Performance evaluation in running – Part 3: Energy expenditure during running.

This is the third part (the first was about VO2max, while the second was about the energy expenditure during rest) of a journey into the evaluation of the runner’s performance, made possible with the big support of Mark Henninger (himaxx Centre for Altitude Training – Berlin, Germany), that provided the ergospirometer, the treadmill, the hypoxic chamber and his knowledge for the tests. Thanks Mark!

In terms of total energy expenditure is it more expensive running a 10 km race at 10 km/h or at 20 km/h? If we don’t consider the air friction component and if the race is run without any pace variation (steady state), the answer is: the total energy requirement is approximately the same!

The reason lies in the linear relationship between oxygen consumption and running speed. As a rule of thumb, during horizontal running the energy cost is about 1 kCal/kg/km. Thus, the energy cost of running 10 km for a 70 kg individual averages 700 kCal, regardless of running speed.

Having an ergospirometer, as explained in the previous Part 1 and Part 2, allows to know the relative contribution of Carbohydrates and Lipids in the energy transfer system; in Figure 1 the data are put together in a graph, and the main results can be described as follows:

  • the whole-body energy requirement increases up to 15-20 times above resting levels (purple curve);
  • for this athlete, between 6 and 10 km/h is evident the formation of a plateau where the ratio between Fats and Carbs contribution is constant;
  • training to extend the plateau is something to focus on, since the energy contribution of Fats is more than double of the Carbs’ one (9 kCal/g vs. 4 kCal/g);
  • the higher the speed, the lower the Fat’s contribution;
  • training at low speeds is a good way to “teach” the body to use the Lipids as energy source;
  • doing a Conconi test will allow the athlete to know exactly the different “fuels” contribution at his anaerobic threshold;
  • Proteins contribution is not taken into account, as explained in Part 2.
Figure 1 – Energy expenditure during running.

We are working on the fourth part, wich will be published after the next test session. Meanwhile…keep on training, people!

Here you can find a list of my running-related posts. Now shut down the notebook and have a run!
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Performance evaluation in running – Part 2: Carbs, Fats and Proteins as Energy for living.

This is the second part (the first was about VO2max) of a journey into the evaluation of the runner’s performance, made possible with the big support of Mark Henninger (himaxx Centre for Altitude Training – Berlin, Germany), that provided the ergospirometer, the treadmill, the hypoxic chamber and his knowledge for the tests. Thanks Mark!
During exercise the whole-body energy requirement increases 20 to 30 times above resting levels, but what are the relative contribution of Carbohydrates, Lipids and Proteins in the different energy transfer systems?
First of all, we need to define the above-mentioned “resting levels”: the BMR (Basal Metabolic Rate) is the amount of energy expended daily by humans and other animals to sustain vital functions in the waking state. Under controlled laboratory conditions, after at least 3 hours from the last light meal and without prior physical activity, the RMR (Resting Metabolic Rate) can be measured. The TDEE (Total Daily Energy Expenditure) can be divided as follows:
  • RMR accounts for 60 to 75% of TDEE;
  • thermic effects of eating account for around 10%;
  • physical activity accounts for the remaining 15 to 30%.
The first part of the ergospirometry is exactly the measurement of the RMR: without taking into account the Proteins’ contribution (being far enough from the last meal and without doing any prior physical activity allow this approximation), the machine can split the energy expenditure between Carbohydrates and Lipids measuring ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air. There are some generalized equations to predict the Resting Daily Energy Expenditure (if anyone is interested, please contact me and I will write something more specific), but the direct measurement is always the most accurate solution.
As an example, in the Table presented below a set of typical data resulting from the RMR analysis with the ergospirometer is shown.

 

Table 1 – RMR analysis data.

 

The third part will be about the energy expenditure during exercise. Meanwhile…keep on training, people!
Here you can find a list of my running-related posts. Now shut down the notebook and have a run!
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Performance evaluation in running – Part 1: the VO2max.

This is the first part of a journey into the evaluation of the runner’s performance, made possible with the big support of Mark Henninger (himaxx Centre for Altitude Training – Berlin, Germany), that provided the ergospirometer, the treadmill, the hypoxic chamber and his knowledge for the tests. Thanks Mark!

The MET (Metabolic Equivalent of Task) is a physiological measure that expresses the energy cost of physical activities. It is defined as the ratio of metabolic rate during a specific physical activity to a reference metabolic rate (set by convention to 3.5 ml  O2/kg/min):

 
 
The reference metabolic rate just mentioned, is the expression of an individual’s body capacity to transport and use oxygen during exercise and it is called VO2 (milliliters of oxygen per kilogram of bodyweight per minute [ml/kg/min]). The maximum reachable value of VO2 describes the maximum capacity to transport and use oxygen during an incremental exercise and it is called VO2max. Various methods are available to predict the VO2max value, but the most accurate values can only be obtained with a measurement.
 
Figure 1 – VO2max measurement through an ergospirometer and a treadmill. 
 
The ergospirometer (it can be seen in Figure 1) is used to measure ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air during a graded exercise test (in this case performed on a treadmill, but it can be done on a cycle ergometer or on a rowing ergometer, depending on the reference sport): the  VO2max is reached when oxygen consumption remains at steady state despite an increase in workload (see Figure 2).
 
