estimated percent body weight experienced at a given angle on a tilt table =
= SIN(angle in radians) * 100%
where:
• In EXCEL the angle in radians = (angle in degrees) * PI() / 180
The author compared this to a "gold standard" of having a weight scale on the foot rest of the tilt table. It would be important to select a scale that is still accurate when used at an angle. This also requires the assumption that the interaction between the subject and the tilt table is frictionless.
The author found that the estimated percent body weight tended to overestimate the value given by the weight scale. In the interval of 10 to 90 degrees, the difference in the percent estimated and the percent measured was 2.8 percent at 10 degrees, 14.2 percent at 40 degrees, and 7.3 percent at 90 degrees.
overestimation in percent at angles from 10 to 35 degrees =
= (-0.012 * ((angle)^2)) + (0.9549 * (angle)) - 4.634
overestimation in percent at angles from 35 to 90 degrees =
= (-0.002804 * ((angle)^2)) + (0.2197 * (angle)) + 9.917
actual percent body weight if you believe the scale reading =
= (estimated from SIN function) - (percent overestimated)
The fact that the scale reading at 90° was less than the actual weight indicates that some form of resistance (from straps or clothing friction) is present.
