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Tuesday, August 30, 2011

Correct Cycling Posture: The Spine

After cycling several thousands of miles with no history of lower back pain to any degree, I hope to clear up any confusion about what posture is optimal for cycling.  This may sound surprising, but a good number of pro cyclists suffer from low back pain despite consulting the most expensive and technologically advanced bike fit technology (3,4).  Why doesn't it work?  What many bike fit specialists fail to account for is the kinesiology of the spine which is influenced by the position of the pelvis.  The saddle can be adjusted in any position, but if the rider has poor posture on the bike, lower back pain is inevitable.  Bike fitters must inform cyclists that rounding the back must be avoided to prevent lower back pain.  After learning why good posture is optimal, you'll understand why no amount of fine tuned adjustments will fix low back pain unless the rider's posture is also corrected.

ROUNDED BACK VS. NEUTRAL SPINE:
I noticed that those who recommend rounding the back do this based on opinion rather than evidence.  A popular cycling blogger, Sheldon Brown, suggested that an "arched back" or flexed spine absorbs shock more efficiently and claimed that additional flexion caused by bumps is "harmless".  Later in his post, he claimed that a straight back cannot absorb shock because it will "jam the vertebrae together."  To kinesiologist, doctors, biomechanists and phd's alike, this is absolutely incorrect and exactly opposite to what is safe and effective for the spine.

Sheldon Brown seemed to believe that the spine was simply a stack of disks connected by support beams which acted exactly like a bridge.  The spine is much more complicated than this.  There are soft intervertebral disks, fascia and musculature of the spine/ core which aid in shock absorption.  Rounding the back places excessive stress on the soft intervertebral discs between the vertebrae and puts the rider at risk for herniation or bulging.  Contrary to popular belief, good posture does not literally mean that the spine is a straight stack of disks- it just appears to look like that.


GOOD POSTURE 101
When you maintain good posture, there are two types of normal curves in the spine, lordosis and kyphosis.  When the spine has a healthy amount of these curves, it is better able to take on the forces of gravity, additional weight, absorb shock from the ground, and allow the musculature around it to produce the largest amount of force possible (2).  Reducing or sharpening any of the curves of the spine compromises its ability to absorb shock.  When you look at the function of every intricate muscle of the spine, you'll find that the actual purpose of these muscles is to prevent the spine from losing these curves (1,2,3,4,5).  In fact, a study has already identified that repetitive flexion or "arching" of the back is a mechanism that may lead to herniation of the intervertebral disks (5).  This means that by following Sheldon Brown's advice on cycling posture, the risk of herniation increases.


Analyzing exercises where a neutral spine is all but necessary:
The squat and the kettlebell swing are two of the most powerful total body exercises essential to a cycling weight lifting program.  If these exercises are performed with an arched back, an eventual injury is guaranteed- the spine must be in neutral!  When the spine is in neutral during both of these exercises, the length of the gluteus maximus is optimized.  This allows the glutes to activate and extend the hips to bring the weight back up.  In an opposite scenario, if the pelvis is tilted back with the spine out of neutral (arched back), the glutes shorten and cannot contribute as much to the movement.  As a result of reduced activation from the glutes, the muscles and joints above and below the pelvis (lumbar spine & knees) will have to compensate by working harder.  Examples of these two exercises can be seen below.
This is an image of Pavel Tsatsouline performing a kettlebell swing with a neutral spine.  Notice how similar this position is to a cyclist on the drops.This is an image of the proper technique for three different types of squats.  All three variations require a neutral spine.

SADDLE ADJUSTMENTS FOR BETTER POSTURE:
The position of the saddle is the easiest variable to change which can make an instant difference (good or bad) on performance, posture, and comfort.  A saddle with its nose tilted down 10-15 degrees will give the pelvis enough room to tilt forward and allow the lumbar spine to move from flexion to slight extension (neutral) (1,2,4).  Sure, the same effect can be done by consciously tilting the pelvis anteriorly on a perfectly level or nose up saddle, but excessive stress will be placed on the arteries forward of the ischial tuberosities (sit bones).  Tilting the nose down also helps because it will be easier to maintain good posture without conscious effort.

