Antioxidant or Free Radical Production Depends on the Intensity of the Exercise Performed

Limit Exercise Intensity & Duration to Enjoy Benefits of Antioxidant Production

Movies are not spicy without a villain and life too seems to be bland when it goes on and on without some challenges to dethrone. So is the connection between free radicals and antioxidants. Our body is our recluse from which we garner energy for day-to-day functioning of all activities. This energy is acquired from the food that we eat. Free radicals are produced as a consequence of metabolic steps when food is converted into energy, as a result of normal cellular function and also as part of natural physiological process of all living beings. They might also be derived from external sources such as exposure to X-rays, ozone, cigarette smoking and industrial chemicals. There is a continuous formation of free radicals happening in our body as a result of enzymatic and nonenzymatic reactions. Until their production is normal there is no harm caused from them but once overproduction happens, they can become dangerous to even basic processes needed to keep individuals alive. In order to avoid such damages, the cells also produce free radical scavengers known as antioxidants.

Free Radicals & Antioxidants
Free radicals are molecules that contain one or many unpaired electrons in their outer orbit which become highly unstable when they try to react with other molecules to attain molecular stability. In this outreach, the free radical robs other molecules of their electrons creating a chain reaction leading to the damage of DNA and protein breakdown. But it is essential to known that not all free radicals are harmful and there are some of them which help to wipe out invading pathogenic microbes to protect the body’s defense mechanism. In science, we use the terms reactive oxygen species (ROS) and reactive nitrogen species (RNS) to describe free radicals and other non-radical reactive derivatives.

The human body has its own tactical ways for self-defence. It has an excellent antioxidant network that plays the defense role helping to neutralize free radicals and maintain homeostasis. But the defense mechanism doesn’t work in favour of the individual all the time where an imbalance between free radical production and antioxidant defense is possible. Such imbalance leads to what we call ‘oxidative stress’. This oxidative stress is considered to be the starting point for the origin of numerous diseases, development of ageing and the onset of health problems such as arthritis, cardiovascular and neurodegenerative diseases, inflammation and cancer. Oxidative stress is also possible due to poor diet or disease. Nowadays, we read numerous articles that suggest the consumption of various foods for antioxidant benefits but there are also questions raised whether performance of exercise can alleviate the effects of free radicals.

Exercise & its Effect on Free Radicals
Physical activity has been proposed as a solution to remove the harmful effects caused by free radicals on the human body. Various studies these days show evidence that ROS are generated during exercise but physical activity helps in improving antioxidant defense. Physical activity is different from exercise. We define physical activity as some body movement produced by skeletal muscles resulting in energy consumption and examples include everyday life activities and exercises such as walking and cycling. Moderate exercise and an active lifestyle have been proposed as good ways to reduce oxidative stress. It finally depends on the exercise duration, intensity, fitness condition and nutritional status as to whether the reactive species are helpful or harmful. On the other hand, we also have research showing that exercise-induced free radical production promotes insulin sensitivity in humans thereby acting as a catalyst for type 2 diabetes prevention.

Regular practise of moderate-intensity exercise helps to stay away from oxidative stress while acute bodily exercises can cause oxidative stress and increase the production of free radicals. Overperformance of exercise increases the amount of reactive and nitrogen species which increase ROS production and RNS might cause imbalance among RONS and antioxidants. Hence, exercise-an activity that must benefit the body-becomes the cause for exhaustion and injury.

Effect of Low-intensity Exercise on Antioxidants & Oxidative Stress
The study included 2 groups: one group of low-intensity exercise performers (EXG) and another one performing no exercises called the control group (CG) with each group consisting of 20 participants. Low-intensity exercise is that which gets you to about 40-50% of your maximum heart rate (MHR) such as jogging and walking. Those individuals above the age of 30, suffering from chronic diseases or taking long-term medications were excluded from the study. Blood samples of all the participants were collected and antioxidant capacity of the samples was estimated using the Benzie and strain method.

A comparison between the two groups was made regarding body mass index (BMI), alanine transferase (ALT), alkaline phosphate (ALP), aspartate (AST) and FRAP. Significant difference in BMI values was found in both groups with BMI of CG less than the BMI of EXG. ALT of CG was less than that of EXG; ALP of CG was high than the ALP of EXG; AST of CG was less than the AST of EXG. The study concluded that low-intensity exercise had no effect on liver enzymes but improved blood life quality by reducing various health problems related to oxidative damage of cells and muscles fatigue.
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Physical Activity Improves Antioxidant Capacity in Individuals with Type 2 Diabetes Mellitus
We have numerous evidences pointing to the fact that free radicals and oxidative stress contribute towards Type 2 diabetes mellitus (T2DM) and its related complications. Some of the causes of oxidative stress during diabetes include overproduction of ROS by mitochondria and nonenzymatic glycation. Physical activity or exercise helps to improve insulin resistance by improving insulin action and vascular function while decreasing ROS generation. Animal studies were conducted to bring about the effect of exercise on T2DM. Regular and moderate-intensity aerobic exercise that consisted of 12 weeks of swimming was conducted for both diabetic and lean rats which were between 8 and 20 weeks of age. The animals performed the exercise in a cylindrical tank that contained water in a controlled temperature. The animals were placed in the tank everyday at the same time. While the duration was for 15 min/d initially it was increased to 60 min/d by the end of the first week and the schedule was followed thrice every week. The sedentary rats were placed in similar containers where the swimming session was held for all the 60 min to ensure that rats in both groups underwent the same amount of stress. The research team observed an amelioration of insulin resistance and diabetic dysmetabolism. A decrease in systolic and mean blood pressure and heart rate, decrease in oxidative stress and increase in NO production was observed.
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Antioxidants came to the defense of animals with T2DM in yet another study by Nishida et al. which reported increased Cu/Zn-SOD protein production as a result of low-intensity exercise in contrast with increased Mn-SOD after moderate-intensity exercise. Studies from other researchers on a six-month moderate-intensity aerobic exercise training showed decrease in lipid peroxidation, increase in GSH and catalase activity in T2DM and obese individuals. Oliveira et al. compared the effects of 12 weeks of training on 3 different exercises (aerobic, strength and combined training) on T2DM male and female human participants showing that aerobic training program provided important upregulation in antioxidant enzymes and increased NO bioavailability which helps to minimize oxidative stress and chronic complications of diabetes.

Hence, regular and moderate exercise can have antioxidant and anti-inflammatory effect in individuals with type 2 diabetes.

Both aerobic and anaerobic exercise can produce free radicals but oxidative stress always doesn’t occur because ROS production is dependent on the exercise intensity. While high ROS production due to acute exercise performance is harmful to the immune system chronic exercise produces physiological adaptations that can empower a person’s antioxidant system.

References
Regular Physical Exercise as a Strategy to Improve Antioxidant & Anti-inflammatory Status: Benefits in Type 2 Diabetes Mellitus: https://www.hindawi.com/journals/omcl/2012/741545/

Oxidants, Antioxidants & the Beneficial Roles of Exercise-induced Production o Reactive Species: https://www.hindawi.com/journals/omcl/2012/756132/
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Is Exercise the Best Antioxidant Supplement? https://www.unm.edu/~lkravitz/Article%20folder/Antioxidants.pdf
Impact of Low-intensity Exercise on Liver Enzymes and Antioxidants Systems of the Body: https://www.unm.edu/~lkravitz/Article%20folder/Antioxidants.pdf