He bit his lip to keep from groaning as he crouched down low to grab out the bag for the woman.
It wasn't her fault that his legs were sore.
It wasn't her fault that the store had placed product so low on the shelves.
Nor was it her fault that his legs were no longer used to crouching so much during a regular work shift.
But by golly. He didn't want to be here any longer.
A hot shower, a day in bed.
That was what he needed. 
To help his sore muscles relax.
And not keep pushing them to the limit trying to help others.

-Inspiration from being at work and having sore legs