{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T15:51:38Z","timestamp":1791215498034,"version":"4.1.0"},"reference-count":24,"publisher":"American Physiological Society","issue":"6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2002,12,1]]},"abstract":"<jats:p> We assessed the effects of naloxone, an opioid antagonist, on exercise capacity in 13 men and 5 women (mean age = 30.1 yr, range = 21\u201335 yr) during a 25 W\/min incremental cycle ergometer test to exhaustion on different days during familiarization trial and then after 30 mg (iv bolus) of naloxone or placebo (Pl) in a double-blind, crossover design. Minute ventilation (V\u02d9e), O<jats:sub>2<\/jats:sub> consumption (V\u02d9o <jats:sub>2<\/jats:sub>), CO<jats:sub>2<\/jats:sub> production, and heart rate (HR) were monitored. Perceived exertion rating (0-10 scale) and venous samples for lactate were obtained each minute. Lactate and ventilatory thresholds were derived from lactate and gas-exchange data. Blood pressure was obtained before exercise, 5 min postinfusion, at maximum exercise, and 5 min postexercise. There were no control-Pl differences. The naloxone trial demonstrated decreased exercise time (96% Pl; P &lt; 0.01), total cumulative work (96% Pl; P &lt; 0.002), peakV\u02d9o <jats:sub>2<\/jats:sub> (94% Pl; P &lt; 0.02), and HR (96% Pl; P &lt; 0.01). Other variables were unchanged. HR and V\u02d9e were the same at the final common workload, but perceived exertion was higher (8.1 \u00b1 0.5 vs. 7.1 \u00b1 0.5) after naloxone than Pl ( P &lt; 0.01). The threshold for effort perception amplification occurred at \u223c60 \u00b1 4% of Pl peakV\u02d9o <jats:sub>2<\/jats:sub>. Thus we conclude that peak work capacity was limited by perceived exertion, which can be attenuated by endogenous opioids rather than by physiological limits. <\/jats:p>","DOI":"10.1152\/japplphysiol.00521.2002","type":"journal-article","created":{"date-parts":[[2015,3,3]],"date-time":"2015-03-03T15:42:53Z","timestamp":1425397373000},"page":"2023-2028","source":"Crossref","is-referenced-by-count":63,"title":["Effect of naloxone on perceived exertion and exercise  capacity during maximal cycle ergometry"],"prefix":"10.1152","volume":"93","author":[{"given":"Anthony L.","family":"Sgherza","sequence":"first","affiliation":[{"name":"Department of Physical Education and Exercise Science, Brooklyn College, Brooklyn 11210;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kenneth","family":"Axen","sequence":"additional","affiliation":[{"name":"Department of Physical Education and Exercise Science, Brooklyn College, Brooklyn 11210;"},{"name":"Joan and Joel Smilow Cardiac 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