In this case, endurance is mainly an effect of heart hypertrophy.
The effect of myocardial enlargement or “athlete’s heart” is the pumping of a large amount of nutritive blood to the arteries.
Aerobic endurance depends on the heart tone,
which determines a higher blood pressure,
by allowing the supply capillaries to open at the
level of active muscles.
This intense capillarization is the result of a long training process based mainly,
in our view,
on the way rest breaks are used between repetitions.