While saddle angle is important, seat height can also have an effect on the lumbar spine.  Individuals with poor hamstring flexibility will have a flexed or rounded back if the seat is set too high.  The seat should be set at a height which will not cause the pelvis to tilt posteriorly.  If the seat must be set lower than optimal to prevent damage to the lumbar spine, work on mobility and flexibility exercises for the hamstrings.  As mobility and flexibility improves, continue to raise the saddle little by little.  A saddle height which is too low will place greater compressive forces on the knee (risk of damage to the knee increases) so work hard to improve flexibility and mobility quickly.  Good hamstring flexibility will save both the knees and the lumbar spine from damage.


FAQ: WHY SOME ELITE CYCLISTS CAN'T MAINTAIN GOOD POSTURE
Common reasons for this is due to either poor flexibility, previous injury, incorrect saddle adjustment or a combination of these factors.  Tight hamstrings are usually the problem when it comes to poor posture.  A tight hamstring will cause the pelvis to posteriorly tilt, forcing the disks of the lumbar spine into flexion. The solution to this problem is easy to say, but hard to do- stretch often. For those who fall into the category of spinal injury, it's likely that it will be close to impossible to regain full range of motion (depends on the extent of the injury).


SUMMARY:
The optimal posture for cycling is a neutral "straight" back that allows the spine to remain in neutral.  A neutral spine absorbs shock more efficiently and allows the muscles of the core to activate fully.  In no way has a rounded back been shown to be either safe or optimal for performance.  In fact, a flexed or rounded back may cause intervertebral disk (the pillow between each vertebrae) herniation or bulging.  A study done by a spine biomechanics professor showed that a rounded back is actually a risk factor for lower back pain (5).  Too many cyclists and bike fitters are misinformed and it's a big reason why lower back pain is one of the most common overuse injuries (2).  Bike fitters should learn why tilting the saddle anteriorly (nose down) is necessary to allow the lumbar spine to remain in neutral (3).  For those already suffering from lower back pain, 10-15 degrees was enough to bring the spine back into neutral and reduced the incidence and magnitude of low back pain in 80 cyclists (1,2,4).



RIDERS SETTING A GOOD EXAMPLE:
A cyclist who has excellent cycling posture is Thor Hushovd.  Notice how he is able to maintain a neutral spine in a seated and aero position.  He can safely achieve this position without compromising his lower back thanks to the flexibility of his hamstrings.  It also helps that he shifted past the saddle to give room for his pelvis to anteriorly tilt and keep the spine in neutral.  By including hamstring flexibility exercise into your program, you can mirror his posture once your range of motion reaches 90 degrees hip flexion.



Resources:
  1. de Vey Mestdagh K. Personal perspective: In search of an optimum cycling posture. Applied Ergonomics 1998; 29; 325-334.
  2. Floyd, R. T.. Manual of structural kinesiology. 17th ed. Boston: Mcgraw-Hill Higher Education, 2009. Print.
  3. Mandy, Marsden, MPhil Sports Physiotherapy, and Schwellnus Martin. "Lower back pain in cyclists: A review of epidemiology, pathomechanics and risk factors." International SportMed Journal 11 (2010): 216-225. Print.
  4. Salai M, Brosh T, Blankstein A, et al. Effect of changing the saddle angle on the incidence of low back pain in recreational bycyclists. Br.J.Sports Med 1999;33: 398-400.
  5. Callaghan, J.P., and McGill, S.M. (2001) Intervertebral disc herniation: Studies on a porcine model exposed to highly repetitive flexion/extension motion with compressive force.  Clinical Biomechanics, 16(1): 28-37