Study Participants

The study enrolled 21 adult female participants aged 20–60, with a BMI ≥ 30 kg/m2, who underwent SG surgery in a private clinic between May 2022 and December 2022.

The participants with similar age and BMI characteristics and who were not currently engaged in any other exercise program were recruited. Those participants who were willing to join a regular exercise program assigned to Corrective Exercise Group (CEG), while those who were not willing to join a regular exercise program were included in Control Group (CG).

Initially each study group included 11 participants, one participant in CEG was lost to follow-up after the surgery. The study was completed with a total of 21 participants as 10 participants in CEG (BMI = 42.13 kg/m2) and 11 participants in the CG (BMI = 42.17 kg/m2).

Study inclusion criteria were undergoing SG surgery, not engaging in any other exercise program for CG, being able to participate in an exercise program for 3 days a week and actively participating in online communication through the WhatsApp platform for CEG. Those participants who participated in final test measurements, which took place in a single center, included in this study.

The exclusion criteria were having any disabling disease at the time of measurements, having a physical disability that would hinder participation in a corrective exercise program, having a permanent disability, having diseases of the lower extremities, having undergone orthopedic surgery or currently undergoing treatment in this regard, and being male.

Ethical approval for the study was obtained from the Marmara University Clinical Research Ethics Committee (Protocol No: 2022/13–01).

Data Collection Methods

In the week preceding the SG surgery, all participants underwent data collection, including demographic information and measurements of body composition (body fat percentage, body fat mass, body muscle mass, visceral fat score), as well as anthropometric measurements (BMI, body weight, height, waist-to-height ratio).

Static balance measurements were conducted under the supervision of a physiotherapist, both with eyes-open and eyes-closed. Additionally, the International Physical Activity Questionnaire (IPAQ), Food Frequency Form, and Food Intake Record Form were administered. At the 4th month post SG surgery, all participants repeated all questionnaires and measures except the demographic information form, using the same methods as before surgery.

Anthropometric Measurements and Assessment of Body Composition

Height measurements were taken barefoot using a stadiometer (SECA, Germany) with a precision of 0.01 mm, while body weights were measured using a body composition analyzer, TANITA MC-580, with a precision of 0.1 kg. Body composition measurements, including body mass index (BMI), body fat mass (kg), body fat percentage (%), lean body mass (kg), lean body percentage (%), waist-to-height ratio, and visceral fat score, were analyzed using a Bioelectrical impedance analysis (BIA) device, and the waist-to-height ratio measurement reported by the Tanita MC-580 was accepted as within the healthy range between 0.4 and 0.49. However, the range of 0.5 to 0.59 is considered indicative of health risks associated with high body weight, while 0.6 or higher is assessed as a higher risk of health issues [14]. Tanita displays the visceral fat percentage scale from 1 to 59. A range of 1–12 indicates healthy levels of visceral fats, 13 and above is indicative of excess visceral fat and potential health risks. During the classification of obesity, the criteria for BMI value were considered in accordance with the World Health Organization’s classification. According to these criteria, BMI values of 30 kg/m2 and above were classified as first-degree obesity, 35 kg/m2 and above as second-degree obesity, and 40 kg/m2 and above as third-degree obesity [15].

Static Balance Measurement

The objective of the static balance test is to measure changes in the position of the center of gravity over time. For this purpose, static balance performance was assessed using the isokinetic balance measurement platform (PROKIN 252, Tecnobody, Bergamo, Italy). The tests were conducted with participants standing barefoot, both with eyes-open and eyes-closed. The position of the feet was determined to be equidistant from the origin point, using the lines on the platform’s X and Y axes as references. Participants were instructed to focus their gaze on a fixed point marked at a distance of 1 m in front of them. The arms were placed adjacent to the body, while a brief resting period of approximately 40 s was allowed between test measurements, each spanning 30 s. Each measurement was repeated twice, and the average values of the results were calculated. The assessment of static balance was performed based on data including the average center of pressure in the x-axis (average C.O.P.X) in millimeters, the average center of pressure in the y-axis (average C.O.P.Y) in millimeters, lateral sway speed (medium-lateral speed) in millimeters per second, forward–backward sway speed (average forward–backward speed) in millimeters per second, perimeter used (perimeter-P) in millimeters, and the area used (ellipse area) in square millimeters. This data was utilized to derive the static balance score for each participant. Static balance measurements were taken by an expert physiotherapist who is a researcher at the Physical Therapy and Rehabilitation Center of a hospital.

