The effects of the zinc supplementation and weight trainings on the testosterone levels

Total zinc content in body is approximately 1,5 gram in women while it is 2,5 gram in men [18]. Zinc moves in and out of the cells through transport proteins. These transport proteins takes zinc and protects cells from zinc toxicity and enables sufficient amount of zinc to be obtained. Common zinc transporting proteins are ZIP proteins, ZnT4 proteins and metallothionein [19].

While testosterone is produced by main testis in male, its primary source is the adrenal gland and ovaries in female. In male, approximately 7 mg testosterone is produced daily under the control of hormonal feedback [23]. Although tes- tosterone is swung regularly in young men, it has been asserted the testosterone levels decrease with increasing age in male [17].

Testosterone is a steroid-type hormone produced out of cholesterol. Steroid hormones that can be produced in adrenal glands, gonads and placenta play a significant role in the growth, development and maturation of the brain [5, 20].

In conclusion, it has been demonstrated that testosterone has regulatory effects in sexuality, aggression, sleeping control, cognitive functions, visual spatial skills, endurance and mood in male [14, 17]. It is known that androgens which have growth and virilization stimulating effect are widely used illegally in order to increase the muscle structure and accordingly the performance of the athletes because of their anabolic effects occurring when its primary therapeutics usage forms the therapy of hormone replacement [2]. However, its dosage used in order to develop muscles and improve performance of the athletes may be higher than required dosage [10].

Testosterone is a hormone that has effects on the skeletal muscle. The most prominent effect of testosterone is the increase in muscle mass and glycogens concentration. In a study conducted on that issue, it has been set forth that short term high-intensity tiring training enables increase in total testosterone levels of the athletes and this increase is observed to continue more distinctively and significantly in cyclists than the football players. That demonstrates that cyclists may be affected by the maximal resistance exercises [1].

Similarly, in the study of [22], the male and female subjects perform 6 sets squat exercises for 10 times in order to identify the muscle andro-genous and glucocorticoide receptors of the acute resistance exercises. While free testosterone levels increase significantly in both genders through exercises, total testosterone levels increase in only male subjects. The [8] subjects 624 voluntary male ranging in age from 25 to 85 to a short term highly heavy exercises in cycle ergometer and state that the serum testosterone levels of the participants are not affected.

In parallel with this information, in this study it has been aimed to examine the effects of 6-week zinc supplementation applied with weight trainings on the free and total testosterone levels. The paper is equal contribution of all authors.

Materials and Methods. The Subjects: 40 healthy male subjects ranging in age from 18 to 22 participate in the study. The subjects are equally divided into 4 groups. The pre-test and post-test model is used. The population of the study comprises of the students of Adiyaman University who do physical exercises actively in different branches and the ones who do not do sports. All of the subjects stay in the dormitory of Adiyaman University and are liable to the same diet.

• 1^st Group: Control Group (S)

• 2^nd Group: Sedentary Gorup which is only supplied with Zinc (Z)

• 3^rd Group: Training Group which is supplied with Zinc (ZT)

• 4^th Group: Athletes’ Group who performs the weight training (T)

The 2nd and 3rd group are supplied with zinc (2,5–3 mg /kg /day) in addition to the normal diet for 6 weeks. In addition, the 3rd and 4th group perform weight training for 90–120 minutes throughout 6 weeks and the 1st group, the control group, are not given zinc supplementation and do not perform weight trainings.

Examination of the Testosterone. The blood samples are centrifuged at 3000 rpm³ for 10 mi- nutes and the blood plasma fractionation is done. The measurement of the plasma parameters is carried out at the Biochemistry laboratory of Özel I§il Kardiyoloji Dali Merkezi (Private I§il Cardiology Center) which operates in Diyarbakir. The analysis of Testosterone level is done through the Enzymatic Colometric method by using the scientific brand BT3000 biochemistry auto analyzer.

The Statistical Analyses. Variance analysis is used to identify the differences between the values of the groups obtained through measurements; and the Duncan’s Multiple Range Test is used to determine in which groups differentiations are observed. The comparison of the groups is done through t-test in order to identify the differentiations between the values of the groups obtained through measurements the statistical analyses are conducted via SPSS 22.0.

Results. When the bodyweight values given at (Table 1) is examined, it has not been found any differences between the pre-test and post-test values of the 1^st group (p > 0.05). It is identified statistically significant differences between the pre-test and post-test values of the 2nd, 3rd and 4th groups. It has been determined that zinc supplementation and weight training enables individuals to lose weight (p < 0.05). It is observed differences between the groups when the weight loss of the groups is compared with the control group and other groups (p < 0.05).

