A team of Swiss researchers found that when a hormone in the brain, erythropoietin (Epo), was elevated in mice, they were more motivated to exercise. In addition, the form of erythropoietin used in these experiments did not elevate red blood cell counts. Such a treatment has obvious benefits for a wide range of health problems ranging from Alzheimer's to obesity, including mental health disorders for which increased physical activity is known to improve symptoms.