Abstract:
Systems and methods are provided to improve the gait performance of subjects with neurodegenerative disease movement disorders, injuries, surgical wounds, athletic performance objectives, or combinations thereof through feedback-enhanced training A subject walks, jogs or runs on a surface with the use of an assistive walking device such as a walker, cane, rollator or railings. Attached to the assistive walking device is a distance sensor and processing unit that detects, measures, and evaluates certain gait characteristics and delivers feedback to the subject. The subject is trained to exhibit desirable gait characteristics such as stride length, heel-toe motion, cadence, pace and the like.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of abandoned U.S. application Ser. No. 11/742,840, filed May 1, 2007, which was a non-provisional claiming priority to U.S. provisional application No. 60/796,582 filed May 1, 2006. The entire disclosures of both applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to improving motor performance in subjects with neurodegenerative conditions, movement disorders, injuries, surgical wounds and athletic performance objectives. 
     BACKGROUND OF THE INVENTION 
     Neurodegenerative diseases, such as Guillain-Barre syndrome, Huntington&#39;s disease and amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS) and Parkinson&#39;s Disease (PD) and injuries caused by stoke, atherosclerosis, traumatic injury from accident, and the like, afflict patients with a reduced ability of movement. Parkinson&#39;s Disease is a progressive neurodegenerative disease that causes affected individuals to move slowly and make small movements. Subjects with Parkinson&#39;s Disease display tremor, rigidity, bradykinesia and postural instability. Without the use of exteroceptive (visual or auditory) input, subjects with PD make hypometric movements (Flowers,  Brain,  99:269-310, 1976, Klockgether &amp; Dichgans,  Mov. Disord.,  9:48-56, 1987) but motor performance improves with auditory or visual cues (Georgiou et al,  Brain,  116:1575-78,1993). 
     The gait in subjects with PD can be described as shuffling, with short hesitant steps that are sometimes quick (festinating). Subjects with PD have difficulty initiating their gait and walk stiffly with limited arm swing. Postural instability is usually a relatively late symptom of the disease and one that is not amenable to current medical or surgical therapy (Koller et al,  Clin. Neuropharmacol,  12:98-105, 1989), although some improvement in balance has been reported with bilateral subthalamic stimulators (Bejjani et al.,  Jour. Neural. Neurosurg. Psych.  68(5):595-600, 2000). Subjects with PD experiencing postural instability are at increased risk of falls resulting in traumatic injuries and are usually dependent on the use of assistive devices such as walkers. In one survey, subjects with PD had a yearly incidence of broken bones of 35.6% of which ⅓ were hip fractures (Pressley et al.,  Neurology,  60(1):87-93, 2003). Following hip fractures, the gait worsens and 21.9% may be fully unable to walk (Gialanella,  Minerva Med.,  92(3):11-6, 2001). In addition, freezing and gait hesitation usually occur relatively late in the disease and can be quite debilitating even when the other symptoms of the disease are well-treated medically. 
     Although subjects with PD are routinely sent for physical therapy to address their gait problems, the efficacy is not well documented. Furthermore, the methods used vary from center to center and have not been subjected to rigorous scientific investigation. Weight-supported treadmill training, a technique in which the subject walks on a treadmill with partial body weight support through an overhead harness as well as a pelvic belt has been found to improve gait stride length and speed in persons with strokes (Miyai et al.,  Arch. Phys. Med. Rehabil.  81:849-52, 2000) and these benefits may be long-lasting (Miyai et al.,  Arch. Phys. Med. Rehabil.,  83:1370-3, 2002). The mechanism for the improvement is unknown. A portion of the improvement with treadmill training in PD may be due to aerobic conditioning since that seems to be a factor when applied to stroke patients (Macko et al.  Stroke,  28:326-330, 1997; Macko et al,  Arch. Phys. Med. Rehab.,  82(7):879-884, 2001). In this training in subjects with PD, the weight support may be a factor (Visintin et al,  Stroke,  29:1122-28, 1998) in the improvement aside from any improvements resulting from more efficient energy expenditure. Frenkel-Toledo et al. ( Movement Disorders  20(9)11109-1114, 2005) suggest that the treadmill itself may be acting as an external cue to enhance the rhythmicity of the gait of the subject with PD, but did not demonstrate any stride length improvements. 
     It is a common observation that subjects with PD may undergo severe “freezing” when attempting to go through doorways but may have little trouble going up stairs or when there is a repeated pattern on the floor. These visual stimuli can have large effects on a subject&#39;s gait. There is a commercially-available cane (STEPOVER WAND®) that employs a red wire as a visual stimulus or a visual aid for subjects experiencing freezing. With this device, subjects are explicitly using visual input to help improve the magnitude of their steps. It is well accepted that visual stimuli may improve gait by alleviating freezing, and in fact, there are improvements in gait in subjects with PD with visual and auditory cueing (Suteerawattananon et al,  J. Neurol. Sci.,  219:63-69, 2004). However, the improvements with auditory cueing (using a metronome) were in cadence rather than stride length (Suteerawattananon et al.,  Ibid,  2004). 
     The use of the term “gait improvement,” as used herein, means the alleviation of freezing and hesitation. 
