Things can be harmful to a rider without hitting the deck (e.g. bad saddle location). Other things like a too stiff, too soft frame and much more. Other things like nerves and their branches and the amount of tension in areas like the sacral plexus, not seen from video, or tracking by using dots.
Cycling really is a sport of balance and cognitive function, an exercise of sound judgment. How you balance the weight makes a huge difference. Shorty stems, wrong size bikes don't make sense and can have you in pain. Where does the sound judgement of bike fitting come? First is the choice of bike. What do you want to do? Or is it just get close, make the ordeal as fast and easy as you can. Don't expect tall head tubes, tall hands to improve you balance no matter what they tell you. For most shops "I don't want the shop turning into a training center, and I don't want to hear that bike I have already paid for is the wrong size, move it off the floor. We don't teach."
"There is always differences between the two sides of a thigh - such as a difference of 1.25 cm in total length of the limb - may be normal."
That is why WN measures the bones, and the CAD takes the average for compression, shearing, and tension!
One of the biggest pain in the butt in cycling is, not knowing where to put the saddle in space. That depends on what you want to do (e.g. tt, tri, road, mtb, track, etc...). It's important to note, sitting atop a saddle while on a trainer in a passive manner is not the same as the exercise out in the real world. Even the lateral stiffness of a bike is changed in a trainer verses outside. A saddle that seems hard in flex on a trainer is not as hard outside. A saddle that is too soft in a trainer is going to be way too soft in the real world, causing a less stable hip.
Where the human meets the saddle is many times the source of soreness and pain given the actual pedaling actions. Just like ski boots, too much, too little and you can have an "OUCH" and it depends on the user and how hard they want to go. Even with the so called high-tech fitting processes many point out that they have pains not only in their butts, but also other areas, above and below the hip. Like a tooth, wait until they wear out due to having the wrong placement of saddle. After all you can get new knees made these days! The spine is another story!
The saddle supports the connection of upper and lower body. Management comes from knowing how to adjust the saddle with the Sacrum. Learning how to address the saddle. Not so easy, as you have a human spine above the hip, with maximum pressure at the spines base on top of the sacrum, that has a (Lumbosacral angle), at the junction of, and is formed by, the long axes of the lumbar region of the vertebral column and the angle of the sacrum, the bone in the middle of the hip. The vertebral column is flexible because it consists of many relatively small bones that descend to the sacrum. The structural differences here are huge and you can have disabling pain (e.g. back pain occurs frequently in competitive sports). It plays a very important role in posture and locomotion - movement. It is partly rigid and flexible, forming an axis for motion.
"The anatomy of the back is very complex, and back pain has many causes"
Inadequate spinal motions can cause the spinal segments to stiffen, normal with age, the discs tend to dry out. It's no fun to have stiff links, links that are too rigid, just like not having the bike chain clean and lubed. Stiff links equal dysfunction through the entire human link chain. The shape and strength of the vertebrae and discs, ligaments, and muscles provide stability to the vertebral column. Variations in vertebrae are affected by race, sex, and development factors (genetic & environmental). Only with medical images such as radiographs and computed topographies (CT's) and during dissections and autopsies of persons can it be reviewed. Abnormal curvatures of the spine affect the anatomical positions and how that person can and can't perform work.
The anterior rotation of the pelvis (upper sacrum tilts anteroinferiorly) at the hip joints, it has motion, so tracking from the outside of the lateral hip, on top of shorts, skin, muscle layers is at best guessing. The pull of gravity often causes a temporary lordosis (e.g. increased weight or obesity of the abdominal contents (potbelly) or like the late deformity of pregnancy. Weaken trunk musculature, especially the anterolateral abdominal muscles.
Ok, back to the saddle being in the wrong place, a real pain in the butt from a dysfunctional system (e.g. poor bike fit). It then becomes a game of tolerance with time. Let's start with a given hip angle and add the compression of muscles due to the anterior rotation of the pelvis on nerves (e.g. piriformis), it can become a major issue for sports that require excessive use of the gluteal muscles. So what position is it? Is there a position v. motion?
Start with women who are more likely to develop the sciatic syndrome, hypertrophy may be the cause. In about 12% of people the sciatic nerve passes through the piriformis. It can pass over, through or under or in any combination.
Think about what that means in finding the correct lordosis with a saddle. Way too often, the saddle is placed too far forward, level or for what ever reason a fitter comes up with, because of ease of using the plumb-line to knee, this lowers the saddle, it puts the lumbosacral angle in the wrong zone, much more compression is placed on the distal spine, plus more press on the rearward ischial ramus, there is a bursa and it can have microtrauma, resulting in bursitis (e.g. inflammation) or even calcification in the bursa that is chronic. It causes you to also deepen the knee flexion at the top of the pedal stroke, an area of concern.
Plumb-line is easy, fast, low-tech, very general, plus cause compression of the piriformis, micro trauma, hypertrophy of certain muscles, IT band issues, chronic bursitis, even calcification, along with sciatic. Yet it is used as the reference point for most of the bike fits people pay for. Another method is to place angle device on the lateral aspect and eyeball it, again "no cigar".
Sciatica can be caused by a herniated disc or bone deposited, that narrows the foramina, but also for other reasons. Any maneuver that stretches the sciatic nerve, poor skills (e.g. heel down pedal style), flexing the thigh wrongly with leg extended, having the saddle in the wrong location, wrong saddle choice, etc...
People should realize when you move the saddle too much forward they place more compression, more stretch to area around the hip, more pressures on things that can take you out of the game (e.g. a real pain in the butt), things that can produce or exacerbate pain. On the other side, having the saddle too much the other direction is not much better.
There are many parts of a hip, ilium, sacrum, anterior and posterior aspects, ramus of ischium, ischial tuberosity, inferior rams of pubis and a bony pubis, nerves and bursa sacs. They all need to be able to move in & out of balance upon a saddle. There are even deeper groups of muscles of concern (piriformis, obturator interns, externus gemelli, and quadrates femurs), all covered by the inferior half of the gluteus maximus, and the lateral rotators of the thigh. All these move a lot and work together to help stabilize the hip joint by steadying the femoral head in the acetabulum. So tracking superficial muscles makes it next to impossible to wants going on deeper where compression, shearing, and tension occur.
"You don't want to sit on your gluteus maximus"
Then you have to concern everything above it in space, the best shoulder blades, spine motions, etc... Then you have different angles of inclination of the long axis of the femoral neck that varies with age, sex, and the development of the femur.
Just like the ski industry, for years retail shops just sold ski boots that had sizzle, but few really knew what the foot really needed. They didn't care to track the movement of the bones ( 7 tarsal, 5 metatarsal & 14 phalanges) of the feet that lie inside of a given shoe? That was too hard, and besides they would never know the difference. So that's the question, who cares?
How long is it going to take to get people to care? It would seem a lot don't care, as they just park their bikes and allow it to collect dust due to the thing being a pain!
Any wonder we can't get more people on bikes, it takes much effort to teach, after all it's a pain in the butt to go through the whole process, besides "it's a pain in their butt, not the fitter." You can simply have someone use a plumb-line and call it good, sit on things that really hurt, who cares. It would seem the industry doesn't care! That means the guy who thinks they aren't part of the industry. Proof is in the fact that it is used everywhere. But again, it's easy and they will never know the difference!
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