Why Cardio Matters in any Workout Plan

Cardio has been under a fair amount of criticism in recent years, especially from strength-oriented trainees.


After all, what use does someone have from cardio if their primary goals revolve around lifting enormous amounts of weight?


Sure, cardio seems optional - and even unnecessary - but its effects inside the body go far deeper than most people imagine.


With that in mind, let’s discuss why your workout plan could use cardio, regardless of your primary goals.


But First: Let’s Define Cardio


Cardio, also known as aerobic exercise, is any activity that elevates your heart rate and keeps it that way for an extended period (1). As its name suggests, aerobic exercise refers to the use of oxygen to produce the energy we need to do a specific activity. 


As a result, regular cardio improves the function of our cardiovascular system and our ability to produce energy with oxygen (2).


The Impact Cardio Has Inside The Body


Your body produces and breaks down countless adenosine triphosphate (ATP) molecules (3). These molecules provide energy for every cell in the body, allowing us to stay alive, do physical work, play sports, and do everything else we can think of (4).


Your body produces ATP molecules for energy in two ways (4):

  • Anaerobically - the quick and highly inefficient way that allows us to do short bursts of activity
  • Aerobically - the slower but much more efficient way that allows us to use up every glucose and fat molecule


Most people are under the impression that getting good at a specific activity is only about practicing it. But things are much more intertwined than we imagine. For example, research shows that even for something as intense as a 20-second sprint (an all-out effort), nearly one-third of the energy is produced aerobically (5).


Weight training is similar. While we don’t have direct data, we can look at the aerobic costs of sprinting and speculate a bit. Specifically, weight training is a form of all-out effort (especially with heavy weights), so it’s not a stretch to assume that roughly a third of the energy we need is produced aerobically. When lifting lighter weights for more repetitions, the aerobic system can easily produce more than half the energy we need.


The idea? A well-developed aerobic system can improve your work capacity, allow you to do more work, and reach fatigue more slowly.


The Practical Benefits Of Doing Regular Cardio


When done correctly and moderately, cardio can offer the following benefits:

  • Allowing you to do more repetitions with different percentages of your 1RM, especially when talking about sets of over ten repetitions.
  • Superior intra-workout recovery, allowing you to jump from set to set more quickly, maintain high training quality and finish quicker (6).
  • Superior recovery between workouts, allowing you to train more frequently and adapt positively (6).
  • Possibly pushing off anaerobic fatigue factors and further preventing acute fatigue, though this point is mostly speculative.
  • Not getting winded from longer sets and having to stop lifting a weight because your face has turned purple.

As far as incorporating cardio intelligently, we recommend doing your cardio on rest days from weight training. If that’s not possible, spread your cardio and weight training by at least six hours - for example, cardio in the morning and weights in the evening. If even that isn’t an option, do some cardio after lifting weights. This should minimize the interference effect (7, 8).