Simply put, 'Cardio' is cardiovascular exercise; in essence a type of exercise that increases your heart and respiration rate. You may also see this referred to as 'Aerobic exercise' which basically means 'to require oxygen'. The opposite of this is 'Anaerobic exercise'.
Cardio has a whole host of benefits. Crucially, it helps to keep the most important muscle in your body - your heart - healthy. It can also assist in maintaining healthy blood pressure levels. Other physical benefits include helping to increase stamina levels, assisting with the management of health conditions and to keep body-weight levels in check. The benefits aren't just physical though, there are few things that help to stave off stress and get the endorphin's flowing quite like a good workout.
Fundamentally there are two primary types of cardio:
1 - Low Intensity Steady State - LISS
2 - High Intensity Interval Training - HITT
So before we go any further, let's understand what these two cardio forms actually mean.
Low Intensity Steady State - LISS
As the name implies, with LISS cardio you aim for a low level of physical exertion for a long, continuous period. This elevates the heart rate by maintaining a specific level of intensity. The intensity and duration you choose will vary based on your fitness levels and your specific goals. Due to the lower level of intensity, your body recovers quickly and so does your metabolic rate; this means your body returns to its normal level of calorie expenditure soon after your workout.
Do not confuse 'Low Intensity' with 'No Intensity'. Too often people will hide behind the 'LISS' acronym as an excuse for doing sweet FA. Make sure you are still working, but at an intensity which is sustainable. Don't be afraid to experiment with different LISS types, and also to take it outside - A hike is a perfect example of LISS. Personally, my 'Go-To' LISS of choice is incline walking on a Treadmill at anywhere between 15-20 degree incline, and a speed of 5kph.
High Intensity Interval Training - HITT
No prizes for guessing - HITT is the EXACT opposite of LISS. It is a specialised form of interval training that involves short periods of maximum intensity exercise (intervals) broken up with slightly longer periods of moderate/low intensity exercise. Unlike LISS, HITT increases the amount of calories you continue to burn after your workout because it takes a longer time for your body to recover.
HITT can be far more varied than LISS training due to the number of factors involved. With LISS, the two main variables are time and intensity. Whilst these remain true for HITT, you are able to increase/decrease the number of overall working intervals you have, as well as increase/decrease the resting periods. My preferred weapon of choice for HITT is 10 intervals of 20 seconds on with 40 seconds resting on an assault bike. If you have never used an assault bike, then I strongly recommend that you try one. It will, quite literally, fuck your world up in a way you never thought possible.
Which leads nicely to my next point, do not kid yourself and allow 'High Intensity' to become 'Medium Intensity'. It is absolutely crucial that you are putting everything you have into those short working intervals as the full benefits of HITT come when you push past the threshold of your aerobic capacity. Do not massage your ego, and go hell for leather - Embrace the panting, the wheezing, the sweating, and accept the fact you're going to look like shit. Take comfort in the fact that every time you do this, you are improving who you are.
So...What Cardio is the BEST?!
The answer is...
...There isn't one!
Sorry Sports Fans, I know that's probably not the answer you wanted to read. As with so many things fitness related, there is no right or wrong answer. The best thing you can do is to experiment and find the balance that works best for YOU. Try combining both LISS and HITT to mix your training up and to prevent boredom from kicking in.
As with all things training, there are no shortcuts, and there is no 'secret ingredient'. I'm sorry to say that there is no 'Space Jam Water'. (If you haven't seen Space Jam and do not understand that reference, then shame on you. You should watch it immediately.)
The key is consistency - Find what works for you, and something that is sustainable. Do it. Do it again. Then again. And again...you get the picture.