On Using Abled-Bodied Subjects in Wheelchair Propulsion Research – Erik Kondo

Example of Able-bodied Subject in Wheelchair Propulsion Research

If you can walk in typical fashion, I would like you to imagine what it would be like to walk without having control of your trunk muscles.  Assume that you have no control of your abdominals and lower back. How would you walk? What would it feel like? Take a moment…

I think it is safe to assume that you have no idea of what it would be like. How could you imagine something that is so far from your actual experience? How do you simulate not using muscles that you use unconsciously and literally form the core of your upright posture?

Now imagine that you are an able-bodied researcher of wheelchair propulsion. You want to study how wheelchair users with spinal cord injury propel their wheelchairs. What do you do? If you are like the majority of researchers, you recruit able-bodied participants and put them in simulated wheelchairs in a laboratory environment to perform your experiments.

With our previous thought experiment, we have determined that it is not possible to simulate or imagine lack of trunk stability for walking, so why would propelling a wheelchair be any different? How could an able-bodied person simulate lack of trunk stability for wheelchair propulsion? The truth is that they can’t.

An able-bodied person cannot simulate the propulsion movements of someone lacking in trunk control. As a paraplegic, I cannot simulate the propulsion of a person with cervical level spinal cord injury who lacks triceps or full hand function. I don’t know how to NOT use my triceps for propulsion. I cannot turn them off at will.

This concept is straightforward. Able-bodied people who don’t need to use wheelchairs will propel a wheelchair in a different manner than people who must use wheelchairs due to a physical disability. 

People with different physical disabilities will propel a wheelchair differently due the varying effects of their disability. Amputees and low level paraplegics propel wheelchairs differently than high level paraplegics who propel wheelchairs differently than low level quadriplegics who propel differently than higher level quadriplegics. Therefore, even if the research subjects are all people with disabilities, the data should not be comingled into a single class due to the vast differences between the disabilities.

When a person without trunk control sits in their wheelchair, they are at risk of falling forward at any given time. Even if it doesn’t look like that is the case. Whereas a person with full trunk can lean forward without falling and pick up weighted objects and return to their upright sitting position. Their upper body doesn’t “fall” forward, backwards, or sideways. They have inherent stability. On the other hand, a person without trunk control is balanced like a book sitting alone on a shelf. It takes very little for it to fall over.

A person without trunk control is constantly using their arms to “catch” themselves from falling. This act of catching is integrated with their propulsion movements. It determines their propulsion technique at any given time due to the off-balancing influence of the terrain the wheelchair user is encountering.

Given all that I have said, why do able-bodied researchers use able-bodied participants for their studies? The obvious answer is that is it more convenient to find able-bodied subjects. I agree. But I think there is more to it than that.

I think the researchers don’t understand wheelchair use sufficiently to realize the effect that lack of trunk control has on wheelchair propulsion in the real world. They don’t understand how much the laboratory environment differs from the actual conditions faced by wheelchair users.

Why is this the case? Because they don’t use wheelchairs. And they don’t bother to consult with knowledgeable wheelchair users. They assume they know, when they don’t. They don’t know what they don’t know.

The results of their flawed research are typically passed on to medical practitioners, who also don’t use wheelchairs. Eventually, the questionable (or outright wrong) conclusions become the basis of “evidence based practice” for wheelchair seating clinics around the world.

There is a simple solution to this problem. Design wheelchair propulsion research with the consultation of knowledgeable wheelchair users and recruit actual wheelchair users as research study participants.