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. 2022 Sep 6;10(17):e15365. doi: 10.14814/phy2.15365

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© 2022 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.

This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Correlation between plasma β‐endorphin and quantitative sensory tests in patients with chronic nonspecific low back pain. The competitive ELISA technique indicates that the lower the value of β endorphin (pg), the higher the concentration of plasma β endorphin in the sample. The graphs show a Pearson correlation between plasma β endorphin and: (a) Temporal summation; (b) PPT measured at L3; (c) PPT measured at L5; (d) PPT measured in tibialis anterior; (e) CPM before conditioning stimulus; (f) CPM during the conditioning stimulus; (g) CPM after conditioning stimulus. CPM, conditioned pain modulation; CS, conditional stimulus; PPT, pressure pain threshold; TS, temporal summation of pain.