Changes in fibrinolysis following exercise above and below lactate threshold.

This study sought to compare fibrinolytic responses to exercise above lactate threshold (LT) to longer-duration, equicaloric exercise below LT. Fifteen males performed cycle ergometer tests above (77% VO(2)peak) and below LT (41% VO(2)peak) to comparatively evaluate tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) responses. tPA activity significantly (P < 0.05) increased during the >LT test (pre-exercise = 1.57 +/- 0.44 IU ml(-1), post-exercise = 3.85 +/- 4.72 IU ml(-1)), but not the <LT test (pre-exercise = 1.51 +/- 0.36 IU ml(-1), post-exercise = 1.94 +/- 1.00 IU ml(-1)). Plasma tPA antigen significantly (P < 0.05) increased during both the >LT (pre-exercise = 8.32 +/- 4.48 ng ml(-1), post-exercise = 14.23 +/- 5.40 ng ml(-1)) and <LT (pre-exercise = 7.40 +/- 3.52 ng ml(-1), post-exercise = 9.03 +/- 3.25 ng ml(-1)) tests. Furthermore, post-exercise tPA antigen was greater (P < 0.05) following the >LT test. PAI-1 activity significantly (P < 0.05) decreased during both the >LT (pre-exercise = 15.00 +/- 2.73 AU ml(-1), post-exercise = 10.12 +/- 2.90 AU ml(-1)) and <LT (pre-exercise = 14.51 +/- 2.80 AU ml(-1), post-exercise=12.59 +/- 2.20 AU ml(-1)) tests, and the post-exercise PAI-1 activity was significantly (P < 0.05) lower during the >LT test. Our results suggest that exercise <LT can cause fibrinolytic responses and that exercise above LT elicits greater fibrinolytic responses than equicaloric exercise performed below LT.