Thierry Crouzet

Automatic translation from french

It all started with recurrent buttocks. A friend told me "change my saddle, it changed my life. " I listened to him. In a bike shop, I sat on an electronic seat that measured my distance between the ischions, the two bones in contact with the saddle, then the salesman advised me a saddle, a Specialized Power, which immediately improved my cycling foundation.

I was not sitting in an armchair yet, but nothing stopped me from cycling several days. By dint of creaming, I fired more or less well. I also had a lot of neck pain. I raised my gallows, I had less pain, but it was far from perfect. The more I drove, the more I told myself that a postural study was needed. But I discovered something to greatly reduce my neck pain: I removed the visor of my ATV helmet. My field of vision widened, I raised my head less, and I forgot the postural study.

Sometimes a friend from behind gave me advice. "Lift your saddle, go back there, reposition your brake levers. Gradually, I discovered a comfortable position, but that did not erase all tensions. Accustomed to running, I thought it was normal to have pains, even on my bike.

Once in Florida, I started gravel. My saddle time has increased and new pains have arisen, including ants in the hands and tension in the shoulders. Nothing penalizing, I continued to roll three or four times a week until I felt knee pain. I was immediately on my guard. I practically stopped running because of a windshield wiper syndrome and the bike was waking him up.

I knew the theory: "Evil above the knees, saddle too low, badly below, saddle too high. But how much saddle? To advance it by how much? How much back? Adjust the holds under my shoes? There were too many possibilities for me to experiment at random. I did some research, read a lot of tips, often contradictory, until I found John Weirath's YouTube channel. I can talk about a revelation. I watched and watched John's videos. If I had lived near him in Colorado, I would have run to ask him to do a postural study.

I had to see his video on the knee ten times. John explains why we often have knee bumps on our bikes. If our saddle is not high enough, we bend the leg too much when the pedal is at 12 o'clock and we risk heating tendons and cartilages. The ideal angle of the leg and knee would be around 65 °; less, the saddle is too low; more, it may be too high.

Premières mesures
Premières mesures

But how to measure this angle? John explains that a static measurement is impossible. You have to pedal and be filmed, then analyze the images. Ideally, you need a home-trainer and a phone capable of filming in slow motion. Nothing more. Except in Florida I do not have a home-trainer. So I asked my wife to film me while I was driving in front of the house. Thanks to a web service advised by John, I started to analyze my posture.

The angle of my leg was 62.3 °, so I pulled the saddle a good centimeter to reach a higher angle, I never managed to fall on 65 °. But this angle is only one of the many parameters mentioned by John. Always in the pedal position at 12 o'clock, the foot must be inclined between 15 ° and 35 °, the pros going up to 40 °.

Position 6 heures
Position 6 heures

John evokes another fundamental angle: pedal positioned at 6 o'clock, the angle of opening of the knee should be between 34 ° and 48 ° (and not between 25 ° and 35 ° as many think). The higher the saddle, the smaller the angle. At this point, keep in mind that moving the seat back up raises it, as the distance from the widest part of the saddle to the crank axle increases. So to adjust the angles, it is necessary at the same time to play on height and horizontal position. So, film after film, I managed to contain my knee pain.

Après ajustement
Après ajustement

Another good advice from John: on a racing bike or gravel, align the forearm on the third metacarpal of the hand when it is placed on the casseroles. I turned my hanger up a few degrees and the ants disappeared overnight.

At this point, I understood three things.

  1. On commence par régler ses chaussures.
  2. On positionne la selle en hauteur et d’avant en arrière. En théorie, on aboutit à un réglage valable pour tous les vélos. Il définit notre position de pédalage optimale en termes de performance et de confort. Pour une selle donnée, cette position est décrite par deux valeurs : la distance horizontale entre le nez de la selle et l’axe du pédalier (saddle fore-aft), la hauteur de la selle, mesurée par exemple entre l’axe du pédalier et le milieu de la selle (ou évaluée verticalement, ligne pointillée sur image ci-dessous).
  3. On termine par le guidon, sachant que plus on penche vers lui, plus on relâche la pression sur notre dos et sollicite nos bras, épaules et cervicales. J’ai passé l’âge de l’aérodynamique, d’où m’a position redressée.
Mes réglages de départ
Mes réglages de départ

On my gravel, I completed a fore-aft of 100 mm and a height of 75 cm. I felt better, even if it was not perfect yet. I transposed these settings on the rigid mountain bike that I use for bikepacking. I chained two raids with no other problem than irritation on the left buttock, quite embarrassing to tell me that it was time to consult a specialist. During a ride, a friend advised me to contact Dwayne Adams, according to him the best bike fitter in Miami. So I made an appointment with him.

The session lasted a good three hours.

Step 1 Dwayne asked me about my practice and purpose (comfort above all else). Then he studied my body, my flexibility, he measured my crotch (inseam), my distance between ischia. He deduced that I was average, so the simple client type.

