A couple of days ago I did the "Around the Bay in a Day" ride around Port Phillip Bay in Victoria, Australia. Its a 215km ride, but in total on the day I rode 238km including to and from my house. I have noticed that often after I do a ride of this length, I get "cold/flu" symptoms for a couple of days after the ride. This may include headaches, sniffly nose, scratchy throat, hot/cold feelings and weary body. Nothing really bad, its not like I get really sick, but I often feel like I am on the edge of coming down with something. Its almost like my body has trouble regulating its temperature after riding, and its weird, because I feel great when I am actually riding, and I always make sure I am warm/cool enough during the ride. I am wondering if there's anything I may be doing wrong, or if theres any way of avoiding these symptoms.