Regular Resistance Training Enhances Fibrinolytic Potential

Abstract

Blood clots cause most cardiovascular events, such as heart attack and stroke. Blood markers of fibrinolysis, the capacity to dissolve blood clots, are independently associated with cardiovascular morbidity and mortality. Regular resistance training (RT) produces various muscular and vascular adaptations that are theorized to influence thrombotic potential, but there are no published longitudinal studies that examine fibrinolytic adaptations to RT. PURPOSE: The purpose of this study was to identify effects of an 8-week RT program on fibrinolytic potential. METHODS: Sixteen healthy adults (n = 12 women, 4 men; age = 23 ± 5 years) completed a RT program that targeted all major muscle groups, 3 times per week for 8 weeks. Exercises included 2-3 sets of 8-12 repetitions performed at approximately 60-80% of 1 RM. Body composition, circumferences, and 1 RM leg and chest press strength measures were obtained via standard methods. Resting blood samples were obtained by clean venipuncture at baseline and after 8 weeks of RT. Enzyme-linked immunosorbancy assays were used to assess plasma concentrations of the following fibrinolytic variables: active tissue plasminogen activator (tPA:c), tissue plasminogen activator antigen (tPA:g), active plasminogen activator inhibitor-1 (PAI-1:c), and plasminogen activator inhibitor-1 antigen (PAI-1:g). Statistical analyses were conducted using paired t-tests. RESULTS: Significant increases in lean mass (PRE = 52.18 ± 10.03, POST = 53.64 ± 10.42 kg), arm circumference (PRE = 29.89 ± 5.12, POST = 30.97 ± 4.92 cm), and mid-thigh circumference (PRE = 49.96 ± 5.43, POST = 51.08 ± 5.83 cm) were observed (all p<0.05). Maximal chest press (PRE = 57.8 ± 37.5, POST = 73.3 ± 43.2 kg) and leg press strength (PRE = 189.5 ± 95.8, POST = 256.7 ± 97.9 kg) significantly increased (p<0.01). PAI-1:c (PRE = 20.3 ± 32.5, POST = 9.5 ± 20.9 U/ml, p=0.05) and PAI-1:g decreased (PRE = 10.18 ± 8.98, POST = 7.20 ± 5.74 ng/dl, p<0.05 ). No change in tPA:c or tPA:g occurred. CONCLUSION: The decrease in plasma concentrations of total and active PAI-1 indicate reduced inhibition of fibrinolytic activation, suggesting that the risk of a cardiovascular event is reduced after resistance training. The mechanisms underlying this specific adaptation may relate to increased skeletal muscle mass, but additional research is warranted.