Step 2 Dwayne observed my feet, finding that I was pronator, which sometimes requires custom soles. He evaluated the angle of articulation of my foot with respect to the axis of the foot. In theory, for maximum power, the axis of the pedal cuts the joint in the middle. At home, the angle is low. Vertically, there is only one centimeter between the joint of the big toe and that of the little toe (between the two lateral bumps). The clips under the pedals must be moved 5 mm away from the big toe joint. Dwayne used the Ergon TP1 kit to adjust the holds (knowing that mine was pretty much adjusted).

Réglage des cales
Réglage des cales

Ideally, a bike fitter should have soles with pressure sensors, so that the clips can be adjusted for optimum power transmission. As a standard customer, I thought that a standard method suited me, especially since I have never suffered too many feet, even during very long outings. I just do not over tighten my shoes.

Still, I found Dwayne very sure of himself on this one. John reiterates that there is no standard setting. In the event of tension in the calf or Achilles tendon, the shim must be moved back towards the heel. In case of pain in the arch, it must instead advance. Dwayne positioned me in the middle, which would be wise in the case of a standard customer.

Sur mon vélo virtuel
Sur mon vélo virtuel

Step 3 Dwayne recreated my bike on his Trek simulator and I started pedaling, on the eyes of two cameras.

Step 4 While filming me in slow motion, Dwayne gradually adjusted the height and position of the saddle, until all the parameters evaluated were in green.

Extension maximale
Extension maximale

Parameter 1: Maximum Extension As I had done following John's advice, Dwayne evaluated my maximum extension (34.3 °). Acceptable range according to Trek: 30-40 °, so different from the 34-48 ° postulated by John (which proves us that the postural studies are not scientific and depend above all on the bike fitter).

KOPS
KOPS

Parameter 2: Knee Over Pedal Spindle KOPS This is the position of the knee relative to the pedal axis when the pedal is at 3 o'clock, which should be within +/- 2 cm for a standard cyclist ( the plumb line method is outdated).

BMR
BMR

Parameter 3: BMR (Body Mass Representation) Pedal at 6 o'clock, we checked that my mass is centered on the pedalboard. Fork: 0 + 7-2 cm.

Angle minimal du genou
Angle minimal du genou

Parameter 4: Bent knee Dwayne does not measure the minimum angle of my knee bent the same way as John. I adjusted this measure a posteriori. I end up at a high angle of 71 °, but you should know that this angle continues to fall when the pedal exceeds 12 hours. On the video capture, it is necessary to look a little further for the point of maximum bending, which then must not be far from the 65 °.

Genou plié et angle pied
Genou plié et angle pied

Parameter 5: Ankling We checked the angle of my foot, pedal at 9 o'clock. I am at the upper limit of the expected range, between 5 ° and 30 °.

Coudes
Coudes

Parameter 6: Elbows The arms should be slightly bent for comfort, between 15 ° and 25 °. With 34 °, I am very very comfortable.

Épaules
Épaules

Parameter 7: Shoulders For the sake of comfort, I'm slightly off fork, 90-120 °.

Torse
Torse

Parameter 8: torso Always according to Trek, it must be inclined between 20 ° and 55 ° (angle measured between the hip joint and the ear lobe).

Trajectoires des genoux
Trajectoires des genoux

Parameter 9: Knee Paths The farther they go, the better, but Dwayne tells me he has a range of +/- 5 cm. Since I am straight on the left and barely eccentric on the right, I would not need to adjust the position of my holds or wear custom soles.

Après étude posturale
Après étude posturale

Step 5 It's time to postpone the new settings on my bike. Surprise: only one parameter has varied. The fore-aft went from 100 mm to 85 mm, which resulted in a slight reduction in the distance between the pedal and the middle of the saddle. The postural study has practically confirmed my own home study.

Etude de la selle
Etude de la selle

Step 6 There was one important thing to deal with: the saddle. Dwayne put a pressure sensor on mine, and then he asked me to pedal. He varied the inclination to minimize the pressure points. I arrived with an inclined saddle forward of 7.6 °, I left with a horizontal saddle. Dwayne had me try a dozen more stools to see if one was better for me. On all, points of pressure appeared. So I kept my saddle.

The next day, I was on the levees with my gravel. I had the impression of having a new bike, while only the fore-aft and tilt of the saddle had changed. Result: absolutely no pain in the buttocks. Ten days later, I can only confirm Dwayne's choices. Side knees, it's ok, no more (I may need a break to rest the accumulated tension).

So must we pay? Two friends with a home-training and a little patience can arrive at a more than correct result. To go further, to go into physiology, you must consult a bike fitter of the caliber of John Weirath or Dwayne Adams. It is also necessary to listen to one another, not to make any definitive adjustments, so one must understand the various measures and allow oneself to change them.

I'm not finished learning things on the bike.