CARDIO WORKOUTS, TO A LOT of bodybuilders, are like kissing your aunt Babushka from the old country—something you’d really like to avoid, but something you’re required to do. By and large, bodybuilders hate cardio. Old-school bodybuilders never did much of it because they didn’t like it or feel it was beneficial.
Some even believed it hurt their muscle-building efforts. Even today it’s safe to say if bodybuilders can achieve their desired look through training and diet, they’d nix cardio. But skipping cardio work during the contest preparation will make achieving your desired body-fat level nearly impossible unless you happen to be a freakishly lean ectomorph with an extremely fast metabolism.

The great debate in the bodybuilding world surrounding cardio is whether you should perform cardio at low intensity or high intensity. Even more heavily debated is when the two styles should be performed in conjunction with certain dieting strategies and strength-training workouts.
Let’s first consider some facts. Strength training is your number one way to spare muscle glycogen and burn body fat. Strength training in all its different forms has been proven through research to increase your body’s calorie burning potential, through a phenomenon known as excess post-exercise oxygen consumption (EPOC). Another term for EPOC is after-burn, which describes the calories expended beyond the resting metabolic rate after a bout of intense exercise.

The metabolic disturbance caused by all the chemical reactions happening as your body returns to its pre-exercise state—reactions such as lactate removal, increased blood circulation, higher body temperature, and
increased oxygen consumption—elevates metabolism and boosts calorie burn while sparing muscle mass. Depending on intensity of effort and your own metabolism, it generally takes between 15 minutes and 48 hours for the body to fully return to a resting metabolism. That’s great news for anyone who wants to drop body fat, especially the bodybuilder. But it still doesn’t mean that a bodybuilder in contest-prep mode can eliminate cardio training. Diet and weight lifting alone won’t do it all. For a bodybuilder to reach optimum body-fat levels of 6 to 3 percent, cardiovascular training must be performed.
But which type of cardio is best? Many bodybuilders assume that low-intensity cardio is the way to go because it’s aerobic and as such burns more body fat. High-intensity cardio is characterized as anaerobic because it taps fast-burning glucose stores for fuel. Studies comparing the two have shown that high-intensity cardio burns fewer overall calories but results in more fat lost and muscle spared.
As a person who has utilized both protocols during contest preparation, I’m not here to start a debate. What I can tell you through personal experience and coaching is that high-intensity cardiovascular work is superior and needs to be utilized by the dieting bodybuilder in order to speed up the body-fat-burning process.

A key component to high-intensity cardio is the way the body responds to this training style. Just as strength training does, high-intensity cardio increases your body’s insulin sensitivity and causes the release of more growth hormone, IGF-1, and testosterone but without the central nervous system fatigue associated with resistance training. So, your first choice should be high-intensity cardio work.
But there are benefits to be reaped from aerobic training, too, if you can fit that into your workout
schedule as well.
The best times to perform high-intensity cardiovascular work are on non-strength-training days.
Treat the session just as you would a strength-training session, that is, follow the same pre- and postworkout nutrition plan.

The Bodybuilder’s Beginning Cardio Workouts Prescription

Here again, your body type plays a critical role in your cardio plan of choice.
Frequency: 3 sessions per week
Length of session: 20 to 30 minutes
Do 1 to 2 sessions as high-intensity cardio
Frequency: 4 to 5 sessions per week
Length of session: 20 to 30 minutes
Do 2 to 3 sessions as high-intensity cardio
Frequency: 5 to 7 sessions per week
Length of session: 20 to 45 minutes
Do 2 to 3 sessions as high-intensity cardio

Ranking the Different Forms of Cardio Workouts

From highest to lowest calorie after-burn or EPOC:

#1: Metabolic Resistance Training (MRT)
What it is: MRT is an intense lifting style that combines aerobic and anaerobic training in an efficient workout that torches calories and will test your cardiovascular endurance. It can be done as circuits, supersets (using compound movements), but it is primarily characterized by very short rest periods.

What it does: An effectively designed strength-training program will create an increase in excess post-exercise oxygen consumption (EPOC) or metabolic disturbance following the workout. MRT promotes the body to maintain lean muscle mass while elevating the post-exercise metabolism.

When to use: If you only have 3 to 4 hours a week to train, perform as part of your strength-training program. Use with alternating sets, tri-sets, or quad-sets.
Specifics: Intensity is key—work can best be performed by following a form of periodization.
#2: High-Intensity Anaerobic Interval Training (HIIT)

What it is: Also known as HIIT, it involves alternating between short bursts of high-intensity effort and recovery segments at lower intensity. For example: In a HIIT running workout, after warming up, you might sprint at an intensity level of 8 out of 10 for 30 seconds followed by 30 seconds of recovery-level jogging (maybe a 4 or 5) and continue to alternate this way for the duration of your run.

What it does: HIIT much like MRT increases EPOC following a training session. HIIT will burn calories during and after the session. Studies show it promotes similar hormonal responses in the body as strength training.

When to use: Do this cardio workout on non-strength-training days if you have 4 to 6 hours to devote to your contest training per week.

Specifics: Be sure to follow up work periods with at equal or longer rest periods, that is, 15 seconds of work, 30 seconds of rest; 30 seconds of work, 30 seconds of rest; 30 seconds of work, 60 seconds of recovery.

#3: High-Intensity Aerobic Training

What it is: Steady state aerobic training, this is sustained at a fairly intense level for a moderate period of time. In other words, it is training at a non-fluctuating or constant speed at high-effort level.

What it does: High-intensity aerobic training will burn more calories than a low-intensity aerobic training session of equal time but won’t promote muscle mass or elevate your metabolism following the session.

When to use: If you can devote 6 hours per week in addition to strength training, perform this on nonstrength-
training days or after a lower-intensity strength session.

Specifics: Work periods will mostly be performed with intervals greater than 45 seconds and up to 5 minutes. For example—bike intervals of 2 minutes of intense work followed by 2 minutes of recovery.
#4: Low-Intensity Aerobic Training
What it is: Steady-state aerobic training, this is sustained at a low-intensity level for a longer period of time.

What it does: Low-intensity aerobic training will burn calories—possibly a good number of calories, depending on how long you perform a session—but it won’t help promote muscle mass or elevate your metabolism.

When to use: Only if you are one of those freaks who can devote about 8 hours of cardio training in addition to your strength training, perform this as part of your workout on strength-training and nonstrength-  training days.

Specifics: This is true aerobic training: running, walking, or riding a bike at a steady pace for 30
minutes to an hour. This puts you in what’s called “the fat burning zone” because your intensity is only
60 to 65 percent of your maximum effort.