A woman has been in labor for the past 8 hours, and she has progressed to the second stage of labor. However, after 2 hours with no further descent, the provider diagnoses an "arrested descent." The woman asks, "Why is this happening?

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.