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: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.
Category: