The present invention generally relates to exercise apparatus and physical therapy machines and, more particularly, to apparatus for physical therapy and exercise in regard to human ambulatory gait.
In the course of a lifetime, a significant number of persons will suffer serious physical injuries and medical incidents and conditions which may be survivable and allow a degree of recovery but, nevertheless, leave a more or less intractable degree of impairment of some capabilities. Some injuries to the head and physical incidents such as stroke which cause some loss of some brain and/or spinal cord function are particularly serious and often result in disabilities or physical impairments which compromise or even preclude some activities which are extremely important and substantially essential to what is considered to be a reasonably normal and independently functional life style in a community.
Stroke is one of the leading causes of disability in the United States with roughly 750,000 individuals being affected each year. The yearly cost of stroke is estimated at nearly 30 billion dollars in direct medical costs and nearly 20 billion dollars is lost productivity. Many people who survive stroke are left with severe and persistent disabilities. Among these persistent conditions is hemiparesis, a weakness on one side of the body, which can impair the ability to walk. While the majority of stroke survivors will regain some limited ability to walk, 40% will require assistance with walking and, of those who eventually become independent, 60% will still achieve only limited community ambulation. Fewer than 20% of stroke victims will achieve unlimited community ambulation.
In a recent study, over 90% of stroke victims considered the ability to walk sufficiently to participate in the community to be important and 40% considered that capability to be essential. Therefore restoration of a walking gait is a major goal of rehabilitation of victims of stroke and accidents having similar hemiparetic effects.
Walking or gait is a person's natural way of moving from one location to another and is the most efficient way for a person to travel short distances. In a normally functioning person, the lower limbs have the ability to adapt to different surfaces, ground topologies and obstacles such as uneven ground or stairs. Because of the importance of walking, patients will generally strive to retain or regain the ability to walk, notwithstanding severe impairment.
In early human development, many skills involving more or less repetitive movements of limbs or coordination among muscle groups, such as speech and ambulation which are necessary to functioning in a community, are learned to the point of being almost reflexive in nature. Many more involving movement and/or coordination such as riding a bicycle, skating, sports skills and performing on musical instruments can also be learned to a similar degree. Such learning is sometimes colloquially referred to as “muscle memory”. When a person having learned such skills suffers a stroke or injury causing hemiparesis, the muscles on one side of the body do not respond normally and impair the performance of such skills. Moreover, muscles on the impaired side of the body and the ability to control them may degenerate or atrophy from substantial disuse over a period of time and further impede recovery and the regaining of such skills.
It is well-established that repetitive movement against resistance can result in improved muscle tone and produce muscle growth as well as improve cardiovascular fitness even in persons of relatively advanced age. Movement against a weight is a classical form of such exercise. In recent years, many more or less sophisticated devices have been designed and built which not only provide such resistance in an easily controllable manner with reduced likelihood of injury but also allow some isolation of particular muscle groups during particular repetitive motions. Other types of exercise apparatus have also been developed to simulate some normal activities involving repetitive motion against resistance more or less closely. However, for normal persons, the degree of simulation of a normal activity is more important for the larger muscle groups to increase the exercise value of the repetitive motion against resistance than for the smaller muscle groups that would be important to the productive value of the activity that is being simulated. That is, some particulars of a complex repetitive motion being simulated may be altered in the interest of simplicity and/or robustness of the exercise apparatus or to place parts of the body at a relative mechanical disadvantage or to isolate particular muscle groups in order to maximize the exercise value of the motion but may be counterproductive in regard to the practice of activity, itself. In other words, use of exercise apparatus for development of the muscles involved in an activity does not necessarily improve the practice of the activity, itself, by the user of the exercise apparatus. Therefore, use of known commercially available exercise machines, while generally effective for obtaining maximal exercise value from their use, are of substantially reduced value in achieving rehabilitation of stroke or injury victims.
