Astrand Bike Test | Maximal aerobic capacity / VO2max calculation
Maximal aerobic capacity, also called VO2max, is the maximum rate of oxygen consumption during exercise and is expressed in liters per minute. Aerobic capacity is a good indicator of physical fitness and a reduction can be the first sign of disease. Ideally, it is measured in a lab with very expensive equipment, but this is rarely applied in practice as it is a very complicated process.
Therefore, Astrand and Rhyming wanted to develop a test that would allow someone to estimate the aerobic capacity of healthy individuals using a safe and submaximal ergometry test correlating heart rate with VO2max.
In order to conduct the Astrand bike test, you will need a body weight scale, a bicycle ergometer, a heart rate monitor, the score sheet to record the different heart rate values, and a stopwatch. Record the patient’s weight and resting heart rate. Ideally, the patient has recorded their resting heart rate upon waking up in the morning.
Calculate the patient’s target heart rate using the Karvonen formula. If you don’t know what that is, just read our post about this topic by clicking here.
Start the stopwatch and ask the individual to start biking with a wattage set to 100 watts for females and 150 watts for males. Make sure to record the heart rate after each minute, either by software or with a score sheet.
The goal in the first two minutes is to reach a steady heart rate close to the target heart rate, so you might have to adjust the watts in small increments during the first two minutes only. In our case, we had to raise the wattage from 150 to 160 watts to reach the calculated target heart rate of 135 beats per minute.
Motivate the patient during the test so that they complete the full six minutes. A cool down at low wattage is done for 1 minute after the test.
Before you can calculate the Vo2max, you have to take the average heart rate of minutes five and six. In our case, that’s 135 plus 125 divided by two, which is 130.
To calculate the VO2max use the nomogram. Mark the average heart rate, in our case for a male person, on the left side of the nomogram, so I’m going to make a dot at 130 bpm, and then on the right side, you see the work rate in watts. There you are going to mark the watts that your patient was cycling at, in our case, that’s 160. And then connect those two points with a straight line. And then from this middle graph, you can read the VO2max in liters per minute, which in our case is roughly 4.4 liters per minute.
If the patient is younger than 17 or older than 35 years old, you have to apply a correction factor to the VO2max, so you’re going to multiply the VO2max by this factor:
Now, there might be some confounding factors to the accuracy of this test, and just to name a few, they might be as simple as the temperature or noise level in the room where the test takes place, or the emotional state your patient is in, or the amount of sleep that they have gotten prior to testing day because all of these factors can affect the heart rate.
You can find the norm values of VO2max for different age groups in the table below:
21 OF THE MOST USEFUL ORTHOPAEDIC TESTS IN CLINICAL PRACTICE
Another way to calculate the VO2max using a submaximal test is the Harvard Step test.
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