Left ventricular dysfunction after prolonged strenuous exercise in healthy subjects

To determine whether depressed left ventricular (LV) contractile function can occur after prolonged and strenuous exercise, 12 healthy men, 26 ± 1 years old (mean ± standard error of the mean) were studied. The subjects exercised on a treadmill at 69 ± 1 % of maximal O₂ uptake until exhaustion (170 ± 10 minutes). Hemodynamic variables were measured before and 10 minutes aftere exhausting exercise. Baseline systolic blood pressure decreased from 124 ± 2 to 113 ± 3 mm Hg (p < 0.001) after exhausting exercise. LV end-diastolic diameter, measured by echocardiography, decreased from 51 ± 1.0 to 47 ± 1.0 mm (p < 0.005) but LV end-systolic diameter did not change (34 ± 1.0 vs 34 ± 1.0 mm). Both LV fractional shortening and the mean velocity of circumferential fiber shortening decreased (33 ± 1 vs 28 ± 1%; p <0.01 and 1.09 ± 0.4 vs 0.97 ± 0.05 circ/s; p < 0.025) despite a lower end-systolic wall stress (σ_es = 88 ± 4 vs 82 ± 5, × 10³ dynes/ cm²; p <0.05) after prolonged exhausting exercise. A repeat bout of exercise of the same intensity but brief in duration (10 minutes) resulted in increases in LV fractional shortening (p <0.001) and mean velocity of circumferential fiber shortening (p < 0.001), and a decrease in LV end-diastolic diameter (50 ± 1.0 to 48 ± 1.0 mm; p <0.05) at heart rates comparable to those attained after prolonged exhausting exercise. The results suggest that prolonged strenuous exercise may result in impaired LV function in healthy young subjects.