An interventional study of Control and Exercise in Cancer, Breast Cancer and Neoplasm, sponsored by University of Castilla-La Mancha. Not yet recruiting at 1 site in Spain. Open to female participants aged 18 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-05-28.
Sponsored by University of Castilla-La Mancha · Not applicable, Interventional, and Prevention
The REFLEX study is a randomized, controlled clinical trial designed to evaluate the impact of a 16-week supervised, combined exercise program on metabolic flexibility and cardiorespiratory fitness in breast cancer survivors. While cancer treatments have significantly improved survival rates, the disease and its therapies often cause systemic mitochondrial dysfunction and muscle loss. This leads to persistent "metabolic inflexibility"-a reduced ability to efficiently switch between burning carbohydrates and fats for energy. This inflexibility, exacerbated by sedentary behavior and cancer-related fatigue, can severely diminish a patient's functional autonomy and overall quality of life. The trial focuses on assessing whether exercise can restore this metabolic adaptability in women aged 18 to 70 with stage I-III breast cancer who are currently on hormonal treatment and completed neo/adjuvant chemotherapy within the past 6 months.
The study operates on the primary hypothesis that an individualized exercise intervention will significantly improve the participants' metabolic flexibility-measured via the metabolic crossover point-and overall aerobic capacity (VO2max) when compared to a control group. Additionally, the trial will analyze secondary outcomes, including changes in cardiovascular and metabolic risk factors, muscle strength, body composition (such as bone mineral density), and patient-reported outcomes assessing quality of life, fatigue, joint pain, anxiety, and depression.
A total of 44 participants will be randomly assigned to either the intervention or control group. Participants in the intervention group will complete a 16-week program consisting of two weekly supervised sessions. Each session lasts between 55 and 85 minutes and includes a tailored combination of aerobic and strength training based on the individual's baseline fitness and metabolic thresholds. Participants in the control group. will receive standard educational materials via email, featuring healthy lifestyle and exercise guidelines from the World Health Organization (WHO) and the American College of Sports Medicine (ACSM).
To evaluate the program's effectiveness, comprehensive medical and functional assessments will be conducted at baseline, immediately after the 16-week intervention, and at a 3-month follow-up. These evaluations include submaximal and maximal exercise tests on a cycle ergometer to analyze respiratory gases, detailed blood tests, body composition imaging (DXA scans), and maximum dynamic strength testing. Ultimately, the research aims to generate high-quality evidence to optimize standard exercise recommendations for breast cancer survivors and improve their long-term health and resilience.
14,825 studies on the registry are indexed under Breast Neoplasms; 3,319 are open to participants now.
This study's planned enrollment of 44 is below the median of 72 across 10,896 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →University of Castilla-La Mancha is the lead sponsor of 107 studies on the registry; 26 are open to participants now.
Compared within Breast Neoplasms, this study's primary condition as ClinicalTrials.gg classifies it; the registry's first condition term is Neoplasms. The counts are of registry records indexed under each term, refreshed daily. How we classify →
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Adjuvant and neoadjuvant
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HbA1c
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Behavioral: Exercise
Behavioral: Control
Participants assigned to the control group receive standard care typically provided to patients in this phase of recovery. Instead of a supervised exercise program, these individuals are sent educational materials via email. This material consists of a video and official documents containing basic guidelines and recommendations for a healthy lifestyle, based on standards from the World Health Organization (WHO) and the American College of Sports Medicine (ACSM) for cancer survivors. The documents provide general instructions on physical activity, reducing sedentary behavior, and maintaining overall health habits. Like the intervention group, participants in the control group undergo all clinical and functional evaluations at the start of the study, after 16 weeks, and during a 3-month follow-up.
The intervention consists of a supervised, in-person, combined exercise program lasting 16 consecutive weeks, conducted at a specialized exercise unit. Participants attend two sessions per week, with at least 48 hours of recovery between sessions, and each session lasts between 55 and 85 minutes. The program follows a "combined" methodology, meaning every session integrates both resistance (strength) and aerobic training. To ensure safety and precision, sessions are led by a graduate in Physical Activity and Sport Sciences with specialized training in oncology, and participants work in small groups of 6 to 8 people. Each session is structured into four distinct parts: a 10-minute warm-up involving low-to-moderate intensity activity and joint mobility; a resistance training block; an aerobic training block; and a cool-down featuring static stretching for 30-40 seconds per muscle group. The resistance training portion utilizes a "full body" approach.
