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Br J Sports Med. 2007 Feb;41(2):101-5. Epub 2006 Nov 30.

Effect of off-road competitive motocross race on plasma oxidative stress and damage markers.

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Research Center in Physical Activity, Health and Leisure, Faculty of Sports Sciences, University of Porto, Porto 4200-450, Portugal.



To analyse the effect of an off-road motocross heat on plasma levels of oxidative stress and damage, blood leucocyte counts and urine catecholamine concentration.


Plasma contents of total, reduced and oxidised (GSSG) glutathione, %GSSG, malondialdehyde (MDA), protein carbonyl and sulphydryl groups, total antioxidant status (TAS), uric acid, and blood neutrophil and lymphocyte counts were evaluated in 10 male top-level riders before, immediately after (0 h) and 1 h after a simulated competitive motocross race. 24-h urine adrenaline, noradrenaline and dopamine concentrations were also measured.


The motocross heat resulted in an increase in plasma oxidative stress and damage (p<0.05). This was shown by a significant increase in %GSSG, TAS, MDA and carbonyls, and by a decrease in sulphydryl groups after the race. There was a significant increase in both plasma uric acid and urine catecholamine concentration after the race (p<0.05). Blood neutrophil counts increased at 0 and 1 h after exercise (p<0.05). Lymphocyte count increased from baseline to 0 h, although it decreased from baseline and 0 to 1 h after exercise (p<0.05).


The data reinforce the marked metabolic and hormonal demands imposed by motocross, resulting in a condition of enhanced plasma oxidative stress and damage.

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