Concurrent Exercise Effects in Post-Bariatric Patients (BAR-EX)

Effect of a Concurrent Exercise Program on Muscle Quality, Body Composition, Functional Response, and Quality of Life in Individuals Undergoing Bariatric Surgery

This study aims to evaluate the effect of a 5-week concurrent exercise program (aerobic and resistance training) on muscle quality, body composition, functional response, and quality of life in individuals undergoing bariatric surgery.

This is a single-center, prospective, longitudinal, non-randomized controlled clinical trial with two groups: intervention and control. A total of 84 adults aged 18 to 60 years who have undergone sleeve gastrectomy or gastric bypass and have a medical indication for metabolic rehabilitation will be recruited.

The intervention group will complete a supervised concurrent exercise program for 5 weeks, consisting of two in-person sessions per week (10 sessions in total), while the control group will continue with usual care without participating in a structured exercise program. All participants will be assessed at two time points: baseline (postoperative week 4) and 7 weeks after baseline (after 5 weeks of intervention and 1 week of rest).

The primary outcome will be muscle quality of the rectus femoris assessed by ultrasound (echo intensity). Secondary outcomes will include body composition (bioelectrical impedance analysis), functional performance (one-minute sit-to-stand test), and quality of life (Moorehead-Ardelt II questionnaire).

Additionally, adherence to the exercise program in the intervention group will be evaluated as the percentage of attendance to supervised sessions, and its association with the magnitude of changes in outcomes will be analyzed under a dose-response framework.

The results are expected to provide clinically relevant evidence on the effectiveness of exercise in the early postoperative period and to support the optimization of metabolic rehabilitation strategies after bariatric surgery.

Study Overview

• Status: Recruiting
• Conditions: Obesity & Overweight; Post-bariatric Surgery
• Intervention / Treatment: Behavioral: Concurrent Exercise Program

Detailed Description

Bariatric surgery is an effective intervention for the treatment of severe obesity; however, the early postoperative period, characterized by rapid weight loss, is often accompanied by unfavorable changes in body composition, including loss of lean mass and decreased muscle function. These alterations may negatively affect functional recovery and quality of life. In this context, physical exercise has been proposed as a key strategy within metabolic rehabilitation; nevertheless, there is limited evidence regarding the effectiveness of short-term concurrent exercise programs initiated in the early postoperative phase, particularly in relation to muscle quality.

The aim of this study is to evaluate the effect of a 5-week concurrent exercise program on rectus femoris muscle quality in individuals undergoing bariatric surgery, compared with a control group receiving usual care. Additionally, changes in body composition, functional response, and quality of life will be assessed, and the association between adherence to the exercise program and the magnitude of observed changes will be explored under a dose-response framework.

This is a single-center, prospective, longitudinal, non-randomized controlled clinical trial. The study will include two groups: an intervention group and a control group. A total of 84 adults aged 18 to 60 years who have undergone sleeve gastrectomy or Roux-en-Y gastric bypass at BUPA Clinic Santiago and have a medical indication for metabolic rehabilitation will be recruited. Participants will enter the study at postoperative week 4, when baseline assessments will be performed.

Participants will then be allocated to either the intervention or control group according to criteria defined by the research team. The intervention group will begin a concurrent exercise program immediately after baseline assessment, while the control group will continue with usual clinical care without participating in a structured exercise program during the study period.

The intervention will consist of a 5-week concurrent exercise program combining aerobic and resistance training. The program will include two supervised in-person sessions per week (10 sessions in total), each lasting approximately 60 minutes, and one recommended weekly home-based session guided by an individualized exercise plan. Training progression will be gradual and tailored to each participant's tolerance and clinical safety criteria. Aerobic exercise intensity will be monitored using the Borg Rating of Perceived Exertion scale, while resistance training will be adjusted according to individual capacity using estimated one-repetition maximum (1RM). The home-based session will be considered complementary and will not be included in adherence calculations.

