Reliability of the manual dynamic mode of the Baltimore Therapeutic Equipment Work Simulator

Twelve Baltimore Therapeutic Equipment Work Simulators (BTEWS) were tested for consistency of resistance in the manual dynamic mode using a previously described timed weight-drop test. Fifty weight-drop measurements were made at five different weight levels: 5, 10, 20, 30, and 40 lb. Alterations in weight-drop times indicate changes in exercise-head resistance. Substantial resistance variation was found in the manual dynamic mode. With console resistance set consistently at 92% of applied weight, weight-drop times varied from failures of the weight to drop to times that were not recognized by the electronic timing system. Measurable weight-drop times ranged from 0.75 to 16.97 seconds. Ten Simulators had weight-drop times greater than +/-3 standard deviations (SD) from the mean; eight Simulators had times +/-4 SD from the mean; and four had times +/-5 SD from the mean. Console printout data did not accurately reflect resistance produced by the exercise head. While intermachine correlations based on Simulator printout data ranged from +1.0 to +0.9906, correlations derived from resistance-based weight-drop times ranged from +0.9866 to -0.9956. For a constant externally applied torque, the weight-drop times should have been constant but were not. Resistance produced in the manual dynamic mode is inconsistent, both within and between machines (p = 0.0001).