142
2.3 Myocardial Infarction Induced by Isoproterenol
The induction of MI is performed through subcutaneous administration of isopro-
terenol at a dose of 150 mg/kg/day diluted in 2 ml of saline on two consecutive days
with an interval of 24 h between applications. The false induction of MI in the sham
group is performed by subcutaneous administration of 2 ml of saline on two con-
secutive days, also with an interval of 24 hours between applications [ 23 ].
3 Physical Activity and Exercise Training in the Context
of MI: General Concepts
Before beginning data presentation about the protective or regenerative effects of
physical activity (PA) and/or ET on MI, it is necessary to clarify the main concepts
and recommendations involving both kinds of body movement. In fact, although
similar, PA and ET have different concepts and, generally, cause distinct body adap-
tations. Moreover, these tools are applied in different contexts, depending on the
purpose chosen by the healthcare team (e.g., physical educator, physiotherapists,
nurse, physician) after evaluation and patient agreement.
The American College of Sports Medicine (ACSM) has defined PA as any bodymovement performed in response to voluntary muscle contraction that increases
energy expenditure [ 24 ]. Thus, it is important to understand that blinks or shivering are
not considered PA, even if they are types of body movement. On the other hand, walk
for some minutes in the park talking with a friend is a PA, once the contraction of leg
muscles is voluntary and the energy expenditure increases exponentially from baseline
levels. In turn, ET refers to a more elaborated concept, which concerns a planned and
structured body movement aimed to improve one or more physical capacities. ET has
different designs, and can be introduced as, for example, aerobic and strength/resis-
tance exercise, swimming training, yoga, among others, depending on the approach.
The American Heart Association (AHA) describes PA as an important tool to beused in the prevention of a variety of pathologies, as hypertension, diabetes mellitus
type II, obesity, as physical inactivity is strongly associated with cardiovascular
disease risk factors, morbidity and mortality [ 25 , 26 ]. Moreover, AHA strongly
encourages the inclusion of PA in the lifestyle changes of patients who aim to
decrease cardiovascular disease risk factors [ 25 , 26 ]. General recommendations
indicate that adults should achieve, at least, 150 minutes of moderate-intensity
activity or 75 min of vigorous-intensity activity per week to prevent cardiovascular
disease [ 25 , 26 ].
In the context of cardiac rehabilitation and secondary prevention, ET is generallythe used approach. Surprisingly, epidemiological data about its preventive effects
are not elucidated, since prescription of ET are dependent on some factors, as exer-
cise volume, intensity, cadence, which are difficult to control in observational stud-
ies (i.e., follow-up). However, the effects of ET on cardiovascular disease risk
I.C. Moraes-Silva et al.