Effects on Muscle Growth: HIIT v. Low-Intensity Cardio Training

Many athletes think that the combination of endurance and strength can negatively effect muscle growth. A common question I get from people is “If I add cardio to my strength training, will I decrease my muscle growth?”

A recent research study by Keith Baar (Department of Neurobiology, Physiology, and Behavior. University of California ) suggests that adding cardio to strength training tends to decrease muscle growth. In his research, he and his colleagues scientifically recommend the following training tips when performing high-intensity training [1]:

If performing a long high-intensity run session, do them in the AM. Following the workout, give your body at least 3 hours recovery time so that AMPK and SIRT1 activity can return to normal, healthy levels before strength training is performed. In simple terms, AMPK plays a big role in determining our body fat composition. It is found inside every cell in the body and serves as your body’s master metabolic regulating switch, influencing how our cells process energy. When AMPK is activated, cells don’t make or store fat, they only burn up stored fat. SIRT1 protein actively promotes the repairing on DNA brakes; It is an enzyme that when stressed can contribute to cellular regulation. After your strength training session, it becomes extremely important to consume protein right before you sleep to maximize the synthetic response overnight. [1]

For (30 min) low-intensity cardio training sessions, it is suggested to perform strength training immediately after. This training method will result in greater muscle growth without jeopardizing strength gains. [1]


In another study (University of Sydney), the effects of short HIIT cardio sessions combined with heavy strength training actually doesn’t decrease muscle growth significantly. To be more specific, running or sprinting tended to show no negative impact to muscle hypertrophy. In other words, data suggested that high-intensity cycling following a lower body strength training session negatively affected lower body hypertrophy however sprinting/running did not. [2]


Conclusion: After reading research reviews, most studies have found low-intensity cardio to negatively affect muscle growth when compared to HIIT training. [3]  The probable reason why high-intensity training is more optimal is because this form of training stresses the same energy systems as heavy strength training does. As a result, HIIT may interfere less with muscular adaptations. That being said, if you want to perform extra cardio on top of building muscle, high-intensity or HIIT may be your best bet when compared to low-moderate intensity cardio.





[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4213370/

[2] https://www.ncbi.nlm.nih.gov/pubmed/29658408

[3] https://www.ncbi.nlm.nih.gov/pubmed/22002517

[4] https://www.ncbi.nlm.nih.gov/pubmed/9927024

[5] https://biosignaling.biomedcentral.com/articles/10.1186/1478-811X-9-11

[6] Sirtuin 1


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1 thought on “Effects on Muscle Growth: HIIT v. Low-Intensity Cardio Training

  1. Good read for sure. I’ve been following Craig Capurso’s 30 Days Out program and he insists on doing cardio for 25 min so I usually walk at 3-4mph on incline. But the program that I was doing before, it insisted that I did a full hour of HIIT one day out of the week. So it’s very confusing to decide what’s good for your body, as everyone’s body is different and reacts different! Thanks for the research. -H

    Liked by 1 person

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