In intense full body exercise our hearts can supply only 1/3-1/2 of the muscles. To deal with this limitation, blood vessels in muscles and organs that are not too busy constrict while those in the working muscles dilate. This redistributes the blood flow, delivers more oxygen where it is needed most, and eases the work of the heart.

These so-called vascular reactions are so vital that Prof. Yuri Verkhoshansky listed them among the most important criteria of adaptation of the cardiovascular system and the entire organism to endurance exercises.

To put some numbers on it, in endurance sports during the competition period peak circulation in the working muscles has a massive correlation with performance, r=0.8—while VO₂max does not even make it to 0.4.

The vascular reactions can be improved—or messed up—with different types of training.

For example, a particular type of exercise reduces the peripheral resistance to blood flow by 23%—while amateurish interval training increases it.

When hard working muscles are not well supplied with blood, the contribution of the aerobic system decreases while the share of the lactic acid producing glycolysis increases. Whether your goal is to summit Denali or to lose a spare tire, you have got problems.

Next time learn how to optimize your vascular training for greater endurance and fat loss.