Jay wandered into the gym for his daily workout. If he made his human form stronger, he got stronger as a Hulk, too. Also, it was easier to track progress as a human. Buildings tended to fall down if he pressed his Hulk strength.

He noticed Erin running on the treadmill. He shrugged to himself as he walked over to the weights and peeled off his shirt. He tossed it on top of his nearby towel.