U.S. patent application number 14/174090 was filed with the patent office on 2014-08-21 for exercise machine for use with lower body negative pressure box.
This patent application is currently assigned to The Government of the United States of America, as represented by the Secretary of the Navy. The applicant listed for this patent is Christine M. Dailey. Invention is credited to Christine M. Dailey.
Application Number | 20140235412 14/174090 |
Document ID | / |
Family ID | 51351604 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140235412 |
Kind Code |
A1 |
Dailey; Christine M. |
August 21, 2014 |
Exercise machine For Use with Lower Body Negative Pressure Box
Abstract
A compact, portable, lightweight, easily transportable leg press
exercise apparatus to simulate both exercise and the daily activity
of sitting in a microgravity environment. The exercise portion of
the apparatus creates stress on the lower extremities by supplying
a variable resistance to a reciprocating foot pedal by way of a
coil spring and damper system acting through a four-bar linkage.
The leg press exercise apparatus is paired with an existing Lower
Body Negative Pressure (LBNP) box to add an evenly distributed
pressure-induced stress to the lower extremities. By combining
resistance exercise and lower body negative pressure with the LBNP
leg press exercise apparatus, the users experience one or more
times body weight (BW) in stress on their musculoskeletal,
cardiovascular and nervous systems. By achieving one times BW or
greater (artificial gravity) during exercise and two-thirds BW
during sitting, the gap between the precondition and post condition
syndrome will become smaller.
Inventors: |
Dailey; Christine M.;
(Alexandria, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dailey; Christine M. |
Alexandria |
VA |
US |
|
|
Assignee: |
The Government of the United States
of America, as represented by the Secretary of the Navy
Arlington
VA
|
Family ID: |
51351604 |
Appl. No.: |
14/174090 |
Filed: |
February 6, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61767551 |
Feb 21, 2013 |
|
|
|
Current U.S.
Class: |
482/57 |
Current CPC
Class: |
A63B 21/0421 20130101;
A63B 21/0083 20130101; A63B 2210/00 20130101; A63B 22/0056
20130101; A63B 2022/0038 20130101; A63B 23/03541 20130101; A63B
2230/045 20130101; A63B 23/0429 20130101; A63B 2208/056 20130101;
A63B 2208/0247 20130101; A63B 21/023 20130101; A63B 2023/0441
20130101; A63B 2225/09 20130101; A63B 22/0605 20130101 |
Class at
Publication: |
482/57 |
International
Class: |
A63B 22/06 20060101
A63B022/06 |
Claims
1. In a Lower Body Negative Pressure (LBNP) Box comprising a frame
adapted to accommodate a lower body portion of a subject, the frame
comprising a plurality of spaced-apart rigid members upon which are
disposed a pressure resistant material to thereby define a lower
body-receiving envelope attached to a pump which creates a lower
pressure environment (negative pressure relative to atmospheric
pressure), with the LBNP placed in a supine position inside the
box, the improvement comprising an exercise apparatus comprising: a
rectangular base frame; an adjustable sliding frame member having
opposing first and second sides and mounted on the rectangular
frame, wherein a position of the sliding frame member is adjustable
along the base frame to accommodate users of different heights; a
four-bar linkage assembly comprising a first pair of spaced apart,
parallel bars and a second pair of spaced apart, parallel bars each
having a first end and a second end, and wherein said second end of
each bar of said first pair of bars is attached at a first pivot
point to the first side of the adjustable sliding frame member and
said second end of each bar of the second pair of bars is attached
at a second pivot point to the second side of the adjustable
sliding frame member such that the first and second pairs of bars
are alignably positioned across said first and second sides of said
adjustable sliding frame member, and wherein said first end of each
bar of said first pair of bars is attached to a first support
bracket and said first end of each bar of said second pair of bars
is attached to a second support bracket; a first adjustable foot
pedal mounted on the first support bracket; a second adjustable
foot pedal mounted on the second support bracket; a first coil
spring and damper assembly attached at a first end to a first
adjustable ground pivot on said second end of said first pair of
bars and at a second end to the first side of the adjustable
sliding frame member; a second coil spring and damper assembly
attached at a first end to a second adjustable ground pivot on said
second end of said second pair of bars and at a second end to the
second side of the adjustable sliding frame member, such that each
said coil spring and damper assembly provides resistance during a
user's cyclic movement of the respective foot pedals through
compression of the coil springs; a spring-loaded pin detent
mechanism for adjusting the position of the sliding frame member to
accommodate each user; and a chair adjustable in both angle and
linear distance to apply a resistance force to a posterior side of
the user's lower extremities during use of the exercise
apparatus.
2. The exercise apparatus of claim 1, wherein the four-bar linkage
assembly comprising a first pair of spaced apart, parallel bars and
a second pair of spaced apart, parallel bars has a parallelogram
configuration such that each said foot pedal traverses a
circular-arc path at a substantially fixed angle relative to the
frame and thereby maintains a substantially perpendicular
relationship between a lower leg and foot of a user during
exercise.
3. The exercise apparatus of claim 1, wherein the chair is a two
member chair.
4. The exercise apparatus of claim 1, further comprising a linear
actuator to automatically control the position of the ground pivot
based on the user's heart rate.
5. The exercise apparatus of claim 1, wherein a mass of the
adjustable foot pedal is selected to minimize inertia forces to be
overcome by the user during operation of the exercise
apparatus.
6. A method of exercising in a Lower Body Negative Pressure (LBNP)
Box, comprising: positioning an exercise apparatus in the LBNP Box
in a supine position, wherein the exercise apparatus comprises: a
rectangular base frame; an adjustable sliding frame member having
opposing first and second sides and mounted on the rectangular
frame, wherein a position of the sliding frame member is adjustable
along the base frame to accommodate users of different heights; a
four-bar linkage assembly comprising a first pair of spaced apart,
parallel bars and a second pair of spaced apart, parallel bars each
having a first end and a second end, and wherein said second end of
each bar of said first pair of bars is attached at a first pivot
point to the first side of the adjustable sliding frame member and
said second end of each bar of the second pair of bars is attached
at a second pivot point to the second side of the adjustable
sliding frame member such that the first and second pairs of bars
are alignably positioned across said first and second sides of said
adjustable sliding frame member, and wherein said first end of each
bar of said first pair of bars is attached to a first support
bracket and said first end of each bar of said second pair of bars
is attached to a second support bracket; a first adjustable foot
pedal mounted on the first support bracket; a second adjustable
foot pedal mounted on the second support bracket; a first coil
spring and damper assembly attached at a first end to a first
adjustable ground pivot on said second end of said first pair of
bars and at a second end to the first side of the adjustable
sliding frame member; a second coil spring and damper assembly
attached at a first end to a second adjustable ground pivot on said
second end of said second pair of bars and at a second end to the
second side of the adjustable sliding frame member, such that each
said coil spring and damper assembly provides resistance during a
user's cyclic movement of the respective foot pedals through
compression of the coil springs; a spring-loaded pin detent
mechanism for adjusting the position of the sliding frame member to
accommodate each user; and a chair adjustable in both angle and
linear distance to apply a resistance force to a posterior side of
the user's lower extremities during use of the exercise apparatus;
establishing a desired position for the chair for a user;
positioning the user in the chair; and establishing and maintaining
a negative pressure in the LBNP Box relative to atmospheric
pressure whereby the user exercises while the relative negative
pressure is maintained on the user's lower extremities.
7. The method of claim 6, wherein the user exercises in accordance
with established rehabilitation protocols.
8. The method of claim 7, wherein the established rehabilitation
protocols are directed to a user diagnosed with osteoporosis or to
discourage an onset of an osteoporosis condition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application 61/767,551 filed on Feb. 21, 2013, and incorporated
herein by reference, and is related to U.S. application Ser. No.
______, filed concurrently herewith.
FIELD OF THE INVENTION
[0002] The invention is directed to a physical conditioning
apparatus for space travel and terrestrial rehabilitation
protocols, and more particularly, to an exercise machine that can
operate in a microgravity environment with a Lower Body Negative
Pressure Box or as an apparatus for rehabilitation purposes.
BACKGROUND OF THE INVENTION
[0003] Gravity has had a profound effect on the development of life
on Earth over millions of years and has shaped the anatomy and
physiology of human beings. Exposure to microgravity has been shown
to affect the body causing it to undergo a reduction in heart size
and blood volume, impaired balance control, changes in nervous
system sensitivity, decreases in bone and muscle mass, and
reduction of the immune function. Astronauts in space during short
or long-term missions have demonstrated these physiological
changes, known as space deconditioning, which may lead to
undesirable health consequences and to operational difficulties,
especially during emergency situations. Physiological
deconditioning is a critical problem in space, especially during
long-term missions. Despite physiological deconditioning, a future
involving microgravity environments is quickly becoming a
reality.
[0004] With the recent advent of space tourism and with longer
space missions planned, greater numbers of astronauts will work and
live in low-gravity environments, and the need to understand the
in-flight and post-flight consequences of this lack of gravity will
become more significant. The physiological adaptations have proven
to be less problematic while still in space, but become more
pronounced after an astronaut returns to Earth. Many different
types of countermeasures have been developed over the years,
ranging from specific diets to heavy exercise protocols that must
be performed daily by the astronauts during a space mission.
Ideally, the best way to counteract the consequences of space
deconditioning would be the use of artificial gravity through
centrifugation or other biomechanical stressors for periods of time
during microgravity exposure.
[0005] Among the countermeasures currently under testing, daily
exercise in space seems to be the most complete, since it can have
an important positive impact on bone demineralization, muscle loss
and cardiovascular deconditioning. The mechanical unloading affects
the musculoskeletal system even in short-duration space flights. It
has been reported that after only two weeks in space, muscle mass
can decrease by 20%. For missions of three to six months duration
this loss of muscle mass can rise to 30%, especially affecting
postural muscles. The decrease in bone mass is also of great
concern to space physiologists and physicians, as the normal
processes of bone formation and resorption are disturbed, favoring
a loss of bone tissue. This process begins almost immediately upon
introduction into microgravity, and can range between one and two
percent of bone mass loss per month. One of the first responses to
space flight is the shift of blood and body fluids towards the
upper body, with subsequent adaptations occurring over a few days
to lower overall blood volume through activation of several
mechanisms. It is upon return to Earth that the cardiovascular
deconditioning raises concerns by producing significant orthostatic
intolerance and decreasing aerobic performance.
