With Rick L (a strong rider). Emerging from "the land of the ice and snow," the weather today was good for a change: mostly sunny, mid-40s to low 50s F, and the winds at the start were only 6mph but got to 12 mph by the end. Mostly they were crosswinds, but there were some unexpected headwinds (in the second half, of course). Startled a guy with his dog (not close, he just didn't realize anybody was nearby), but he recovered enough to courteously return a friendly hello. Even tho the distance has been no big deal in the past (including last month), I struggled mightily today. My thigh muscles and my knees hurt, and I even had a short spell of dizziness (very unusual). Lots of cramping, too, even tho it was not warm and I was diligent about taking my Saltstick capsules. Then Rick suggested it might be related to my first Covid-19 vaxxing, which took place less than 2 days ago. I hope that's it. I'd hate to give up these 100kms, but I have no intention of continuing if they are going to be suffer-fests.