Ischemia reperfusion injury may be reduced by ischemic preconditioning. This projects aims to show the effects of short and long time ischemic preconditioning (both sequences 3 x 5 minutes) during and after an ischemic period of 20 minutes in healthy subjects by functional MRI. Ischemia is produces by cuff inflation to a suprasystolic pressure on one tight. Signal is acquired from calf muscles.

A cross-over design of 4 to 8 study periods is used, 4 different study days with 2 different MR measurement methods (BOLD imaging and high energy phosphates) are planned.

Inclusion Criteria:

• Men aged between 18 and 45 years
• Nonsmoker for more than 3 months
• Body mass index between 18 and 25 kg/m2
• Normal findings in medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant

Exclusion Criteria:

• Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
• Evidence of hypertension, pathologic hyperglycemia, hyperlipidemia
• Treatment in the previous 3 weeks with any drug including over-the-counter drugs
• Symptoms of a clinically relevant illness in the 2 weeks before the first study day
• Blood donation during the previous 3 weeks
• Any metallic, electric, electronic or magnetic device or object not removable
• Claustrophobia