Fick principle can be applied using a number of marker substances. Carbon Dioxide is the most commonly used substance. Here, the difference in carbon dioxide content between expired and inspired air is measured in order to estimate arterial-venous oxygen difference.

Thermodilution Technique

The Thermodilution Technique involves inserting a temperature sensitive catheter from a peripheral vein into the pulmonary artery. A saline solution of known temperature and volume is injected into the right atrium. It then mixes with, and thus cools, the blood. The change in blood temperature is measured and cardiac output is computed using this information.

Inert Gas Rebreathing

Inert gas rebreathing is a technique that involves pulmonary gas exchange measurement. A small amount of an inert gas is inhaled from a rebreathing bag. The rate of disappearance of the gas from the alveolar space is proportional to the flow of blood perfusing the ventilated parts of the lungs. This is used to estimate cardiac output.

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Pulse Contour Analysis

Pulse contour analysis makes use arterial pressure measurements to estimate stroke volume. When such measurements are taken in conjunction with the measurement of heart rate, this allows for the estimation of cardiac output. However, the arterial pressure profile is analysed in a wide number of different ways, depending on which algorithms are used for the estimation of stroke volume. Furthermore, if changes in arterial tone occur, then the primary assumptions about the interaction between stroke volume and arterial pressure also change, and the validity of a specific algorithm may be degraded (Pinsky, 2003). As changes in arterial tone are to be expected during exercise, there may be difficulties associated with using pulse contour analysis for the estimation of cardiac output during exercise.

PhysioFlow

The PhysioFlow device is a form of impedance cardiography. Disposable sensors on the neck and chest are used to transmit and detect electrical and impedance changes in the thorax, which are used to measure and calculate hemodynamic parameters. There is a small battery pack for the device that can be strapped around the waist, making it practical to use during exercise.

The PhysioFlow method has been shown to be valid in its measurement of cardiac output at rest and during steady state dynamic leg exercise performed in the supine position relative to the Fick method (Charloux et al., 2000). While this is encouraging, we should bear in mind that most sport and exercise does not take place in the supine position. It is therefore fortunate that subsequent research has reported similar findings using different modes of exercise (Ruddy et al., 2001; Tordi et al., 2004). The PhysioFlow device has also been shown to produce reliable results when measuring cardiac output during cycle ergometry (Welsman et al., 2005).

Some research has shown PhysioFlow to overestimate cardiac output (Kemps et al., 2008) and conflicting findings have also been reported regarding the accuracy of the device (Bougault et al., 2005; Taylor et al., 2012). Furthermore, in a comparison of four different methods of cardiac output assessment during exercise, one of which was use of the PhysioFlow device, it was found that determination of cardiac output depends significantly on the applied method (Siebenmann et al., 2014). The other three methods assessed were the fick method, inert gas rebreathing and pulse contour analysis.

Measuring arterial-venous difference

Introduction

Arterial-venous oxygen difference is the difference in oxygen content between the arterial blood and the venous blood. It provides an indication as to how much oxygen is removed from the blood in the capillaries as the blood circulates in the body. Arterial-venous oxygen difference can be measured directly using blood sampling or it can be estimated using the Fick principle.

Main methods

Arterial-venous oxygen difference can be determined by comparing the difference between the oxygen concentration of blood taken from the femoral, brachial or radial artery and the oxygen concentration of blood taken from the pulmonary artery. The pulmonary artery is used as an indicator of venous oxygen concentration. This method is invasive, as it requires the use of a pulmonary artery catheter to sample mixed venous blood. However, in practice, arterial-venous oxygen difference is usually determined using the Fick Principle.

MEASURING PERFORMANCE RELATIVE TO VO2-MAX

VO2-max is a poor predictor of endurance performance amongst high-level endurance athletes. However, velocity at VO2-max, usually abbreviated to vVO2-max, appears to be able to predict endurance performance with a high degree of accuracy (Jones, 2006). VVO2max is determined by calculating the ratio between VO2-max (in milliliters per kilogram per minute) minus oxygen consumption at rest and the energy cost of running (in milliliters per kilogram of body mass per second).

Jones, through his applied work with world-class endurance athletes including Paula Radcliffe, has been able to describe with precision the manner in which vVO2-max can predict endurance running performance. In this regard, Jones has stated that 3,000m race pace corresponds with vVO2-max, whilst 5,000m race pace corresponds with 97% of vVO2-max. This appears to be very accurate, with an error of just 0.2-0.4% (Jones, 2009).

