30 participants were participated in our study according on inclusion criteria: lack of prohibition of sports activities by the physician and body mass index 25-30 kg/m2 and inactive lifestyle for at least 2 years. participants were postmenopausal women who were familiar with swimming skills. All participants completed the Medical Assessment and Physical Activity Readiness Questionnaire. The participants, according to the Helsinki Declaration [18], were informed about the whole protocol of the study. Then, they completed the informed consent form and were assured that their information would be kept confidential. The participants were randomized into a high-intensity interval swimming training group (HIIT: n=15, age 55.53 ± 2.92 years; BMI 26.90 ±2.4 kg/m2), and a control group (CON: n=15, age 55.93 ± 2.46 years, BMI 26.53 ± 2.33 kg/m2). The randomization process separated the participants in two groups and then defined the type of intervention. Both stages were carried out in random and blinded conditions. The study was started with preliminary testing and familiarization sessions. Then HIIT group took part in high intensity interval swimming training with 3 training sessions per week for 8 weeks, while CON group had no training or lifestyle changes during the same period. Dietary intake was not controlled in training period and there were no dropouts from the study.
The HIIT group completed all of 24 experiment design training sessions during the 8 weeks intervention period. Each session consists of 6-10 30s front crawl intervals which disperse by 2 min of passive recovery [19]. The 1th, 2th and 3th weeks were included 6 intervals, the 4th, 5th and 6th weeks were included of 8 intervals the 7th and 8th weeks were consisting of 10 intervals. The 24 HIIT training session occurred in an indoor pool. RPE and HR of participant was monitoring during training sessions. Each HIIT training session started with 10 minutes warm up that was include: pool walking and jogging, stretching and slow swimming. The training sessions began with 10-minute warm-up period that consist of pool walking and jogging, wall stretches and slow swimming (table 1).
Table 1
The training program for participants during study
weeks
|
Days in week
|
Warm up
|
Intensity
|
Cooldown
|
1
|
3 days in week
|
10 minutes
|
6 repetition of fast 30-second swimming repetitions, with 2-min intervals of active rest between repetitions
|
10 minutes
|
2
|
3
|
3 days in week
|
8 repetition of fast 30-second swimming repetitions, with 2-min intervals of active rest between repetitions
|
4
|
5
|
6
|
3 days in week
|
10 repetition of fast 30-second swimming repetitions, with 2-min intervals of active rest between repetitions
|
7
|
8
|
All participants were required to complete the training program. Fail to complete three HIIT sessions would result in exclusion from the study. participants reported their RPE following the 1th, 2th, 4th, 6th, 8th and 10th intervals in each training sessions and their heart rate were also monitored using a Polar H10 monitor during one session in 0th, 2th, 4th, 6th, 8th week at the same intervals of RPE data to determine adequate changes in their heart rate. also, in each session the peak heart rate and the swimming distance was noted. Average mean and peak HR in HIIT training session in the 0th and 8th weeks was 143.40±2.19 and 152.13±2.38 bpm, respectively, corresponding to 87.20±.79 and 92.52±1.5 % HRmax, respectively (figure 2). Ten minutes of cool down which include of stretching and locomotor activities were used at the end of training sessions.
No training was performed 48 h before testing. resting blood sample were taken from an antecubital vein under standardized conditions between 7 and 8 a.m. after a 12 hours overnight fasting. The blood samples were centrifuged for 30 s to collected the plasma. Irisin was measured by ELISA kit (Hangzhou Eastbiopharm Co, cat number KE90905). Blood samples were also treated to measure insulin and lipid profile level. Serum insulin level were assayed by ELISA technique. Also, TG, TC, LDL-c and HDL-c were assayed using enzymatic method kit (Pars Azmoon, Tehran, Iran) by RA-1000 American biochemical auto analyzer machine. an automatic BP monitor (HEM-709; OMRON, IL, USA) was used to determine systolic and diastolic blood pressure according to standard methods [20] every 30 min during 2 h rest period.
Data are reported as mean ± SD and Shapiro-Wilk test was used to evaluated the normality of data. Also sample t-test was used to compare baseline and endpoint continuous values within groups. Student’s independent t-test was performed to comparison between HIIT and control groups. In addition, two-way ANOVA performed to comparison between and within subjects’ factor. P value <0.05 was determined to be statistically significant and SPSS was used to analyses data and graph pad prism software was used to creating graphs.