An Intervention to Reduce Sedentary Behavior and Promote Physical Activity in Colorectal Cancer Chemotherapy

Background and rationale: Patients with colorectal cancer undergoing chemotherapy frequently experience symptoms such as fatigue that reduce physical activity and increase sedentary time. Prolonged sedentary behavior is independently associated with adverse health outcomes, whereas replacing sitting with light-intensity activity confers metabolic and other health benefits. Reducing sedentary behavior is a feasible, low-burden behavioral target that may be more attainable than structured exercise during active treatment. Continuous, objective monitoring of activity and symptoms using a wearable device, combined with tailored feedback, offers a practical approach for this population. Objective: To develop a Capability, Opportunity, Motivation-Behavior (COM-B) based intervention to reduce sedentary behavior and promote physical activity in patients with colorectal cancer undergoing chemotherapy, and to evaluate its feasibility. Intervention development: The intervention is developed using the COM-B model and the Behavior Change Wheel (BCW). A behavioral diagnosis is conducted across the COM-B components (capability, opportunity, motivation). Relevant intervention functions (education, training, enablement, environmental restructuring) and behavior change techniques (e.g., prompts/cues, self-monitoring of behavior, feedback on behavior, goal setting, problem solving, action planning, information about health consequences, verbal persuasion about capability, social rewards) are selected and mapped to interrupt prolonged sitting. The draft intervention undergoes expert review, and content validity is assessed using a 4-point scale with reference to the Item-level Content Validity Index (I-CVI) and Scale-level Content Validity Index (S-CVI); the intervention is refined based on expert feedback. Study design and procedure: A single-group, non-randomized feasibility study with a pre-post test design is conducted. After providing written informed consent and confirming eligibility, each participant receives a study-provided smartwatch and participates in a 3-week intervention. Sedentary behavior and physical activity are recorded objectively by the smartwatch continuously for 3 weeks before, during, and 3 weeks after the intervention. The intervention comprises five core components, with the central target of interrupting prolonged sitting: when 60 minutes of continuous sitting is detected during waking hours, the participant is prompted to perform at least 1-2 minutes of light-intensity activity. The components are: (1) smartwatch-based sedentary prompts (vibration alerts after 60 minutes of continuous sitting, with guided light-activity options); (2) self-monitoring of sedentary behavior and physical activity via the smartwatch app; (3) structured weekly nurse feedback delivered by telephone (10-15 minutes; reviewing weekly activity data, reinforcing successes, and setting condition-adjusted goals); (4) weekly electronic symptom monitoring using the ESAS-r Cancer; and (5) tailored symptom-management education addressing treatment-related symptoms (e.g., fatigue, pain) as key barriers to reducing sedentary behavior. Survey-based outcomes are assessed at two time points (pre- and post-intervention) to enable pre-post comparison, scheduled to coincide with routine outpatient visits, so no additional hospital visits are required. Measurements: Objective sedentary behavior and physical activity (smartwatch); subjective physical activity (GPAQ); symptoms and quality of life (EORTC QLQ-C30 \& CR29); self-efficacy to reduce sedentary behavior (SRSB); and feasibility of the intervention (acceptability, demand, implementation, practicality). Sample size: Forty participants are enrolled. Statistical analysis: Data are analyzed using SPSS/WIN 29.0 (alpha = .05). General and clinical characteristics and all feasibility outcomes are summarized using descriptive statistics. As exploratory secondary analyses, changes in objective sedentary behavior and physical activity across the three time points (pre-, during, and post-intervention) are analyzed using repeated-measures ANOVA, and survey-based outcomes measured at two time points are compared using ANCOVA.