Leg speed is, simply, the speed your legs will move without you trying to move them faster. You have a certain leg speed on a bike, and another one when running, or, eventually, walking. Because leg speed decreases over time in the same way that entropy increases, or because of it.
How many times have I been out on an epic ride, cracked like a robin’s egg dropped from the nest, and then fallen back to leg speed to get myself home? Lots of times is the answer. My companions, if they stay loyal, wondering how it is that we can be moving this slowly and still staying upright.
In the midst of a blood-sugar crash, I often calculate the distance home and think, “Yeah. I think I can get there on leg speed alone.” It’s quite a consolation. It means I can crawl away, lick my wounds, and fight again another day. Honestly, on the occasion this scenario materializes, I much prefer to be by myself. The pity escort just compounds the damage to ego.
I’m not even really sure what leg speed is made of, and if you’ve ever wondered, “How are my legs still going round and round?” then you know what I mean. As best as I can tell, the weight of your legs has a certain momentum in the captive arc of the pedal stroke. Obviously, that momentum isn’t perpetual. You have to put something in, but if you can put in just enough to keep the rolling momentum up, you can keep going.
It’s less like pushing the pedals and more like just lifting your quads the length of your cranks, likely between 170 and 175mm.
The trick is not to stop rolling, because then you have to build that momentum again, from scratch…or from Skratch I suppose. In my experience, the leg speed you have when you come to stop is not necessarily equal the speed you have when start again, especially if you opted to lie down on the ground.
Of course, the real compromiser of leg speed is incline. I can still feel the hurt in my soul from crawling up wet, gritty mountainsides in Vermont mud season. On two wheels and headed uphill, there is no equivalent to walking, unless it’s walking, and that is a step I just can’t take, but have.
When I am toast, when I am travelling under leg speed alone, there is a clock ticking in the back of my head. Assuming I don’t have calories I can add to equation, I know that I will reach a point of diminishing leg speed that will lead to stopping, or falling over, or making the phone call of shame, and of those options, I am not sure which is the worst.