An Exercise Bike Ergometer Designed
for General Accessibility
Ryan Pope1, Jon Millin2, Amit Mehta3,
Jeff Swift4
1)
Department of Biomedical Engineering,
poper@cae.wisc.edu, Office: 608/263-0008, Fax: 608/265-9239,
2)
Department of Biomedical Engineering,
3)
Department of Biomedical Engineering,
4)
Department of Biomedical Engineering,
An Exercise Bike Ergometer Designed for General Accessibility
Abstract
An Accessible
Exercise Bike Ergometer usable by persons of various ailments as well as those
without was built. The project began
with a commercially available exercise bike (NordicTrack SL710) and made
modifications to increase the accessibility.
The modifications include; seat assist, power adjustable seat, arm
motion exercise, walkthrough frame, lighted pedals, and improved user
interface. The seat assist aides people
who can no longer get up unassisted due to insufficient upper or lower body
strength. The power seat allows easy
seat adjustment as well as allows unlimited positioning of the seat for
users. The arm motion exercise allows a
more full body workout than a pedal bike alone would provide. The walkthrough frame allows unobstructed
access to the seat. The lighted pedals
allow them to be easily seen by users of low vision and help initiate motion
for users with Parkinson’s Disease. The
improved user interface addresses low vision and colorblind users. A prototype was built and tested using human
subjects and no significant difference in the accessibility was recorded
between control and test subjects, demonstrating general accessibility. An increase in accessibility verses standard
exercise equipment was observed for the test subject group, demonstrating an improvement
for patients with ailments.
Key Words: disability, accessible society, ailments
Introduction
The aim of this project was to build a
creative cycle ergometer that is usable by individuals with a diversity of
abilities. The specific disabilities
addressed include; post-stroke effects of limited arm function and necessity of
a cane for walking, diabetes, poor eyesight, morbid obesity (BMI over 40),
heart failure, generalized low strength and flexibility, and Parkinson’s
disease effects. Users that fall into
one or more of these groups commonly complain of an inability to use standard
exercise equipment which leads to a higher proportion of these users living
sedentary and potentially unhealthy lifestyles.
Methods
To accommodate for
the post-stroke symptoms of limited arm function, the ergometer arm exercise
motion was made to be independent between the left and right side to allow just
one arm to exercise. Additionally the
push and pull resistances were made to be independently adjustable to accommodate
for strength variations between the extensor and flexor muscle groups. To address the requirement of using a cane to
walk, the ergometer was made to have an easily accessible cane holder to allow
placement of the cane prior sitting.
This cane holder was strategically placed to be intuitive for a cane
user and so that the cane is within easy grasp when ready to exit the
ergometer. For users with poor eyesight
and those who are blind, the user interface was made with a large LCD touch
screen and well-defined readouts and buttons.
Obese users require a structurally stable ergometer that is capable of
supporting in excess of a 400 pound load, so mild steel was used throughout for
the weight bearing structures. To
accommodate heart failure users, the ergometer contains an EKG readout which
could be coupled to a warning system against potential overexertion. To assist users of low strength and
flexibility, the seat position and all resistance controllers are readily
accessible and require minimal effort to adjust. For users with Parkinson’s disease, a method
of helping initiate the movement to place their feet on the foot pedals is
incorporated, as well as a method that will assist these individuals in entering
information into the user interface [6].
NordicTrack
SL710
The
existing commercial design that was utilized for this project was the
NordicTrack SL710. It was chosen because
it is a recumbent cycle that incorporated magnetic resistance, EKG/pulse
sensors, a console and ergonomic pedal placement
A
recumbent ergometer was chosen over an upright cycle ergometer due to two main
factors: support of the user and stability.
A recumbent style exercise cycle allows for the user to have their body
supported when seating in a reclined seat compared to a bicycle seat that is
used for upright stationary cycles. This
reduces the amount of pain that is experienced by people in their lower
back. Additionally, a user in a seated
position is more stable than a user perched on a raised seat.
The
magnetic resistance used on this style of NordicTrack cycle is referred to as
SMRTM, Silent Magnetic Resistance.
The SMR system (Figure 1) enables changes in the pedaling resistance by
having a metallic flywheel rotating through a magnetic field. As the flywheel passes through a greater
portion of the magnetic field, the resistance is increased. The magnetic field is generated by permanent
magnets that are mounted on a C-shaped bracket.
Since the magnetic resistance is a smooth operating and easily
controlled resistance design, it was kept intact and utilized along with the
existing pedal drive train for rotating the flywheel.
Figure 1: Sketch of Flywheel/Magnetic Resistance
System [5].
Another
aspect of the NordicTrack SL710 that was left basically unchanged was the
CardioGripTM EKG/pulse sensors.
