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

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Some 35 years later, using a specific scoring technique, Nie and colleagues [ 12 ]

compared the “injury score” of mitochondria from left ventricles of two groups of

control and trained rats in a tentative to highlight some difference but without suc-

cess, demonstrating that training in healthy animals is not deleterious.

1.1.3 Cardiomyocytes Hypertrophy: Resulting Effects of Exercise

on Length, Width and Depth

With the increased use of the enzymatic dissociation technique and the extensive

implementation of confocal microscopy it became easier to address the length,

width, depth and the resulting volume of isolated cardiomyocytes.

Cell length was generally found to be increased, ranging from 5% to 20%: 5%

[ 4 , 13 ], 6% [ 5 , 6 ], 10% [ 14 ], 13% [ 10 ], 20% [ 7 ]. It should be noted this length

increase is reversible. In the latter paper, authors reported a detraining in 2 weeks,

in a timing similar to the left ventricle weight which returned to 2% (over 14%

increase) in 2–4 weeks of detraining.

With regards to regional differences it could be noted that cardiomyocytes origi-

nated from sub-endocardium wall left ventricle displayed a greater effect of training

than the one from sub-epicardium wall: a 20% cellular hypertrophy (measured as

cell volume) was seen in endocardium cardiomyocytes while the size increase was

no significant in epicardium cardiomyocytes [ 1 ]. Similar results were obtained [ 8 ]

in experiments where the depth was also measured or calculated.

Fig. 5.1 Graphical abstract of training effects on healthy cardiomyocytes. AP action potential, MP
membrane potential, SR sarcoplasmic reticulum, T-Tubules transverse tubules

A. Krzesiak et al.