The cardiovascular system is the power plant of energy production. It pumps the blood throughout the many miles of blood vessels that make up the vascular network and delivering oxygenated blood to the working muscles, while transporting deoxygenated blood back to the lungs. As well as blood it also transports: vital nutrients, hormones, metabolites, gases, waste etc… throughout the body. So how well the cardiovascular system performs plays a massive role in performance and general health.
Lately LISS has gotten a bad name and most people shun it for higher intensity intervals. But this is a mistake as it develops the heart and vascular network in a way that higher intensity training cant.
You can increase how much blood your heart can pump in different ways and methods. Longer slower training works to increase stroke volume (the volume of blood pumped out with each beat) primarily by increasing the size of the left ventricle of the heart. Think of a balloon being constantly inflated, overtime it will stretch and become bigger. The same thing happens with the heart when you fill its chambers with a large volume of blood and force it work for an extended period of time.
Through training the heart adapts to this stimulus and you end up with a larger left ventricle which is capable of pumping out more blood with each beat. This is known as eccentric cardiac hypertrophy. The result is a lower resting heart rate, a lower working heart rate, and greater cardiac efficiency. The less work your heart has to do to pump blood; the better your aerobic energy production will be because more oxygen can get to your muscles.
High intensity training leads to a different kind of cardiac adaptation known as concentric hypertrophy. Training that raises blood pressure such as strength training, lead to a different adaptation. Rather than stretching, the heart walls increase in size and become thicker. When you do high intensity exercise, and your heart rate goes above a certain threshold, typically 150bpm or so, the contractions become too fast for there to be enough time for the chambers of the heart to fill with blood (so the heart doesn't stretch). Lower intensity methods also stimulate your vascular network to develop as well and thus increase oxygen transport to the working muscles.
Guidelines for LISS:
- Heart rate should be 120-150
- Each session should last 30-60 mins
- Any low intensity, low pressure exercise: jogging, cycling, swimming, skipping etc…. will work as long as heart rate is kept in correct range. I like to mix it between rounds of skipping and shadow boxing
(Research from the book "Ultimate MMA Conditioning" by Joel Jamieson)