Workout conundrum: Is that good pain or bad?

No pain, no gain. We've all heard it, and some people wear it like a badge of honor after a hard workout.

But is it true? Can pain really be a good thing?

"Yes, in a way it's true, but we have to distinguish between good pain and bad pain," says Elizabeth Brooks, a personal trainer.

Muscle soreness after exercise is often a sign of delayed onset muscle soreness, which is the feeling we get when our muscle fibers tear (during workouts) and then repair (during rest and recovery).

"You have to push past your comfort zone to get gain," Brooks says. Even the most fit people can get muscle soreness if they do something new or add duration, intensity or external load to their exercise.

But the problem with "no pain, no gain," says Winston Gwathmey, an orthopedic surgeon at the University of Virginia, is that it can be tricky to distinguish between good pain and bad pain. "Some people have a high threshold for pain, and others can't tolerate it at all," he says.

But there are a few pretty universal signs to look for as we try to distinguish between the good and the bad.

The good

• Muscle soreness after workouts that goes away after 48 hours

• Soreness that is felt equally on both sides of the body. (For example, if you're doing a bench press and the left shoulder is hurting but not the right one, that could be a sign of an injury, Gwathmey says.)

• Pain that can also be described as a muscle burn or fatigue (as opposed to a sharp pain)

• Discomfort that is located in a muscle, not deep in a joint

• Discomfort in the area targeted by the drills (for example if you're doing a plank it should be felt in your abs, not your back)

• Clicking and popping in a joint without pain

The bad

• Sharp pain

• Pain deep inside a joint

• Pain only felt at a particular angle during a movement or exercise

• Pain that doesn't subside after 48 hours

• Stiffness and swelling after an exercise

• Pain felt in an area not targeted by a drill (for example your back hurts when you're doing situps)

• Pain on only one side of the body even though you're doing a movement that is bilateral (for example bench press)

• Clicking and popping in joints accompanied by pain

Sometimes pain is caused by a traumatic injury and you have no choice but to stop the activity and seek medical help - like tearing your ACL while skiing. But often sports injuries happen over time when people do too much, too quickly, Gwathmey says. "You have to let the body adjust over time."

Brooks says sometimes new clients come in thinking they can pick up where they left off as college athletes - two decades ago!

"That's completely irrelevant. If you haven't worked out for the past six months to a year you are a beginner," she says. "You might still have good coordination, but you're still a beginner."

That means starting easy with lots of body-weight exercises, focusing on the core and doing 20 minutes of no-impact cardio as the body - muscles, tendons, ligaments and bones - gets used to the extra stress.

The goal is to create muscle balance and range of motion, Brooks says, so exercises can be performed accurately. Otherwise, "bad" pain is likely to be felt in the "wrong" place.

Says Christopher Ricardo, a physical therapist: "If you're doing a situp you should feel it in your abs, not in your back." In other words, be mindful as you go through your routine - with or without a trainer - that you're feeling the mild burn in the targeted muscles as opposed to any joint pain. Watch also for muscular pain in a non-targeted area.

"Also if soreness or pain is affecting how you're moving during your workout - that's not a good thing," Ricardo says. It can cause you to use bad form, which might cause or contribute to an injury. If you lack range of motion in a hip flexor, for example, it can cause you to lean forward in your lunges, which over time can create knee pain.

In the end, it's about listening to your body, Gwathmey says. Everyone needs to develop his or her own wisdom about levels of discomfort and what those mean. If it's sharp or deep or lasting, it needs to be respected and addressed.

"Pain is a sign that your body is experiencing something that isn't good for it," he says, noting that this may be more difficult to interpret for someone new to exercise.

Or, as Brooks puts it: "You should be back in the saddle in a week - at the most. If not, it's time to go to the doctor and get it checked out."