Big & Tall
riders position - The challenge of the body geometry of bigger
riders.
Many of us ride for weight management. Health and fitness are
the goal. Cycling is the best low-impact exercise to achieve
weight goals and cardiovascular health. But for certain
individuals their body geometry clashes with the bicycles
interface and causes discomfort, pain and even injuries.
How can a big and tall cyclist prevent from being sidelined from
the bicycle due to injuries?
The challenge facing Big & Tall riders can be quite daunting.
B&T riders approach cycling as the best option for low impact
exercising. Often, B&T riders are precluded from other aerobic
activities like running because of the high stress imposed on
the knee due to their weight. Cycling provides a great
alternative being low-impact in nature.
Bicycles are designed with an average human being in
mind: the 95 percentile man is 5'8" in height and about
160 lb in weight. This is not very representative of the B&T
segment of the population and poses a challenge. As a result,
B&T cyclists can find interfacing with the bicycle a difficult,
often painful and even damaging proposition.
| The challenge starts
from the body geometry of B&T cyclist in the interaction
between the upper and lower body: strong legs and
-typically- a larger waist line. When at the top
of the pedal stroke, there is a collision between the
stomach and the quad as the leg reaches the highest
point in the pedal revolution. The result of this
collision forces the quad to move out and sideways at
the top of the pedal stroke. Sometimes, the width of the
saddle nose is also a problem: a wider nose causes the
quads to push out also.
This, in turn, throws the knee out of alignment and away
from the bio-mechanically correct straight up/down
motion parallel to the plane of the bicycle frame. The
Q-Factor -the width of the pedal stance- is affected and
must be increased to keep this knee alignment in a
healthy state.
The challenge continues with the small range
of choices when it comes to adjusting Q-Factor. Ideally, we
would want the knee to track perfectly parallel to the frame of
the bike. Crank arms and bottom brackets come pre-installed on
the bicycle and often the consumer has no choice in their
selection. Even if given the choice, there isn't a great deal of
options for widening the stance.
The problem is further aggravated by pedals.
The commonly available pedals have a fixed spindle width,
further reducing the options for adjusting the Q-Factor in the
quest for healthy knee tracking. |
 |
The combination of the body geometry of the
rider and the limited options in Q-Factor choices is what brings
out the problem for B&T riders. The typical knee tracking of a
B&T cyclist is 12 deg of tilt as compared to the plane of the
bike frame - ideally, we'd want between 0 to ±2 deg of tilt.
 |
When a B&T cyclist pedals the required miles
to achieve his/her weight management goal, this knee position
can cause tremendous wear and tear on the joints and high stress
on the tendons and muscles involved in the pedaling chain.
The result? Patellar pain (that nagging pain
under the knee), IT band inflammation or tears (the pain on
either side of the knee), Achilles tendon inflammation and
tears, etc.
In this case study we discuss the case of a
B&T cyclist who sought bike fitting to resolve the issue with
knee pains when also aggravated from a pre-existing meniscus
condition.
The position of this B&T rider required a
different approach to fitting than a typical rider. Usually, the
back angle and hip angle closed parameters drive
the upper body and lower body interaction. These parameters are
connected by the rider's interaction with the handlebar reach
and seat height/forward/aft.
In the case of the B&T application, we have
to introduce an additional parameter: the quad clearance
at the top of the pedal stoke. We call this the quad angle,
the angle between the femur and the departing tangent leaving
the great trochanter at the top most quad. It's not a typical
parameter used (or even recognized) by bike fitters and bike
fitting jargon. We pioneered its use because we found it to be
very effective for B&T applications.
The quad angle has a direct relationship with
the interaction between the quads moving in/out of the pelvic
area and the stomach. It's also related to the hip angle at the
top of the pedal stroke - a critical parameter for all B&T
cyclists.
A small hip angle will cause a small quad angle
and, in turn, it will cause the leg to
reach too high and collide with the stomach. This collision, is
not only uncomfortable for the cyclist, but it also pushes the
quad out of the pedaling plane, putting pressure on the muscle
groups controlling the hip movement and forcing an increase the Q-Factor.
Often times, most fitters will
seek an adjustment at the position of the foot in
attempt to open the Q-Factor, hoping to resolve this
problem. However, this is not an effective approach. The
majority of the source of the problem is at the hip
angle and the Q-Factor is the effect, not the cause. We
can't treat just the effect. We need to go to the source
of the cause. |
The goal is to create the
least amount of interference, so we can reduce the need for
altering the Q-Factor at the pedal spindle with custom-made
accessories while we could try with off-the-shelf
components instead. It's not always possible, but it's worth the
try. This is the correct approach.
Here, we show the management of the quad
angle through the expert positioning of a rider's body to
manipulate the hip angle and the resulting Q-Factor.
It's possible to improve the position to such
an extent that even larger riders can achieve reasonable levels
of biomechanic neutrality - which means riding ergonomically
safe.
In this example we work with a mountain bike
rider. When working with MTB cyclists, we can't work in the
vacuum of the driving parameters imposed by a B&T
fit parameters and let those parameters alone set the bike fit. We must
also be always aware of a rider's positioning with respect to
handling. As part of the fit, weight balance management (CG
location) is also a driving (and very critical) parameter - together with overall
comfort.
| Finally, we introduced a custom Ti pedal
spindle solution for this rider. After the best position
possible was achieved by the process described above, we took
the Retül parameters knee tilt and knee-to-foot measurement to
have a custom pedal spindle made.
A special aerospace
grade Ti/Alu/Cro alloy spindle can be made to replace the stock
pedal spindle for B&T riders.
This spindle is wider and helps
bring the knee tracking into alignment, but it must be introduce
only after all other avenues of hip angle
and quad-angle management have been exhausted. |
 |
Over time, the width of the custom spindle
can vary. As the rider weight management goals can be achieved
thanks to safe and (mostly) pain-free riding, the body geometry
can change. With a trimming waist line, the quad interference
changes and so does the hip angle along with the Q-Factor.
Period bike fit reviews are often needed to re-align the
position to the new and improved circumstances.
Weight management in cycling is a journey
that can potentially alter a rider's life for the better. Bike
fitting is the partner in the road to success of this journey.
We are happy we could be here for this
cyclist.
OUR BELIEF:
"You don't have to be a Pro to get a bike fit. Everyone who
climbs into a bike deserves to have a great experience,
regardless of their fitness, expertise or equipment level."
A Perfect Bike Fit Pro Studio
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