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.

• Sedentary behavior reduction intervention for patients with colorectal cancer undergoing chemotherapy (Behavioral): A 3-week, COM-B based behavioral intervention delivered via a smartwatch, primarily targeting the interruption of 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. It comprises five core components: (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; (3) structured weekly nurse feedback 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.

Primary outcomes

• Feasibility of the intervention: acceptability [At 3 weeks after intervention start (immediately following completion of the intervention)]: Acceptability: satisfaction/ease/burden/recommendation, 5-point Likert
• Feasibility of the intervention: demand (1) Recruitment rate [At enrollment (baseline)]: enrolled participants / eligible individuals approached (%)
• Feasibility of the intervention: demand (2) Retention rate [At 3 weeks after intervention start (immediately following completion of the intervention)]: participants completing the post-intervention assessment / enrolled participants (%)
• Feasibility of the intervention: implementation (intervention adherence rate) [At 3 weeks after intervention start (immediately following completion of the intervention)]: overall adherence rate to intervention components (%)
• Feasibility of the intervention: practicality [At 3 weeks after intervention start (immediately following completion of the intervention)]: CTCAE-graded adverse events and technical faults (n)

Secondary outcomes

• Change from baseline in sedentary behavior [Three weeks before, throughout the 3-week intervention, and three weeks after the intervention.]: Sedentary time (min/day)
• Change from baseline in physical activity [Three weeks before, throughout the 3-week intervention, and three weeks after the intervention.]: Physical activity time (min/day)
• Change from baseline in symptoms at 3 weeks [Baseline and 3 weeks after intervention start]: EORTC QLQ-C30/CR29 symptom scales (0-100; higher scores indicate worse symptoms)
• Change from baseline in quality of life at 3 weeks [Baseline and 3 weeks after intervention start]: EORTC QLQ-C30 global health status/QoL scale (0-100; higher scores indicate better quality of life)
• Change from baseline in self-efficacy to reduce sedentary behavior at 3 weeks [Baseline and 3 weeks after intervention start]: Self-Efficacy to Reduce Sedentary Behavior (SRSB) Questionnaire (9-item mean score, 1-5; higher scores indicate greater self-efficacy)

Sex: All, ages: 19 Years to any

Inclusion Criteria:

1. Diagnosed with colorectal cancer (stage 2 or 3) and scheduled to receive or currently receiving chemotherapy
2. Able to use a smartwatch and respond to smartphone-based surveys
3. Able to read and understand Korean and provide written informed consent
4. ECOG performance status of 0 or 1

Exclusion Criteria:

1. Newly advised by the attending physician to restrict physical activity
2. Any injury or condition that, in the investigator's judgment, makes study participation inappropriate