After completing the 5-week intervention, a 1-week period without supervised sessions will be observed to minimize acute exercise effects on outcome measurements. The final assessment will be conducted at week 7 from baseline. Therefore, outcomes will be measured at two time points: baseline (pre-intervention) and 7 weeks after baseline (following 5 weeks of intervention and 1 week of rest).

The primary outcome will be rectus femoris muscle quality assessed by musculoskeletal ultrasound, using echo intensity as the main indicator. Secondary outcomes will include body composition assessed by bioelectrical impedance analysis, functional response measured using the one-minute sit-to-stand test (1min-STST), and quality of life assessed using the Moorehead-Ardelt II questionnaire.

Adherence to the exercise program will be assessed exclusively in the intervention group as the percentage of attendance at supervised sessions (adherence = attended sessions/10 × 100). For descriptive purposes, adherence will be categorized as high (≥80%), moderate (60-79%), or low (<60%). Additionally, its association with the magnitude of changes in outcomes will be analyzed under a dose-response framework.

Statistical analyses will be performed using SPSS (v29). Data distribution will be assessed using the Shapiro-Wilk test. Continuous variables will be presented as mean ± standard deviation or median (interquartile range), as appropriate, and categorical variables as frequencies and percentages.

Changes in outcomes (Δ = post - pre) will be analyzed both within and between groups. Within-group analyses will be conducted using paired t-tests or Wilcoxon signed-rank tests, depending on data distribution. Between-group comparisons will be performed using independent t-tests or Mann-Whitney U tests. Additionally, repeated-measures analysis of variance (two-way ANOVA: group × time) or equivalent linear models may be used to evaluate interaction effects.

Effect sizes (e.g., Cohen's d) will be estimated to support clinical interpretation. To explore associations, Pearson or Spearman correlation coefficients will be used. Furthermore, multivariable linear regression models will be conducted to examine the association between adherence (continuous variable) and changes in primary and secondary outcomes within the intervention group, adjusting for relevant variables such as weight change during the intervention period (Δweight).

• Study Type: Interventional
• Enrollment (Estimated): 84
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: María José Pabst Perez, MSc; Phone Number: +56950023025; Email: majose.pabst@gmail.com
• Study Contact Backup: Name: Tomás Vergara Soria, Kinesiólogo; Phone Number: +56988289188; Email: tomasvergarasoria21@gmail.com

Study Locations

• Chile
  • Santiago Metropolitan
    • Santiago, Santiago Metropolitan, Chile, 7820830
      • Recruiting
      • Clínica BUPA, Santiago
      • Contact: Tomás Vergara Soria, Kinesiólogo; Phone Number: +56988289188; Email: tomasvergarasoria21@gmail.com
      • Contact: Sebastian Barrios, Kinesiólogo; Phone Number: +56984513233; Email: se.barriosv@gmail.com
      • Principal Investigator: Tomás Vergara Soria, Kinesiólogo

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria

• Voluntarily agree to participate and sign informed consent.
• Men and women aged 18 to 60 years.
• Have undergone bariatric surgery (sleeve gastrectomy or gastric bypass) at BUPA Clinic Santiago.
• Have a medical indication for metabolic rehabilitation.
• May present associated comorbidities such as insulin resistance syndrome, dyslipidemia, arterial hypertension, and/or hypothyroidism.

