The American Pain Society and the American College of Physicians (Chou & Huffman 2007) endorse exercise as a treatment intervention for chronic lower-back pain (LBP). Many in the fitness community, the medical profession and the general public believe that core training (including core strength and/or core stability) is the solution for LBP.
Wang et al. (2012) performed a meta-analysis (a statistical technique for combining results from independent studies) on the effectiveness of core stability exercise versus general exercise. They looked at five studies that included 414 patients and compared core stability to general exercise for LBP. The subjects all had chronic LBP ( > 3 months).
The results of the analysis showed that core stability exercise was better than general exercise for short-term pain relief. However, in long-term follow-ups at 6 and 12 months, there was no difference between core stability exercise and general exercise. The analysis also showed that in the short term, functional status improved with core stability exercises.
The authors acknowledged some limitations associated with this meta-analysis, noting that the results were based on relatively low-quality data with a high risk of bias. For example, neither the subjects nor the clinicians were blinded to the interventions or the outcomes. The total number of subjects (414) was too small to enable researchers to identify differences between the two exercise interventions. And the types of core stability exercises were not specified, nor were examples provided.
In a study by Falla et al. (2014) the authors looked not at an exercise intervention but rather at relevant muscular responses to the exercise environment. The study examined the lumbar erector activity of patients with chronic LBP versus healthy controls. Multiple prior studies had shown that people with chronic LBP displayed biomechanical disturbances in trunk, spinal and lumbopelvic motion.
Using electromyography (EMG), Falla and colleagues observed muscle activity during a repetitive lifting task of 25 cycles in 200 seconds. The load lifted was consistent for all subjects, and researchers controlled the rate of movement with a metronome. They measured pain thresholds while lifting and 3 minutes after the test and then compared those numbers with baseline pain levels for the LBP subjects.
Results showed that healthy controls used a more variable movement strategy and changed the distribution of lumbar erector activity during the repetitive lifting task. This muscle activation variability in different regions of the erector spinae in healthy subjects may be a preferential movement strategy for maintaining motor output and avoiding overload on one region. Conversely, the LBP group performed the task with the same group of lumbar erectors throughout the task. This lack of variability and muscle activity coincided with reduced lumbar movement and higher levels of LBP. The LBP group also showed a reduction in mean EMG frequency. Over time, a reduction in EMG frequency can occur due to an accumulation of metabolic byproducts, which may then lead to increased nociception stimulation and fatigue.
When selecting exercises for clients who have chronic pain, be specific and consider the entire bio-psycho-social perspective. Some clients—particularly those who report back instability—may respond well to core stability exercises. But others may already be overusing a bracing/stability strategy that is counterproductive to long-term function and movement confidence. For a client in this group, isometric core stabilization exercises such as planks may reinforce the lack of variable motion in the lower-back region and perpetuate the limited-movement strategy that has been shown to increase their pain. For this client, consider beginning with more remedial corrective exercises in postures or positions that do not immediately encourage bracing; for example, exercises that are done prone, supine, in quadruped position, kneeling or half-kneeling. Help the client focus on external cues to remove his attention from his internal focus on stabilizing.
Movement variability is key to healthy motion and dissipates mechanical stress to soft tissue and joint structures, thereby avoiding localized fatigue and developing alternative movement strategies.
To read more about how physical activity can reduce the risk of nearly three dozen harmful conditions and life-threatening diseases, please see "The Many Dimensions of Pain" in the online IDEA Library or in the February 2016 print issue of IDEA Fitness Journal. If you cannot access the full article and would like to, please contact the IDEA Inspired Service Team at (800) 999-4332, ext. 7.