The high degree of accuracy associated with vVO2-max is thought to arise because vVO2-max combines VO2-max and running economy into a single factor. This is therefore much more powerful in terms of explaining individual differences in performance as compared to using either VO2-max or economy as stand alone variables. However, while velocity at VO2-max may be a more useful measure of how endurance athletes have adapted to certain training interventions, the correct determination of this variable still requires the measurement of both VO2-max and running economy, which can make it onerous to calculate.

VO2 kinetics

Oxygen uptake kinetics, or VO2 kinetics, refers to the rate at which oxygen uptake increases in response to an abrupt transition from rest, or a low work rate, to a higher constant work rate. This parameter of aerobic fitness may be able to help explain any error associated with the use of velocity at VO2-max as a variable for the prediction of endurance performance. In a race situation an athlete must accelerate up to race pace within a matter of seconds. This results in an abrupt increase in the energy turnover in the working muscles over this very short time frame. If race pace is at or below the velocity associated with VO2-max then we might expect the energetic demands to be met through aerobic metabolism.

Oxygen Deficit

However, this only holds true once oxygen uptake has increased up to its maximal level. The reality is that it will take longer for oxygen uptake to increase to this level than it takes for the athlete to accelerate up to race pace. As a consequence of this is that there is an oxygen deficit associated with the onset of exercise. The longer it takes for oxygen uptake to increase to a maximal or steady state, the greater the oxygen deficit will be.

The oxygen deficit can be thought of as the difference between the amount of energy required to perform exercise at a given intensity for a certain period of time and the amount of energy provided through oxidative metabolism over the same time period. A larger oxygen deficit results in greater breakdown of high-energy phosphates and increased anaerobic glycolysis. The consequences of this include decreased concentrations of phosphocreatine and possibly ATP as well as the accumulation of metabolic by-products such as ADP, inorganic phosphate, lactate and hydrogen ions. All of these factors appear to be associated with fatigue during exercise, and so improved VO2 kinetics is likely to be beneficial for endurance performance.

Oxygen Uptake Kinetics

The increase in oxygen uptake during the first few minutes of exercise is near exponential. As a result of this, VO2 kinetics is usually characterized in terms of a time constant. The time constant is the time it takes for an exponential response to reach 63% of its final value. An exponential response can be considered to be complete once four time constants have elapsed. So in the case of oxygen uptake kinetics, a VO2 time constant of 35 seconds (normal in sedentary populations) would mean that a VO2 steady state would be attained within about 140 seconds. In contrast, Paula Radcliffe has been measured as having a VO2 time constant of 9 seconds, which corresponds to reaching a VO2 steady state in just 36 seconds. Lower time constants are expected for endurance athletes in comparison with the general population.

Greater oxygen uptake kinetics (i.e. lower VO2 time constants) reduces the oxygen deficit that occurs at the onset of exercise. This likely occurs because of a reduction in the build-up of metabolic by-products associated with fatigue. It may therefore be possible to consider oxygen uptake kinetics in tandem with vVO2-max in order to reduce the error associated with predicting endurance performance when vVO2max is used as a standalone measure. However, no research has yet been performed that has looked at how data on oxygen uptake kinetics can be used to provide a correction factor for the prediction of endurance performance on the basis of vVO2max data. Despite this, it is a variable of considerable interest, and it seems apparent that an improvement in this variable should contribute towards improved endurance performance.

Time to exhaustion at vVO2-max

VO2-max is a strong discriminator of endurance performance within groups of individuals that are heterogeneous in terms of the ability in endurance sports. In a homogeneous group of world class endurance athletes VO2max will have little to no ability to discriminate between different levels of performance. However, vVO2max is able to predict performance with considerable accuracy in such homogeneous groups. Such predictions, however, are not without error. This is because there are additional variables that also contribute towards endurance performance. One such variable is time-to-exhaustion at vVO2-max.

Time-to-exhaustion at vVO2-max appears to be highly reproducible within athletes but displays great variability among individuals with a low coefficient of variation for vVO2-max (Billat & Koralsztein, 1996). This means that within a group of individuals with very similar vVO2-max, we might expect sizeable differences in the duration for which they can maintain those velocities. As such, this variable can probably go a long way towards explaining any error associated with predictions of endurance performance that are based on vVO2-max.

Time to Exhaustion and Lactate Threshold

Time-to-exhaustion at vVO2max is not widely studied in the sports science literature. In this regard it is worth noting that lactate threshold appears to be able to explain inter-individual differences in time-to-exhaustion at vVO2max (Billat & Koralsztein, 1996). As lactate threshold is a much more commonly measured variable, there may be value in considering findings on variables such as VO2-max, running economy and lactate threshold in combination when evaluating the efficacy of endurance training protocols.

