## 3 Results
The time course of the changes in the largest Lyapunov exponent and approximate entropy are presented in Figures 3 and 4. All nonlinear parameters were increased in the caffeine group, and these increments were statistically significant for the largest Lyapunov exponent and approximate entropy at 60 min (Table 2). Also, the caffeine group's largest Lyapunov exponent values at 60 min were found to be statistically significant when compared to those for the control group (\(p\) = 0.013). For the taurine group, there was a slight reduction in the correlation dimension, but no significant alterations were observed for the other nonlinear parameters. Furthermore, for the caffeine + taurine group, all nonlinear parameters were higher than the pre values; however, a statistically significant increase was only observed for the largest Lyapunov exponent value at 60 min. No significant changes in the nonlinear parameters were observed for the control group over time. Figure 1: Time course of changes in heart rate of experimental groups. \(\Delta\): statistically significant versus the pre value of the caffeine group (\(p\) = 0.013). Figure 2: Time course of changes in systolic blood pressure in experimental groups. \(\Delta\): statistically significant versus the pre value of the caffeine group (\(p\) = 0.019). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & **Caffeine** & **Taurine** & **Caffeine + Taurine** & **Control** \\ \hline  & Pre & 3 \(\pm\) 0.688 & 3 \(\pm\) 0.641 & 3 \(\pm\) 0.194 & 3 \(\pm\) 0.326 \\ Embedding & 30 min & 3 \(\pm\) 0.109 & 3 \(\pm\) 0.113 & 3 \(\pm\) 0.677 & 3 \(\pm\) 0.773 \\ Dimension & 60 min & 3 \(\pm\) 0.341 & 3 \(\pm\) 0.651 & 3 \(\pm\) 0.382 & 3 \(\pm\) 0.161 \\  & _p_-value & 0.445 & 0.943 & 0.111 & 0.444 \\ \hline  & Pre & 2 \(\pm\) 0.120 & 2 \(\pm\) 0.663 & 2 \(\pm\) 0.798 & 4 \(\pm\) 0.391 \\ Time Delay & 30 min & 3 \(\pm\) 0.251 & 3 \(\pm\) 0.214 & 3 \(\pm\) 0.379 & 3 \(\pm\) 0.832 \\  & 60 min & 3 \(\pm\) 0.188 & 3 \(\pm\) 0.216 & 3 \(\pm\) 0.256 & 2 \(\pm\) 0.166 \\  & _p_-value & 0.337 & 0.910 & 0.963 & 0.558 \\ \hline  & Pre & \(-\)0.357 \(\pm\) 1.193 & \(-\)0.341 \(\pm\) 1.184 & \(-\)0.343 \(\pm\) 1.246 & \(-\)0.343 \(\pm\) 0.167 \\ Lyapunov & 30 min & 0.069 \(\pm\) 1.166 & \(-\)0.345 \(\pm\) 1.108 & 0.280 \(\pm\) 1.013 & \(-\)0.347 \(\pm\) 0.995 \\ Exponent & 60 min & 1.507 \(\pm\) 1.391 & \(-\)0.347 \(\pm\) 1.825 & 0.829 \(\pm\) 1.121 & \(-\)0.346 \(\pm\) 0.571 \\  & _p_-value & 0.009 & 0.101 & 0.021 & 0.609 \\ \hline  & Pre & 0.987 \(\pm\) 0.016 & 1.001 \(\pm\) 0.017 & 0.995 \(\pm\) 0.013 & 0.986 \(\pm\) 0.021 \\ Correlation & 30 min & 1.029 \(\pm\) 0.053 & 0.990 \(\pm\) 0.064 & 1.023 \(\pm\) 0.091 & 0.984 \(\pm\) 0.013 \\ Dimension & 60 min & 1.140 \(\pm\) 0.078 & 0.864 \(\pm\) 0.048 & 1.086 \(\pm\) 0.087 & 0.984 \(\pm\) 0.029 \\  & _p_-value & 0.261 & 0.811 & 0.113 & 0.716 \\ \hline  & Pre & 0.089 \(\pm\) 0.052 & 0.090 \(\pm\) 0.026 & 0.091 \(\pm\) 0.067 & 0.090 \(\pm\) 0.096 \\ Approximate Entropy & 30 min & 0.119 \(\pm\) 0.043 & 0.093 \(\pm\) 0.080 & 0.108 \(\pm\) 0.084 & 0.090 \(\pm\) 0.023 \\  & 60 min & 0.136 \(\pm\) 0.086 & 0.093 \(\pm\) 0.007 & 0.127 \(\pm\) 0.030 & 0.092 \(\pm\) 0.089 \\  & _p_-value & 0.035 & 0.959 & 0.143 & 0.517 \\ \hline  & Pre & 0.793 \(\pm\) 0.012 & 0.787 \(\pm\) 0.181 & 0.787 \(\pm\) 0.109 & 0.793 \(\pm\) 0.145 \\ Hurst & 30 min & 0.823 \(\pm\) 0.073 & 0.785 \(\pm\) 0.129 & 0.825 \(\pm\) 0.141 & 0.791 \(\pm\) 0.166 \\ Exponent & 60 min & 0.858 \(\pm\) 0.091 & 0.785 \(\pm\) 0.117 & 0.849 \(\pm\) 0.132 & 0.789 \(\pm\) 0.219 \\  & _p_-value & 0.079 & 0.704 & 0.228 & 0.900 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Nonlinear heart rate variability parameters of the groups. _p_-value refers to the differences between the pre and 60 th min values of the groups. Figure 3: Time course of changes in the largest Lyapunov exponent of experimental groups.