Experiencing back pain?
Immediately stop any exercises causing it.
You may very well have a bulging vertebral disc or a herniated disc, which is a dislocation of the cartiligenous "cushion" between the bones of your spine.
If they move out of position, they will press against the sciatic nerve, etc...causing a burning type sensation accompanied by a shooting sharp pain shooting down the buttock down the hip along one side of your back and leg...sometimes accompanied with numbness, lower back spasms, a limp, or inability to straighten up your back when walking.
Perhaps you've only "overdone" working out.
Rest the back, and if the pain continues seek medical help.
A bulging disc can recede back into position but will always tend to be trouble.
A herniated disc is much more serious, producing crippling pain, and often requires major surgery.
Simply put...pain out of the ordinary after exertion is your body giving you a warning which you'd best not ignore. Modern techniques can treat disc issues, especially if caught early on. If you suspect a disc issue, have it checked out...they don't improve with age...just the opposite.
A great deal of this current "fitness" craze serves only to pay the mortgages of skilled neurosurgeons.