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:heavy exercise intensities (Krustrup et al. 2009; Ozyener et al. 2001; rossiter et al. 2002) whereas studies that measured EPOc magnitude and duration to the point at which resting metabolism was restored found that both EPOc magnitude and duration showed significant differences with changes in exercise intensity (Short and Sedlock 1997; Smith and Mc naughton 1993).
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