It is therefore an object of the present invention to provide an apparatus which closely replicates motions of a normal person performing a skill such as walking which can be used by a person suffering hemiparesis to guide movement of portions of the body in order to regain muscle tone and coordination for practice of basic skills.
It is another object of the invention to provide an apparatus for re-training of basic movement skills in which ankle angle movement patterns can be readily and easily altered and which can be manufactured by inexpensive modification of relatively inexpensive commercially available exercise equipment.
In order to accomplish these and other objects of the invention, an apparatus is provided comprising in combination a mechanism for moving and extremity of a limb along a substantially elliptical locus, a sensor for determining locations of a portion of the mechanism along the substantially elliptical locus, and an actuator for guiding a position of said extremity that simulates a repetitive motion of said limb corresponding to respective positions along said substantially elliptical locus.
In accordance with another aspect of the invention, a robotic module for attachment to an exercise apparatus is provided comprising a sensor for determining locations of a extremity of a person along a substantially elliptical locus, and an actuator for guiding a position of the extremity that simulates a repetitive motion of a limb corresponding to respective positions along said substantially elliptical locus.
In accordance with a further aspect of the invention, a method of providing physical therapy using an exercise apparatus is provided comprising steps of guiding an extremity of a human body along a locus of substantially elliptical repetitive motion with the exercise apparatus and guiding angular position of the extremity in accordance with a position of said extremity along the locus of substantially elliptical repetitive motion.
The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which:
Referring now to the drawings, and more particularly to
The first sequence depicts normal walking on a level surface. The second sequence depicts a walking motion executed on a commercially available Nordic Trak™ CXT 910 elliptical trainer apparatus. Elliptical trainer apparati are types of device which cause the load-bearing extremity of the user to follow a generally elliptical path simulating a repetitive motion of a normal and common activity such as walking. The generally elliptical path of, for example, the right foot of the subject in these sequences of photographs, captured with a video camera, can be observed in both sequences of photographs.
The individual photographs in each sequence correspond to the respective photograph in the other sequence and correspond to identifiable points within a gait cycle which are of particular interest, as will be discussed below and are not necessarily equally separated in time as will also be further discussed below. These points in time are, from left to right:
1.) the loading response (when body weight is shift to a particular foot),
2.) early mid-stance) when body weight is directly over one foot),
3.) terminal stance (when body weight is about to be removed from that foot but the foot remains fully in contact with the supporting surface),
4.) pre-swing (as weight is removed from that foot to be transferred to the other foot as the heel of the foot is lifted and the body is thrust forward by the grip of the toes),
5.) initial swing (as the foot begins to move forward),
6.) mid-swing as the lifted foot passes the other, load-bearing foot, and
7.) terminal swing (at the moment of heel contact prior to shifting of weight when the loading response point in the gait is repeated at the beginning of the next gait cycle).
It should be noted that these points in time are identified for each foot of the subject and the particular identified point in the gait cycle for one foot will correspond to another identified point in the gait cycle for the other foot. For example, the loading response point in the gait sequence for the right foot will correspond to the pre-swing point in the gait cycle for the left foot. It should also be understood that, while the respective photographs in each sequence correspond to each other, they do not necessarily correspond to the same points in time as a percentage of a gait cycle.
It can be seen from the photographic sequences of
The angle of the foot with respect to the horizontal direction in the sagittal plane is graphically plotted as a function of a percentage of a single gait cycle in
Referring now to
While not important to the invention, the elliptical trainer illustrated in
The development of an elliptical motion can be readily seen from
It should be appreciated that the bottom half of a highly eccentric ellipse when the major axis of the ellipse is brought near horizontal through use of a small angle of inclination of the ramp 16 and allowing for some flexure of the leaf spring of the lever arm 14 under loading from the weight of the user, is relatively flat and thus closely approximates the loading response, stance and preswing phases of a gait cycle while the upper half of the ellipse closely approximates the locus with respect to the body through which the foot travels during the swing phases of a gait cycle. This geometry has the effect of dividing the gait cycle substantially evenly with the stance and swing phases each comprising about 50% of the gait cycle. In normal walking, however, the stance phases comprise about 60% of the gait cycle while the swing phases are somewhat shortened to about 40% of the gait cycle. While some commercially available therapy apparatus has attempted to increase fidelity of movement to the unequal durations of the stance and swing phases of the gait cycle through complex differential gearing arrangements and/or electronic controls (adding substantial cost and weight to the apparatus) it appears to the inventors that this discrepancy between the elliptical trainer motion and normal walking is of little, if any, importance to effectiveness of therapy and that, once sufficient coordination and muscle strength have been regained, the body will reflexively shorten the swing phase of normal walking in order to increase the duration that both feet are in contact with the surface being traversed and to more readily maintain balance.
