## 4 Discussion  
This study assessed the perspectives of oncology physiotherapists on exercise immunology in oncology physiotherapy. Seven emerging themes were identified: the construct 'immune functioning', symptoms related to decreased IF, influences on IF, tailored physiotherapy treatment, treatment outcomes in oncology physiotherapy, the oncology physiotherapists within cancer are and measurement and interpretation of IF.  
Participants' definitions of and associations with the construct IF generally aligned with current literature [8]. Interestingly, diverse opinions existed regarding the most influential factors affecting IF and the physiotherapist's role in addressing them: While exercise, nutrition, stress, and sleep were commonly linked to IF, variations existed in how these elements were integrated into clinical reasoning. Some participants discussed these factors with patients, actively incorporating them into treatment plans. Notably, these participants had often followed courses or did personal research on exercise immunology. Others did not discuss the topic of IF with their patient since they did not feel confident regarding their knowledge of the topic. This can be explained by the novelty of this subject within physiotherapy. Existing Dutch and international oncology physiotherapy guidelines lack guidance on integrating the immunological effects of exercise [6,7].  
Previous research showed that the effects of exercise on the immune system interact with other lifestyle factors [18; 19; 20]. This highlights the need for a multidisciplinary approach for treatment, as well as a better fundamental understanding of the interaction of these effects. Interestingly, a recurring theme in this study was collaboration of oncology physiotherapists in multidisciplinary networks and teams including, for example, nurses, dieticians, and psychologists. This aligns with a growing recognition of the importance of a comprehensive approach in healthcare for patients with cancer, addressing not only physical function but also overall well-being and quality of life [21; 22; 23].  
The findings also underscore the importance of a personalized approach in oncology physiotherapy. The heterogeneity of patients with cancer undergoing cancer treatment necessitates tailored exercise interventions that account for each patient's unique circumstances and needs [7]. This approach reflects the core tenets of person-centered care, which emphasize respect for patients' values, preferences, and active participation in their care [22; 24]. Continuous tailoring is crucial due to significant variations in patients' physical conditions between training sessions. Oncology physiotherapists play a pivotal role in monitoring patients, adjusting training parameters (type, frequency, intensity, timing, and duration), and making real-time decisions to optimize patient outcomes. Participants recognized the potential value of incorporating exercise immunology into their clinical reasoning to further enhance decision-making--such as optimizing the timing of training sessions during chemotherapy--thereby reinforcing a dynamic, evidence-informed, and person-centered model of care.  
This study showed that oncology physiotherapists tailor their training based on various factors, including patient-reported symptoms such as dizziness and pain, observations such as changes in heart rate or color of the skin, as well as their 'gut feeling'. Some common symptoms such as fever, fatigue, and pain were specifically associated with decreased IF by participants. Importantly, IF was rarely utilized as parameter or outcome on itself. Participants often emphasized that they were not familiar with a measurement instrument for physiotherapists to assess and interpret IF. Future research should therefore explore whether a non-invasive measure of IF could be a facilitator for oncology physiotherapists to incorporate the subject IF in their clinical reasoning.