So, there is data that people who are physically active, including runners, actually have less arthritis than people who don't run. That's one thing. However, there's also data that if you have an injury due to running or something else, and you then do that kind of high impact exercise, you'll actually increase your risk of joint damage and possibly go on to arthritis. So, it really comes down to whether or not you've had an injury and many older adults that I'm a geriatrician. So, I see older adult; and certainly, arthritis of the knees is one of the most common problems that we see and in those individuals, who already have arthritis, we certainly don't recommend high-impact exercise. But you can get high intensity aerobic exercise by doing something like stair-climbing or walking up an incline, for example, or alternatively, you can do weight-lifting exercise. Which is a lot of the time actually far more tolerable for people with lower extremity arthritis than is even simple walking. So, there's certainly ways to get high intensity, robust versions of exercise without resorting to high impact exercise. If you have joint damage.