WOMACK, C. J., C. M. PATON, A. M. COUGHLIN, P. R. NAGELKIRK, A. T. DEJONG, J. ANDERSON, and B. A. FRANKLIN. Coagulation and Fibrinolytic Responses to Manual versus Automated Snow Removal. Med. Sci. Sports Exerc., Vol. 35, No. 10, pp. 1755–1759, 2003.
Purpose: The purpose of this study was to assess coagulation and fibrinolytic responses to snow removal.
Methods: Thirteen healthy male subjects (age = 26 ± 5 yr, height = 179.0 ± 7.0 cm, weight = 78.7 ± 16.1 kg, V̇O2max = 54.7 ± 8.9 mL·kg−1·min−1) underwent maximal treadmill stress testing (TM), 10 min of snow shoveling (SS), and 10 min of snow removal using an automated snow thrower (ST). Blood was collected immediately before and after each test and analyzed for von Willebrand Factor antigen (vWF:ag), tissue plasminogen activator (tPA) antigen, and plasminogen activator inhibitor-1 (PAI-1) activity. Data were analyzed using a two-factor repeated-measures analysis of variance.
Results: vWF:ag significantly increased during TM (84.7 ± 21.7% normal preexercise, 149.0 ± 45.6% normal postexercise) but not SS or ST. TM resulted in significant increases in tPA antigen (6.54 ± 2.76 ng·mL−1 preexercise, 21.39 ± 10.56 ng·mL−1 postexercise) and both SS and TM caused significant reductions in PAI-1 activity (SS = 15.1 ± 3.8 AU·mL−1 preexercise, 13.2 ± 4.3 AU·mL−1 postexercise; TM = 15.3 ± 3.6 AU·mL−1 preexercise, 10.5 ± 5.3 AU·mL−1 postexercise). Postexercise PAI-1 activity was significantly lower for TM versus SS. tPA antigen was unchanged after SS and ST, and PAI-1 activity was unchanged after ST.
Conclusion: vWF:ag is unchanged after self-paced snow shoveling and automated snow removal in young, healthy males. Snow shoveling acutely increases fibrinolytic potential in this population, although not to the degree observed after maximal treadmill exercise.
Typically, hemorrhage or ulceration of atherosclerotic plaque initiates an acute cardiovascular event. Thrombus formation inside the ulcerated plaque or in the atherosclerotic vessel ultimately occludes the lumen. However, plaque ruptures have been observed in autopsy studies of individuals without a history of cardiovascular events (5,19), suggesting occlusive thrombus formation does not always occur with plaque rupture. Therefore, blood coagulation potential and/or the potential to lyse clot (fibrinolysis) are likely important determinants in this cascade of acute cardiovascular events (and their sequelae). Accordingly, increased coagulation potential and decreased fibrinolysis are associated with acute cardiovascular events (4,12). Furthermore, potential for coagulation is increased (20,23,26) and fibrinolysis decreased (10,13,16,21) in patients with cardiovascular disease (CVD).
Vigorous exercise transiently increases the risk of acute cardiovascular events, especially in habitually sedentary persons with documented or occult CVD (22,25). Coronary artery disease (CAD) is the leading cause of death during exercise in adults (22), and physical activity has been noted as a trigger of infarction in up to one third of patients able to identify a possible trigger (25). The transient increase in cardiovascular events during exercise is likely due, at least in part, to an altered coagulation and/or fibrinolytic exercise response, as myocardial infarctions triggered by physical stress are more likely to occur due to an occlusive thrombus (9). Furthermore, acute exercise results in a larger increase in coagulation potential in patients with CVD (20).
The rate of death from cardiovascular events is higher in the winter months (1,3), which may be partially due to snow shoveling (11). The hemodynamic responses to heavy snow shoveling are similar to those seen during maximal treadmill testing (8), suggesting disproportionate and potentially threatening myocardial demands. The high degree of muscular effort during snow shoveling may predispose at-risk individuals to exertion-related myocardial infarction as the majority of these events occur during or immediately after physical tasks that require significant lifting or isometric contraction (9). It is not known whether this increased risk is related to altered coagulation and/or fibrinolytic responses, although El-Sayed (6) reported robust increases in both factor VIII, a marker of coagulation potential, and fibrinolysis after acute strength training. If snow shoveling causes similar hemostatic responses, this could explain the high rate of cardiovascular events that are triggered by this activity.
Although the hemostatic response to automated snow removal has not been evaluated, use of an automated snow thrower has been shown to result in an attenuated hemodynamic and metabolic response as compared with snow shoveling (8,24). The purpose of the proposed study was to determine changes in thrombotic and fibrinolytic potentials during snow shoveling versus maximal treadmill exercise and automated snow removal. We hypothesize that snow shoveling elicits coagulation and fibrinolytic responses similar to those observed after maximal treadmill exercise and that automated snow removal decreases these hemostatic responses.