## 3 Results
### Oxidative Stress and Antioxidant Enzymes Responses
However, the percentage increment of CAT decreased in response to the increment of both intensity and duration of exercise (Figure 2). The percentage changes of CAT activities were positive across all exercise intensity and duration except at 70% \(\text{VO}_{2}\text{pk}\) for all durations and at 60% \(\text{VO}_{2}\text{pk}\) for 30 min. As for GPx, the percentage changes in GPx are low and did not vary after exercise at different intensities and duration (Figure 3). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\ \begin{tabular}{c} **I** \\ **\% \(\text{VO}_{2}\text{pk}\)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **D** \\ **mins** \\ \end{tabular}  } & \multicolumn{2}{c}{SOD} & \multicolumn{2}{c}{CAT} & \multicolumn{2}{c}{GPx} & \multicolumn{1}{c}{AE} & \multicolumn{1}{c}{**MDA**} \\  & & & **(Unit/mgHb)** & **(u/s/mgHb)** & **(Unit/min/mgHb)** & **(Unit/min/mgHb)** & **(nmol/ml)** \\ \cline{3-8}  & \multicolumn{6}{c}{**(Mean \(\pm\) SEM)**} \\ \hline
50\% & 20 & Pre & \(1.18\pm 0.052\) & \(0.45\pm 0.027\) & \(6.941\pm 0.0002\) & \(2.842\pm 0.2218\) & \(9.10\pm 0.265\) \\  & & Post & \(1.54\pm 0.092\) * & \(0.49\pm 0.029\) * & \(6.058\pm 0.0001\) * & \(3.324\pm 0.3163\) & \(10.31\pm 0.289\) * \\ \cline{3-8}  & & \% changes & \(34.7\pm 8.74\) & \(12.8\pm 3.79\) & \(-10.4\pm 3.75\) & \(21.59\pm 7.984\) & \(14.7\pm 3.54\) \\ \hline
60\% & 20 & Pre & \(1.19\pm 0.082\) & \(0.41\pm 0.019\) & \(6.755\pm 0.0001\) & \(2.994\pm 0.2171\) & \(8.58\pm 0.383\) \\  & & Post & \(1.54\pm 0.051\) * & \(0.42\pm 0.027\) & \(6.303\pm 0.0001\) * & \(4.189\pm 0.4255\) * & \(10.57\pm 0.255\) * \\ \cline{3-8}  & & \% changes & \(44.8\pm 12.16\) & \(3.8\pm 6.17\) & \(-5.7\pm 2.69\) & \(49.34\pm 12.552\) & \(30.4\pm 7.45\) \\ \hline
70\% & 20 & Pre & \(1.15\pm 0.060\) & \(0.54\pm 0.031\) & \(6.573\pm 0.0002\) & \(2.308\pm 0.1951\) & \(9.37\pm 0.341\) \\  & & Post & \(1.51\pm 0.073\) * & \(0.49\pm 0.037\) * & \(6.079\pm 0.0003\) * & \(3.496\pm 0.3218\) * & \(13.20\pm 0.249\) * \\ \cline{3-8}  & & \% changes & \(40.5\pm 10.79\) & \(-9.7\pm 3.77\) & \(-7.1\pm 3.32\) & \(59.59\pm 13.852\) & \(44.6\pm 4.88\) \\ \hline
50\% & 30 & Pre & \(1.01\pm 0.067\) & \(0.40\pm 0.023\) & \(7.363\pm 0.0001\) & \(2.617\pm 0.1938\) & \(8.49\pm 0.277\) \\  & & Post & \(1.21\pm 0.066\) * & \(0.41\pm 0.026\) & \(6.995\pm 0.0001\) * & \(3.070\pm 0.2187\) & \(10.16\pm 0.261\) * \\ \cline{3-8}  & & \% changes & \(30.8\pm 10.38\) & \(4.9\pm 5.38\) & \(-4.1\pm 2.26\) & \(28.35\pm 10.470\) & \(21.3\pm 3.26\) \\ \hline
60\% & 30 & Pre & \(1.73\pm 0.112\) & \(0.37\pm 0.024\) & \(5.948\pm 0.0001\) & \(5.319\pm 0.5969\) & \(9.06\pm 0.324\) \\  & & Post & \(1.99\pm 0.134\) * & \(0.34\pm 0.021\) * & \(5.336\pm 0.0001\) * & \(6.373\pm 0.5307\) * & \(11.88\pm 0.365\) * \\ \cline{3-8}  & & \% changes & \(20.2\pm 8.07\) & \(-6.5\pm 2.93\) & \(-10.3\pm 1.88\) & \(32.55\pm 10.239\) & \(32.3\pm 2.99\) \\ \hline
70\% & 30 & Pre & \(1.17\pm 0.053\) & \(0.33\pm 0.019\) & \(8.031\pm 0.0002\) & \(3.835\pm 0.3066\) & \(8.36\pm 0.369\) \\  & & Post & \(0.87\pm 0.039\) * & \(0.29\pm 0.017\) * & \(7.610\pm 0.0001\) * & \(3.076\pm 0.1973\) * & \(13.85\pm 0.302\) * \\ \cline{3-8}  & & \% changes & \(-22.7\pm 4.10\) & \(-7.8\pm 3.81\) & \(-4.8\pm 1.31\) & \(-11.53\pm 7.246\) & \(72.5\pm 7.41\) \\ \cline{3-8}  & & \% changes & \(-22.7\pm 4.10\) & \(-7.8\pm 3.81\) & \(-4.8\pm 1.31\) & \(-11.53\pm 7. Figure 1: Percentage of MDA changes at 50%, 60%, and 70% VO2 pk during exercise. * significantly different from 70% V O2 pk (_p_ < 0.05). Figure 3: Percentage of GPx changes at 50%, 60%, and 70% VO2 pk during exercise. Figure 2: Percentage of CAT changes at 50%, 60%, and 70% VO2 pk during exercise. * significantly different from 70% V O2 pk (_p_ < 0.05). As opposed to CAT, the percentage changes of AE and SOD exhibited a similar pattern, with positive percentage changes after all exercise bouts except negative percentage change after exercising at 70% \(\dot{\mathrm{V}}\)O\({}_{2}\)pk for 30 min (Figures 4 and 5).