JUPITER, Fla. — We are all familiar with that stereotypical picture of a lifeguard, what with the rakish spin of his whistle and that universally accepted symbol of smart, outdoor health — the white stripe of sunscreen on his nose. It’s not a fashion statement. It’s there because it’s needed. Through many years as a lifeguard I’ve peeled off more noses than I care to admit, and I’ve got the freckles seven layers deep to prove that I should have been more vigilant with my white stripe. I imagine that every profession or pursuit that puts in the line of (sun) fire has that same soft spot that the rays find and punish. When I coached swimming, we were constantly reminded to put a swipe of sunscreen on top of our ears where our sunglasses rest. That’s where coaches are vulnerable, we were told, and skin cancer can nest. Snorkeling can leave your back exposed to the sun’s raw brutality as I learned last month in Curacao. Construction workers have to be wary of their necks. Golfers have to be mindful of their foreheads. Skiers have to remember the sun can ricochet off the glistening snow to double-blast their cheeks and even when you can’t see the sun its rays can still seer you. Drivers have to take special care of that left elbow, poking out into the sun as it does while they’re cheerfully rocking out to AC/DC on a road trip. (I’m thinking Emilio Estevez in Maximum Overdrive.) And baseball writers must always remember the tender spot behind the knee. I am reminded of this tonight as I sit to write and the little prickles have started. Out of sight and out of mind, it’s the backside of the knee that gets burned if ignored. There is a lot of standing in spring training. Standing around waiting for an interview. Standing there talking to the manager. Standing there to watch live batting practice. Standing for the National Anthem. Standing there filming a bullpen with an iPhone I can’t quite hold steady but, dagnabbit, I’m trying. Standing. Standing. Standing. All of that standing means being in the sun, and that gives the sun just enough time to poke around and find the softest spot it can reach and bake. The backside of the knee is a crucible for burns, and writers forget to rub in the sunscreen at their own peril. Eventually as a writer you will get to sit down to type and that’s when you find out what the sun has been doing all day behind your back. So when you visit spring and you see a baseball writer with two pools of sunscreen lathered on the back of his or her knees, remember the lifeguard. That white stripe on the nose is not only cool it’s preventative. The back-knee sunscreen is just like that. Preventative. Not cool.