Change in Crossover point
Assessment of the metabolic crossover point determined through an individualized, submaximal incremental exercise test on a cycle ergometer with continuous measurement of expired gases (indirect calorimetry) to calculate substrate oxidation rates.
Time frame: 7 months
Changes in Cardiorespiratory Fitness
Assessment of cardiorespiratory capacity determined through a maximal cardiopulmonary exercise test (stress test) on a cycle ergometer
Time frame: 7 months
Change in maximal fat oxidation
Assessment of the maximal fat oxidation rate determined through an individualized, submaximal incremental exercise test on a cycle ergometer with continuous measurement of expired gases (indirect calorimetry).
Time frame: 7 months
Change in maximal carbohydrate oxidation
Assessment of the maximal carbohydrate oxidation rate determined through an individualized, submaximal incremental exercise test on a cycle ergometer with continuous measurement of expired gases (indirect calorimetry).
Time frame: 7 months
Change in Lower Body Muscular Strength
Estimated one-repetition maximum (1RM) for the leg press. Measurements will be obtained through force-velocity profiling using a linear position transducer.
Time frame: 7 months
Change in Upper-Body Muscular Strength
Estimated one-repetition maximum (1RM) for the vertical press. Measurements will be obtained through force-velocity profiling using a linear position transducer.
Time frame: 7 months
Change in 6-Minute Walk Test
Evaluation of physical performance using the 6-minute walk test.
Time frame: 7 months
Change in Lower-Body Muscular Endurance (30-sec CST)
Evaluation of physical performance using the 30-second chair stand test.
Time frame: 7 months
Change in Grip Strength
Evaluation of upper-body isometric strength using a handheld dynamometer.
Time frame: 7 months
Change in Body Mass Index (BMI)
BMI will be calculated as weight in kilograms divided by height in meters squared (kg/m2).
Time frame: 7 months
Change in Body Fat Percentage
Assessment of total body fat percentage using Dual-Energy X-ray Absorptiometry (DXA) scan.
Time frame: 7 months
Change in Lean Mass Percentage
Assessment of total lean muscle mass percentage using Dual-Energy X-ray Absorptiometry (DXA) scan.
Time frame: 7 months
Change in Bone Mineral Density
Assessment of bone mineral density (g/cm²) determined through a Dual-Energy X-ray Absorptiometry (DXA) scan.
Time frame: 7 months
Change in EQ-5D-5L Visual Analogue Scale (VAS)
Evaluation of self-rated health using the EuroQol Visual Analogue Scale (EQ VAS). The scale is a vertical line with minimum value 0 (worst imaginable health) and maximum value 100 (best imaginable health). Higher scores indicate a better perceived health outcome.
Time frame: 7 months
Change in EQ-5D-5L Index Score
Evaluation of health-related quality of life based on the EuroQol 5-dimension 5-level (EQ-5D-5L) descriptive system. This system assesses five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Responses are converted into a single index score using a valuation algorithm. The index scale typically ranges from less than 0 to 1, where higher scores indicate a better outcome.
Time frame: 7 months
Change from Baseline in Cancer-Related Fatigue (FACIT-F)
Evaluation using the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) scale. Total scores range from 0 to 52, where higher scores indicate lower levels of fatigue.
Time frame: 7 months
Change in Hospital Anxiety and Depression Scale (HADS)
Evaluation using the Hospital Anxiety and Depression Scale (HADS). The total score ranges from 0 to 42, where higher scores indicate greater psychological distress.
Time frame: 7 months
Start is estimated for Sep 2026; primary completion for Aug 2027, 11 months later.
Of 2,661 non-industry interventional studies with no phase under Breast Neoplasms, half reached primary completion within 33 months of starting (the median), counting those still running; a quarter within 16 and three quarters within 66. This study's planned 11 months is below that.
Counting every sponsor, half of 2,771 studies reached it within 33 months; a quarter within 15 and three quarters within 66.
How these figures are worked out, and which studies are left out of them.
This study is not yet recruiting, as verified in Jan 2026. You cannot join it, but the record below documents what was studied.
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