The present study will investigate the effects of aerobic exercise on cognition and growth factors including brain-derived neurotrophic factor (BDNF) in young adults aged 15-21 years. The included subjects will be randomized to three different groups including one control group and two exercise groups. Subjects randomized to the exercise groups will complete 30 minutes of aerobic exercise 3 times a week for 9 weeks incorporating low (group I) or high (group II) intensity aerobic exercise. The exercise will be conducted as running or indoor cycling (supervised). At baseline and 9-weeks follow-up all subjects will complete two cognitive tests (measures of concentration and sustained attention), a maximal cycling test (direct measures of VO2max), an intelligence quotient test, anthropometric measures, fasting blood samples and blood samples immediately following the cycling test. The blood samples will be analyzed for growth factors including BDNF and metabolic factors.

Inclusion Criteria:

• age 15-21

Exclusion Criteria:

• injury preventing one from being physically active