PART THREE OF A THREE-PART SERIES ABOUT STANDING SYSTEMS, LIFTS, AND BODY WEIGHT SUPPORT UNITS
Photos by Andrew Studer
In 1987, Hughes Barbeau studied the effects of weight support on spinal cats (with transected spinal cords). The study involved an ambulation protocol on a treadmill and revealed that the cats—with no communication between the hind limbs and brain—were still able to walk. A rehabilitation approach, soon to be transferred to human studies, was born.
The technology and science soon integrated to human applications and evolved to include initial diagnoses to be treated and parameters. Additionally, clinicians and scientists soon understood the multitude of benefits to patients receiving body weight support (BWS). The various systems contributing to recovery may include cardiovascular, neuromuscular, and musculoskeletal. Impairments benefiting from BWS intervention may include range of motion (ROM), endurance (cardiovascular, muscular, and neuromuscular), strength, and balance. The initial intent of BWS, based on Barbeau’s studies, was to investigate and utilize central neuroplasticity and stimulation of the central pattern generator (CPG) after spinal cord injury. This continues to be studied and is apparently a viable area of improvement for human subjects through BWS. As with all treatment applications in rehabilitation, our understanding continues to evolve. Soon after the III STEP conference in 2005, rehabilitation was fundamentally changed, emphasizing intensity and repetitions in the rehabilitation of neurologically impaired individuals. In all of health care, professionals were encouraged, if not incentivized, to use evidence-based medicine. These movements increased research on BWS in many diagnostic groups, and increased the prevalence of the different types of BWS systems. At present, we have BWS units with robotics, harnesses, rail systems, and inflation-based supports.
Despite all of the advances, BWS should not be considered a rehabilitation approach, but rather a tool or environment. Through safety and body weight reduction, BWS can afford the learner greater participation in recovery through higher levels of intensity or for a longer duration. Specifically, however, intensity is a widely misunderstood term. Intensity can come in the form of resistance, speed, accuracy, or duration. When used within a task-specific context, higher levels of intensity should increase the opportunity for neuroplasticity. Using BWS, therapists are afforded the opportunity to safely engage patients in higher levels of intensity. Specifically, patients can be allowed to experience a greater loss of balance or pathway deviation; begin a progression away from an assistive device; engage in higher speeds on the treadmill; do longer duration/distance walking; or even have additional weight/resistance on a limb or trunk while gait training (Table 1).
Movement of almost any kind (bed mobility, walking, stairs) in recovery from a stroke or other injury/surgery will require more energy. In addition, patients can become fatigued quickly as a function of their deconditioning. Through the alleviation of body weight, supporting 5% to 25%, BWS can enable patients to engage in more repetitions and fewer rest breaks per session. More repetitions (work time) and shorter breaks (rest time) per session mean that patients receive more practice in the task of gait, for maximal carryover. (See case studies #1 and #2 below.)
While BWS can be invaluable, the technology itself is not inexpensive, and clinic managers should take time to compare various units. The decision those managers face, however, should be about which unit to purchase—and not whether one is needed. There are significant differences between the various BWS models. To assist in understanding and decision-making, the following is a brief overview:
Style of harness. Most body weight support units include suspension through some sort of harness that fastens around the pelvis. Some models suspend the patient from underneath the groin, while others grasp at the iliac crest and still others include thigh straps. Notable exceptions include those that offer robotic, hydrodynamic, or inflation (air) support.
Type of suspension. Most BWS units suspend patients from overhead. Significant differences ensue, as some offer a single point of suspension, others by two point, and still others by four point suspension. Considerations for “which is best for me” are based on the intended use. With more points of control, therapists are afforded more adjustability—to introduce or eliminate asymmetry, for example. Single point suspension often allows for an immediate direction change—walking forward, sideways, and backwards without interruption. Notably, most models have “retro-fit kits” allowing for four point suspension to rotate as needed. Again, exceptions are noteworthy in that the air, water, and robotic suspensions support the patient (largely) from below, not overhead.
Versatility of use. Consider the population that you will be serving with this device. Robotic and inflatable units are for use solely above a treadmill. Many overhead suspensions are stable/stationary, while some are based on a unit that is mobile with wheels (allowing for BWS over ground) or through a tracking system that can be used above or over the treadmill.
Patients with greater levels of debility need more support and adaptability for donning the harness. This population is served best with an overhead harness and four point control. Higher level patients often need the challenge of a direction change more than they need extensive lift. They may benefit from a single point of suspension or a tracking system for balance challenges off the treadmill. Patients with spinal cord injury may be best served with more complete lower limb assistance through robotics.
One should also consider underwater treadmills as a form of body weight support—through buoyancy. These treatment environments offer the additional benefit of softening a loss of balance (through the hydrodynamics), similar to the function of the harness in a BWS system. In contrast, an underwater treadmill offers a consistent resistance to the swing phase of gait, again through the hydrodynamics/viscosity of water versus air.
Remember, whether over ground or on a treadmill, BWS can help you rehabilitate your patient more completely and faster through higher levels of intense practice. This environment (BWS) allows for more task-specific practice, more repetitions, and a higher level of intensity in terms of gait speed, duration, accuracy, balance, or resistance. As always, evidence and objective testing guide the expert therapist, using information from the patient to individualize and personalize treatment according to the International Classification of Function. Equipment can help us maximize our delivery of the evidence.
Barbeau H, Rossignol S. Recovery of locomotion after chronic spinalization in the adult cat. Brain Res. 1987;412:84–95.
Behrman AL, Harkema SJ. Locomotor training after human spinal cord injury: a series of case studies. Phys Ther. 2000;80:688-700.
Harkema SJ. Neural plasticity after human spinal cord injury: application of locomotor training to the rehabilitation of walking. Neuroscientist. 2001;7:455-468.
Sullivan KJ, Brown DA, Klassen T, et al; for the Physical Therapy Clinical Research Network (PTClinResNet). Effects of task-specific locomotor and strength training in adults who were ambulatory after stroke: results of the STEPS randomized clinical trial. Phys Ther. 2007;87:1580–1602.
Sullivan KJ, Knowlton BJ, Dobkin BH. Step training with body weight support: effect of treadmill speed and practice paradigms on poststroke locomotor recovery. Arch Phys Med Rehabil. 2002;83:683–691.
Mike Studer, PT, MHS, NCS, CEEAA, is a full-time clinician at Northwest Rehabilitation Associates, Salem, Ore. He is a board-certified neurologic clinical specialist and certified exercise expert for aging adults. Studer has been a PT for 21 years and is the current Chair of the Geriatric Section—APTA Balance and Falls Special Interest Group. For more information, contact .