## 3 Results
### Oxidative Stress and Antioxidant Enzymes Responses  
We observed that MDA concentration increased significantly immediately after exercise at all intensity levels and durations (Table 3). SOD activity also rose immediately after completing all exercise bouts, except it decreased significantly at 70% VO2 pk for 30 min. CAT activities also increased substantially after exercise at 50% VO2 pk for 10 and 20 min but decreased after exercise at 60% VO2 pk for 30 min duration (Table 3). As exercise intensity intensified to 70% VO2 pk, the CAT activities significantly reduced after exercise at all durations. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Duration (Mins)** & **Intensity (\%)** & **Measured \(\dot{\text{VO}}\)2 (Mean \(\pm\) SE)** & **Exercise HR (Mean \(\pm\) SE)** \\ \hline
10 & & 20.30 \(\pm\) 1.088 & 127.56 \(\pm\) 3.586 \\
20 & 50\% \(\dot{\text{VO}}\)2 pk & 20.31 \(\pm\) 0.983 & 126.36 \(\pm\) 3.298 \\
30 & & 20.37 \(\pm\) 1.030 & 126.28 \(\pm\) 3.246 \\ \hline
10 & & 24.15 \(\pm\) 1.001 & 148.68 \(\pm\) 3.718 \\
20 & 60\% \(\dot{\text{VO}}\)2 pk & 24.05 \(\pm\) 0.926 & 148.08 \(\pm\) 3.577 \\
30 & & 24.35 \(\pm\) 1.004 & 149.56 \(\pm\) 3.663 \\ \hline
10 & & 27.58 \(\pm\) 1.125 & 166.64 \(\pm\) 4.206 \\
20 & 70\% \(\dot{\text{VO}}\)2 pk & 27.88 \(\pm\) 1.147 & 167.64 \(\pm\) 4.233 \\
30 & & 27.90 \(\pm\) 1.056 & 169.32 \(\pm\) 3.945 \\ \hline \end{tabular}
\end{table} 
Table 2: Oxygen usage and heart rate (HR) responses at different intensity percentages and duration of exercise. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**SOD**} & \multicolumn{2}{c}{**CAT**} & \multicolumn{2}{c}{**GPx**} & \multicolumn{2}{c}{**AE**} & \multicolumn{2}{c}{**MDA**} \\
**\% \(\dot{\text{VO}}\)2 pk** & **D** & \multicolumn{2}{c}{**(Unit/mgHb)**} & \multicolumn{2}{c}{**(u/s/mgHb)**} & \multicolumn{2}{c}{**(Unit/min/mgHb)**} & \multicolumn{2}{c}{**(Unit/min/mgHb)**} & \multicolumn{2}{c}{**(nmol/mL)**} \\ \cline{3-7}  & & \multicolumn{4}{c}{**(Mean \(\pm\) SEM)**} \\ \hline
50\% & 10 & Pre & 0.83 \(\pm\) 0.049 & 0.29 \(\pm\) 0.019 & 6.009 \(\pm\) 0.0002 & 3.172 \(\pm\) 0.3333 & 9.23 \(\pm\) 0.357 \\  & & Post & 1.41 \(\pm\) 0.082 * & 0.36 \(\pm\) 0.018 * & 5.621 \(\pm\) 0.001 & 4.009 \(\pm\) 0.2914 & 10.28 \(\pm\) 0.300 * \\ \cline{3-7}  & & \% changes & 93.3 \(\pm\) 22.02 & 44.6 \(\pm\) 14.62 & \(-\)4.5 \(\pm\) 3.00 & 61.52 \(\pm\) 21.804 & 12.7 \(\pm\) 1.81 \\ \hline
60\% & 10 & Pre & 0.91 \(\pm\) 0.096 & 0.40 \(\pm\) 0.022 & 5.507 \(\pm\) 0.001 & 2.447 \(\pm\) 0.2873 & 8.41 \(\pm\) 0.381 \\  & & Post & 1.28 \(\pm\) 0.044 * & 0.41 \(\pm\) 0.021 & 5.112 \(\pm\) 0.001 & 3.248 \(\pm\) 0.1839 * & 9.97 \(\pm\) 0.322 * \\ \cline{3-7}  & & \% changes & 139.3 \(\pm\) 47.45 & 4.9 \(\pm\) 4.77 & \(-\)4.3 \(\pm\) 4.95 & 147.51 \(\pm\) 51.332 & 21.5 \(\pm\) 3.79 \\ \hline
70\% & 10 & Pre & 1.14 \(\pm\) 0.048 & 0.34 \(\pm\) 0.012 & 7.281 \(\pm\) 0.0004 & 3.413 \(\pm\) 0.1889 & 10.01 \(\pm\) 0.360 \\  & & Post & 1.68 \(\pm\) 0.069 * & 0.31 \(\pm\) 0.018 * & 6.491 \(\pm\) 0.0004 & 5.679 \(\pm\) 0.4152 * & 12.98 \(\pm\) 0.356 * \\ \cline{3-7}  & & \% changes & 52.6 \(\pm\) 8.72 & \(-\)8.6 \(\pm\) 3.49 & \(-\)2.9 \(\pm\) 8.27 & 72.07 \(\pm\) 11.272 & 32.1 \(\pm\) 3.91 \\ \hline \end{tabular}
\end{table} 
Table 3: Changes in antioxidant enzymes activities and MDA concentration after exercise intervention at different intensities and duration. Similarly, GPx activity decreased significantly after 20 and 30 min at all intensity levels (Table 3). The ratio of activities of antioxidant enzymes was calculated using \(AE=\frac{SOD}{\text{U}Px+CAT}\)[41]. In contrast, the antioxidant enzyme activity ratio only increased after exercise at 60% and 70% \(\text{VO}_{2}\text{pk}\) for all durations, except it decreased at 70% \(\text{VO}_{2}\text{pk}\) for 30 min (Table 3). The percentage increment of MDA continued to increase (Figure 1), and even the percentage increment of MDA increased exponentially after exercise at 70% \(\text{VO}_{2}\text{pk}\) for 30 min.