Seating and Positioning Series

Up & At ’Em

The Physics & Benefits of Standing for Wheelchair Users

• By Laurie Watanabe
• Apr 01, 2010

An 8-month-old baby — feet widely planted, his little hands gripping the edge of the sofa — laboriously pulls himself upright for the first time. Even as he wobbles and clutches that sofa for dear life, he also dares to survey this newly revealed landscape: I’m so tall! Everything looks so different from up here! And he grins.

People who can stand up independently mostly do so without thinking much about it. But moving from sitting to standing, then maintaining a standing position, involves complex physics and can impact a number of different physical, cognitive and social functions for the better.

While wheelchair users may not be able to stand independently or move independently from sitting to standing, many can benefit from incorporating standing into their mobility routines.

The Science of Standing

Within a few months of learning to stand, babies are so adept that they move on to other adventures, such as learning how to walk.

But from a physics perspective, moving from sitting to standing is a complex, wholly impressive act requiring significant weight shifting and balance.

“As a person transitions from sitting to standing, the pressure transfers off of their sitting bones (ischial tuberosities), primarily to their feet and knees,” explains Amy Meyer, PT, ATP, Permobil’s pediatric and standing specialist. “The biggest change when moving from a seated to a standing position is the total body extension.”

That weight shift to the legs and feet is accompanied by “an opening of the thoracic area, with the hips over the knees and feet, and the shoulders and head over the pelvis,” says Nancy Perlich, COTA, ATP, funding& product development specialist for Altimate Medical.

As for the balance needed, Lori Potts, PT, Rifton, describes the sit-tostand movement as “weight-bearing through legs and pelvis with anterior-tilt pelvis and forward lean of trunk.” Simultaneously, the person needs to “maintain balance of the body’s center of gravity over the base of support during extension of knees and hips, as the body progresses to an upright stance.”

But the process of standing is different for the wheelchair client, Meyer notes.

“A standing wheelchair moving from the seated to standing position is not the same as how an able-bodied individual would complete this transition,” she says. “When an able-bodied person transfers from sit to stand, typically the trunk flexes forward, shifting weight forward to create momentum and a mechanical advantage. The extensor muscles then counteract this forward momentum, keeping the body balanced in an upright position. From there, the flexor, extensor and rotational muscle groups are working together to keep the body stable and balanced. In a mechanical standing device, the backrest angle typically either remains upright throughout the standing process or is slightly reclined — depending on individual preference or what the standing device is capable of.”

Says Altimate Medical Product Development Manager Wes Ovre, “When an able-bodied person rises from a chair to the standing position, the torso is moved forward to change the center of gravity so that the body’s muscles can overcome the weight of the body to accomplish the standing motion. In a standing frame, the user cannot use all of these same muscles, so this center-of-gravity shift is not necessary. The torso remains more or less vertical, which is an added benefit to help the user maintain their spatial orientation. The fear of falling forward is dispelled by providing the back support and remaining in a vertical position.”

The Many Benefits of Standing

Research — including a RESNA position paper on wheelchair standing devices — has discussed many physical benefits to be gained by standing.

“When sitting all day, you have increased risk of hip/knee flexion contractures, your vital organ capacity is reduced, and you are not getting the benefit of lower-extremity weight-bearing for bone health,” Meyer says. “When a person stands, they experience range of motion in the lower extremities (stretching hamstrings and hip flexors); improved lung capacity for better/easier breathing; gravity-assisted GI (gastrointestinal) motility assisting with bowel function and possibly reducing reflux; (and) better bladder emptying, lowering the risk of urinary tract infections.”

“The human body in terms of both musculoskeletal and systemic health has a notable advantage in relation to gravity when in the upright position,” Potts notes.

She says those advantages can include preventing contractures in ankles, knees and hips; reducing spasticity; preventing or reversing osteoporosis and resultant hypercalciuria; preventing pressure ulcers and alleviating pain through change of position; improving circulation as it relates to orthostatic hypotension; developing and improving upper-body balance and strength; and increasing standing tolerance and endurance.

There are some differences between independent standing and standing in a standing frame or wheelchair. For instance, depending on the circumstances, a client in a stander would not necessarily bear his full body weight, due to the support being provided by the equipment. But the option of having the client bear less than his full body weight can be beneficial, Ovre points out.

“I would say up to 95 to 98 percent weight-bearing by the user can be attained in the right circumstances, (including) structural body type and support options,” he says. “There will be cases where a doctor or therapist may not want full weight-bearing, and this is achieved by positioning the standing frame in a partially upright stance, if that is what’s desired. More weight is borne by the combination of the seating surface and knee blocks as the user is further from being completely upright.”

