Clinical use of submaximal treadmill exercise testing and assessments of cardiac biomarkers NT-proBNP and cTnI in dogs with presymptomatic mitral regurgitation

Evaluation of the Submaximal Treadmill-Based Fitness Test in Six Brachycephalic Breeds-A Follow-Up Study

Brachycephalic obstructive airway syndrome (BOAS) in dogs challenges veterinary surgeons both with a complex clinical picture as well as wide-ranging ways to diagnose the disease, often not easily implemented nor standardised in clinical practice. The assessment of a combination of exercise testing, the occurrence of breathing noises, recovery time, and respiratory effort proved to be an appropriate method to identify Pugs with BOAS. The purpose of this study was to apply an established standardised, submaximal, treadmill-based fitness test for Pugs to other brachycephalic dog breeds. A total of 79 participants, belonging to 6 different brachycephalic breeds, trotted 15 min with an individual comfort speed of 3-7 km/h on a treadmill. Additionally, functional BOAS grading based on respiratory clinical signs before and after exercise was applied. The test was passed if the dogs presented with a BOAS grade of 0 or 1 and their vital parameters recovered to baseline within 15 min after exercise. A total of 68% showed a BOAS grade of 0 or 1 and passed the fitness test. Of the failed participants, 65% failed due to BOAS affectedness, 9% were categorised as not affected by BOAS and failed due to not passing the fitness test only, and 26% showed both failure criteria. The fitness test can be a useful method to identify BOAS-affected dogs in other brachycephalic breeds and to diagnose BOAS in dogs that only show clinical signs under exercise.

The effect of the surgical treatment of brachycephalic obstructive airway syndrome on the thermoregulatory response to exercise in French bulldogs: a pilot study

Introduction

Due to altered anatomy of the upper respiratory tract, brachycephalic dogs exhibit increased airway resistance and reduced surface area for evaporative heat loss, predisposing them to respiratory and thermoregulatory problems, a syndrome referred to as Brachycephalic Obstructive Airway Syndrome (BOAS). Compared to non-brachycephalic dogs, brachycephalic breeds are more susceptible to heat-related injuries even at low ambient temperatures and relatively low physical activity levels. Surgical treatment alleviates clinical signs, potentially improving dogs' thermoregulatory ability with BOAS. Our study aimed to investigate the thermoregulatory response in French bulldogs before and after the surgical correction of BOAS, respectively.

Methods

Thirteen dogs were exposed to dynamic exercise on a treadmill and the dynamics of their rectal temperature (RT) and heart rate (HR) was measured. The experiment was performed in two independent sessions, before and after the surgical treatment. The test consisted of two consecutive 5-min walks at a speed of 2.5 km/h, first at an inclination of 0% and the second at an inclination of 5%, and a 30-min recovery period. Rectal temperature and HR were measured before the start of the test (t0), at the end of the first (t1) and the second part (t2), and 15 min (t3) and 30 min (t4) in the recovery.

Results

A significant increase in RT and HR was observed during exercise and recovery compared to the resting values, implying that the exercise intensity was sufficient to challenge the thermoregulatory response. The increase of RT was significantly lower during both parts (t1: p  = 0.004; t2: p  <  0.001) of exercise after the surgical treatment than before the treatment. Although a trend of lower RT after recovery was observed compared to before the surgery, it did not reach statistical significance. Similarly to RT, the HR was significantly lower during exercise after the first (p  =  0.020) and the second part (p  =  0.011) of exercise after the surgery compared to before the surgery but did not reach significance in the recovery.

Conclusion

Surgical treatment of BOAS can improve thermoregulation during exercise in French bulldogs with BOAS.

Investigation of the cardiac effects of exercise testing on apparently healthy Boxer dogs

BACKGROUND

Holter electrocardiographic monitoring is a cornerstone of diagnostic testing for arrhythmogenic cardiomyopathy (ACM) in Boxer dogs, but physical activity during monitoring is not controlled. In humans, exercise testing (ExT) can identify latent tachyarrhythmias associated with cardiomyopathy, and exercise increases serum cardiac troponin-I concentrations ([hs-cTnI]). These effects have not yet been investigated in Boxer dogs.

HYPOTHESIS/OBJECTIVES

Subjecting Boxer dogs to brief, moderate-intensity ExT can identify changes in Holter recordings and [hs-cTnI] compared to baseline results.

ANIMALS

Thirty overtly healthy, client-owned Boxer dogs.

