Back pain affects 60-85 percent of people worldwide, at one time or another, and half the population has their first lower back episode before age 20. It is the most common and expensive neuromuscular disorder. For most, the pain subsides in a few days, but for others, the right exercise program can restore and enhance back health. One of the biggest causative factors of lower back pain is the type and amount of mechanical loading placed upon the spine, such as bending, twisting and prolonged sitting. The good news is that you’ll have success if you incorporate exercises that develop power around the hips and gluteals. Many accomplished athletes and world-class strongmen with back pain credit a component of their success to kettlebells, a popular new trend in training. Yet others find that it irritates their backs. The kettlebell swing is a terrific dynamic total-body integration movement, but is it good for everyone? Kettlebells are bowling ball-size cast iron weights with a single looped handle on top. Unlike using regular weights, unique loading patterns are created throughout the body. The kettlebell swing is an example, in that the back, gluteal and external oblique muscles are turned on. To perform the swing, the kettlebell is held in your right hand. From a squat position with a neutral spine, the swing is initiated by simultaneously extending through your hips, knees and ankles, performed by swinging it to chest level and returning it. The move, says Stuart McGill, Ph.D., a professor of spine biomechanics and chair of the department of kinesiology at the University of Waterloo, is a “wonderful posterior chain balancer.” Pavel Tsatsouline, a former Soviet Special Forces trainer, started the kettelbell craze in the West in the 1990s. He and six other fit young men were part of Stuart Mcgill and Leigh Marshall’s research published in the Journal of Strength and Conditioning Research last month. McGill was curious about why the lower back loading of this exercise (the study included three others that I don’t have room for in this column) is therapeutic for so many accomplished athletes, yet troublesome for others. The swing itself needs sufficient spine stability to withstand the compression forces across the lumbar joints needed to accelerate the bell through the arc-like trajectory. The findings showed that compared to traditional squats or dead lifts, the ratio of compression to shear is quite different. Unstable spinal joints may experience micro-movements from these forces, causing discomfort. Most people with painful back conditions tend to use their backs more by moving the spine instead of the hips when it is under load. The spine may be better able to withstand high loads if it is postured close to its natural curves, and stiffened with abdominal wall contraction, McGill notes. He suggests using good form by bending at the hips in the squat part of the move (and any other type of squat), rather than spine motion. If it is appropriate for you, enjoy including kettle bells into your workouts.     Connie Aronson is a fitness specialist based in Ketchum.