SUMMARY - Measuring Aerobic Capacity

Aerobic capacity is most commonly measured by reference to VO2-max. VO2-max is the maximum capacity of the body to utilize oxygen. It is measured in milliliters per kilogram of body weight per minute (ml/kg/min). There is a strong correlation between endurance performance and VO2-max for a cross section of the general population. In contrast, VO2-max is a poor predictor of endurance performance in a homogenous group of highly-trained endurance athletes. In contrast, VVO2-max is best able to predict performance in a homogeneous group of highly-trained endurance athletes, most likely because it is able to incorporate measures of both VO2-max and movement economy. However, there is still some measurement error associated with endurance performance predictions that are based upon VVO2-max alone. This is because other factors also play are role in the determination of endurance performance. These factors include: oxygen uptake kinetics, time-to exhaustion at velocity at VO2-max and anaerobic capacity.

Taking oxygen uptake kinetics into account when measuring VVO2-max may therefore be helpful in measuring endurance performance. For the complete assessment of an endurance athlete, it therefore seems appropriate to include these measurements alongside the assessment of vVO2-max. It should also be born in mind that the determination of vVO2-max also requires the measurement of VO2-max itself as well as running economy. Furthermore, these may represent useful measurements in their own right. For example, if a training intervention is found to produce a significant improvement in vVO2-max, information on how that improvement was achieved is likely to be of interest. Additionally, the subcomponents of VO2-max (cardiac output and arterial venous oxygen difference) should not be neglected.

Additional Note on Measuring Aerobic Capacity

If you found this resource page interesting, it is likely that you will also be interested in my in depth piece on how to accurately achieve a predicted marathon time.

Further Resources on Measuring Aerobic Capacity

This resource on measuring aerobic capacity was created whilst Tim was working on a previous project. As such, it is unlikely that Tim will be creating additional resources on measuring aerobic capacity. That said, if you found this page useful, please do get in touch. If there is a big enough demand, then I may consider expanding on this resource on measuring aerobic capacity. The likelihood, though, is that I will be focusing on Personal Training and Sports Massage content. This is now the focus on my business, and you can find links to my primary services below:

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References on Measuring Aerobic Capacity (1-5)

Butts, N. K., Henry, B. A. & Mclean, D. (1991). ‘Correlations between VO2max and performance times of recreational triathletes’. Journal of Sports Medicine and Physical Fitness, 31 (3), pp. 339-44
2. Ferretti, G., (2014). ‘Maximal oxygen consumption in healthy humans: theories and facts’. European Journal of Applied Physiology, Epub ahead of print
3. Gordon, D., Mehter, M., Gernigon, M., Caddy, O., Keiller, D., Barnes, R. (2012). ‘The effects of exercise modality on the incidence of plateau at VO2max’. Clinical Physiology and Functional Imaging, 32, pp. 394-9
4. Howley, E. T., Bassett, D. R. & Welch, H. G. (1995). ‘Criteria for maximal oxygen uptake: review and commentary’. Medicine and Science in Sports and Exercise, 27, pp. 1292-301
5. Dempsey, J. A. and Wagner, P. D. (1999). ‘Exercise induced arterial hypoxemia’. Journal of Applied Physiology, 87 (6), pp. 1997-2006

Rferences (6-10)

6. Jones, A. (2009). The Physiology of Running. Asics Running Conference.
7. Bougault, V., Lonsdorfer-Wold, E., Carloux, A., Richard, R., Geny, B., Oswald-Mammosser, M. (2005). ‘Does Thoracic Bioimpedance Accurately Determine Cardiac Output in COPD patients during Maximal or Intermittent Exercise?’. Chest, 127 (4), pp. 1122-31
8. Charloux, A., Lonsdorfer-Wolf, E., Richard, R., Lampert, E., Osswald-Mammosser, M., Mattauer, B., Geny, B. & Lonsdorfer, J. (2000). ‘A New Impedance Cardiograph Device for the Non-invasive Evaluation of Cardiac Output at Rest and During Exercise: Comparison with the “Direct” Fick Method’. European Journal of Applied Physiology, 82 (4), pp. 313-20
9. Kemps, H. M. C., Thijssen, E. J. M., Schep, G., Sleutjes, B. T. H. M., De Vries, W. R., Hoogeveen, A. R., Wijn, P. F. F. and Doevendans, P. A. F. M. (2008). ‘Evaluation of two methods for continuous cardiac output assessment during exercise in chronic heart failure patients’. Journal of Applied Physiology, 105 (6), pp. 1822-9
10. Ruddy, R., Lonsdorfer-Wolf, E., Charloux, A., Doutreleau, S., Bucheit, M., Osswald-Mammosser, M., Lampert, E., Mettaeur, B., Geny, B. & Lonsdorfer, J. (2001). ‘Non-invasive Cardiac Output Evaluation during a Maximal Progressive Exercise Test, Using a New Impedance Cardiograph Device’. European Journal of Applied Physiology, 85, pp. 2022

