From The Ergoweb® Learning Center

Is That Ball Ergonomic?

In last week’s Ergonomics Roundup I posed the question of what makes a product "ergonomic," or "ergonomically designed." Today I came across another example that brings that question to mind … exercise balls. In an article titled "Are Exercise Balls Ergonomic?," Liz Thomas writes:

Exercise balls can be a fun and low impact way to get in shape, but there has been a bit of a debate concerning the claims of the ergonomics of exercise balls. Some people claim they are a great alternative to even ergonomic desk chairs, while others say that they are not ergonomic and cannot solve posture and pain problems. Read the full article …

This isn’t the first time Ergoweb has covered this topic, and I’d bet Thomas read some of our materials as she prepared her own article. In fact, the most popular article on our web site is Opinion: Balls as Office Chairs a Bad Idea, which we published in 2005. Roughly 5,000 readers per month, month after month, access this article. Google, Wikipedia and Bing alone sent some 40,000 searchers to read it in the past year. (You can also read many other articles and Ergoweb Forum discussions on that touch on the balls-as-chairs topic.)

So, are exercise balls ergonomic?

Well, it depends. First, it depends on what we mean by "ergonomic." We could debate that question ad infinitum, but after reviewing numerous definitions let me suggest that no matter how we specifically define it, there are at least these elements to any credible definition: design for human well-being and system performance, or some close variation on that theme.

That is, to be ergonomic, something must have design features that maintain or enhance human well-being and performance within its context of use — the system.

So far, so good, but how might we go about objectively evaluating something? What metrics would, could or should be used? What metrics capture "human well-being?" How about "system performance?" If we were asked to evaluate a product, I propose we would need measures for at least the following:

Human Well-Being:

  • Physical health, safety and performance
  • Psychological fulfillment and performance

System Performance:

  • Productivity
  • Quality
  • Reliability

I’ll leave the specifics of how we might measure such attributes for another time, since this is a complicated subject in itself. Metrics and measurement methodology aside, there are a series of questions that must be considered in our evaluation.

Question 1: What is the intended use?

Question 2: What is the intended outcome?

Question 3: Who is the intended user?

Question 4: What is the intended context of use?

Question 5: Within these constraints, does it maintain or enhance human well-being and system performance?

I’m trying to keep this simple in order to illustrate the basics of the evaluation process, but in practice, these questions should go beyond intended uses/users/contexts to include foreseeable, even if not intended, uses/users/contexts, as well.

Now, let’s walk through these questions using an exercise ball as the example (this is not meant to represent any specific exercise ball).

Intended Use:

To support the human body in various postures while performing exercise

Intended Outcome:

Improved core strength and balance

Intended User:

Anyone aged 16-70 years, weighing no more than 250 lb.

Intended Context of Use:

Supervised medical rehabilitation and health club environments

If we were to evaluate this device, we should require evidence that it actually improves core strength and balance among people within the target user population when used within the supervised medical and health club environments. And at a minimum, we would also require evidence that it is safe and effective for use within these constraints. We might also evaluate whether supervisory staff are properly trained, whether product accompanying materials adequately inform users of the constraints, and so on. Using this simplified example, I can see how an exercise ball might pass as being ergonomic — within well defined constraints – as a device to assist with improving core strength and balance under supervised conditions.

But what happens when a manufacturer or promoter of the exercise ball tells people that the ball can also serve as an ergonomic chair suitable for use in computer workstations? What qualities/features does a chair — any chair — need in order to be considered ergonomic? Well, it depends on our constraints, as always, and since a computer task chair is part of a system (e.g., desk, computer and workstation accessories), that system introduces additional constraints.

What if the constraints were as broad as:

Intended Use:

To support the human body in a seated position while performing any task at any computer workstation

Intended Outcome

Improved core strength and balance, reduced lower back pain

Intended User:

Any person, of any height or weight, in any physical condition

Intended Context of Use:

Any computer task in any environment

Research and experience tells us that without some form of adjustability, most people will not be able to acheive an effective fit with their computer workstation, so I’ll emphatically say "no, a ball used within these constraints is not ergonomic," even if some users do report improved core strength, balance, or reduced low back pain. It’s very likely that other users, probably a majority of users, will not find these benefits, and may in fact encounter many challenges and problems while using the ball as a chair.

What if the constraints were:

Any person between 5′ 0" and 6′ 4" tall, weighing no more than 250 lb., sitting at a workstation with adjustable worksurface and monitor heights.

These constraints move toward a better fit, but are still a long way from making the ball ergonomic when used as a computer task chair.

What if my target constraints were:

Any healthy, able-bodied person who is 5′ 8" tall, weighing 180 lb., sitting on the ball at a workstation with keyboard height set at or near seated resting elbow height and the top of the monitor height set at or below seated eye height, who is personally motivated and properly trained to maintain or improve core strength and balance while using the ball, and sits on the ball for no more than 1-2 hrs at a time.

In other words, could the ball be ergonomic, at least in terms of working heights, for a specific person using it for short durations? Perhaps, but there are other chair features that come into play (e.g., seat pan size, stability, not to mention other features like backrests and armrests), so even under tight constraints, a ball could still have a hard time passing as ergonomic.

Does this mean that no one should ever sit on a ball while working at a computer? Of course not; it only means that a ball is not likely to pass as ergonomic seating for the general population, that only a subset of the population will acheive well-being and enhanced system performance, and that individuals and organizations should exercise caution if considering the use of such devices. Yes, a ball might be ergonomic for some subset of the population under certain conditions and constraints, but it is not, in and of itself, ergonomic.

Read the comments from satisfied ball sitters at the end of our article, Opinion: Balls as Office Chairs a Bad Idea, and you’ll see some very strong feelings on the subject. Some people swear by them, and in the end, user experience is yet another important criteria we should consider when asking the question, "is it ergonomic." But, user experience feedback and popularity alone cannot define ergonomics; there must also be objective standards. Just because something is popular, or that it produces some "good" outcomes for some people, doesn’t mean it’s ergonomic.

The "is it ergonomic?" topic concerns me greatly. I feel the general public has a limited understanding of ergonomics, not because people are stupid, but because our profession has remained relatively quiet while others with little or no understanding of ergonomics continue to trumpet the word in confusing, questionable, and sometimes unsavory ways. It’s even hard to criticize those who misuse the term, because we’ve apparently done a poor job educating, influencing and setting the bar for ergonomics. It’s time we change that.

This article was last modifed May 20, 2010, 2:38 PM, EST

This article originally appeared in The Ergonomics Report™ on 2010-05-19.