The effect of different exercise intensities on the fibrinolytic system

Hemostatic Responses to Multiple Bouts of Firefighting Activity: Female vs. Male Differences in a High Demand, High Performance Occupation

While the fire service has long been a male-dominated occupation, women's participation in this strenuous, high risk, high performance activity has increased in recent years. Firefighting induces significant cardiovascular strain, including hemostatic disruption; however, the effect of sex on hemostatic responses has not been investigated despite evidence that there are sex-related differences in hemostatic variables at rest and following exercise. Thus, we investigated hemostatic responses in age- and BMI-matched male and female firefighters who performed 3-4 evolutions of firefighting drills over a 3 h period. Venous blood samples were collected before and after the firefighting training drills and hemostatic variables were assessed. Firefighting significantly increased platelet count and factor VIII, tissue plasminogen activator (t-PA) antigen, and t-PA activity, and decreased activated partial thromboplastin time and plasminogen activator inhibitor (PAI-1) activity. Females had lower values for epinephrine-induced platelet closure time, antithrombin III, PAI-1 activity, and PAI-1 antigen. There were no interactions between sex and time for any variables assessed. In conclusion, multiple bouts of firefighting activity resulted in a procoagulatory state. Although there were sex differences for several hemostatic variables, male and female firefighters did not differ in their hemostatic response to multiple bouts of firefighting.

Effects of Four-Week Rehabilitation Program on Hemostasis Disorders in Patients with Spinal Cord Injury

Background: Patients with spinal cord injury (SCI) exhibit hemostasis disorders. This study aims at assessing the effects of a 4-week rehabilitation program on hemostasis disorders in patients with SCI. Methods: Seventy-eight in-patients undergoing a 4-week rehabilitation were divided into three groups based on time elapsed since SCI: I (3 weeks–3 months), II (3–6 months), and III (>6 months). Tissue factor (TF), tissue factor pathway inhibitor (TFPI), thrombin–antithrombin complex (TAT) and D-dimer levels, antithrombin activity (AT), and platelet count (PLT) were measured on admission and after rehabilitation. Results: Rehabilitation resulted in an increase in TF in group III (p < 0.050), and decrease in TFPI (p < 0.022) and PLT (p < 0.042) in group II as well as AT in group I (p < 0.009). Compared to control group without SCI, TF, TFPI, and TAT were significantly higher in all SCI groups both before and after rehabilitation. All SCI groups had elevated D-dimer, which decreased after rehabilitation in the whole study group (p < 0.001) and group I (p < 0.001). Conclusion: No decrease in activation of TF-dependent coagulation was observed after a 4-week rehabilitation regardless of time elapsed since SCI. However, D-dimer levels decreased significantly, which may indicate reduction of high fibrinolytic potential, especially when rehabilitation was done <3 months after SCI.

Compression socks and the effects on coagulation and fibrinolytic activation during marathon running

PURPOSE

Compression socks are frequently used in the treatment and prevention of lower-limb pathologies; however, when combined with endurance-based exercise, the impact of compression socks on haemostatic activation remains unclear.

OBJECTIVES

To investigate the effect of wearing compression socks on coagulation and fibrinolysis following a marathon.

METHODS

Sixty-seven participants [43 males (mean ± SD: age: 46.7 ± 10.3 year) and 24 females (age: 40.0 ± 11.0 year)] were allocated into a compression (SOCK, n = 34) or control (CONTROL, n = 33) group. Venous blood samples were obtained 24 h prior to and immediately POST-marathon, and were analyzed for thrombin-anti-thrombin complex (TAT), tissue factor (TF), tissue factor pathway inhibitor (TFPI), and D-Dimer.

RESULTS

Compression significantly attenuated the post-exercise increase in D-Dimer compared to the control group [median (range) SOCK: + 9.02 (- 0.34 to 60.7) ng/mL, CONTROL: + 25.48 (0.95-73.24) ng/mL]. TF increased following the marathon run [median (range), SOCK: + 1.19 (- 7.47 to 9.11) pg/mL, CONTROL: + 3.47 (- 5.01 to 38.56) pg/mL] in all runners. No significant post-exercise changes were observed for TAT and TFPI.

CONCLUSIONS

While activation of coagulation and fibrinolysis was apparent in all runners POST-marathon, wearing compression socks was shown to reduce fibrinolytic activity, as demonstrated by lower D-Dimer concentrations. Compression may reduce exercise-associated haemostatic activation when completing prolonged exercise.