     The short steps that subjects with PD take are one form of the hypometria they experience, and this is also present during movements of the upper extremities. With visual feedback, subjects are able to make larger limb movements, and the deficit may be due to a sensory-motor mismatch (Demerci et al.  Ann. Neurol.,  41:781-788, 1997). That is, the kinesthetic signal may be “felt” as indicating the subject has made an adequately-sized movement even though he has not. Subjects with PD perceive distances to be shorter than control subjects when they use kinesthesia rather than vision. Subjects with PD often feel they are speaking at a normal volume even though they may be severely hypophonic (Marsden,  Neurology,  32:514-539, 1982), but when they are coerced into speaking louder they feel as if they are shouting (Ramig et al,  J. Med. Speech Lang. Pathol,  2:191-209, 1994). Apparently during both limb movements and speech, subjects with PD have a feeling of performing well and do not attempt to make corrections because they do not feel any discrepancy between their motor intention and performance (motor output) as long as there is no exteroceptive feedback. Based on these ideas, improvements in speech have been achieved (the Lee Silverman Voice Treatment program). The focus is on producing a louder volume and this results in improvements in articulation as well (Ramig,  Intelligibility in Speech Disorders: Theory, Measurement and Management , John Benjamins Pub. Co., R. Kent, ed., Amsterdam, 1992) even though articulation is not stressed during the therapy. These ideas have not been applied to physical therapies for gait. 
     U.S. Pat. No. 6,704,603 B1 and divisional U.S. Publication no. 2004/0133249 A1 describe a method of adaptive stimulation and an adaptive stimulator product. The &#39;603 patent describes a control unit and method to aid in the relief of symptoms of Parkinson&#39;s disease. The device disclosed electrically stimulates a subject&#39;s muscles at a set rhythm to stimulate better movement or uses a signal to tell the subject when to take a step. Stride lengthening is not disclosed. 
     Since subjects with neurodegenerative disease have a greatly increased risk of suffering traumatic injuries as a result of postural instability, intervention with physical therapies and the use of assistive devices, such as canes and walkers, may be helpful in preventing these falls. Various experimental therapy methods including Body Weight Supported Treadmill Training (Miyai et al.,  Ibid,  2000, 2002), and visual and auditory cueing (Suteerawattananon et al,  Ibid,  2004) have demonstrated some improvement in gait parameters. However, there are no standardized physical therapeutic modalities that lead to improvement in gait or postural stability. There is a need in the art for improving the gait stride length, gait shape, and gait pace of a subject, as well as improving general postural stability in subjects with neurodegenerative disease. 
     Subjects recovering from surgeries to the lower body, such as total hip replacement, total knee replacement, arthroscopic surgery and prosthetic device implantation as well as subjects recovering from traumatic injuries often exhibit less-than-ideal gaits. That is, the gait of the patient consists of a short stride length, a flat-footed shuffling motion, an unstable step that wavers laterally from the intended stepping direction or combinations thereof. Current physical therapy applied to subjects recovering from these afflictions includes practice of proper walking form and range-of-motion exercises. However, proper performance of the exercises is only ensured when a physical therapist or attending clinician is present to guide the subject. There is a need for improving the range-of-motion, gait stride length, gait shape and gait pace of a subject through guided therapy even in the absence of an attending health care provider. 
     Subjects, both human and animal, with aesthetic or athletic performance objectives relating to stride and gait characteristic such as optimized stride length, gait shape, cadence and the like can benefit from real-time feedback of their gait characteristics. Human performers and athletes have to rely on reviewing video of their gait after their training session to determine how they must alter their gait in the next training session to more closely reflect desired gait characteristics. Animals that are desired to have certain aesthetic or athletic performance objectives relating to their gait must rely on human trainers to provide feedback of the adequacy of their gait characteristics during the training session. There is a need for real-time feedback to subjects of the adequacy of their gait characteristics in meeting desired gait characteristics without the use of a human trainer. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to products and methods to improve gait performance in subjects with neurodegenerative conditions, movement disorders, injuries, surgical wounds, athletic performance objectives and combinations thereof. 
     Exemplary embodiments in accordance with the present invention use feedback methods during walking, running, and variations of walking and running, for example on a treadmill, with a rollator, or other assistive walking device, to train the gait in subjects with afflictions such as neurodegenerative diseases, movement disorders, injuries, surgical wounds, athletic performance objectives, or combinations thereof to embody certain characteristics. These characteristics may include stride length, heel-toe motion, stepping cadence, pace, stride shape and the like. 
     The present invention includes a walking surface and an assistive walking apparatus which is available to help the subject maintain stability while standing, walking, jogging, running, or variations thereof. For example, on a walking surface such as the ground, the subject may use an assistive walking apparatus in the form of a walker, rollator, crane, crutch, wheelchair, or variations thereof; on a walking surface such as a treadmill surface, the subject may use an assistive walking apparatus in the form of railings along the treadmill surface. Furthermore, the present invention includes a gait training system that the subject himself or a clinician, therapist, nurse, trainer, or other attendant to the subject attaches to the assistive walking apparatus. In one embodiment, the range of detection of a distance sensor is positioned to be orthogonal to the plane of motion of the subject&#39;s foot during a step. In addition, the range of detection is positioned to detect the presence of a desired characteristic of each step. The distance sensors measure distance using electromagnetic radiation, such as infrared light and radar, or sonic waves, such as ultrasound. 
     Crossing of the target beam by a portion of the subject is determined by comparing the data generated by the distance sensor, which measures the distance to the closest object in its line of detection. A calibration dial in a processing unit controlling the distance sensor is used to set a threshold distance. The threshold distance is determined to reflect the lateral variability of the subject&#39;s gait or the width of the assistive walking apparatus, whichever is greater. The system interprets any distance greater than this threshold as an uninterrupted target beam. The system interprets any distance smaller than this threshold as the subject&#39;s leg or foot interrupting the target beam. This comparison is done by an electronic circuit, microprocessor, computer, or other suitable components. Positive auditory feedback of crossing the target beam is also generated by an electronic circuit, microprocessor or computer and actuated through electro-acoustic transducers such as loudspeakers, earphones, headphones, piezoelectric speakers and variations thereof. Positive visual feedback of crossing the target beam is also generated by an electronic circuit, microprocessor or computer and actuated through light emitting diodes, LCD displays, computer displays, gauges, lights, paper printout, and variations or combinations thereof. 
