Although plasma norepinephrine (NE) increases with age in response to a variety of submaximal adrenergic stimuli, the effect of age on plasma catecholamine levels during maximal aerobic effort and during submaximal work at a fixed percent of peak O2 consumption (V̇(O2) is unknown. We therefore measured NE, epinephrine (E), and V̇(O2) at rest and during graded maximal treadmill exercise in 24 healthy male volunteers (ages 22-77 yr) from the Baltimore Longitudinal Study of Aging who were rigorously screened to exclude the presence of cardiovascular disease. At rest neither heart rate (HR) nor V̇(O2) were age related. Resting NE (pg/ml) was not age related, but resting E (pg/ml) was higher in male subjects 68-77 yr old (group III) than in those aged 22-37 (group I) or 44-55 yr (group II), P < 0.01. Maximal HR (beats/min) showed a strong inverse relationship to age (203.5-0.65 age, r = -0.80, P < 0.001). Peak V̇O2 in milliliters per kilogram total body weight per minute decreased with age (47.7 - 0.23 age, r = -0.71, P < 0.001). At maximal effort both NE (P < 0.01) and E (P < 0.05) were higher in group III than in either of the younger groups. At submaximal work levels NE and E also increased with age, and when normalized for relative effort at loads between 45 and 80% of peak V̇(O2) both NE and E were higher in the group III male subjects, although statistical significance was reached for NE (P < 0.01) but not for E (P = 0.09). Thus, for any relative level of aerobic stress incurred by healthy males during treadmill exercise, plasma catecholamines are higher in the elderly.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of applied physiology|
|State||Published - Dec 1 1985|
ASJC Scopus subject areas
- Physiology (medical)