METHODS

Prospective interventional study. Dogs underwent baseline diagnostic testing including 24-hour Holter monitoring and [hs-cTnI], followed by brief ExT (accompanied, brisk stair-climbing and -descending for <5 minutes).

RESULTS

Eleven dogs (37%) had >100 premature ventricular complexes (PVCs)/24 hours at baseline (3), ExT (3), or both (5). After ExT, these dogs had more PVCs/24 hours and greater increases in [hs-cTnI] compared to those with ≤100 PVCs/24 hours. Dogs with the striatin mutation had more PVCs/24 hours and a greater increase in [hs-cTnI] after ExT than did dogs without the striatin mutation.

CONCLUSIONS AND CLINICAL IMPORTANCE

Exercise testing may improve the binary classification of Boxer dogs with or without ACM by increasing the number of PVCs and [hs-cTnI] in affected dogs to a greater degree than in unaffected dogs. This effect also is associated with presence or absence of the striatin mutation. Exercise should be a controlled variable when screening Boxer dogs for ACM.

Evaluation of blood pressure and NT-proBNP in pugs with and without clinical signs of Brachycephalic Obstructive Airway Syndrome

Brachycephalic Obstructive Airway Syndrome (BOAS) is a pathologic condition of the upper airways, frequently occurring in dogs of brachycephalic breeds including pugs. It has been suspected that BOAS may be associated with cardiovascular changes and an increased risk for hypertension. The cardiac biomarker NT-proBNP can help to differentiate cardiac from non-cardiac respiratory distress. A possible influence of BOAS on NT-proBNP values has not been investigated, however. The aim of the current study was to examine blood pressure and NT-proBNP levels in pugs with and without clinical signs of BOAS and compare them to values of mesocephalic dogs. For this purpose, NT-proBNP values of 42 pugs and six mesocephalic dogs and blood pressure measurements of 34 pugs and four mesocephalic dogs were explored in the present study. Pugs were examined for clinical signs of BOAS at rest and after a submaximal fitness test, and a functional BOAS grading was applied. Blood pressure (BP) was measured at the beginning and end of the study day and NT-proBNP values were obtained before and after exercise. Measured values of pugs with different degrees of clinical impairment due to BOAS were compared among each other as well as to the CG. In terms of systolic, mean, diastolic BP, and NT-pro BNP, there were no relevant differences between pugs and the CG and no obvious connection between the severity of BOAS symptoms and measured values. BP values of all groups were lower at the second measurement at the end of the study day. NT-proBNP measurements were higher after exercise. BP and NT-proBNP values in all groups were in agreement with commonly used reference ranges. In conclusion, the study adds evidence, that BP and NT-proBNP values did not differ between mesocephalic dogs and pugs with different levels of severity of BOAS but between the measurement times. Thus, in the present study, excitement and exercise seemed to have a greater influence on BP and NT-proBNP values than presence of BOAS symptoms or breed. Discovered values show that the commonly used reference ranges for BP and NT-proBNP are applicable in pugs. This indicates that NT-proBNP can be used to differentiate between cardiac and non-cardiac respiratory distress even in pugs with clinical symptoms of BOAS.

Effects of Breed, Exercise, and a Two-Month Training Period on NT-proBNP-Levels in Athletic Dogs

N-terminal pro-b-type natriuretic peptide (NTproBNP) is a cardiac biomarker used to detect myocardial wall stress. Physical activity and cardiac disease can affect serum NTproBNP concentrations. In people, different types of physical activity have different effects on NTproBNP. Our hypothesis was that physical activity and training have an effect on NTproBNP concentrations depending on the type of exercise and the intensity. Seven German Shepherd dogs (GSD) under military training performing short bursts of fast-paced interval exercise and seven Eurohounds (EHs) training for racing competition with endurance exercise were included in the study. Blood samples were taken at enrollment (T₀) and after a two-month (T_2mth) training period; on both occasions, the samples were acquired before and after physical exercise. An echocardiographic evaluation was performed at T₀. Echocardiographic heart size was larger in the EHs compared to the GSDs. The NTproBNP concentration was higher in the EHs than in the GSDs before and after exercise at T₀ and T_2mth. Echocardiographic parameters of heart size and wall thickness correlated with NTproBNP at T₀ before and after exercise. Exercise induced an elevation of NTproBNP in the EHs at T₀ and T_2mth, while in the GSDs this was observed only at T₀. In the EHs, post exercise was associated with higher NTproBNP at T_2mth compared to T₀, while in the GSDs the opposite pattern was noticed. From our study, the serum NTproBNP concentration differs between breeds. Intense physical activity causes an increase in NTproBNP. A two-month training period does not affect the NTproBNP concentration at rest. Intense physical activity may increase NTproBNP above the reference range in individual dogs.