     Exemplary embodiments of the present invention include a method for evaluating the subject&#39;s performance of the heel-toe motion. For example, the range of detection of the distance sensor is set to detect the presence of a heel-toe motion in the step and is positioned a distance above the walking surface. If the subject does not perform the heel-toe motion and steps in a flat-footed fashion, the subject&#39;s foot will not cross into the range of detection and no positive auditory and/or visual feedback is given for that step. The processing unit collects and evaluates data accordingly. 
     Exemplary embodiments of the present invention include a method for training the subject to perform the heel-toe motion with each step. The range of detection of the distance sensor is set to detect the presence of a heel-toe motion in the step and is positioned a distance above the walking surface. In this embodiment, when the subject does not perform the heel-toe motion and steps in a flat-footed fashion, the subject&#39;s foot will not cross the target beam and no positive auditory and/or visual feedback is given for that step. The subject is instructed to modify each successive step so that each step elicits positive feedback. 
     Exemplary embodiments of the present invention include a method for evaluating the subject&#39;s stride length. The range of detection of the distance sensor is set to detect a minimum stride length and is positioned a certain distance away from the subject along the intended walking path. When the subject does not step the minimum length, the subject&#39;s foot will not cross the target beam and no positive auditory and/or visual feedback is given for that step. The processing and control unit collects data accordingly. 
     Exemplary embodiment of the present invention includes a method for training the subject to exhibit a minimum stride length. The range of detection of the distance sensor is set up to detect a minimum stride length and is hence positioned a certain distance away from the subject along the intended walking path. When the subject does not step the minimum length, the subject&#39;s foot will not cross the target beam and no positive auditory and/or visual feedback is given for that step. However, the range of detection is set to detect both the presence of a heel-toe motion in the step as well as a minimum stride length and is positioned a distance above the walking surface as well as a certain distance away from the subject along the intended walking path. When the subject both performs the desired heel-toe motion as well as strides the minimum length, the subject&#39;s foot crosses the target beam and a positive auditory and/or visual feedback is given in the form of a tone and/or light. The subject is instructed to modify each successive step so that each step elicits positive feedback. 
     Exemplary embodiments of the present invention include a method for evaluating and training the cadence of the subject&#39;s gait. The range of detection of the distance sensor is placed at a distance near enough to the subject and close enough to the walking surface that every step will cross it. The electronic circuit, microprocessor, or computer used to process data from the distance sensor and to generate the feedback signals sent to the audio and visual actuators may additionally be programmed to time the period between successive steps and provide negative auditory and/visual feedback when the cadence is not within a desired window. One form of auditory or visual feedback, such as a low frequency beep or yellow light, is generated to signal that the subject&#39;s cadence is too slow, and another form of auditory or visual feedback, such as a high frequency beep or red light, is generated to signal that the subject&#39;s cadence is too fast. The processing unit collects data accordingly, or if the subject is being trained, the subject is instructed to modify his cadence to avoid eliciting the negative feedback. 
     Exemplary embodiments of the present invention include a method for evaluating and training the minimum pace of the subject&#39;s gait. The range of detection off the distance sensor is placed at a distance from the subject correlating to the desired stride length every step of sufficient length will cross it. The electronic circuit, microprocessor, or computer used to process data from the distance sensor and to generate the feedback signals sent to the audio and visual actuators may additionally be programmed to divide the minimum distance of each stride that crosses the target beam by the time between strides to determine the pace of the subject&#39;s gait and provide negative auditory and/visual feedback when the pace is not within a desired window. One form of auditory or visual feedback, such as a low frequency beep or yellow light, is generated to signal that the subject&#39;s pace is too slow, and another form of auditory or visual feedback, such as a high frequency beep or red light, is generated to signal that the subject&#39;s pace is too fast. The processing unit collects data accordingly, or if the subject is being trained, the subject is instructed to modify his pace to avoid eliciting the negative feedback. 
     Exemplary embodiments of the present invention include a method for evaluating and training the subject&#39;s left leg gait and right leg gait independently. The electronic circuit, microprocessor, or computer used to process data from the distance sensor and to generate the feedback signals sent to the audio and visual actuators may additionally be programmed to determine if each datum collected by the distance sensor corresponds to the subject&#39;s left or right foot. If the distance sensor is attached to the assistive walking apparatus on the subject&#39;s left side, then the a datum corresponds to a step by the left leg if the distance measured by the sensor is significantly shorter than both the calibrated threshold distance as well as the distance measured by the sensor during the previous step; the datum corresponds to a step by the right leg if the distance measured by the sensor is significantly shorter than both the calibrated threshold distance as well as the distance measured by the sensor during the previous step; and the datum corresponds to a step by the same leg that performed the previous step if the distance measured by the sensor is not significantly shorter nor significantly longer than the distance measured by the sensor during the previous step. The opposite determinations would be made if the distance sensor is attached to the assistive walking apparatus on the subject&#39;s right side. 
     Exemplary embodiments of the present invention include a method for evaluating and training the symmetry of the subject&#39;s gait. Since the subject&#39;s left and right legs may be evaluated independently, the electronic circuit, microprocessor, or computer used to process data from the distance sensor and to generate the feedback signals sent to the audio and visual actuators may additionally be programmed to compare the adequacy of the subject&#39;s left leg gait in exhibiting desired characteristics against the adequacy of the subject&#39;s right left gain in exhibiting the same characteristics. One example is to set up the gait training system to evaluate achievement of a minimum stride length. The most current datum corresponding to the left stride length may be compared to the most current datum corresponding to the right stride length. If the difference between the two lengths is greater than a certain preset tolerance, then the gait training system shall deliver negative auditory or visual feedback to indicate to the subject and persons attending to the subject that the left and right stride lengths are not sufficiently symmetrical. The processing unit collects data accordingly, or if the subject is being trained, the subject is instructed to modify his pace to avoid eliciting the negative feedback. Using similar methods, symmetry in other characteristics of gait, such as performance of the heel-toe motion, stepping speed, and the like may be evaluated and trained. 
