Effects of 6-week hypertrophy training on body profile and muscle cross-section in chronotype-determined groups

The aim of this study is to examine whether 6 weeks of hypertrophy training has an effect on body profile and muscle cross-section in groups determined according to chronotypes. Twenty healthy male volunteers with a mean age of 19.42±1.017 years participated in the study. A chronotype questionnaire was applied to the participants, which could be divided into morning and evening groups. According to the results of the questionnaire, they were divided into two groups: morning group (n=10) and evening group (n=10). Morning and evening groups applied hypertrophy training for 6 weeks after 4 weeks of adaptation training. As a pre-post test in all groups; body circumference and diameter measurements were made to determine somatotype. Then, the cross-section of the upper leg muscle (fiber diameter, size, etc.) was examined with magnetic resonance imaging. Frequency and descriptive statistics were used to determine the distribution of the data, paired samples t-test was used to determine the pre- and post-exercise differences within the groups, and independent samples t-test was used to determine the difference between the groups. In conclusion, based on the pre-test and post-test results for the morning and evening groups, the difference between the groups was significant only in the post-test for body fat percentage, while the differences between the groups for the other parameters were not significant. However, while there was no statistically significant difference between the groups in the cross-sectional rectus femoris measurement, there was a medical and mathematical difference. In this context, it can be said that those with a morning biorhythm and those who train in the morning have an advantage over those with an evening biorhythm and those who train in the evening.