Blackburn J Troy, Padua Darin A, Guskiewicz Kevin M
University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-8605, USA.
J Athl Train. 2008 Jan-Mar;43(1):29-36. doi: 10.4085/1062-6050-43.1.29.
Greater musculotendinous stiffness may enhance spinal stretch reflex sensitivity by improving mechanical coupling of the muscle spindle and the stretch stimulus. This heightened sensitivity would correspond with a shorter latency and higher-amplitude reflex response, potentially enhancing joint stability.
To compare spinal stretch reflex latency and amplitude across groups that differed in musculotendinous stiffness.
Static group comparisons.
Research laboratory.
Forty physically active individuals (20 men, 20 women).
INTERVENTION(S): We verified a sex difference in musculotendinous stiffness and compared spinal stretch reflex latency and amplitude in high-stiffness (men) and low-stiffness (women) groups. We also evaluated relationships between musculotendinous stiffness and spinal stretch reflex latency and amplitude, respectively.
MAIN OUTCOME MEASURE(S): Triceps surae musculotendinous stiffness and soleus spinal stretch reflex latency and amplitude were assessed at 30% of a maximal voluntary isometric plantar-flexion contraction.
The high-stiffness group demonstrated significantly greater stiffness (137.41 +/- 26.99 N/cm) than the low-stiffness group did (91.06 +/- 20.10 N/cm). However, reflex latency (high stiffness = 50.11 +/- 2.07 milliseconds, low stiffness = 48.26 +/- 2.40 milliseconds) and amplitude (high stiffness = 0.28% +/- 0.12% maximum motor response, low stiffness = 0.31% +/- 0.16% maximum motor response) did not differ significantly across stiffness groups. Neither reflex latency (r = .053, P = .746) nor amplitude (r = .073, P = .653) was related significantly to musculotendinous stiffness.
A moderate level of pretension (eg, 30%) likely eliminates series elastic slack; thus, a greater change in force per unit-of-length change (ie, heightened stiffness) would have minimal effects on coupling of the muscle spindle and the stretch stimulus and, therefore, on spinal stretch reflex sensitivity. It appears unlikely that differences in musculotendinous stiffness influenced spinal stretch reflex sensitivity when initiated from a moderate level of pretension. Consequently, differences in musculotendinous stiffness did not appear to influence dynamic joint stability with respect to reflexive neuromuscular control.
更大的肌肉肌腱僵硬度可能通过改善肌梭与牵张刺激之间的机械耦合来增强脊髓牵张反射敏感性。这种更高的敏感性将对应更短的潜伏期和更高幅度的反射反应，可能增强关节稳定性。
比较肌肉肌腱僵硬度不同的各组之间的脊髓牵张反射潜伏期和幅度。
静态组间比较。
研究实验室。
40名身体活跃的个体（20名男性，20名女性）。
我们验证了肌肉肌腱僵硬度的性别差异，并比较了高僵硬度组（男性）和低僵硬度组（女性）的脊髓牵张反射潜伏期和幅度。我们还分别评估了肌肉肌腱僵硬度与脊髓牵张反射潜伏期和幅度之间的关系。
在最大自主等长跖屈收缩的30%时评估比目鱼肌的肌肉肌腱僵硬度以及比目鱼肌脊髓牵张反射的潜伏期和幅度。
高僵硬度组的僵硬度（137.41±26.99N/cm）显著高于低僵硬度组（91.06±20.10N/cm）。然而，反射潜伏期（高僵硬度组=50.11±2.07毫秒，低僵硬度组=48.26±2.40毫秒）和幅度（高僵硬度组=0.28%±0.12%最大运动反应，低僵硬度组=0.31%±0.16%最大运动反应）在不同僵硬度组之间没有显著差异。反射潜伏期（r = 0.053，P = 0.746）和幅度（r = 0.073，P = 0.653）均与肌肉肌腱僵硬度无显著相关性。
适度的预张力水平（例如30%）可能消除串联弹性松弛；因此，单位长度变化时力的更大变化（即更高的僵硬度）对肌梭与牵张刺激之间的耦合以及对脊髓牵张反射敏感性的影响将最小。当从中等预张力水平开始时，肌肉肌腱僵硬度的差异似乎不太可能影响脊髓牵张反射敏感性。因此，就反射性神经肌肉控制而言，肌肉肌腱僵硬度的差异似乎并未影响动态关节稳定性。
