Often your back pain is due to muscle strain
It can occur for a number of reasons. Often it’s due to poor running posture and trying to “push” yourself forward while running. Sometimes it’s due to muscle spasms due to dehydration or a pulled muscle that occurred while running. Also, tight hamstrings can increase the likelihood of muscle strain in the lower back. How can you tell it’s a muscle strain? The pain will be localized pain that doesn’t radiate into the hips, legs or other parts of the body.
Another cause could be sciatica
This happens to a runner when the body shifts during running in such a way that pressure is placed on the sciatic nerve. Pain caused by sciatica can present as leg pain, hip pain and lower back pain. It can be because of incorrect running technique, muscle spasms that put pressure on the sciatic nerve or degeneration of the discs in the spine.
If you strain the muscles in the lower back and have tight hamstrings, it can result in something called Piriformis Syndrome. Piriformis syndrome is an irritation of the piriformis muscle of the buttock. This muscle aids in the rotation of the hips. When the muscle becomes irritated and inflamed it causes pain in the lower back, buttocks and upper thighs.
Foot problems can also be the cause
Improper running techniques can cause jarring in the ankles, knees, hips and even the bones of the spine which can lead to any of the above causes. A common improper technique is running with “flat” feet which means allowing the sole of your foot to impact the ground flatly instead of making initial ground contact with just the heel and allowing the rest of the foot to follow in a rolling motion. Along those lines are footwear issues. When your shoes wear out it causes problems.
If you have back pain after running, seek help, set up a physical therapy consultation, find the cause and get it treated.