Cardio is the King of the Fitness Jungle. Rows and rows of cardio machines - ellipticals, treadmills, bikes, stair steppers, have a huge foot print in commerical gyms. Spin classes, Step Aerobics, BodyPump classes are usually full.
But Cardio's days as King are numbered.
"Cardio" is a generic, over-used, misunderstood word that has become firmly entrenched in the fitness vernacular and in the mind of the public as a "thing". "I'm going to do some cardio" or "I hate cardio" now carries its own meaning.
The term usually means exercise on a machine - elliptical, cycle, stair climber, treadmill - for 30 minutes or more, trying to achieve a certain heart rate and whose purpose is to burn fat. There's a misperception that this type of exercise somehow targets your cardiorespiratory system better than other types of exercise when the truth is that all exercise engages your cardiorespiratory system. The difference between exercising on an elliptical machine and lifting weights is in the type of energy you use to get the job done; not whether your heart and lungs work more or less in one exercise or the other.
There are three main energy systems: Adenosine Tri-Phosphate / Creatin Phosphate (ATP/CP), Glycolysis, and the Krebs Cycle. The first two are anaerobic and the last one is aerobic. The ATP/CP system can fuel about 15 seconds of high intensity work - like a sprint. The Glycolysis system fuels about 30-40 seconds of work and as you pass about one minute, the Aerobic system begins to take over. Now, these systems do not work in isolation of each other. Based on the intensity, you may need a burst of energy and you get this from the anaerobic system even though you might be performing a sustained exercise like cycling.
Why this matters is because of the effect that training has on the muscle, nervous and energy systems. Conventional "Cardio" uses mostly Slow Twitch Fiber (STF) and the Aerobic energy system. In addition, the nervous system is not taxed greatly with a repetitive motion like an elliptical machine or a bike. But, what you really need, especially as you age, is to train Fast Twitch Fiber (FTF) and the Anerobic energy system and to stress the nervous system (balance, agility, etc). To train FTF you have to perform some type of strength training at a moderate to high intensity (and intensity is highly variable by individual). It's the FTF that gives you strength, speed, reaction time etc. and as you spend more and more time on an elliptical machine or jogging or swimming thinking that this will keep you fit, what you're actually doing is teaching the FTF to work like STF. You may burn calories and lose weight but you will gain very little strength and strength is something you need for not just recreational sports or hobbies but for life.
Some people get concerned that if they don't do "cardio" that they are somehow not going to have a healthy heart and lungs. This is just not true. You can maintain your cardiorespiratory fitness by doing things such as lower intensity circiuit strength training where you use loads around 30-40% of your maximum, perform 15 to 20 repetitions per drill and move from one drill to the next with little to no rest. Or, you can use high intensity interval training as well. Cycle as hard as you can for 15 seconds then peddle easy for 45 seconds and do this for 20-30 minutes.
So, is there anything good about "Cardio"? Well, first let's call it what it really is - either Endurance Training or Distance Training. Of course, there is nothing wrong with Enurance Training / Distance Training as a vehicle to tax your heart and lungs. And, there are some other benfits as well:
- Increase in capillary density
- Improved nutrient delivery and metabolic waste removal
- Improved psychological well-being
- Improved insulin sensitivity
- Decreased blood pressure
- Improved glycemic control
- Reduced body fat
- Improved foundational level fitness
Just recognize that while you're Endurance or Distance training, you are not taxing other parts of your muscle and nervous and energy systems and that those systems need your attention too.
