|The Impact of Strength Training on the Back
Len Kravitz, Ph.D. and Tony Kemerly, M.S.
Previous research has established that 60% to 80% of adults in the U.S. have low back pain (LBP) sometime in their adult lives, with up to 50% having back pain in any particular year (Lahad, Malter, Berg, & Deyo, 1994). A current review by Carpenter and Nelson (1999) adds that LBP is the major physical limitation to people under 45 years of age, trailing cardiovascular problems as the second most common chronic disorder.
Ironically, with all the muscular fitness research indicating the strength and endurance benefits of a periodized, progressive resistance training approach, the role of exercise in the treatment of LBP remains unclear and problematic. Perplexing this issue is the knowledge that 33% of patients with LBP will be pain free within a week of the episode, regardless of any intervention.
A common theme seen in a number of LBP treatment approaches is a lack of research supporting the intervention as well as a passive approach of the therapy (i.e. electrical stimulation, massage, traction, manipulation, heat, cold, etc.). Carpender and Nelson (1999) proclaim that the underlying similarity in these passive treatments is the failure to induce a desirable physiological adaptation.
Exercise vs. Meaningful Movement
The evidence clearly shows that those with higher levels of cardiovascular fitness, muscular strength, and muscular endurance have fewer spinal problems. In addition, healthy, normal individuals have superior trunk strength than their LBP counterparts. McGill (1998) suggests that more emphasis should be placed in developing muscular endurance. However, LBP patients often shun physical activity due to its association with increased pain. This lessened physical activity leads to muscular weakness, loss of range of motion, and may also contribute to an increase in the susceptibility to injury. This common activity avoidance malady is referred to as the "Deconditioning Syndrome."
Presently, the prevailing sentiment in the literature is to incorporate active exercise treatment protocols for LBP sufferers. Much controversy exists into which exercise programs produce the most praiseworthy outcomes. Further discussion suggests that a clear distinction needs to be made between exercise and meaningful exercise for the treatment of LBP. Many traditional calisthenics-type approaches to low back conditioning fail due their inability to stabilize and isolate the pelvis.
A Need for Pelvic Stabilization with Lumbar Extension
Carpenter and Nelson (1999) concur with the view of others that pelvic stabilization is a major key to the measurement and treatment of lumbar extension strength. Even though equipment technology has made significant leaps in quality and effectiveness within the last decade, there are few low back exercise devices that appropriately challenge the lumbar extensors while keeping the pelvis fixated. Yet the research shows that the lumbar extensors have a rather large capacity to improve in strength, when adequately challenged this way. It has been shown that in addition to the potential for strength gains, lumbar bone mineral density and erector spinae cross-sectional area will increase with isolated lumbar extension exercises. Surprisingly, randomized/controlled research comparing once per week, twice per week, and three times per week of isolated dynamic lumbar extension exercise (with pelvic stabilization) over a 12-week period did not show any frequency to be superior in the magnitude of strength gain. It has been hypothesized that the lumbar extensors are unique with regard to the need of only one workout per week.
The Exercise Prescription for Low Back Health
An exercise prescription may have a two-fold approach of challenging damaged tissue, as in LBP rehabilitation, as well as progressively overloading healthy supporting tissue in an effort to encourage tissue growth. Ideally, meaningful exercises will be selected that impose minimal load to the joint while sufficiently challenging the muscle. The realm of LBP prevention has been inundated with a variety of modalities and recommended interventions. Yet, scientific evidence has recognized one chief component of the low back health exercise prescription to be isolated lumbar extension, with pelvis stabilization. This can be achieved with a training program consisting of a minimum of one set of 8-15 repetitions done to muscular fatigue, one time a week.
McGill (1998) recommends that exercises involving spinal loading need to be performed in a "neutral" spine position. He cautions those who recommend posterior pelvic tilts during spinal loading, which may cause preloading of the annulus (of the intervetebral disc) and the posterior ligaments. He also recommends performing unloaded spinal flexibility training as is done with the well-known "cat stretch." The emphasis of the flexibility training should be in establishing mobility, with less focus on achieving end range of motion improvements in the spine. McGill advocates a variety of abdominal exercises since no single spinal flexion motion fully and effectively engages all of the abdominals. He also recommends exercises similar to a side lying support (hips off floor with body weight supported by a bent elbow with side of body toward floor) to strengthen the quadratus lumborum, which plays a sizable role in spinal stabilization.
Aerobic exercise should also be included in a low back health exercise prescription. Epidemiological research suggests that runners have less disk degeneration than their physically active weight lifter and soccer player peers. Even walking may have some beneficial effect to low back health due to the prolonged activation of the torso musculature during a sustained period of walking.
As with all exercise prescriptions, designing an exercise prescription tailored to each individuals goals and fitness level is essential. At present, more clinical biomechanical and electromyographical studies are needed to verify the type of exercises, number of exercises, and proper progressive overload that should be included in a comprehensive LBP exercise program.
Carpenter, D. M. and Nelson, B.W. (1999). Low back strengthening for the prevention and treatment of low back pain. Medicine & Science in Sports & Exercise, 31, 18-24.
McGill, S. M. (1998). Low back exercises: Evidence for improving exercise regimens. Physical Therapy, 7, 754-765.
Lahad, A., Malter, A. D., Berg, A. O., & Deyo, R. A. (1994). The effectiveness of four interventions for the prevention of low back pain. Journal of the American Medical Association, 272, 1286-1291.