Another thing I've tried a bit is called the Art of Kung or something like that. A man I caught a ride with taught it to me during my homeless nomad days; I'm not actually sure if it's an official training program, but the results were pretty impressive; he could do things I didn't even think were possible for an old guy his size.
One practice involved jumping in and out of a hole the diameter of your outstretched arms for hours on end. Not a super deep hole; pretty easy for a while. After a couple days of that, dig the hole a couple inches or so deeper, and jump in and out of that for a couple days, then dig it another couple inches deeper and jump in and out of that for a couple days, etc, etc, lather, rinse, repeat. Only continue to dig the hole deeper once you've mastered the current depth and it becomes easy for you. Then dig out another couple inches or so. Due to not having enough room for a running start, it has to be a vertical leap straight upwards. After years of dedicated training, I joke you not, you'll find yourself leaping in and out of a 15 foot hole in the ground; possibly even higher. Spider-Man level leaping ability lol.
Another practice entails wearing weights when you run. Start off with a lot of weight until you can run X amount of laps in X amount of time. Keep trying to get faster with all the extra weight on. Once you've mastered that level, take off a little bit of the weight, and master the next time limit you set for yourself. And so on, and so forth. By the time you finally get down to taking off the last weight, you'll be running like the wind; well beyond 20 mph. probably closer to 30 mph. Years of training in this method can enable someone to run nearly as fast as a car at 40 mph.
The Art of Kung is basically, (supposedly), an ancient practice that turns humans into superhumans through seemingly easy exercises that gradually get more difficult over the course of many years. Usually only Monks have that kind of patience and mental domination over their own bodies. Wanted to learn more; especially about the Tummo meditation techniques; monks would use it to melt circles out of the ice around their bodies by increasing their body temperature on command; another game they play is seeing who can dry the most wet towels on their backs in the mountains by heating the towels up via manipulating their own body temperature. Crazy stuff lol.
And those superhuman monks are teeny tiny; size really doesn't matter; a little old man just might throw a truck at you if you're not careful lol.