Exclusion Criteria

• Diagnosis of type 1 or type 2 diabetes mellitus.
• Severe musculoskeletal disorders that impair ambulation or limit participation in the exercise program.
• History of a cardiovascular event.
• Severe cardiorespiratory diseases that significantly reduce physical capacity or cause dyspnea at rest or with minimal exertion.
• Dependence on supplemental oxygen.
• Bariatric surgery-related complications, including:
• Staple line leak or fistula
• Hemorrhage/bleeding
• Stenosis or gastric narrowing/stricture
• Intra-abdominal abscess
• Hypersensitivity (as clinically determined).
• Hepatic and/or renal insufficiency.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Concurrent Physical Exercise Program; Intervention group undergoing a concurrent exercise program (aerobic and resistance training) during the postoperative period after bariatric surgery. Participants enter the study at postoperative week 4 and complete a baseline assessment before starting the program. The intervention lasts 5 weeks and includes 10 supervised in-person sessions (2 per week, approximately 60 minutes each) and one recommended weekly home-based session guided by a prescribed exercise plan. After completing the program, a 1-week period without supervised sessions is observed, and the post-intervention assessment is conducted at week 7 from baseline.	Behavioral: Concurrent Exercise Program; Concurrent physical exercise program of 5 weeks combining aerobic and resistance training in individuals undergoing bariatric surgery. The program includes two supervised in-person sessions per week (10 sessions total), each lasting approximately 60 minutes, and one recommended weekly home-based session guided by a prescribed exercise plan. Aerobic exercise is performed at moderate to high intensity, monitored using the Borg Rating of Perceived Exertion scale. Resistance training targets major muscle groups and is prescribed based on an estimated one-repetition maximum (1RM), with progression in volume and intensity according to individual tolerance and safety criteria. The program begins at postoperative week 4. After completing the 5-week intervention, participants undergo a 1-week period without supervised sessions before the post-intervention assessment.; Other Names: Concurrent Physical Exercise Program
No Intervention: Usual Care; Control group that continues with usual clinical care as indicated by the healthcare team, without participating in a structured physical exercise program during the study period. Participants are assessed at the same time points as the intervention group (baseline and at 7 weeks).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in rectus femoris muscle quality (echo intensity; grayscale units 0-255)	Muscle quality will be assessed by ultrasound as echo intensity (mean grayscale value, 0-255) within a standardized region of interest, analyzed using ImageJ, at baseline and post-intervention. Change will be calculated as Δ = post - pre.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in skeletal muscle mass (kg)	Body composition will be assessed using bioelectrical impedance analysis (InBody S10) under standardized conditions before and after the intervention. Skeletal muscle mass (kg) will be recorded at baseline and post-intervention. Change will be calculated as Δ = post - pre.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Change in fat mass (kg)	Body composition will be assessed using bioelectrical impedance analysis (InBody S10) under standardized conditions before and after the intervention. Fat mass (kg) will be recorded at baseline and post-intervention. Change will be calculated as Δ = post - pre.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Change in 1-minute Sit-to-Stand performance (1min-STST)	Functional response will be assessed using the One-minute Sit-to-Stand Test (1min-STST). The primary metric is the total number of completed repetitions in 60 seconds performed using a standard chair. Perceived exertion (modified Borg scale) may be recorded as a complementary measure.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Adherence to the exercise program (supervised in-clinic sessions)	Attendance rate to supervised in-clinic sessions at Clínica BUPA during the intervention. Adherence will be calculated as: adherence (%) = (number of attended sessions / 10) × 100. For descriptive purposes, adherence will be categorized as high (8-10 sessions; ≥80%), moderate (6-7 sessions; 60-79%), and low (0-5 sessions; <60%). Adherence ≥80% will be considered clinically acceptable.	During the 5-week intervention period (calculated at the end of the program based on attendance to the 10 supervised sessions).
Change in percent body fat (%)	Body composition will be assessed using bioelectrical impedance analysis (InBody S10) under standardized conditions before and after the intervention. Percent body fat (%) will be recorded at baseline and post-intervention. Change will be calculated as Δ = post - pre.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Change in visceral fat area (cm²)	Body composition will be assessed using bioelectrical impedance analysis (InBody S10) under standardized conditions before and after the intervention. Visceral fat area (cm²) will be recorded at baseline and post-intervention. Change will be calculated as Δ = post - pre.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Change in basal metabolic rate (kcal/day)	Body composition will be assessed using bioelectrical impedance analysis (InBody S10) under standardized conditions before and after the intervention. Basal metabolic rate (kcal/day) will be recorded at baseline and post-intervention. Change will be calculated as Δ = post - pre.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Change in rectus femoris muscle thickness (cm)	ectus femoris muscle thickness (cm) will be assessed by ultrasound under standardized conditions at baseline and post-intervention. Change will be calculated as Δ = post - pre.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Change in rectus femoris cross-sectional area (cm²)	Rectus femoris cross-sectional area (cm²) will be assessed by ultrasound under standardized conditions at baseline and post-intervention. Change will be calculated as Δ = post - pre	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Change in fat infiltration measured by ultrasound in the rectus femoris (cm)	Fat infiltration will be assessed by ultrasound in the rectus femoris under standardized conditions at baseline and post-intervention. The measurement will be recorded in centimeters (cm), and change will be calculated as Δ = post - pre.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).
Change in quality of life assessed by the Moorehead-Ardelt II questionnaire	Quality of life will be assessed using the Moorehead-Ardelt II questionnaire, a bariatric surgery-specific instrument that evaluates domains including self-esteem, physical well-being, social relationships, work, and sexuality. Total score (and domain scores, if applicable) will be compared before and after the intervention.	Baseline (pre-intervention) and 7 weeks after baseline (after 5 weeks of exercise and 1 week of rest).

