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Could you tell the difference between various saddles in a blind test? How much weight do you put on the saddle vs the pedals and the handlebars? And does bike fit and position affect these things?


After two and a half years of research at the University of Colorado, Fizik and associate professor of integrative physiology Rodger Kram have been able to quantify these things and more as part of an ongoing exploratory study. While the complete findings will be published soon, BikeRadar had the opportunity to visit Dr Kram to learn about the study and take part in an example blind test of saddles.

“We wanted to change the way we do things,” Fizik’s Alberto Fonte said of the Italian brand’s partnership with the CU Locomotion Lab and Dr Kram. “The aim of Fizik is to be the connection between the man and the machine. In order to make better products for the rider’s three contact points, we want to understand as much about that connection as we can.”

While some companies will occasionally trot out an academic expert to endorse a product, Fizik has taken a different approach, at least for now. Dr Kram said he gets approached all the time by companies asking him to ‘prove’ that their product has value, and he has no interest in this. “Here, we are not asking equipment-specific questions, but basic questions,” said Dr Kram, who decades ago invented a running treadmill that measured the forces a runner creates in motion.

Some of those basic questions – such as, what is the division of pressure across the contact points? – have led to other questions, such as investigations about the weight distribution on each wheel for pros vs amateurs who set up their own bikes vs those who have had Specialized Body Geometry fits or Retül fits.

How much information can be gleaned by measuring the three-dimensional forces applied to a saddle? And how much can a rider tell about a saddle by riding it blind?

Although Dr Kram’s personal passion is running – he hasn’t missed a single day of running in eight years – his connections to the cycling world are deep. Dr Allen Lim, the founder of Skratch Labs nutrition who has worked closely with scores of top pro cyclists over the years, was a student of Dr Kram’s at CU. So was Todd Carver, who created the Retül bike-fit company.

To answer many of these questions, Fizik, Dr Kram and his team of students first needed to create a tool that could quantify the forces at work in that man/machine connection on the bike. So, Dr Kram’s team overhauled a Retül Müve dynamic fit bike, affixing force transducers underneath the three points of contact, and adding a Powertap wheel to verify the build-in power meter. They then wrote custom LabView code to capture three-dimensional data streaming from the sensors.

Dr Kram’s team has completed the following studies 1-6, with 7-9 still in the works. The test subjects are male cyclists, aged 18-45, who ride at least 100 miles or eight hours a week. Fizik and Dr Kram hope the findings of the last three tests could inform how brands, bike shops and riders make and select saddles.

Power study, 1-4w/kg – to determine standard for future tests Cadence study, 60-110rpm – to determine standard for future tests Hand position – tops vs drops vs hoods Rider position and saddle – road vs triathlon Handlebar stack and reach – how does this affect forces at stem, bb and saddle? Front/rear wheel rider weight distribution – self-set position vs Body Geometry fit vs Retül fit, plus pro rider data Center of pressure location as saddle is moved fore/aft Saddle discrimination ability – can riders differentiate between saddles in blind test? Subject ride comfort – can this be somehow quantified?

While some of the tests confirmed some of cycling’s common wisdom – increasing watts at the same cadence decreases pressure at the saddle, for instance – some of the findings were unexpected. And even for the findings of the first type, the quantification of these generally held thoughts are notable. This author, at least, has not seen these types of forces measured in this way before.

Note that Dr Kram’s team did not do pressure mapping on the saddle. You may have seen pressure mapping images in conjunction with saddles or bib short marketing material, where colors are used to highlight different levels of pressure. Instead, the total and directional forces on the saddle (and stem and BB area) were measured, regardless of where on the saddle they were applied.

The CU Locomotion Lab in the integrative physiology department wrote custom software to handle the streams of data from the sensors the attached under the saddle, bar and BB area of a Retül Müve dynamic fit bike

Dr Kram’s team settled on a sustained power output of 2w/kg at a 90rpm cadence for all the subsequent data acquisition.

Some of the findings included:

a rider’s weight is distributed roughly 40/15/45 to the saddle/stem/BB

Power

per increase of w/kg increase of power, forces decreased 3% at the saddle and 1% at the bottom bracket

for fore/aft forces, riders averaged 20% at the saddle, and a balancing 12% at the stem and 8% at the BB

Cadence

increasing cadence caused saddle forces to increase slightly but forces at the bar were nearly constant from 60-110rpm

Hand position

riding on the hoods increased pressure at the saddle, compared to the tops and drops, surprisingly

Position and saddle

changing saddles didn’t affect forces at the three contact points

TT positions put less pressure on the saddle and BB but more on the stem

Bar stack and reach

stem pressure decreased as the bar got higher, but saddle pressure stayed the same

surprisingly, as bar reach increased, saddle force increased and stem force decreased

Front/rear wheel weight distribution

self-fit cyclists had the closest weight distribution to select BMC and Cannondale riders

front/rear weight amateurs pros (distribution in %) BG Fit self-fit Retül average 32.9 / 67.1 38.5 / 61.5 44.7 / 55.3 40.4 / 59.6 standard deviation 2.2 4.9 2.1

Saddle discrimination ability

although still ongoing, 12 of 23 tested subjects couldn’t differentiate between two saddles when riding blind (Riders completed three short sessions, riding one saddle once and the other saddle twice, but in a random order. Then they were asked to list that order, such as A, A, B or A, B, A.)

The author did the blind saddle discrimination test… and passed (phew!)

Dr Kram and representatives from Fizik said that the study has perhaps generated as many new questions as quantified answers to others. For instance, as Dr Kram’s team was surprised to see saddle forces increase as handlebar reach increased, they are investigating ways to measure muscle activity at the back to try to account for this.

“We thought going into this that perhaps bike fit could be done by looking at the forces put on the contact points instead of angles, as is done now,” Dr Kram said. “Our stack/reach study contradicted this.”

Going forward, the big question for the team is whether a rider’s subjective report of comfort can somehow be quantified, or at least correlated with some of data-based number scale.

BikeRadar will report back with more information from this ongoing study as it becomes available.


Could you tell between two saddles only by sitting on them, without looking? This study suggests that half of you could not