The relationship between cardio and muscle growth is much more complex than people make it out to be. Aerobic exercise provides many beneficial effects on the cardiovascular system that cannot be achieved through resistance exercise; however, there are appropriate times to perform cardio that will not interfere with muscle gains.


  •  The best time to do cardio when muscle building appears to be on days when not performing resistance exercise.
  • Training with cardio and resistance exercise in excess can cause blunted muscle growth.
  • The greater frequency, intensity, and duration of cardio, the greater its impact on reducing muscle growth.
  • The interference effect seems more prominent with running, whereas cycling has less impact.
  •  Cardio can improve cardiovascular function and improve blood flow to muscles.
  • Cardio can enhance recuperation by increasing blood flow to muscle and improving cardiovascular health.


Cardio should not be vilified. If done properly, you benefit from both without worrying about blunted increases in lean mass. Much of the research investigating the combination of cardio and resistance exercise performed together has found no impact on lean mass.

A study that compared weightlifting alone to weightlifting plus cardio (i.e., separated by three hours) found that only resistance exercise plus cardio had decreases in body fat (i.e., -11%) compared to resistance training alone (i.e., -6%). Both groups had similar increases in lean mass, but the combined cardio and weightlifting group had blunted peak power.[1] One crucial aspect of this study was that it controlled for calories so that caloric needs were met in all groups, and each group received a whey protein isolate group post-exercise. Whether the interference effect is due to a blunted anabolic signaling pathway or results from being in a caloric deficit remains to be determined.

Several studies have found that a combination of resistance exercise and cardio can simultaneously decrease body fat and increase lean mass.[2,3] Some lifters think they get all the cardio from weightlifting and doing high reps.


One study had experienced weightlifters doing squats and deadlifts to get their heart racing, whereas the other group did weightlifting and high-intensity aerobic exercise training. Both groups had improved cardiovascular function, but the strength training plus cardio group had greater cardiovascular improvements.[4]

Many of the current strongmen who lift cars and atlas stones are now incorporating cardio (in the right dose) into their routines because it makes them overall better athletes. Cardio will result in better muscle pumps by increasing the number of capillaries per muscle area, allowing more oxygen and blood flow to the muscle.[5]

Better blood flow to muscles with higher capillary densities can result in a better anabolic environment. This can be accomplished by low-intensity cardiovascular training.[6] One study found that combined cardio and weightlifting may improve muscle growth. The study investigated cardio in the morning with resistance exercise performed 6 hours later in the evening or resistance exercise alone.

The group that performed cardio and resistance training had greater increases in mTOR (i.e., increasing mTOR increases anabolic pathways) and increased VEGF (i.e., promotes new blood vessels). The author concluded that concurrent aerobic and resistance exercise might enhance the muscle’s anabolic environment compared to creating a catabolic environment.[7]

The key point is that this study separated cardio from resistance exercise by 6 hours; the studies that combined them in one session have primarily resulted in adverse effects. If you do cardio with resistance exercise, ensure it is separated by 6 hours or preferably done on a different day. If you must do cardio and resistance exercises together, ensure the cardio sessions are short. Optimally, it is best to do cardio on opposite lifting days.


Most research on the interference effect has had subjects drink water during exercise. I suggest you drink 40 grams of whey protein and carbohydrates to replenish glycogen and increase protein synthesis during and after exercise.

One study found that muscle protein synthesis was 48% higher with a protein and carbohydrate drink after combined resistance exercise and cardio compared to a control group.[8] A similar study found that muscle protein synthesis increased by 145% after combining cardio and resistance exercise with a protein supplement compared to water which increased protein synthesis by 75%; thus, the protein supplement doubled muscle protein synthesis.[9]

Some evidence suggests that protein supplementation immediately post-exercise blunts genes regulating muscle catabolism compared to a control drink.[10]  The acute studies suggest no interference effect when protein is consumed immediately post-exercise.


The abundance of research shows that combined cardio and resistance exercise increases a protein called AMPK, which blocks anabolic actions in muscles. AMPK acts as a negative feedback loop on muscle growth by reducing muscle protein synthesis.[11] Still, AMPK is directly affected by nutrient availability (calories).[12]

Excessive cardio will result in an excessive increase in AMPK, which could be a major reason for the interference effect. Whey protein and carbohydrates have been found to increase AMPK levels and protein synthesis.[13] Cardio and resistance exercise protocol on an empty stomach results in low nutrient availability and depleted glycogen, which increases AMPK.

A literature review found that protein supplementation in five out of nine studies reported increased muscle mass with concurrent training-mediated. Five out of nine studies reported that protein supplementation enhanced concurrent training-mediated muscle strength and/or power increases. There was a large range of differences in the volume and intensity of aerobic exercise programs, which could have resulted in not all the studies finding positive relationships between post-exercise supplementation and increases in lean muscle mass.

