1.  Kettlebell exercises strengthen the glutes (muscles in your backside). 

The late Vladimir Janda, M.D., from the Czech Republic observed that people with low back dysfunction often exhibit "gluteal amnesia." And if not overcome with proper recruitment pattern practice, it is likely to lead to more back problems as the back has to take over the lifting task of the powerful glute muscles.   Unlike most other exercise programs, the glutes are STRONGLY emphasized in kettlebell training.

Another way of putting it...you help your back by developing real "buns of steel."

2.  Kettlebell exercises stretch the hip flexors.

In Janda's research, weak glutes were associated with tight hip flexors.  The RKC system of kettlebell training has no equal in promoting hip flexibility.

3.  Kettlebells develop back endurance.

Professor Stuart McGill, the #1 spine biomechanist in the world, concluded that while lower back strength surprisingly does not appear to reduce the odds of back problems, muscular endurance does.  Enter the high repetition swing and snatch.

4.  "Bracing" is superior to "hollowing" for spinal stability.

Misinterpreted research has lead to the popular recommendation to "pull your navel in toward your spine."  "Bracing", as defined by Dr. McGill as symmetric stiffening of all the muscles surrounding the spine without hollowing or pushing out the abdominal wall, is a superior technique (see McGill's book Ultimate Back Fitness and Performance).  The RKC system of kettlebell training teaches many innovative techniques to improve your spine bracing skill.

5.  Sensible ballistic loading appears to reduce the odds of arthritis.

Repetitive ballistic loading of kettlebells swings and other quick lifts appears to be highly beneficial to your joints--provided you do not overdo it.  Doctor Verkhoshansky and Dr. Siff state in the book Supertraining (available from www.elitefts.com):  "...joints subjected to heavy impact are relatively free of osteoarthritis in old old age and those subjected to much lower loading experience a greater incidence of osteoarthritis and cartilage fibrillation...as one progresses up the lower extremity, from the ankel, to the knee, the hip and finally to the lumbar spine, so the extent of fibrillation increases at any given age.  It appears the the cartialge of joints subjected to regular impulsive loading with relatively high contact stresses is mechanically much stiffer and better adapted to withstand the exceptional loading of running ajumping than the softer cartilage associated with low loading.  Thus joint cartilage subjected to regular repetitie loading remains healthy and copes very well with impulsive loads, whereas cartilage that is heavily loaded infrequently softens...the collagen network loses its cohesion and the cartilage deteriorates."

6.  Unique kettlebell exercises are great for strengthening the multifidus.

Weakness in this small intrinsic spine muscle has been linked to back problems.  Physical therapists Steve McNamara, RKC has concluded that kettlebell exercises, especially juggling, safely recruit and strengthen the MF.

7.  "Injury prevention by imperfection training."

The late Dr. Mel Siff pointed out that the traditional injury prevention strategy of avoiding "dangerous" exercises and excessive loads is inadequate.  The scientist advocated "injury prevention by imprefection training".

Taking carefully measured doses of "poisonous" exercises to build up one's tolerance is standard Russian practice.  An example is the Russian hockey deadlift.  It combines spine torsion and forward flexion, traditionally a non-no combination.

"Injury prevention by imperfection training" is an advanced practice, generally frowned upon by medical professionals.  Clear it with your doc and practice it at your own risk.