regarding stretching, I'd like to complement this by saying that for the hard moves like front and the side splits, people shouldn't think they should be working on flexibility of just one muscle or bodypart (typically Hamstrings).
Failure to do splits is due to all of the machinery being rusty or uncapable, not just the hamstrings. The nearer I get to achieve the split, the more I understand how is ALL of the lower body helping to reach the goal.
Hamstrings are the first to let you know there's years of stretching to be done but if they could, calves, glutes, all of your back would all collectively yell and tell you the same thing as well. Don't spot work for lower body and Back flexibity, treat everything equally.