Accessible Exterior Surfaces Technical Article

EXPLANATION OF STUDY DESIGN

What was measured and why?

Energy Consumption – Measuring the oxygen a person consumes indicates how much energy the body is producing. When the oxygen consumption is measured at rest (i.e., with the person sitting or lying down), the amount of energy the body is using to function (e.g., for making the heart pump, organs function) can be determined. If an individual walks at a steady pace for 3 to 4 minutes, energy consumption will stabilize at a level that is equal to the energy required to negotiate that environment. By subtracting the resting oxygen consumption from the oxygen consumption while walking/wheeling, the amount of energy being used specifically for walking can be determined.

Walking Speed – If adults are asked to walk at their freely chosen speed they automatically select the type of movement and speed that requires the least amount of energy. If an individual is forced to walk either faster or slower than this chosen pace, the amount of energy used will increase. Therefore, f or this study, subjects were allowed to determine their own preferred pace so that energy consumption in its “most efficient” state could be measured.

Heart Rate and Rating of Perceived Exertion – Rating of perceived exertion (RPE) is a research scale used to document the individual’s perception of how difficult it is for his/her body to perform an exercise (i.e., how hard the individual’s lungs are breathing, and heart is pumping). RPE scores have been shown through research to be consistently related to measures of heart rate and amount of exercise, regardless of the type of exercise. In general, the RPE score is equal to the steady state heart rate divided by 10.

Level of Difficulty – Level of difficulty is similar to the rating of perceived exertion in that it attempts to quantify the individual’s subjective perception of the activity. However, it differs from the rating of perceived exertion in that it is not specific to how the heart and lungs are performing. Often, an unstable surface, for example, may be perceived as very difficult because of the unstable footing, even though the individual does not have to exert him/herself. Level of difficulty was recorded to evaluate factors (e.g., ease of slipping, uneven surfaces) that would not necessarily affect the energy consumption but may impact the overall “accessibility” of the surface.

Why test on straight courses and P-shaped turning courses? Constructing long test courses enables comparison of subject data with research done by other investigators in which subjects walk on a straight linear course or in large diameter circles or ovals. However, the cost for producing these course designs with a number of surface materials would be very large. As a compromise, the construction of two long courses enabled some comparisons with published research without generating prohibitive surface construction costs. In this study, there was also a desire to have the subjects walk on the test surfaces in a manner that would reflect the types of ambulation that would represent functional mobility. This functional mobility includes both turning and walking in a straight path on any given surface. The “P” courses were designed so that the subject was turning for approximately 10% of the total distance.

What happens when people walk under more difficult conditions? In general, when people walk under more difficult conditions there is: 1) a decrease in speed (to decrease the energy required), 2) an increase in heart rate (to pump more oxygen to the muscles), and/or 3) an increase in total energy consumption (when the other compensating mechanisms are not sufficient).

Which surfaces are accessible to everyone? There are no surfaces that are accessible to everyone, because there is an infinite range of abilities among the population. Participants in this study were recruited to represent a variety of disabilities. They completed standard tests of fitness to ensure that a variety of ability levels was represented. Currently, our society has made a decision on what is considered “sufficiently accessible,” that being environments that comply with the current ADAAG. Although it is recognized that not all individuals have independent access in an ADAAG environment, these standards have been designated “accessible enough” for most people. It should be noted that all powered mobility technologies are able to negotiate ADAAG environments and represent an option for persons without the functional mobility to negotiate these environments.