Time of day and short-duration high-intensity exercise influences on coagulation and fibrinolysis

Exercise has been demonstrated to have considerable effects upon haemostasis, with activation dependent upon the duration and intensity of the exercise bout. In addition, markers of coagulation and fibrinolysis have been shown to possess circadian rhythms, peaking within the morning (0600-1200 h). Therefore, the time of day in which exercise is performed may influence the activation of the coagulation and fibrinolytic systems. This study aimed to examine coagulation and fibrinolytic responses to short-duration high-intensity exercise when completed at different times of the day. Fifteen male cyclists (VO_2max: 60.3 ± 8.1 ml kg^-1 min^-1) completed a 4-km cycling time trial (TT) on five separate occasions at 0830, 1130, 1430, 1730 and 2030. Venous blood samples were obtained pre- and immediately post-exercise, and analysed for tissue factor (TF), tissue factor pathway inhibitor (TFPI), thrombin-anti-thrombin complexes (TAT) and D-Dimer. Exercise significantly increased plasma concentrations of TF (p < .0005), TFPI (p < .0006), TAT complexes (p < .0012) and D-Dimer (p < .0003). There was a time-of-day effect in pre-exercise TF (p = .004) and TFPI (p = .031), with 0830 greater than 1730 (p  .001), while 1730 was less than 2030 h (p = .008), respectively. There was no significant effect of time of day for TAT (p = .364) and D-Dimer (p = .228). Power output, TT time and heart rate were not significantly different between TTs (p > .05); however, percentage VO_2max was greater at 1730 when compared to 2030 (p = .04). Due to a time-of-day effect present within TF, peaking at 0830, caution should be applied when prescribing short-duration high-intensity exercise bout within the morning in populations predisposed to hypercoagulability.

Acute physical exercise is safe in patients with primary antiphospholipid syndrome with exclusive venous thrombosis and under oral anticoagulation with warfarin

The purpose of present study was to evaluate the effects of maximal acute physical exercise on prothrombin time/international normalized ratio (PT/INR) in patients with primary antiphospholipid syndrome (PAPS) under oral anticoagulation with warfarin and the safety of acute exercise in regard to thrombosis and bleeding risk. Eighteen physically inactive women with PAPS (Sydney criteria) with exclusive venous events and without thrombocytopenia were included. All patients were under stable warfarin therapy (PT/INR target: 2.0-3.0). Eighteen age-matched healthy sedentary women without thrombosis/bleeding disorders were selected as controls. All subjects performed a maximal exercise test, and capillary blood samples were obtained pre-, post- and at 1-h post-exercise (recovery time) for PT/INR analysis using a portable CoaguCheck. PAPS patients and controls had similar mean age (31.50 ± 8.06 vs. 29.61 ± 7.05 years, p = 0.46) and body mass index (24.16 ± 3.67 vs. 24.66 ± 2.71 kg/m(2), p = 0.65). PAPS had a mild but significant increase in PT/INR value at 1-h post-exercise (recovery) compared with pre- (2.33 ± 0.34 vs. 2.26 ± 0.29, p = 0.001) and post-exercise (2.33 ± 0.34 vs. 2.26 ± 0.32, p = 0.001) that was observed in 61.11 % of these patients. None of the subjects had thrombotic or bleeding complications related to the acute exercise. Acute exercise in patients with PAPS with exclusive venous thrombosis was safe with a minor increase in PT/INR. This is an important step to introduce regular exercise training as a therapeutic tool in the management of these patients.

The effect of the acute submaximal exercise on thrombin activatable fibrinolysis inhibitor levels in young sedentary males

Depending on type, duration, and intensity of the exercise, changes occur in hemostasis. In this study, we evaluated the changes in the parameters of coagulation and fibrinolytic systems that happened after the submaximal aerobic exercises by bicycle ergomater. Twelve healthy male participants whose ages were between 21 and 28 have been included. The venous samples have been drawn before the exercise as well as at the 0 th, 15th, and 60th minutes after the submaximal exercise. The values of prothrombin time (PT), active partial thromboplastin time (aPTT), D-dimer, fibrinogen, plasminogen activator inhibitor 1 (PAI-1) and thrombin-activatable fibrinolysis inhibitor (TAFI) have been measured. Plasminogen activator inhibitor 1 values have shown an insignificant increase after exercise (P = .328), whereas, it has decreased significantly during the resting period (P = .033) Postexercise 15th and 60th minutes TAFI values have decreased significantly comparing to basal and postexercise (0 th minute) values (P = .001). Fibrinolytic system activation is observed after acute submaximal aerobic exercise of sedentary healthy participants.

[Assessment of changes in body composition in critically ill patients]

Critically ill patients are especially prone to malnutrition because their hypermetabolic state produces an increase in nutritional requirements that often are not covered with the formulae supplied. Evaluation of the body composition (BC) makes it possible to quantify the main structural components of the body: muscle, bone and fat. An anthropometry study was made for the assessment of these elements to obtain information on the protein-calorie nutritional status of critically ill patients. We have aimed to describe the variations in the BC of the critical ill patient during the first seven days after ICU admission. The observational study included 50 critically ill patients, of whom 78% were male and 22% women with a mean age of 56 years. Height, weight, body mass index (BMI), bone diameters, muscle perimeters and skinfolds of patients were recorded. The body composition (BC) calculations were performed using the Faulkner, Rocha, Wurch and Matiegka formulae. We obtained the baseline energy expenditure of each patient with the Harris-Benedict formula. After analyzing the data, a decrease was found in the percentage of muscle mass (mean+/-SD: 3+/-0.76), an increase in the percentage of body fat (2+/-0.76) and an increase in BMI at the expense of an augment of weight. We have concluded that during the first week of ICU admission patients lose critical muscle mass and have an increase in fat mass. Awareness of these changes in the BC of patients may be useful to determine the appropriate nutrition for critically ill patients.

