My ADHD daughter likes to run across the room and then slide as far as her momentum carries her on my hardwood floors. This is a fun pastime for her and one of the ways she expends excess energy. This behavior has been going on for years, and since she is now legally an adult I'm thinking she may not outgrow this hyperactivity. I can picture her in advanced years, gray hair pulled back in a pony tail, attaching waxed wheels onto her walker and scooting across the nursing home floor. Over and over.
So, okay, as someone who struggles with fatigue problems I admit to being envious of the energy that hyperactive people seem to have in spades. But here is the baffling part - my hyperactive children can go from full-speed to sloth-speed just like that. During our homeschool day, Josh would wiggle and squirm until we took a break. Then he'd run around like a cyclone until I called him back to the table for our next school subject. After reluctantly returning to his chair, Josh would go from full-on energy to extreme lethargy in a matter of seconds. He would slouch and prop his head on his hand as if it took too much effort to hold his head up without support. Often, this child who needed way less sleep than I did would begin to yawn. He appeared to be anything but hyperactive. What's going on?
I've also observed that despite obvious hyperactivity much of the time, when I actually need Josh to move quickly he seems incapable of doing so. In fact, the more Josh is urged to hurry up, the pokier he becomes. Despite encouragement (and some yelling and begging) with increasingly desperate exhortations that we need to leave right away or we will be late, Josh doggedly has one speed, and that speed is slow. Slow, methodical, and plodding are not my idea of hyperactive. The more pressured and hurried Josh feels, the slower he seems to move. Even telling him to "Run!" doesn't work. He might trot a few steps at most and then return to his set pace. It's aggravating, but Josh isn't being deliberately obstinate or difficult. Again, what's going on?
Josh, like many children with learning challenges, had difficulty regulating his state of alertness. He tended to manifest extremes - high energy or slug-level energy, with not much in between. Josh couldn't explain what was happening, because it was all he ever knew so it was his "normal". I tried dietary interventions, thinking he was experiencing some kind of physical crash. Except it was only happening when Josh was asked to engage in tasks that demanded sustained attention and a relatively still body. My dietary interventions had no effect with Josh. I tried having him sit on a hard wooden (uncomfortable) chair so he couldn't get overly relaxed. This, too, had no effect. I offered ice water for him to sip, an inflatable cushion disk or therapy ball to sit on, fidget toys, and other sensory strategies, and over time we were able to find some things that helped some of the time. I'm still looking for anything that actually helps all of the time. It is my dream and quest.
For parents

God bless our amazing children, who force us to become better teachers than we ever wanted to have to be! But we are better teachers now, because these struggling learners have stretched us far beyond what we thought we knew. We are so much richer because of them.