Weight-bearing percentage, Meyer says, is also dependent “on the person’s motor control, the equipment options and whether or not the person can tolerate a full upright position in the device. Additional supports — i.e., lateral trunk supports, chest belts, hip/thigh guides, etc. — can be used if someone is extremely weak and needs the device to be more supportive. On the other hand, if a person is more active, certain standing devices allow the user to move more freely in the system for function.”

Who Can Benefit from Standing?

While no positioning regimen is a panacea for all seating & mobility clients, our experts said standing can potentially help people with widely ranging diagnoses and abilities.

“All individuals who do not have the opportunity to stand due to physical disability can benefit from standing regimens,” Potts says. “Depending on the design of the stander, a large variety of both physical and cognitive disabilities can be accommodated.”

She adds, “The guidance of a health professional is advised for individuals who have not had previous opportunity to stand, because prolonged periods of no standing can contribute to decreased bone mineral density (see sidebar), joint contractures and circulatory issues, such as orthostatic hypotension.”

“Most clients with diagnoses from congenital disorders, degenerative or progressive neuromuscular disease or from an injury or trauma can benefit from weight-bearing in a stander,” Perlich says. “Clinical recommendations as to the safety of weight-bearing for the individual client are necessary, as not everybody is an appropriate candidate for a standing program. Some contraindications and precautions include but are not limited to existing contractures, non-flexible skeletal deformities, osteoporosis or existing bone loss that could cause fracture, and postural hypotension.”

Meyer says most of the existing research on standing involves clients with spinal cord injuries, but “in my personal experience, I have seen a profound positive impact in standing for patients with cerebral palsy; neuromuscular conditions (muscular dystrophies/spinal muscular atrophy, etc.); multiple sclerosis, Fibrodysplasia Ossificans Progressiva (FOP), spina bifida, stroke, brain injury and many more.”

In addition to ensuring that clients will be able to physically tolerate a standing program, Meyer says safety also needs to be considered. “There are various types of standing devices,” she explains. “Some are operated independently, and others utilize a caregiver to operate the standing feature. For the standing devices that are operated independently, a client would need to demonstrate the ability to safely and effectively use the device.”

Customizing the Technology & Program to the Client’s Needs

As with any assistive technology, the use of standing frames and wheelchairs should be customized to clients’ particular needs to be optimally effective.

Says Meyer, “For instance, someone who has cerebral palsy and may use their tone or motor control to assist with their positioning in the standing device may be able to effectively use a tighter sit-to-stand movement — whereas someone with complete paralysis would be better off using a semi-reclined standing sequence or possibly even a full supine-to-stand sequence in order to allow the body to extend and remain positioned well before gravity begins to take over in upright. The supine-to-stand also helps control any abnormal cardiovascular responses that may take place when moving from a seated to a standing position.”

And, she says, “If someone has muscle control, even if it is abnormal muscle tone, they can also activate their muscles while in the weight bearing position, which will further enhance the benefits for bone density. Several studies have also recommended use of electrical stimulation to paralyzed muscle groups while standing to enhance the benefit to the skeletal system. This is a form of dynamic loading of the bones through muscle contraction.”

While Perlich says all sit-to-stand standers share the same mechanics of movement, “The effect on clients can be different for different persons — not just by diagnosis, but even within the same diagnosis, as we all have different body sizes and different needs. Thus the importance of individual assessment and trial.”

But when the standing equipment, the clinical needs of the client and the overall goals of the seating & mobility team all come together, the results can be significant.

Meyer points out that the RESNA position paper on standing also discusses improved environmental accessibility thanks to increased vertical reach, improved productivity at work or school thanks to reduced need to pause to perform pressure relief, and greater confidence from being able to interact with peers on an equal physical level.

(To download that RESNA position paper, visit the University of Pittsburgh’s Department of Rehabilitation Science and Technology Continuing Education Web site: rstce.pitt.edu/RSTCE_Resources/RSTCE_Resources.html.)

Perlich says, “Cognitive benefits include increased cognition, being more alert, enhanced social participation with peers, and eye-to-eye status. With better upper-body positioning, many find it easier to be more vocal. Standing can lift the client’s mood, which helps prevent depression.”

As parents of active toddlers know, learning how to stand ushers in a whole new realm of functional, cognitive, social and emotional possibilities. Fortunately for many wheelchair users, those same benefits and more can also be enjoyed with the upstanding support of the appropriate assistive technology.

This article originally appeared in the April 2010 issue of Mobility Management.