Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Between four and seven days after the VO2peak test, each participant returned to the laboratory to perform a test to verify the power output required to elicit the requisite VO2peak for each training session, i.e. 80% VO2peak.
Category: