Once upon a time, in a cozy little town called Flexville, lived a boy named Charlie with bright blue eyes. Charlie loved adventures but had never been on a muscle adventure before.

One sunny morning, Charlie woke up feeling strange. His legs felt like they had a mind of their own, and his arms felt wiggly like spaghetti!

At breakfast, Charlie told his mom about the wiggly feeling. 'Ah,' she said, 'you’ve got your very first muscle soreness from all that playing at the park!'

Charlie was curious. 'What's a muscle soreness?' he asked. His mom smiled and replied, 'It means your muscles are growing stronger from new exercises!'

To understand more, Charlie decided to imagine a tiny adventure inside his muscles. 'Let’s find out what’s happening in there,' he said with a giggle.

In his adventure, Charlie met Flexi the Friendly Muscle, who explained that when Charlie plays and exercises, his muscles work hard and sometimes need a break to fix themselves.

By the time Charlie's adventure ended, he felt tired but happy. 'Now I know my muscles are getting stronger!' he exclaimed. And with a yawn, Charlie snuggled into bed, ready for his next adventure in dreams.