"Growth spurts?" you asked incredulously. "You mean like what gave you all those extra muscles and stuff?"
"No," Alex grinned, "the muscles are the main part of the drug, remember? No, the growth spurts are just pure increases in height, anywhere from a few inches at a time to several dozen feet. There's lots of factors that go into it, like what I've eaten that day and how much, how hydrated I am, and some other stuff I haven't quite figured out yet. But once I start growing, there's only one way to get me back to my original height."
"Which is?"
Alex continued to beam at you, shaking his head. "Ah, you don't remember, bro? Well, this time I'm just gonna let you find out on your own. It'll make it more fun that way."
You stare in amazement as your brother starts to stretch his legs. Growth of up to several dozen feet at a time? And only one way to get him to stop? You had no clue what that could be, but you had a bad, uneasy feeling in your gut.
"Okay," you finally said, trying to choose your words carefully, "so if you grow, then--"
"Hold that thought!" Alex interrupted. "It's starting to-- OHHHH!" He closed his eyes, his face contorting in something between pleasure and pain. You heard his bones begin to creek and his muscles started to vibrate, and his body began to get bigger. He went from being shorter than you by a few inches to your height in just a few seconds, and he wasn't anywhere near done.
"What the hell?" you asked, stepping back as Alex started to stretch higher and higher. His swim trunks were getting very tight, and the white sleeveless t-shirt began to rip all over, finally falling to his feet, letting his ripped chest and abs breathe.
"Ahh, that feels better," Alex said. You noticed he's stopped growing now, but appears to be almost seven feet tall, much bigger than anyone else on the beach. He flexes some more, testing out his muscles at his new height. Smiling, he looks back at you and says...