Exercise causing thrombosis

Thrombophilia refers to the increased tendency to form blood clots (thrombosis), which is a major cause of morbidity and mortality. Thrombosis is associated with various chronic conditions such as cancer, diabetes, renal disorders, and cardiovascular disease. The incidence and associated complications of thrombosis are likely to increase significantly in the next few decades because of aging populations. Regular exercise has been proposed to decrease the risk of developing thrombosis, although there are inconsistent data from studies investigating its effects, with reports of both increased and decreased thrombotic risk across a variety of subject cohorts. Confounders such as age, gender, hormonal variations, physical activity, underlying disease and treatment, and body composition also contribute to the difficulty in assessing and defining the precise effects of exercise in preventing thrombotic events. However, there is evidence suggesting that physical activity is beneficial for reducing thrombotic risk in younger individuals and those with chronic conditions. This article aims to summarize the known risk factors for thrombosis and briefly review the benefits of exercise in the general population. Furthermore, this article highlights the additional factors in a cohort of individuals that would (at first) appear unlikely to be at risk of thrombosis--elite athletes.

Avaliação do volume de fluxo venoso da bomba sural por ultra-sonografia Doppler durante cinesioterapia ativa e passiva: um estudo piloto

CONTEXTO: O fisioterapeuta na unidade hospitalar atua sobre os efeitos da hipoatividade ou inatividade do paciente acamado. Na prática diária, a contração do músculo da panturrilha é difundida entre os profissionais de saúde no ambiente hospitalar, principalmente nos períodos de pré e pós-operatório, como forma de diminuir a estase venosa e os riscos de trombose venosa profunda nos membros inferiores. OBJETIVO: Avaliar o volume de fluxo venoso na bomba sural, através de ultra-sonografia doppler, durante cinesioterapia ativa e passiva (flexão plantar do tornozelo). MÉTODOS: A amostra foi constituída por 30 indivíduos escolhidos aleatoriamente e submetidos a ultra-sonografia doppler da veia poplítea direita, visando mensurar o volume de fluxo sanguíneo em quatro momentos: repouso, compressão manual da panturrilha, movimentação passiva e ativa do tornozelo em flexão plantar. Na análise dos resultados, utilizou-se o teste t, sendo utilizado um valor de p < 0,05 como índice de significância estatística. RESULTADOS: Na amostra constituída, 16 eram do sexo feminino e 14 do sexo masculino, apresentando as seguintes médias: idade (31,57 anos), altura (1,68 m), peso (68,25 kg) e índice de massa corporal (24,16). Na análise estatística, a flexão plantar do tornozelo realizada de forma passiva, quando comparada ao valor basal, é significante (p < 0,000056) em relação à ativação da bomba sural, embora não tanto quanto o exercício ativo (p < 0,0000016). Também mostrou significância a compressão manual do músculo tríceps sural em relação ao exercício passivo (p < 0,000000081). CONCLUSÃO: Neste estudo, a flexão plantar do tornozelo de forma ativa mostrou-se estatisticamente mais eficaz do que a passiva na ativação da bomba sural, aumentando o volume do fluxo de sangue na veia poplítea e diminuindo a estase venosa nos membros inferiores.

Hemostatic response to acute physical exercise in healthy adolescents

The chronic and immediate post-exercise responses in the hemostatic and fibrinolytic systems have been shown to be variable and reflect differing adaptations with ageing and responses to exercise protocols. This study investigated the effects of acute and exhaustive exercise on the amplitude and duration of hemostatic and fibrinolytic responses in young adolescent males. The sample comprised 10 sedentary boys (13.2+/-0.5 years, 55.8+/-11.3kg, 165.7+/-7.4cm), who had not exercised or received any medication for at least 2 weeks before the experiments. The subjects performed exhaustive stepping exercise, consisting of 1s up and down cycles to fatigue. When the subjects were unable to maintain the required stepping rhythm, they were given a 30s recovery period. Following each 30s recovery participants recommenced the stepping cadence until fatigue prevented them continuing. Venous blood samples were drawn before and immediately, 1 and 24h after exercise to assess the following coagulation and fibrinolytic parameters: Platelet counts, activated partial thromboplastin time (aPTT), prothrombin time (PT), coagulation factor VIII (FVIII:C), von Willebrand factor (vWF), fibrinogen concentration, thrombin-antithrombin complex (TAT), D-dimer, plasminogen activator inhibitor (PAI-1), and tissue-type plasminogen activator (t-PA). Immediately following exercise, platelet counts, aPTT, FVIII, vWF and t-PA were significantly elevated in contrast to PAI-1, which decreased significantly until 1h after exercise. FVIII and platelet counts were elevated at 1 and 24h after exercise, respectively. Only the parameters FVIII and PAI-1 did not return to baseline values during the first hour after physical exercise. When compared to adults the results revealed different rates and ranges of coagulation and fibrinolysis parameters being activated by exhaustive exercise in this group of adolescents.

