Houston, Texas (PressExposure) September 01, 2008 -- People often use the term cardio and ESD (Energy System Development) interchangeably. I don't pretend to be the one who came up with the term, but I prefer ESD because it's more descriptive. Case in point, when someone says cardio, it could be jumping rope, long, slow running for time, or sprint training. Trainees and trainers alike put it all into this category when it couldn't be further from the truth. The name itself implies long and slow. Two of the three exercises couldn't be further from the truth. Sprint training and jumping rope are shorter in duration and performed at a higher intensity. They primarily rely on a different energy source than long, slow distance running. ESD pertains the use of three different energy systems involved in training. This covers each one of the aforementioned above and the reason why I prefer to use this term.
Often I hear people talk about the need to do long slow distance work because they need to stress their aerobic system. While this is true, it also comes into play for sprint exercise. Remember, each energy system plays a part in every form of ESD work. Certain systems are stressed due to the modality, but each one is used to some degree in every form of ESD. What does this mean? Cardiovascular or aerobic benefits can be derived from sprint or higher intensity exercise. This is a great thing to keep in mind because of the negative benefits from aerobic training.
Have you ever seen a long distance runner's body? What about a sprinter's? Which one would you prefer to have? Probably the sprinter's, right? Generally, sprinters have lower body fat and bigger, stronger muscles than long distance athletes because he/she trains at a higher intensity. I'm sure you could say that genetic endowment plays a role. It would be naive of me to say that wasn't true. Regardless, just take a look at high school sprinters and cross country runners. Have you ever seen a muscle biopsy of a marathon runner at the conclusion of a race? Their muscles are absolutely destroyed! Long distance running is extremely catabolic (muscle degrading, "eating") causing this to occur. This is one reason why marathoners tend to be really skinny and/or gaunt and have higher levels of body fat. Muscle is energy costly and this mode of exercise tells the body to minimize it. This negatively affects metabolism and hinders calorie utilization.
This can be very contradictory for the fitness enthusiast/athlete. When losing fat, we want to maintain/increase muscle while losing fat. That way, the metabolism stays the same or increases, helping the effort. I would suggest focusing more ESD time on higher intensity exercise and less on the "muscle chewing" long slow distance stuff to get the body you want.
So, what conclusions have we come to today? Cardio and ESD are one of the same in some ways and very different in others. I don't know about you, but I'm going to continue using the term ESD. It just makes sense.