{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,9]],"date-time":"2025-12-09T15:43:36Z","timestamp":1765295016497,"version":"3.37.3"},"reference-count":43,"publisher":"American Physiological Society","issue":"4","funder":[{"DOI":"10.13039\/501100000925","name":"Department of Health, Australian Government | National Health and Medical Research Council (NHMRC)","doi-asserted-by":"publisher","award":["GTN1029782","GTN1029782"],"award-info":[{"award-number":["GTN1029782","GTN1029782"]}],"id":[{"id":"10.13039\/501100000925","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Neurophysiology"],"published-print":{"date-parts":[[2019,4,1]]},"abstract":"<jats:p> Studies on anesthetized animals have revealed that nociceptors can excite fusimotor neurons and thereby change the sensitivity of muscle spindles to stretch; such nociceptive reflexes have been suggested to underlie the mechanisms that lead to chronic musculoskeletal pain syndromes. However, the validity of the \u201cvicious cycle\u201d hypothesis in humans has yielded results contrasting with those found in animals. Given that spindle firing rates are much lower in humans than in animals, it is possible that some of the discrepancies between human experimental data and those obtained in animals could be explained by differences in background fusimotor drive when the leg muscles are relaxed. We examined the effects of tonic muscle pain during voluntary contractions of the ankle dorsiflexors. Unitary recordings were obtained from 10 fusimotor-driven muscle spindle afferents (6 primary, 4 secondary) supplying the ankle dorsiflexors via a microelectrode inserted percutaneously into the common peroneal nerve. A series of 1-min weak contractions was performed at rest and during 1 h of muscle pain induced by intramuscular infusion of 5% hypertonic saline into the tibialis anterior muscle. We did not observe any statistically significant increases in muscle spindle firing rates of six afferents followed during tonic muscle pain, although discharge variability increased slightly. Furthermore, a participant\u2019s capacity to maintain a constant level of force, while relying on proprioceptive feedback in the absence of visual feedback, was not compromised during pain. We conclude that nociceptive inputs from contracting muscle do not excite fusimotor neurons during voluntary isometric contractions in humans. <\/jats:p><jats:p> NEW &amp; NOTEWORTHY Data obtained in the cat have shown that muscle pain causes a marked increase in the firing of muscle spindles, attributed to a nociceptor-driven fusimotor reflex. However, our studies of muscle spindles in relaxed leg muscles failed to find any effect on spindle discharge. Here we showed that experimental muscle pain failed to increase the firing of muscle spindle afferents during weak voluntary contractions, when fusimotor drive sufficient to increase their firing is present. <\/jats:p>","DOI":"10.1152\/jn.00862.2018","type":"journal-article","created":{"date-parts":[[2019,1,30]],"date-time":"2019-01-30T14:36:16Z","timestamp":1548858976000},"page":"1143-1149","source":"Crossref","is-referenced-by-count":7,"title":["Effects of tonic muscle pain on fusimotor control of human muscle spindles during isometric ankle dorsiflexion"],"prefix":"10.1152","volume":"121","author":[{"given":"Lyndon J.","family":"Smith","sequence":"first","affiliation":[{"name":"School of Medicine, Western Sydney University, Sydney, New South Wales, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3325-6566","authenticated-orcid":false,"given":"Vaughan G.","family":"Macefield","sequence":"additional","affiliation":[{"name":"School of Medicine, Western Sydney University, Sydney, New South Wales, Australia"},{"name":"Neuroscience Research Australia, Sydney, New South Wales, Australia"},{"name":"Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ingvars","family":"Birznieks","sequence":"additional","affiliation":[{"name":"Neuroscience Research Australia, Sydney, New South Wales, Australia"},{"name":"School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia"},{"name":"School of Science and Health, Western Sydney University, Sydney, New South Wales, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alexander R.","family":"Burton","sequence":"additional","affiliation":[{"name":"School of Medicine, Western Sydney University, Sydney, New South Wales, Australia"},{"name":"Neuroscience Research