Appendix.

Suggestions for future research projects and proposal regarding how data should be assessed and reported

Investigation	Reason	How to assess	How to report
Compare pedometer and accelerometer readings in patients undergoing TJA	To prove that accelerometers may be more accurate because they assess each step taken and allow calculation of intensity	Data sampling with pedometers and accelerometers in the same patient; comparison with actual steps taken; tests at different walking speeds	Steps/day Sampling time Separately for patients undergoing THA and those undergoing TKA Numbers of females and males, age, weight, and height Mean, SD, and range for each subgroup
Compare the accuracy of different pedometer and accelerometer models in patients undergoing TJA	Large differences between models have been shown before; to determine the most appropriate models for patients undergoing TJA	Data sampling with pedometers and accelerometers in the same patient; comparison with actual steps taken; tests at different walking speeds	Steps/day Sampling time Separately for patients undergoing THA and those undergoing TKA Numbers of females and males, age, weight, and height Mean, SD, and range for each subgroup
Identification of potentially useful habitual physical activity questionnaires for patients undergoing TJA	Administration of questionnaires is more feasible in the daily routine; they may allow for additional assessment of activities not suited for pedometer or accelerometer use (eg, swimming)	Literature review of habitual physical activity questionnaires	Suitable questionnaires should allow quantification of physical activity in internationally comparable units such as kcal or METs They also should allow calculating the proportion of patients meeting or not meeting current physical activity recommendations
Assessment of usefulness of different habitual physical activity measures in patients undergoing TJA; criterion validation in the target group	Questionnaires differ in length and administrative burden; under- or overreporting might be present; criterion validation in the target group (ie, patients undergoing TJA) is necessary to prove that any questionnaire really measures what it intends to measure	Administration of different questionnaires together with traditionally used outcome measures such as the WOMAC or Oxford scores; calculation of response rates and assessment of patient judging; correlation with objective measures such as doubly labeled water, oxygen uptake, or accelerometers	Sampling time Separately for patients undergoing THA and those undergoing TKA Numbers of females and males, age, weight, and height Mean, SD, and range for each subgroup Questionnaire results in kcal or METs Proportion of patients meeting current physical activity recommendations Correlation coefficients between questionnaires and objective measures

TJA = total joint arthroplasty; kcal = kilocalories; MET = metabolic equivalent of task (1 MET corresponds to the energy expenditure of sitting quietly for 1 minute; 3.5 mL O²).