If you lift weights you can rupture an aneurysm. If you sit calmly at work or at home, you risk increased coronary disease (which is why some people insist on saying that “sitting is the new smoking”). If you run or play volleyball, you can damage your knees. There is no way out of this, so you should do the things you enjoy. But know that in some cases, it will mess you up.

When it happens, it’s important to know what to do. Getting medical attention for every little muscle spasm will mean that you do nothing else in your life. Failing to get medical attention, or failing to coddle that damaged part while it heals, could increase the time it takes for you to get back to doing what you love and the cost of treatment.

AP medical reporter Lindsey Tanner has a nice overview of the kinds of problems active boomers face, and a few guidelines on how to differentiate self-treatable injuries from the ones that warrant a doctor’s intervention. One good rule: if the joint or muscle can bear weight, you’re probably OK to treat it yourself. (But if it doesn’t start improving in a few days, you better head down to the clinic.)

Also, and contrary to the t-shirts you see at the gym, pain is not weakness leaving the body. It’s usually your body telling you that you have a problem that probably isn’t going to leave any time soon if you don’t pay attention to it: “Injuries that need immediate treatment cause excruciating, unrelenting pain, or force you to immediately stop your activity and prevent normal motion.”

Tanner also addresses the value of consistency (don’t be a weekend Olympian), stretching (after, not before your exercise) and strength training.

Picking the right activities for your body and level of conditioning will brings all kinds of benefits. Doing it wrong—or not doing it all—also has consequences. Tanner points out that “knee replacements have more than tripled in people aged 45-64 in recent years and a study released last week found that nearly 1 in 20 Americans older than 50 have these artificial joints.” This isn’t necessarily a bad thing: there are people out there with two artificial hips or two fake knees that are leading very active lives, something that wouldn’t have been possible a few short decades ago. But it is so much better, and so much cheaper, to avoid those joint-destroying injuries in the first place.

Photo of one thing that can surely hurt you, from the 2010 Mavericks competition, by Shalom Jacobovitz via Wikimedia Commons