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Heart size/heart volume:

Heart size is measured by means of heart volume.

Besides an increased heart volume, stamina training can also cause thickening of the heart muscle.

Heart weight (absolute and relative):

Values collected by medical methods for approximate determination of heart muscle mass and described heart weight.

A heart weight from 500g onwards is called critical. A non-pathological growth of heart, caused by physical training (above all stamina sport), is called a sport heart. Such a sport heart produces the same performance for lower heart rate (compared to normal heart).

Resting heart rate

Resting heart rate describes heart rate in physical rest. It differs from human being to human being and can be reduced by stamina training.
Resting heart rate is an indicator of fitness level for athletes. The better exercised, the quicker drops heart rate after an exertion towards value of rest. The body recovers much quicker.
Women have a higher heart rate at rest and in exertion compared to men, because they differ regarding heart size. The smaller the heart, the higher is the heart rate at rest.

An increased resting heart rate can be an indicator for infection, over-training or a training intensity too high.
Maximum heart rate does not change by training or under exertion.

Stroke volume (SV):

The amount of blood released by a heart chamber into the body during systole (expulsive phase of heart).
Stroke volume depends upon size of heart and body position. In lying position, venous return is relieved. A better starting filling of heart chambers can be realized before expulsive phase.

Compared to heart rate, increase in stroke volume under physical exertion remains nearly constant. SV at rest and for physical exertion is enlarged for stamina athletes.

Cardiac output (= CO):

Amount of blood released by a heart per minute.
The cardiac output is heart rate (per min) multiplied by stroke volume (CO = HR x SV). CO increases with increasing heart rate

Maximum oxygen capacity (VO₂max):

Oxygen capacity describes the amount of oxygen the organism consumes or transforms within the scope of energy supply in tissues within a minute.

The maximum relative value indicates how many millilitres of oxygen the body can use per minute (for maximum workout). Indication in millilitre per minute (ml O₂/ min/kg).

VO₂max can be used as criterion for evaluating aerobic stamina fitness. Cardiac output decreases with advancing age (standard values above are of twenty to thirty-year-old) and values for women are often 10 to 15 % below those of men.