High-Intensity Interval Training Does Not Promote Fibrinolytic Adaptations in Healthy Men

Abstract

Blood clots cause the majority of adverse cardiovascular events, such as heart attack and stroke, and fibrinolysis, the capacity to dissolve blood clots, is recognized as an independent predictor of cardiovascular morbidity and mortality. Aerobic exercise training is theorized to enhance fibrinolytic potential, but studies have yielded inconclusive results. High intensity interval training (HIIT) is a novel exercise training strategy that has been shown to improve several components of health in various populations, but the effect of a HIIT regimen on fibrinolytic potential is unknown. PURPOSE: The purpose of this study was to examine potential fibrinolytic adaptations in healthy men following four and eight weeks of HIIT. METHODS: Healthy, sedentary men participated in a HIIT program three days/week for eight weeks. Training bouts were modeled after the traditional Wingate test, consisting of repeated, 30-second bouts of maximal intensity cycling separated by 4.5 minute rest intervals. Training began with three bouts per day and an additional bout/day was added to the regimen every two weeks, progressing up to six bouts per day in the final two weeks. Plasma concentrations of total tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) were assessed at baseline, after four weeks (4w), and after eight weeks (8w). Statistical comparisons across the three time points were done using repeated measures ANOVA. Significance was set to p<0.05. RESULTS: 21 men (age: 25± 5 yrs, BMI: 26.7± 6.2 kg/m2) completed the study. No significant changes were observed for tPA during training (baseline: 9.8 ± 3.1, 4w: 9.7 ± 2.9, 8w: 8.9 ± 2.7 ng/ml, p>0.05). Likewise, PAI-1 did not change with training (baseline: 17.7 ± 16.8, 4w: 18.8 ± 16.1, 8w: 18.0 ± 16.8 ng/ml, p>0.05). CONCLUSION: Though it has been suggested that HIIT may be superior to traditional, aerobic training for the purpose of enhancing one’s cardiovascular health, results of the present study do not indicate HIIT influences fibrinolytic potential in healthy young men. Future research should explore the benefits of HIIT in populations that may be characterized by diminished fibrinolytic potential.