The Role of Neural Tension in Stretch-Induced Strength Loss

The purpose of this study was to determine if neural tension during passive stretching affected subsequent strength loss. Eleven healthy subjects (10 men, 1 woman; age 34 ± 12 years) performed maximal isometric hamstring contractions at 100°, 80°, 60°, and 40° knee flexion before and after five 1-minute hamstring stretches performed in either a spinal neutral position or a neural tension position. One leg was stretched in the neutral position and the other in the neural tension position. Hamstring electromyography (EMG) activity was recorded during all contractions and stretches. Passive resistance to stretch was reduced by 11% after stretching (p <0.01; no difference between neutral or neural tension stretches p = 0.41). Stretch-induced strength loss was apparent after neural tension stretches (12%, p <0.01) but not after neutral stretches (5%, p = 0.09). There was a rightward shift in the angle-torque curve after neutral stretches (strength loss on ascending limb, strength gain on descending limb, p <0.01). This effect was not apparent after neural tension stretches (p = 0.43). Stretching did not affect EMG activity during isometric contractions (