Like ordinary shoes, running shoes consist of an upper and a sole. But there the similarity ends, as the cutaway of the shoe below shows.

The upper. These days, leather is out; most running shoes have breathable synthetic mesh. The toe box should be roomy enough to let toes spread. The heel counter should keep your heel from slipping excessively.

The midsole. Or middle layer provides most of the cushioning. The midsole is usually made of shock-absorbing foam and may incorporate gel or air sacs and plastic torsion supports.

The insole. Or sock liner, is the layer nearest the foot, provides added shock absorption and arch support. It's removable and washable in all the shoes we tested.

The sole. The bottom layer, usually carbon rubber, is segmented for flexibility and grooved for traction.

The reflector. Some uppers have large reflective areas, for those who run after dark.

Lacing. Fabric, plastic, or metal speed-lacing loops make tightening easier. Extra top eyelets provide a snug fit at the ankle.