Quoting the study :
"Our study design is composed of both prospective and > cross-
sectional features (Fig. S1). The prospective aspect of the study
involved enrolling 26 healthy subjects who had no prior RR-
eliciting experience (Novices, N1) which served as their own
controls. They then underwent 8 weeks of RR-eliciting training
(Short-term Practitioners, N2). The cross-sectional aspect of the
study involved enrolling another 26 healthy subjects who had
significant prior experience of regular RR-eliciting practice for 4–
20 years (Long-Term Practitioners, M) to be compared with
novices either before or after their 8-week RR training."
Then
"We collected blood samples and biological measures when study
subjects attended morning laboratory sessions, during which M
and N2 listened to a 20-minute RR-eliciting CD and N1 listened
to a 20-minute health education CD (control)"
So if I understand correctly, it means the "novices" went through :
* a period of time during which their blood was tested before, shortly after and then later after doing basically nothing
* a period of time during which their blood was tested before, shortly after and then later after doing meditation/yoga/whatever
The same experiment being done with people with more experience.
I'm no researcher, so I'm curious what would be an acceptable control group for this experiment ?
A group of novices that would gets their blood tested before/after doing nothing at all (sleep ? another activity ?)
Is it the fact that the same person serves as its own control (by doing different experiments over time) that invalidates it ?