| Implications of group III and IV muscle afferents for high-intensity endurance exercise performance in humans. | |
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MedLine Citation:
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PMID: 21878520 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We investigated the influence of group III/IV muscle afferents on peripheral fatigue, central motor drive (CMD) and endurance capacity during high-intensity leg-cycling. In a double-blind, placebo-controlled design, seven males performed constant-load cycling exercise (318 ± 9 W; 80% of peak power output (W(peak))) to exhaustion under placebo conditions and with lumbar intrathecal fentanyl impairing spinal μ-opioid receptor-sensitive group III/IV muscle afferents. Peripheral fatigue was assessed via changes in pre- vs. post-exercise quadriceps force in response to supramaximal magnetic femoral nerve stimulation (ΔQ(tw,pot)). CMD was estimated via quadriceps electromyogram. To rule out a direct central effect of fentanyl, we documented unchanged resting cardioventilatory responses. Compared to placebo, significant hypoventilation during the fentanyl trial was indicated by the 9% lower V(E)/V(CO(2)), causing a 5 mmHg increase in end-tidal P(CO(2)) and a 3% lower haemoglobin saturation. Arterial pressure and heart rate averaged 8 and 10% lower, respectively, during the fentanyl trial and these differences progressively diminished towards end-exercise. Although initially similar, the percent change in CMD was 9 ± 3% higher at end-exercise with fentanyl vs. placebo (P < 0.05). Time to exhaustion was shorter (6.8 ± 0.3 min vs. 8.7 ± 0.3 min) and end-exercise ΔQ(tw,pot) was about one-third greater (-44 ± 2% vs. -34 ± 2%) following fentanyl vs. placebo. The rate of peripheral fatigue development was 67 ± 10% greater during the fentanyl trial (P < 0.01). Our findings suggest that feedback from group III/IV muscle afferents limits CMD but also minimizes locomotor muscle fatigue development by stimulating adequate ventilatory and circulatory responses to exercise. In the face of blocked group III/IV muscle afferents, CMD is less inhibited but O(2) transport compromised and locomotor muscle fatigability is exacerbated with a combined net effect of a reduced endurance performance. |
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Authors:
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Markus Amann; Gregory M Blain; Lester T Proctor; Joshua J Sebranek; David F Pegelow; Jerome A Dempsey |
Publication Detail:
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Type: Clinical Trial; Journal Article; Research Support, N.I.H., Extramural Date: 2011-08-30 |
Journal Detail:
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Title: The Journal of physiology Volume: 589 ISSN: 1469-7793 ISO Abbreviation: J. Physiol. (Lond.) Publication Date: 2011 Nov |
Date Detail:
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Created Date: 2011-11-01 Completed Date: 2012-05-29 Revised Date: 2013-02-19 |
Medline Journal Info:
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Nlm Unique ID: 0266262 Medline TA: J Physiol Country: England |
Other Details:
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Languages: eng Pagination: 5299-309 Citation Subset: IM |
Affiliation:
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University of Utah, Department of Internal Medicine, Salt Lake City, UT, USA. markus.amann@hsc.utah.edu |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adult Analgesics, Opioid / pharmacology Electromyography Exercise / physiology* Fentanyl / pharmacology Heart Rate / drug effects Humans Magnetic Field Therapy Male Muscle Fatigue / physiology* Muscle Fibers, Skeletal / physiology* Physical Endurance Pulmonary Ventilation / drug effects Quadriceps Muscle / physiology* Young Adult |
| Grant Support | |
ID/Acronym/Agency:
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HL-103786-02/HL/NHLBI NIH HHS; HL-15469/HL/NHLBI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Analgesics, Opioid; 437-38-7/Fentanyl |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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