[0006] Astronauts participating in space shuttle missions, which
are usually two weeks long, exercise for approximately 30 minutes
per day. Astronauts who live on the International Space Station
(ISS) for much longer periods of time are required to exercise for
approximately two hours per day. Each astronaut's exercise routine
is monitored, and can be adjusted if necessary based on his or her
monthly fitness assessment. If astronauts are scheduled to perform
a spacewalk, their exercise routines may be altered or
restricted.
[0007] Understanding how to combat the negative effects imposed by
microgravity could allow researchers to apply an exercise routine
to terrestrial rehabilitation protocols that would decrease the
required rehabilitation time. The negative effects discussed above
occur at an accelerated rate in space in comparison to on Earth,
allowing researchers to collect data faster.
[0008] One in six Americans has osteoporosis or early signs of the
disease. Even though the causes behind osteoporosis and space
induced bone loss are different, the treatments may be similar.
[0009] The human body experiences similar physiological changes as
astronauts after encountering shattered bones. When a bone is
broken or fractured the healing process is very slow or incomplete
because the blood supply is often damaged. This may lead to
amputation and/or a longer recovery time. When the cast is removed,
the weakness resulting from muscle atrophy is very apparent. The
rate of major amputations has changed throughout the course of
combat operations in the Afghanistan Theater of Operations (ATO).
This rate of amputation suggests an increasing demand on the
healthcare continuum, from the battlefield to long-term
rehabilitation centers. Again, the reasons these negative effects
occur are different but the solution can very much be the same.
Daily exercise using range-of-motion and muscle-strengthening
exercises is necessary for people to combat stiffness and regain
strength. Applying a differential pressure not only adds stress to
the body's systems; it forces the blood to flow in its most healthy
and natural way.
[0010] The effectiveness of exercise protocols and equipment for
astronauts in space are unresolved and still under discussion.
Prior studies indicate that all exercise in space to date has
lacked sufficient mechanical and physiological loads to maintain
preflight musculoskeletal mass, strength, and aerobic capacity.
Researchers have been pairing exercise with a Lower Body Negative
Pressure (LBNP) Box. The LBNP Box is a sealed device into which the
user is partially inserted. A seal near the waist allows a vacuum
to be applied to the device, thus creating a lower relative
pressure on the user's lower body. This lower pressure helps pull
bodily fluids toward the feet. Exercise within an artificial
environment (LBNP Box) has been shown to counteract
microgravity-induced deconditioning during terrestrial testing. A
recent study on the addition of a treadmill to an LBNP Box has
demonstrated that it is able to simulate the physiological and
biomechanical features of upright exercise. However, the
treadmill's mechanical design lacks mobility and is both large and
heavy, making it unsuitable for space flight.
BRIEF SUMMARY OF THE INVENTION
[0011] Resistance exercise coupled with lower body negative
pressure (LBNP) has been shown to be effective in counteracting
some of the deconditioning related problems. The development of a
compact, lightweight, and effective resistance exercise machine
that works within a LBNP Box has, however, proven to be
difficult.
[0012] In one embodiment, the resistance exercise machine for a
lower body negative pressure (LBNP) Box prevents
microgravity-induced deconditioning by simulating physiological and
biomechanical features of upright exercise and daily activities.
This combination can determine whether the kinematics,
musculoskeletal loadings, and metabolic rate during supine exercise
within the LBNP Box are similar to those of an upright posture in
Earth gravity (1G).
[0013] The compact, easily transportable, exercise machine, named
Entirety.TM., simulates both exercise and the daily activity of
sitting. The exercise portion of the apparatus creates stress on
the lower extremities by supplying a variable resistance to a
reciprocating foot pedal. This resistance is created from a coil
spring and damper system acting through a four-bar linkage. The
resisting force increases as a function of leg extension to
maximize work done by the user in each cycle of motion. The sitting
portion of the exercise apparatus creates a resistance applied to
the posterior side of the lower extremities by the use of an
adjustable chair. The angle of the chair can be adjusted to fit
each user and to simulate a force that is about two-thirds (2/3) of
body weight. Humans sit between six to eight hours a day, which
means that the posterior side is accustomed to these forces.
[0014] The exercise apparatus can be paired with an existing LBNP
Box to add an evenly distributed pressure-induced stress to the
lower extremities. By combining resistance exercise and lower body
negative pressure, the users will experience one or more times body
weight (BW) in stress on their musculoskeletal, cardiovascular, and
nervous systems. By achieving one times BW or greater (i.e.,
artificial gravity) during exercise and 2/3 BW during sitting, the
gap between the precondition (before space flight) and post
condition (after space flight) syndrome will become smaller.
[0015] In one embodiment, a leg press exercise apparatus is
provided for use with a Lower Body Negative Pressure Box. The leg
press exercise apparatus includes a rectangular base frame and an
adjustable sliding frame member is attached to the rectangular
frame for adjusting a position of the sliding frame member along
the rectangular frame to accommodate users of different heights.
The leg press exercise apparatus includes a linkage assembly having
four bars, with each pair of bars mounted at a pivot point on a
lower end on opposite sides of the rectangular frame, and mounted
at an upper end to the support bracket. The leg press exercise
apparatus further includes a pair of adjustable foot pedals with
each foot pedal mounted to a corresponding support bracket to which
a pair of bars of the linkage assembly is mounted. A coil spring
and damper mechanism is attached at a first end to an adjustable
ground pivot, the coil spring and damper mechanism providing
resistance during a user's cyclic movement of the foot pedals
through compression of the coil spring. A spring-loaded pin detent
mechanism adjusts the position of the sliding frame member for each
user. A two member chair is preferably included in the exercise
device and is adjustable in both angle and linear distance to apply
a resistance force to a posterior side of the user's lower
extremities during use of the leg press exercise apparatus.
[0016] The leg press exercise apparatus could be used to collect
and establish a database under both terrestrial conditions and
microgravity environments, such as the International Space Station
(ISS) to enhance the understanding of medical researchers of how
LBNP paired with resistance exercise impacts osteoporosis,
orthostatic intolerance and cardiovascular health. The technology
used in the leg press exercise machine could also be used to
enhance rehabilitation protocols.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other advantages and aspects of the embodiments of
the disclosure will become apparent and more readily appreciated
from the following detailed description of the embodiments taken in
conjunction with the accompanying drawings, as follows.
[0018] FIG. 1A illustrates a leg press exercise apparatus paired
with an existing environmentally controlled LBNP Box in an
exemplary embodiment.
[0019] FIG. 1B illustrates a perspective view of the leg press
exercise apparatus including leg simulation links.
[0020] FIG. 1C illustrates a side elevation view of the leg press
exercise apparatus including leg simulation links.
[0021] FIGS. 2A-2B illustrate perspective views of an exemplary
embodiment of the leg press exercise apparatus with the four-bar
linkage at different positions during a cycle of movement.
[0022] FIG. 3 illustrates a two dimensional (2-D) diagram of a
four-bar mechanism paired with a sliding crank mechanism.
[0023] FIG. 4 illustrates a perspective view of the leg press
exercise apparatus including a spring-loaded knob and pin detent
mechanism which allows the user to adjust the sliding member over a
range of positions in an exemplary embodiment.
[0024] FIG. 5 illustrates a side elevation view of the leg press
exercise apparatus including a spring-loaded knob and pin detent
mechanism which allows the user to adjust the sliding member over a
range of positions in an exemplary embodiment.
[0025] FIG. 6 illustrates a perspective view of the leg press
exercise apparatus including a two-position chair in a raised
position in an exemplary embodiment.
[0026] FIG. 7 illustrates a side elevation view of the leg press
exercise apparatus including a two-position chair in a raised
position in an exemplary embodiment.
[0027] FIG. 8 illustrates the starting position of the leg press
exercise apparatus with the spring at a resting position in an
exemplary embodiment.
[0028] FIG. 9 illustrates the end position of the leg press
exercise apparatus with the spring fully compressed in an exemplary
embodiment.
[0029] FIG. 10A illustrates a kinematic diagram of the leg press
exercise apparatus in an exemplary embodiment.
[0030] FIG. 10B is a schematic diagram showing the parameters
applied to the leg press exercise apparatus in an exemplary
embodiment.
[0031] FIG. 11 illustrates attachment of the leg press exercise
apparatus to a trolley system for transport into the LBNP Box in an
exemplary embodiment.
[0032] FIG. 12 illustrates the leg press exercise apparatus
positioned inside a LBNP Box using the trolley system in an
exemplary embodiment.
[0033] FIG. 13 illustrates perspective view of an upright device to
support the leg press exercise apparatus in a vertical position in
an exemplary embodiment.
[0034] FIG. 14 illustrates integration of the leg press exercise
apparatus and the upright device in an exemplary embodiment.
[0035] FIG. 15 illustrates a resistance profile for the LBNP leg
press apparatus assuming a positive and negative constant angular
acceleration of the foot pedal separated by a period of constant
velocity.
[0036] FIG. 16 illustrates a resistance profile for the LBNP leg
press apparatus assuming a positive and negative constant angular
acceleration of the foot pedal and not having a period of constant
velocity.
[0037] FIG. 17 illustrates results from an electrogoniometer test
with the user in the supine position.
[0038] FIG. 18 illustrates variations in the user's force as the
spring preload increases through a change in dimension l.sub.o.
[0039] FIG. 19 shows a representative LBNP Box for use in
combination with the exercise machine according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The following detailed description is provided as an
enabling teaching of embodiments of the invention. Those skilled in
the relevant art will recognize that many changes can be made to
the embodiments described, while still obtaining the beneficial
results. It will also be apparent that some of the desired benefits
of the embodiments described can be obtained by selecting some of
the features of the embodiments without utilizing other features.
Accordingly, those who work in the art will recognize that many
modifications and adaptations to the embodiments described are
possible and may even be desirable in certain circumstances. Thus,
the following description is provided as illustrative of the
principles of the invention and not in limitation thereof, since
the scope of the invention is defined by the claims.
[0041] In an exemplary embodiment, the leg press exercise apparatus
serves as a portable, lightweight, and effective exercise system
that can be paired with an existing environmentally controlled LBNP
Box 30 to form a LBNP leg press exercise apparatus as shown in FIG.
