1. Choose a workload that will elicit a heart rate of 120-160 bpm after 5 minutes of bicycling.
2. The workload chosen should be either 50, 75, 100 or 150 watts
3. Bicycle at a constant pace (50-70 RPM) and note heart rate after 5 minutes.
This is the classical Aastrand test that has been used for more than 40 years. The formulas behind the test are based on regression analysis on several hundred subjects. The test is based on the association between heart rate and oxygen uptake and the association between workload in watts and oxygen uptake. By measuring the work and heart rate on a submaximal workload, an estimation can be made on the probable workload that could be performed at maximal heart rate.
There is however some uncertainty associated with estimation of maximal heart from age and therefore this test carries at least the same amount of uncertainty. Two thirds of the results from this test will be within a 15% deviation. Approximately 5% of the results will be more than 30% wrong.
Performed under the same conditions this test is very good for tracking changes in fitness over time or estimating the mean fitness in a population. This can be done within minimal time and effort.
Textbook of work physiology. Åstrand & Rodahl. 3rd ed. McGraw Hill 1986. Side 363-384.