These sensors work by detecting the EKG through the metallic conducting
palm sensors and then relaying the signal back to the computer where the heart
rate can then be calculated and sent to the display. This pulse detecting system is not as
accurate as other methods such as pulse oximetry or a telemetry strap, but it
can be used by a wide variety of people with very low strength and dexterity
and thus was appropriate for the prototype.
One
final aspect of the commercial bike was deemed sufficient for a final
prototype, the seat. The original seat
padding and general shape was left intact and the angle between the seat base
and seat back was left unchanged. The
one small addition made to the seat base was the lift seat assist system, which
is addressed elsewhere in this report.
Modifications
to Existing Device
The
first concern addressed when modifying the commercially available bike for
general accessibility was the incorporation of a walkthrough access, or zero
step-over technology (Figure 2). Zero
step-over technology means that the user would not have to lift a leg and
maintain balance on one foot to get onto the bike.
Figure 2:
Zero step-over technology access walkway.
The implementation
of a zero step-over technology led to one other major and beneficial change to
the commercial bike. To make more room
for the walkthrough, the original manual seat locating system was eliminated
and replaced with a power seat system that was mounted lower than the original
system.
Additions
to existing device
Power and Lift Seat
The
powered seat locating system was made in such a way that the seat would travel
through the same path in space with the new system that it traveled through
with the original system. Thus the angle
of the seat track was maintained at approximately the original 22.6° and the
seat was placed in exactly the same reference to the pedals as it was
originally. A new mounting platform for
the seat and the future arm motion was created utilizing rectangular steel
tube. On the outside of the new seat
platform, rollerblade wheels were attached that would ride on a new track
system. Additionally, secondary wheels
were attached to the bottom of the seat platform and these wheels ride below
the seat track to keep the seat platform locked to the track in the same way a
roller coaster is locked to its track.
The new track system was constructed from angle iron set to the width of
the seat platform and the proper length to cover the full range of travel of
the 500 lb linear actuator which is used to control the seat motion.
Once
the locating system for the seat was established, improvements for the seat
itself could also be addressed. Since it
can be difficult for some users to stand from a fully seated position due to
insufficient upper or lower body strength, a lift assist based on a 100 lb.
pressurized lift cylinder was incorporated into the seat (Figure 3).
Figure 3:
Lift seat configuration.
As
the seat travels up, a portion of the 100 lbs. that the lift cylinder can
generate is exerted to aid the user in getting to a standing position. Additionally, a spring was added to the force
cylinder so as the seat angle approached 0°, the force generated by the spring
would add to the total force exerted and the piston force would not go to 0
lbs. The lift force generated follows
the graph seen in Figure 4. A limiting
chain was added to allow the seat to achieve an angle no greater than 45° for
ease of sitting down.
Figure 4:
Lift force as a function of seat angle.
Arm Motion Exercise
Along with lower body workout provided by the cycling
motion, users can also obtain an upper body workout using the arm motion
exercise. Furthermore, both components
(arm motion and the cycling motion) can be performed together to allow for a
total body workout. Also, since the upper body and lower body workout are
independent of each other, the user has total control of his/her exercise
routine.
The arm motion is controlled by four independently variable
resistance pistons. Using independent
pistons is unique in the sense that it allows patients with limited one arm
function to conduct exercise with only their functional arm and not worry about
the unused handle coming back at them, as it would if the arms were tied to the
same resistance system. The pistons are
capable of a 5-200 lb. load controlled with an adjustable dial that ranges from
1 to 12, with increasing number on the dial corresponds to higher resistances. The two pistons are attached to each handle
to provide both push and pull resistance.
A free body diagram for the piston placement is shown in Figure 5. It was found that the minimum force a user
would be required to exert on the arm handle to move it is only 3.70 lbs, while the maximum
force can be up to 93.08 lbs. The final
design is shown in Figure 6.
Figure
5: Free body diagram of arm motion. Fuser is the force exerted by the
user,
and Fpiston 1 and Fpiston 2
is the force of the piston resisting the motion induced by the user.
Figure
6:
Arm Motion Exercise
Arm EKG Handles
Arm handles were
incorporated to give a clean place to grip when exiting the device and as a
convenient location for the EKG/pulse rate sensors (Figure 7). The placement of the handles puts them within
easier reach of the user than if they were by the user console and also
eliminates potential motion artifact in the EKG signal that would come if they
were placed on the arm motion handles.
Figure 7: Raised arm handles with heart rate sensors
The handles were
mounted on a pivoting system to allow each handle to be pivoted out of the way
of the user to allow uninhibited access to the seat. The pivot system consists of two bolts that
pass through the handle bars. Each bolt
rides in a notch that allows a 1/8 rotation of the
handle. When each of the 1/8
rotations occur together, the handle can travel through a Ľ rotation and rotate
up and out of the way of the user.
