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Impact of endurance exercise on levodopa associated cortisol release and force increase in patients with Parkinson's disease
Background: Levodopa (LD) application improves motor symptoms and reduces cortisol levels, whereas the impact of LD on force development and coordination is matter of debate in patients with Parkinson's disease (PD), who report reduced exercise capacity. Endurance exercise enhances cortisol release in proportion to the intensity of the effort in particular in the morning and thus may counteract the LD associated cortisol decrease.
Methods: We measured levels of cortisol and LD over an one hour lasting interval following administration of soluble 200mg LD/50mg benserazide with concomitant maximal grip strength assessment in 16 PD patients under cued conditions with stress avoidance during rest and endurance exercise on two separate consecutive days.
Results: The motor response, the plasma levels of cortisol and LD did not significantly differ on both days, but cortisol concentrations significantly decreased even during the exercise condition in PD patients unlike in healthy subjects, who experience a cortisol increase. Grip strength only significantly went up during the rest condition.
Conclusion: Endurance exercise did not counteract the LD associated decreased cortisol release, which may partially be responsible for the complaints of PD patients during and after performance of exercise, since cortisol improves muscle function. We suggest, that the missing increase of maximal grip strength following LD administration during exercise was misinterpreted as reduced exercise capacity by PD patients.