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What Goes Into A Professional Bike Fit

I have been working on my bike fit for the past few months by making micro adjustments, but I still struggle to find a comfortable and pain-free position to ride in. The pain in my knees kept creeping back, and my lower back screams for me to stop whenever I go for rides longer than 100km. 

So we headed over to professional bike fitter Martin Choo from Fahrenheit Performance for some help and advice on bike fitting.

Martin is the Official Fitter for the Singapore National Team and Team Allied World – Treknology3. 

 

 

Here was what went on during my 3D Dynamic Bike Fit session with Martin:

Pre-fit physical assessment 

Filling up a “rider history form”

Before commencing on my bike fit, I filled up a form asking about my 1) riding style, 2) comfort/injury status and 3) bike/equipment history. If you are planning to go for a bike fit, it would be helpful if you are clear of what your cycling goals are (e.g. how often you ride, are you a recreational or competitive rider) and your injury status so that the bike fitter can cater to your needs.

 

Click here to read more about the 5 biggest bike fit myths busted. 

 

Body analysis

Martin advised me to do some lunges at home regularly, then progress to lift some weights as well

 

Before getting onto the bike, Martin accessed the strength of my legs. When I did single and double leg squats, my knees pointed inwards. That was a sign that I have weak glute muscles and tight hip flexors.

“Cyclists often don’t use their glutes enough; we tend only to use our quad muscles.” Martin advised me to do some lunges before a ride that would help to activate the glutes and stretch the hip flexors.

 

Doing a straight leg raise to check for my hamstring’s flexibility.

 

While lying down, Martin did knee bends to check for my hips’ flexibility, and checked the internal and external rotation of my knee to ensure that I have a decent range of motion while cycling. 

 

To measure the natural angle of your feet, sit on an elevated chair and dangle your feet.

 

He used a forefoot measuring device to gauge my forefoot tilt. 

 

Said Martin, When you are cycling, you want to be pedalling in a natural position. Forcing your leg to cycle in a different position and angle will only lead to injuries.”

 

 

Cleats positioning 

Featuring my speedplay cleats and Martin showed me the correct position of the cleats which will ensure maximum power transfer. 

 

I am using Speedplays on my road bike shoe. While adjusting my cleats position, Martin shared with me how to determine the right cleats position: “A general rule of thumb is to position the cleat so that it sits right below the ball of your foot. To do so, average the distance between your first metatarsal head of the big toe and the fifth metatarsal head of the little toe. 

“You want to position your cleat so you have the point of power transfer from the foot to be right over the pedal spindle.”

 

Martin carefully marked my shoe with a sticker. “Stickers are better than using marker on expensive shoes”

 

 

Determining the right saddle width 

Having a saddle with the correct width is one of the critical factors to a comfortable ride. 

While I was sitting on the memory foam, Martin pointed out where the sit bones are located. That’s the width that he was measuring.

 

Even if you are a big rider or you have a big bum, it does not mean that you need a wider saddle. The width of your sit bone -the bony ends of your pelvis that bear most of the weight when you are in a saddle- is independent of your body size. 

 

The “fancypants ass measuring device” as Martin puts it.

 

Here’s the memory foam that I sat on. The two impressions created are indications of where my sit bones are. According to the scale, I fall in the green range, which means that I need a saddle with a width of 155cm. 

 

 

Now onto the bike

 

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Martin uses the Retül system, a 3D motion capture device that captures your cycling movement at 15 frames per second. You can also do a fit on a Retül bike before purchasing your own. This way, you will know what bike size suits you before splurging on one. 

After positioning my bike onto the trainer, he proceeded to place LED markers on eight anatomical points on each side of my body: the wrist, elbow, shoulder, hip, knee, ankle, heel, and toe.

As I pedalled, Retül’s Vantage Motion Capture System gathered real-time, 3D data of my pedal strokes and movements. The platform I was on could be rotated, so Martin could collect data from my left and right sides without needing me to leave the bike. 

 

 

The path of travel of your knee and amount of deviation from side to side should show straight lines in a closed loop. Generally speaking, side to side movement of less than 30mm is optimal to reduce the risk of overuse injuries.

 

 

Column 1: left side of body. Column 3: right side of body. Yellow numbers: out of range. Green numbers: within range 

 

The ranges are dependent on what sort of cycling discipline you are doing; road, triathlon, or mountain biking.

The real-time data of my pedal strokes are compiled into the Retül fit software. A good bike fitter knows that the optimal fit for an individual does not mean that all the values have to fall within the recommended range. Your comfort is ultimately the most important factor.  

 

 

Recording down the finalised measurements using a Zin tool

 

The Zin, Retül’s handheld digitiser, allows the fitter to digitally measure the rider’s bike at 13 to 15 points, depending on the bike. The Zin can measure fixed points, contours, and curves, and provides a complete digital map of the bike. 

The data includes the rider’s profile, measurements from the fit, bike measurements, and the rider’s final fit position. So let’s say I am purchasing a new bike, I can transfer these measurements over. 

 

My bike measurements are recorded after being “zinned”

 

 

Before and after 

My position before (left) and after bike fit (right)

Before making any adjustments, I was stretched too far out, which might be the reason for my lower back pains. After doing the bike fit, I was riding in a more upright position. 

 

Changes made to my bike position:

  • Saddle height: +3mm
  • Saddle tilted down slightly 
  • Saddle position: +10mm forward 
  • Cleats: Set to be neutral over the 1st/5th metatarsal heads

Even though the adjustments were minimal, the differences in my comfort and performance levels were noticeable. When I went out on the roads again, I felt more comfortable and could power more through the pedals. I stopped bouncing on the saddle too. 

 

Martin also made some recommendations post fit:

  1. Start a cycling-specific strength and stretching routine 
  2. Concentrate on core strength and flexibility 
  3. Work on hip flexor mobility and glute strength 

After the bike fit, you will also receive a Personal Bike Fitting Report which includes snapshots of you on the bike, a summary of the adjustments made during the fit, the Zin Report, and your final bike position. 

 

 

SportsIN Cycling would like to thank Martin from Fahrenheit performance for having us over at his clinic. If you would like to know more about his bike fitting services, please click here

Esther Koh

Author: Esther Koh

Cycling is her drug and therapy.
She is a certified Nutritionist (BSc Nutrition, University of Leeds) and loves both road cycling and mountain biking. She hopes that more females in Singapore will discover the joy and simple pleasure of riding a bike.

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