They say laughter is the best medicine. That may be true… if you are laughing while you exercise, because the health benefits of a good workout are undisputed.

Many of exercise’s benefits, particularly for neurology patients, are hard for available medical treatments to match. Exercise is associated with decreased cardiovascular mortality, including stroke. It may also delay cognitive decline in the elderly.

But unlike medications and procedures, it’s much harder to quantify how much of this great medicine your patients get. Evidence shows when physicians counsel their patients about physical activity, the results are good—patients tend to take their doctor’s advice and exercise more. But as a physician, you must often work with your patients’ best recollections of how physically active they are, so making specific recommendations can be difficult.

Luckily, there is a great way to tap into a treasure trove of this information. Simply log in to your patients’ fitness trackers.

Many of your patients probably already use them, and if not you may recommend purchasing them. The technology on these devices provides a surprising amount of detail about the wearer’s activity for prices ranging from under $50 to well over $200. That may sound expensive but relative to a lifetime of prescription medication, it’s a steal.

If you have your patient connect with you as a friend on the online dashboard offered by many of these devices, you can see great detail about their activity level. For example, Fitbit will allow you to view a 30-day graph of steps and distance as well as 30 days worth of activity broken down into time spent being sedentary, lightly active, fairly active or very active.

With this information at your fingertips via phone, tablet or laptop, you can personalize physical activity counseling. Perhaps your patient thinks they are exercising more than they really are (recall bias never seems to skew the other way). Or maybe they don’t need to exercise more, they just need to up the intensity a bit. You won’t be making general recommendations anymore; you will be giving your patients advice specifically tailored for them.

This information is available to you without any investment in new technology. You don’t even have to have a tracking device yourself to set up a free dashboard account. So why not give it a try? Start with your patients who already use the devices and see what kind of results you get. Once they’ve got the exercise down, you can move on to getting them to laugh a little more.