1A. In this illustration, the legs of the user are simulated by
links 40. Tubes 42, 44 represent cooling ducts. Four-bar linkage 20
movement is controlled by foot pedals 22. The LBNP leg press
exercise apparatus stresses the user's lower extremities to
counteract the effects of microgravity induced syndrome. FIGS. 1B
and 1C illustrate perspective and side elevation views,
respectively, of the leg press exercise apparatus including the leg
simulation links 40 with the leg press exercise apparatus
positioned outside the LBNP Box.
[0042] FIGS. 2A-2B illustrate perspective views of an embodiment of
the leg press exercise apparatus 10 with the four-bar linkage 20 at
different positions during a cycle of movement. The leg press
exercise apparatus 10 includes a four-bar linkage 20, with a first
pair of spaced-apart bars 19 and a second pair of spaced-apart bars
21, rectangular frame 28, foot pedals with strain gages 22, a coil
spring and damper mechanism 16 and 17 for each respective pair of
spaced apart bars 19 and 21, and an adjustable seat or chair 12.
Each pair of bars 19 and 21 in the four-bar linkage 20 is pivotally
attached at respective ends 23 and 25 at corresponding pivot points
27 on opposite sides 29 and 31 of adjustable sliding frame member
24. Each coil spring and damper mechanism 16 and 17 (the latter
shown in phantom in FIG. 2A) is respectively attached at one end 9
and 11 to bars 19 and 21 by ground pivots 13 and 15, and at each
respective second end 5 and 7 to the corresponding side 29 and 31
of adjustable sliding frame member 24. An upper end 1 and 3 of each
respective pair of bars is attached to a support bracket 30 on
which a foot pedal 22 is mounted. The sliding frame member 24 is
mounted on the rectangular base frame 28 with its position
adjustable relative to the rectangular frame 28 by a knob and pin
detent mechanism 26. In some embodiments, a linear actuator can be
included in the leg press exercise apparatus 10 as described below.
The location of the linear actuator (not shown) is indicated by
reference number 14.
[0043] Four-Bar Linkage in Conjunction with Coil Spring and Damper
System
[0044] 1. Kinematics
[0045] FIG. 3 illustrates a two dimensional diagram of a four-bar
parallelogram linkage 60 paired with a sliding crank mechanism 66
representing kinematics of the four-bar linkage and coil spring and
damper mechanisms. The sliding crank 66 is a spring and damping
system that provides a variable resistance. As shown in FIG. 3, if
a force (F.sub.user) 62 is applied by the user to the foot pedal,
the parallelogram linkage 60 will guide the foot pedal along a
circular-arc path at a fixed angle relative to the frame 68. This
maintains a generally perpendicular relationship between the lower
leg and the foot. Applying forces in this manner to the
musculoskeletal system is believed to be one of the most efficient
ways to counteract osteoporosis according to the National
Osteoporosis Foundation.
[0046] With further reference to FIGS. 2A-2B, in order to
accommodate a wide range of potential users, the location of the
pedal system 22 is adjustable relative to the seat 12 location.
This is accomplished through the use of a sliding member 24 that
allows the user to adjust the position of the device 10 along the
rectangular base frame 28.
[0047] FIGS. 4-5 illustrate perspective and side elevation views,
respectively, of the leg press exercise apparatus 10 in an
exemplary embodiment. As shown in FIGS. 4-5, the sliding member 24
is easily adjusted over a range of positions (e.g., 14 cm in one
embodiment) by a spring-loaded knob and pin detent system 26.
[0048] FIGS. 6-7 illustrate a perspective and side elevation views,
respectively, of the leg press exercise apparatus including a
two-position chair in a raised position in an exemplary embodiment.
The two-position chair 12 has frame members 11 and 13. Chair frame
member 11 folds under the bottom side of frame chair member 13 to
position the chair 12 for exercise. The raised position shown in
FIGS. 5-6 enable the user to sit on frame member 11 until the user
is ready to exercise.
[0049] 2. Resistance
[0050] The coil spring and damper system 16, acting as the
prismatic joint in a slider-crank mechanism, provides the
resistance for the leg press exercise apparatus 10. Using this
force-generating slider-crank system in conjunction with the
four-bar linkage 20 creates a nearly optimal resistance curve that
approximates the strength curve of the user through the range of
motion. This creates the high forces and stresses needed to
maintain bone density and optimize the cardiovascular workout. FIG.
8 illustrates the starting position of the leg press apparatus 10
with the spring at a resting position. FIG. 9 illustrates the end
position of the leg press exercise apparatus 10 with the spring
fully compressed. The slider-crank mechanism compresses the linear
spring, creating an increasing resistance throughout the movement
and causing the largest load to be applied when the user's leg is
fully extended. This trend in the resistance provides the desired
optimized profile in relation to the human strength curve.
