FIELD

The present disclosure relates to resistive devices and, more particularly, to resistive devices that employ eddy current braking.

BACKGROUND AND SUMMARY

This section provides background information related to the present disclosure which is not necessarily prior art. This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

Many patients with stroke, cerebral palsy, and other neurological conditions have significant limitations in walking, and experience limited mobility for the rest of their life. Lack of mobility significantly affects functional independence and, consequently, results in greater physical disability. Facilitating gait recovery, therefore, is a key goal in rehabilitation.

With the growing elderly population, the prevalence of many of the neurological conditions is expected to increase worldwide, and the need for intervention to address gait dysfunction will grow. Appropriately designed rehabilitation devices can assist in meeting this imminent heightened demand for care.

Task-specific training is recognized as the preferred method for gait training following neurological injury because the motor activity seen in this type of rehabilitation is known to facilitate neural plasticity and functional recovery. However, current task-oriented gait training approaches seldom focus on improving muscle strength and impairment, which are also critical for motor recovery and plasticity.

For example, incorporating strengthening exercises into rehabilitation interventions can counteract muscle weakness and improve function in individuals with a wide variety of neurological and orthopedic disorders. Numerous studies have also demonstrated a link between the ability to produce adequate force in the muscles of lower limbs and gait speed following neurological injury. Additionally, resistance training may result in adaptive changes in the central nervous system.

However, the benefits of strength training may not translate maximally into improvements in gait function unless the training incorporates task-specific elements. This task-specific loading of the limbs—termed as functional strength training—is gaining popularity when rehabilitating individuals with neurological injury.

Currently, devices exist to provide functional strength training during walking. The simplest of which applies resistance by placing a weight on the lower limb. Research indicates that this intervention can increase the metabolic rate of healthy subjects as well as increase power of the hip and knee and muscle activation during walking in neurologically injured populations. While this method of functional strength training is simple and practicable, it is hindered by a low torque-to-weight ratio: making large resistances unobtainable without excessively large weights.

Cable driven devices address this issue by locating the heavy force generating elements (actuators and cable spools) away from the patient. This device resists ankle translation during the swing phase of gait, and studies have found that it can potentially improve step length symmetry and gait speed following stroke. However, methods that resist the user through cables will be difficult to use in over-ground training.

The majority of the existing methods for functional strength training apply resistance to the end effector region of the leg (i.e., foot or ankle). Because of this, the resistance may be irregularly distributed between the hip and knee joints, and compensatory strategies could be promoted as weaker muscles are not specifically targeted in the training. The magnitude of resistance applied to the leg could also change as a function of limb position. Further, the resistance in these applications is usually unidirectional, which would assist movement during certain phases of gait. Bidirectional resistance is possible, but only obtainable with supplementary equipment (additional actuators and cables) and controls that utilize gait detection.

For these reasons, providing resistance in the joint space (i.e., across the joint) may be beneficial for training and other biomechanical evaluations. However, making a device that is lightweight and wearable while still providing high bidirectional torque requires a unique approach.

According to the principles of the present teachings, a resistive device is provided that enables adjustable resistance to the muscles used during walking for functional strength training of gait, for example. Because the resistive device of the present teachings can be bench mounted, it strengthens the muscles used in this task. As outlined herein, this method of therapy is called functional strength or resistance training. The specific muscles are dependent on the joints (hip, knee, or both) that the resistive device is being worn on. The resistive device can be used for physical therapy made necessary due to weakness caused by neuromuscular diseases, such as stroke and cerebral palsy, orthopedic disorders, general disuse, or even for overall fitness.

Conventional resistive training strengthens isolated muscle groups during either flexion or extension, but does not have neuroplastic advantages. Purely assistive devices are advantageous because encourage goal-directed repetitive motions and facilitate neuroplasticity due to motor learning, but increases in patient strength are minimally seen in such assistive devices.

The present teachings integrate both concepts in that they provide either unidirectional or bidirectional resistance to motions of the leg during walking or other appendage movement, providing an option for in home use by patients, fewer hours spent in clinic for therapy, and better patient outcomes. There are a few existing devices designed for functional strength training, but they fail to address many key aspects of the therapy.

The forces that resist motion are purely dissipative and no energy is stored to assist the other motions of the leg as would be the case with a weight, spring, or entirely treadmill-based approach. In some embodiments of the present teachings, the present teachings can be used in conjunction with a treadmill or other machine, but does not require the use of one. Conventional devices require a treadmill and the nature of the design causes the wearable resistive device to be assistive during certain stages of walking as the treadmill shares in the work. The present invention addresses the most important aspects of functional strength training.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

