Here is the design of a clinical trial:

Official Title: Improved Cardiovascular Health for Patients With Inflammatory Joint Diseases

Included conditions:
- Spondyloarthritis
- Rheumatoid Arthritis
- Psoriatic Arthritis

Study Armgroups:
- {'label': 'High-intensity exercise (HIIT)', 'type': 'EXPERIMENTAL', 'description': 'Usual care; CVD risk assessment, lifestyle advice (heart-healthy diet, regular exercise, weight management and non-smoking) and relevant medication.\n\nThe 12-week intervention is carried out as individual or group sessions with maximal 4 patients, supervised by physiotherapists in primary health care. The HIIT group complete two weekly HIIT sessions and a third weekly session with exercise at moderate intensity. Exercise is tailored to each individual to provide the same relative exercise stress and to ensure progression. Target exercise intensity is tracked by a heart rate monitor.\n\nIndividual exercise session are recorded in a training diary. Succeeding the intervention, a questionnaire will be distributed to patients in the HIIT group. Semi-structured interviews will target physiotherapists supervising HIIT and 5-7 patients in the HIIT group.', 'interventionNames': ['Behavioral: High-intensity exercise (HIIT)']}
- {'label': 'Usual care', 'type': 'NO_INTERVENTION', 'description': 'Control group participants receive the same treatment as usual care; CVD risk assessment including lifestyle advice (heart-healthy diet, regular exercise, weight management and non-smoking) and relevant medication. Control group participants are invited to a physiotherapist-led theoretical and practical HIIT session following study completion.'}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'High-intensity exercise (HIIT)', 'description': '12 week intervention: Two weekly sessions of 35-40 min exercise: 10 min warm-up, followed by 4x4 min at 90-95% peak heart rate (HRpeak) interspaced by 2-3 min active breaks at 60-70% HRpeak and a third weekly session with continuous exercise for a minimum of 40 min at moderate intensity.', 'armGroupLabels': ['High-intensity exercise (HIIT)']}

Primary Outcomes:
- {'measure': 'Peak oxygen uptake - VO2peak ml/kg/min', 'description': 'VO2peak, expressed in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min). VO2peak will be measured by a Cardiopulmonary Exercise test (CPET) on a treadmill, using electrocardiogram (ECG), breath-by-breath gas analyzing system, blood pressure (BP) monitor, pulse oximetry, and Borg rating of perceived exertion', 'timeFrame': '3 months post baseline'}

Please estimate the sample size based on the assumption: 
Using a reported upper bound of 4.5 on the SD of change in VO2peak and 80% power to detect this difference, with a 20% drop-out rate.
Sample size
        Sample size is calculated on the basis of the primary outcome variable, where a between-group difference in peak oxygen uptake (VO2peak) of 3.5 mL/kg/min is considered to be of clinical relevance.20 Using a reported upper bound of 4.5 on the SD of change in VO2peak34 and 80% power to detect this difference, approximately 25 participants are required in each group. To allow for a possible 20% drop-out rate, we plan to randomise 60 patients in total (ie, 30 per group).