[0051] The leg press exercise apparatus has been optimized to
produce desirable force and motion properties using classical
techniques in kinematics. FIG. 10A illustrates a kinematic diagram
for an exemplary embodiment of the leg press mechanism. The loop
closure equation (Eq. 1) and velocity loop equation (Eq. 2),
described below, yield the position, s, and velocity, s-dot, of the
slider crank mechanism given the input position, 0, and velocity,
O-dot. Static resistance is dependent only on the value of 0, which
determines the compression of the spring and the geometry of the
device. Dynamic resistance depends on the user's motion profile
(O-dot). Assumed user motion profiles and their effect on dynamic
resistance are discussed below. Once the position and velocity loop
equations have been solved, virtual work can be used to find the
resistive force, F.sub.user, as a function of position, 0, from Eq.
3. The inertial term in Eq. 3, I*{umlaut over (.theta.)}{dot over
(.theta.)} is based on a position-dependent equivalent inertia
approach known in the art. The motion of the user is expected to be
slow, therefore, dynamic effects, including the force of the
damper, are expected to be small. The damper is incorporated to
prevent rapid movement in the event that the user's foot slips off
the pedal. The damper also helps to discourage high-speed exercise
motion.
l.sub.o -l.sub.1-l.sub.2e.sup.j.theta.-se.sup.j.gamma.=0 (1)
l.sub.2{dot over (.theta.)}e.sup.j.theta.-{dot over
(s)}e.sup.j.gamma.- s{dot over (.gamma.)}e.sup.j.gamma.=0 (2)
I*{umlaut over (.theta.)}{dot over (.theta.)}+F.sub.user{dot over
(.theta.)}l.sub.3+F.sub.spring{dot over
(.theta.)}l.sub.3+F.sub.spring{dot over (s)}=0 (3)
[0052] FIG. 10B is a schematic diagram showing the parameters
applied to the leg press exercise apparatus in an exemplary
embodiment, with representative values shown in the following 2
tables.
TABLE-US-00001 TABLE 1 Specifications Height Width Depth Mass
Moment of Link (in) (in) (in) (lbs) Inertia l.sub.2 2.48 2.06 1.97
0.87 3.13 l.sub.3 16.50 2.06 1.97 13.2 1727.93 l.sub.4 16.50 2.06
1.97 13.2 1727.93 Sum of MOI 3459 (kg*sq. in)
TABLE-US-00002 TABLE 2 Spring properties Stroke length (in) 3 Eye
to eye length (in) 12.51 Spring rate (k) 650
[0053] Resistance Due to Inertial Forces
[0054] The user must overcome the static spring forces, the damping
forces, and the inertia forces generated by acceleration of the
links of the exercise device. Inertia forces are incorporated in
Eq. 3 by calculating an equivalent inertia of the system, I*, that
varies with position. Eq. 4 shows how such an equivalent inertia is
determined.
1/2I*=.SIGMA..sub.i=1.sup.n1/2m.sub.i({dot over
(x)}.sub.i.sup.2+{dot over (y)}.sub.i.sup.2)+1/2I.sub.l{dot over
(.theta.)}.sub.l.sup.2 (4)
Eq. 4 takes into account the mass (m) and inertia (I) of every
moving link in the mechanism. While all links contribute to the
total user force, the mass of the foot pedal is of special concern.
Because the foot pedal is at the extreme end of link l.sub.3, it
has the largest peak velocities and accelerations. The foot pedal
is also the most massive element in the leg press exercise
apparatus. One goal in designing the leg press exercise apparatus
is to minimize inertial forces. This enables shaping the static
resistance curve through kinematics to be as similar to the human
strength curve as possible. Dynamic forces will change the shape of
this curve as a function of how rapidly the user moves the foot
pedal. Further analysis will show that the dynamic forces can be
kept small.
[0055] In another embodiment, to further accommodate users of
different strengths, an additional adjustment can be included in
the leg press exercise apparatus. This additional feature
personalizes the device by changing the initial preload in the
spring along with the displacement curve. The geometry of the
slider-crank mechanism can be changed by lowering the ground pivot
on the right side of the mechanism as shown in FIG. 10. Lowering
this pivot (i.e., changing the value of l.sub.0) generally causes a
vertical shift in the resistance curve.
[0056] During testing, the largest single-leg forces during
resistance exercise were 1.16 BW (232 lbs) during supine position
when .gamma., the angle between the horizontal and the ground pivot
on the right side of the apparatus, equals 187 degrees and the
minimal leg force was at 0.68 BW (136 lbs) when .gamma. equals 177
degrees. The leg press exercise apparatus was able to elicit loads
comparable to exercise on Earth since the forces were greater than
1 BW. When paired with LBNP, the maximum resistance load could be
as low as 196 lbf when the LBNP is set for the recommended 50 mm Hg
to achieve a maximum of 2 BW.
[0057] In a further embodiment, a linear actuator can be
incorporated into the leg press exercise device to control the
position of the ground pivot. The adjustment will occur
automatically based on the user's heart rate (HR). The user will be
required to keep a steady target heart rate that will be
determined, using Eq. 5, before testing and monitored throughout
the workout. The spring can be changed manually with the use of
quick release pins.
HR.sub.target=((HR.sub.max-HR.sub.rest)*%.sub.intensity)+HR.sub.rest
(5)
[0058] 3. Biomechanics
[0059] Ground reaction forces (GRF) are created by static and
dynamic loading. The forces experienced in 1G are due to the user's
weight (static) and the dynamic loading is due to movement. To
simulate forces equivalent to those experienced in 1G, the ground
reaction force must be equal to or greater than 1 BW. As indicated
in Eq. 6, the GRF are directly related to the pressure differential
force and the total user force applied to move the foot pedal. It
should be noted that the vacuum feature of the LBNP box was not
used during preliminary testing.