     Exemplary embodiments of the present invention include a method for evaluating and reducing the lateral wavering of the subject&#39;s gait. Since the subject&#39;s left and right legs may be evaluated independently, the electronic circuit, microprocessor, or computer used to process data from the distance sensor and to generate the feedback signals sent to the audio and visual actuators may additionally be programmed to compare the distance measured by the distance sensor of the left or right leg when it crosses the target beam during the current step to the distance measured by the distance sensor of the same leg when it crossed the target beam during the previous step. If the difference between these two distances shows that the two distances are significantly different, as determined by a preset tolerance, then the gait training system shall deliver negative auditory or visual feedback to indicate to the subject and persons attending to the subject the detection of wavering in the subject&#39;s gait. The processing unit collects data accordingly, or if the subject is being trained, the subject is instructed to modify his gait to avoid eliciting the negative feedback. 
     The present invention includes the placement of distance sensors in positions so that other parts of the subject&#39;s leg, such as the knee, shin, or thigh, cross the target beam of the distance sensor to trigger feedback on the subject&#39;s gait characteristics. In addition, the present invention includes the simultaneous placement of multiple distance sensors in same or varying positions to make evaluate and provide feedback on multiple gait characteristics at the same time. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a back perspective view from a first side of an embodiment of a feedback-enhanced assistive walking device in accordance with the present invention; 
         FIG. 2  is a back perspective view from a second side of an embodiment of a feedback-enhanced assistive walking device in accordance with the present invention; 
         FIG. 3  is a front elevation view of an embodiment of distance sensor mount and distance sensor for use in accordance with the present invention; 
         FIG. 4  is a side elevation view of the distance sensor mount and distance sensor of  FIG. 3 ; 
         FIG. 5  is a top plan view of the distance sensor mount and distance sensor of  FIG. 3 ; 
         FIG. 6  is a perspective view of the distance sensor mount and distance sensor of  FIG. 3 ; 
         FIG. 7  is a plan view of the distance sensor mount and distance sensor of  FIG. 3  with axis lines; 
         FIG. 8  is an exploded perspective view of the distance sensor mount and distance sensor of  FIG. 3 ; 
         FIG. 9  is a front elevation view of an embodiment of a processing unit for use in accordance with the present invention; 
         FIG. 10  is a first side elevation view of the processing unit of  FIG. 9 ; 
         FIG. 11  is a second side elevation view of the processing unit of  FIG. 9 ; 
         FIG. 12  is a back elevation view of the processing unit of  FIG. 9 ; 
         FIG. 13  is bottom plan view of the processing unit of  FIG. 9 ; 
         FIG. 14  is an exploded perspective view of the processing unit of  FIG. 9 ; 
         FIG. 15  is a perspective view of an embodiment of the assistive walking device of the present invention with a subject&#39;s foot under the range of detection of the distance sensor; 
         FIG. 16  is a front elevation view of an embodiment of the assistive walking device of the present invention with a subject&#39;s foot under the range of detection of the distance sensor; 
         FIG. 17  is a perspective view of an embodiment of the assistive walking device of the present invention with a subject&#39;s foot making a heel-toe motion; 
         FIG. 18  is a top plan view of an embodiment of the assistive walking device of the present invention with a subject&#39;s foot moving perpendicular to the range of detection of the distance sensor; 
         FIG. 19  is a perspective view of an embodiment of the assistive walking device of the present invention with a subject&#39;s foot crossing the range of detection of the distance sensor using a heel-toe motion; and 
         FIG. 20  is a front elevation view of an embodiment of the assistive walking device of the present invention with a subject&#39;s foot crossing the range of detection of the distance sensor using a heel-toe motion. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to a system for improving movement in a subject. The movement includes a person moving by foot across a walking surface such as a floor or the ground and encompasses any type of movement by foot including walking and running Referring initially to  FIGS. 1 and 2 , an exemplary embodiment of a system  100  includes an assistive walking device  132  that includes a frame  140  that extends up from a walking surface  130 . The frame is configured to support the subject that is moving by foot, i.e., walking or running, across the walking surface. In one embodiment, the assistive walking device  132  is a walker, a wheeled rollator, a cane or a rolling chair. In this embodiment, the walking surface is the floor or ground across which the subject moves with the assistive walking device. Therefore, the assistive walking device moves with regard to a stationary walking surface. Alternatively, the assistive walking device is stationary and the walking surface moves. In another embodiment, the assistive walking device is a treadmill and the walking surface is a moving treadmill surface of the treadmill. 
     In the embodiment as illustrated, the system  100  is a feedback-enhanced rollator device  100  and the assistive walking device is a rollator  132  having a tubular frame  140  that is used by a subject to provide walking assistance. The frame  140  is a three-sided frame, and the subject will grasp the frame along a pair of horizontal top rails  150  and stand generally within the three sides of the frame. Suitable rollators are known and available in the art, and any suitable rollator provides the desired walking assistance can be used. The rollator  132  also includes two or four wheels  110  that roll along the walking surface  130 . 
     The system  100  also includes a first distance sensor  120  that is attached to any desired location along the frame  140  of the assistive walking device  132 . The first distance sensor  120  can be selectively placed along any desired portion of the frame  140  and fixedly secured in that portion of the frame  140 . In addition, the first distance sensor  120  can be remove from the frame  140  or moved along elements of the frame  140  without completely removing the first distance sensor  120  from the frame  140 . This facilitates adjustment of the location and monitored area of the first distance sensor with respect to the assistive walking device  132  and the walking surface  130 . 
