Climbing shoes fit very closely to support the foot and allow the climber use small footholds effectively. Many climbers do not wear socks inside their climbing shoes to achieve a more precise fit and prevent their foot from slipping inside the shoe.
Most climbing shoes, particularly the more aggressive or technical styles, are uncomfortable when properly fitted; a common adage among climbers is, "If your feet don't hurt after climbing, then your shoes are too big." A primary reason for this is that aggressive climbing shoes force the climber's toes into a curled position, which puts the climber's weight on the tips of his toes rather than the pads, giving him much more strength and stability on small foot- and toeholds.
Source: scarpa.comAdded: 12 December 2009