One of my favorite resources when it comes to the science of training and nutrition is Core Performance. They do a really good job of explaining the science behind why we do what we do as athletes, training professionals, and regular gym-goers.

For a while, I’ve been on this rant about high-intensity training versus steady-state cardio. You will NEVER find me running outdoors (unless it’s for my dog, of course), or just steady-state anything on any equipment. The most effective training is interval training. We obviously want to make the most out of everything we do (well, at least I do), so why not capitalize on the time while you’re training and work on building your lactate threshold… lactate whhaaat?!?!
Below, Core Performance lists the different energy systems that are important for us to build:
1.Lactate threshold – This is your capacity to do high-intensity work for up to 3 minutes. The ESD unit of your training program is a form of interval training in which you will alternate between periods of intense exercise with less strenuous periods.
2.Lactate power – This is your body’s ability to do high-level work for periods of up to 12 seconds.
3.Aerobic system – The ability to work beyond 3 minutes and help you recover from your bouts with the lactate threshold. For instance, if you’re sprinting up hills and walking down, you’re using the lactate system on the way up and the aerobic system on the way down. In this case, the aerobic system enhances your recovery from these intense bursts of energy.
These are dependent on the types of activities you do and to what capacity they can elevate your heart rate, because it all boils down to science, right guys?! Calorie burned > Calorie intake — and the most effective way to increase your calorie burn is increasing your heart rate! DUH!

So here are some activities (excerpt from Core Performance site) that correspond with the different energy systems mentioned above:
Level 1
Level 1 focuses on steady-state aerobic work. Aerobic simply means that your body will use oxygen to provide a steady and consistent, low level of energy for a long time, without building up any waste products in the body that hinder performance. A good rule of thumb for level 1 is that you should be able to carry on a conversation when you are in the aerobic zone. Some of the best activities for level 1 are:
■ Outdoors: Brisk walking, walking up hills, biking, swimming, rowing
■ Indoors: Biking, treadmill climbing/walking, elliptical trainer, Airdyne
Level 2
Level 2 will introduce interval training by mixing moderate intensity (heart rate zone # 1) with bouts of Level 1 easy-intensity aerobic work to allow you to catch your breath and recover from the slightly more intense intervals. You’ll know you’ve reached Level 2 moderate intensity if you would find it difficult to carry on a conversation. You could, but you wouldn’t be able to say much more than a couple of words at a time. Some of the best activities for Level 2 are:
■ Outdoors: Running-to-jogging/walking, jogging-to-walking
■ Indoors: Bike, elliptical trainer. treadmill, stair climbers, Airdyne
Level 3
In Level 3 you will work harder, performing intervals that include time spent in heart rate zone # 2. The times and rest intervals both decrease. Don’t be intimidated by more intense work; you’ll be ready for it. In fact, you will be looking for a greater challenge. Some of the best activities for Level 3 are:
■ Outdoors: Running-to-jogging/walking, jogging-to-walking
■ Indoors: Bike, elliptical trainer. treadmill, stair climbers, Airdyne
Level 4
Level 4 is the shortest of the intervals, increasing your heart rate to the highest zone (zone # 3). It requires mobility, stability and strength. At this level you will ride, run, or climb as hard as possible for between 10 and 30 seconds. In order to get the most out of Level 4, you’ll need to pack as much power and energy into these segments as possible.
Some of the best activities for Level 4 are:
■ Sprinting (flat or uphill)
■ Shuttle runs (5 yards and back, 10 yards and back, 15 yards and back)
■ Bicycle intervals (or take my spin class, hahaha)
The rest of this article can be found here.
So cardio it up, my friends, but cardio wisely!!!
