Usability and Acceptability Study of the P-STEP Mobile Application

the System Usability Scale (SUS) at 12 weeks. The SUS a validated scale and a popular instrument for assessing perceived usability. There are 10 items in total, 5 with a positive tone and 5 with a negative tone, the response of each ranging from strongly disagree to strongly agree. The participant's scores will be transformed onto a 0-100 scale. General guidance suggests a SUS score 68 and above to be considered above average and below 68 is below average. Scores range from 0-100, a higher score indicates higher usability.

Other than the SUS, 9 usability questions relating to the specific features of the app will be asked. Participants will also be asked to provide their general feedback on the app as well as how much they used it. Individual items in the questionnaire will be summarised with percentages. Scores range from 1-5, a higher score indicates higher usability.

The User Engagement Scale - Short Form (UES-SF) is a reliable a valid questionnaire containing twelve items that measure user engagement categorised into; focused attention, perceived usability, aesthetic appeal, and reward. These categories can be calculated to get an average of the scores. An overall user engagement score can be calculated with UES-SF by adding together all 12 items and dividing them equally. Scores are presented on a scale 1-5. The items can be averaged into 4 categories or averaged for an overall score. Scores range from 0-60, a higher score indicates higher user engagement.

The short form 12 item (SF-12v2) health survey measures functional health and well-being from the participant's perspective. It assesses eight domains; physical functioning, physical role, pain, general health, vitality, social functioning, social role, mental health. Each domain contributes to two summary scores; physical component summary (PCS) and mental component summary (MCS). SF-12v2 responses will be scored and interpreted using the SF-12v2 user guide. The 8 domains will generate two summary scores; physical component score (PCS) and mental component score (MCS). Scores for the PCS and MCS range from 0-100, a higher score indicates a higher quality of life.

The RPAQ is designed to find out about a participant's physical activity in their everyday life. The RPAQ will be scored and interpreted using the scoring guidelines published by the Authors. All activities are categorised with respect to their intensity, on a scale of sedentary (<1.5), light (1.5-<3), moderate (3-6) and vigorous (>6). Each activity is scored by hours a day multiplied by the intensity of the activity. A higher RPAQ score indicates higher levels of physical activity.

Percentage of those potentially eligible who register their interest.

Percentage of participants that register interest enrol on the study.

Percentage that successfully download the app.

Percentage of participants who enrol and complete the 12-week study

Completion levels of questionnaire

Description of all cause mortality at 3 months

Description of cardiovascular events at 3 months