GRF=(Pressure Differential Force)+(Total User Force) (6)
[0060] Eq. 6 states that the pressure differential force (the
product of the body cross-sectional area multiplied by the pressure
differential across the LBNP Box, which will be assumed to equal 50
mm Hg) plus the total user force (the inertial forces caused by
geometry and the force required to overcome the resistance of the
coil spring and damper system) equals the ground reaction force.
The total user's force includes the inertial forces caused by the
leg press exercise apparatus and the force required to overcome the
resistance of the coil spring and damper system.
Two Member Chair Serves as Daily Activity
[0061] The posterior side of the lower extremities are accustomed
to 2/3 BW between six and eight hours a day. The chair simulates
this daily activity of sitting by translating a fixed linear force
to the active areas. The force applied is simulated from the
negative pressure in the LBNP Box.
[0062] As indicated in Eq. 7, if the user is sitting or remains
static, the total user force term in Eq. 6 equals zero. The GRF
then becomes:
GRF=Pressure Differential Force=Axy*.DELTA.P (7)
[0063] The chair is adjustable in both angle and linear distance by
the use of quick release pins and a sliding member. The chair can
be folded easily and has a resting position horizontal to the
center bar. The chair can be cushioned by foam and covered with
leather allowing the user to both exercise and sit comfortably.
Integration of Leg Press Exercise Apparatus with LBNP Box
[0064] The leg press exercise apparatus can be manufactured to be
removable, without disassembly, from the LBNP inner structure. The
leg press exercise apparatus can be attached to a trolley system,
as shown in FIG. 11, making the apparatus maneuverable and easily
accessible which allows the user to adjust his personal settings
outside of the LBNP Box. The parallel arms and seat collapse
horizontally to the center bar allowing the removal process to be
quick, easy, and safe. FIG. 12 illustrates the leg press exercise
apparatus positioned inside the LBNP Box through use of the trolley
system.
Integration of the Leg Press Exercise Apparatus and the Upright
Device
[0065] FIG. 13 illustrates a perspective view of an upright device
for supporting the leg press exercise apparatus in a vertical
position. FIG. 14 illustrates integration of the leg press exercise
apparatus and the upright device in an exemplary embodiment.
[0066] The physiological and biomechanical responses of each user
can be recorded in both the supine and upright position in order to
collect comparative data. In the upright position, there will be no
added negative pressure or suction force, only the effects of
gravity. Data collected in the upright position can be compared to
similar data in the supine position. If the LBNP is effective, user
forces, heart rate, and expended energy should be comparable
between the two configurations.
Resistance Profile
[0067] It is well known that the human body is a highly nonlinear
mechanical device from the standpoint of generating forces over a
given cycle of motion. The leg press provides a good example of
this. A plot of the maximum force a user can produce at each point
in the outward cycle of a leg press would show, not surprisingly,
that the user is able to generate far more force at the extreme
position (when the knee joint is at full extension) than when the
knee is sharply bent. Mechanical work and physiology stress in the
muscles will be nearly optimized when the resistance provided by a
leg press exercise machine most nearly matches this strength curve.
Stated simply, the resistance curve should match the human strength
curve for optimal efficiency in strengthening muscle and stressing
bone. Although the strength curve varies from user to user as does
the resistance curve, the general shape of the curves is
approximately maintained. The leg press exercise apparatus
approximately matches the resistance provided by the apparatus with
the human strength curve in a leg press exercise. An adjustment
could be provided to raise and lower the magnitude of resistance
while keeping the general shape of the curve. The slider-crank
mechanism used in the leg press exercise apparatus creates an
excellent approximation to the human strength curve when
considering only the resistance of the spring. By limiting dynamic
forces, the overall apparatus exhibits an excellent resistance
curve under typical operating conditions.
[0068] The theoretical resistance provided by the leg press
exercise apparatus can be calculated under a set of assumed
conditions. The analysis uses the actual link masses and inertias
from the apparatus. The most important assumption necessary to
perform a complete analysis is the user's motion profile. Since the
foot petals reciprocate, their angular velocity will be zero at the
beginning and end of each stroke. Velocity should ramp up to a peak
somewhere between these endpoints, but there is no way to precisely
predict how the user will accelerate and decelerate. Results from
testing indicate that a typical user moves at about one cycle of
motion per second. Two different motion profiles were used to
calculate the inertia and user force. The first profile used
constant angular acceleration of the foot pedal link to start and
end the motion cycle and a period of constant velocity in between.
The second motion profile was similar, but had no period of
constant velocity motion separating the periods of positive and
negative constant acceleration. The results of these two analyses
are shown in FIG. 15 and FIG. 16, respectively. In both figures,
the user force curve shows the user force on the foot pedal due to
the resistance of the spring, the inertia curve shows the user
force on the pedal due to dynamic effects, and the superposition
curve is the net user force on the pedal through a 0.5 second
stroke.
