The measurement of physical activity in bone density research.

Physical activity is often recommended as a method to prevent or treat osteoporosis. Nevertheless, it is difficult to interpret the research findings upon which this recommendation is made because of problems measuring physical activity. Studies investigating the bone density-physical activity association were reviewed. Physical activity was measured by participation in a specific form of exercise, questionnaire and interview, mechanical devices, and physiological markers of activity. In about half of the exercise participation studies, grouping criteria were problematic for the nonexercise or control group. Many discrepancies were found in the questionnaire and interview studies. Overall, little information was reported with respect to reliability or validity of measures, thereby hampering comparisons across studies. These measurement issues can provide nurses with a new perspective for evaluating studies that report the impact of physical activity on bone mass and other health outcomes as well.