The purpose of this study is to investigate the feasibility of 10 weeks of maximal strength training (MST) in patients with inflammatory rheumatic disease. As well as the effects of MST on maximal strength, rate of force developement and quality of life in this patient population.

Patients with inflammatory rheumatic diseases (IRD) such as rheumatoid arthritis, spondyloarthritis and systemic lupus erythematosus have reduced strength and muscle mass in the lower extremities compared to healthy control groups. This attenuation results in impaired physical function and health-related quality-of-life. Maximum muscle strength is an important indicator of total mortality, even when adjusted for cardiovascular health. Therefore, international guidelines encourage strength training since it has been demonstrated that resistance exercise using moderate loads (≤80% of one repetition maximum; 1RM) result in improved strength and function without worsening pain or disease activity.

In this trial patients are randomized into either a maximal strength training (MST) intervention group or a control group. The intervention period will last 10 weeks. The MST group will perform two supervised MST sessions per week, on non-consecutive days, in a seated horizontal leg press apparatus. The control group will continue with their existing activity routines. One MST session consist of 4 series of 4 repetitions maximum (4RM) utilizing heavy loads (~90 % of 1RM), separated by 3 minutes break and lasts approximately 15-20 minutes. The MST intervention follows the principle of linear progression continuously adjusting the resistance to achieve the targeted 4RM training load. The control group will be given supervised introduction to effective strength training after the intervention period.

The purpose of this intervention is to evaluate the feasibility of the highly potent MST intervention and its impact on 1RM, rate of force development (RFD) and quality of life in the IRD patient population. MST has been documented to yield almost twice the increase in both 1RM and RFD as conventional strength training performed with moderate resistance. However, it is uncertain if MST is well tolerated by the IRD patient population which is characterized by having pain, stiffness, and joint swelling. Before and after the training period, identical testing (approximately 60 min) will be performed by both intervention groups. The testing will include measurements of maximal oxygen uptake in an endurance test as well as maximal muscle strength, recorded as 1RM, and dynamic RFD both carried out in a horizontal leg press apparatus. Additionally, quality of life questionnaires will be obtained.

Inclusion Criteria:

• Inflammatory rheumatic disease

Exclusion Criteria:

• Inability to complete the testing procedures
• Pregnancy
• Not able to perform exercise intervention
• Planed surgeries or other plans during initial exercise intervention period than directly will effect the testing or training.
• unstable ischemic heart disease
• unstable aortic stenosis or aneurysm
• Less than 80% compliance of planned training sessions

The outcome assessor was blinded with regards to which intervention group the participants had been assigned.