Effects of Mild Leg Exercise in a Seated Position on Haemostatic Parameters Under Normobaric Hypoxic Conditions

This study tested the hypothesis that in humans mild leg exercise affects haemostasis in normobaric hypoxia and thus avoids the development of a deep venous thrombosis (DVT). Eight young men breathed in a 15.4% oxygen in nitrogen gas mixture for 2 hrs while seated at rest (R) or seated and performing a 3-min mild leg exercise program (Ex) at 15-min intervals to assess the impact of mild leg exercise on haemostatic parameters related to the risk of developing DVT, as has been discussed for hypobaric hypoxic conditions during commercial airline travel. Capillary blood gases were analysed every 30 min. Heart rate was monitored continuously. Haemostatic parameters were analysed from venous blood at the beginning, after 1 and 2 hrs, and after a 30-min resting period in normoxic conditions. Plasminogen-activator-inhibitor-1 diminished in both tests in hypoxia, but not after the resting period. Antithrombin-III decreased in R in the hypoxic period. Platelet count, international normalized ratio, partial thromboplastin time remained unchanged, as did highly sensitive parameters like tissue-plasminogen-activator, α2-antiplasmin, d-dimers, thrombin-antithrombin-III-complexes, and prothrombin-fragments 1 and 2. The haematocrit decreased significantly in R. The mild leg execise prevented the decrease of antithrombin-III and caused an increase in haematocrit after an initial drop in the first hour. The present study revealed that normobaric hypoxia did not have clinically relevant effects on haemostasis in humans. Mild leg exercise carried out under those conditions did not lead, via alterations in haemostasis, to a reduced risk of DVT. Key words: local aerobic exercise, haemostasis, hypoxia, thrombosis

Cardiovascular, cerebrovascular, and respiratory changes induced by different types of music in musicians and non-musicians: the importance of silence

OBJECTIVE

To assess the potential clinical use, particularly in modulating stress, of changes in the cardiovascular and respiratory systems induced by music, specifically tempo, rhythm, melodic structure, pause, individual preference, habituation, order effect of presentation, and previous musical training.

DESIGN

Measurement of cardiovascular and respiratory variables while patients listened to music.

SETTING

University research laboratory for the study of cardiorespiratory autonomic function.

PATIENTS

12 practising musicians and 12 age matched controls.

INTERVENTIONS

After a five minute baseline, presentation in random order of six different music styles (first for a two minute, then for a four minute track), with a randomly inserted two minute pause, in either sequence.

MAIN OUTCOME MEASURES

Breathing rate, ventilation, carbon dioxide, RR interval, blood pressure, mid-cerebral artery flow velocity, and baroreflex.

RESULTS

Ventilation, blood pressure, and heart rate increased and mid-cerebral artery flow velocity and baroreflex decreased with faster tempi and simpler rhythmic structures compared with baseline. No habituation effect was seen. The pause reduced heart rate, blood pressure, and minute ventilation, even below baseline. An order effect independent of style was evident for mid-cerebral artery flow velocity, indicating a progressive reduction with exposure to music, independent of style. Musicians had greater respiratory sensitivity to the music tempo than did non-musicians.

CONCLUSIONS

Music induces an arousal effect, predominantly related to the tempo. Slow or meditative music can induce a relaxing effect; relaxation is particularly evident during a pause. Music, especially in trained subjects, may first concentrate attention during faster rhythms, then induce relaxation during pauses or slower rhythms.

Changes in fibrinolysis following exercise above and below lactate threshold

This study sought to compare fibrinolytic responses to exercise above lactate threshold (LT) to longer-duration, equicaloric exercise below LT. Fifteen males performed cycle ergometer tests above (77% VO(2)peak) and below LT (41% VO(2)peak) to comparatively evaluate tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) responses. tPA activity significantly (P < 0.05) increased during the >LT test (pre-exercise = 1.57 +/- 0.44 IU ml(-1), post-exercise = 3.85 +/- 4.72 IU ml(-1)), but not the <LT test (pre-exercise = 1.51 +/- 0.36 IU ml(-1), post-exercise = 1.94 +/- 1.00 IU ml(-1)). Plasma tPA antigen significantly (P < 0.05) increased during both the >LT (pre-exercise = 8.32 +/- 4.48 ng ml(-1), post-exercise = 14.23 +/- 5.40 ng ml(-1)) and <LT (pre-exercise = 7.40 +/- 3.52 ng ml(-1), post-exercise = 9.03 +/- 3.25 ng ml(-1)) tests. Furthermore, post-exercise tPA antigen was greater (P < 0.05) following the >LT test. PAI-1 activity significantly (P < 0.05) decreased during both the >LT (pre-exercise = 15.00 +/- 2.73 AU ml(-1), post-exercise = 10.12 +/- 2.90 AU ml(-1)) and <LT (pre-exercise = 14.51 +/- 2.80 AU ml(-1), post-exercise=12.59 +/- 2.20 AU ml(-1)) tests, and the post-exercise PAI-1 activity was significantly (P < 0.05) lower during the >LT test. Our results suggest that exercise <LT can cause fibrinolytic responses and that exercise above LT elicits greater fibrinolytic responses than equicaloric exercise performed below LT.

