Inflammatory joint disease (IJD) is associated with increased risk of cardiovascular disease (CVD) fostered by systemic inflammation and a high prevalence of CVD risk factors. Cardiorespiratory fitness (CRF) is an important health parameter and CRF-measures are advocated in routine health evaluations. CRF associates with CVD risk, and exercise modalities such as high intensity interval training (HIIT) can increase CRF and mitigate CVD risk factors. In IJD, exercise is rarely used in CVD risk management and the cardioprotective effect of HIIT is unclear. Furthermore, the clinical applicability of HIIT to primary care settings is largely unknown and warrants investigation. The primary aim is to assess the effect of a HIIT programme on CRF in patients with IJD. Second, we will evaluate the effect of HIIT on CVD risk and disease activity in patients with IJD, feasibility of HIIT in primary care and validity of non-exercise algorithms to detect change in CRF.