If you want the best in custom articulated cycling prosthesis look no further.
After helping a local Dubbo triathlete achieve his cycling goals by building a totally new prosthetic from the ground up, I am ready and excited to build more. This project was one of my favourites and would like to move the concept into the realm of carbon fiber, it is more costly but the performance benefits would be awesome.
Professional Bike Fitter Aaron Dunford Designs Custom And
Innovative Prosthesis for Competitive Cyclist
Sydney 05, July 2012: For competitive cyclist, and amputee Gerard Cushan,
the only cycling prosthesis available on the market that allowed him to ride
and compete was flawed. A better solution was required and bike fit expert
Aaron Dunford of Fusion Peak Professional Cycle Fitting designed and built
a custom prosthesis that is ergonomic and individually tailored to allow
Gerard to cycle more naturally improving his comfort and performance.
Gerard’s right leg was amputated just below the knee as a child. Aaron’s skills,
including a strong understanding of biomechanics and cycling position and the
ability to develop and build a working prototype would soon lead to a completely
new and totally custom prosthesis for Gerard.
Gerard’s cycling prosthesis at the time was a simple carbon fibre post with a
Shimano SPD-SL cleat attached to the bottom. This caused stress on his body
while riding due to the fore and aft cleat positions being approximately 100 mm
different from foot to prosthesis causing a rotation in his pelvis. Gerard’s left leg
worked well but the right leg and the prosthesis equated to instability in his position
and an inability to stand and sprint fluently.
The totally new cycling prosthetic began as a drawing. A Turner Flux mountain
bike frame was to provide the curtail components that would eventually become
the new prosthesis. The cleat placement was a key mechanical factor in setting
up symmetry in Gerard’s pedal stroke. From the cleat up the body was to be realigned.
The prosthetic’s ankle was established early on and once working effectively, it
became important to control its’ range of motion; Gerard at 82 kg would need
something to push against. A Fox RP3 mountain bike shock was chosen to control
the ankles’ movement. The next step was to attach the prosthesis to Gerard’s
coupler (which is attached to his leg).
A shaft was milled to fit into Gerard’s coupler and a cleat plate was welded to the
bottom of the foot. The final modification was the installation of two bicycle seat
post clamps to clamp the prosthesis to the milled shaft.
Aaron returned to Dubbo to see Gerard and fit his new prosthesis. “I really had
no idea if it was going to work,” Aaron recalls, “I was very optimistic, but ready to
go back to the drawing board. The connection between Gerard’s coupler and the
top shaft of the prosthetic had to be perfect or else there was a chance that the
prosthetic would slip or twist.”
The shaft fit perfectly.
When fitting the cleat to the bottom of the prosthetic the human foot was mimicked
and the cleat was placed in symmetry. Another unique advantage of the new
prosthetic design is it can be adjusted in 5 dimensions. It can be rotated 360
degrees, it can be raised and lower to adjust for the length of the opposite leg,
the angle of the foot can be opened and closed to match the plantar flexion of the
human foot, and the shock can be adjusted pneumatically for compression and
hydraulically for rebound. These adjustments mean the prosthetic could be fitted to
any transtibial amputee.
Gerard recently wrote, “The main improvements that I perceive are:
• More comfortable due to better foot and cleat position
• Improved power conversion
• Less gear shifting required for the same effort
• Less fatigue and soreness on long rides
• Increased average speed (based on two races)
• Other cyclists have observed and mentioned a much smoother cycling technique”
About Fusion Peak
Fusion Peak is a Sydney based bicycle fitting company with a focus on rider
satisfaction, comfort and performance. With formal training from Serotta and Trek
Bicycles and methodology from some of the worlds’ greatest fitters, Aaron has
the ability to fit existing bikes (road, time trail, triathlon and mountain) or fit and
design custom bikes and frames from scratch using his Next Generation Serotta
Size Cycle. Fusion Peak now also offers custom cycling prosthetic design and
*All listed prices are subject to change without notification, and are exclusive of parts.