Timoszyk Wojciech K, Nessler Jeff A, Acosta Cynthia, Roy Roland R, Edgerton V Reggie, Reinkensmeyer David J, de Leon Ray
Department of Mechanical and Aerospace Engineering, 4200 Engineering Gateway (EG3225), University of California, Irvine, CA 92697-3975, USA.
Brain Res. 2005 Jul 19;1050(1-2):180-9. doi: 10.1016/j.brainres.2005.05.041.
We compared the bipedal hindlimb stepping ability of untrained and trained (step-trained 6 min/day) spinal rats (mid-thoracic spinal cord transection at post-natal day 5) at different levels of body weight support on a treadmill over a 40-day period, starting at 69 days of age. A robotic device provided precise levels of body weight support and recorded hindlimb movement. We assessed stepping ability using: (1) step quantity determined from the measured hindlimb movement, (2) ordinal scales of paw placement, weight-bearing, and limb flexion, and (3) the lowest level of body weight support at which stepping was maintained. Stepping quantity and quality depended strongly on the level of support provided. Stepping ability improved with time, but only at the higher levels of weight-bearing, and independently of training. Increasing limb loading by gradually decreasing body weight support altered the spatiotemporal properties of the steps, resulting in an increase in step length and stance duration and a decrease in swing and step cycle duration. The rats progressively improved their ability to support more load before collapsing from a maximum of about 42 g ( approximately 25% of body weight) at Day 1 to 73 g ( approximately 35% of body weight) at Day 40. We conclude that the level of hindlimb loading provided to a spinally transected rat strongly influences the quantity and quality of stepping. Furthermore, the relationship between stepping ability and loading conditions changes with time after spinal cord transection and is unaltered by small amounts of step training. Finally, load-bearing failure point can be a quantitative measure of locomotor recovery following spinal cord injury, especially for severely impaired animals that cannot step unassisted.
我们比较了未训练和经训练（每天进行6分钟阶梯训练）的脊髓损伤大鼠（出生后第5天进行胸段脊髓横断）在跑步机上不同体重支撑水平下的双足后肢行走能力，实验从69日龄开始，为期40天。一个机器人装置提供精确的体重支撑水平并记录后肢运动。我们使用以下方法评估行走能力：（1）根据测量的后肢运动确定的步数；（2）爪放置、负重和肢体屈曲的序数量表；（3）维持行走时的最低体重支撑水平。步数和步质在很大程度上取决于所提供的支撑水平。行走能力随时间改善，但仅在较高负重水平下，且与训练无关。通过逐渐降低体重支撑来增加肢体负荷会改变步的时空特性，导致步长和站立时间增加，摆动和步周期时间减少。大鼠在崩溃前支撑更多负荷的能力逐渐提高，从第1天的最大约42克（约占体重的25%）增加到第40天的73克（约占体重的35%）。我们得出结论，给予脊髓横断大鼠的后肢负荷水平强烈影响行走的数量和质量。此外，脊髓横断后，行走能力与负荷条件之间的关系随时间变化，且少量阶梯训练不会改变这种关系。最后，承重失败点可以作为脊髓损伤后运动恢复的定量指标，特别是对于严重受损无法独立行走的动物。