International Physical Activity Questionnaire (IPAQ)

The IPAQ is a subjective instrument used to measure the physical activity levels of individuals who participated in the survey, developed by Craig in 2003 [16]. The Turkish validity and reliability of the questionnaire were carried out by Ozturk in 2005 [17]. IPAQ is used in two ways, short and long. In this research, a short form consisting of 7 questions was used. The 7 questions in the questionnaire were prepared to determine the duration of walking, moderate and high-intensity activities, and sitting times of individuals in daily life, based on days and hours. The answers given to the questionnaire determine the metabolic equivalent (ME-min) amounts of individuals in minutes as physical activity duration (minutes) and frequency (days). After the MET (metabolic equivalent) values of individuals, vigorous physical activity is calculated as 8.0 MET, moderate physical activity: 4.0 MET, low physical activity: 3.3 MET, and walking: 1.5 MET. The total MET-minutes/week = (walking + moderate intensity + vigorous intensity + sitting) MET-minutes/week is calculated with this formula. According to the MET scores, the physical activity level of the individuals is divided into groups as low (< 600 MET min/week), moderate (600–3000 MET min/week), and vigorous (> 3000 MET min/week) [17].

Food Frequency Questionnaire

Participants were queried about the frequency of consumption of each of the 39 listed foods in the food frequency questionnaire, both before the SG surgery and at the 4th month post-surgery. Food consumption frequency was categorized into seven options: daily, 5–6 times per week, 3–4 times per week, 1–2 times per week, once every 15 days, once a month, and never. Foods in this questionnaire were grouped under the titles as “milk and dairy products, meat, legumes, bread, fat, beverages, sugary products, others.” Foods were detailed under each group, e.g., whole, semi skimmed, or skimmed for milk.

Food Record

To determine the participants’ nutritional status, a 24-h dietary recall was obtained, and the analyses were conducted using the BeBiS (Beslenme Bilgi Sistemleri) 8.2 program. Examination of participants’ energy, carbohydrate, protein, fat, fiber, and fluid intake was carried out based on group-appropriate averages according to the recommendations outlined in the Türkiye Dietary Guide (TÜBER) of 2015 [18].

Diet Programs

After the SG surgery, all participants received guidance from a bariatric dietitian and were monitored online for a period of 4 months. Both groups were advised to consume two sachets of 100% isolated whey protein specially formulated for bariatric surgery participants daily for the first 4 months following the SG surgery. Protein requirements during the initial 4 months were calculated as 60–80 g/day or 1–1.5 g/kg (ideal body weight), with the recommendation of isolated whey protein powder support when necessary [19]. From the second day after SG surgery, the participants started to take a protein powder supplement suitable for consumption after bariatric surgery, which is a 100% isolated whey protein supplement suitable for bariatric surgery. This protein supplement consists of 100% isolated whey protein, probiotic fiber and a blend of 21 vitamins and minerals.

Corrective Exercise Program

Both study groups were advised to maintain physical activity (such as walking) in the first month following the surgery. The CEG group underwent a 12-week corrective exercise program starting from the 4th week after surgery. Regular exercise programs, in the form of training video material prepared by a certified exercise specialist, were provided to the CEG participants. The exercises were conducted three days a week. The adherence to the program was monitored with the photos of each session shared by the participants. A WhatsApp group was created for the CEG participants share their photos while exercising. In the event of missing the exercise session, participants were provided with makeup sessions during the rest of the week.

