Free Radicals and Muscle Soreness - Can Antioxidants Help?

by Yuri Elkaim, BPHE, CK, RHN
Author, Eating for Energy

 

Oxygen is pretty amazing. Its special reactivity provides us with the energy required to sustain life, including the ability to power movements and muscular contraction. However, the oxygen molecule is a double-edged sword, because this same chemical reactivity can also wreak havoc in the cells by means of the potentially destructive molecules called free radicals, which are produced unavoidably as a consequence of harnessing the chemical energy of oxygen within the body.

Free radical damage has been implicated as a factor in degeneration, heart disease, cancer, rheumatoid arthritis, and even the process of aging.

For the purposes of this article, we will look at how free radicals effect exercise-induced muscle soreness and, if or how anti-oxidants can play a preventive role.

Fortunately, the human body comes equipped with a number of systems capable of deactivating the free radicals produced as a result of oxygen metabolism. Collectively known as the ‘antioxidant defence system’, these systems use both antioxidant enzymes (large protein molecules manufactured in the body) and antioxidant nutrients (consumed in the diet) to ‘soak up’ the energy of free radicals, thereby minimising damage to the body.

In recent years, there has been much speculation that avid exercisers might be at increased risk of free radical damage, or ‘oxidative stress’. Regular exercisers don’t just process a larger volume of oxygen than their sedentary counterparts – they also process it at a higher rate; during training, the rate of oxygen processing by the mitochondria (the energy producing furnaces in the cells) can rise by a factor of 20, placing exceptionally high demands on the antioxidant defence system. By carrying out these higher levels of oxidation, to meet the extra energy requirements of exercise, your body produces a higher level of free radicals.

 

How is antioxidant nutrition linked to exercise-induced muscle damage?

Take a muscle biopsy immediately after a strenuous training session and you’ll certainly detect muscle damage. However, take a muscle biopsy from the same area 2-3 days later and you’ll detect even more damage! Although the initial damage that occurs is believed to be caused by mechanical strain, the delayed and additional damage is now known to occur as a result of an inflammatory response, aggravated by free radicals.

When a muscle cell is damaged (mainly via free radical associated cell membrane disruption known as lipid peroxidation), it becomes more ‘leaky’ to calcium, which then accumulates within the cell. This acts as a signal, attracting a range of immune cells, such as macrophages and monocytes, to the damaged area. These immune cells release toxins, including free radicals, to further break down the damaged areas and mop up tissue debris. In other words, the destructive power of free radicals is harnessed positively to help break down damaged tissue.

While the free radicals released by these cells help to break down the damaged tissue, if unchecked they can also attack adjacent healthy tissue. It’s a bit like using a sledgehammer to crack a nut: yes, it will get the job done, but it may take out your coffee table in the process! An optimally functioning antioxidant defence system, however, appears to minimise this collateral damage.

Studies also suggest that an improved antioxidant status, for instance by eating a raw food diet, enhances the adaptive response to exercise-induced muscle damage by increasing the concentration of the immune cells charged with initiating breakdown and repair.

The evidence suggests that how accustomed an individual is to a particular mode of exercise is an important factor in determining whether extra antioxidants can reduce post-exercise muscle damage and soreness.

 

New evidence suggests that age and gender are also relevant.

As far as older athletes are concerned, there is evidence that exercise-induced muscle damage is more extensive than in younger ones for any given intensity/duration of exercise, but also that older athletes may have most to gain from antioxidant supplementation. One study compared the structural muscle damage produced by 45 minutes of high-intensity eccentric exercise in young (20-30) and old (59- 63) men and found that the same intensity and duration of exercise produced significantly more muscle damage in older men.

A diet high in antioxidants intake doesn’t appear to prevent the mechanical damage induced by exercise, but in some circumstances it may be able to reduce the amount of postexercise damage that occurs as part of the repair and regeneration process. Such is the case for younger males but mainly when the exercise is ‘unaccustomed’, vigorous in nature and including a significant amount of eccentric work.

Female athletes, on the other hand, may have more to gain from antioxidant supplementation, even during their regular workout routines. For older athletes, who are more at risk than young ones from exercise-induced muscle damage, the case for antioxidant supplementation appears rather more clear-cut, and fortifying the diet with these nutrients seems a reasonable thing to do.

 

Can antioxidants prevent and/or reduce muscle soreness?

Overall, the research suggests that diets high in antioxidants do not significantly prevent or reduce exercise-induced muscle soreness. However, they certainly do not hurt. After all, they have tremendous benefits for slowing the aging process and reducing the risk of cancer, among other health benefits. For your overall health, it makes sense to ensure that your diet is high in antioxidants. The main nutrient-derived antioxidants are vitamins C, A (beta-carotene), E, selenium, and zinc, all of which are most abundantly found in fresh fruit, green leafy vegetables, nuts and seeds, olive oil, whole grains, and fish.

 

Poly vs. Mono

As mentioned earlier, free radicals cause damage to the cell through lipid peroxidation, as they disrupt the cell membrane. They are far more likely to react with phospholipids (part of cell membrane) based on polyunsaturated (corn/sunflower/flaxseed oils) fatty acids than monounsaturated fats. Therefore, a diet rich in monounsaturates (olive and avocado) would lead to membranes which are more resistant and less susceptible to free radical damage. As a result, it is advised to carefully consider the polyunsaturate to monounsaturate ratio in your diet.

To change the ratio of polyunsaturates to monounsaturates in your diet, the most significant thing you can do is use an cold-pressed extra virgin olive oil in preference to a polyunsaturated oil (such as sunflower, corn, blended vegetable oils). Avocados and sun-ripened olives are also rich in monounsaturates, as are some nuts, including hazelnuts, cashews, and almonds.

References:

Am J Physiol 1990, 258: C429–35

Am J Clin Nutr 1996, 64:960–5

Med Sci Sports Exerc 1991, 23:1028–34

 

 

 

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