Measuring Work Economy
Resource Page on Measuring Work Economy
Measuring Work Economy
Measuring Work Economy is of interest to coaches, researchers and athletes as it can help us to assess the effectiveness of endurance training programmes. However, there are a number of ways in which Work Economy can be measured. This page provides a critical analysis of methods commonly used for the measurement of Work Economy.
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Measuring Work Economy - 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?
This page explains what methods for studying changes in work economy 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 Work Economy
The following terms and concepts are key for an understanding of how work economy is measured:
1. Calorie – this is a unit of energy.
2. Lactate Threshold – this is the exercise intensity at which blood lactate rises above its resting value.
3. Net Energy Cost of Running – this is a term that has been used to describe the ratio of steady state oxygen consumption to running velocity.
4. Running economy – this is a term commonly used to describe how oxygen it takes to run a given distance at a given speed. The term running economy can also be used to describe the caloric cost of running.
5. Velocity at VO2-max (vVO2-max) – this is a variable that combines VO2max and running economy into a single factor, which is more powerful in terms of explaining individual differences in performance as compared to using either VO2-max or running economy alone.
6. Work economy – this is a measurement term used to classify efficiency. Work economy can be measured in terms of the oxygen cost or in terms of the caloric cost of exercise.
MEASURING WORK ECONOMY - An Introduction
Running economy, or work economy if we account for other exercise modalities, is the measurement used to classify efficiency. Running economy is most commonly described in terms of how much oxygen it takes to run a given distance at a given speed (Saunders et al., 2004). When described in terms of oxygen consumption, two different units of measurement are widely used:
- Measurement relative to time: this calculation is measured in milliliters of oxygen per kilogram of body mass per minute; and
- Measurement relative to distance: this calculation is measured in milliliters of oxygen per kilogram of body mass per kilometer.
When using the measurement relative to time, then it is important to specify the speed at which economy is being assessed. Standard practice with highly-trained endurance athletes is to assess running economy on a treadmill at 16 km/hr and at a 1% grade incline. The 1% grade incline is treadmill running has been shown to most accurately reflect the energetic cost of outdoor running when this level of inclination is used (Jones & Doust, 1996). However, a running speed of 16 km per hour is unlikely to be suitable for all populations and speeds such as 12 or 14 km per hour are commonly used in young athletes.
Measuring Work Economy at a Range of Speeds
A similar running speed is likely to be used if describing running economy in terms of milliliters per kilogram per kilometre. However, it has been theorized that, so long as running speed is below Lactate Threshold, then the oxygen cost of running is independent of speed. This would mean that we could assess running economy in an individual at a range of speeds and, if expressed in milliliters per kilogram per kilometre, we should have the same value for running economy each time. However, this has been shown to be incorrect (Vickers, 2005). So while this unit of measurement might seem appealing as a means of allowing for comparison of findings from different studies, there may still be some dangers associated with making these comparisons when different speeds have been used.
Measuring work economy using oxygen consumption
Running economy is commonly described in terms of how much oxygen it takes to run a given distance at a given speed. When described in terms of oxygen consumption, two different units of measurement are widely used. These are milliliters of oxygen per kilogram of body mass per minute and milliliters of oxygen per kilogram of body mass per kilometer. To convert oxygen consumption in milliliters per kilogram per minute at a given speed into milliliters per kilogram per kilometre, apply the following formula:
VO2 (ml/Kg/Km) = VO2 (ml/kg/min) / (speed (km/h) / 60)
For example, for an athlete with a running economy of 45 ml/kg/min at 16km/h, we would need to divide 45 by 16/60, providing a running economy of 168.75 in ml/kg/km.
Running Economy standards
The following standards have been proposed when assessing running economy in ml/kg/min at a speed of 16km/h:
· Excellent = 44-47 ml/kg/min
· Very Good = 47-50 ml/kg/min
· Average = 50-54 ml/kg/min
· Poor = 55-58 ml/kg/min
When assessing running economy in ml/kg/km, the following standards have been proposed:
· Excellent = 170-180 ml/kg/km
· Very Good = 180-190 ml/kg/km
· Above Average = 190-200 ml/kg/km
· Below Average = 200-210 ml/kg/km
· Poor = 210-220 ml/kg/km
When looking at these standards, which have been proposed by Jones (2007), we should appreciate that they have been established as a guideline for highly trained middle and long distance runners. Clearly, these values will not apply for other exercise modalities.
