Exercise is commonly viewed to be beneficial for one's health. However, you may be surprised to learn that exercise can be detrimental too. Previous study in mammals, including humans, has shown strenuous exercise to produce free radicals, which increase the presence of reactive oxygen species that induce oxidative damage in cells and tissues. Specifically, reactive oxygen species have been shown to play an important role in the etiology of numerous serious ailments such as cancer, Alzheimer's disease and heart disease.

Nevertheless, there may be a simple way to continue exercising without suffering the consequences of the associated oxidative damage. Numerous fruits contain antioxidant compounds such as polyphenols and flavanoids that have been shown to protect against oxidative stress by functioning as reducing agents, singlet oxygen quenchers, and helpers in the repair of damaged DNA bases or protein amino acids. Thus, maintaining a diet supplemented with fruits high in antioxidant compounds could potentially serve to sustain the body's antioxidant levels and prevent exercise-induced oxidative damage.

Kriya Dunlap and associates at the University of Alaska Fairbanks were interested in determining whether a diet supplemented with a fruit high in antioxidant compounds would indeed elevate an animal's total antioxidant power and protect against oxidative muscle damage associated with exercise. As such,Dunlap's team devised an experiment to investigate whether supplementing the diet of Alaskan huskie (Canis lupus familiaris) sled dogs with blueberries would prevent oxidative muscle damage in these animals following strenuous exercise. The team maintained two groups of 12 dogs for two months with minimal exercise on either (1) a normal dog food diet or (2) a supplemented diet in which 2% of the daily food intake was blueberries. At the end of the two-month acclimation period, both groups of dogs were exercised on two consecutive days for 30 min each day at 70% of their

\({\dot{V}}_{\mathrm{O}_{2}}\)
max. Blood samples were taken prior to, immediately following and 24 and 48 h post-exercise for measurements of plasma creatine kinase and isoprostane-indicators of muscle damage - and total antioxidant power. Measurements were compared to a control group of dogs that were fed a normal dog food diet over the two-month adaptation period but were not exercised at its conclusion.

The team found that supplementing the diet of young healthy sled dogs with blueberries failed to attenuate the muscle damage associated with the exercise regime. Both groups of exercised dogs exhibited a slight, but not unusual,amount of muscle damage following exercise. However, the blueberry-fed dogs did have a greater total amount of antioxidants present in blood plasma immediately post-exercise, but not at 24 or 48 h following exercise. From this finding, Dunlop's team surmise that the blueberry-fed dogs had the potential to be better protected against the deleterious effects of oxidative stress. Thus, it appears the old saying holds true, `you are what you eat'!

References

Dunlap, K. L., Reynolds, A. J. and Duffy, L.(
2006
). Total antioxidant power in sled dogs supplemented with blueberries and the comparison of blood parameters associated with exercise.
Comp. Biochem. Physiol.
143A
,
429
-434.