It will be a randomized, double-blind, sham-controlled study. The trial will be performed at a single-center, Hospital Central Norte PEMEX, a tertiary center with a gastrointestinal endoscopy fellow trainee program with more than 10 years of experience. This trial will be conducted in accordance with the most recent version of the Declaration of Helsinki. The trial has been approved by the local ethical committee and research committee with the number DCAS-SSS GSM-HCN-INV-0043-2022. Written informed consent will be obtained from all the patients before participation. This manuscript will be reported in accordance with CONSORT guidelines.

Prior to the procedure, age, sex, height, weight, waist circumference (WC), body mass index (BMI), and colonoscopy indication of all participants will be recorded. Once enrolled, patients will be randomized to either the abdominal binder (AB) group or the sham binder (SB) group in a 1:1 ratio. Randomization will be performed using a web-based computer system (Research Randomizer, Geoffrey C. Urbaniak and Scott Plous) by an independent statistician who had no other intervention in the study. An independent operator will print the randomization number and group for each participant (either the AB or SB group) in individual cards, which will be hidden in a locked black box by the same independent operator. Only the nurse, who will fit the abdominal binder to all the patients in a private space, will have access to the cards. Randomized data and cards will be concealed to study coordinators, endoscopists, clinical staff, and participants.

The abdominal binder to be used for the patients allocated in the AB group was the Revive 3-in-1 Postpartum Recovery Support Belt (KeaBabies® Co., CA, USA). Its price is $29.96. The device is manufactured in two sizes, One Size and X-Large. For the patients with a waist circumference \>110 cm it will be used the X-Large model. The three belts that make up the binder will be fitted to all the participants. Once placed, the binder will be adjusted to be located between the subcostal border and the anterior superior iliac spine. The participants will be asked to confirm that the binder is fastened tightly but not uncomfortably. For the participants in the SB group the same binder will be fitted, but once the patient is sedated, it will be loosened by the same nurse. The participants will wear a non-transparent gown over the binder so that it will not be visible to the endoscopists.

Bowel preparation with 4 L of polyethylene glycol solution in split-dose (2 L in the afternoon of the day before and 5 h before the colonoscopy) will be used in all the participants. In this trial, all colonoscopy procedures will be performed by two second-year fellow trainees in gastrointestinal endoscopy.

A standard video-colonoscope (EC-3890Li, PENTAX Co., Tokyo, Japan) will be used. All the patients will be placed in the left lateral decubitus position. Manual abdominal compression and postural change will be conducted by a technician when required by the endoscopy trainee or the attending endoscopist. Endoscopist or anesthesiology will be allowed to remove the binder at any time during the procedure if they resolve it was necessary for safety. Air insufflation will be used during colonoscopy.

Sample size was estimated over the primary outcome of the study based on pre-experimental data estimation and previously reported CIT and SD of similar studies with fellows' participation. It was calculated that 142 participants were needed to detect a 60-second difference in CIT (SD 110 sec), with 90% power and two-side alpha 0.05. Moreover, it was also calculated based on the frequency of ancillary maneuvers, using pre-experimental data estimation and literature data. It was found that 186 participants (93 per group) were needed to detect a 20% reduction in the use of ancillary maneuvers, with 90% power and two-side alpha 0.05. As a preventive measure in case of withdrawal or exclusion, the sample was expanded by 10%, a total of 206 patients, 103 in each group were included in the study.

Descriptive statistical analysis, including mean, mode, and frequencies will be performed for the description of the study data. The comparative analysis of the quantitative data will be previously subjected to normality evaluation by the Shapiro-Wilk test and graphical analyses. According to the normality, data comparative analysis will be performed either with a two-way Student's test or U Mann-Whitney test. For the comparative analyses of the categorical data (e.g., manual abdominal compression, postural change, need for intervention by the attending endoscopist) will be used chi-square or Fisher' exact test. A p value of \<0.05 will be accepted as statistical significance. Statistical inferential analysis will be performed using RStudio® (R Core Team v.1.2.5033; R Foundation for Statistical Computing, Vienna, Austria) and SPSS® Statistics for Windows Version 23.0 (IBM Corp., Armonk, NY, USA). RStudio® (R Core Team v.1.2.5033) will be also used for drawing graphics. The study biostatistician (SA) will be blinded to the randomization phase and recollection data process.