Comparison of t-PA and u-PA levels in maximal treadmill and deep-water running

BACKGROUND

The differences of urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator (t-PA) between maximal treadmill and deep-water running have not been reported. The purpose of this investigation was to compare u-PA and t-PA levels during maximal treadmill and deep-water running.

METHODS

Six male subjects carried out two maximal exercises, one on a treadmill and the other running in deep water using a vest. The u-PA, t-PA, total plasminogen activator inhibitor (PAI-1), epinephrine, and norepinephrine in plasma and lactate and ammonia in blood concentrations were measured after maximal exercise.

RESULTS

The blood lactate and ammonia concentrations were significantly higher in treadmill running than in deep-water running during recovery following exercise (P < 0.05). At 1 min after exercise, the plasma epinephrine, norepinephrine levels, and the u-PA and t-PA levels were higher in treadmill running compared with that in deep-water running (P < 0.05). No significant difference between the two runs was found in PAI-1 level.

CONCLUSION

The maximal treadmill running induced a greater increase in u-PA and t-PA levels than maximal deep-water running.

The effect of submaximal exercise on fibrinolysis

We studied the relationship between sustained submaximal exercise, increased tissue plasminogen activator (t-PA) levels and decreased hepatic clearance of t-PA. Six healthy male volunteers exercised for 35 min while receiving constant rate infusions of either saline or two different doses of recombinant t-PA for 90 min (40 min before, 35 min during and 15 min after exercise). Liver blood flow was estimated simultaneously by constant rate indocyanine green infusion. Since t-PA is cleared rapidly by the liver in direct proportion to liver blood flow, it was expected that a significant decrease in liver blood flow during sustained submaximal exercise would be associated with a proportional increase in plasma t-PA. During submaximal exercise with a saline (placebo) infusion, steady-state t-PA antigen increased from a resting baseline of 6.3 +/- 3.1 to 15.1 +/- 5.1 ng/ml; with a 20 microg/min t-PA infusion, t-PA antigen increased from 33 +/- 12 to 84 +/- 25 ng/ml during exercise; and with a 40 microg/min t-PA infusion, t-PA antigen increased from 77 +/- 38 to 166 +/- 42 ng/ml during exercise. During submaximal exercise, liver blood flow fell on average 71, 68 and 70%, respectively, during the three procedures, while calculated t-PA clearance decreased on average 59, 59 and 53%. t-PA concentration versus time curves, displayed in proportional units, were similar. The comparable relative increases in endogenous and exogenous t-PA with simultaneous proportional decreases in liver blood flow suggests that diminished hepatic t-PA clearance is the major cause of increased t-PA concentration and blood fibrinolytic activity enhancement during sustained submaximal exercise.

Effects of strenuous exercise on haemostasis

OBJECTIVES

To review the effects of exercise on haemostasis and examine the possible clinical sequelae of these changes.

METHODS

The search strategy included articles from 1966 to August 2002 using Medline and SportDiscus databases, and cross referencing the bibliographies of relevant papers.

RESULTS

Exercise results in activation of both the coagulation and fibrinolytic cascades, as shown by a reduction in whole blood clotting time and activated partial thromboplastin time, an increase in the activity of several components of the cascades, and an increase in fibrin degradation products. In vitro tests suggest that coagulation remains activated after fibrinolysis has returned to baseline levels.

CONCLUSIONS

Both the coagulation and fibrinolytic cascades are stimulated by strenuous exercise, but the temporal relation between the two and its clinical significance remains to be clarified. Doctors and athletes should be aware of the haemostatic changes induced by exercise, and further work is needed to clarify the possible role of these changes in sudden cardiac death.

Exercise-induced changes in coagulation and fibrinolysis in healthy populations and patients with cardiovascular disease

This review highlights the clinical significance of coagulation and fibrinolytic responses, and adaptations in healthy individuals and patients with cardiovascular disease (CVD). Much of the review focuses on indicators of the potential for coagulation and fibrinolysis. The terms 'coagulation potential' and 'fibrinolytic potential' are used frequently, as much of the literature in the area of exercise haemostasis evaluates factors that reflect an increased potential for coagulation, while coagulation per se, may or may not be occurring. Similarly, fibrinolysis is definitively the lysis of inappropriate or excessive blood clot, which may or may not be occurring when the enzymes that stimulate fibrinolysis are activated. Nevertheless, markers of coagulation and fibrinolytic potential are associated with CVD, ischaemic events, and cardiovascular mortality. Additionally, fibrinolytic potential is associated with other established CVD risk factors. Ischaemic events triggered by physical exertion are more likely to occur due to an occlusive thrombus, suggesting the exercise-induced responses related to haemostasis are of clinical significance. The magnitude of increase in coagulation potential, platelet aggregation and fibrinolysis appears to be primarily determined by exercise intensity. Patients with CVD may also have a larger increase in coagulation potential during acute exercise than healthy individuals. Additionally, the magnitude of the fibrinolytic response is largely related to the resting fibrinolytic profile of the individual. In particular, high resting plasminogen activator inhibitor-1 may diminish the magnitude of tissue plasminogen activator response during acute exercise. Therefore, acute responses to exercise may increase the risk of ischaemic event. However, chronic aerobic exercise training may decrease coagulation potential and increase fibrinolytic potential in both healthy individuals and CVD patients. Due to the aforementioned importance of resting fibrinolysis on the fibrinolytic response to exercise, chronic aerobic exercise training may cause favourable adaptations that could contribute to decreased risk for ischaemic event, both at rest and during physical exertion.

Exercise and Training Effects on Blood Haemostasis in Health and Disease

In recent years, the dysfunction of the haemostatic system in relation to the clinical complications from arterioscleroses and cardiovascular diseases has become more recognised. Blood coagulation and fibrinolysis comprise two important physiological systems, which are regulated by a balance between activators and inhibitors. Activation of blood coagulation is associated with accelerated clot formation, whereas activation of blood fibrinolysis enhances the breakdown of the blood clot. Available evidence suggests that strenuous exercise induces activation of blood coagulation with simultaneous enhancement of blood fibrinolysis. Although the responses of blood coagulation and fibrinolysis appear to be related to the exercise intensity and its duration, recent reports suggest that moderate exercise intensity is followed by activation of blood fibrinolysis without concomitant hyper-coagulability, while very intense exercise is associated with concurrent activation of blood coagulation and fibrinolysis. Similar to blood coagulation and fibrinolysis, systemic platelet-related thrombogenic factors have been shown to be involved in the initiation and progression of atherogenesis and plaque growth. Although exercise effects on platelet aggregation and function in healthy individuals have been examined, the results reported have been conflicting. However, for patients with coronary heart disease, the balance of evidence available would strongly suggest that platelet aggregation and functions are increased with exercise. Few studies are available concerning the influence of training on blood coagulation and fibrinolysis and the exact effects of exercise training on the equilibrium between blood coagulation and fibrinolysis is not as yet known. Although the effects of physical training on platelets have been briefly investigated, available meagre evidence suggests that exercise training is associated with favourable effects on platelet aggregation and activation in both men and women.

A single bout of walking exercise enhances endogenous fibrinolysis in stroke patients

PURPOSE

Impaired endogenous fibrinolysis is an important predictor for increased risk of stroke and myocardial infarction. Acute exercise can enhance fibrinolysis, primarily by stimulating short-term increases in plasma tissue plasminogen activator (tPA), which is postulated to protect against atherothrombotic events. No prior studies have examined the fibrinolytic response to exercise in stroke survivors despite their high risk for recurrent stroke and myocardial infarction. The purpose of this study was to assess the fibrinolytic response to acute submaximal exercise in chronic hemiparetic stroke patients.

METHODS

Eighteen (16 men, 2 women) untrained stroke patients with chronic hemiparetic gait deficits volunteered for participation in this single session exercise study. Fasting blood samples for determination of tPA and plasminogen activator inhibitor (PAI-1) enzyme activities were obtained before, immediately after, and 60 min after submaximal treadmill walking. Patients walked at 60% maximal heart rate reserve (low-moderate intensity) for a cumulative total of 20 min.

RESULTS

The exercise bout increased tPA activity by 79% (P < 0.01) and decreased PAI-1 activity by 18% (P < 0.01). At 1 h after completing the walking exercise, plasma tPA activity levels were still significantly elevated (43%,P < 0.01), and PAI-1 activity levels were 25% lower (P < 0.01) than baseline.

CONCLUSIONS

These findings demonstrate that a single bout of aerobic walking exercise can improve fibrinolysis profiles in chronic stroke patients. Significant increases in endogenous tPA and reductions in PAI-1 activity persist for at least 1 h after exercise cessation. The implications are that alterations in physical activity during the day may modify clot lysing potential, thereby affecting atherothrombotic risk.

Clotting and fibrinolytic activity change during the 1 h after a submaximal run

PURPOSE

To determine the changes in clotting and fibrinolytic activity during the 1-h period after an acute submaximal exercise at a specific relative exercise intensity to ascertain whether during this time there is a greater risk for developing a clot formation or thrombus.

METHODS

Ten healthy men reported between 0700 and 1000 h and ran at 70-75% VO2max or walked at 1.2 mph for 30 min in a random counter-balanced order. Venous blood was obtained at rest, immediately after, and every 20 min during the 1-h recovery.

RESULTS

There were no differences in the resting parameters for each treatment. Walking did not alter the activity of any of the measures analyzed compared with rest. Clotting indicators activated partial thromboplastin time (APTT) was significantly decreased by approximately 2 s and remained at this level during the 1-h recovery, and factor VIII activity was elevated 66% immediately after the run and remained elevated at this level during the 1-h recovery period. Fibrinolytic indicators, t-PA, and D-dimers were significantly increased immediately after the run. However, t-PA demonstrated a quadratic negative slope during the 1-h recovery time. D-dimers remained elevated during the 1-h recovery time.

CONCLUSIONS

These results suggest that running at 70-75% VO2max resulted in elevated clotting and fibrinolytic activity. However, the clotting activity was sustained during a time when fibrinolytic activity declined, which suggests a more favorable situation for clot formation during this time after exercise.

Absolute versus relative intensity of physical activity in a dose-response context

PURPOSE

To examine the importance of relative versus absolute intensities of physical activity in the context of population health.

METHODS

A standard computer-search of the literature was supplemented by review of extensive personal files.

RESULTS

Consensus reports (Category D Evidence) have commonly recommended moderate rather than hard physical activity in the context of population health. Much of the available literature provides Category C Evidence. It has often confounded issues of relative intensity with absolute intensity or total weekly dose of exercise. In terms of cardiovascular health, there is some evidence for a threshold intensity of effort, perhaps as high as 6 METs, in addition to a minimum volume of physical activity. Decreases in blood pressure and prevention of stroke seem best achieved by moderate rather than high relative intensities of physical activity. Many aspects of metabolic health depend on the total volume of activity; moderate relative intensities of effort are more effective in mobilizing body fat, but harder relative intensities may help to increase energy expenditures postexercise. Hard relative intensities seem needed to augment bone density, but this may reflect an associated increase in volume of activity. Hard relative intensities of exercise induce a transient immunosuppression. The optimal intensity of effort, relative or absolute, for protection against various types of cancer remains unresolved. Acute effects of exercise on mood state also require further study; long-term benefits seem associated with a moderate rather than a hard relative intensity of effort.

CONCLUSIONS

The importance of relative versus absolute intensity of effort depends on the desired health outcome, and many issues remain to be resolved. Progress will depend on more precise epidemiological methods of assessing energy expenditures and studies that equate total energy expenditures between differing relative intensities. There is a need to focus on gains in quality-adjusted life expectancy.

The effect of alcohol ingestion on the exercise-induced changes in fibrin and fibrinogen degradation products in man

The present study examined the influence of ingesting a moderate dose of alcohol on plasminogen activator activity (t-PA), plasma fibrinogen (Fb), total degradation products (TDP) and the degradation products of fibrin (FbDP) and fibrinogen (FgDP) at rest and in response to exercise. Eleven male subjects performed two separate experimental trials at an exercise intensity corresponding to 70% maximal oxygen consumption for 35 min. Prior to trials, subjects were either given 0.5 g/kg alcohol in orange-flavoured drink or an equal volume of non-caloric non-alcoholic drink 45 min before exercise. Comparison of the levels of t-PA, Fb, TDP, FbDP, and FgDP at rest, before and 45 min after the ingestion of alcohol revealed no significant differences between alcohol and control experiments. Exercise resulted in a marked increase in t-PA, TDP, and FgDP, with no appreciable change in FbDP. Although plasma fibrinogen level showed significant decrease post-exercise when subjects ingested alcohol, this difference was small and its biological significance is questionable. While t-PA level increased similarly in response to exercise during alcohol and control trials, a significantly higher response of TDP was found during the control trial compared with alcohol trial. It was concluded that exercise with and without alcohol ingestion is followed by a substantial increase in t-PA, which coincided with an increase in TDP. The increase in TDP was mainly due to an increase in FgDP, but not to FbDP. These findings support the hypothesis that a significant fibrinogenolysis occurs in response to exercise, and moderate intoxication with alcohol prior to exercise reduced this response.

Blood hemostasis in exercise and training

Formation of the blood clot is a slow but normal physiological process occurring as a result of the activation of blood coagulation pathways. Nature's guard against unwanted blood clots is the fibrinolytic enzyme system. In healthy people, there is a delicate dynamic balance between blood clot formation and blood clot dissolution. Available evidence suggests that exercise and physical training evoke multiple effects on blood hemostasis in normal healthy subjects and in patients. A single bout of exercise is usually associated with a transient increase in blood coagulation as evidenced by a shortening of activated partial thromboplastin time (APTT) and increased Factor VIII (FVIII). The rise in FVIII is intensity dependent and continues into recovery. The effects of acute exercise on plasma fibrinogen have yielded conflicting results. Thus, the issue of whether exercise-induced blood hypercoagulability in vitro mirrors an in vivo thrombin generation and fibrin formation remains disputable. Exercise-induced enhancement of fibrinolysis has been repeatedly demonstrated using a wide range of exercise protocols incorporating various exercise intensities and durations. Moderate exercise appears to enhance blood fibrinolytic activity without a concomitant activation of blood coagulation mechanisms, whereas, very heavy exercise induces simultaneous activation of blood fibrinolysis and coagulation. The increase in fibrinolysis is due to a rise in tissue-type plasminogen activator (tPA) and decrease in plasminogen activator inhibitor (PAI). The mechanism of exercise-induced hyperfibrinolysis is poorly understood, and the physiological utility of such activation remains unresolved. Strenuous exercise elicits a transient increase in platelet count, but there are conflicting results concerning the effect of exercise on platelet aggregation and activation. Few comprehensive studies exist concerning the influence of exercise training on blood hemostasis, making future investigation necessary to identify whether there are favorable effects of exercise training on blood coagulation, fibrinolysis, and platelet functions.

The effect of moderate alcohol ingestion on blood coagulation and fibrinolysis at rest and in response to exercise

The effect of alcohol ingestion before exercise on blood haemostasis is not known. The present study examined the effects of moderate alcohol ingestion on blood haemostatic variables at rest and in response to exercise. Eleven normal healthy individuals randomly performed two tests separated by 7 days. A moderate dose of ethanol (0.5 g.kg-1) was administered before one test, whereas an equal volume of an alcohol-free drink was administered before the other. Forty-five minutes after the ingestion of either drink, the participants cycled at 65% VO2max for 30 min followed by a 5-min all-out performance. Venous blood samples were obtained before and 45 min after the ingestion of both drinks, and also immediately after exercise. Exercise induced a significant increase in tissue-type plasminogen activator activity and antigen, and factor VIII procoagulant activity. The post-exercise data also showed a significant decrease in plasminogen activator inhibitor activity and soluble fibrin, with a significant shortening in prothrombin time and activated partial thromboplastin time, but not thrombin time. No significant changes were observed in antithrombin III. Although no significant differences were found between trials in the haemostatic and fibrinolytic variables at rest, a significant decrease in fibrinogen concentration was observed after exercise in the alcohol trial. This suggests that ingesting a moderate dose of alcohol does not alter blood coagulation and fibrinolysis at rest. Apart from fibrinogen concentration, which was significantly decreased after exercise in the alcohol trial, most of the haemostatic and fibrinolytic variables were not affected by alcohol. The mechanism responsible for the decrease in fibrinogen following exercise in the alcohol trial remains unknown, but might be related to inhibition of fibrinogen synthesis by the liver or an enhanced rate of its catabolism.

Fibrinolytic activity is similar in physically active men with and without a history of myocardial infarction

The purpose of this study was to evaluate fibrinolytic potential at rest and after a fibrinolytic stressor in men with a history of myocardial infarction (MI) compared with an age- and activity-matched group of men without coronary artery disease (CAD). All men were currently enrolled in exercise programs. Tissue-type plasminogen activator (TPA) and plasminogen activator inhibitor 1 (PAI-1) activity and antigen levels were measured at rest and after a maximal exercise test. A 2 x 2 (group x time) ANOVA with repeated measures was used to evaluate fibrinolytic potential. Bivariate regressions were conducted to evaluate relations between fibrinolytic potential and maximal oxygen uptake (VO2max). Age was similar between groups (CAD, 57.5 +/- 6.6; non-CAD, 58.1 +/- 7.3 years); however, VO2max was higher in non-CAD subjects (36.2 +/- 6.2 vs 27.5 +/- 5.9 mL.kg-1.min-1). Mean +/- SEM resting TPA and PAI-1 activities were similar between CAD and non-CAD subjects (TPA, 2.8 +/- 0.2 vs 2.8 +/- 0.2 IU/mL; PAI-1, 15.9 +/- 3.1 vs 13.1 +/- 4.1 AU/mL). Both groups showed similar significant increases in TPA activity with exercise (P < .05), and postexercise TPA activity was also similar (CAD, 9.1 +/- 2.0 IU/mL; non-CAD, 11.7 +/- 2.6 IU/mL). Both groups also showed similar significant decreases in PAI-1 activity with exercise (P < .05) and no differences in postexercise PAI-1 activity (CAD, 13.2 +/- 2.5 AU/mL; non-CAD, 10.4 +/- 3.6 AU/mL). Significantly higher resting TPA antigen levels were seen in CAD (14.8 ng/mL) than non-CAD (10.2 ng/mL) subjects (P < .05), but neither group showed significant changes with exercise (CAD, 12.9 ng/mL; non-CAD, 11.8 ng/mL). Resting PAI-1 antigen was similar in the two groups (CAD, 71.4 ng/mL; non-CAD, 74.2 ng/mL) and did not significantly change with exercise (CAD, 77.9 ng/mL; non-CAD, 72.3 ng/mL). VO2max was positively correlated with postexercise TPA activity (r = .52, P < .05) and negatively correlated with resting TPA antigen (r = -.43, P < .05). Resting TPA antigen was also directly correlated with body mass index (r = .63, P < .05). The finding that functional fibrinolytic activity was not different in physically active men with and without CAD contrasts with previous reports. This suggests that matching subjects on the bases of age and habitual physical activity status and controlling exercise intensity are important factors to consider when evaluating fibrinolytic potential.