The Nurse Wishes to Conduct Research on the Number of Cancer

The nurse wishes to conduct research on the number of cancer clients who are actively involved in exercise programs following chemotherapy. To prepare, the nurse reviews similar, published research studies. The nurse knows that maturation can be a threat to internal validity of the research study. Which is the best example of maturation?

A) A heat wave occurred during the study and clients who normally exercised outside were unable to do so
B) A client developed fatigue and was unable to complete the exercise program
C) Repeated stress tests on stationary bicycles demotivated clients from participating
D) Inclusion of a former Olympic athlete in the study skewed the results