Cardio… Who does it, who doesn’t? Honestly who really understands it?
Cardio spans the rainbow from an easy walk that elevates your heart rate to a full on sprint for 0:00:30… The interesting part is what is occurring physiologically. Aerobic fitness, cardio, has a few gears. First is activity up to and below Aerobic Threshold AeT. Any aerobic activity below or at AeT is primarily fueled by fat. The keto diet is derived from this science. Low carbs force the body to burn fat. Well how bout this…You can burn fat as a primary fuel source if you stay below or at your AeT.
The AeT is the point where we, as homo sapien sapiens, switch from fat metabolism to glucose or sugar metabolism. Once we start to burn sugar the clock is ticking in terms of lasting power. Sugar or glucose metabolism creates by-products, i.e. lactate. Lactate = end game.
Why does this matter?
When you do cardio, is it at Aerobic Threshold, Anaerobic Threshold, or in between… Do you even know the difference? Chances are you have no clue. Most athletes do not.
When we talk about Cardio there are so many facets to it calling it Cardio is idiotic. It would be akin to saying “Oh…you lifted weights today…” Well did you train Max Strength, Muscular Endurance, Base Strength, Functional Strength, etc… See the problem?
Do you do Cardio? Well, do you mean sprints, intervals, aerobic base, etc…? The heart rate you are at determines your “cardio” . If I do 10x10 @ 35# bench but my 1 RM is 395#'s what am I actually working on? If I do 5x2 @ 90% 1 RM Dead Lift what am I working?
Cardio is the same… Are you trying to burn fat, improve aerobic capacity, increase sprint power, lose weight…etc. CARDIO is the lamest term in fitness. Similar to “Do core work”. WTF does that mean… Sit-ups? Or do you mean addressing the multiple muscular components in the abdominal region; transverse abdominal, rectus abdominal, obliques, etc…
Its not so easy. Cardio is diverse and needs to be conducted with end goals in mind. I will happily write an academic article with references for those who want more info.