Hello, Welcome to Just Answer and thanks for your question. The problem can be constipation, obstruction, polyp, hemorrhoid, etc. You will need to have an examination and perhaps a colonoscopy to determine what the problem is. Fiber in the form of fresh fruits and vegetables and whole grains can help keep stool soft and easy to pass. If that isn't sufficient, supplements like Metamucil and Citracel can help.
If this happens only occasionally, then an increase in fiber and fluids along with 30-60 minutes of brisk exercise daily should eliminate the problem. One should not have to "try hard" to have a bowel movement. That indicates a problem.
What is too brief? Without an examination and a colonoscopy there is no way to tell you what is causing the problem. Whether that is said in 50 words or 5,000 is immaterial.