lots of hamstring stretching , tight hamstrings are very bad lower back, plenty of core = stomach exercies, and this one lie flat on your back , bring left leg under right leg , then push left leg against the right, whilst bring both legs up , its called a x over , it will stretch right into buttock area , feck me it hit's right in to where i get lot of jib bang into both sides of my lower back . try these above, (But ) take it easy when you start , build up slowly