In The Public Domain Effect of Aging on Changes in Plasma Potassium During Exercise

Background. Exercising skeletal muscle releases large amounts of potassium into plasma. (3-adrenergic receptors enhance reuptake of potassium into muscle. Since p-adrenergic responses decline with aging in many tissues, the elderly might be predisposed to hyperkalemia during exercise. Methods. Venous plasma potassium (K +) was measured during graded bicycle exercise (30 W initial workload with 3-minute 30 W increments) in 18 healthy young men (24.0 ± 2.9 yrs; mean ± SD), 18 healthy untrained elderly men (70.0 ± 3. 6 yrs), and 7 elderly master athletes (70.0 ± 4. 6 yrs). Subjects exercised to exhaustion. Results. Exercise times and maximal oxygen uptake were: young (TV = 14; 19.6 ± 4.4 min, 42.1 ± 3.8 ml/kg/min), elderly (N = 13; 11.7 ± 1.9 min, 26.6 ± 8.0 ml/kg/min), elderly master athletes (N = 6; 16.8 ± 2.4 min, 40.2 ± 10.2 ml/kg/min). The rate of increase in K+ was greater in both elderly (89 ± 59 fimol/l/min) and elderly master athletes (88 ± 26) compared with healthy young men (60 ± 30), p <.05. Despite this greater rate of increase, the elderly group did not achieve higher maximal K+ concentrations than the young because of the much shorter duration of exercise in the elderly group. For subjects performing a maximal exercise test, the maximal increase in K+ was similar in the elderly (1.15 ± 0.91), but significantly greater in elderly master athletes (1.70 ± 0.31), compared with healthy young men (1.3) ± 0.45). Conclusions. Changes in K+ during short-lasting exercise are similar in untrained healthy elderly men compared wit