@2024 Afarand., IRAN

---

ISSN: 2252-0805    The Horizon of Medical Sciences 2015;21(2):135-140

Background
… [1, 2] Resistance training improves body composition via an increase in net mass and body fat decrease [3] and increases muscle strength [4]. … [5] Fat tissue has a key role in lipid and glucose metabolism, and produces a large number of hormones and cytokines such as leptin, angiotensinogen, TNF-α, IL-6, adiponectin, etc. [6]. … [7]
Previous Studies
Intense resistance training leads to leptin decrease through increasing glucose uptaking by peripheral tissues in the presence of lactate, glycogen depletion increase, sympathoadrenal input increase, and acidosis increase [8, 9]. Following the exercises, body fat and fat weight decrease due to the misbalance between energy intake and energy consumption, which leads to leptin decrease [10]. … [11, 12] Aerobic exercises reduce leptin levels or make no change in it [13]. Research on the effects of resistance training, a strong anaerobic stimulus which have neural, metabolic and hormonal different responses [8], on the concentration of leptin is very limited and contradictory. … [14-17]
Aim(s)
The aim of this study was to evaluate the effect of 6-week resistance training on body composition, serum leptin and muscle strength in non-athletic men.
Research type
This is a quasi-experimental research.
Research society, place and time
Non-athlete male students living in dormitories of the University of Zanjan (Iran) who were enrolled in the academic year 2012-2013, were studied.
Sampling method and number
22 students, who were not in the last 6 months of regular exercise, voluntarily participated in the study. All participants were selected through purposeful sampling. Entry requirements were: lack of regular exercises for at least 12 months, no doping, no history of cardiovascular and lung diseases and lack of infectious diseases for at least one month before the start of the study.
Used devices&materials
The subjects were randomly assigned into two groups as training (n = 12) and control (n = 10). Health Questionnaire was used to determine the health status of the participants; wall stadiometer (Seca; Germany) was used to measure height, and a digital scale (Seca; Germany) was used to measure body weight of the participants. The participants' body composition (fat percentage and lean mass percentage) in the fasting status and before physical activity was evaluated through measuring the thickness of subcutaneous fat of the thoracic, abdominal and thigh using a caliper (Yagamy; Japan), on three rotary occasions in every area of the right side of the body and with the closest number, calculated by Jackson and Pollock equation [18]. Due to the subjects being beginners, maximum strength was evaluated both in bench press and leg press exercises through indirect method using Brzycky equation (Maximum One-repetition = Pasted Weight (kg)/(Number of Repetition ×0.0278)-1.0278) [18]. First blood sample was taken after 12-hour fasting, if there was no vigorous physical activity 24 hours prior to sampling, sitting and from antecubital forearm vein (5ml). In the post-test, blood sampling was done in the same situation and 48 hours after the last training session. Leptin serum was measured using ELISA method and commercial kit (DBC Company; Canada) with 0.4ng/ml sensitivity and 6.5%coefficient change percentage. Then the sample were divided into two groups including training (n = 12) and control (n = 10) homogenized according to statistical procedure (according to data from the pre-test).Subjects in training group received 6-week resistance training, 3 sessions per week, according to Kramer and Ratans protocol [19]. Each exercise session was about one hour. The subjects in the control group continued their usual activities without interference. Nutrition of subjects during the study was similar. Items measured at pre-test were also measured at post-test in the same way and at the same time. Since the results of Kolmogorov-Smirnov test showed normality of data distribution, Independent T-test was used to compare intra-group changes of variables, and Paired-T test was used to compare variables within the groups. All statistical analysis was performed using SPSS 16 software.
Findings by Text
Demographic characteristics of the subjects are presented in Table 1. The intergroup comparison of variables showed that 6-week strength trainings did not lead to significant changes between control and training groups in leptin levels, body fat, lean body mass and upper body strength. Nevertheless, these changes were statistically significant in lower body strength. In addition, comparison between intra-group variables showed significant changes in bench press and leg press strength only in training group (Table 2).
Main comparison to the similar studies
Resistance training increases body composition and muscle strength [3]. Resistance training increases muscle strength and reduces body fat through increasing testosterone hormone which is an anabolic hormone [7, 20]. 6-week resistance training did not result in significant changes in leptin levels, body fat, lean body mass and upper body strength. The results of this study are consistent with the findings of some studies [13-15, 21-23], while they are not in accordance with some other studies [16, 17, 24-27]. Reduction in leptin levels is in line with the decrease in the thickness of subcutaneous fat and BMI [16, 24]. Resistance training has reduced plasma leptin concentration [17, 27]. Regular physical activity is likely to be effective on serum leptin level reduction, if it is implemented in long-term period [25]. 16-week resistance trainings in obese postmenopausal women has been accompanied with no changes in leptin levels (in women who had no weight loss) and with leptin level reduction (in women who had 36% weight reduction) [25]. In the current study, participants' BMI was about 22kg/m². A short-term resistance training session, even without changes in body fat, has been effective on serum reduction [26, 28]. After a resistance training session, leptin concentration was significantly decreased compared to control group, 9, 12 and 13 hours after the exercises [26]. After 3-week resistance training, there has been a significant reduction of leptin independent of BMI and body fat [28]. … [29, 30] It seems that the exercise program used in this study did not have necessary intensity to influence the level of leptin. Inter-group differences were significant in lower body strength. In addition, intra-group changes in chest press and leg press strength were significant in training group. Despite of the relatively large difference between pretest-posttest (delta) changes in the upper-body strength in two groups, the increase in upper body strength was not significant in training group based on the Independent T-test. There was no significant increase in lean body mass. In the first weeks, the increase is due to neuromuscular adaptations as a result of learning, neuromuscular coordination and the ability of the brain in recruiting motor units and in the next few weeks, hypertrophy plays a major role to increase the power [31, 32]. In the present study, there was an increase in the power, but there was no significant increase in the lean body mass. There was no significant change in body composition of subjects. The intensity of exercise is one of the key factors to change body composition [17, 20]. In this study, the extent of training was not likely to cause significant changes in body composition of subjects.
Suggestions
Further studies should be conducted carefully controlling the intervening factors.
Limitations
Lack of measuring changes affecting the status of anabolic hormones, small sample size, no calculation of the received calorie and expenditure of energy in the resistance training program and in some hormones were of the limitations of this study.
Conclusions
Without affecting the body composition (lean mass and fat percentage) and leptin serum, 6-week resistance trainings might significantly increase the muscle strength in non-athletic men.
Acknowledgments
All those participated in this study are appreciated.
Conflict of interest
All the subjects confirmed consents.
Ethical Permissions
Non-declared
Funding Sources
This study has been funded by the corresponding author.

TABLES and CHARTS

Show attach file