Use of proposed systolic and myocardial performance indices derived from simultaneous ECG and PCG recordings to assess cardiac function in healthy Beagles

Background and Aim:

Cardiac time intervals (CTIs) can provide important information on the electrical and mechanical properties of the heart. We hypothesized that cardiac function can be described using the combined power of electrocardiography (ECG) and phonocardiography (PCG) signals. This study aimed to (1) validate a novel custom device in measuring CTI parameters; (2) compare CTI parameters with a commercially available device and standard transthoracic echocardiography (STE); and (3) compare calculated systolic performance index (SPI) and myocardial performance index (MPI) with Tei index from the STE.

Materials and Methods:

This study determined CTIs based on simultaneous ECG and PCG recordings in 14 healthy Beagle dogs using the custom-built device. These CTI parameters were compared with a commercially available device (Eko DUO ECG + Digital Stethoscope; Eko DUO) and the STE. Agreement of CTI parameters between the custom device and the commercially available device or STE was evaluated. Calculated SPI and MPI based on Wigger’s diagram were proposed, compared with SPI and Tei index, and correlated with STE parameters.

Results:

We found that the ECG and PCG parameters measured from the custom-built device did not differ from the commercially available device and the STE. By combining ECG and PCG signals, we established CTI parameters in healthy dogs including indices for systolic function (SPI: QS1/S1S2) and global cardiac function {F1 ([QS1+S2]/S1S2), F2 ([RS1+S2]/S1S2), and F3 (RS1 + [QS2-QT]/S1S2)}. The SPI, F2, and F3 were comparable with echocardiographic parameters describing systolic (Pre-ejection period/left ventricular ejection time [LVET]) and Tei index ([MCOdur-LVET]/LVET), respectively. Only SPI and F3 were correlated significantly with MCOdur and heart rate, respectively.

Conclusion:

We have validated the use of the custom-built device to describe CTIs that are comparable to the commercially available device and STE in healthy Beagles. The proposed SPI and MPI derived from CTI parameters can be useful in clinical practice to describe the cardiac function, especially in areas where access to STE is constrained.

Evaluation of a Treadmill-Based Submaximal Fitness Test in Pugs, and Collecting Breed-Specific Information on Brachycephalic Obstructive Airway Syndrome

Simple Summary

In the present study, a submaximal fitness test on a treadmill was evaluated to assess its feasibility under standardised conditions. Moreover, its effectiveness in identifying pugs with clinical signs of brachycephalic obstructive airway syndrome was examined. It was apparent that respiratory symptoms can be exposed during the fitness test, and intensified with an increased duration of exercise. This method of testing improves the clinical evaluation of the dogs and helps identify restrictions due to brachycephalic obstructive airway syndrome. Since most of the dogs could be familiarised with the treadmill, it may be a feasible option for performing fitness tests in brachycephalic dogs. Major benefits, therefore, are that each dog can be closely monitored during the entire process, and that the examination can be conducted under standardised conditions.

Abstract

Despite efforts of veterinarians and breeders, brachycephalic obstructive airway syndrome (BOAS) is still a common problem in pugs, underlining the need for objective tests to identify and prevent breeding with affected dogs. In the current study, a submaximal, treadmill-based fitness test was evaluated as a tool to identify signs of airway obstruction not recognisable under rest conditions. In addition to this, different body conformation and measurements were assessed regarding their association with BOAS. A total of 62 pugs and 10 mesocephalic dogs trotted with an individual comfort speed on a treadmill for 15 min. Before and during the examination, dogs were examined for signs of respiratory distress, and a functional BOAS grading was applied. The influence of body conformation on BOAS grading was tested in a univariable and multivariable logistic regression model. During exercise, more respiratory noises were observed, and existing respiratory noises became more apparent in comparison to when at rest. In the multivariable logistic regression model, no factor had a statistically significant influence on BOAS classification. Submaximal fitness testing helped to identify signs of respiratory distress not apparent under resting conditions, and could be a valuable addition for identifying dogs with BOAS. Performing testing on a treadmill facilitates continuous observation of the patients, and enables standardisation of the test regarding the test environment, as well as provides an uninterrupted, steady workload.