Collaborators and Investigators

• Sponsor: Universidad Autónoma de Chile
• Collaborators: Clinica Bupa Santiago
• Investigators: Principal Investigator: María José Pabst Pérez, MSc, Universidad Autónoma de Chile; Principal Investigator: Tomás Vergara Soria, Kinesiólogo, Clinica Bupa Santiago; Study Chair: Sebastian Barrios Valenzuela, Kinesiólogo, Clinica Bupa Santiago; Study Chair: Luis Astete, MSc, Universidad Autónoma de Chile; Study Chair: Nicolas Arancibia Ramirez, Kinesiólogo, Clinica Alemana; Study Chair: Erika Troncoso, MsC, Clinica Las Condes; Study Director: Rosario Alonso Domínguez, PhD., Universidad de Salamanca. España; Study Director: María de la Luz Tocino, PhD., University of Salamanca; Study Director: Matias Otto Yañez, PhD., Universidad Autónoma de Chile. Chile; Study Chair: Paloma Lillo, MsC, Universidad Silva Henriquez; Study Chair: Carla Martinez Dominguez, Kinesióloga, Clinica Bupa Santiago

Publications and helpful links

General Publications

• Tamboli RA, Hossain HA, Marks PA, Eckhauser AW, Rathmacher JA, Phillips SE, Buchowski MS, Chen KY, Abumrad NN. Body composition and energy metabolism following Roux-en-Y gastric bypass surgery. Obesity (Silver Spring). 2010 Sep;18(9):1718-24. doi: 10.1038/oby.2010.89. Epub 2010 Apr 22.
• Otto-Yanez M, Torres-Castro R, Barros-Poblete M, Barros M, Valencia C, Campos A, Jadue L, Puppo H, Seron P, Vilaro J. One-minute sit-to-stand test: Reference values for the Chilean population. PLoS One. 2025 Jan 29;20(1):e0317594. doi: 10.1371/journal.pone.0317594. eCollection 2025.
• Complicaciones a largo plazo y efectos secundarios de la cirugía bariátrica: una revisión sistemática. Journal of Negative and No Positive Results, 6(6), 582-589. https://doi.org/10.19230/jonnpr.1584
• Moorehead, M. K., Ardelt-Gattinger, E., Lechner, H., & Oria, H. E. (2003). La validación del Cuestionario de Calidad de Vida Moorehead-Ardelt II. Cirugía de Obesidad, 13(5), 684-692. https://doi.org/10.1381/096089203322509237
• Gonzalez-Molero I, Garcia Arnes JA, Dominguez Lopez M, Gallego JL. [Persistent hypoglycemia in a patient with bariatric surgery]. Med Clin (Barc). 2011 Oct 22;137(11):522-3. doi: 10.1016/j.medcli.2011.01.001. Epub 2011 Mar 10. No abstract available. Spanish.
• National Institute of Diabetes and Digestive and Kidney Diseases. (2020). Efectos secundarios de la cirugía para adelgazar (bariátrica). Recuperado de https://www.niddk.nih.gov/health-information/informacion-de-la-salud/control-de-peso/cirugia-adelgazar-bariatrica/efectos-secundarios
• Muñoz, R., Hernández, J., Palacio, A., Maiz, C., & Pérez, G. (2016). El ejercicio físico disminuye la pérdida de masa magra en pacientes obesos sometidos a cirugía bariátrica. Revista Chilena de Cirugía, 68(6), 303-308. https://doi.org/10.1016/j.rchic.2016.05.007
