Cocoa Flavanols and Exercise Capacity

13 participants (highly-trained cyclist, accustomed to exercise testing on ergometers will be enrolled (VO2max\>50 ml/kg, FMD \>5%, non-smokers, no medication, no diseases, age 20-36, male). Baseline Testing: Participants will perform a baseline testing consisting of an ergometric test with a step-wise increase of workload until exhaustion to determine lactate anaerobic threshold and cardio-pulmonary exercise capacity. Vascular function is monitored by Doppler Ultrasound. In a second test, participants will perform a time trial (goal: as fast as possible) Flavanol intervention Participants will twice daily receive either a flavanol-poor cocoa drink (13mg/dl)or a flavanol-rich cocoa drink (596mg/dl) over a period of 7 days. Order is randomized and balanced. Subjects will crossover to the second arm after a washout period of 7 days. Testing performed on baseline day is repeated after the intake of both drinks In a subgroup of n=6 participants, we will test whether the blood pressure cuff maneuver used for FMD will itself modify nitrite levels. For this the manuever will be completed 4 times and compared to n=6 untreated controls. in another subgroup 6 participants will receive 4times the maneuver but reperfusion will be limited by means of an ultrasound probe.