References (11-14)

11. Siebenmann, C., Rassmussen, P., Sorensen, H., Zaar, M., Hvidtfelt, M., Pichon, A., Secher, N. H. and Lundby, C. (2014). ‘Cardiac Output during exercise: a comparison of four methods’. Scandinavian Journal of Medicine and Science in Sports, Epub ahead of print
12. Tam, E., Rossi, H., Moia, C., Berardelli, C., Rosa, G., Capelli, C. & Ferretti, C. (2012). ‘Energetics of running in top-level marathon runners from kenya’. European Journal of Applied Physiology, 112 (11), pp. 3797-806
13. Taylor, K., Manlhoit, C., McCrindle, B., Grosse-Wortmann, L. & Holtby, H. (2012). ‘Poor accuracy of noninvasive cardiac output monitoring using bioimpedance cardiography [PhysioFlow(R)] compared to magnetic resonance imaging in pediatric patients’. Anesthesia and Anelgesia, 114 (4), pp. 771-5
14. Tordi, N., Mourot, L., Matusheski, B., Hughson, R. L. (2004). ‘Measurements of Cardiac Output during Constant Exercises: Comparison of Two Non-Invasive Techniques’. International Journal of Sports Medicine, 25, pp. 145-9

References (15-18)

15. Welsman, J., Bywater, K., Farr, C., Welford, D. and Armstrong, N. (2005). ‘Reliability of Peak VO(2) and Maximal Cardiac Output Assessed using Thoracic Bioimpedance in Children’. European Journal of Applied Physiology, 94 (3), pp. 228-34
16. Florence, S. and Weir, J. P. (1997). ‘Relationship of critical velocity to marathon running performance’. European Journal of Applied Physiology and Occupational Physiology, 75 (3), pp. 274-8
17. Housh, D. J., Housh, T. J. & Bauge, S. M. (1990). ‘A methodological consideration for determination of critical power and anaerobic work capacity’. Research Quarterly in Exercise and Sport, 61, pp. 406–409
18. Monod, H. and Scherrer, J. (1965). ‘The work capacity of a synergic muscular group’. Ergonomics, 8, pp. 329-8

References (19-23)

19. Moritani, T., Nagata, A., deVries, H. A., Muro, M. (1981). ‘Critical power as a measure of physical work capacity and anaerobic threshold’. Ergonomics, 24, pp. 339–350
20. Vanhatalo, A., Jones, A. M., Burnley, M. (2011). ‘Application of critical power in sport’. International Journal of Sports Physiology and Performance’. 6 (1), pp. 128-36
21. Jones, A. (2006). ‘The physiology of the world record holder for the women’s marathon’. International Journal of Sports Science and Coaching, 1 (2), pp. 101-16
22. Billat, L. V. and Koralsztein, J. P. (1996). ‘Significance of the velocity at VO2max and time to exhaustion at this velocity’. Sports Medicine, 22 (2), pp. 90-108
23. Pinsky, M. R. (2003). ‘Probing the limits of arterial pulse contour analysis to predict preload contour analysis’. Anasthesia and Analgesia, 96 (5), pp. 1245-

Additional Foxwood Personal Training Resources

Although it is unlikely I will be creating additional pages on measuring aerobic capacity, I do continuue to produce informative content on the website. In particular, I continue to update the Foxwood Personal Training Blog:

Foxwood Personal Training Blog

A recent area of focus is in the area of Strength Training for Runners. This is an area of specialism for me, and so I have written extensively on this subject. If you would like an aspect of Strength and Conditioning for Runners covered on the blog then please get in touch. If I am able to accomodate your request, then I will endevour to do so. The subject matter could include plyometrics, power training or even eccentric strength training for runners. Other areas could include stretching or recovery methods for runners. These are a few examples, but ultimately, I would like to hear from you! If you have enjoyed this page on measuring aerobic capacity, and you are interested in running performance, then there will be many more topics we can explore.