Australia, Sydney, New South Wales, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"24","reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1997.82.6.1811"},{"key":"B2","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1998.84.6.1827"},{"key":"B3","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1983.sp014533"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0035091"},{"key":"B5","first-page":"21","author":"Birznieks I","year":"2008","journal-title":"Physiol News"},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.2008.151746"},{"key":"B7","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1979.sp012812"},{"key":"B8","doi-asserted-by":"publisher","DOI":"10.3389\/fneur.2016.00109"},{"key":"B9","doi-asserted-by":"publisher","DOI":"10.1016\/j.archoralbio.2006.10.011"},{"key":"B10","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00066.2004"},{"key":"B11","doi-asserted-by":"publisher","DOI":"10.1016\/0168-0102(95)00906-A"},{"key":"B12","doi-asserted-by":"publisher","DOI":"10.1152\/jn.1990.63.6.1314"},{"key":"B13","doi-asserted-by":"publisher","DOI":"10.1113\/expphysiol.2012.071670"},{"key":"B14","doi-asserted-by":"publisher","DOI":"10.1093\/brain\/113.5.1563"},{"key":"B15","doi-asserted-by":"publisher","DOI":"10.1016\/j.jpain.2011.02.356"},{"key":"B16","doi-asserted-by":"publisher","DOI":"10.1016\/j.jpain.2008.06.012"},{"key":"B17","doi-asserted-by":"publisher","DOI":"10.1016\/0168-0102(93)90008-E"},{"key":"B18","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1986.sp016110"},{"key":"B19","doi-asserted-by":"publisher","DOI":"10.1016\/0168-0102(90)90057-L"},{"key":"B20","doi-asserted-by":"publisher","DOI":"10.1016\/0306-9877(91)90233-O"},{"key":"B21","doi-asserted-by":"publisher","DOI":"10.1016\/0006-8993(90)91528-O"},{"key":"B22","doi-asserted-by":"publisher","DOI":"10.1007\/978-1-4615-0713-0_4"},{"key":"B23","first-page":"I60","volume":"61","author":"Kaufman MP","year":"1987","journal-title":"Circ Res"},{"key":"B24","doi-asserted-by":"publisher","DOI":"10.1067\/mmt.2000.109674"},{"key":"B25","doi-asserted-by":"publisher","DOI":"10.1002\/(SICI)1097-4598(199911)22:11<1564:AID-MUS12>3.0.CO;2-3"},{"key":"B27","doi-asserted-by":"publisher","DOI":"10.1007\/s00421-014-3036-1"},{"key":"B28","doi-asserted-by":"publisher","DOI":"10.1139\/y91-102"},{"key":"B29","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1993.sp019908"},{"key":"B30","doi-asserted-by":"publisher","DOI":"10.1152\/jn.00071.2018"},{"key":"B31","doi-asserted-by":"publisher","DOI":"10.1053\/eujp.2002.0332"},{"key":"B32","doi-asserted-by":"publisher","DOI":"10.1016\/S0304-3959(98)00012-8"},{"key":"B33","doi-asserted-by":"publisher","DOI":"10.1016\/0006-8993(83)91367-7"},{"key":"B34","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1988.64.6.2306"},{"key":"B35","doi-asserted-by":"publisher","DOI":"10.1016\/S0304-3959(97)00102-4"},{"key":"B36","doi-asserted-by":"publisher","DOI":"10.3758\/BF03206496"},{"key":"B37","doi-asserted-by":"publisher","DOI":"10.1007\/s00221-005-0225-5"},{"key":"B38","doi-asserted-by":"publisher","DOI":"10.1002\/(SICI)1097-4598(199811)21:11<1382:AID-MUS4>3.0.CO;2-5"},{"key":"B39","doi-asserted-by":"publisher","DOI":"10.1007\/s00221-001-0941-4"},{"key":"B40","doi-asserted-by":"publisher","DOI":"10.1016\/j.humov.2007.07.001"},{"key":"B41","doi-asserted-by":"publisher","DOI":"10.1523\/JNEUROSCI.5211-08.2009"},{"key":"B42","doi-asserted-by":"publisher","DOI":"10.1152\/jn.00718.2005"},{"key":"B43","doi-asserted-by":"publisher","DOI":"10.1007\/s00221-002-1081-1"},{"key":"B44","doi-asserted-by":"publisher","DOI":"10.1016\/S0003-9969(00)00137-0"}],"container-title":["Journal of Neurophysiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.physiology.org\/doi\/pdf\/10.1152\/jn.00862.2018","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2019,9,21]],"date-time":"2019-09-21T23:45:53Z","timestamp":1569109553000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.physiology.org\/doi\/10.1152\/jn.00862.2018"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,4,1]]},"references-count":43,"journal-issue":{"issue":"4","published-print":{"date-parts":[[2019,4,1]]}},"alternative-id":["10.1152\/jn.00862.2018"],"URL":"https:\/\/doi.org\/10.1152\/jn.00862.2018","relation":{},"ISSN":["0022-3077","1522-1598"],"issn-type":[{"type":"print","value":"0022-3077"},{"type":"electronic","value":"1522-1598"}],"subject":[],"published":{"date-parts":[[2019,4,1]]}}}