In contrast, it should be noted that the crank positions 12a-12d do not correspond to the either extreme top, bottom front and back of the elliptical locus or the extremes of inclination of the lever arm 14. Thus there is an unavoidable phase discrepancy between the cyclic foot position and ankle angle established by the elliptical trainer apparatus and the foot position and ankle angle (referred to a horizontal direction) that is established by contact of the foot or a portion thereof and a level surface. As alluded to above, this phase discrepancy can be clearly observed from curves 32 and 34 of
Since this phase discrepancy is substantially inherent in the geometry of elliptical training apparatus, the foot/ankle angle must be decoupled from the apparatus which produces the elliptical movement that causes the desirable shin, knee, thigh and hip to move in a manner which closely mimics movements of walking on a level surface. Accordingly, the invention provides for the footplate 18 to be pivoted from a member 40 that is raised from the lever arm 16 as shown in
As a further incident of design, it is considered that a stroke victim would probably undergo a prolonged period of substantial immobility prior to being able to undergo therapy using the invention and therefore may be of greater than normal body weight, assumed to be 250 pounds for purposes of a practical design of an embodiment of the invention. Since substantially the entire body weight of a user must be carried by each footplate as the user shifts body weight between footplates in the course of a walking gait and may be applied to the footplate through the ball of the foot and the toes, it is considered that such a structure should be able to carry full body weight at a point about six inches away from the desired ankle location relative to the footplate 18 which, in turn, should be substantially aligned with the pivot location 42. Therefore, the arrangement of
The maximum speed of rotation of footplate 18 around pivot point 42 corresponds to the slope of profile 32 of
Accordingly, the preferred embodiment of the invention is shown in
The preferred embodiment of the invention comprises a body 50, preferably in the form of a beam with downwardly extending flanges, presenting a flat upper surface and having a width somewhat in excess of the width of the arcuate lever arm 14 such that the beam flanges extend along the sides of the lever arm in order to laterally position body 50 thereon. A pair of downwardly extending brackets 51 are provided, preferably as extensions of the flanges of the beam to engage crank 12. The brackets 51 are positioned such that the beam will be tangent to the arcuate lever arm 14 at the location of member 40 providing a raised pivot point 42 for footplate 18. Thus lever arm directly supports the footplate through member 40 and body 50, providing extremely stable support for a user.
The flat upper surface of body 50 is preferably covered with a vibration absorbing (preferably rubber) material layer 52 to limit conduction of vibration from an actuator such as gear box 54 and motor 56 either directly or through motor mount 57. As will be discussed in greater detail below, motor 56 is preferably a servo motor, although a stepping motor of possibly other types of actuators could theoretically be used. A servo motor can produce substantially greater torque than a stepping motor of comparable weight, generates less rotational vibration and is somewhat more easily controlled. Thus a servo motor is preferred for practice of the invention. The gear box 54 preferably houses a worm gear meshed with a sector of a pinion gear. The preferred gear ratio is 60:1 which is effectively self-locking when not being driven by the servo motor and can operate with zero backlash through preloading. The high gear ratio also provides for multiplication of servo motor torque to drive control arm 55, pushrod 46 and control arm 44 which alters the angle of footplate 18. A ball bearing 58 is preferably provided for the pivot bearing of the footplate, again to avoid vibration and, importantly, any lost motion or free play in the pivot joint that would compromise stability of the footplate.