Measuring work economy using caloric cost
Research into running economy has typically involved measuring this variable in terms of VO2 or oxygen consumption. However, in reality, the assessment of oxygen uptake is a surrogate measure of running economy. This is because the measurement of oxygen uptake does not take into consideration the fact that, depending on the substrate being metabolized, the energy equivalent of a volume of oxygen will vary. The oxidation of carbohydrate generates 21kJ of energy for each liter of oxygen but the oxidation of fat generates only 19.6kJ of energy for each liter of oxygen. From this, it is clear that the caloric cost of running may be different in two athletes where the oxygen cost has been shown to be the same. For this reason the caloric unit cost of running, measured in Kcal/kg/km, has been proposed as a superior way of expressing running economy (Fletcher et al., 2009).
Measuring Work Economy – Limited Research
Very few studies (Margaria et al., 1963; Pialoux et al., 2008) have measured running economy in this way. As a result, when reviewing the literature on economy, we currently have to make do with findings relating to oxygen consumption. One notable exception in the literature is an investigation into the influence of pedaling rate on the energy cost of cycling in humans (Belli & Hintzy, 2003). This study found that when cycling economy was measured in terms of oxygen cost, there was a marked difference between the most economical pedaling rate and the preferred pedaling rate chosen by professional cyclists. However, when cycling economy was measured in terms of caloric cost the most economical pedaling rate was in agreement with the preferred pedaling rate of cyclists. This supports the idea that the caloric cost of exercise is a better way of expressing work economy.
Additionally, in a comparative study on the oxygen cost versus the caloric cost of running, it was found that the caloric cost was sensitive to changes in running speeds whilst the oxygen cost was not sensitive to such changes (Shaw et al., 2014). Although previous research has shown middle distance runners to be more economical at faster running speeds and long distance runners to be more economical at slower running speeds (Daniels & Daniels, 1992). However, it is widely considered that economy is independent of speed. This may be because the majority of studies on economy have not measured the caloric cost of exercise. As such, the difference in the sensitivity to changes in running speeds reported by Shaw et al., (2014) may be another reason to use the caloric cost of exercise as a preferred measure of economy.
Repeated Sprint Ability (RSA) tests
A large number of Repeated Sprint Ability (RSA) tests have been reported in the literature. A common feature of these tests is that they involve repeated short, maximal effort, sprints with short brief recovery periods between bouts. It is usual for these tests to measure and record three separate variables. These are the best sprint score achieved in any single effort in the test, the mean sprint time for all the sprints performed in the test and the fatigue index.
The fatigue index is usually measured in terms of the difference between the best and the worst score in the test. Mean sprint scores have been shown to have much smaller coefficients of variation and error values compared to fatigue index scores (Oliver, 2009; Spencer et al., 2006). As a result, the value of fatigue index scores has been questioned, and mean sprint score is currently considered to be the primary measurement in a RSA test (Dawson, 2012). The drawback of using mean sprint score as a proxy measure of glycolytic capacity is that it is not possible to determine the relative contribution of aerobic and anaerobic processes towards improved scores. This is a limitation that is common to all performance based field tests.
Net Energy Cost of Running
Running economy, or work economy if we are accounting for other exercise modalities, is the measurement used to classify total efficiency. Running economy is commonly described in terms of how much oxygen it takes to run a given distance at a given speed. However, in reality, the assessment of oxygen uptake is a proxy measure of running economy. This is because the measurement of oxygen uptake does not take into consideration the fact that, depending on the substrate being metabolized, the energy equivalent of a volume of oxygen will vary. Thus, it is likely that measures of running economy that are based upon the caloric unit cost of running (in Kcal/kg/km) will be more accurate.
