I would think that there are many who've experienced the same / similar. While not challenged by another cyclist, I faced a headwind for most of an 80 mile ride last week with about 2,800 ft of climbing. The calf muscles were tightening by half way, but I managed to keep them from cramping, and finished the ride in my usual time. I was definitely dehydrated though despite eating and drinking what my experience would suggest is enough for this distance and effort. Two weeks earlier I rode a similar ride with the same distance and 7,300 ft of climbing which I sailed thru without a hiccup. Was the wind really that big of an influence this last weekend? Or perhaps it was the hill climb ride the night before? I don't know. It just happens I guess.