Overtraining may cause (or result from) oxidative stress


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“Overtraining” is one of those terms that means different things to different people. For some, it means they’re tired because they went too hard for a few workouts in a row; for others — particularly elite endurance athletes — it’s a potentially debilitating condition that can take many months to recover from. The confusion arises in part because there’s no definitive definition of the condition, or any reliable way to predict or diagnose it.

Overtraining syndrome is characterized by an unanticipated reduction in performance, despite increased or maintained training challenges.

That’s the simplest possible definition, from a new paper in the Journal of Sports Sciences by researchers from Finland. The study joins the search for physiological indicators of what’s going on and why, focusing on oxidative stress. In the normal course of events, exercise causes oxidative stress, and your body’s natural antioxidant system responds to neutralize the oxidation. The more you train, the more powerful your body’s antioxidant defenses become.

The Finnish researchers studied seven overtrained athletes, and compared them to a group of matched controls. At rest, the overtrained athletes had higher levels of oxidative stress than the controls. When they exercised to exhaustion, the antioxidant response increased in the controls, but not in the overtrained athletes — and this was still true six months later. The conclusion: overtrained athletes are no longer able to adapt to the oxidative stimulus of exercise.

Of course, this doesn’t say anything about cause and effect. But it does add weight to the argument that overtraining syndrome — whose very existence, like chronic fatigue syndrome, is often debated — really does exist as a distinct physiological state. And the researchers suggest that one of the markers of oxidative stress in the study, protein carbonyls, has potential to be used for early detection of overtraining.