Confusing Terminology
There is some potential for confusion when reviewing the literature on variables related to running economy. This is because there is another variable known as the net energy cost of running. This variable was originally described by Di Prampero (1986). It has been defined as the ratio of steady state oxygen consumption to running velocity. The potential for confusion here arises from the fact the name of the variable seems to be implicit of a measurement similar in nature to the caloric unit cost of running. However, the definition bears much closer resemblance to a measure of running economy expressed in terms of oxygen consumption. Nevertheless, despite confusion over terminology, the measurement of this variable does raise an important question about the way in which running economy is currently measured.
According to the guidelines set out by Di Prampero, steady state oxygen consumption should be calculated as the VO2 above resting levels. In other words, we should measure net oxygen consumption rather than gross oxygen consumption. Net oxygen consumption refers to the total oxygen consumption minus the resting value. Gross oxygen consumption just refers to total oxygen consumption. Net oxygen consumption may provide a better estimation of active energy use compared to gross oxygen consumption. This raises another potential question mark regarding the methods of assessing running economy that are currently in common use. As such, care needs to be taken when drawing any conclusions about the efficacy of various training interventions for the development of running economy or work economy.
Velocity at VO2-max (vVO2-max)
Running economy, or work economy if we are accounting for other exercise modalities, is the measurement used to classify total efficiency. Running economy is commonly described in terms of how much oxygen it takes to run a given distance at a given speed, although it is likely that a caloric unit cost of running, measured in Kcal/kg/km may be superior. Nevertheless, findings from studies that have measured the oxygen cost of running are still of interest. Such measures of running economy have been found to be strong determinants of running performance (Saunders et al., 2004). Furthermore, when such measures of running economy are combined with VO2-max we have a very powerful means of predicting endurance running performance in the form of vVO2max.
VVO2max combines VO2-max and running economy into a single factor, which is more powerful in terms of explaining individual differences in performance as compared to using either VO2-max or running economy alone. VVO2max is calculated as the ratio between VO2max (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 Work Economy - SUMMARY
Running economy, or work economy if we are accounting for other exercise modalities, is the measurement used to classify total efficiency. Running economy is commonly described in terms of how much oxygen it takes to run a given distance at a given speed. When described in terms of oxygen consumption, two different units of measurement are widely used. These are milliliters of oxygen per kilogram of body mass per minute and milliliters of oxygen per kilogram of body mass per kilometre.
A possible question mark over these measurements is that they tend to use gross oxygen consumption, whereas it has been theorized that net oxygen consumption may be a more appropriate measurement. Additionally, the caloric unit cost of running, measured in Kcal/kg/km, may be a more appropriate way of expressing running economy. Unfortunately, it is less common. Finally, it is important to remember that running economy, in combination with VO2-max, can be used to determine vVO2-max, which is a powerful method for predicting endurance performance.
Additional Note
If you found this resource page interesting, it is very likely that you will be interested in my in depth piece on how to accurately achieve a predicted marathon time
References (0-6)
Daniels, J. and Daniels, D. (1992). Running economy of elite male and elite female runners. Medicine and Science in Sports and Exercise, 24 (4), pp. 483-9
Jones, A. M. and Doust, J. H. (1996). A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. Journal of Sports Science, 14, pp. 321-7
Saunders, P. U., Telford, R. D., Pyne, D. B., Peltola, E. M., Cunningham, R. B., Gore, C. J., & Hawley, J. A. (2006). Factors affecting running economy in trained distance runners, Sports Medicine, 34 (7), pp. 465-85
Vickers, R. R. (2005). Running economy: comparing alternative measurement models. Naval Health Research Centre. Accessed: http://www.dtic.mil/dtic/tr/fulltext/u2/a445216.pdf
Jones, A. M. (2007). Middle and long distance running. In: Winter, E. M., Jones, A. M., Davison, R., Bromley, P. D. & Mercer, T. H. (2007). Sport and Exercise Physiology Testing Guidelines. London: Routledge
Belli, A. and Hintzy, F. (2003). Influence of pedaling rate on the energy cost of cycling in humans. European Journal of Applied Physiology, 88, pp. 158-62
References (7-12)
- 7. Fletcher, J. R., Esau, S. P. & McIntosh, B. R. (2009). Running economy: beyond the measurement of oxygen uptake. Journal of Applied Physiology, 107, pp. 1918-22
