This study investigates changes in glymphatic flow in the brain acutely after vigorous-intensity steady-state aerobic exercise. Twenty subjects (10 male and 10 female) perform 25 minute submaximal cycle ergometry exercise and the changes in the glymphatic flow and cerebral perfusion are evaluated using a variety of MRI sequences (e.g. MREG).

The glymphatic system is a drainage system for the brain to help maintain fluid balance and extract waste metabolites. Glymphatic system function (healthy glymphatic flow) may prevent accumulation of harmful substances and therefore slow down the onset of neurodegenerative diseases.

The hypothesis is, that glymphatic flow could be increased through exercise and enhanced cerebral arterial pulsality, which might explain some of the brain health benefits of exercise proven in epidemiological studies. This study indirectly investigates the acute changes in the glymphatic flow acutely after aerobic exercise using MREG that measures pulse wave propagation as an indirect surrogate marker for glymphatic flow.

Twenty healthy subjects (n=20, 10 male, 10 female, age 18-45 years) will perform 25 minute 70%VO2max cycle ergometry exercise. The glymphatic flow and cerebral perfusion will be measured using magnetic resonance imaging sequences before and after exercise. The glymphatic flow is measured using 10 Hz fMRI technique called magnetic resonance encephalography (MREG). In addition, perfusion MRI is used to evaluate changes in brain perfusion.

Inclusion Criteria:

• Age 18-45
• BMI 18-30
• Resting Blood pressure < 140/90 mmHg

Exclusion Criteria:

• History of a cardiac event
• Insulin or medically treated diabetes
• Any chronic disease or condition that could create a hazard to the subject safety, endanger the study procedures or interfere with the interpretation of study results
• Presence of ferromagnetic objects that would make MR imaging contraindicated
• Claustrophobia
• Abundant use of alcohol
• Use of narcotics
• Smoking of tobacco or consuming snuff tobacco
• Diagnosed depressive or bipolar disorder
• Abnormalities in resting ECG (revised by the study physician)
• Pregnancy