You've reduced your calories and increased your activity and finally, theweight loss is starting to show. Then one unsuspecting day you don your workoutclothes, tie on your sneakers -- and the next thing you know, you're yelping inpain.

Experts say a workout injury can happen to anyone, regardless of experienceor conditioning.

"A pulled muscle, a strained back, a turned ankle, a shoulder sprain --it can happen in the blink of an eye, usually when you least expect it,"says Todd Schlifstein, DO, clinical assistant professor of physical medicineand rehabilitation at New York University Medical Center.

According to sports medicine specialist Robert Gotlin, DO, the mostvulnerable areas for pulls and strains are the hamstring and thigh, followed byleg or calf muscles.

If you're a beginner exercising to lose weight, the risk of injury may beeven greater, with hot spots that also include knees and ankles.

"If you are overweight, the most common injury is a sprain occurring ineither the ankle or the kneecap," says Gotlin, director of orthopaedic andsports rehabilitation at Beth Israel Medical Center in New York. This problemoften occurs when surrounding muscles are weak due to a lack of exercise, hesays.

"The more out of shape you are when you start to work out, the greateryour risk of injury, particularly if your muscles are weak," saysGotlin.

Pain vs. Soreness: Know the Signs

Even if you're already in good shape, experts say problems can occur if youoveruse any one set of muscles. To keep this from happening, ease into theactivity slowly and never skip warm-ups.

"For example, take five minutes out to stretch your muscles beforejumping on that treadmill or bicycle, and don't push yourself to the point ofpain -- even if you have done the routine before," says Schlifstein.

Some more advice: Stop immediately if you do feel pain, and rest for a day.If pain begins when you do the same motion again, says Schlifstein, it's a surebet you've got an injury.

But how do you know you've got an injury and are not just sore from workingout?

"Soreness usually shows up one or two days after you work out, and doesnot usually occur while you are actually doing the activity," says RichWeil, MEd, CDE, an exercise physiologist at St. Luke's-Roosevelt Hospital inNew York and consultant for the WebMD Weight Loss Clinic.

If you try to work out when you're feeling sore, the pain usually subsidesafter 10-15 minutes of activity, Weil says. Not so when an injury isinvolved.

"Pain related to an injury gets worse when you are working out,"says Schlifstein. "That's when you know it's time to stop and listen toyour body."