Have you ever heard of "sewing machine leg"? I hadn't either, not until I was 100' up a cliff in an area of New York called The Shawangunks (or just The Gunks if you're cool). Here's a description of the climb I found online: "Climb up from the ledge and traverse right to the obvious place to turn the corner and make "The Move" to pull the roof - the exposure is immediate and the rock is steep! Continue up the face past gear, jugs, and fixed pins, trending left back towards the arete, until you top out. Exhilarating!" Sure, exhilarating once you're standing safely on the top! To clarify, what "pull the roof" means in this case is you scramble up the wall, under, and then over the roof of the little ledge that you've been safely sitting on. And "steep" doesn't just mean vertical. It means the rock tilts back towards the valley below. Try to picture yourself, clinging to the rock wall like a frightened monkey, having somehow managed to just scramble out over the roof, with gravity pulling at your back, and suddenly your leg starts jumping up and down uncontrollably. You look down and you've got a leg, the same leg that's trying to keep you connected to solid rock, flopping around like a dying fish. No amount of "what the .... "s seem to solve the problem. But there's really only one thing to do - climb on. When I reached the top of the climb and told my partner about my leg situation he said, "Oh! You had sewing machine leg!". So apparently that's a thing. I've read some climbing sites that say it's a buildup of lactic acid, or the way you're placing your foot that puts a lot of strain on your calf muscle, or as one forum poster put it, "Pure and simple ScareDeeCattedNess!". Whatever it is, it's uncomfortable, surprising, and certainly not an efficient way to climb.
I was 25 when I did that climb. There were a few climbs that followed, but I haven't climbed at all in the last decade so I've started going to the local climbing gym in preparation of my Grand Teton climb. The summit of the Grand will require a few pitches of some actual rock climbing and I certainly don't want to be 13,000' off the ground and have another attack of sewing machine leg. Although I anticipate a certain degree of ScareDeeCattedNess, I'm hoping that with some fitness, mental preparedness, and a healthy dose of confidence I can keep that floppy leg under my own control. Wish me luck!