There is provided an apparatus for performing the following: acquire test results with respect to a plurality of tests performed by a test person (324) convert the test result of each test into a test score having a common unit, wherein the conversion is based on a test-specific conversion model (400, 500) and determine a daily energy reserve for the test person (324) in time domain on the basis of the plurality of test scores, wherein the daily energy reserve indicates time duration the test person (324) can perform physical and/or mental activities above a predetermined intensity threshold during a day.
