Here is the design of a clinical trial:

Official Title: Effectiveness and Cost-Effectiveness of a Tele-Rehabilitation Program in the Treatment of Chronic Musculoskeletal Pain

Included conditions:
- Chronic Pain

Study Armgroups:
- {'label': 'Internet-Based Pain Education and Exercise', 'type': 'EXPERIMENTAL', 'description': 'Patients allocated to the intervention group will receive a login and password for individual access to the website designed for the study. The content of this intervention will include videos and animations based on pain education, physical activity promotion and general exercises. The pain education component will be based on the E-pain intervention developed by Reis et al (2017), which includes nine main features: (1) acceptance, (2 and 3) education about pain, (4) sleep hygiene, (5) recognizing stress and negative emotions, (6) increasing positive coping in lifestyle, (7) exercises, (8) communication and (9) relapse prevention. The exercise component will include general exercises aiming to improve strength, flexibility, control and coordination.\n\nPatients in this group will also receive weekly text messages and a health coaching over the telephone. The text messages will include information on the benefits of exercises, motivation, and positive messages about dealing with pain.', 'interventionNames': ['Other: Internet-Based Pain Education and Exercise']}
- {'label': 'Online Booklet', 'type': 'ACTIVE_COMPARATOR', 'description': 'The patients allocated to the control group will have access to an online booklet containing general information about self-management of chronic pain, including pain education, advice on healthy lifestyle and sleeping habits and promotion of exercises. They will also receive one phone call at week 4 and text messages once a week during the study period.', 'interventionNames': ['Other: Online Booklet']}

Interventions:
- {'type': 'OTHER', 'name': 'Internet-Based Pain Education and Exercise', 'description': 'Telerehabilitation is defined as providing techniques for therapeutic rehabilitation remotely or off-site using telecommunication technologies. Thus, our intervention will be based on the use of a website created and registered especially for the study that will have the shooting of 1 video of pain education and 1 video of exercises for the subjects of the study, totaling 8 videos of pain education and 8 exercise videos. We will provide complimentary materials along with the triggered videos and a booklet of chronic pain information. We will also make weekly calls for a health coaching service and the sending of smartphone messages for the motivation and accountability of the subjects.', 'armGroupLabels': ['Internet-Based Pain Education and Exercise'], 'otherNames': ['Telerehabilitation']}
- {'type': 'OTHER', 'name': 'Online Booklet', 'description': 'An online booklet containing information about chronic pain and suggestions for lifestyle modifications and behavior will be delivered, as well as an incentive to perform physical exercises.', 'armGroupLabels': ['Online Booklet']}

Primary Outcomes:
- {'measure': 'Pain Intensity at post-treatment follow-up', 'description': 'The primary outcome will be pain intensity measured using the Pain Numerical Rating Scale, a numerical scale of 11 domains, where 0 indicates no pain and 10 indicates maximum pain intensity.', 'timeFrame': 'Post-treatment follow-up (8 weeks)'}

Please estimate the sample size based on the assumption: 
two-sided alpha level of 0.05, loss to follow up rate of up to 15%
Sample size calculation
          We determined that a minimum of 160 individuals (80 per group) would be required to provide the trial with 90% power to detect a between-group difference of 1.5 point in a 0 to 10 Pain Numerical Rating Scale, with an estimated standard deviation of 2.75 points and two-sided alpha level of 0.05. The estimated sample size would also allow for loss to follow up rate of up to 15%.