Figure 2 – VO2 & HR vs. speed (from rest to maximum speed).

 

In Figure 3 is possible to see the plateau created by the VO2 and the HR, when reaching the maximum values.

 

Figure 3 – VO2 & HR vs. speed (detail).
 
An average untrained man will have a VO2max of around 45 ml/kg/min, while women’s values are typically 10-15% lower. These values can improve with training (altitude training is a common way, for elite athletes, to try improving the VO2max values) and decrease with age, even if the degree of trainability is very variable: some individuals may double the initial values, while some others will never improve. Elite male runners can generate up to 85 ml/kg/min and female elite runners can generate up to 77 ml/kg/min, even if higher values are reported in literature.
 
The second part will be about the energy expenditure’s splitting between fats and carbohydrates. Meanwhile…keep on training, people!
 
Here you can find a list of my running-related posts. Now shut down the notebook and have a run!
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Running at 4000 m: the hypoxic chamber (altitude training).

Have you ever thought about training at altitude? If you are a runner with passion for mountains, probably the answer is affirmative.
But what’s altitude training?
Wikipedia says that “the basic concept of living or training at altitude is to cause the body to adapt to the lower oxygen content by producing more oxygen-carrying red blood cells and hemoglobin. This improves the athlete’s ability to perform work, because more oxygen is available to the working muscles”.
Why is there less oxygen at high altitude?
At sea level the air contains around 20.9% oxygen. On the top of Mount Everest (8848 m), too. Why do we say, then, that there’s less oxygen? The difference is all in the air pressure: at sea level there is a pressure over our heads equivalent to 10 m of water. At 8848 m this pressure is equivalent to around 3.5 m of water. The percentage of the oxygen is the same, but being the pressure lower, the molecules are less compressed and, thus, more distant from each other: there are few molecules of everything in the same volume. That’s why the oxygen intake is lower, if the respiration rate is the same.
Does this kind of training really improve performance?
Apart from the cool thing of running at 4000 m even if your city is at sea level, the results of hypoxia (lack of oxygen) training are not clear. As Prof. Dr. Joachim Mester said in his speech titled “Altitude training: on myths and methods” (you can find the pdf here), the analysis of more than 100 international studies in the last 40 years show:

  • “practical experiences and also controlled studies indicate performance enhancement effects, other do not;
  • acute and chronic hypoxia induce well-known physiological effects in gas exchange, hematology etc.;
  • performance enhancement may occur; it is, however, in onset, magnitude and duration very individual;
  • re-adaptation to sea level is quite rapid, the duration of positive effects is scientifically unclear;
  • the effects of all options live high/train low – train high/live low are not sufficiently proven;
  • criteria for individual input (training load at altitude) are often insufficient: High-low responders, early-late responders.”

One thing is for sure: training at altitude (simulated or not) is hard!
I tried two different conditions in three different session. The first day (06/01/2012), the chamber was simulating the 4000 m conditions: 12.2% oxygen (18.0 °C the temperature, 41.5 % the humidity). The workout consisted in:

  • Warm-Up (2.50 km @ 4’35″/km);
  • 1×1000, 1×800, 2×400 @ 3’40″/km, 2’30” recovery @ 7’30″/km;
  • Cool-Down (1.0 km @ 4’15″/km, 1.0 km @ 4’35″/km, 1.0 km @ 5’00″/km).

And here you have the HR graph:

HR acquisition of the 4000 m training (06/01/2012).
The second (09/01/2012) and the third day (11/01/2012), the chamber was simulating the 2500 m conditions: 14.8% oxygen (18.5-17.0 °C the temperatures, 72.5-60.5 % the values of humidity). Both workouts consisted in:
  • WU (3.00 km @ 4’35″/km)
  • 4×1000 @ 3’30″/km, 2’00” recovery @ 7’00″/km
  • CD (3.10 km @ 4’35″/km).

Unfortunately the acquisition of the first training is pretty bad, but the data are very clear in the second graph.

HR acquisition of the first 2500 m training (09/01/2012).
HR acquisition of the second 2500 m training (11/01/2012).

When the oxygen percentage goes under 14%, things are really difficult: the recovery time appears to be far useless (actually it isn’t, but my body said the opposite), breathing is difficult and HR cannot increase (188 out of 195 bpm, that is my max threshold) or decrease (150 bpm the lowest value between the repetitions) too much. For values of oxygen around 15%, everything is much easier and you can carry on your workout without any particular problems, even if the paces are slower than normal (the recovery time starts to be useful!).
Obviously if you train at low oxygen percentage, you should being constantly monitored: the oxygen saturation in the blood shouldn’t go under 80%, to stay distant from hypoxemia risk (the use of a pulse oximeter, a device that uses a red and an infrared light to measure indirectly the oxygen saturation of the blood, is the easiest way to stay monitored).

Blood’s oxygen saturation monitoring right after the training session.

For the record, al the data have been acquired in the Himaxx Center for Altitude Training in Berlin (Germany). If you have any question don’t hesitate to contact me! Keep on training!

Here you can find a list of my running-related posts. Now shut down the notebook and have a run! 

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