The commonly held beliefs that a strong low back and strong abdominals are protective of back pain are not entirely true. Several studies have shown that muscular strength does not predict who will suffer from future back pain (Biering-Sorenson, 1984). You see, most people have the requisite muscular strength needed to maintain a neutral lumbar spine during daily activities. However, repetitive tasks seem to tire our musculature, resulting in faulty movement patterns over time. Poor movement patterns put undue strain on tissues in the back that inevitably lead to pain. These findings suggest that it is not insufficient strength, but insufficient muscular endurance that leads to injurious movement patterns associated with low back pain(Cholewicki, 1996). This dispells the myth that strong back or abdominal muscles are prophylactic of the back. Rather it has been shown that core muscular endurance reduces the risk of future back problems (Louto, 1995).
So possessing core strength doesn't appear to protect the spine from CLBP (chronic low back pain)? Does training for core strength? It appears not. One study found that traditional physical therapy treatment modalities coupled with lumbar strengthening exercises were less effective than training for dynamic muscular stabilization techniques. Let's define strength as to not get one confused. Strength refers to maximal muscular contractions, as in moving the heaviest load possible or resisting being moved by large forces. Generally strength is measured in short amounts of time or repetitions (less than 5). Strength is not to be confused with muscular endurance, which is measured by performing many repetitions or by performing over a duration of time.
Another study in which all 3 groups increased trunk strength concluded that,
"No differences in the clinical outcome were observed between the three therapy groups, and the changes in physical performance after therapy did not correlate with the clinical outcome. It is therefore questionable whether strength measurements have any clinical significance in documenting the success of rehabilitation programmes."
So possessing strength or improving ones strength in the core musculature doesn't appear to help reduce CLBP. improving trunk/core balance, muscular endurance and dynamic muscular stabilization do appear to help. Again, this harks back to the fact that repetitive tasks seem to tire our musculature, resulting in faulty movement patterns that over time lead to injury and pain.
So how should I go about gaining endurance in the core musculature? You want to do this in the manner in which the body is meant to move. This means avoiding machines. Anything that trains you in an upright seated posture most likely is not going to benefit your spine. Secondly, sitting in a loaded position or sitting and repeating flexion/extension or rotation only further damage the spine via increased compression in an already precarious position. DON'T DO IT.
Dynamic muscular stabilization techniques (DMST) may be more effective than traditional physical therapy. DMST basically means training yourself to be able to stabilize the spine throughout a variety of 'dynamic' movement patterns. DMST is training muscular endurance in a functional manner. This type of training requires proper movement patterns be taught so that one may maintain optimal spinal positioning during activities of daily living and progressing to more challenging rarely used postures. Including gardening from the knees, picking items off the floor, rising from chairs etc. Teaching proper movement patterns may alleviate CLBP. If the painful stimulus is lessened or eliminated shouldn't the pain go away with it?
As for gaining muscular endurance in objective measures, you may guess that I am not going to recommend performing 2000 sit-ups per day like Manny Pacquiao claims to perform in his commercial. This is lumbar spine suicide for 99% of humans. Instead, revisit the big three exercises popularized by the leading spinal researcher in the english speaking world, Stuart McGill. As you progress with these movements, try subbing the modified curl-up for front plank progressions. Practice the front and side planks until you can easily hold them with great form for greater than 60 seconds. Next, progress by adding weight, using one/arm for support or rotating the body in a plank fashion into front/side planks, and returning to the initial position. Build your capacity via many sets of shorter holds. For example 8 sets of 6 second holds instead of going all out on 2 sets of 20 second holds. This will limit chance of injury and allow re-oxygenation and recovery of the stressed tissues.
McGill and colleagues (2003) demonstrated that the relationship between the extensor musculature of the back is diminished relative to the flexor and lateral musculature in those with lingering back troubles. Specifically we are talking about the thoracolumbar musculature; erector spinae, the longissimus, iliocostalis and multifidus muscles .The best lifters in the world (Olympic Weightlifters) show hypertrophy in these muscles that act to support the spine from buckling forward when lifting a load. Any time we bend over or flex forward, these muscles act to create posterior shear to counter the anterior shear forces that we may experience from picking a heavy box from the floor.
So how do you know if your extensors are weak relative your flexors/lateral musculature. Check out the table below.
RSB= right side bridge, LSB= left side bridge, the times are listed in seconds.
The above results are from pain free subjects mean age 21 years. As you can see, women had higher times in extension vs. men and lower times in the lateral musculature as measured via side bridges.
Next, we look at older men; mean age 34. Endurance times are down across the board as compared to the younger counterparts from 11.2. Specifically note the ratio between flexors and extensors in the non-back troubled controls vs. those with a history of back troubles. Those with a history of back troubles have much more flexion endurance (84 vs 66 seconds) as well as more lateral muscular endurance. They also have lessened extensor endurance 90 vs 103 seconds).
Extensor Test for thoracolumbar musculature and glutes
Flexion Test for hip flexors and abdominals
Side-Bridge Test for lateral musculature (Obliques)
So those with lingering back issues have poor endurance in the lower back extensor musculature as well as the glutes in comparison to the obliques and the abdominals. They also had increased endurance in the obliques and abdominal/hip flexor musculature compared to the pain free controls. This suggests that compensatory movement patterns that neglect lumbar extension and rely more on the anterior musculature of the core are not protective of the back. If you fall into this category, focus on holding bird-dogs then progressing to more demanding moves such as supine planks from the hands, supine planks, supine bridges / glute bridges, hip-thrusts and graduating with glute-ham raises. Again, be smart and build endurance through many bouts of shorter holds or lower reps with numerous sets as you work towards longer holds or more repetitions.
With all of the above movements, focus on limiting motion at the lumbar spine by bracing your ribs to your hips via the abdominal musculature. We want the movement to come from the hips via strong gluteal contractions that extend the hips. SQUEEZE YOUR CHEEKS HARD! When at the top of the movements, picture a quarter between your cheeks and squeeze as hard as possible as to not let it go. Strong glutes may be protective of the back, while muscular endurance of the lumbar extensors (this includes the glutes) certainly appear to be protective.
What are you waiting for assess! Correct! Get started progressing with your exercises! And of course don't start without discussing this with your Dr. Yada yada. Don't sue me! I'm only trying to help.
Biering-Sorenson, F.,(1984) Physical measurements as risk-indicators for low-back trouble over a one-year period. Spine, 9: 106-119.
Louto, S., Heliovaara, M., Hurri, H., et al. (1995) Static back endurance and the risk of low back pain. Clinical Biomechanics, 10: 323-324.
McGill, S.M., Childs A., and Liebenson, C., (1999) Endurance times for stabilization exercises: Clinical targets for testing and training from a normal database. Archives of Physical Medicine and Rehabilitation, 80: 941-944