Scott Wayne B, Lee Samuel C K, Johnston Therese E, Binkley Jennifer, Binder-Macleod Stuart A
Department of Physical Therapy and Rehabilitation Science, University of Maryland, Baltimore, USA.
Phys Ther. 2006 Jun;86(6):788-99.
Following spinal cord injury (SCI), paralyzed muscles undergo physiological changes that alter their force responses to electrical stimulation. The purpose of this study was to investigate the effects of SCI on the contractile properties and force-frequency relationship (FFR) of the paralyzed human quadriceps femoris muscle of adolescents and young adults.
Thirteen subjects (11 male, 2 female; age range=11-24 years) with motor complete SCIs and 13 matched control subjects (11 male, 2 female; age range=9-23 years) without SCI participated in the study.
Both groups of subjects underwent the same testing protocol using similar equipment.
The paralyzed muscles of the subjects with SCI produced 62% of the peak twitch force and had a fatigue ratio that was 65% of that of the control subjects. The paralyzed muscles contracted 14% and 25% faster and relaxed 38% and 46% faster than the nonparalyzed muscles in nonfatigued and fatigued conditions, respectively. Compared with the control subjects, the subjects with SCI had twitch-to-tetanus ratios that were 84% and 127% greater in nonfatigued and fatigued conditions, respectively. Relative to the control subjects, the FFR of the subjects with SCI was shifted to the left in the fatigued condition. Relative to their respective nonfatigued conditions, the FFR of both groups of subjects shifted to the right with fatigue.
These findings may have important implications for designing stimulation strategies to reduce the rapid fatigue that limits the clinical efficacy of functional electrical stimulation.
脊髓损伤（SCI）后，瘫痪肌肉会发生生理变化，从而改变其对电刺激的力量反应。本研究旨在调查SCI对青少年和青年瘫痪的股四头肌收缩特性和力-频率关系（FFR）的影响。
13名运动完全性SCI患者（11名男性，2名女性；年龄范围11 - 24岁）和13名匹配的无SCI对照受试者（11名男性，2名女性；年龄范围9 - 23岁）参与了本研究。
两组受试者使用类似设备接受相同的测试方案。
SCI患者的瘫痪肌肉产生的峰值抽搐力为对照受试者的62%，疲劳率为对照受试者的65%。在非疲劳和疲劳状态下，瘫痪肌肉的收缩速度分别比未瘫痪肌肉快14%和25%，松弛速度分别快38%和46%。与对照受试者相比，SCI患者在非疲劳和疲劳状态下的抽搐与强直比分别高出84%和127%。在疲劳状态下，SCI患者的FFR相对于对照受试者向左偏移。相对于各自的非疲劳状态，两组受试者的FFR均随疲劳向右偏移。
这些发现可能对设计刺激策略以减少限制功能性电刺激临床疗效的快速疲劳具有重要意义。
