After the long Holiday weekend, you may have lapsed in your workout routine. Heading back into your workout, you may experience a bit of soreness, especially if you worked out harder than normal. This terrific article by Cathe Friedrich, explains delayed-onset muscle soreness and what you can do to prevent it.
Cathe Friedrich - Delayed-Onset Muscle Soreness or DOMS: What Causes It and Can It Be Prevented?