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bibliography * The PainScience Bibliography contains plain language summaries of thousands of scientific papers and others sources, like a specialized blog. This page is about a single scientific paper in the bibliography, Blazevich 2014.

Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans

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Blazevich AJ, Cannavan D, Waugh CM, Miller SC, Thorlund JB, Aagaard P, Kay AD. Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans. J Appl Physiol (1985). 2014 Sep;117(5):452–62. PubMed #24947023.
Tags: stretch, exercise, self-treatment, treatment, muscle

PainSci summary of Blazevich 2014?This page is one of thousands in the PainScience.com 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 at the bottom of the page, as often as possible. ★★★☆☆?3-star ratings are for typical studies with no more (or less) than the usual common problems. Ratings are a highly subjective opinion, and subject to revision at any time. If you think this paper has been incorrectly rated, please let me know.

For this study, several people stretched their calf muscles twice per day for three weeks (each session consisted of 4 stretches of 30 seconds). They were compared to people who did not stretch. Measurements included changes in muscle and tendon mechanics, muscle activity, and spinal motoneuron excitability. The non-stretchers didn’t change; stretch training “elicited a 19.9% increase in dorsiflexion range of motion (ROM) and a 28% increase in passive joint moment at end ROM.” However, the ROM improvement was not explained by changes in the muscle structure: “Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment (stretch tolerance).

original abstractAbstracts 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 neuromuscular adaptations in response to muscle stretch training have not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity, and spinal motoneuron excitability were examined during standardized plantar flexor stretches after 3 wk of twice daily stretch training (4 × 30 s). No changes were observed in a nonexercising control group (n = 9), however stretch training elicited a 19.9% increase in dorsiflexion range of motion (ROM) and a 28% increase in passive joint moment at end ROM (n = 12). Only a trend toward a decrease in passive plantar flexor moment during stretch (-9.9%; P = 0.15) was observed, and no changes in electromyographic amplitudes during ROM or at end ROM were detected. Decreases in H(max):M(max) (tibial nerve stimulation) were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed. Muscle and fascicle strain increased (12 vs. 23%) along with a decrease in muscle stiffness (-18%) during stretch to a constant target joint angle. Muscle length at end ROM increased (13%) without a change in fascicle length, fascicle rotation, tendon elongation, or tendon stiffness following training. A lack of change in maximum voluntary contraction moment and rate of force development at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment (stretch tolerance) and both muscle and fascicle elongation rather than changes in volitional muscle activation or motoneuron pool excitability.

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