The best way for me to answer this question is for me to discuss why a large number of the population suffer from bad backs.
Over the years our lives have become more and more sedentary, we drive to work whereupon we sit at our desk having taken the escalator to our office for example! This has resulted in a number of adaptations to our bodies and none of them particularly beneficial to us.
One of these adaptions is that our hip flexors (the muscles that we use to run, located at the very top of our legs) become shorter (or they may be called tighter or over active) either way this shortening of these muscles has a very important and detrimental effect on our bodies. The effect is that they inhibit the opposing muscle of the body from working properly. In this case the opposing muscles to the hip flexors are the glutes (bum). If this muscle isn't working properly another muscle immediately next to it has to do its job or role.
The muscles next to the glutes are the hamstrings and lower back. Thus either one of these group of muscles will be loaded with a force that it is not designed to take. It is therefore easy to see why a large number of people complain of lower back discomfort or in fact perceived hamstring tightness. When all that is happening is that the lower back or hamstrings are taking on the job of the glutes.
It is therefore common sense for an exercise programme to attempt to counter act this by lengthening those muscles that have become short i.e. the hip flexors and then strengthening the underactive ones i.e. the glutes (bum).
If you would like a progressive way of doing this then look out for the new video podcasts that are coming soon. They will give you all the routines needed to not only lose body fat but help fix the problems that every day life has caused us!