ORIGINAL: Adil Some pumps are usually assosiated with testosterone. tbol inhibits SHBG - therefore increasing free testosterone There must be some other reasons to, but I do not know what they are
What exactly is back pumps? Tricky one this. I personally believe that it's not quite just as simple as certain-steroids causing an increase in bloodflow to /retention in the spinal erectors. Yes that happens certainly, but there may well be other factors at play, like misalignment of your SI joints, caused by the hypertonic erector muscles. Also, there is the core support issue to consider. Personally, when I take those steroids that do cause the back pump, I also seem to get inhibition of my obliques and TVA, causing my guts to bulge out. This reduces the amount of abdominal recruitment and support, placing more load on my erector muscles, compounding the problem of the back pump. Yet another thing to consider is that if the erector muscles are hypertonic, then they don't get as much chance to recover full between workouts, so they become more fatigued over time, leading to weakness and injury/swelling, which further impedes performance in the gym.
IMHO the symptoms are due to pumps of the psoas major muscle which is a large muscle that runs to the lesser trochanter of the femur from the lumbar vertebrae, and runs proximally medial to the kidneys. this is a large muscle that flexes the thigh - if your lumbars are out of alignment the pumps could more painful and frequent