Introduction
Immediately after physical exercise, the risk of cardiovascular events increases; however, in the long term, aerobic exercise improves cardiovascular health. In cardiovascular rehabilitation, moderate-intensity continuous training (MICT) is most commonly used, though high-intensity interval training (HIIT) has been gaining ground in recent times. Compared to MICT, HIIT is thought to improve capacity more quickly, likely at the price of a slightly higher risk of complications. Haemostasis is one of the indicators of the balance between the efficacy and safety of physical exercise in cardiac patients, but there are no studies comparing the effects of HIIT and MICT on haemostasis. The aim of this study was to evaluate the acute and chronic effect of different types of physical exercise (HIIT and MICT) on haemostasis appraised by the overall haemostatic potential (OHP), overall fibrinolytic potential (OFP), and overall coagulation potential (OCP) in patients with coronary artery disease.
Methods
In this randomised interventional study, we included patients after a recent myocardial infarction, that were referred to a rehabilitation programme. Patients were randomly allocated into two groups: the first group performed HIIT-based exercise for three months, three hours per week; those in the second group performed MICT-based exercise for three months, three hours per week. Six peripheral venous blood samples were collected from each patient: at baseline (before the first exercise session, after the first exercise session, and after one hour of rest) and at the end of the intervention period (before the last exercise session, after the last exercise session, and after one hour of rest). OHP, OCP, and OFP were determined using spectrophotometric analysis, fibrinogen, D-dimer, and von Willebrand factor antigen (vWF:ag) were assessed according to validated protocols.
Results
A total of 117 subjects were included in the study, 59 in the HIIT group and 58 in the MICT group. There were no significant differences between the groups in baseline characteristics. Both groups showed an increase in peak oxygen uptake (VO2peak) after the rehabilitation programme (from 23.2 ± 6.1 to 25.2 ± 4.7 in the HIIT group and from 21.6 ± 5.7 to 24.4 ± 4.3 in the MICT group), with no difference between the groups. Baseline values of OHP, OCP, OFP, and vWF:ag were comparable between the groups. In the linear mixed model analysing the acute effects in untrained individuals, time (i.e., the effect of exercise) had a statistically significant impact on all coagulation variables – OHP (F (2, 98.190) = 7,214, p = 0,001); OKP (F (2, 99.391) = 6,906, p = 0,002); OFP (F (2, 99.291) = 3,239, p = 0,043); fibrinogen (F (2, 114.355) = 43,683, p < 0,001); D-dimer (F (2, 110.594) = 4,855, p = 0,010); vWF:ag (F (2;110.407) = 19,279, p < 0,001). The time*group interaction (i.e., the intervention effect) was statistically significant only for D-dimer (F (2, 110.594) = 3.777, p = 0.026). In the linear mixed model analysing the long-term effects of exercise, a significant increase in OFP (F (1, 94.665) = 5.161, p = 0.0025) and a decrease in fibrinogen concentration (F (1, 110.318) = 4.635, p = 0.034) were observed after intervention. There were no differences in the time*group interaction for long-term effects. In the linear mixed model analysing the acute effects of exercise in trained individuals, time had a significant effect on OHP (F (1, 90.753) = 7.214, p = 0.009) and OFP (F (1, 87.345) = 5.967, p = 0.017). A difference between HIIT and MICT was observed for fibrinogen (F (1, 111.211) = 4.228, p = 0.042). For vWF:ag, a significant time*group interaction was detected (F (1,108.191) = 3.998, p = 0.048).
Conclusion
Our study shows that a single session of physical exercise in untrained patients with coronary artery disease triggers an acute, but short-lived, increase in haemostasis due to increased coagulation and decreased fibrinolysis, which normalises during the resting period. In the long term, physical exercise increases fibrinolysis without affecting coagulation. In trained subjects, a session of physical exercise results in a similar acute increase in haemostasis, increased coagulation, and decreased fibrinolysis compared to untrained subjects; however, in trained subjects, haemostasis values decrease more during the rest period and fibrinolysis values increase more. High-intensity interval training and moderate-intensity continuous training have a comparable effect on haemostasis.
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