A Formalized Method to Acclimate Dogs to Voluntary Treadmill Locomotion at Various Speeds and Inclines

Simple Summary

The land treadmill provides a range of behavioral and physical training benefits for dogs. Walking and trotting on the treadmill, however, is unfamiliar to many dogs and requires acclimation. This study developed and conducted a voluntary treadmill acclimation protocol on eight working dogs in training or working dogs performing detection research. The acclimation protocol was successfully completed for seven out of eight dogs. An acclimation assessment protocol was developed to measure a previously exposed dog’s degree of acclimation. This protocol was successfully used in two previously exposed dogs. A muscle soreness protocol was created to evaluate the soreness developed during the acclimation protocol. These protocols offer an option to acclimate dogs to the treadmill and determine the degree of acclimation for previously exposed dogs for research and training purposes.

Abstract

The land treadmill is a multipurpose tool with a unique set of behavioral and physical benefits for training and assessing active dogs. Habituation to voluntary treadmill locomotion is crucial for training a dog or accurately assessing a dog’s fitness on a treadmill. Therefore, a treadmill acclimation program was developed and evaluated with working dogs in training or working dogs performing detection research. Seven of eight naive dogs became acclimated to the treadmill using the protocol developed. Two previously experienced dogs successfully conducted an acclimation assessment to test for habituation to the treadmill. A muscle soreness protocol was created to evaluate the soreness developed during the acclimation program. This detailed protocol was successful in acclimating dogs to the treadmill at various safe speeds and inclines.

The effect of treatment with pimobendan in dogs with preclinical mitral valve disease - a placebo-controlled double-blinded crossover study

Background

Pimobendan is a widely used medication for the treatment of dogs with congestive heart failure (CHF) and preclinical degenerative mitral valve disease (DMVD) with cardiomegaly. The benefit of a treatment in dogs with preclinical DMVD but without cardiomegaly has not yet been elucidated. Some positive effects concerning life quality and a decrease in cardiac biomarkers could be verified. This study aimed to further investigate these results using a placebo-controlled double-blinded crossover design. Out of a total of 15 dogs, eight were allocated to sequence-group AB, in which dogs received pimobendan (A) during the first treatment period and placebo (B) during the second period. Accordingly, sequence-group BA was treated first with placebo followed by pimobendan. Each treatment period lasted six months and included a baseline investigation and follow-ups after 90 and 180 days. The investigations included a questionnaire completed by the owners, echocardiographic examination, and measurements of NT-proBNP, cTnI and lactate before and after a standardised submaximal exercise test.

Results

NT-proBNP values decreased significantly during the treatment period with pimobendan, and the post-exercise increase was attenuated at day 180. No significant treatment effects could be verified for cTnI and lactate, neither pre- nor post-exercise. Left ventricular size decreased under treatment, whereas no significant changes in left atrial size were detected. The owners described their dogs under treatment with pimobendan as being more active at day 90 (11/15) and day 180 (12/15). Those animals treated with placebo were described as being more active at day 90 (2/15) and day 180 (5/15).

Conclusions

Pimobendan had reducing effects on the concentrations of pre- and post-exercise cardiac biomarkers and the size of the left ventricle in dogs with DMVD ACVIM B1. Exercise testing in addition to an assessment of cardiac biomarkers might improve the decision when to initiate pimobendan treatment in dogs with DMVD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03014-5.

An individually adjusted endurance test reveals differences in physical fitness between young and old Beagles

OBJECTIVE

Aim was to establish an individually adapted endurance test for dogs on a treadmill, which takes the individual's physical condition into account. To check the applicability of the test, two age groups of clinically healthy beagles were examined.

METHODS

A total of 10 clinically healthy Beagles were enrolled and divided in a younger (1-3 years, n = 5) and older group (> 8 years, n = 5). The individual comfort gait speed of each dog was determined on a treadmill with integrated force plates. A maximal time of 20 minutes at trot was set for the endurance test. The test was terminated prematurely if the dog showed signs of fatigue (massive panting, unwillingness to move further). Blood samples were taken at general examination (G), prior to (B) and post exercise (P) for determination of lactate level (LL), oxygen and carbon dioxide partial pressure (pO2, pCO₂), bicarbonate (HCO₃ ^-), base excess (BE) and pH. On each occasion (G, B, P) heart rate (HR) and respiratory rate (RR) were recorded. Additionally, vertical ground reaction forces (Fz) were analysed.

