A short rest allows a creature to regain the use of encounter powers and spend healing surges to regain hit points. Short rests follow these rules.
Duration: A short rest is about 5 minutes long.
No Limit per Day: A creature can take an unlimited number of short rests per day.
No Strenuous Activity: Resting means just that. The creature can stand guard, sit in place, ride on a wagon or other vehicle, or do other tasks that don’t require much exertion.
Regain the Use of Powers: After a short rest, a creature regains the use of expended encounter powers.
Spend Healing Surges: After a short rest, a creature can spend as many healing surges as desired (see “Hit Points and Healing,” page 255). A creature that runs out of healing surges must take an extended rest to regain them.
Using Powers during the Rest: If a creature uses an encounter power (such as a healing power) during a short rest, it needs another short rest to regain the use of that power.
Interruptions: If a creature’s short rest is interrupted, the creature needs to rest for another 5 minutes to get the benefits of a short rest.
Published in Player's Handbook, page(s) 263, Rules Compendium, page(s) 172.