Resistance exercise was thought to deplete muscle glycogen modestly. It has been estimated that an intense, high-volume bodybuilding style workout can modestly deplete glycogen anywhere from 24–40%.[14]

A recent study had lifters perform a high-volume resistance exercise protocol. Total muscle glycogen decreased by 38%, but a different story arose when they analyzed the different muscle fibers. Type I fibers glycogen decreased by 33%, whereas, in type II fibers, there was a drop of 54%.[15] AMPK activity is regulated by glycogen availability.[16]


If you are trying to put on muscle, it’s probably best to limit cardio to low-intensity exercise. I recommend limiting cardio to 25 minutes a week, preferably four times a week. You are still getting the beneficial effects of cardiovascular training but maximizing resources to build muscle.


  •  Training with cardio and resistance exercise in excess can cause blunted muscle growth.
  •  The greater frequency, intensity, and duration of cardio, the greater its impact on reducing muscle growth.
  •  The interference effect seems more prominent with running, whereas cycling has less impact.
  •  Cardio can improve cardiovascular function and improve blood flow to muscles.
  •  Cardio can enhance recuperation by increasing blood flow to muscle and improving cardiovascular health.


1.   Matthew J.-C. Lee et al., “Order of Same-Day Concurrent Training Influences Some Indices of Power Development, but Not Strength, Lean Mass, or Aerobic Fitness in Healthy, Moderately-Active Men after 9 Weeks of Training,” PLOS ONE 15, no. 5 (May 14, 2020): e0233134.

2.   Shawn P. Glowacki et al., “Effects of Resistance, Endurance, and Concurrent Exercise on Training Outcomes in Men,” Medicine and Science in Sports and Exercise 36, no. 12 (December 2004): 2119–27.

3.   Brett A. Dolezal and Jeffrey A. Potteiger, “Concurrent Resistance and Endurance Training Influence  Basal Metabolic Rate in Nondieting Individuals,” Journal of Applied Physiology 85, no. 2 (August 1, 1998): 695–700.

4.   Patroklos Androulakis-Korakakis et al., “Effects of Exercise Modality During Additional ‘High-Intensity Interval Training’ on Aerobic Fitness and Strength in Powerlifting and Strongman Athletes,” Journal of Strength and Conditioning Research 32, no. 2 (February 2018): 450–57.

5.   B. J. McGuire and T. W. Secomb, “Estimation of Capillary Density in Human Skeletal Muscle Based on Maximal Oxygen Consumption Rates,” American Journal of Physiology. Heart and Circulatory Physiology 285, no. 6 (December 2003): H2382-2391.

6.   Naoko Shono et al., “Effects of Low Intensity Aerobic Training on Skeletal Muscle Capillary and Blood Lipoprotein Profiles,” Journal of Atherosclerosis and Thrombosis 9, no. 1 (2002): 78–85.

7.   Tommy R. Lundberg et al., “Aerobic Exercise Does Not Compromise Muscle Hypertrophy Response to Short-Term Resistance Training,” Journal of Applied Physiology (Bethesda, Md.: 1985) 114, no. 1 (January 1, 2013): 81–89.


8.   Rémi Mounier et al., “Antagonistic Control of Muscle Cell Size by AMPK and MTORC1,” Cell Cycle (Georgetown, Tex.) 10, no. 16 (August 15, 2011): 2640–46.

9.  Beelen, M., Tieland, M., Gijsen, A. P., Vandereyt, H., Kies, A. K., Kuipers, H., Saris, W. H., Koopman, R., & van Loon, L. J. (2008). Coingestion of carbohydrate and protein hydrolysate stimulates muscle protein synthesis during exercise in young men, with no further increase during subsequent overnight recovery. The Journal of nutrition138(11), 2198–2204.

10.  Camera, D. M., West, D. W., Phillips, S. M., Rerecich, T., Stellingwerff, T., Hawley, J. A., & Coffey, V. G. (2015). Protein ingestion increases myofibrillar protein synthesis after concurrent exercise. Medicine and science in sports and exercise47(1), 82–91.

11.   P. J. Atherton et al., “Selective Activation of AMPK-PGC-1alpha or PKB-TSC2-MTOR Signaling Can Explain Specific Adaptive Responses to Endurance or Resistance Training-like Electrical Muscle Stimulation,” FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology 19, no. 7 (May 2005): 786–88.

12.   Gabriel J. Wilson et al., “Leucine or Carbohydrate Supplementation Reduces AMPK and EEF2 Phosphorylation and Extends Postprandial Muscle Protein Synthesis in Rats,” American Journal of Physiology. Endocrinology and Metabolism 301, no. 6 (December 2011): E1236-1242.

13.   René Koopman et al., “Intramyocellular Lipid and Glycogen Content Are Reduced Following Resistance Exercise in Untrained Healthy Males,” European Journal of Applied Physiology 96, no. 5 (March 2006): 525–34.

14.   Rune Hokken et al., “Subcellular Localization- and Fibre Type-Dependent Utilization of Muscle Glycogen during Heavy Resistance Exercise in Elite Power and Olympic Weightlifters,” Acta Physiologica (Oxford, England) 231, no. 2 (February 2021): e13561.

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