Griffin Lisa, Godfrey Sharlene, Thomas Christine K
The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami School of Medicine, Miami, Florida 33136, USA.
J Neurophysiol. 2002 May;87(5):2271-8. doi: 10.1152/jn.2002.87.5.2271.
The pattern of seven pulses that elicited maximal thenar force was determined for control muscles and those that have been paralyzed chronically by spinal cord injury. For each subject group (n = 6), the peak force evoked by two pulses occurred at a short interval (5-15 ms; a "doublet"), but higher mean relative forces were achieved in paralyzed versus control muscles (41.4 +/- 3.9% vs. 22.7 +/- 2.0% maximal). Thereafter, longer intervals evoked peak force in each type of muscle (mean: 35 +/- 1 ms, 36 +/- 2 ms, respectively). With seven pulses, paralyzed and control muscles reached 76.4 +/- 5.6% and 57.0 +/- 2.6% maximal force, respectively. These force differences resulted from significantly greater doublet/twitch and doublet/tetanic force ratios in paralyzed (2.73 +/- 0.08, 0.35 +/- 0.03) compared with control muscles (2.07 +/- 0.07, 0.25 +/- 0.01). The greater force enhancement produced in paralyzed muscles with two closely spaced pulses may relate to changes in muscle stiffness and calcium metabolism. Peak force-time integrals were also achieved with an initial short interpulse interval, followed by longer intervals. The postdoublet intervals that produced peak force-time integrals in paralyzed and control muscles were longer than those for peak force, however (77 +/- 3 ms, 95 +/- 4 ms, respectively). These data show that the pulse patterns that maximize force and force-time integral in paralyzed muscles are similar to those that maximize these parameters in single motor units and various whole muscles across species. Thus the changes in neuromuscular properties that occur with chronic paralysis do not strongly influence the pulse pattern that optimizes muscle force or force-time integral.
确定了能引发最大鱼际肌力量的七个脉冲模式，用于对照肌肉以及因脊髓损伤而长期瘫痪的肌肉。对于每个受试者组（n = 6），两个脉冲诱发的峰值力量出现在较短的间隔（5 - 15毫秒；一个“双峰”），但与对照肌肉相比，瘫痪肌肉达到的平均相对力量更高（分别为最大力量的41.4 +/- 3.9%和22.7 +/- 2.0%）。此后，较长的间隔在每种类型的肌肉中诱发峰值力量（平均分别为35 +/- 1毫秒、36 +/- 2毫秒）。使用七个脉冲时，瘫痪肌肉和对照肌肉分别达到最大力量的76.4 +/- 5.6%和57.0 +/- 2.6%。这些力量差异是由于与对照肌肉（2.07 +/- 0.07，0.25 +/- 0.01）相比，瘫痪肌肉中双峰/单收缩和双峰/强直力量比显著更大（2.73 +/- 0.08，0.35 +/- 0.03）。两个紧密间隔的脉冲在瘫痪肌肉中产生的更大力量增强可能与肌肉僵硬度和钙代谢的变化有关。峰值力量 - 时间积分也是在初始短脉冲间隔后，接着是较长间隔时实现的。然而，在瘫痪肌肉和对照肌肉中产生峰值力量 - 时间积分的双峰后间隔比产生峰值力量的间隔更长（分别为77 +/- 3毫秒、95 +/- 4毫秒）。这些数据表明，使瘫痪肌肉中力量和力量 - 时间积分最大化的脉冲模式与使跨物种的单个运动单位和各种整块肌肉中的这些参数最大化的脉冲模式相似。因此，慢性瘫痪时发生的神经肌肉特性变化不会强烈影响优化肌肉力量或力量 - 时间积分的脉冲模式。
