Effectiveness of a Multimodal Outpatient Supervised Physical Activity Program to Improve Tolerance and Efficacy of Chemotherapy in Adults With Breast, Lung and Colon Cancer

This study proposes a randomized, stratified, assessor-blinded, longitudinal, prospective clinical trial designed in accordance with the CONSORT guidelines. This study is justified by the need to identify effective strategies to improve chemotherapy tolerance and efficacy, as well as to reduce adverse effects and preserve patients' quality of life. The available scientific evidence suggests that multimodal physical activity programs combining cardiovascular and strength training, particularly when supervised, individualized, initiated before treatment, and maintained throughout chemotherapy, may exert a positive impact on chemotherapy tolerance and efficacy. These variables are key determinants in achieving favorable indicators and in improving the side effects caused by chemotherapy. OBJECTIVES AND HYPOTHESIS The primary objective is to evaluate the effectiveness of a supervised multimodal therapeutic exercise program, initiated before and maintained during chemotherapy, on treatment tolerance and efficacy in patients aged 35 to 65 years diagnosed with breast, lung, or colorectal cancer. The following outcomes will be compared between the experimental and control groups: * Relative Dose Intensity (RDI) * Treatment completion rate * Radiological or pathological complete response Secondary objectives include comparing the evolution of cancer-related fatigue, quality of life, muscular strength, cardiorespiratory capacity, and adherence to physical activity between both groups. Additionally, the study will explore whether tumor location, cancer stage, and age moderate the effect of the intervention on treatment tolerance and efficacy, as well as on secondary outcomes. The main hypothesis is that participants performing supervised therapeutic exercise will more frequently achieve an RDI ≥85% compared to the control group and will demonstrate improved therapeutic efficacy outcomes. STUDY DESIGN Two parallel groups will be included: Experimental Group (EG): supervised therapeutic exercise program Control Group (CG): unsupervised home-based physical activity with general recommendations Randomization will be stratified according to cancer location (breast, lung, or colorectal) to ensure balance between groups. Allocation will be generated using computer software. Outcome assessors will be blinded to group assignment. INTERVENTION The total duration of the program will be 48 weeks, including 18 weeks of active intervention during chemotherapy and 24 weeks of follow-up after treatment completion. CONTROL GROUP Participants in the control group will receive standardized verbal and written recommendations to perform therapeutic physical activity at home in accordance with World Health Organization guidelines. Recommendations will include: 3-4 weekly sessions of aerobic exercise (30-45 minutes at approximately 70% of maximum heart rate), such as walking, brisk walking, cycling, swimming, or rowing. 2 weekly strength-training sessions (approximately 30 minutes), including upper limb, trunk, and lower limb exercises at intensities between 50-80% of one-repetition maximum (1RM), consisting of 2 sets of 8-12 repetitions, using body weight and elastic resistance bands. Low-intensity joint mobility exercises. These activities will not be supervised or individualized by the research team. EXPERIMENTAL GROUP Participants in the experimental group will perform supervised and individualized therapeutic exercise sessions in specialized centers. The program will be adapted according to fatigue levels and the phase of the chemotherapy cycle. Three supervised sessions per week will be conducted: One session focused on aerobic exercise (45 minutes), combining moderate continuous training (approximately 70% of maximum heart rate) with moderate interval training (\>85% of maximum heart rate alternating with 50% of maximum heart rate), including Low-Intensity High-Intensity Interval Training (Low HIIT). Two combined sessions (50 minutes each), including: 30 minutes of aerobic exercise 20 minutes of strength training at intensities between 50-80% of 1RM, 2 sets of 8-12 repetitions, using guided machines, elastic resistance bands, and free weights. Exercises will target the main muscle groups (quadriceps, hamstrings, gluteal muscles, pectoralis major, latissimus dorsi, biceps, triceps, and lumbar musculature). All sessions will include low-intensity joint mobility exercises. PROCEDURE AND ASSESSMENTS Four assessment time points will be conducted: Baseline (at diagnosis) At the start of chemotherapy At completion of chemotherapy At 24 weeks after completion of the intervention The general areas assessed will include: Relative Dose Intensity (RDI) Radiological complete response (RRC) Dynamic and static muscular strength Cardiorespiratory capacity Cancer-related fatigue Quality of life Adherence to physical activity