Cardio Induces Skeletal Muscle Hypertrophy

Published in final edited form as:
Exerc Sport Sci Rev. 2014 April ; 42(2): 53–61.  

*Aerobic Exercise Induces Skeletal Muscle Hypertrophy 

*Extract from part 1 of my blog

"We were born for VO2 Max Training" 

How many times have you heard "cardio will make you lose muscle mass?" Before I introduce the science, my submission is that "bodybuilders" who started this unfounded hypothesis mentally associate cardio with the "cutting stage" of their training before a show. These guys "bulk" most of the year with the intake of tons of carbs, sugars and calories, which makes them feel big, strong and happy. The drugs and stimulants they take help offset some of the insulin spikes thus assisting artificially with protein synthesise and fat utilisation. 


Bodybuilder types introduce cardio during the "self diminishing" stage of their training cycle. It's their mental perception, not science fact that makes them believe cardio is the reason for their vanishing mass.

Then when these "bodybuilder types" need to lose the fat and condition up, they reluctantly turn to cardio training. Note they are on a "self diminishing" cycle as they remove "junk food, sugar, mass calorie intake, zero cardio and reduce drug dosages" How do you think they mentally begin to feel? Depressed, anxious and self conscious.

They mentally attach "cardio with loss of mass, and feeling low" This is NOT from the cardio training effect but the way they chose to introduce the protocol. Its their metal perception, not science fact that turns them off cardio.

Skeletal Muscle Hypertrophy after Aerobic Exercise Training.

Mayo Clinic Exerc Sport Sci 2014 April

Now lets look at both common sense and science here. Firstly are you telling me that our perfect "cellular" system has a flaw? I mean how would we have evolved if the human body would scarfice and cannibalise its own flesh each time we would need to go and "hunt" for long periods of time walking/jogging miles on end in the search for food? Remember for an effective kill we would then need all the mass / strength and high aerobic fitness levels we could gather. Surely aerobic activity signals hunt or being hunted & therefore the opening of adaptive pathways one being hypertrophy? .... 

I am known for my intense cardio/Vo2 Max and HIIT training. At 40 years of age few can keep my pace, and even though I am now at the stage of life that I have entered my "ageing" timeline making it more difficult to retain and gain lean muscle mass, I hold plenty. I typically do 10-14 hours a week of "Cardio" based training. I can gain mass when needed with ease. I have never had a client "lose mass" whilst under my watch and incorporating efficient cardio training...  

Aerobic exercise training (AET) has an effect on many mechanisms that may collectively promote skeletal muscle hypertrophy. 

Aerobic exercise training (AET) has an effect on many mechanisms that may collectively promote skeletal muscle hypertrophy. 

It would seem science backs my theory that "efficient" cardio training does not only NOT hinder muscle hypertrophy it assists it! 

Numerous papers cite how aerobic exercise training alters key intracellular signaling pathways and mRNA expression related to both skeletal muscle protein metabolism (FOXO3a) and mitochondrial dynamics and proliferation leading to greater skeletal muscle hypertrophy. 

The findings in "Skeletal Muscle Hypertrophy after Aerobic Exercise Training Adam R. Konopka1 and Matthew P Mayo Clinic College of Medicine 2014" support my opinion that cardio training   will "not reduce muscle mass" but actually assist growth; 


"We propose properly performed aerobic exercise leads to skeletal muscle hypertrophy that is comparable to resistance exercise training"

This paper accurately remarks "as with any exercise-training program in humans, adaptations are highly variable which could be why some studies have not observed increased muscle size". Further still, Nearly all studies examining muscle mass since 2005 (8 of 9) have reported skeletal muscle hypertrophy in the muscle group(s) most utilized during exercise. 


Aerobic exercise training (AET) has an effect on many mechanisms that may collectively promote skeletal muscle hypertrophy. 

It's worth noting that over 95% of the people I come across/see/post on social media are approaching cardio training completely incorrectly. Most are blinding following systems that are outdated and have no proven protocol effectiveness. Again as the paper above highlights this is perhaps why you guys are not observing what I am! The paper cites

"The effectiveness of aerobic exercise training to induce skeletal muscle hypertrophy most likely depends on obtaining sufficient exercise intensity (70-80% HRR), duration (30-45 minutes) and frequency (4-5 days per week) to achieve a large number of muscle contractions that places a high-volume, low-load on skeletal muscle compared to traditional hypertrophic resistance exercise programs" ... It further comments

"Collectively, research revolving around protein metabolism suggests aerobic exercise acutely and chronically stimulates skeletal muscle protein synthesis, creating a myocellular milieu that coincides with increased myofiber and whole muscle size after training"

The paper then goes on to conclude

"Collectively these data warrant that aerobic exercise training should be acknowledged to increase skeletal muscle mass and be considered an effective countermeasure for muscle loss with advancing age."

Still think cardio will induce muscle wastage?