Paraplegics cannot walk in the manner they used to before the onset of spinal cord injury, because they have lost the power in the lower extremities that is essential for a normal bipedal gait. Yet paraplegics can regain their walking ability by using two crutches and long leg braces after having had appropriate physical therapy. Here the problem arises. Most paraplegics choose not to continue crutch ambulation but prefer wheelchair ambulation, at some time after being discharged from rehabilitation hospitals. We postulated that the crutch swing-through gait is very unlike the normal bipedal gait. So it is very difficult for any adult to master this mode of locomotion. To explain this assumption, we conducted energy cost measurement of the crutch swing-through ambulation. We did not adopt the conventional O_2 consumption method, but used a mathematical link model analysis. We followed the method that we reported previously, in which we calculated leg muscle power and energy consumption in normal bipedal gait. This consists of measurement of trajectories of landmarks placed on the body, floor reaction forces, and foot and floor contact timing. For the link and source of power for crutch ambulation, we reduced human body to 5 segments and 9 muscles on one side of the body. Weight and center of the mass of each segment were measured by a technique that processes a graphical image of body shape, which we have reported previously. The maximum strength of 9 muscles was measured by a strain gauge appliance and a Cybex machine. All data were fed into an NEC9801RX computer to obtain contraction speed and length of each muscle during crutch ambulation. These parameters were used to compute muscle strength and power using Hill's equation. Energy consumption per unit of time was obtained by integrating muscle power. We used a non-paraplegic subject (23years old, 172cm height, 63kg body weight), who simulated paraplegic swing-through ambulation at 3 different speeds. The results were as follows. At 42.0m/min walking speed, energy consumption per minute was 76.5 (cal/kg/min), permeterwas 1.74 (cal/kg/m). At 57.6m/min walking speed, energy consumption per minute was 70.3 (cal/kg/min), per meter was 1.22 (cal/kg/m). At 61.2m/min walking speed, energy consumption per minute was 64.4 (cal/kg/min), and that per meter was 1.10 (cal/kg/m). These results agreed with those of other workers who measured energy consumption of paraplegic walk by conventional technique. Paraplegics use shoulder girdle depressors, elbow extensors and shoulder flexors for this mode of locomotion. Unless these muscles are strengthened, it seems difficult to master the swing-through ambulation.
