Your liver is not down by your Lower back so don't worry about that....

There are two things I can think of...

1. This is the most likely issue I can think of from what you have given us... Go to a running shop and ask them to monitor your running style and see if your pelvis/ hips are rocking from side to side.... You have 2 muscle called 'quadrants lumborum', they originate on the iliac crest/ hip and insert on the lowest rib and then L1, 2 and 3 (lower spine).... They are there to keep your hips square and support the lower spine..... Running can overtrain these muscle as you can imagine when your foot lands the hip wants to move up.... The opposite QL prevents this by contracting.... You may have some kind of repetitive strain injury that just requires some rest and maybe a little deep tissue therapy....


2. The other thing I can think of is that your lower back is weak and your using too much weight and the lower back is having a hard time supporting your torso.... Personally I go really light on low rows and sit dead up right if not leaning forward slightly..... I don't ned much weight this way cuz im just using my lats and upper back, no lower back and little bicep TBH...


Hope this helps