The total and free testosterone values of the groups are given at (Table 2). As the total testosterone values are considered, it is determined that values of both training and supplementation groups increase after the implementation (p < 0.05). When the pre-test and post-test values are examined, it has been identified statistically significant differences in zinc supplementation, exercise, and zinc supplementation + exercise groups (p < 0.05). Considering the free testosterone values, it has been observed differences between the pre-test and post-test values and also the values increase at the end of the implementation (p < 0.05).

Discussion. In this study which aims to examine the effects of 6-week zinc supplementation applied with weight trainings 4 times a week on the free and total testosterone levels in sedentary and athletes, the total testosterone and free testosterone values of the participants were measured from the blood samples which were drawn from the participants at the beginning and at the end of the 6-week training period. When

Спортивная тренировка these measurements are compared, it is identified that zinc supplementation applied with weight trainings create positive changes in both free and total testosterone levels. It is confirmed that these changes are seen in both groups supplied with zinc and training and zinc supplementation + training groups.

Table 1

The Age, Height, Weight and Fat Values of the Research Groups

Values	Measurement	1st Group (Cont)	2nd Group (Zn)	3rd Group (Tra + Zn)	4th Group Training
Age (year)	I. Measurement	20.04 ± 2.20x	21.02 ± 3.10x	20.89 ± 2.06x	20.44 ± 3.02x
Height (cm)	II. Measurement	174.52 ± 7.56x	175.40 ± 8.25x	175.08 ± 7.15x	176.02 ± 7.20x
Weight (kg)	I. Pre test	76.60 ± 5.42ax	75.22 ± 5.70ax	75.84 ± 5.92ax	74.63 ± 5.86ax
	II. Posttest	75.32 ± 6.90ay	77.71 ± 5.57bx	78.22 ± 6.12bx	77.42 ± 6.08bx

Note: a, b; the differences in measurements that carry different letters at the same column are important (p < 0.05); x, y, z; the differences between the groups that carry different letters at the same line are important (p < 0.05). I. Measurement: Pre-Supplementation (Pre Test). II. Measurement: Post-Supplementation (Post Test).

Table 2

Total and Free Testosterone Values of the Research Groups

Values	Measurements	1st Group (Cont)	2nd Group (Zn)	3rd Group (Tra + Zn)	4th Group Training
Total Testosterone (uIU/mL)	I.    Pretest II.    Post test	596,20 ± 52ax 605,40 ± 0.88ax	604,30 ± 0.87ax 638,60 ± 0.74by	612,60 ± 0.96ax 654,20 ± 0.92by	616,50 ± 0.90ax 658,30 ± 0.92by
Free Testosterone	I.    Pre test II.    Post test	14,8 ± 3.76ax 14,6 ± 3.70ax	15,7 ± 3.50ax 18,8 ± 4.18by	16,8 ± 4.48ax 22,5 ± 4.36by	16,6 ± 3.44ax 21,3 ± 3.88by

Note: a, b; the differences in measurements that carry different letters at the same column are important (p < 0.05); x, y, z; the differences between the groups that carry different letters at the same line are important (p < 0.05). I. Measurement: Pre-Supplementation (Pre Test). II. Measurement: Post-Supplementation (Post Test).

the effects of regular exercises on the blood glucose and testosterone in diabetic rats. They have determined that moderate exercises implemented for 9 weeks decrease the blood glucose and enhance the testosterone levels. In a study conducted on human subjects, [21] have studied the serum anabolic and catabolic effects of the acute exercises performed close to the anaerobic threshold in antrene and sedentary young males. In conclusion, the cortisol levels of both sedentary and athlete groups decrease below the basal level in 24 hours following the exercise. Additionally, anabolic hormones (testosterone, growth hormone and insulin-like growth factor-1) have increased significantly in both groups but particularly in the antrene group. In a similar study, it has been determined that short-term high-intensity tiring exercise enables total testosterone levels of the athletes to increase considerably [1]. Similarly, [13] has examined the serum adipo-nectin and testosterone concentration of 12-week endurance training in young obese males. 21 obese male participants are divided into two groups as control group and experimental group. At the end of the study, it has been confirmed that endurance training implemented 3 times a week for 12 weeks has increased the serum adiponectin and testosterone concentration. The [11] studied the effect of increased exercises and decreased caloric intake on the testosterone levels. They have ascertained that 12-week aerobic exercise and caloric intake restriction have increased significantly the serum testosterone levels.

Conclusions. As a consequence, 6-week zinc supplementation applied with weight trainings 4 times a week in sedentaries and athletes has increased the free and total testosterone levels significantly. Therefore, it may be said the increment of zinc supplementation in human organism increases the testosterone levels and constitutes positive effects on the physical performance.