- 8. Margaria, R., Cerretelli, P., Aghemo, P. & Sassi, G. (1963). Energy cost of running. Journal of Applied Physiology, pp. 367-70
9. Pialoux, V., Proust, O. & Mounier, R., Energy expenditure of submaximal running does not increase after cycle-run transition. Journal of Sports Medicine and Physical Fitness, 48, pp. 143-148
10. Di Prampero, P. E. (1986). The energy cost of human locomotion on land and in water. International Journal of Sports Medicine, 7, pp. 55-72
11. Saunders, P. U., Pyne, D. B., Telford, R. D. & Hawley, J. A. (2004). Factors affecting running economy in trained distance runners. Sports Medicine, 34 (7), pp. 465-85
12. Shaw, A. J., Ingham, S. A. & Folland, J. P. (2014). The valid measurement of running economy in runners. Medicine and Science in Sports and Exercise, 46 (10), pp. 1968-73
Foxwood Personal Training, York
I do hope you found this resource page on Measuring Work Economy insightful. However, it is unlikely that I will be providing further updates to the page. This is because the creation of this resource page was part of a previous venture. As you have found your way to this website, you will be able to see that my focus is now on personal training. As such, I do plan to continue producing content. Any future content, however, will be focused on personal training, sports massage or running training. This is in alignment withe three core services I provide here at Foxwood Personal Training.
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Our requirements are as follows:
1) You must speak English. Unfortunately, I am not fluent in other languages. So whilst, yes, you can be based from anywhere in the world. If you are not fluent in English, then it will probably present too much of a communication barrier between us.
2) You must have good internet access. As this is an online coaching service. If you can not access a decent internet connection on a day to day basis it simply will not work.
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I am specifically interested in runners that are ready to properly commit to being the best possible runner they can be. If this sounds like you, then I would like to hear from you. This doesn’t necessarily mean you are elite or world class. You may be sub-elite, or you may be a good club runner. However, the key thing is that you are in a phase of your life where you are able to give it your all. If this applies to you, then we could go really far together.
Tim Egerton Running Coaching
If you have read this far, then I can safely assume you are still interested in running coaching. As such, you will probably want to know a little more about me.
My name is Tim Egerton. I am a former National level middle distance runner. I have a 3:45 PB in the 1500m and also a 1:50 pb in the 800m. I won the UK Inter-Counties title in the Mile, and I was also England Championship bronze medallist at 1500m. I was a North of England Champion at 1500m and also at 3000m. I was also a National and North of England championship medallist over 5000m.
My racing credentials went beyond track racing though. As a junior, I was selected to run for England on three occasions in Mountain Running. This included the World Mountain Running Championships in Austria, 2002. I also enjoyed success at cross country. I placed 5th in the UK Inter-counties Cross Country Championships. I also placed 5th in the North of England Cross Country Championships.
Beyond my racing performances, I also have a strong academic background. I have a BSc (Hons) Sport and Exercise Science degree, as well as an MSc In Strength and Conditioning. I was a lecturer in Strength and Conditioning for four years at the University of Derby. I also hold a level five diploma in Sports Therapy. As you will also be able to see, from this resource page on Measuring Work Economy, I have remained up to date on Sports Science.
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Of course, whilst the above is all well and good, you are probably interested in my coaching credentials. So, what follows is some of the highlights of my coaching career.
As a former sprints coach at my local athletics club, I coached two athletes to qualify for the English Schools Track and Field Championships. As a Strength and Conditioning Coach, I have worked with numerous sprinters and middle distance runners. All of these athletes improved their PB’s whilst working with me. Several of these athletes substantially improved their performance levels levels to the extent that they won medals at North of England Championships. Some of these athletes also went on to qualify for the UK Olympic Trials and World Trials. It is worth noting that, as a sports massage therapist, I have also worked with Olympic Athletes, Commonwealth Games Medallists, and World Champions.
Moving up in distance, in the last 12 months I have coached three different marathon runners. All three of these runners managed to improve their marathon PB by at least 10 minuets within one year of working with me.
I don’t say any of this to impress you, but to impress upon you that my coaching works, and that I walk the walk. So if you are ready to take you running to the next level, and if you believe I am the person to help you to do so, then please get in touch!
I look forward to hearing from you.
Tim Egerton