The goal of this randomised controlled trial study is to investigate whether exercise (brisk walking, equal to 13 on a rating of perceived exertion scale; somewhat hard) can be used as an adjuvant therapy for people living with axial spondyloarthritis and taking biologic medications to further improve their quality of life and lower their symptoms and disease burden. The main questions it aims to answer are: Does a 12-week structured home-based aerobic exercise intervention have a favourable effect on markers of immune-mediated inflammation and symptom severity? As a secondary aim and outcome, this study will investigate: * The acceptability of this intervention using questionnaires with free text boxes and one-to-one semi-structured interviews in a subset (50%) of participants (Q-ExTASI-B substudy). * The effect of the home-based intervention on circulating markers of cardiometabolic health, anthropometrical measures, and immune markers that associate with systemic inflammation. * The effect of the home-based intervention on objective measures of physical function and exercise tolerance The study will compare the data of a healthy group with that of people living with axial spondyloarthritis. Within the patient population, 20 of the individuals will be allocated to the exercise group (randomly), and 20 will be allocated to the usual care group. In the exercise group, participants will be asked to do 30 minutes of brisk walking five days a week for 12 weeks, and they will be visiting Loughborough University every four weeks to provide blood samples and fill out questionnaires. Participants in the usual care group will continue with their current care routine and will visit the study site to provide blood samples and questionnaire data every 4 weeks. The data from all axSpA patients will be compared to healthy controls, and subgroup analysis will be conducted to investigate the difference between the exercise group and the usual care group.