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:A comparison between the findings of Krajcarski et al. (1999) and the rested values in the present study revealed similar effects of pre- load and added load on peak trunk flexion and extensor moments. The EMG activity of the trunk extensor muscles (TES and LES) had similar responses to the loading conditions, although the pre-trial LES and TES EMG amplitudes from Krajcarski et al. (1999) were about 6 to 13 %MVC larger than was found in the current study. Also, the peak muscle activity of the TES was about 10 %MVC lower and the IO and EO had larger EMG amplitudes during the pre-trial and trial in the Krajcarski et al. (1999) study.
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