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The role of neural tension in stretch-induced strength loss

PainSci » bibliography » McHugh et al 2013
Tags: stretch, exercise, self-treatment, treatment, muscle

One article on PainSci cites McHugh 2013: Quite a Stretch

PainSci commentary on McHugh 2013: ?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

This was a test of the effect of stretching on hamstring stretches with and without spinal flexion, which adds “neural tension” to the hamstring stretch (by pulling on the spinal cord and big nerve roots and nerves like the sciatic nerve). After stretching with neural tension, strength dropped about 12% — quite a bit actually! The effect of regular hamstring stretching was a mixed bag, with reduced strength at short muscle lengths but boosted at long muscle lengths — a fine example of how generalizations about the effects of stretching are foolhardy.

~ Paul Ingraham

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

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 (<2% decline p = 0.58; no difference between neutral and neural tension, p = 0.86). Hamstring stretching with the spine in a neutral position did not result in a significant strength loss but shifted the length-tension relationship such that strength was decreased at short muscle lengths and increased at long muscle lengths. Hamstring stretching with increased neural tension resulted in strength loss with no associated shift in the length-tension relationship.

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