• Alvero-Cruza, J. R., Correas Gómez, L., Ronconi, M., Fernández Vázquez, R., & Porta i Manzanido, J. (2011). La bioimpedancia eléctrica como método de estimación de la composición corporal, normas prácticas de utilización[Bioelectrical impedance analysis as a method of body composition
• Cancino-Ramírez, J., Troncoso-Ortiz, E. J., Pino, J., Olivares, M., Escaffi, M. J., Riffo, A., Podestá D, I., Vásquez M, M., & González-Rojas, L. (2019). Recomendaciones de actividad física y ejercicio en el paciente adulto sometido a cirugía bariátrica. Ejercicio y actividad física en adultos sometidos a cirugía bariátrica. Documento de consenso]. Revista médica de Chile, 147(11), 1468-1486. https://doi.org/10.4067/S0034-98872019001101468
• McIver CM, Wycherley TP, Clifton PM. MTOR signaling and ubiquitin-proteosome gene expression in the preservation of fat free mass following high protein, calorie restricted weight loss. Nutr Metab (Lond). 2012 Sep 14;9(1):83. doi: 10.1186/1743-7075-9-83.
• Pleticosic-Ramírez Y, Mecías Calvo M, Navarro-Patón R. Efectos de programas de ejercicio físico en la composición corporal, condición física y calidad de vida de personas mayores con sobrepeso u obesidad: Una revisión sistemática effects of physical exercise programs on body composition, physical fitness and quality of life in older people with overweight or obesity: A systematic review.
• Thomas-Lange J. Sobrepeso y obesidad en chile: Consideraciones para su abordaje en un contexto de inequidad social. Rev chil nutr. 2023;50(4):457. doi: 10.4067/s0717-75182023000400457.

Study record dates

Study Major Dates

• Study Start (Actual): August 11, 2025
• Primary Completion (Estimated): December 31, 2027
• Study Completion (Estimated): December 31, 2028

Study Registration Dates

• First Submitted: November 14, 2025
• First Submitted That Met QC Criteria: February 17, 2026
• First Posted (Actual): February 20, 2026

Study Record Updates

• Last Update Posted (Actual): May 4, 2026
• Last Update Submitted That Met QC Criteria: April 28, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Quality of life; Body composition; bioelectrical impedance analysis; Functional capacity; Therapeutic exercise; Muscle quality; concurrent exercise; one-minute sit-to-stand; ectus femoris ultrasound
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Overweight; Obesity; Motor Activity; Movement; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena; Therapeutics; Physical Therapy Modalities; Patient Care; Exercise Therapy; Rehabilitation; Aftercare; Continuity of Patient Care; Physical Conditioning, Human; Exercise; Resistance Training
• Other Study ID Numbers: CEC CBS /3-2025

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data (IPD) will not be publicly shared to protect patient confidentiality. Only aggregated and anonymized results will be disseminated through scientific publications or presentations.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No