Sports and Free Radicals

How are Sports and Free Radicals Related?

1. Free Radicals:

Free radicals are molecular species that have the ability to exist independently and contain an unpaired electron in an atomic orbital. These radicals are unstable and highly reactive. They can either accept or donate an electron to other molecules, therefore the free radicals behave as reductants or oxidants.

These free radicals stay short in a biological setting dependent upon the site and rate of production, free radicals can mediate both harmful modifications to bio-molecules and/or take part in homeostatic, cellular signal transduction.

The most important oxygen-containing free radicals that cause cell damage, diseases, and aging, are superoxide anion radical, hydrogen peroxide, hydroxyl radical, oxygen singlet, hypochlorite, nitric oxide, and peroxynitrite radicals.

These highly reactive species can damage nuclear DNA, proteins, carbohydrates, and lipids in the cell and cell membrane. Free radicals attack important cellular macromolecules leading to cell damage and homeostatic disruption.

These free radicals target all kinds of molecules in the body especially lipids, nucleic acids, and proteins.



a. Sports and exercise have clinical benefits but the beneficial effects of sport and exercise are lost with exhaustion and with lack of training. Exhaustive exercise causes muscle damage because of an increase in the plasma activity of cytosolic enzymes such as lactate dehydrogenase or creatine kinase as well as some of this damage is due to the production of excess free radicals.

b. Rush of free radical/reactive oxygen species in red blood cells can break down the cell membrane (hemolysis) and denature the hemoglobin of red blood cells which can lead to hemolytic anemia.


2. How are sports and free radicals related?

Normally, reactive oxygen species are continuously produced in the human body and some of these have beneficial effects and there is a balance between free radicals (pro-oxidant) and antioxidants (antioxidant defense system) in the body. But when there is oxidative stress (excess of free radicals) due to increased oxygen consumption and cellular activity during intense sports performance, exercise or physical activity can lead to damaging and harmful results in the body.


3. How excess free radicals are produced during sports performance?

Intense and long duration sports performance and physical activity increase the free radicals that create an imbalance between pro-oxidant and antioxidant defence system through several possible factors, including an increase of phenomena of reperfusion of muscle tissue, increase in oxygen consumption, increase in production of ATP, autoxidation of catecholamines (epinephrine), the release of metals (free iron), increased temperature in the muscle and its inflammation, oxidation of the purine basis from DNA, and the activation of neutrophils (WBCs) by using at least three biochemical pathways such as mitochondrial electron transport chain, xanthine oxidase, and polymorphoneutrophil. The reception of free radicals from the external environment also increases the intensity of imbalance between pro-oxidant and antioxidant defense system.

Free radicals consume antioxidants, antioxidant enzymes are released into the blood plasma, intracellular calcium rises up, the production of nitric oxide (NO) increases, and the levels of hydrogen peroxide (H2O2) and hypochlorous acid (HOCl) increase. These penetrate through the cell membranes and ultimately peroxidation of lipids, proteins, DNA, and other compounds occur and lead to cellular damage and aging, serious illnesses including cancer.


4. One liner reason or etiology:

Disturbance or imbalance between the production of free radicals and the availability of antioxidants (Glutathione, NADPH, and Vitamins).

What are antioxidants?

Antioxidants are the molecules or substances that can prevent or slow down the damage to cells caused by free radicals. Antioxidants convert unstable free radical molecules into stable molecules.

a. Endogenous antioxidants:

Most enzymes are the endogenous antioxidants that work in conjunction with specific minerals such as  iron, copper, zinc, manganese, and selenium.

b. Exogenous antioxidants:

Exogenous antioxidants are the vitamins such as vitamin A (beta-carotene), E, C, flavonoids, alpha-lipoic acid,  resveratrol, lycopene, and ubiquinone. 

Free radicals are unstable and highly reactive that can react and oxidize, damage, or denature the cellular contents such as lipids (cell membrane), proteins, and DNA. Sports and intense activities can increase the production of free radicals and imbalance the cellular pro-oxidant and antioxidant defence system. We can decrease the risks of pro-oxidant and antioxidant imbalance, cellular damage, diseases, aging, and ultimately improve health by consuming antioxidant-rich foods and supplements.

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