When working with kettle bells it is extremely important you have an experienced trainer/ instructor who can show you the proper technique of the numerous swings and movement patterns which can be executed with this amazing piece of equipment. The swings should come from the hips and not the lower back. I see a lot of people make the mistake of swinging from their lower back. I find that most of the population with a postural dysfunction stemming from the pelvis will forget how to activate the muscles that cross the hip and instead activate the already tight lower back.
Multiple positive effects are created from this modality: strength building, muscular endurance training, lean muscle building, hand/ eye co-ordination and improved proprioception and balance are key areas where improvements take place. The cardiovascular conditioning and full body workout out and fat burn in a short period of time outpaces everything else.
I found an article that sums up the reason why Kettle Bells can even be used by the population of people with aches and pains stemming from the lower back. Again, check with your chiropractor or physiotherapist if this modality will help your situation by strengthening the correct muscles of the posterior chain of the body.