Effects of physical conditioning on fibrinolytic variables and fibrinogen in young and old healthy adults

Background. The effects of 6 months of intensive endurance exercise training on resting tissue-type plasminogen activator (t-PA) activity, plasminogen activator inhibitor type 1 (PAI-1) activity, t-PA antigen, and fibrinogen were studied in 10 young (24-30 years) and in 13 old male subjects (60-82 years). Methods and Results. After training, maximum oxygen consumption was increased in the young group by 18% (44.9±5.0 to 52.9±6.6 ml/kg/min, p<0.001), whereas it was increased in the old group by 22% (29.0±4.2 to 35.5±3.6 ml/kg/min, p<0.001). The young group had no significant changes in any of the measured variables, whereas the old group had a 39% increase in t-PA activity (0.82±0.47 to 1.14±0.42 IU/ml, p<0.03), a 141% increase in the percentage of t-PA in the active form (11.1±7.7 to 26.8±15.1%, p<0.01), a 58% decrease in PAI-1 activity (8.4±4.9 to 3.5±1.7 AU/ml, p<0.01), and a 13% decrease in fibrinogen (3.57±0.79 to 3.11±0.52 g/l, p<0.01). Conclusions. We conclude that intensive exercise training enhances resting t-PA activity and reduces fibrinogen and PAI-1 activity in older men. These effects are potential mechanisms by which habitual physical activity might reduce the risk of cardiovascular disease.