The purpose of this study is to compare aquatic high intensity interval training with moderate intensity exercise training on exercise capacity in a population with rheumatic diseases.

Exercise is important to manage rheumatic diseases (RDs). In 2007, the American College of Sports Medicine (ACSM) launched a global initiative to advocate the use of exercise not only to prevent illness but to serve as a key element in the management and treatment of multiple chronic diseases. Their "Exercise is Medicine" initiative promotes exercise as a highly potent free medicine with few side effects. Despite catchphrases such as "best drug ever," few adhere to the global recommendations for weekly physical activities. Exercise is one of the therapeutic strategies that helps minimise deleterious effects on the musculoskeletal system generated by aging while preserving independence, promoting weight control, and maintaining or improving quality of life, functional capacity, and emotional well-being. However, exercises performed on the ground can aggravate joint pain and increase the risk of falls among those with RDs. Aquatic exercises are a popular adjunct treatment modality for patients with inflammatory RDs. Aquatic exercises are highly preferred by people with RDs, who are more likely to report feeling better than those treated with similar exercises on land. A preference for a water-based rehabilitation or environment may enable greater exercise compliance.

A systematic review and meta-analysis from 2011 concluded that the effects of aquatic exercise for adults with arthritis appears comparable to land-based exercise. When people are unable to exercise on land or find it difficult, aquatic programs provide an enabling alternative strategy.

Aquatic exercise programmes have been criticised for being non-progressive or low-intensive. One possible advantage of the aquatic environment is that the people with chronic diseases may be able to train at higher intensities than on land.

The effectiveness of aquatic exercise needs further comprehensive investigation, particularly related to the link between load, types of exercise, and degree of changes in physical functioning and physical fitness.

Method:

• Design: The study will be a randomized clinical trial. Patients will be recruited from different municipalities in Norway with possibilities of pool training in temperate water (between 30-34°C to be optimal).
• Intervention group: The intervention group will receive aquatic high intensity interval exercise training twice a week for 12 weeks.
• Control group: The control group will receive aquatic moderate intensity exercise training twice a week for 12 weeks.
• Sample Size Estimation: Sample size is calculated on the basis of the primary outcome variable, where a between-group difference in VO2peak of 15% or 3.5 mL∙kg-1∙min-1 is considered to be of clinical relevance. Both groups are receiving an exercise intervention, therefore we estimate a smaller between group difference to be 2.0 mL∙kg-1∙min-1. Using a reported standard deviation of change in VO2peak of 3 and 80% power to detect this difference, approximately 35 participants are required in each group. To allow for a possible 20% drop-out rate, we plan to randomise 84 patients in total (i.e. 42 per group).
• Statistical analyzes: Descriptive data are reported for variables of interest and will be analysed following the intention-to-treat principle. Prospective differences in primary and secondary outcomes and baseline characteristics between the intervention group and the control group will be assessed by t-tests for continuous and normal distributed variables and non-parametric tests for categorical variables. Multiple linear regression modelling is used to control for confounding differences between study groups.

The study will provide evidence-based knowledge for performing high-Intensity water workout in municipalities and investigates the factors that determine successful effects on physical fitness, disease activity and pain and tests the programme's utility for municipal health care services.

Inclusion Criteria:

Individuals who

• are 18 years or older,
• have a diagnosis of any kind of RDs,
• can walk with or without a walking aid and
• understand Norwegian.

Exclusion Criteria:

• medical contraindications to high intensity exercise,
• life expectancy below 1 year and
• currently participating or have participated in aquatic high intensity exercise programs or trials during the last 3 months.