[0069] In one test of the multi-user device, an electrogoniometer
was applied to the subject's left knee, centered directly over the
rotational joint. FIG. 17 illustrates the results from the
electrogoniometer test when the use is in the supine position. The
electrogoniometer limits were calibrated for 0.degree. when the
user's knee was straight, the top limit equaled 200 volts, and for
90.degree., when the user's knee was bent, the lower limit equaled
zero volts. The vertical line in FIG. 17 indicates a maximum
voltage of 141.5 volts at roughly 90 degrees. This curve indicates
that the user is generally accelerating or decelerating the foot
pedal, with little or no constant velocity in the middle.
[0070] The analysis also considered the effect of varying the
spring preload and the effect of the LBNP Box pressure difference
on the foot pedal forces exerted by the user. The graphs in FIG. 18
show the variation in user foot pedal force as the spring preload
increases through a change in the adjustable dimension l.sub.0. The
top curve used a dimension l.sub.0=0.38. The middle curve used a
dimension l.sub.0=1.38. The bottom curve used a dimension
l.sub.o=2.0.
[0071] Exercising in space is the most effective known method of
counteracting the deleterious effects of living for prolonged
periods in low gravity conditions. However, even with rigorous
exercise, astronauts typically lose 0.4-1.0% of their bone density
per month in space. Although astronauts gradually recover their
muscle tissue and most of their bone mass when they return to
Earth, it is important that they are strong enough to perform
emergency procedures during landing. Coupling appropriate
resistance exercise with a Lower Body Negative Pressure (LBNP) Box
will improve on the current state of the art in preventing
deconditioning and bone loss.
[0072] The leg press exercise apparatus was designed to fit within
an existing LBNP Box, which placed significant constraints on its
dimensions and operation. This caused the length requirement for
the subject's lower extremities, waist to sole of foot, to range
from 70 cm to 82 cm. A linear actuator in another embodiment would
change the level of resistance based directly off the subject's
heart rate.
[0073] After testing the embodiment illustrated in FIGS. 4-5, it
was found that the angle of the foot pedal is preferably adjusted
so that the user's foot maintains an angle closer to 90.degree.
throughout the entire cycle rather than just toward the beginning
and the end of the stroke. If too much of the force from the
subject's foot is directed along the link, user forces will be
somewhat higher than desired for the first half of the pedal
stroke.
[0074] Overall, the combination of the multi-platform and the LBNP
Box provides the advantage of minimizing deconditioning in a safe,
compact, lightweight and efficient way for space travelers to
exercise. The leg press exercise apparatus can also incorporate
automated adjustments and feedback control to maintain the user's
heart rate while providing near optimal resistance curves.
[0075] An LBNP Box 30 is described in T. Russomano et al.,
"Development of a lower body negative pressure box with an
environmental control system for physiological studies", Advances
in Space Research 38, 6; 1233-1239 (2005), as follows. Referring
now to FIG. 19, LBNP box 30, a tube structure designed to
accommodate the lower body portion of a subject, consists of five
carbon steel ribs in the shape of a cylinder that is covered by
high pressure resistant and transparent vinyl. The front and foot
plates are fabricated of carbon steel. The pressure and flow system
consists of two valves--an inlet and an outlet valve--that connect
the external to the internal environment of the chamber--and a set
of tubes mounted within the chamber. The valves are affixed to the
foot-plate of the box with the set of tubes connected to them as
shown. The level of negative pressure inside the box is primarily
controlled via the outlet valve, specifically a threeway valve
having one end connected to a vacuum pump to create the negative
pressure, another end connected to the interior of the chamber
through a pipe, and the third end connected to the external
environment. The required negative pressure inside the LBNP box is
obtained by mixing air drawn from the LBNP box with atmospheric
air. The connection to the external environment can be opened and
closed by a stepper motor, varying the negative pressure in the
LBNP box. Airflow control is achieved through the inlet valve,
which also connects the external to the LBNP box environment and is
opened or closed by another independent stepper motor. Both the
inlet and the outlet valves are connected to tubes that allow a
uniform distribution of air in the chamber. The inlet valve is
connected by two parallel tubes placed along the chamber to a third
tube placed in the front plate that has five holes symmetrically
displaced along it. On the foot plate, connected to the outlet
valve, there is a similar tube, also with five holes. The tubes are
located in the upper part of the box, above the surface on which
the subjects lie. The LBNP box 30 further includes at the upper
part of the box a seal configured to fit proximate to and snuggly
around the waist of the subject so that the vacuum applied to the
device produces a lower relative pressure on the user's lower body
when positioned inside the box. The negative pressure is therefore
maintained with the subject's lower body positioned inside the box
while using the exercise machine of the invention.
[0076] The corresponding structures, materials, acts, and
equivalents of all means plus function elements in any claims below
are intended to include any structure, material, or acts for
performing the function in combination with other claim elements as
specifically claimed.
[0077] Those skilled in the art will appreciate that many
modifications to the exemplary embodiments are possible without
departing from the scope of the present invention. In addition, it
is possible to use some of the features of the embodiments
disclosed without the corresponding use of the other features.
Accordingly, the foregoing description of the exemplary embodiments
is provided for the purpose of illustrating the principles of the
invention, and not in limitation thereof, since the scope of the
invention is defined solely by the appended claims.
* * * * *