True, it cuts down on your gas bill and reduces your carbon footprint, but the most obvious reason for leaving your car in the garage tomorrow for Bike to Work day is right under your nose—or at least several inches below your nose: your heart. Aerobic exercise strengthens the heart muscle at the same time that it helps keep weight, cholesterol, and blood pressure at healthy levels. It may also reduce arterial inflammation, which increases heart-attack risk, and slow the progression of heart disease.

Need another reason to bike? It can stave off arthritis. A recent study suggests that women with stronger quadriceps (the muscle at the front of the thigh) are less likely to get painful knee arthritis.

Thirty minutes of moderate-intensity exercise most days of the week can start with a brisk walk or a jog—but if walking bores you and running is hard on your knees, biking might be just the thing that helps you start or re-start a healthy habit.