6156
Eight healthy untrained male volunteers pedalled a cycle ergometer according to two exercise protocols: the first involved step-wise increasing physical exercise to maximal ( MPE ); the second involved prolonged (35 min) submaximal physical exercise ( PPE ) at 70% of the individual's maximal oxygen uptake .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 None