RESULTS

The older dogs (age: 10.4 ± 0.89 years) completed the test with less speed and duration compared to the younger dogs (age: 2.4 ± 0.89 years), which managed to complete the maximum time. Lactate levels in the older dogs were higher than in the younger dogs at all timepoints of examination. Contrary to the younger dogs, there was no significant increase in the heart rate of the older dogs. Ground reaction forces were not significantly different between the groups.

CONCLUSION AND CLINICAL RELEVANCE

Whereas standardised endurance tests allow for the comparison of fitness levels between dogs, an individually adjusted endurance test aims at objectively determining the physical fitness of the single dog taking into account its individual performance. Such a test allows to examine the individual performance development over time and to evaluate medicinal therapies or dietary measures, e. g. in aging dogs. HR, RR, LL, blood gases (pCO₂, pO₂) and acid-base metabolism (HCO₃ ^-, BE, pH) were found to be appropriate parameters for determining the physical capacity of the dogs during endurance tests as these parameters change under physical stress and are indicative for the onset of fatigue.

Development of Novel Continuous and Interval Exercise Programs by Applying the FITT-VP Principle in Dogs

Although proper exercise training induces positive physiological effects, improper exercise can lead to injury, fatigue, and poor performance. The frequency, intensity, time/duration, type, volume, and progression (FITT-VP) are the essential components of exercise training to maintain or improve physical fitness and health. The purpose of this study was to develop specific exercise programs by applying the FITT-VP principle and to examine the effects on heart rate (HR) and hematological and biochemical parameters in dogs. The healthy male Beagles (n = 4) included in this study performed continuous and interval exercises, comprising 12 protocols. The HR monitoring elicited an affirmative response to activities but varied depending on the protocols. The hematologic parameters (e.g., red blood cell count, white blood cell count, hemoglobin, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration) were within the reference ranges both before and after exercise. The creatine kinase level significantly increased, and the cholesterol level decreased after exercises. In conclusion, the continuous and interval exercise program elicits an appropriate HR reaction, has no adverse effects on the serum parameters, and provides valuable insight for healthcare in dogs.

Effect of pimobendan on physical fitness, lactate and echocardiographic parameters in dogs with preclinical mitral valve disease without cardiomegaly

Pimobendan has gained enormous importance in the treatment of mitral valve disease in dogs. The current consensus statement of the American College of Veterinary Internal Medicine (ACVIM) recommends a treatment for dogs with symptomatic disease and dogs with asymptomatic disease with radiographic and echocardiographic signs of cardiomegaly. To investigate whether these dogs also benefit from a therapy with pimobendan, 21 dogs with mitral valve disease ACVIM B1 underwent a standardized submaximal exercise test on a treadmill. In this double-blinded and randomized study, the animals were divided into two groups, one receiving pimobendan and the other a placebo. At the first visit and at every follow-up appointment (at days 90 and 180), heart rate during the complete exercise test and lactate before and after running were measured. In addition to this, a questionnaire was completed by the dogs’ owners and all dogs were given an echocardiographic examination to detect any changes and to observe if the disease had progressed. Due to the diagnosis of leishmaniosis, one dog in the pimobendan group was retrospectively removed from the study so that 20 dogs were included for statistical analysis. No differences were observed at any time between the pimobendan-group and the placebo-group regarding heart rate. At day 180, the increase in lactate after exercise was significantly lower than in the placebo-group. The increase in the pimobendan-group at day 180 was lower than at day 90. Most of the dog owners from the pimobendan-group declared that their dogs were more active at day 90 (6/10) and at day 180 (8/10), while most dog owners from the placebo-group observed no changes regarding activity at day 90 (8/10) and day 180 (6/10). It can be concluded that the results of this study indicate that some dogs with mitral valve disease ACVIM B1 might benefit from a therapy with pimobendan.

Effect of Pimobendan on NT-proBNP and c troponin I before and after a submaximal exercise test in dogs with preclinical mitral valve disease without cardiomegaly - a randomised, double-blinded trial

Background

Exercise testing in conjunction with measurement of cardiac biomarkers NT-proBNP and cTnI is a useful tool for monitoring the effect of treatment on cardiac patients. Administering Pimobendan in dogs with degenerative mitral valve disease (DMVD) and cardiomegaly results in delaying the onset of clinical symptoms and prolonging life. Its effect in dogs with DMVD without cardiomegaly has not been well examined. The aim of the current study was to investigate the effect of administering Pimobendan in dogs with DMVD without cardiomegaly using exercise testing in conjunction with measuring cardiac biomarkers in addition to echocardiography.

