The components influencing your running performance include your cardiovascular and muscular systems, lactate threshold, aerobic capacity (VO2 Max), speed and economy of running. Goals of training should include increasing your body’s ability to transport blood and oxygen, increasing your muscles ability to use available oxygen, shifting your lactate threshold to correspond to a faster running speed and decreasing the energy demand of your running.
Your heart is a pump with output (Q) equaling stroke volume times your resting heart rate/minute. As your fitness level increases your stroke volume increases and your heart rate decreases. Your blood’s oxygen carrying capacity is a function of your hemoglobin concentration in your blood. It is measured in millimeters of oxygen carried per 100 ml of blood. One gram of hemoglobin transports 1.34 ml of oxygen. If your hemoglobin count is 15gm/100ml of blood then 15 times 1.34 equals 20 ml oxygen/100 ml of blood.
Blood flow is affected by the diameter of the vessel carrying the blood, the pressure difference between the heart and the destination of the blood, and the viscosity of the blood.
Your muscle cells and fibers reap the benefits of your cardiovascular labor. There is an actual increase in the number, size, and distribution of mitochondria, which are the powerhouse of your muscle. There is an increase in oxidative enzymatic activity which increases the rate oxygen is processed. There is also increase in oxygen flow to more parts of your muscle.
Your aerobic (VO2) capacity is your maximum oxygen uptake while exercising. Aerobic capacity can be increased by increasing your intensity, overloading your body slightly more than your body can handle. This will result in a greater VO2 capacity.
Accumulation of blood lactate in your muscles is a function of lactate acid production and the rate it is cleared by your muscles, liver, and heart. Lowering the blood lactate threshold that accumulates in the muscle while working increasingly close to VO2 max while running is a goal of all runners.
If you are going to use speed to win a race or set a PR with a long distance run you have to be able to “hang in” there until the point of kicking in the speed. The “hanging in” part requires high VO2, high lactate threshold, and good economy of running. We all have slow and fast twitch muscle fibers and they develop according to the specificity of the training.
Running economy is the consumption of oxygen relative to your weight and speed. The goal is to reduce your consumption of oxygen measured in ml of oxygen/kg/min while running at a set pace to become more economical as well to run faster without an increase in energy expenditure.