     In one embodiment, the first distance sensor  120  includes a range of detection  135 , i.e., a range over which the sensor can detect objects and determine the distance to those objects. The range of detection  135  extends along a first line, extending from the frame across the walking surface. The distance sensor can detect objects crossing into the first line within the range of detection. In addition to detecting the occurrence of an object crossing into the range of detection, the distance sensor can determine or calculate a distance from that object to the distance sensor. Therefore, the distance sensor provides two distinct measurements, object detection and distance to object measurement. In one embodiment, these objects include portions or parts of the subject that is moving by foot along the walking surface, for example, a foot, leg (upper and lower), shin, knee, hip, torso, arm, neck or head. 
     In one embodiment, the first distance sensor  120  is an optoelectronic distance sensing device that includes an optical light source emitting a pre-defined frequency of light along the first line and a photodetector filtered to detect the pre-defined frequency. Suitable optical light emitting sources are known and available in the art. In one embodiment, the optical light emitting source emits infrared light, for example, light having a pre-defined frequency from about 1 mm to about 750 nm. The optical light source and photodetector are aligned with the range of detection in order to emit light and to detect reflected light along the line of the range of detection. 
     In one embodiment, the system also includes a timing device (not shown) in communication with the optical light source and photodetector. This timing device or the necessary electrical or electronic circuitry for the timing device can be incorporated into the first distance sensor  120  or can be provided in a separate control mechanism that is in communication with the first distance sensor. The timing device measures an elapsed time for light of the pre-defined frequency to project or to be emitted from the optical light source along the first line, to reflect on the object crossing into the first line and to fall upon the photodetector. This can be used to calculate the distance of the object from the first distance sensor. 
     In one embodiment, the distance sensor  120  is a sonic-electric distance sensing device that includes a cyclic sound pressure generator emitting a pre-defined frequency of sound along the first line and a sonic detector configured to detect the pre-defined frequency of sound being reflected along the first line. Suitable cyclic sound pressure generators are known and available in the art. In one embodiment, the pre-defined frequency is an ultrasonic frequency of at least about 20 kHz. The cyclic sound pressure generator and sonic detector are aligned with the range of detection in order to emit sound and detect reflected sound along the line of the range of detection. 
     In one embodiment, the system also includes a timing device in communication with the cyclic sound pressure generator and the sonic detector. The necessary electrical or electronic circuitry for the timing device can be incorporated into the first distance sensor  120  or can be provided in a separate control mechanism that is in communication with the first distance sensor. The timing device measures an elapsed time for sound of the pre-defined frequency to project from the cyclic sound pressure generator along the first line, to reflect on the object crossing into the first line and to fall upon the sonic detector. This can be used to calculate the distance of the object from the first distance sensor. 
     In one embodiment, the distance sensor  120  is a radio detection and ranging device that includes a radio transmitter emitting a pre-defined frequency of radiation along the first line and a radio receiver configured to detect the pre-defined frequency of radiation. Suitable radio transmitters are known and available in the art. The radio transmitter and radio receiver are aligned with the range of detection in order to emit radiation and detect reflected radiation along the line of the range of detection. 
     In one embodiment, the system also includes a timing device in communication with the radio transmitter and the radio receiver. The necessary electrical and electronic circuitry for the timing device can be incorporated into the first distance sensor  120  or can be provided in a separate control mechanism that is in communication with the first distance sensor. The timing device measures an elapsed time for radiation of the pre-defined frequency to project from the radio transmitter along the first line, to reflect on the object crossing the first line and to fall upon the radio receiver. This can be used to calculate the distance of the object from the first distance sensor. 
     In one embodiment, the system  100  includes a second distance sensor separate from the first distance sensor. The second distance sensor is attached to the frame of the assistive walking device  132  and has a range of detection  170  extending along a second line running from the frame  140  across the walking surface  130 . This second line is separate from the first line. The second distance sensor  160  is configured to detect an object crossing into the second line within the range of detection and to determine a distance from that object to the second distance sensor. 
     Suitable embodiments and configurations for the second distance sensor  160  are the same as for the first distance sensor  120 . The first and second distance sensors can be the same type of sensor or different types of sensors, e.g., ultrasonic and infrared. In addition, both distance sensors can have the same type of associated mounting and control structures. In one embodiment, the first distance sensor and the second distance sensor comprise a unitary structure. As illustrated, the first and second distance sensors are separate structures, and the second distance sensor  160  is positioned farther from a subject using the assistive walking device. In addition the first and second ranges of detection are parallel. However, the second distance sensor  160  can be attached to any suitable location of the frame  140  of the assistive walking device  132 . The second distance sensor can be positioned closer to or farther from the subject, higher up from the walking surface or lower down toward the walking surface. The second distance sensor  160  can be located on section of the frame opposite the first distance sensor such that the sensors are facing in opposite direction. In addition, the second distance sensor  160  can be positioned on the frame such that the ranges of detection are not parallel but intersect, for example at an angle of about 90 degrees. In addition to a single second distance sensor, the system  100  can include a plurality of second distance sensors each configured as discussed above for the single second distance sensor. 
     Although the distance sensors can be provided with a housing that is mounted directly to the frame  140  of the assistive walking device  132  using suitable mounting devices such as clamps and magnets, the system includes a distance sensor mount  134  attached to the frame  140  of the assistive walking device  132 . The distance mount sensor permits adjustment of the location of distance sensors attached to the mount include spacing of the range of detection line above the walking surface by a desired height and the line of intersection of a walking path of the subject using the assistive walking device. 
