Cardio: Low Intensity Or High Intensity?
By: Shane Giese
Like my other article, I was inspired to write about cardio for many reasons. First off, many people don’t understand the benefits of it and as a result, they don’t incorporate it into their training split. Finally, people don’t know how cardio will affect their body, and they also don’t understand that doing low intensity cardio is much different than doing high intensity cardio.
Here are the main benefits of cardio:
* Decreased resting heart rate.
* Decreased resting blood pressure.
* Increased muscular endurance.
* Improved circulation throughout your body.
* Decreased percentage of body fat.
* Decreased stress levels.
* More energy to complete your daily activities with vigor.
As you can see, cardio is very important for everyone. Cardio doesn’t have to be boring. It can be fun and exhilarating! Cardio shouldn’t be stereotyped to riding a stationery bike or running on a treadmill. Cardio is included in many activities such as basketball, swimming, biking, soccer, boxing, and America’s favorite sport, football!
Low intensity cardio is much different than high intensity cardio. In order to understand how these are different, I will first have to explain some things to you.
The breakdown of fats in your body is called lipolysis. The enzyme in the body that is responsible for lipolysis is called lipase. Lipase turns fats, or triglycerides, into three unbound fatty acids (FFA) and one glycerol molecule. So pretty much all you need to know by now is that lipase, the breakdown of fats, is caused partly by cardio.
Mobilization is the breakdown of triglycerides into glycerol and FFA’s for energy. So basically you can think of mobilization as breaking down fat in your body for future possible use. Oxidation is the point at which the fatty acids that were mobilized were actually burned. Fats that were mobilized for possible use do not have to be burned and can be converted back into new triglycerides.
Higher Intensity = Lower FFA’s
Studies have shown that as the intensity of exercise increases, the lower the amount of FFA’s (fats that have been mobilized) there are in your bloodstream. By now, most of you are thinking: Ok, since high intensity cardio create less mobilization than low intensity cardio, then low intensity burns more fat. This is not necessarily true. Although mobilization of fats goes down as intensity increases, the total oxidation of total fats is greater because more calories were burned, but at a lower rate of burned fat.
During low intensity cardio, the rate at which oxidation occurs in FFA’s in much higher than in high intensity cardio. By now you are probably going nuts thinking: Ok, in low intensity cardio there is more mobilization and a higher rate of oxidation than in high intensity cardio. So why is high intensity cardio better for burning fat? It is better for burning fat because although the amount of FFA’s being burned is lower, the amount of total fat is much greater.
So where is this other fat coming from? The other fat is called intramuscular triglycerides. Intramuscular triglycerides are droplets of triglycerides that are stored inside the muscle fiber. This places fat closer to the site of energy production in the muscle fiber and therefore allows intramuscular fat to be utilized at a slightly higher rate than adipose tissue (stored body fat).
Here is an example:
Say you burn 200 calories doing low intensity cardio and 90% of those calories came from fat. That means you burned 180 calories from fat and 20 from other sources. If you would have done high intensity cardio during that period, you might have burned 300 calories and 75% of those calories were burned from fat. That means you burned 225 calories from fat and 75 calories from other sources.
(keep in mind these figures are used for only a demonstration and do not
correctly represent the percentage of fat actually burned during cardio)
With high intensity cardio, you burn more fat and calories than low intensity cardio in the same period of time.
The summary of this article is that there isn’t a right answer as to whether low intensity is better than high intensity or that high intensity is better than low intensity. Both have their advantages. The advantage of doing high intensity cardio is that you burn much more calories than low intensity cardio and you burn more fat in the same period of time. The advantage of low intensity cardio is that more of the calories that you burn are coming from fat and not other sources.
So, which one is right for you? High intensity cardio is better for people who aren’t in a fasted state (ex: pre-contest) and don’t have to worry about every last once of muscle. It is good for people who don’t have hours a week to waste walking slowly on a treadmill. With high intensity cardio, you can burn more fat and calories in the same amount of time than low intensity.
Low intensity cardio is ideal for people who are in a fasted state. This allows them to burn off fat without having to worry too much about burning off muscle at the same time. Burning off 200 calories during low intensity cardio is more beneficial than burning off 200 calories during high intensity cardio if you are going for fat loss.