True or False? Your Back Pain Will Vanish Forever if You Train Your "Core"! Plus: What Actually is the F*** "Core"?

Currently, no standardized system has been established analyzing and comparing the results of core strength training and typical resistance training. Therefore, Wen-Dien Chang, Hung-Yu Lin, and Ping-Tung Lai conducted a systematic review of the results of previous studies to explore the effectiveness of various core strength training strategies for patients with chronic low back pain.

In general, their results appear to confirm the hypothesis that appropriate "core training" will "assist in the alleviation of chronic low back pain" (Chang. 2015). The efficacy of different training modalities and training different muscle groups does yet have significantly different effects on chronic low back pain.

Before we delve any deeper into the specific exercise modalities I do however want to do something many people forget, when they are talking about strengthening the "core muscles". This "something" that is so often forgotten is to define the muscle groups that constitute the core,... or rather the muscles that are capable of stabilizing our (lower) backs in a way that renders them "pain proof". As Chang et al. point out, the core muscles, which are the primary muscle group for maintaining spinal stability, can be divided into two groups according to their functions and attributes (from Chang. 2015):

• The first group of muscles is composed of the deep core muscles, which are also called local stabilizing muscles. These muscles primarily include the transversus abdominis, lumbar multifidus, internal oblique muscle and quadratus lumborum. The lumbar multifidus is directly connected to each lumbar vertebral segment, and the transversus abdominis and lumbar multifidus activate a co-contraction mechanism. The abdominal draw-in that occurs during contraction provides spine segmental stability and maintains the spine within the neutral zone. In additional, these muscles provide precise motor control and are thus primarily responsible for spinal stability.
• The second group of muscles comprises the shallow core muscles, which are also known as global stabilizing muscles, including the rectus abdominis, internal and external oblique muscles, erector spinae, quadratus lumborum, and hip muscle groups. These muscles are not directly attached to the spine, but connect the pelvis to the thoracic ribs or leg joints, thereby enabling additional spinal control. These muscles produce high torque to counterbal ance external forces impacting the spine; thus, this group of muscles is secondarily responsible for maintaining spinal stability. 

The function of this muscle can be best described as a "natural brace" that maintains segmental stability, protects the spine, and reduces stress impacting the lumbar vertebrae and intervertebral discs. If the muscles are weak or their power is unbalanced, this can trigger chronic back pain. Depending on which of the two is the reason for your back pain (imbalance or weakness), the goal must thus be to strengthen all or specific core muscles.

Figure 1: Overview of the four exercise types used in the studies reviewed by Chang et al. (2015).

In their study, Chang et al. compared the results of four out of 142 reviewed studies which study the effect of four core strength training exercises (i.e., trunk balance, stabilization, segmental stabilization, and motor control) on deep core muscles strength, stability and back pain (see Figure 1). One reason the studies by Akbari et al. (2008), Andrusaitis (2011), França (2010) and Gatti (2011) were selected was their design.

Table 1: Intervention, assessment and results of reviewed articles (Chang. 2015) | VAS: visual analogue scale; OSWDQ: Oswestry disability questionnaire; RMQ: range minimum query; PBU: stabilizer pressure bio feedback unit; BPS: back performance scale | *p < 0.05, statistically significant difference between experimental group and control group.

To make sure that any potential benefits of the exercise protocols were in fact core-training specific, all of the control groups in the four reference studies performed typical resistance training to strengthen their trunk and lower limb muscles (e.g., curl-ups, straight-leg raises, and pushups) and this is exactly where things become dodgy, because in only one of the studies the pain reduction was significant, compared to the control group.
References:

• Akbari, Asghar, Samane Khorashadizadeh, and Gholam Abdi. "The effect of motor control exercise versus general exercise on lumbar local stabilizing muscles thickness: randomized controlled trial of patients with chronic low back pain." Journal of Back and Musculoskeletal Rehabilitation 21.2 (2008): 105-112.
• Andrusaitis, Silvia Ferreira, et al. "Trunk stabilization among women with chronic lower back pain: a randomized, controlled, and blinded pilot study." Clinics 66.9 (2011): 1645-1650.
• Chang, Wen-Dien, Hung-Yu Lin, and Ping-Tung Lai. "Core strength training for patients with chronic low back pain." Journal of Physical Therapy Science 27.3 (2015): 619-622.
• França, Fábio Renovato, et al. "Segmental stabilization and muscular strengthening in chronic low back pain: a comparative study." Clinics 65.10 (2010): 1013-1017.
• Rozenberg, S. "[Chronic low back pain: definition and treatment]." La Revue du praticien 58.3 (2008): 265-272.