Referring now to
The position indicated by position counter 65 can then be translated to an ankle angle by any of a number of types of device such as a look-up table, a microprocessor performing a computation in accordance with an algorithm or even an optical reader that simply follows the edge of a structure shaped in accordance with the desired ankle angle profile (e.g. 36 in
For example, it may be desirable to exaggerate or under-correct ankle movements during particular phases of therapy. For example, stroke can cause upper neuron lesions in some patients which compromises inhibitory muscle controls; causing the patient to over-react in an opposing direction when a limb is moved or a joint flexed. Under-correction during early therapy seems to allow the body responses to be “coaxed” back to normal function. Conversely, exaggeration of motion is likely to be chosen with other stroke patients or patients with other maladies such as diabetic neuropathy where an exaggerated motion may be required to be learned to prevent dragging of the toes during the swing phase of a walking gait.
Once the flywheel position is translated to a chosen ankle angle corresponding to the particular position within the gait cycle, the servo motor 56 can be suitably energized in a manner well-understood in the art to rotate through an angle that drive the gears in gear box 54, depicted as the preferred worm and pinion sector gears as alluded to above. The rotational motion of the servo motor is reduced (and the torque correspondingly increased) by the preferably high gear ratio such that control arm 53 and pushrod 46, a portion of which is schematically depicted as a dashed line in
It should also be appreciated that, in contrast with other currently available apparatus for performing similar therapy that are entirely motor driven, the invention is entirely propelled by the user except for the servo motor for following the desired ankle angle profile. The invention thus provides a robotic device which follows a motion of the user (e.g. in pressing on the footplates 18) with a corresponding, different movement. Therefore, the invention can operate at any pace the user adopts and provides enhancement of both the exercise and therapeutic benefits of use. Perhaps more importantly, the propulsion of the invention principally by the user is believed to enhance therapy since control of forces produced by a non-parietal limb appear to force embedding of a movement pattern in the complementary impaired parietal limb The invention can also operate in a reverse direction of the flywheel and thus can simulate walking backwards which is also believed to be of substantial therapeutic and exercise value.
As perfecting features of the invention which are not necessary to the practice of the invention in accordance with its basic principles but which are desirable in a therapeutic environment where a user may continue therapy substantially unattended, a brake or locking mechanism 70 that can be electrically actuated by switch 74 through connection 72 can be employed at any point in the mechanical linkage discussed above, such as at flywheel 11, to allow the user to quickly halt operation if desired or in the event of loss of balance or proper positioning on the apparatus such as disengagement of a foot from a footplate 18. Since foot/ankle angle change is determined by flywheel motion, when the flywheel (or other part of the mechanism) is stopped, the elliptical footplate motion is also stopped and the footplate is essentially locked in angular position by the mechanical advantage provided by the worm and sector/pinion gears, as alluded to above. It is also desirable to provide for suspension of the user to the extent of at least a small portion of body weight with a harness that will carry the entire body weight of the user if the user begins to fall from the apparatus. Such a harness is also useful for therapists in initially positioning a non-ambulatory patient in the correct position on the apparatus.
In view of the foregoing, it is clearly seen that the invention provides an inexpensive and low weight apparatus for providing enhanced therapy for victims of stoke and other maladies which have impaired muscle control to the point of compromising the ability to walk. Any desired profile of ankle angle over the course of a gait movement can be accommodated to provide enhanced therapeutic treatment as the condition of the user may require. Cost and weight may be minimized by constructing the invention by modification of a commercially available exercise apparatus by the simple installation of a modular device as shown in
While the invention has been described in terms of a single preferred embodiment, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.
This application claims benefit of priority of U.S. Provisional Patent Application 61/478,981, filed Apr. 26, 2011, which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
---|---|---|---|
61478981 | Apr 2011 | US |