Wireless LED Pedals
Some people with Parkinson’s Disease have
an inability to initiate motion, which means that if you tell them to take a
step they can not do so, but if you tell them to step over a line draw on the
floor they are able to do so. To address
this we theorize that by putting red LEDs into the pedals and coupling that
with audio output instructing the user to place their feet on the pedals, this
will help users with Parkinson’s to overcome the problem of initiating motion.
A second advantage of incorporating
wireless LED pedals became apart during testing; people with low vision are
more able to see the pedals when the exercise bike is on a dark floor with the
presence of the illuminated LEDs. Figure
8 shows the LED clearly illuminated on the pedal.
Figure
8:
Illuminated left pedal.
The LED system was made wireless to overcome
the problem of the continuous rotation of the pedals and also to make it
triggered automatically upon sitting on the seat.
User Interface (LabVIEW based)
To increase the
ease of viewing and the ease of use of the user interface, a completely new one
was made using a 15” touch screen monitor and LabVIEW programming. The new user interface was made to contain;
large lettering, high contrasting images, large buttons/controls, easy to
understand terminology, simple controls, and advanced layout / simple layout
options to tailor to the user. A typical
screen shot is seen in Figure 9.
Figure 9: User interface
Screen Shot
Human Subjects Testing Procedure
Subjects
were from the
Results and Discussion
Four experimental subjects and four control
subjects were recruited. The responses
obtained from each participant through the post-experimental survey are
tabulated and reported below in Figure 10.
Figure 10:
Results of human subjects testing with standard deviations
It was found that most
participants found the prototype readily accessible. Because of the small
number of participants in both the control and experimental group, the standard
deviation was quite high. Based on the results of the ability to enter
and exit the prototype, both groups found it easy to access the device and exit
upon completion of exercise. Nearly all subjects liked the idea of
implementing the seat assist because they liked the extra help when standing
from a fully seated position. The lighted foot pedals was another feature
brought up by our participants as positive. Since they were activated
wirelessly upon sitting, it was very easy for the subjects to find the foot
pedals, especially those with low vision. Lastly, most subjects liked the
idea that we added an arm exercise to the bike. They felt that it gave
them more variability in their exercise by allowing upper and lower body
workouts. Our experimental groups
pointed out that having a bike with dual independent upper and lower body
exercises was unique in the exercise equipment field.
One of the main negative feedbacks that we received was that it was hard to
adjust the pistons for the arm exercise. Because we had to change the
initial design of the arm exercise to increase bidirectional function, the
location of the pistons and number of pistons was changed, which made it harder
for users to adjust the piston resistance.
The design has 4 total pistons, two of which being close to the ground and
thus farther from the seat, which makes the users had to lean far over to reach
them all, and also has twice as many to adjust.
In
general, users appreciated the added components such as the seat assist, power
seats, and the simplified user interface. Our test groups liked the newly
designed bike we created and were able to see it being useful for people with
various disabilities as well as those without.
Conclusions
In
the end, most participants found the prototype readily accessible and were able
to provide useful feedback for the design team.
While subjects and controls in general rated the device high in quality,
certain areas were found that require improvement. First, and most importantly, the user
interface must be completed. To
accommodate blind users, an audio output should be incorporated. This can be done using the LabVIEW program,
and only requires additional computer programming and the downloading of the
program onto the computer. Second, an
additional handgrip should be added to the arm motion handles below the current
grip to make the overall length of the grip four inches longer. This will allow a place to grab on the
handles for shorter people instead of them holding onto the bare metal of the
arm motion handles. Third, there is a
section of the seat track that could potentially cause injury and should be
changed. A section of the angle iron
that was used to construct the track protrudes near the walk-through
platform. When the seat is moved
forward, this piece could possibly catch the front of a user’s shoe, thereby compressing
the user’s foot between the steel and the seat platform. By cutting this small section out of the seat
track, this problem can easily be eliminated without changing the function of
the track. Fourth, the weight of the
device is too heavy for users with disabilities to transport. A solution to this problem is to use a
lighter, yet still sufficiently strong, material throughout.
With these
improvements in mind, we feel that we have built an exercise device that would
be enjoyed by people with various abilities and that our device would be of
great benefit for people who may have trouble using currently existing exercise
devices.
Acknowledgements
The authors would like to thank Dr. John Enderle from
the Department of Electrical and Computer Engineering at the University of
Connecticut for proposing the competition that lead to this research, as well
as our advisor Dr. Justin Williams of the Department of Biomedical Engineering
at the University of Wisconsin – Madison, and Dr. Kreg Gruben of the Department
of Kinesiology at the University of Wisconsin – Madison for all their
assistance and guidance.
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