In medical studies, treatments are tested within a group of study participants. You will be given a sentence of a study report in which your task is to list the phrases that give information about the participants of the study. You should list the phrases in the same order that they appear in the text, separated by commas. If no information about the participants is mentioned, just output "not found". Relevant information about participants include: gender, medical conditions, location, number of people participating. Do not contain participant mentions without relevant information.

Q: A persistent phasic activity pattern was found in 19 of the 21 patients , high frequency phasic activity in 11 of the 21 patients .

A: 21 patients
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Q: Participating physicians were randomized to either the demonstration or the control arm , and patients were assigned to a study arm based on the randomization of their physicians .

A: not found
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Q: Antioxidant supplementation and exercise-induced oxidative stress in the 60-year-old as measured by antipyrine hydroxylates .

A:
60-year-old
****