     An exemplary embodiment of the distance sensor mount  134  and first distance sensor  120  is illustrated in  FIGS. 3-8 . The distance sensor mount  134  includes a body  300  having a length  310 . The distance sensor mount  134  provides for adjustment around and along a first axis  340  ( FIG. 7 ) and around and along a second axis  350 . Adjustment along the first axis  340  is provided by a telescoping mechanism provided in the body  300  between the first end  360  and the second end  370  opposite the first end  360 . The telescoping mechanism adjusts the length  310  of the body  300 . As illustrated, the telescoping mechanism is provided by an inner tube  320  disposed in an outer or sheathing tube  330 . The inner tube  320  moves into and out of the outer tube  330  and is held in place by a knob  380  and set screw  390  that passes through a threaded opening in the outer tube  330  and presses against the inner tube  320 . Other suitable telescoping mechanisms can include external threads on the inner tube  320  and corresponding internal threads on the outer tube  330 . The inner tube  320  can include a gear rack and the outer tube  330  can include a corresponding gear wheel. The telescoping mechanism can be manual or motorized. 
     In addition to providing a telescoping mechanism, the same components of the body  300  can provide a rotation mechanism disposed in the body and configured to permit relative rotation between the first end  360  and the second end  370  of the body  300  around the first axis  340 , which is parallel to the length  310  of the body  300 . Preferably, the same components that provide for the telescoping mechanism also provide for the rotation mechanism. Alternatively, the telescoping and rotation mechanisms can be separate mechanisms that utilize separate components. The rotation mechanism allows the first distance sensor  120  and therefore the range of detection to rotate about the first axis  340 . 
     Adjustment of the distance sensor mount  134  along the second axis  350  is provided by an attachment mechanism  400  that is disposed on the first end  360  of the body  300  and attached to a selected location on the frame  140  of the assistive walking device  132 . In one embodiment, the attachment mechanism  400  includes a mounting body  410  arranged to accept and to accommodate the cross-sectional shaped of the frame  140  of the assistive walking device  132 . In general the mounting body  410  partially surrounds the frame  140  and has a gap or opening large enough to allow the frame  140  to pass into and out of the mounting body  410 . The attachment mechanism also includes a tightening knob  420  attached to a threaded pin  430  with a rubber tip  440 . When the tightening knob  420  is turned, the threaded pin  430  advances into the mounting body  410 , clamping the frame  140  between the rubber tip  430  and a plurality of rubber friction pads  250  attached to the inside of the mounting body  410 . Reversing the rotation of the tightening knob  420  loosens the clamping on the frame and allows the distance sensor mount to be moved along the frame parallel to the second axis  350 . 
     Other suitable attachment mechanism can be used such as spring loaded clamps and magnetic fasteners. As illustrated, the attachment mechanism  400  is separate from the frame  140  and does not work in conjunction with any components on the frame  140  of the assistive walking device  132 , although it is shaped to accommodate the size and shaped of the frame. In another embodiment, the attachment mechanism  400  works in conjunction with structures on the frame  140  including tracks, gear racks, gear wheels, slots and holes. 
     In one embodiment, the attachment mechanism  400  is directly attached to the first end of the body  300 . Alternatively, a pivoting mechanism is provided in the distance sensor mount  134  between the first end  360  of the body  300  and the attachment mechanism  400 . The pivoting mechanism  460  provides pivoting or rotational movement of the body  300  around the second axis  350 . This also provides rotation between the body  300  and the attachment mechanism  400  as well as rotation of the first distance sensor  120  about the second axis  350 . 
     In one embodiment, the pivoting mechanism includes a first part of a pivot joint  470  extending from the mounting body  410  and a second part of the pivot joint  480  attached to the first end  360  of the body  300 . A joint pin  490  passes through aligned holes in the first and second parts of the pivot joint  470 . This defines the axis around which the pivoting mechanism pivots. In one embodiment, the joint pin  490  is threaded, and nuts  500 , for example wing nuts, are attached to either end of the joint pin  490 . The angle between the mounting body  410  and the body  300  is selected and locked in place by tightening the wing nuts  500  on both ends of the joint pin  490 . Additional stability is provided by teeth  510  on the first and second parts of the pivot joint. 
     The first distance sensor  120  is disposed on and attached to the second end  370  of the body. As illustrated in  FIG. 8 , the first distance sensor  120  includes a sensor enclosure  520  that is attached to bottom of the inner tube  320  and houses the desired sensor components  530  that emit the desired target beam. In one embodiment a bandpass filter lens  540  is mounted on the sensor enclosure  520  to enclose the sensor components. In one embodiment, electric and electronic access to the sensor components is provided by routing the appropriate wires through the body  300 . Access to the interior of the body is through the first end  360 . In one embodiment, the second part of the pivot joint  480  includes a cable inlet  550  that allows cables (not shown) to enter the pivot joint, run through the body and enter the sensor enclosure  520  to connect to the sensor components  530 . The cables permit power and control to be communicated to the sensor components and to collect data from the sensor components. Alternatively, the first distance sensor includes all of the power and control mechanisms. In one embodiment, the first distance sensor communicates wirelessly, e.g., Bluetooth or WiFi, with control and data collection circuits. 
     The distance sensor mount  134  can be used to attach any sensor to the assistive walking device  132  and provides multiple degrees of freedom of movement of the distance sensor with respect to the assistive walking device. 
     Returning to  FIGS. 1 and 2 , the system includes a control or processing unit  133  that is attached to the assistive walking device  132  and is in communication with the distance sensor  120  for example through a wire or cable  136 . The processing unit and distance sensor can also communicate wirelessly. The processing unit  133  sends control commands to the distance sensor  120 , receives data from the distance sensor  120 , analyzes the received data and determines characteristics of the movement of the subject across the walking surface using the analyzed data. 
     Referring to  FIGS. 9-14 , an exemplary embodiment of a control box  133  is illustrated. The control box  133  includes a two-piece casing  600 . Suitable materials for the casing include, but are not limited to, plastic, metal, wood and other natural or synthetic materials. The control box includes a clamping or attachment mechanism to provide for releasable attachment of the control box  133  to the frame  140  of the assistive walking device  132 . In this embodiment, the control box  133  is attached to the frame  140  at a location that is easily accessible to the subject. 
