This study was what is called a “Single Blind” study. What this means is that the research assistants needed to know ahead of time which women were in the Active Reflexology Group so they would give this group of women the real reflexology session, and which women were in the Placebo Control Group so they would give this other group of women the fake reflexology session. This means that the practitioner was not “blind” to which of the two groups each woman belonged.
The women did not know if they were in the Active Reflexology Group or the Placebo Control Group. So the women were “blind” to which group they were in. Saying it more briefly; the practitioners were not blind (they knew which group each woman was in); the women were blind (they did not know which group they were in). This makes it a single blind study.
If both the practitioners and the women did not know which group each woman was in, that would have made it a double blind study, difficult to accomplish when there are specific reflex locations involved.