The study was conducted a randomized controlled trial at the Kangwon National University. Participants were post- menopausal females with obesity referred to comprehensive Buk-gu community center, Chuncheon, Gangwon-do, Republic of Korea, from November 2017 until the end of October 2018.
The enrolment of study is shown in the flowchart (figure 1).
Recruitment and Randomization
To recruit the participants, eligible individuals were selected on the basis of information in the health records of the comprehensive community centers in the city of Chuncheon. A total of 50 eligible individuals were invited to participate in the study. After screening the eligible individuals based on their health records and inclusion criteria, they were called and invited for a visit in their comprehensive community center. When they come for the screening visit, they were interviewed to assess eligibility criteria, introducing the project, their autonomy to participate in the study, confidentiality and anonymity of collected data. After signing the written consent, they were randomized to study groups.
The participants were randomly assigned into the study groups. Random allocation was carried out using the simple randomization method, and assignment sequences were written on paper before the start of the research as either aerobic exercise group and resistance exercise group. Recruiters were blinded to the content of envelopes. Randomization was performed using random allocation software. Each participant received the next envelope in the group when she recruited in the study.
A total of 41 post- menopausal obese females volunteered to participate in this study who performed regular physical exercise (aerobic exercise and resistance exercise). These participants were randomly assigned to one aerobic exercise group (n = 21) and one resistance exercise group (n = 20). To be included in the present study, participants had to meet the following inclusion criteria: 1) post- menopausal (absence of a menstrual cycle for at least 3 months) on the date of the assessment; 2) not receiving hormone replacement treatment; and 3) not using drugs such as beta-blockers, statins, and so on. The sample size of the subjects was calculated by using ANOVA a large size of effect size of .90, a significance level of .05 and a power of .80 (G*power 3.1.2). The results of sample size per group were calculated as 15 people each group.
These participants did not participate in a regular structured resistance or an aerobic exercise program for at least four months prior to this study. All subjects who agreed to participate in this study had the study explained to them to ensure a complete understanding of its purpose and methods used. This study was performed following the ethical standard of the Declaration of Helsinki. Subjects signed an informed consent form before participation. This study was approved by Kangwon National University Review Board for Human Subjects (KWNUIRB-2016-04-009-002).
Physical characteristics of participants are shown in Table 1.
[Table 1. Characteristic of subjects]
Measurement of body composition
Physical and anthropometric variables were measured for both groups. Body mass and height were measured to the nearest 0.1 kg and 0.1 cm, respectively, using a body composition analyzer (Inbody 720, Body Composition Analyzer; Biospace, Seoul, Korea). Body mass index (BMI) was calculated as weight in kilograms divided by the square of height in meters.
Measurement of physical fitness test
Physical fitness variables were measured at baseline, 6 weeks, and 12 weeks in both exercise groups. In the evaluation of physical fitness, we utilized muscle strength, muscle endurance, flexibility, power, and agility. Grip strength was used to assess muscle strength, which measured with a digital grip dynamometer (GRIP-D 5101; TAKEI, co., Japan). The legs are slightly spread and the arms opened in a natural way. After straightening the arms at about 15° and keeping the torso upright, the dynamometer can be grabbed. Sit-up was used to assess muscle endurance, which measuring device with both hands crossed over the head and the abdominal strength used to raise the upper body for 30 seconds was measured. Sit and reach were used to assess flexibility, which measuring instrument with a posture of 90 degrees at the waist and the knees bent forward without reaching the bend. The distance (cm) at which the fingertip was pushed out was measured. Side-step was used to assess agility, which measured with a side step meter, with both feet spread out around the center line. We moved to the step with the start at both sides at a 100 cm interval, and one foot returned to the first posture beyond the right (or left) line. The number of times when both feet moved around the center line for 20 seconds was measured. Vertical jump was used to assess power, which vertical jump-measuring instrument on a mat, taking a ready position and jumping with the start. At that time, the knee was not lifted into the air, and the highest value from two trials was recorded. All tests were performed twice and the best score was retained.
Experimental exercise program
The 12-week exercise program intervention consisted of three days of aerobic exercise and resistance exercise per week (i.e., Monday, Wednesday, and Friday) in each group. The resistance exercise group had 10 minutes of warm-up activities, 40 minutes of the main resistance exercise program, and 10 minutes of cool-down. The intensity was set at 55~65% of the one-repetition maximum (1RM) with one minute of rest period between all sets and a 1-minute rest between different exercises. Main resistance exercise was trained by squat and lunge for lower, chest press and vertical fly for chest, let pull-down and long pull for back, and crunch for abdominal. The aerobic exercise group had 10 minutes of warm-up activities, 30 minutes of the main aerobic exercise program, and 10 minutes of cool-down. When aerobic exercise was performed on a treadmill, the intensity was set at 50~60% of the heart rate max (HRmax) via continuous monitoring of heart rates (Polar M400; Polar H7 WearLink; Polar Electro Oy, Kempele, Finland).
A familiarization session took place during the first week. Participants were instructed to learn how to perform each resistance exercise in a safe way. Prior to participation, all subjects were informed of the risks associated with this research study. After obtaining informed consent, subjects completed questionnaires and pre-testing prior to participate in this study. They were familiarized with study procedures during the week prior to implementation of each exercise program.
Blood collection and myokines analysis
Fasting venous blood samples were collected from all participants at baseline, 6 weeks, and 12 weeks. Fasting was maintained for 12 h. Blood samples were collected on the following day. Enough sleep and radical movement as much as possible to refrain. All samples were taken at 08:30 AM from antecubital veins. The samples were immediately centrifuged at 3,500 g at 4°C for 10min, after which serum was stored in -80°C. until further analysis. Serum levels of myokines (IL-6, IL-15, and BDNF) were measured using enzyme-linked immunosorbent assay Dueset kits (R&D systems, Minneapolis, MN, USA) according to the manufacturer's instructions as described previously.
Primary and secondary outcome measurements
The primary outcomes measured was myokines (IL-6, IL-15, and BDNF), and the secondary outcome measures were physical fitness and body composition.
Baseline and follow-up assessments
Evaluation of sexual function and inclusion criteria in post- menopausal women with obesity was performed between the groups at the beginning of the study and before the intervention. Then, before the intervention, all participants measured body composition, physical fitness, and myokiens.
Aerobic and resistance exercise groups were measured that primary and secondary outcomes when duration of the intervention at 6 weeks and end of the intervention at 12 weeks.
All results are reported as the mean ± standard deviation. All data were analyzed using SPSS version 25.0 (SPSS Inc., Chicago, IL, USA). First, we used an independent samples t-test to assess group differences in baseline variables. For the two groups (resistance exercise vs. aerobic exercise) by three stages (baseline, 6 weeks, and 12 weeks), two-way within-subject factor ANOVA was used to examine whether exercise type and time influenced physical fitness and myokines. Bonferroni test was used for post-hoc analysis. The normality of dependent variables was determined by Shapiro-Wilk tests. Statistical significance was accepted at p < 0.05.