Table 1 Considerations for pilot and feasibility studies of physical activity interventions

 • Balance safety, ability to complete intervention or assess outcomes, and generalizability when selecting inclusion/exclusion criteria

 • Willingness to be randomized to the non-exercise group

 • How to assess baseline physical activity level and define inclusion/exclusion criteria, e.g., at what frequency, intensity, time, and type to exclude because they are too active

• Participant and instructor fidelity

• What type of personnel is required for safe intervention delivery and participant assessment?

• Ability and willingness of the participants to understand and adhere to the exercise program

• How to measure adherence, especially for unsupervised exercise

• Adherence tends to decrease over time—what strategies maximize adherence to intervention?

• Exercise setting is accessible, does not create barriers that influence feasibility, and potential generalizability

• Difficult to create a placebo or to blind participants to group allocation

• Usual care or attention control group provides equal attention, but because of lack of blinding, may still create challenges with recruitment, retention or potential for bias

• Post-randomization drop-out rates may be unequal if control group is dissatisfied

• Emphasis on feasibility objectives and not secondary outcome measures

• Must have a priori criteria for success

• How to impute missing data if data not missing at random, e.g., drop-out because randomized to control, individuals with impaired mobility may not be able to complete performance based measures at baseline