Methods
A randomized controlled trial was conducted between
July 2009 and May 2010 in Yamagata, Chiba, Yamanashi,
and Toyama prefectures in Japan. Permission was requested
by telephone to conduct the investigation at child-care locations.
Nine (9) nursery schools and a kindergarten agreed
to participate, and 123 healthy female child-care workers
responded to notices posted at the kindergarten and nursery
schools from August to December 2009. Inclusion criteria
were for participants to be female and aged 20–64 years.
Exclusion criteria included participants who had studied
yoga or classical ballet under professional instructors, those
who had serious medical conditions or orthopedic problems
that might limit their participation, and those who were
pregnant or nursing.
The participants were assigned to a yoga group (homebased
simple yoga) and a control group at a 2-to-1 ratio
using a random-number generator. The participants drew a
small block on which random numbers were written, and
received sealed opaque envelopes with the same number.
The questionnaires and yoga DVD (if assigned to the intervention
group) were in the envelopes. Participants were
asked to complete the intervention program and questionnaires
independently. All participants provided written informed
consent.
This study was performed with the approval of the Ethical
Review Board of the Faculty of Medicine at Tokyo Medical
and Dental University.