She rubbed a sore spot in her lower back.
She tried to work the muscles in her lower back with her fingertips, but the effort was worse than the benefit.
He ran his hand down her arm and rested his hand at her lower back.
That probably explains the dull ache in my lower back that I have all the time!
You have much less shortness of breath during your workouts, and that nagging occasional ache in your lower back has somehow disappeared.