## 5 Conclusions  
In conclusion, cycling at 50%, 60%, and 70% VO\({}_{2}\)pk for 10, 20, and 30 min can potentially increase oxidative stress and antioxidant activities acutely, but with different responses. These findings confirm that oxidative stress markers responses seem to be dependent on the duration of moderate intensity of exercise and may help in the prescription of more effective and less harmful effects of exercise-induced oxidative stress among this population. For sedentary adults, a short duration of high-intensity exercise can be proposed for initial exercise levels. Hence, we suggest that the starting exercise intensity for sedentary adults should not be more than 70% VO\({}_{2}\)pk.  
These findings further emphasize the need to achieve optimal exercise intensity and duration and provide physical trainers, exercise enthusiasts, and clinical practitioners with practical settings. Here, an optimal exercise intensity and duration bring beneficial health outcomes. Concurrently, works should evaluate the long-term effect of this study's optimal intensity and duration. An investigation should be conducted to determine the chronic state of oxidative stress and antioxidant enzyme responses concerning exercise intensity and duration. The existing literature is yet to demonstrate the physiological mechanism that underpins the oxidative process during exercise, especially when the intensity or duration is increased. Here remain the opportunities for future research to evaluate the differences in the production pathways of ROS and free radicals based on different exercise intensities and durations.  
Conceptualization, D.M.A.D.; methodology, D.M.A.D. and F.A.; formal analysis, D.M.A.D.; writing--original draft preparation, D.M.A.D. and D.M.P.B.; writing--review and editing, Z.A.Z.; funding acquisition, D.M.A.D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by University Malaysia Sabah, Malaysia (grant number SDK0330). University Malaysia Sabah, Malaysia, funded the APC.  
This study was conducted according to the guidelines of the Declaration of Helsinki and following the specifications approved by the Ethical Committee of University Kebangsaan Malaysia, Kuala Lumpur (Ref. no.: UKM 1.5.3.5/244/PPP2).  
All subjects had agreed to participate in this study by providing written informed consent.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to confidentiality issue.  
The authors thanked University Malaysia Sabah, Malaysia, for providing facilities and access to various online databases.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.  
I, intensity; D, duration; VO\({}_{2}\)pk, peak oxygen consumption; VO\({}_{2}\), oxygen consumption; HR, heart rate; ROS, reactive oxygen species; BMI, body mass index; SOD, superoxide dismutase; GPx, glutathione peroxidase; CAT, catalase; MDA, malondialdehydedehyde; AE, the ratio of antioxidant enzymes activity.