The design of the exercise program for the study drew upon corrective exercise resources found in the literature [20, 21]. The corrective exercise program was structured to span a total of 12 weeks, comprising 36 sessions in total (3 days/week, approximately 18.6–50 min per day). Over the course of the 12 weeks, the training program was organized into three phases: warm-up (8–10 min), main phase (26–53 min), and cool-down phase (5 min). The program was divided into two phases, each lasting 6 weeks. In Phase 1, the total duration of a single training session was approximately 39 min in weeks 1–2, ~ 43 min in weeks 3–4, and ~ 48 min in weeks 5–6. Phase 2, on the other hand, had a total duration of ~ 50.5 min in weeks 7–8, 58 min in weeks 9–10, and a total of 68 min for weeks 11 and 12. The warm-up phase was 8 min in Phase 1 and 10 min in Phase 2, while the cool-down phase lasted for 5 min. Both the warm-up and cool-down segments were focused on the targeted muscle groups for the exercises. In this program, corrective exercises utilized body weight as well as resistance bands, free weights, and textured foam rollers. The intensity of exercises involving resistance bands was determined based on the elasticity level of the bands (Thera-band; Hygenic Co., Akron, OH, USA). In Phase 1, red and green bands were used, while in Phase 2, green and blue bands were employed. To ensure the safe engagement of patients with obesity in exercises, the kilograms of free weights were determined using the one-repetition maximum (1RM) method, and the weights used over the course of three months ranged from 1 to 5 kg. Exercises were performed using body weight, resistance bands, free weights, and textured foam rollers (Table 1).

Table 1 Corrective exercise program

Control group was established from participants who indicated at the beginning of the study thay they did not want to participate in any exercise intervention after surgery. They were not subjected to any exercise program during the 12 weeks of study. They were monitored by asking them if they did participate in any exercise program during their appointments with the nutritionist.

Statistical Analysis

Descriptive statistics including mean, standard deviation (SD), median, interquartile range (IQR: 25th–75th percentiles), frequency, and percentage were presented for statistical analysis. The assumption of normal distribution was assessed using the Shapiro–Wilk test. Wilcoxon test was applied for within-group comparisons. The comparison of study groups before surgery was assessed using independent samples T-test, Mann–Whitney U test, and Fisher’s exact test. The post-surgery physical activity level was compared between CEG and CG with and Pearson chi-square test. Changes in measurements before surgery and after corrective exercise were examined using two-way (group × time) analysis of variance (ANOVA) in repeated measures, and for variables where parametric assumptions were not met, non-parametric analysis was conducted using aligned rank transformation. The Bonferroni p-value, mean difference, and standard error (SE) were reported for the pairwise comparisons when the group and time interaction was statistically significant in two-way ANOVA. Statistical significance was accepted at p < 0.05. Effect sizes were presented using Cohen’s d (small: 0.2–0.5; medium: 0.5–0.8; large: ≥ 0.8), rank-biserial correlation coefficient (\(_}}\) value indicating no difference between groups: 0; first group higher than the second group: > 0; second group lower than the first group: < 0), and partial eta-squared (η2p value indicating low: 0.01–0.06; medium: 0.06–0.14; high: ≥ 0.14) [22, 23]. Statistical analyses were performed using R software version 4.2.1 with the ARTools package [24, 25].

The power analysis was based on the parameters of the study by Picó-Sirvent et al., 2019 [26], which examined the effects of different exercise methods in individuals with obesity. The power analysis aimed to achieve 95% power, at a significance level of α = 0.05 and the effect size of d = 1.62, resulted in minimum required sample size of 11 participants per group using the G*Power (v3.1.9) software. Initially it was planned for a minimum of 11 participants in each group, the groups were completed with a total of 21 participants, consisting of CEG (n = 10) and CG (n = 11), due to one participant not being able to complete the tests.