{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,14]],"date-time":"2026-10-14T11:03:15Z","timestamp":1791975795650,"version":"4.4.0"},"reference-count":38,"publisher":"American Physiological Society","issue":"1","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2008,7]]},"abstract":"<jats:p> A decrease in maximal exercise heart rate (HR<jats:sub>max<\/jats:sub>) is a key contributor to reductions in aerobic exercise capacity with aging. However, the mechanisms involved are incompletely understood. We sought to gain insight into the respective roles of intrinsic heart rate (HR<jats:sub>int<\/jats:sub>) and chronotropic \u03b2-adrenergic responsiveness in the reductions in HR<jats:sub>max<\/jats:sub> with aging in healthy adults. HR<jats:sub>max<\/jats:sub> (Balke treadmill protocol to exhaustion), HR<jats:sub>int<\/jats:sub> (HR during acute ganglionic blockade with intravenous trimethaphan), and chronotropic \u03b2-adrenergic responsiveness (increase in HR with incremental intravenous infusion of isoproterenol during ganglionic blockade) were determined in 15 older (65 \u00b1 5 yr) and 15 young (25 \u00b1 4 yr) healthy men. In the older men, HR<jats:sub>max<\/jats:sub> was lower (162 \u00b1 9 vs. 191 \u00b1 11 beats\/min, P &lt; 0.0001) and was associated with a lower HR<jats:sub>int<\/jats:sub> (58 \u00b1 7 vs. 83 \u00b1 9 beats\/min, P &lt; 0.0001) and chronotropic \u03b2-adrenergic responsiveness (0.094 \u00b1 0.036 vs. 0.154 \u00b1 0.045 \u0394HR\/[isoproterenol]: P &lt; 0.0001). Both HR<jats:sub>int<\/jats:sub> ( r = 0.87, P &lt; 0.0001) and chronotropic \u03b2-adrenergic responsiveness ( r = 0.61, P &lt; 0.0001) were positively related to HR<jats:sub>max<\/jats:sub>. Accounting for the effects of HR<jats:sub>int<\/jats:sub> and chronotropic \u03b2-adrenergic responsiveness reduced the age-related difference in HR<jats:sub>max<\/jats:sub> by 83%, rendering it statistically nonsignificant ( P = 0.2). Maximal oxygen consumption was lower in the older men (34.9 \u00b1 8.1 vs. 48.6 \u00b1 6.7 ml\u00b7kg<jats:sup>\u22121<\/jats:sup>\u00b7min<jats:sup>\u22121<\/jats:sup>, P &lt; 0.0001) and was positively related to HR<jats:sub>max<\/jats:sub> ( r = 0.62, P &lt; 0.0001), HR<jats:sub>int<\/jats:sub> ( r = 0.51, P = 0.002), and chronotropic \u03b2-adrenergic responsiveness ( r = 0.47, P = 0.005). Our findings indicate that, together, reductions in HR<jats:sub>int<\/jats:sub> and chronotropic responsiveness to \u03b2-adrenergic stimulation largely explain decreases in HR<jats:sub>max<\/jats:sub> with aging, with the reduction in HR<jats:sub>int<\/jats:sub> playing by far the greatest role. <\/jats:p>","DOI":"10.1152\/japplphysiol.90401.2008","type":"journal-article","created":{"date-parts":[[2008,5,15]],"date-time":"2008-05-15T20:59:20Z","timestamp":1210885160000},"page":"24-29","source":"Crossref","is-referenced-by-count":142,"title":["Decreased maximal heart rate with aging is related to reduced \u03b2-adrenergic responsiveness but is largely explained by a reduction in intrinsic heart rate"],"prefix":"10.1152","volume":"105","author":[{"given":"Demetra D.","family":"Christou","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Douglas R.","family":"Seals","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"24","reference":[{"key":"R1","doi-asserted-by":"publisher","DOI":"10.1093\/geronj\/36.3.298"},{"key":"R2","doi-asserted-by":"publisher","DOI":"10.1093\/oxfordjournals.eurheartj.a060792"},{"key":"R3","doi-asserted-by":"publisher","DOI":"10.1001\/jama.1989.03430170057028"},{"key":"R4","doi-asserted-by":"publisher","DOI":"10.1007\/BF00583263"},{"key":"R5","doi-asserted-by":"publisher","DOI":"10.1016\/0014-2999(79)90314-5"},{"key":"R6","doi-asserted-by":"publisher","DOI":"10.1093\/cvr\/5.4.577"},{"key":"R7","doi-asserted-by":"publisher","DOI":"10.1152\/ajpheart.1995.268.4.H1441"},{"key":"R8","doi-asserted-by":"publisher","DOI":"10.1093\/oxfordjournals.eurheartj.a062120"},{"key":"R9","doi-asserted-by":"publisher","DOI":"10.1038\/clpt.1980.108"},{"key":"R10","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1995.78.5.1931"},{"key":"R11","doi-asserted-by":"publisher","DOI":"10.1159\/000212726"},{"key":"R12","doi-asserted-by":"publisher","DOI":"10.1161\/01.CIR.90.5.2333"},{"key":"R13","doi-asserted-by":"publisher","DOI":"10.1042\/cs0870297"},{"key":"R14","doi-asserted-by":"publisher","DOI":"10.1161\/01.CIR.96.1.345"},{"key":"R16","unstructured":"Haqqani HM, Kalman JM. 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