     In one embodiment as illustrated, the clamping mechanism is a two-part clamping mechanism. The two-part clamping mechanism includes a first attached portion  610  that is attached or fixed to one of the two pieces of the casing  600  and a second independent portion  620 . The two parts of the clamping mechanism have complementary mating shapes. The two portions of the clamping mechanism are shaped to fit around the frame  140  of the assistive walking device  132 . In one embodiment, each portion of the clamping mechanism represents one half of a cylinder having a circular cross-section. This accommodates a tubular frame. The two portions are secured together and to the frame by tightening a bolt pin  630  and nut  640  that are inserted through both the attached portion of the clamp  610  as well as the independent portion of the clamp  620 . In one embodiment, the independent portion  620  includes protrusions  650  that fit into corresponding slots  660  in the first portion  610  to provide for proper alignment of the portions and to strengthen the joint between the portions. 
     In one embodiment, the processing unit  133  includes circuit board  670  within the casing that includes an analog circuit, a digital circuit, a programmable microprocessor and combinations thereof. These components provide for the desired control of the distance sensors, the collection of data, the processing of this data and the interfacing of the system with the subject. A power source  680 , for example a battery, that powers the components on the circuit board  670  and the distance sensor is provided in the casing. Alternatively, the power source can be a rechargeable power source or a photo-voltaic power source. 
     In order to communicate with the subject, the system includes a user interface attached to the assistive walking device and in communication with the processing unit  133 . The user interface accepts input from and provides output to the subject. Therefore, the processing unit provides output regarding the determined movement characteristics of the subject through this user interface. For assistive walking devices such as treadmills, the user interface can be incorporated into the control panel of the treadmill. In general, the user interface includes a display, knobs, dials, buttons, switches and combinations thereof. Suitable displays include a light, a printed label, a light emitting diode, a liquid crystal display, a projected image, a computer display and combinations thereof. As illustrated, the user interface is incorporated into the processing unit  133  and includes devices that are in communication with the circuit board  670 . These devices include a piezoelectric speaker  690  that actuates audio signal outputs, a stereo audio jack  700  that also actuates audio signal outputs, a knob  730  connected to a potentiometer  720  that controls the volume of audio outputs, a light emitting diode  740  that actuates visual signal outputs, an input jack  750  that receives the cable  136 , a sensor calibration dial  760  that adjusts the length range of detection and a switch  710  that toggles the circuit on and off 
     In one embodiment, the system also includes a feedback mechanism attached to the frame of the assistive walking device and is in communication with the processing unit. The feedback mechanism communicates the determined movement characteristics to the subject. In one embodiment, the components of the processing unit  133  are used as the feedback mechanism. Suitable feedback mechanisms include, but are not limited to, tactile feedback, visual feedback, auditory feedback and combinations thereof. For example, the tactile feedback can be vibration, created by an spinning eccentric weight location in the processing unit and communicating the vibration through the frame. The visual feedback can be a light, a gauge, a computer readout, a light emitting diode display, a liquid crystal display, a projected image, a paper printout, a computer display and combinations thereof. For example, the display of a treadmill can be used or the lights associated with the processing unit. Suitable auditory feedback includes, but is not limited to, a tone, a series of tones, a melody, a synthesized voice, a recorded voice and combinations thereof. These can use the speaker and speaker jack of the processing unit. 
     The present invention is also directed to a method for improving movement in a subject using the system of the present invention. The first distance sensor  120 , or any other distance sensor in accordance with the present invention, is associated with the assistive walking device  132  by attaching the distance sensor mount  134  to the frame  140 . The first distance sensor is used to detect a portion, e.g., the foot, of the subject crossing into the range of detection of the first distance sensor that extends along the first line running from the first distance sensor. In addition, the first distance sensor determines a distance from that portion of the subject to the distance sensor. Referring to  FIGS. 15-20 , the portion of the subject can be the leg  800  or foot  810  of the subject using the assistive walking device  132 . As shown in  FIGS. 16 and 20 , the line of the range of detection  135  of the first distance sensor is spaced a desired height  820  above the walking surface  130 . This height  820  can be selected to be close enough to the walking surface  130  such that any step of the subject intersects the line  135 . 
     Alternatively, the line  135  is spaced above the walking surface  130  a sufficient distance to encourage the subject to make the proper walking motion. As illustrated in  FIGS. 15 and 16 , the line  135  is spaced a height  820  above the walking surface such that the foot  810  of the subject will pass beneath the line  135  when the subject makes a shuffling motion with the foot  810 , i.e., sliding the foot  810  along the walking surface  130  without significantly raising the heel or toe. As the foot does not intersect the line of the first distance sensor, the subject is not provided with any positive feedback, because the selected illustrated height  820  is selected to encourage the subject to walk with a heel-to-toe motion, raising the toe of the foot  810  above of the walking surface as illustrated in  FIG. 17 . 
     Referring to  FIGS. 19 and 20 , the toe of the foot  810  intersects the line of the range of detection  135  when the foot is moved using the heel-to-toe motion a sufficient distance. This triggers a positive feedback response being delivered to the subject. The first distance sensor detects the foot in the line of detection and can also determine a distance  850  between the first distance sensor and that foot  810 . As illustrated in  FIG. 18 , the various adjustments in the distance sensor mount, in addition to providing for height adjustment, allow the line of the range of detection  135  to be moved parallel to the line of movement  830  of the subject&#39;s leg  800  and foot  810 . In addition, the line of the range of detection  135  can be pivoted to adjust the angle  840  between the line of the range of detection  135  and the line of movement  830 . All of these adjustments provide for different scenarios to be used in evaluating and improving the movement of a subject using the assistive walking device. Depending on the position, the system can target stride length, gait, pace, cadence, lateral wavering and gait symmetry. 
