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:MacArthur et al. (1993) found that 24 weeks of moderate- (50 60% VO2 max) and highintensity (75 85% VO2 max) training improved FAC of HIV-positive persons in each group (n 3) by 5.8 ml/kg/min and 10.1 ml/kg/min respectively.
Category: