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PubMed1994

The influence of thrombolytic therapy on the predictive value of exercise testing 3 weeks after acute myocardial infarction.

OBJECTIVES: To evaluate the prognostic value of exercise testing performed soon after acute myocardial infarction (AMI) in patients treated with thrombolytic therapy. DESIGN: A 1-year prospective follow-up of 185 subjects treated with thrombolytic therapy who survived AMI, and who performed exercise testing 3 weeks after AMI. These patients were compared with 272 patients not receiving thrombolytic therapy during the same period. SUBJECTS: Patients recovering from AMI, without medical contraindications to exercise testing performed 3 weeks after AMI. MAIN OUTCOME MEASURES: ST-segment deviations during exercise testing 3 weeks post-AMI were related to clinical outcome 1-year post-AMI and to the administration of thrombolytic therapy during the acute phase of infarction. RESULTS: In patients treated with thrombolytic therapy, the only exercise-test-related parameter predicting subsequent cardiac events was ST-segment elevation. In contrast, patients not receiving thrombolytic therapy and demonstrating ST-segment depression of > or = 1 mm during exercise had more clinical cardiac events than those without this finding (12.3 vs. 3.9%; P < 0.05). CONCLUSION: This study casts doubt on the ability of exercise testing to select a high-risk population requiring early intervention to prevent recurrent coronary events after thrombolysis for AMI.

Adult↗
PubMed1989

[A prospective study of future cardiac events in subjects who underwent treadmill exercise testing].

The prognostic value of the exercise testing as well as coronary risk factors was assessed in 890 patients (pts) with a history of myocardial infarction (MI, n = 114) or chest pain (typical angina; TA, n = 134, others; OTH, n = 642) in relation to cardiac events (cardiac death, non-fatal MI). Clinical questionnaires and symptomatic-maximal graded treadmill exercise were performed in all pts. Follow-up was obtained prospectively by mail or telephone interview annually. Twenty eight pts were lost to follow-up. In the remaining 862 pts (96.9%), the mean follow-up duration was 3.1 +/- 1.4 (mean +/- SD) years. During follow-up period, 39 cardiac events (21 cardiac death, 18 non-fatal MI) (4.5%) occurred. Cardiac event rates in pts with MI, TA, and OTH were 16.2%, 9.8%, and 1.3%, respectively. Univariate analyses revealed that the event rate was influenced by age, sex (male), hypertension, diabetes mellitus, and HDL-cholesterol among coronary risk factors, and by anginal pain during exercise, ST depression, poor exercise tolerance, and abnormal blood pressure response among treadmill exercise findings. By Cox proportional hazard model analysis, the history of MI, age, TA, and ST depression (within 6 minutes of Bruce protocol) was significantly independent predictors for future cardiac events in all pts; and age, sex, and TA in pts without MI. In conclusion, the exercise testing combined with conventional coronary risk factor analysis was effective means in predicting future cardiac events.

Adult↗
PubMed1989

Prevalence and clinical significance of silent myocardial ischemia in exercise test.

Prevalence of silent myocardial ischemia in exercise test was retrospectively reviewed from 749 tests performed for 513 patients with definite evidence of ischemic heart disease. The clinical significance was studied and absence of transient ischemia, occurrence of transient ischemia with and without pain were observed in 48%, 30% and 22% of the tests, respectively. Anginal pain was frequently observed in exercise tests for patients with severe coronary artery disease and low exercise tolerance. A large number of tests showing ischemic response were discontinued due to symptoms other than anginal pain and hence silent myocardial ischemia could be thought to be a result of ischemic state which does not reach the angina threshold. Silent myocardial ischemia was frequently observed during usual daily life. However, a definite correlation between severity of transient ischemia and presence or absence of chest pain in the same individuals was not obtained from the study. A day to day variation in the angina threshold might be responsible. In general, silent myocardial ischemia was not rare. However, the consistent condition was very unusual. In angina of effort (EA) and old myocardial infarction (OMI), 3.7% and 12.3% were silent, respectively. A higher incidence was obtained in OMI than in EA. This is important for the management of these patients. The mechanism of silent myocardial ischemia and the cause of the different incidence of this state between EA and OMI were not defined and remained to be further studied.

Angina Pectoris↗
PubMed1993

First myocardial infarction in patients under 60 years old: the role of exercise tests and symptoms in deciding whom to catheterise.

OBJECTIVE: To determine the role of exercise tests and assessment of angina in the detection of potentially threatening disease in young patients with infarcts. DESIGN: Elective readmission of patients at a mean (SD) of 60 (30) days after acute myocardial infarction for assessment of angina, treadmill exercise tests, and cardiac catheterisation. SETTING: Cardiology department of a teaching hospital. PATIENTS: 186 consecutive survivors, aged under 60 years and discharged from the coronary care unit after a first myocardial infarction. MAIN OUTCOME MEASURES: Coronary arteriography, presence of angina, result of exercise tests, and referral for revascularisation. RESULTS: 31% of patients had either two vessel disease (with proximal left anterior descending involvement), three vessel disease, or left main stem disease. 49% of all patients had angina. Of the 173 patients who had an exercise test 34% had 1 mm and 24% had 2 mm of exercise induced ST depression. Thirty percent had no angina and a negative exercise test: after a mean (SD) follow up of 16 (4) months none of this symptom free sub-group had died, had experienced a further myocardial infarction, or had been referred for revascularisation. 79% of patients with either two vessel disease (with proximal left anterior descending involvement), three vessel disease, or left main stem disease had either angina or a 1 mm ST depression during the exercise test. CONCLUSION: Patients without cardiac pain after myocardial infarction and without ST changes during an exercise do not need arteriography.

Adult↗
PubMed1986

Post-infarction exercise testing in patients under 55 years. Relation between ischaemic abnormalities and the extent of coronary artery disease.

Previous studies have suggested that the early post-infarction exercise test is useful in predicting the extent of coronary artery disease. The results of a heart rate limited exercise test three weeks after infarction and a symptom limited exercise test six weeks after infarction obtained by both standard lead electrocardiograms and 16 lead precordial maps were compared in 100 consecutive survivors of acute myocardial infarction under 55 years of age. Exercise tests were defined as being positive on the basis of angina, ST segment depression greater than or equal to 1 mm in any electrocardiogram lead, or exertional hypotension. Multivessel disease, that is two or three vessel disease, was present in 60 patients, and three vessel disease in 22 patients. The sensitivity, specificity, and predictive value for multivessel disease of the three week test were 38%, 83%, and 76% respectively; and results for the six week test were 55%, 75%, and 77% respectively. Only 32% of patients with three vessel disease were identified at the three week test, and 59% at the six week test. Significantly more patients with multivessel and three vessel disease were identified by the symptom limited six week test. Precordial mapping offered no advantages over the standard 12 lead electrocardiogram in either the identification of patients with multivessel disease or the prediction of the distribution of coronary artery disease. Angina pectoris during the exercise test at six weeks was the single most useful predictor of multivessel disease. Multivessel disease was found in 27 (87%) of the 31 patients with angina with or without ST depression during the test at six weeks compared with 33 (48%) of the 69 patients who did not have angina during the test at six weeks. Exercise testing in the early post-infarction period in patients under 55 years of age is of limited value in predicting the extent of coronary artery disease. It is, therefore, unreasonable to use such exercise tests to select patients for coronary arteriography after myocardial infarction. None the less angina pectoris occurring during a symptom limited exercise test six weeks after infarction is a strong predictor of multivessel disease, and coronary arteriography is recommended in these patients.

Adult↗
PubMed1994

Method of expired gas collection during cardiopulmonary exercise testing does not affect respiratory gas exchange measurements in patients with heart failure.

Cardiopulmonary exercise testing is commonly used to assess patients with heart failure. Analysis of expired gases during exercise requires the use of either a facemask or mouthpiece with nose clip. The authors sought to determine if the method of expired gas collection during exercise testing (facemask or mouthpiece) influences gas exchange measurements in patients with heart failure. Nine patients with heart failure performed two maximal treadmill tests. Expired gases were collected with a facemask in one exercise test and a mouthpiece in the other. There were no significant differences in exercise test duration, peak oxygen uptake, heart rate, respiratory exchange ratio, or perceived exertion during maximal exercise performed with the facemask when compared to the mouthpiece. Test subjects reported that the overall comfort of the facemask was significantly greater than that of the mouthpiece (P < .02). The method of expired gas collection during cardiopulmonary exercise testing does not significantly affect measures of gas exchange or exercise performance in patients with heart failure. Heart failure patients find the overall comfort of the facemask superior to that of the mouthpiece, but this comfort preference does not affect exercise performance.

Exercise Test↗
PubMed2000

[Effect of trimetazidine on biological activity of neutrophils in patients with transient myocardial ischemia induced by exercise testing].

We estimated the effect of trimetazidine on biological activity of neutrophils in patients with exercise test--induced transient myocardial ischaemia. The study group comprised 16 patients (10 men and 6 women) aged 40-56 years (mean 48.2 years) with stable angina. Exercise test was performed on cycloer-gometer (Medicor, Hungary). Trimetazidine in a dose 3 x 20 mg/day was applied 24 hours prior to the exercise test. The control group consisted of 14 patients (9 men and 5 women) aged 37-59 years (mean 47.9 years), with stable angina, in whom exercise test was performed but the drug was not administered. Blood samples for examination were taken from basilic vein before the exercise test and 10 min afterwards. To evaluate the ability of neutrophils to aggregate the leukergy test of Fleck modified by Berliner and Aronson was applied. Oxidative metabolism of nonstimulated and stimulated by fMLP and PMA was measured using chemiluminescence method. It was shown that in patients with stable angina trimetazidine caused decrease in neutrophil aggregation. The drug did not inhibit neutrophil biological activity af-ter exercise test--induced myocardial ischaemia.

Adult↗
PubMed1989

Improving the validity of clinical exercise testing: the relationship between practice and performance.

Many studies involving exercise testing fail to address the issue of practice. Those that do vary considerably with respect to the parameters of practice used. We evaluated the effect of two standardized practices on a horizontal submaximal exercise test performed on a treadmill. Healthy men (n = 20) with no previous treadmill exposure were alternately assigned to the experimental (practice) or control (no practice) group. Heart rate (HR), systolic blood pressure (SBP), rate pressure product (RPP), step cadence (CAD) and perceived exertion (PE) were recorded at the end of each work load of the practices and/or tests. We observed no significant differences in these variables over the common work loads for the first practice session in the experimental group and the exercise test in the control group (p greater than 0.05). The two groups were homogeneous with respect to fitness and magnitude of arousal on initial exposure to the treadmill. During the submaximal test, HR, SBP, RPP, CAD, and PE were systematically lower for the experimental group than for the control group. The SBP and RPP were significantly lower in the experimental group (p less than 0.01). The CAD tended toward statistical significance (p less than 0.07), whereas HR and PE were not significantly different for the two groups (p greater than 0.05). When the four common work loads were compared over the two practices and the exercise test for the experimental group, SBP and CAD were significantly higher for practice 1 than for practice 2 and the test (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[The simultaneous evaluation of preoperative cardiopulmonary functions of esophageal cancer patients in the analysis of expired gas with exercise testing].

By analyzing expired gas with exercise testing, we examined the relationship between test results and postoperative cardiopulmonary complications. The analysis was evaluated for its accuracy and reliability in comparison with general pulmonary function tests including spirometry, flow volume curves, diffusing capacity and arterial blood gas analysis. Enrolled were 52 of patients admitted between a period from 1991 to 1993 for thoracic esophageal cancer, who underwent a radical operation of right thoracolaparotomy. Patients were divided into two groups according to postoperative cardiopulmonary complications; one with complications (group C, n = 11) and the other without complication (group NC = 41). The two groups were compared in maximum oxygen consumption (VO2 max)/m2, anaerobic threshold (AT)/m2, VC/m2, %VC, FEV1.0/m2, V25/m, V50/V25, %DLCO and PaO2. In the results, there were significant differences between the two groups only in VO2 max/m2 (p < 0.001), AT/m2 (p < 0.001), and V50/V25 (p < 0.05), while there were no significant differences between the two groups in VC/m2, %VC, FEV1.0/m2, FEV1.0%, V25/m, %DLCO or PaO2. The above results suggest that analysis of expired gas with exercise testing is able to measure easily both cardiac and pulmonary reserve forces, which conventional pulmonary function tests are unable to do, and is evaluating surgical indications for esophageal cancer patients and predicting postoperative cardiopulmonary complications.

Adult↗
PubMed1985

Comparison of clinical variables and variables derived from a limited predischarge exercise test as predictors of early and late mortality after myocardial infarction.

An exercise test limited to 5 METS or 70% of age-predicted maximal heart rate was performed 1 day before hospital discharge by 225 survivors of acute myocardial infarction, all of whom were subsequently followed up for at least 5 years. The mortality rate was 11.1% during the first year, but averaged only 2.9% per year from the second to fifth year. Over the entire follow-up period, the five variables that predicted mortality by multivariate analysis were QRS score, an exercise-induced ST segment shift, previous infarction, failure to achieve target heart rate or work load and ventricular arrhythmia during the exercise test. Because mortality differed markedly before and after 1 year, Cox regression analyses were performed separately for both of these periods. The factors that were predictive of mortality during the first year were an exercise-induced ST shift (p less than 0.0001, relative risk 7.8), failure to increase systolic blood pressure by 10 mm Hg or more during exercise (p = 0.0039, relative risk 4.3) and angina in hospital 48 hours or longer after admission (p = 0.0046, relative risk 3.4). None of these three variables was predictive of mortality after 1 year. Previous infarction (p = 0.0007), QRS score (p = 0.0042) and ventricular arrhythmia during the exercise test (p = 0.016) were predictive of mortality after the first year. Thus, clinical and exercise test variables are complementary predictors of mortality after myocardial infarction. An abnormal ST segment response during an early limited exercise test and angina in the hospital are common strong predictors of mortality to 1 year, but not thereafter. Late mortality correlates with markers of poor left ventricular function.

Adult↗
PubMed1994

Does thrombolysis affect the prognostic value of the post-infarct exercise test?

There has been some debate on usefulness of the exercise test in risk stratification after myocardial infarction in the thrombolytic era. This was assessed in 295 patients of whom 184 were treated with thrombolysis. Each had an exercise test using a modified Naughton protocol within 14 days of acute myocardial infarction. The tests were graded as high risk positive (112), low risk positive (83), or negative (100). These gradings predicted use of multiple drug therapy (p = 0.05), severity of coronary artery disease (p < 0.01), and coronary artery bypass grafting (p < 0.01). There was no influence on heart failure, recurrent myocardial infarction or death. This was independent of the use of thrombolytic therapy. The whole group had a good prognosis with a mortality of 2.4% after 56 weeks' follow-up. The exercise test is still a useful screening test after myocardial infarction. In this study, there was a high negative predictive accuracy of 91% for any event. Its use is not altered by thrombolysis. The finding of a lack of influence of the exercise test on major events may be a reflection of the current good prognosis after myocardial infarction and the prompt use of revascularisation.

Adult↗
PubMed1997

Comparison of maximum versus submaximum exercise testing in providing prognostic information after acute myocardial infarction and/or coronary artery bypass grafting.

Exercise testing after acute myocardial infarction (AMI) provides prognostic information. In many studies submaximum exercise tests performed until a given work load, metabolic equivalents (METs) level, or heart rate were used or patients discontinued the exercise test prematurely because of symptoms. We showed recently that peak oxygen uptake during maximum exercise provides independent prognostic information in patients with coronary artery disease. It is, however, not known whether maximum exercise testing is superior in predicting mortality than testing until a target level. Second, it is unclear which target end point best classifies patients at increased risk. Therefore, the independent relation between mortality and indexes of, respectively, maximum and submaximum exercise capacity, were analyzed in 527 patients, who were tested until exhaustion. To express submaximum exercise capacity dichotomous variables (the ability to reach a target METs level or not), and a continuous variable relative to maximum exercise capacity (the ventilatory anaerobic threshold) were used. After adjustment for significant covariates, peak oxygen uptake was significantly related to all-cause and cardiovascular mortality. The target level of 5 METs and the ventilatory anaerobic threshold, when expressed in absolute workload, were related to mortality when unadjusted, but after adjustment for age and other confounders significancy was lost. In multiple Cox regression analysis, the prognostic power of peak oxygen uptake remained significant when 5 METs or the anaerobic threshold were forced into the equations. When analyzing the relation of various METs levels with mortality, the 7 METs level was independently related to all-cause and cardiovascular mortality and yielded the highest diagnostic accuracy. We conclude that maximum exercise testing is more potent in predicting mortality than the ability to reach a predetermined level of exercise, such as the commonly used 5 METs level or the anaerobic threshold. Otherwise, the use of a higher target level of 7 METs is recommended.

Adult↗
PubMed1984

Exercise testing for patients after myocardial infarction and coronary bypass surgery: emphasis on predischarge phase.

Data from the preceding low-level exercise test studies have been compiled and are presented in Table II. The table is arranged according to groups of prognostic indicators for future coronary events or indicators for those patients with multivessel coronary artery disease. In summary, current studies demonstrate safety and predictive value in predischarge low-level exercise testing in patients after myocardial infarction. If the test reveals a positive S-T segment change or angina or both, the predictive value for future cardiac events is significant. In addition, a limited duration on the exercise test, a flat or falling blood pressure response, and the presence or absence of premature ventricular depolarizations add to this predictive value. A more sophisticated technique that employs radionuclide ventriculography may add to the sensitivity and specificity of these various tests but should be used selectively. Post-myocardial infarction patients who perform low-level exercise testing prior to discharge and demonstrate no exercise-induced abnormality from baseline may also harbor multivessel coronary disease, and this group of patients needs to be carefully followed. Testing at 3 weeks and 6 weeks after infarction may be beneficial in revealing additional clinical data. Less data are currently available on predischarge low-level exercise testing in patients with myocardial revascularization. However, these limited data support both feasibility and safety of low-level exercise testing in myocardial revascularization patients before discharge. Prognostic data with regard to low-level exercise testing for this group of patients should be forthcoming. Data from low-level exercise testing need to be incorporated during the in-hospital phase to eliminate unnecessary testing as the patient proceeds home and/or to medically supervised exercise programs. Proper therapeutic modalities based on these data should be included. In accord with this, it is imperative that the cardiac rehabilitation team or exercise testing laboratory correspond directly with the private physician regarding all clinical data and recommendations for discharge activity. Follow-up exercise testing for patients after myocardial infarction and coronary bypass surgery utilizes end points similar to those of predischarge low-level testing and therefore will not be discussed in detail. In general the patient should be able to achieve a higher heart rate or MET level in follow-up testing.(ABSTRACT TRUNCATED AT 400 WORDS)

Angina Pectoris↗
PubMed2001

Exercise testing in special situations: ER, preoperative and disability evaluation.

In a number of medical centers, exercise testing has proven to be a safe and useful tool in the evaluation of patients presenting chest pain in an emergency room. At these centers, after a period of observation without evidence of acute myocardial infarction, exercise testing is done. If the exercise test result is normal, the patient is discharged from the emergency room, without being admitted to the hospital. Exercise testing is a well-accepted noninvasive method to evaluate at-risk patients being considered for elective noncardiac surgery. Exercise testing is frequently used to determine functional capacity during disability assessment.

Chest Pain↗
PubMed1993

A survey of exercise testing practice in Scottish hospitals.

A 1989 survey (unpublished) of exercise testing practice in Scotland suggested that there were important differences in the practice of exercise testing between hospitals. A postal questionnaire was sent to 30 teaching and district general hospitals in 1991 and followed up by telephone questioning of consultants. The numbers of exercise tests performed had increased to 22,012 in 1990, and a greater proportion were performed in district general hospitals. General practitioners had very limited access to the service but hospital doctors of any grade had almost free access. Rationing of early post myocardial infarction testing led to attempts to define "high risk" post infarction patients and this included inappropriate patients in many hospitals. A variety of different protocols was used. Eighteen out of 30 hospitals surveyed discontinued beta blockers but only four hospitals took account of antianginal, antihypertensive or other medication, and all but one exercised patients while on digoxin. In the majority of hospitals decisions regarding drug therapy were taken by individual physicians. A variety of personnel reported tests, many without specialist training in cardiology. Even among consultants there was no concerns on the degree of ST depression which was significant. Exercise tests performed in different hospitals in Scotland are not comparable due to the wide variation in patient selection, test conditions, and interpretation of tests. This problem is likely to be exacerbated by the multiple personnel involved in all aspects of testing. It seems probable that there is a problem throughout the United Kingdom, and that there is a need for guidelines.

Exercise Test↗
PubMedDate not supplied

Cardiopulmonary exercise testing to assess respiratory impairment in occupational lung disease.

Exercise testing can answer several pertinent questions for the physician. It can determine whether a worker's aerobic performance is limited by respiratory or by other factors. It can also help decide whether an individual can perform a job without undue physiologic limitations and fatigue. Exercise testing has its limitations. It cannot determine the etiology of the impairment nor can it make a specific diagnosis except in rare cases. Interpretation of exercise data is not always precise, especially when the VO2max is normal but several physiologic measurements are abnormal. The VO2max achieved under laboratory conditions is probably too simplistic an estimate of the complex energy requirements of any occupation. Future research is needed to develop portable devices to assess both aerobic and anaerobic potentials of workers on the job to better determine job-specific impairment and disability. Patients who have unexplained symptoms or abnormal, but not severely reduced, static pulmonary function tests benefit most from exercise testing. For now, the AMA criteria for impairment as defined by static and exercise pulmonary function testing are the most appropriate to follow. Exercise testing has provided valuable data for epidemiologic research. Descriptive and case-control studies have documented minor physiologic abnormalities and rare respiratory limitations in workers with asbestos exposure and simple coal worker's pneumoconiosis. Additional studies are necessary to further elucidate pathophysiologic findings in patients with asbestosis and other occupationally induced pulmonary diseases.

Asbestosis↗
PubMedDate not supplied

A survey of exercise testing: methods, utilization, interpretation, and safety in the VAHCS.

BACKGROUND: Healthcare organizations are being graded in terms of their adherence to practice guidelines. The authors sought information on practice patterns of exercise testing within the Veterans Affairs Health Care System (VAHCS) to determine how well current practice patterns adhere to current guidelines. In addition, we sought to update past surveys to determine methods, indications, utilization of alternative diagnostic modalities, criteria for interpretation, safety, and physician supervision of exercise testing within the VAHCS. METHODS: Questionnaires were sent to 72 of the largest Veterans Affairs Medical Centers with cardiology divisions. The centers were queried regarding volume and type of exercise testing (standard, nuclear, and echocardiographic), indications, safety, protocols used, and criteria for interpretation. RESULTS: Seventy-one questionnaires were returned, comprising a total of 75,828 exercise tests performed within the last year. Virtually all indications for exercise testing fit the American Heart Association/American College of Cardiology (AHA/ACC) guidelines Class I criteria; 46% of patients were tested for the evaluation of chest pain; 14% were tested to evaluate patients at high risk for coronary artery disease; 10% were preoperative evaluations; and 8% were post-myocardial infarction evaluations. The most commonly used diagnostic test was the standard exercise electrocardiogram; a patient was five times more likely to undergo a standard exercise electrocardiogram or nuclear exercise test than an exercise or pharmacologic echocardiogram. The largest proportion of centers (49%) used 1.0-mm horizontal or downsloping ST depression as a criterion for an abnormal test, although 22% considered 1.5-mm upsloping ST depression to be abnormal, and 25% relied on a treadmill score. Seventy-eight percent of respondents used the treadmill, and of these, 82% used the Bruce or modified Bruce protocol. Four major cardiac events were reported (three myocardial infarctions, one sustained ventricular tachycardia) representing an event rate of 1.2/10,000. A physician was present during 73% of all standard exercise tests; 21% of respondents reported that a physician was required to be present "only for high-risk patients." CONCLUSION: Indications for exercise testing are in close agreement with the AHA/ACC guidelines; thus, the test continues to have an important role in diagnosis and prognosis among patients with or suspected of having coronary artery disease. The exercise test is an extremely safe procedure, with an event rate similar to other recent surveys. However, a great deal of variation exists in terms of criteria for abnormal results and whether physician presence is required during exercise testing.

Coronary Disease↗
PubMed2000

Blood lactate responses to submaximal field exercise tests in thoroughbred horses.

The associations between velocity during a standardized, submaximal 800-m exercise test and blood lactate concentration after exercise were investigated in Thoroughbred racehorses on sand and grass racetracks. Predicted lactate concentrations for each horse's exercise test velocity were calculated from the line of best fit derived from results at each racetrack. The repeatability of the differences between the measured and predicted blood lactate response to exercise was also investigated. Exercise tests were conducted at speeds ranging from 12.8 to 16.6 m/s. The variability of velocity within the exercise test was expressed as the coefficient of variation (CV) of the times for the four 200-m sections.On the sand track, the coefficient of determination for the lactate-speed relationship was highest for an exponential regression equation [lactate (mmol/L) = 0.08e(0.33x)(m/s);r(2)= 0.58, P< 0.05;n = 21]. Similar coefficients of determination were calculated for linear (r(2)= 0.56) and second order polynomial equations (r(2)= 0. 57). On the grass racetrack, the relationship was best described by a second order polynomial equation [lactate (mmol/L) = -0.87x(2)+ 28. 17x - 211.41;r(2)= 0.57, P< 0.05;n = 25]. The mean differences between the measured and predicted blood lactate concentrations in repeated tests were 1.9 +/- 1.8 (SD) and 1.8 +/- 1.7 ( SD) on the sand and grass racetracks. There were no significant associations between the velocity of the exercise and the CV on either racetrack. Differences between measured and predicted blood lactate concentrations, based on track-specific lines of best fit, have potential application in field studies of fitness in Thoroughbred horses.

Animals↗