Here is a slideshow on back problems and pain.
I've had my own share of back problems and can tell you that once it's there you'll usually always have it around lurking in the background waiting for a chance to take you down.
First it helps to know what the problem is. This slide show gives you some idea of the various problems that can crop up. The most important one for tennis players is to know the difference between muscle and disc injuries. Usually with muscle injuries your back stiffens up as a form of protection. The weakened back is then more vulnerable to disc injuries and those are your nightmare. Usually disc injuries show up in leg and arm pains that radiate. Lifting too much weight is often the a cause of back injuries or lifting incorrectly.
Here is a WebMD informational on proper lifting.
I learned from experience that keeping my hamstrings well stretched cut down on my injury risk and the pain of recovery once I did get a back injury. There are ways of stretching correctly and ways to do it incorrectly.
Here are a few links for proper stretching methods.
http://www.sportsinjuryclinic.net/sport-injuries/thigh-pain/tight-hamstring-muscles/stretching-tight-hamstrings
http://www.popsugar.com/fitness/5-Easy-Hamstring-Stretches-1983373#photo-1983373
https://breakingmuscle.com/learn/stretching-your-hamstrings-isnt-always-best
http://www.menshealth.com/fitness/tight-hamstrings-0
I'm not a doctor or physical therapist so only use this for informational purposes and consult a physician if you experience any symptoms discussed or shown above.