     In one embodiment, the portion of the subject to be detected is the foot of the subject, and the first line  135  is positioned above the walking surface  130  a sufficient distance so that each foot of the subject crosses into the range of detection only when the subject moves by foot across the walking surface using a heel-to-toe walking motion. Alternatively, the portion of the subject to be detected is a foot of the subject, and the first line is positioned a sufficient distance from the subject moving by foot across the walking surface using the assistive walking device so that each foot of the subject crosses into the range of detection only when the subject moves by foot across the walking surface using a prescribed stride length. In one embodiment, a time required for the subject to repeatedly move each foot into the range of detection is measured and used to determine a pace for the subject at the prescribed stride length. Feedback is provided to the subject regarding the determined pace such that this feedback can be used to modify the determined pace of the subject. 
     In one embodiment, the portion of the subject to be detected is a foot of the subject, and the first line is positioned above the walking surface a distance so that each foot of the subject crosses into the range of detection upon any given stride, regardless of stride length or heel-to-toe motion. A time required for the subject to repeatedly move each foot into the range of detection is measured and used to determine a cadence for the subject. Feedback is provided to the subject regarding the determined cadence and is used to modify the determined cadence of the subject. 
     In one embodiment, the portion of the subject to be detected is the foot of the subject, and for each foot changes in a gait distance between that foot and the first distance sensor between successive strides of each foot is tracked. These tracked changes are used to determine lateral wavering for each foot. Feedback is provided to the subject regarding the determined lateral wavering, and the feedback is used to modify the lateral wavering of each foot of the subject. 
     In one embodiment, the portion of the subject to be detected is a foot of the subject, and for each foot a gait distance between that foot and the first distance sensor during successive strides of each foot is tracked. The tracked gait distances of both feet are compared to determine a gait symmetry. Feedback is provided to the subject regarding the determined gait symmetry and is used to modify the gait symmetry of the subject. In general, feedback is provided to the subject regarding detection of the desired portion of the subject crossing into the range of detection in addition to the determined distance, and this feedback is used to improve movement in the subject. 
     In one embodiment, a plurality of additional distance sensors is associated with the assistive walking device, and each additional distance sensor is used to detect a distinct portion of the subject crossing into a range of detection of that additional distance sensor. These ranges of detection extend along an additional lines running from each additional distance sensor. In addition, each additional sensor is used to determine a distance from the distinct portion of the subject crossing into the range of detection and the additional distance sensor. 
     In one embodiment, by employing the auditory and visual feedback of the invention, subjects are trained to increase their stride lengths and walk with a heel-toe motion as a means of recalibrating proprioceptive feedback from their leg muscles and thus correct the sensory-motor mismatch in a similar way as it seems to do in the Lee Silverman Voice Treatment program (Ramig, Intelligibility in Speech Disorders: Theory, Measurement and Management, John Benjamins Pub. Co., R. Kent, ed., Amsterdam, 1992). This embodiment may be implemented for subjects with neurodegenerative conditions and movement disorders such as but not limited to Parkinson&#39;s Disease, Parkinsonian syndromes, Senile Gait Disorder, and Ataxia; all of which are capable of inducing sensory-motor mismatch. 
     In another implementation, the auditory and visual feedback of the invention can supplement or substitute the feedback usually provided by a trainer, therapist, caretaker, or variation thereof during the course of physical rehabilitation following injury or surgery. The invention is used outside of physical therapy sessions to reinforce the feedback given by therapists during therapeutic sessions. Therapists adjust the gait training system to provide the subject with positive feedback when desired gait characteristics are detected. Depending on the injury, these characteristics may include a minimum stride length to increase range of motion in the leg joints, a heel-toe motion to maximize stability, symmetry between the left and right leg to promote proper weight distribution, and the like. The gait training system in this implement likely, but does not necessarily, incorporates the use of a walker, rollator, or cane as the assistive walking device. 
     In another implementation, the auditory and visual feedback of the invention can supplement or substitute the feedback usually provided by a trainer, coach, or variation thereof during the course of athletic training such as walking, jogging, running, or variations thereof The invention is used during training sessions to provide real-time feedback of gait characteristics to subjects. Subjects themselves or their trainers may set up the invention to detect desired characteristics such as cadence, pace, stride length, symmetry, heel-toe motion, and the like. The gait training system in this implement likely, but does not necessarily, involve the subject walking, jogging, or running upon a treadmill to which the gait training system is attached. 
     In another implementation, the auditory and visual feedback of the invention can supplement or substitute the feedback usually provided by a trainer in the process of training a subject to walk, jog, or run, with certain gait characteristics. These characteristics may include a specific stride length, symmetry, cadence, pace, and the like. Subjects in this implementation are animals, such as dogs and horses. In this case, the animal must first be conditioned to associate the auditory feedback such as a tone of a certain frequency or the visual feedback such as the illumination of a certain light with a favorable event. This is achieved by repeatedly pairing the presentation of the feedback intended for use with the invention with the presentation of enjoyable stimuli, such as food, petting, or verbal praise. The aforementioned procedure, called Pavlovian conditioning, is a well established methodology. After successful conditioning, the animal will eventually perceive said feedback intended for use with the invention as a desirable event, and the gait training system may be used. The gait training system in this implement likely, but does not necessarily, involve the subject walking, jogging, or running upon a treadmill to which the gait training system is attached. 
     Having now fully described this invention, it will be understood to those of ordinary skill in the art that the same can be performed within a wide and equivalent range of conditions, formulations, and other parameters without affecting the scope of the invention or any embodiment thereof. All patents and publications cited herein are incorporated by reference in their entirety.