SEARCH V.V. Personal Training & Coaching Blog

Friday, January 17, 2014

Kinesiological Approach to Bike Fit: Saddle Tilt

Saddle position is the core of any bike fit.  When the saddle is positioned incorrectly, it can cause a wide range of overuse injuries throughout the entire body.  Pain or numbness can occur at the hands, wrists, elbows, shoulders, neck, back (commonly low back), knees and feet.  This is no exaggeration!  Whenever I perform bike fittings, it's not uncommon for me to fix almost all of the rider's problems solely from correcting saddle position.  This post will discuss saddle tilt.

THE PEVLIS & THE LUMBAR SPINE "LOW BACK"
Since the lumbar spine attaches directly to the pelvis, its fate is determined by the tilt of the pelvis.  When you tilt your pelvis forward, the lower back extends.  When you tilt your pelvis backwards, the lower back will flex.  The right amount of saddle tilt is one that lets the pelvis maintain neutral- the healthy balance of flexion and extension.
Image taken from: http://fixtheneck.com/Other_postural_effects.html
It took some digging around the internet to find the pictures below, but I found three pictures of Nairo Quintana using different amounts of saddle tilt.  Keep in mind that the UCI rule for saddle tilt is plus or minus 2.5 degrees with a tolerance of +/-0.5 degrees, so he's fairly limited with regards to how much he can tilt his saddle.
Nose down = Almost Neutral
If you observe closely, Quintana's saddle was slightly nose down allowing him
to almost reach an almost neutral back.  A few more degrees downward and he would
likely reach neutral!
Level Saddle (0 degrees) = Flexed Back 
With a level saddle, Quintana could not tilt his pelvis forward, so his lumbar AND
thoracic spine had no option but to flex.  Interesting how a few degrees
can cause such a significant change in posture!
Level Saddle (0 degrees) = Neutral Back
Since the climbing position doesn't require a lot of pelvic tilt to reach neutral,
a level saddle was appropriate in this situation.
LEVEL SADDLE... GOOD OR BAD?
There's a lot of bad information circulating and I want to clear it up because I have worked with several clients with problems related to back pain caused by level saddles.  Having a level saddle isn't necessarily bad, but when it is not appropriate for the type of riding to be expected or the rider's condition, that's when problems occur.  A level saddle is not recommended for riders who spend a lot of time in the low racing or time trial position (triathletes and time trialists).  Also, if the frame geometry is aggressive and forces a low position even at the hoods or handlebar tops, then a level saddle is not recommended.

On the other hand, there are situations where a level saddle is appropriate.  If the majority of the time spent cycling is focused on climbing or riding in an upright position, then a level saddle is fine.  A level saddle is also safe for riders with scoliosis or restrictions to avoid extension at the spine.

My custom Fuji SST 3.0. Matching blue
Velocity A23 Pro Build wheelset and
Selle SMP Evolution saddle.
HOW SADDLE DESIGN AFFECTS AVAILABLE PELVIC TILT.
Here is something to consider for those who need an equal amount of climbing and time trial comfort.  A study found that saddles designed with a large cutout allows the pelvis to tilt forward without physically altering the actual saddle angle via the seatpost(2).  So in addition to improving blood flow, saddles with cutouts allow the rider to climb and time trial in a seated position comfortably.  Saddles in the Selle SMP product line are especially versatile at providing both climbing and time trial comfort.  In my personal experience with the Selle SMP Evolution saddle, I have never experienced any discomfort even in 5-7 hour centuries.  It's never a bad idea to invest on comfort, especially near the sensitive areas!


NOSE DOWN:  HOW MUCH IS TOO MUCH?
In order to allieviate or prevent low back pain, most riders can tolerate 10-15 degrees of negative tilt (3).  After 15 degrees, most riders will experience discomfort on the hands or sliding on the saddle.  Grip strength, shoulder stability and core strength will determine how much negative tilt you can handle.


HOW TO PREVENT NOSE DOWN SADDLE TILT PROBLEMS:
Here are common reasons why riders cannot tolerate a nose down position:

  • Saddle movement (sliding down the saddle)
  • Hand pressure
  • Shoulder fatigue

These issues arise mainly because more body weight is transferred towards the front of the bike.  This places a higher physical demand on the upper body and core.  In order to prevent these problems, the following variables need to be addressed.
  • Core strength
  • Grip strength
  • Shoulder stability
  • Posture
Strength exercises done in the gym should be focused on improving one or all of the things listed above.  Exercise with a purpose!

Once these deficiencies are accounted for, you will be able to ride in an aerodynamically low position for hours without discomfort.  Sliding on the saddle no longer becomes an issue because the core and shoulder are able to stabilize and support the body weight.  Hand numbness is eliminated because the intricate muscles of the hand and forearm are able to support the extra body weight.

As a bonus, you will appreciate the extra weight at the front because it will increase grip at the front tire- the tire responsible for steering and cornering.  Since more weight is already placed at the front, you'll also experience smoother and more predictable braking because less weight will need to transfer before deceleration can begin.

HOW TO DETERMINE THE APPROPRIATE AMOUNT OF SADDLE TILT
Saddle tilt is something that needs to be adjusted based on the type of riding to be expected.  Just as you adjust tire pressure to accommodate for riding on pavement (high pressure) or rough roads (lower pressure), saddle tilt should be adjusted based on the terrain of the environment or the workout.  If you're going to be climbing for the majority of the time, then a nose down saddle isn't very important- you can favor a more level saddle.  If you live in the midwest where it's flat and windy, then a nose down saddle is appropriate to make the aerodynamic position more comfortable.

In a sport where aerodynamics are extremely important, there are more benefits in holding a low aero position comfortably versus focusing only on leg exercises, especially since the body accounts for most of the drag.

REFERENCES:
  1. Asplund, Chad, and Patrick St. Pierre. "Knee Pain and Bicycling." The Physician and Sports Medicine 32.4 (2004): 1-11. Print.
  2. Bressel, Eadric, and Brad Larson. "Bicycle Seat Designs and Their Effect on Pelvic Angle, Trunk Angle, and Comfort." Official Journal of the American College of Sports Medicine 3 (2002): 327-332. Print.
  3. Schultz, Samantha, and Susan Gordon. "Recreational cyclists: The relationship between low back pain and training characteristics."International Journal of Exercise Science3.3 (2010): 79-85. Print.