Exercise for Cardiovascular Disease Prevention and Treatment From Molecular to Clinical, Part 1

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or chronic cardiovascular adaptive responses. Ultimately the research goal is either

to uncover the cardiovascular physiological mechanism of exercise or to uncover

how exercise affects cardiovascular health and disease. The latter sections will

briefly describe the most common kinds of animal models of acute and chronic

cardiovascular exercises that are currently being tested and are likely to be employed

in the near future.

2 Criteria for Choosing Animal Cardiac Exercise Modalities

Different criteria may be applied for each exercise modality during the training or

conditioning period. These criteria should be reliable and practical without impact-

ing the study’s primary aims. On the other hand, performance design and imple-

mentation standards are keys to success [ 5 , 7 , 15 , 24 ]. In order to optimize exercise

protocol, animal experiments designed for assessing the impact of exercise on

health and physiology should perfectly address at least several concerns [ 3 ].

First, the experimental protocol should exert minimal amount of exercise to pro-

duce the expected outcomes (e.g. intensity, duration, frequency) [ 3 ]. In reality, many

studies have shown that the intensity (low, high), timing (morning, evening), and

duration (continuous, discontinuous) of the exercises are the determinants of the

physiological responses and outcomes [ 8 , 11 , 12 , 25 – 27 ]. Before initiating any

exercise study, animals should be familiarized with the given exercise modalities

with a period of adaptation and habituation [ 3 ]. This conditioning process is essen-

tial to minimize exercise-induced stress responses and injuries. Importantly,

researchers must ensure that humane procedures are devoted in either acute or

chronic exercise protocols.

Second, exercise study should carefully chose the animal type, which will be

selected according to maximal advantages and minimal disadvantages [ 3 ]. More

care should be also provided in the disease- or disorder-conditioned animals because

they are likely unwilling to perform any exercise at all [ 3 , 7 ].

Third, investigators should also pay attention in selecting exercise type which

will best produce the requisite physiological changes with minimal negative conse-

quences brought by stress. For example, while the efficiency and endurance capac-

ity of the heart become more efficient in aerobic exercise, muscle strength and

endurance also increase with resistance exercise [ 11 , 28 ]. Chosen species is also the

primary determinant in selecting cardiovascular exercise modalities [ 1 , 6 , 7 ]. These

animal exercise modalities, particularly aerobic exercises, include swimming, tread-

mill running, and voluntary wheel running [ 10 , 17 , 20 – 23 , 29 , 30 ].

Fourth, the experimental protocols should be designed to maximize perceived

physiological adaptations and to minimize the negative consequences [ 3 ]. Protocols

should be developed to test the anticipated physiological adaptations to ensure high-

quality research and ensure the safety of the research animals (e.g., following the

Guide for the Care and Use of Laboratory Animals and ethical guidance concerning

about animal welfare) [ 31 ].

4 Acute and Chronic Exercise in Animal Models