Cardiovascular fitness is the ability of your heart, lungs and organs to consume, transport and use oxygen. The maximum amount of oxygen your body can consume and use is your VO2 Max. When you do cardiovascular exercise regularly, you can improve your cardiovascular fitness as your heart becomes more efficient at pumping blood and oxygen to the body, and the body becomes more efficient at using that oxygen.
In the simplest of terms the act of elevating your system above what it is used to through fitness training will increase your cardiovascular fitness. The more stress you put on this system the more it will be forced to adapt.
Lungs physiological adaptations to exercise
1. Ventilation / Breathing rate
Breathing increase with high intensity training (this is more an adaptation from anaerobic fitness and muscular endurance training or higher intensity aerobic fitness training). This enables much more air to move in and out of the lungs, therefore enhancing gas exchange.
2. Lung Capacity/ Volume
Lungs increase their ability to expand enabling a larger quantity of air to move in and out (this is a similar adaptation to the increase in stroke volume in our cardiovascular system).
3. Respiratory Muscles
The strength and endurance of the diaphragm and intercostal muscles increases. This results in an improved ability to breathe in more air, for longer with less fatigue.
Aerobic training improves the endurance of respiratory muscles
Anaerobic training increases the size and strength of respiratory muscles
3. Capillarisation in the lungs
More capillaries are made in the lungs over time allowing more blood to flow in and out of the lungs. This increases the uptake of oxygen as there is a greater surface area for blood to bind with haemoglobin.
The numbers of alveoli in the lungs increase to enable more gas exchange to occur.
5. Gas Exchange
The exchange of oxygen and carbon dioxide improves as the gradient between each becomes bigger. This is because the more oxygen used in the tissues and the more carbon dioxide produced creates a larger difference between the blood and tissues.
Aerobic fitness training tends to improve the efficiency of the body’s tissues at absorbing O2 and removing CO2, while anaerobic fitness and muscular endurance training tends to increase the capacity for this gas exchange.
Other training modes such as hypertrophy training will also result in some minor adaptation occurring in the respiratory system.
For example you will notice your breathing rate increase after each set during hypertrophy training where the work period is 30 seconds or more and rest period is similar. Over time this may result in some respiratory adaptations, however the degree of adaptation with this type of training far less significant.
The Hearts physiological adaptations to exercise
1. Heart Size
The walls of the heart get thicker, particularly, the left ventricle, providing a much more powerful contraction.
The left ventricles internal dimensions enlarge as a result of increased ventricular filling.
2. Stroke Volume
This size increase of the heart enables the left ventricle to stretch more and therefore fill with more blood. The increase in muscle wall thickness also increases the contractility resulting in increased stroke volume (amount of blood pumped per stroke) at rest and during exercise, increasing blood supply to the body.
3. Resting Heart Rate
As cardiac output at rest remains constant the increase in stroke volume (amount of blood pumped per stroke) is accompanied by a corresponding decrease in heart rate.
4. Cardiac Output
Cardiac output increases significantly during intense exercise effort due to the increase in stroke volume. This results in greater oxygen supply, waste removal and therefore improved endurance performance.
5. Blood Pressure
People with normal blood pressure experience little change at rest or with exercise; however hypertensive people find that their blood pressure reduce towards normal as they do more cardiovascular fitness training. This is due to a reduction in total peripheral resistance within the artery, and improved condition and elasticity of the smooth muscle in the blood vessel walls.
Other training types such as hypertrophy (muscle building) training can also result in these adaptations occurring in the cardiovascular system however the degree of adaptation will be less significant than the adaptation caused by aerobic fitness, anaerobic fitness and muscular endurance training.
Cardiovascular fitness training need not be boring, it does not have to be an hour on the treadmill it can be a well structured mix of functional strength training and speed work, as long as you are moving constantly and are out of breath the whole time you are in the right zone.
Here is an example of a nice mixed session that hits all variables.
Kettlebell swings double handed 2 minutes
Pushup burpees 40 reps
2000 meter row
Jumping jacks 2 minutes
Do this for 2-3 rounds should last about 40 minutes, a perfect way to keep your mind occupied rather than on a boring treadmill