MAXIMAL SHORT-TERM EXERCISE PERFORMANCE AND ION REGULATION IN CYSTIC-FIBROSIS

Controversy exists over whether defects in electrolyte transport exist in erythrocytes from cystic fibrosis (CF) patients. We hypothesized t hat differences in ion regulation in CF would affect skeletal muscle p erformance during intense exercise. Seven well-nourished CF patients w ere compared with seven healthy age-matched control subjects. Skeletal muscle performance was assessed during a 30-s sprint on an isokinetic cycle ergometer. Ion regulation was evaluated from arterialized venou s blood sampled at rest, at peak exercise, and after 5 min of recovery . There was no difference in sprint performance between the CF (total work, 93.7 +/- 30.02 % predicted; endurance, 30.6 +/- 9.93 % decline) and control (109.7 +/- 19.48 %; 35.6 +/- 14.76 %) groups. The changes in plasma and erythrocyte ions and blood gases did not differ between the groups. There was a suggestion that the CF group may have had an i nadequate ventilatory response to the metabolic challenge of short-ter m maximal exercise. The contribution of decreases in the strong ion di fference to increases in plasma hydrogen ion concentrations was less i n the CF group. This may be due to alterations in ionic regulation in CF, but the influence of inadequate arterialization of the blood sampl es could not be ruled out.