Testing
Over the rest of the days since his discovery, Harry spent most if not all of his waking hours just sending and feeling the sensation. A tingling that made the affected area shake and stiffens. When he was released, he created the sensation in his arm and saw veins of this bluish energy snake from his elbow all the way to his wrist where it circled and seemed to wait. When he attempted to move the energy, it vanished into his body, and he felt warm and relaxed.
7 ½ - 8 years old
It took months of searching, an in-depth study, for reasons unknown to little Harry, into basic human anatomy’ courtesy of the local libraries non-fiction section. It took a fair bit longer to get what he was looking for across to the librarian, but he eventually succeeded and learned. Due to his dehydration and malnutrition (one of the only times he’d ever thank the Dursley’s), his veins were incredibly prominent down his arms when he rolled his sleeve. Summoning the blue lines again, he noticed that they followed his veins and that it caused his muscles to contract and tense.
8 ½ - 9 years old
Harry had a fairly concrete grasp, at least the basics, of his new power. He learned that through channeling this as of yet unnamed energy through specific muscles, he could augment his strength and/or speed. It was after one particularly vicious beating, where Harry wanted nothing more than for it to stop, that the energy flashed just so each of Uncle Vernon’s blows caught the boy in a state of transition, minimizing the damage. He gained finer control, being able to do select muscle groups instead of an entire extremity or section thereof.
It wasn’t long after he finessed his control to be able to do just his palm or fingers, not both, that he found a new property of this energy. If he let it stew while consistently moving it around, he could almost get it to radiate and could draw funny shapes in the air.
9 ½ years old
He was stuck outside, and it was snowing. Of course, the Dursleys locked him out, they were exactly the type to do that for a laugh. As he started wandering, mostly to try and keep warm through movement, he decided to Dash, which was when he summoned and expended this energy down with each step to greatly increase speed, he felt decidedly warmer in his lower legs than the rest of his frail body. Deciding to test this new phenomenon, he pulsed the energy, sacrificing his hard-won control for quantity and speed. He felt marginally warmer, and he kept doing that until he returned to 4 Privet Drive, tired but excited for new abilities to find the door unlocked and only his aunt awake.
10 years old
One of the few times the Dursley’s forgot to lock the cupboard, Harry snuck out to try and get some food, for he hadn’t eaten in several days. In an attempt to quiet his steps, he pulled as much energy away from his feet as he could. While eating several day old leftovers that were never going to be eaten. He heard a creak come from the stairs. In one of the few circumstances where this energy worked, if not independent of his, then certainly with no conscious thought, his vision filled with blue, and the completely dark room, lit by naught due to the new moon in the sky, suddenly was filled with rough outlines of furniture, his right eye seemed to focus on the stairwell with greater acuity than was normal, and he could hear his aunt sleeping upstairs. Considering that both Dudley and Vernon could understandably be mistaken for passing locomotives, that was an incredible feat in itself. Concluding that it was the house creaking after several long moments of staring and listening, Harry attempted to consciously pulse the energy in the same way it did on its own. Being unsuccessful in this endeavour although his hopes were not dashed, he went to bed, slightly filled stomach and brain working on figuring out these new features of this mysterious energy.
A little under a year later, a letter came. Along with a Very Large Man.