Introduction Despite the beneficial exercise training-induced adaptations, the optimal exercise strategy for populations with obesity, T2DM, and knee osteoarthritis (KOA) presents with some shortcomings in the current literature. More importantly, there are no explicit exercise recommendations in the current KOA guidelines (Kolasinski et al. 2020). Hence, this pragmatic trial was carried out in a home-based setting, aiming to principally investigate the effectiveness of a 12-week home-based circuit training (HBCT) protocol on various outcomes related to knee osteoarthritis symptoms and cardiometabolic health among previously inactive, overweight/obese older adult patients with KOA and T2DM in the real world.

Methods A total of 35 participants were required for this study after considering a dropout rate of 20%. This study involved 69 patients meeting the inclusion criteria as follows: i) age \>55 years, ii) diagnosed with KOA with Kellgren-Lawrence criteria grades 2 and 3, indicating moderate KOA, which was based on radiological assessments conducted by a traumatologist, iv) chronic knee pain for more than three months, v) T2DM based on fasting plasma glucose \>7.0 mmol·L-1 and glycated hemoglobin (HbA1c) \>6.5%, vi) overweight or obesity (BMI ≥25 kg/m2), vii) receiving the standard treatment (all patients were taking diabetes medications), and viii) providing a certificate of a negative COVID-19 diagnostic test (PCR or rapid test). Patients were excluded from the study if during the intervention they demonstrated i) secondary KOA, ii) acute knee pain, iii) changes in medication, supplementation, and/or diet, iv) changes in habitual physical activity, v) intraarticular hyaluronic acid injection treatment within one year, vi) smoking, vii) dementia or any psychiatric diseases, viii) adherence to less than 90% of total prescribed exercise sessions, or ix) they tested positive for COVID-19. After informed written consent, patients were asked not to engage in any other forms of exercise and to maintain their current habitual physical activity levels and eating patterns throughout a 3-month intervention period. Thus, the participants' logbook was reviewed at each visit, aiming to ensure that no changes in nutritional behavior and physical activity patterns occurred. CON followed standard treatment (diabetes medications) without engaging in any structured exercise throughout the intervention.

Study design This is a pragmatic randomized controlled trial study registered at the National Medical Research Register (ID: RSCH ID-21-01180-KGTNMRR ID-21-02367-FUM). The patients were recruited via a poster distributed in the Orthopedics Clinic at USM Hospital. Written informed consent was obtained from all participants before the study. Those willing to participate were then selected and randomly assigned to CON or HBCT. More specifically, patients were divided into two groups performed by an independent statistician using computer-generated random allocation sequences

Assessment procedures All patients were instructed to avoid consuming caffeinated beverages and strenuous exercise 24 hours before the first visit. A total of three visits were performed and all outcomes were assessed through the three visits (baseline, weeks 6 and 12). All measurements were performed at USM Hospital. During the first visit (baseline), assessments were carried out for cardiovascular parameters \[e.g., resting heart rate (RHR), systolic (SBP) and diastolic (DBP) blood pressure\], BMI, biomarkers \[e.g., HbA1c, interleukin 6 (IL-6), and superoxide dismutases (SOD)\], rate of perceived exertion (RPE), blood oxygen levels (SpO2), and a 6-minute walk test (6MWT) to assess cardiorespiratory fitness (CRF). KOA symptoms and comorbidity score were also assessed. During the second visit at week 6 (mid-testing), an assessment of cardiovascular parameters and KOA symptoms, RPE, SpO2, and 6MWT took place. During the third visit at week 12 (post-testing), similar assessments to those conducted at baseline were carried out.