Twenty-one dogs with asymptomatic DMVD without echocardiographic signs of cardiomegaly participated in a randomised, double-blinded trial. Dogs were divided into a Pimobendan-group (n = 11) and a placebo-group (n = 10) in a double-blinded study design and underwent a standardised submaximal exercise test (SSET). One dog in the Pimobendan-group was retrospectively removed from the study after being diagnosed with Leishmaniosis. Cardiac biomarkers NT-proBNP and cTnI were measured before and after exercise. Follow-up appointments were performed at days 90 and 180.

Results

Dogs in the Pimobendan-group had significantly lower post-exercise NT-proBNP-levels after being administered Pimobendan than at the beginning of the study. They also had lower pre- and post-exercise-NT-proBNP-levels than those dogs in the placebo-group. There was neither a significant difference regarding the measured cTnI levels nor an increase in cTnI between the groups at any time.

Conclusions

Pimobendan lowers NT-proBNP in dogs with presymptomatic mitral valve disease without cardiomegaly before and after submaximal exercise. This indicates a reduction in cardiac wall stress. If dogs with asymptomatic DMVD without cardiomegaly benefit from treatment with Pimobendan (for example, through a longer survival time) warrants further investigation.

The effect of telmisartan on the ventricular systolic function in dogs with experimental supraventricular tachyarrhythmia

Maintaining a good ventricular systolic function is important in the long-term therapy of dogs with supraventricular tachyarrhythmia (SVTA). The objective of this study was to evaluate the inhibitory effect of telmisartan on myocardial injury and the resulting ventricular systolic dysfunction in a canine model of SVTA. A total of 14 dogs were randomly assigned to a Telmisartan (oral telmisartan, 1.0 mg/kg daily, n=7) or a Control (no drug administration, n=7) group; the duration of rapid atrial pacing (RAP) was 3 weeks for both groups. The cardiac troponin I (cTnI) concentration in the Control group was significantly increased after 3 weeks compared to that before RAP initiation (baseline), but no significant difference was observed in the Telmisartan group. Moreover, the cTnI concentration at 3 weeks was significantly lower in the Telmisartan group than in the Control group. The left ventricular fractional shortening was significantly decreased at 3 weeks compared to that at baseline in both groups. However, fractional shortening at 3 weeks was significantly higher in the Telmisartan group than in the Control group. The cardiac output values in the Control group were significantly decreased at 3 weeks compared with those at baseline, but no significant difference was observed in the Telmisartan group. This study demonstrates that telmisartan inhibits the reduction in ventricular systolic function and prevents myocardial injury in a canine model of SVTA. Therefore, telmisartan is suggested as a novel treatment for canine SVTA.

A systematic comparison of exercise training protocols on animal models of cardiovascular capacity

Cardiovascular disease (CVD) is a major global cause of mortality, which has prompted numerous studies seeking to reduce the risk of heart failure and sudden cardiac death. While regular physical activity is known to improve CVD associated morbidity and mortality, the optimal duration, frequency, and intensity of exercise remains unclear. To address this uncertainty, various animal models have been used to study the cardioprotective effects of exercise and related molecular mechanism such as the mice training models significantly decrease size of myocardial infarct by affecting Kir6.1, VSMC sarc-K_ATP channels, and pulmonary eNOS. Although these findings cement the importance of animal models in studying exercise induced cardioprotection, the vast assortment of exercise protocols makes comparison across studies difficult. To address this issue, we review and break down the existent exercise models into categories based on exercise modality, intensity, frequency, and duration. The timing of sample collection is also compared and sorted into four distinct phases: pre-exercise (Phase I), mid-exercise (Phase II), exercise recovery (Phase III), and post-exercise (Phase IV). Finally, because the life-span of animals so are limited, small changes in animal exercise duration can corresponded to untenable amounts of human exercise. To address this limitation, we introduce the Life-Span Relative Exercise Time (RET_{life span}) as a method of accurately defining short-term, medium-term and long-term exercise relative to the animal's life expectancy. Systematic organization of existent protocols and this new system of defining exercise duration will allow for a more solid framework from which researchers can extrapolate animal model data to clinical application.