RESTART is anchored in the Tromsø Study, which is conducted in Tromsø municipality (77,000 inhabitants) and is Norway's most long-lasting and comprehensive population study.

The project involves professionals from UiT The Arctic University of Norway, University Hospital of North Norway (UNN), Tromsø municipality, Molde University College, the Center for Morbid Obesity in Health South-East, Akershus University Hospital, Umeå University in Sweden, and the University of Jyväskylä in Finland, as well as LHL and Troms Turlag. Clinical examinations and tests are conducted at the Clinical Trial Unit at UNN and in UiT's test lab at the School of Sport Sciences. Training is conducted at the KRAFT Sports Center on UiT's campus.

RESTART builds on a pilot study, where 16 participants had statistically significant improvements in fitness (VO2max +8%), leg strength (+77kg), fat mass (-2%), and waist circumference (-4 cm) after 6 months. The RESTART model will be tested in an RCT.

A total of 110 study participants aged 60-75 years, who are inactive, have a body mass index > 30 kg/m2, and increased risk of cardiovascular disease, will be recruited from the Tromsø Study and randomly assigned to an intervention or control group. Health outcomes in the two study groups will be compared with the general population in the Tromsø Study as a reference group.

Both the intervention and control groups receive updated advice and digital strategies to promote healthy choices in the form of the Norwegian Directorate of Health's recommendations and a wrist-worn consumer wearable for continuous measurement of physical activity and energy expenditure.

In addition, the intervention group receives supervised high-intensity strength and aerobic exercise twice a week, as well as dietary and habit change advice in smaller groups. The intervention group is gradually transferred to training at the municipality's Healthy Life Center (Frisklivsentralen) and from there to self-selected training and physical activity supported by non-governmental organizations. Group activities are supported by tailored online tools to strengthen health-promoting habits.

The primary endpoint is change in fitness (aerobic capacity, VO2max) after two years. Secondary endpoints are changes in leg muscle strength and power, waist circumference, and objectively measured moderate/intense physical activity (MVPA). Participants are followed up for side effects/injuries and risk factors for cardiovascular disease. We will use questionnaires and interviews to gather information on participant experiences, health-related quality of life, mental health, and conduct a health economic evaluation.

The project activities are divided into four work packages (WP):

• Project management (WP1)
• RCT intervention and data collection (WP2)
• Communication and user involvement (WP3)
• Data analysis and scientific communication (WP4)

We plan to recruit study participants from the third quarter of 2023 with study start in the first quarter of 2024. The primary endpoint will be measured in 2026 and the development of manuals and implementation tools for Norwegian municipalities will take place in 2026-2027.

Significance

In the short term, RESTART can improve participants' fitness, muscle strength, and activity levels, reduce obesity, and thus reduce the risk of cardiovascular disease. In the long term, participants can maintain a healthier lifestyle because the intervention is integrated into municipal services, coordinated with activities offered from voluntary organizations, and supported by digital online tools. If the RESTART model is effective, we will collaborate with Tromsø municipality, LHL, and other partners to develop manuals for implementation and scale up online support tools for health-promoting habits. RESTART has the potential to become a model for disease prevention in municipalities and local communities.