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Asian J Kinesiol > Volume 15(3); 2013 > Article
The Official Journal of the Korean Academy of Kinesiology 2013;15(3):71-78.
DOI: https://doi.org/10.15758/jkak.2013.15.3.71     Published online July 31, 2013.
Effects of Taking ZMA on Plasma Testosterone, IGF-1, Cortisol, and Body Composition during the 12 Weeks of High Intensity Resistance Exercise
Kwang-Su Choi, Sang-Chul Han, Sang-Ho Lee, Ki-Hong Kim
Incheon University
Kyungwoon University
Dankook University
Correspondence:  Sang-Chul Han,
Email: hansc@incheon.ac.kr
Received: 13 June 2013   • Accepted: 20 July 2013

This study attempted to examine the changes in testosterone, IGF-1, cortisol in blood, body composition according to the intake of ZMA during the 12 weeks of resistance exercise for healthy male college students. Participants were divided into a ZMA group and a Control group and a post-test for identical variables was conducted after 12 weeks.
In this study, paired sample t-test was conducted in the groups to measure the changes before and after experiments and 0.5 was selected as a significant level. In addition, independent-sample t-test was conducted between two groups.
The results of this study are as follows: significant differences (p<.05) were observed between two groups. In hormone changes, the average concentrations of testosterone (ng/ml) were 7.41±0.90 for the experimental group and 4.04±1.06 for the control group, and the average concentrations of IGF-1 were 295.69±72.08 for the experimental group and 221.53±45.74 for the control group. On the other hand, there was no significant difference in the average concentrations of cortisol (ug/dl) between two groups; 8.54±2.76 for the experimental group and 9.44±2.74 for the control group. Significant differences (p<. 05) were observed in the changes in the volumes of skeletal muscle; 38.41±1.81 for the experimental group and 35.14±3.46 for the control group. There was no significant difference in the averages of body fat percentage (%).There were significant differences (p<.05) in the changes in the muscle mass.
In conclusion, taking ZMA made significant differences in the concentrations of testosterone and IGF-1 in hormone changes were observed during workouts in comparison with no ZMA group. There were significant differences in the volume of skeletal muscle in body composition changes between two groups. It is considered that taking ZMA on a regular basis, have influences on hormone, body composition and arm circumferences.
Keywords: ZMA, testosterone, IGF-1, cortisol, muscle mass
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