The short answer is: NO, but it depends
You can absolutely crush cardio sessions and heavy overhead presses and hip thrusts and still keep your muscles. You just have to be strategic in your approach. So let's dive into how that is possible!
Concurrent training defined
Concurrent training is defined as a combination of endurance exercise and resistance training.
It does not need to be in the order of endurance followed by resistance training (this has been looked at in research which we will look at later)
Going back to the early 2000's it was speculated that the combination of endurance and resistance training would cause what's known as the "interference effect". The interference effect means that if you were to do both training styles together, your muscle strength/power/gains would be compromised due to excess fatigue, fiber type shift (the body will favor shifting to more slow twitch fibers which are prevalent in endurance activity), a more daily/weekly catabolic (muscle breakdown) state, and the inability to recruit motor units efficiently (1). What this model from the paper aims to explain is that it simply cannot be done where you can do both training methods and not have the body favor the demands of the endurance activity.
As research has looked into this a bit more in recent times, there have been enough studies done to where we have access to meta-analysis and systematic reviews. These are papers that are seen as a more credible source to reference because these types of papers combine studies that fit the criteria of concurrent training (for example but could be for any topic). Meta-analyses include all the fun data and statistical tests, and systematic reviews summarize without the data and tests so having access to both helps with understanding a subject more in depth.
If you look in the field of sport it's easy to see this being done consistently. Olympic sprinters are some of the most muscular athletes in professional sports and are constantly running/sprinting along with weight training. There are also NFL players who exhibit some insane physiques. And of course, the bodybuilders who do endless cardio on show prep who understand how to make recovery/nutritional/training changes to maintain the most amount of muscle mass. There are important variables to consider when making a plan and you will learn more about those later in the article.
So what does the research say?
Schumann et. al. found that looking at aerobic training with strength training does NOT interfere with the development of maximal strength and muscle hypertrophy. The papers included in this meta-analysis looked at the type of endurance training (running and cycling), frequency of weekly sessions (>5 vs <5 sessions), training status (newbie vs veteran), and even age (2).
What they did find was compromised was explosive power meaning your ability to move the weight fast was interfered due to the combination of endurance and strength training. They speculated that the RFD (rate of force development) was impaired due to less voluntary neural activity, along with the discharge of motor units (which helps improve RFD). Fatigue seems to be the reason why this occurs according to the crew who published it. Thus they recommended completing an endurance and explosive power session separately vs in the same session.
Vechin et. al. found that very intense HIIT protocols such as repeated sprints or resisted sprints minimized the chances of the interference effect on muscle strength and mass. They suggested because the type of cardio activity completed (near max effort) has similar neural signaling and muscle activation response to strength training that they complement each other thus limiting muscle breakdown (3).
Wilson et. al. looked at the modality, frequency, and duration of endurance training vs strength and hypertrophy training with 3 groups (running and lifting, cycling and lifting, and lifting alone) and noted that there is indeed an interference effect that occurs. They found that resistance training with running resulted in significant (statistically significant) decrements in both hypertrophy and strength. They speculated this is due to running having such a high eccentric component in each foot contact that there was greater muscle damage observed in the running and lifting group vs the cycling and lifting group and the lifting group alone (4).
Their suggestion to mitigate the interference effect was to supplement more cycling than running, and consider variables that would cause further tissue breakdown such as excessive volume of either lifting or cardio, recovery, and nutrition
So how can it be done?
There are a lot of variables to consider here. This is why it is important to make a plan and observe what is happening along the way to see if things are trending up or down in both your cardio and lifting. Here are some important variables to consider.
Frequency
How many days per week are you completing cardio and lifting
If you can manage fatigue, you are more likely to limit an interference effect
The research looked at >5 and <5 concurrent sessions per week and found no significant effects. So you are able to do them as much or as little as you like but what will matter most is managing fatigue
Fatigue
Listen to your body!
It is okay to push through soreness throughout the week, it will be inevitable that doing both sessions together will cause some soreness
The issue becomes if you can't get out of that soreness and feel any type of relief because you aren't recovering enough via rest, sleep, nutrition, supplementation, etc
This is most prevalent in the HIIT training community trying to fit in a ton of HIIT sessions along with lifting. HIIT sessions should not be the only method of cardio completed and should incorporate other methods (3).
Fatigue is a catalyst for muscle breakdown so no matter how much lifting you perform, if you aren't getting back or close to baseline recovery then the body cannot grow/get faster/run longer/etc.
Training modality
The type of cardio does not seem to affect muscle growth/strength so pick what you love the most
The method used during cardio also does not seem to affect muscle growth/strength
This includes LISS (low-intensity steady state) up to HIIT (high-intensity interval training)
This can also include conditioning workouts with weights vs a traditional treadmill run
What's going to matter here the most is being able to do multiple modalities to ensure you are getting enough frequency for an adaptation response in the body
If you absolutely love the Stairmaster then go crush that thing! It does not need to change constantly rather what you do on the Stairmaster would need to change (keep reading for recommendations)
Nutritional considerations
If you plan on doing both workouts in the same session then nutrition becomes a big player in performance
Pre-training meals should consist of high amounts of carbohydrates and protein (1-2 palm sized portions of carbs, 1-2 palm sized portions of protein)
If you know your session will last more than 2+ hours it may be wise to bring an intra workout consisting of Essential amino acids, electrolytes, and even some sugar)
Post-training meals should consist of high amounts of carbohydrates and protein (1-2 palm sized portions of carbs, 1-2 palm sized portions of protein)
Throughout the day, emphasize protein intake overall aiming to get around 0.8-1.2 grams per pound of bodyweight
How this can be put together in a weekly plan
Let's use a case study
For example, this person can train 4x per week for roughly 60-80 minutes each session. They prefer to train during the week and enjoy the weekends away from the gym. They want to get into running to do a 10k but also retain strength in the gym to be able to do a bodyweight chin-up.
Here is a mock training week
Day 1: Cardio + Lifting
20 minute HIIT session on the treadmill (20s sprint, 80s recovery)
50 minute Upper body weight session
Day 2: Cardio + Lifting
30 minute stair session (steady state in the 50-60% of HR max)
45 minute Lower body weight session
Day 3: Rest
Active recovery via walk, yoga, deep stretching, etc
Chance to allow for recovery from the 2 days
Day 4: Cardio + Lifting
20 minute conditioning circuit (jump rope 60s, KB swings 60s, sled push 60s)
50 minute Upper body weight session
Day 5: Cardio + Lifting
45 minute jog/walk on the treadmill (2-3 minutes of running, 2-3 minutes of rest for the total time)
30 minute Lower body weight session
Day 6/7: Rest
Active recovery via walk, yoga, deep stretching, etc
Chance to allow for recovery from the 2 days
The important thing to take away from this mock plan is
Rest days break up the 4 sessions
There are different types of cardio sessions being completed
Favoring time duration on the lifting but the expended energy for both will likely even out
Take home
You can absolutely perform cardio and lifting sessions and not see a loss of gains. What matters the most is creating a plan and understanding how to listen to your body and not letting fatigue from sessions inhibit recovery and loss of muscle gains.
Hope this helps :)
D
Sources:
Docherty D, Sporer B. A proposed model for examining the interference phenomenon between concurrent aerobic and strength training. Sports Med. 2000 Dec;30(6):385-94. doi: 10.2165/00007256-200030060-00001. PMID: 11132121.
Schumann M, Feuerbacher JF, Sünkeler M, Freitag N, Rønnestad BR, Doma K, Lundberg TR. Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis. Sports Med. 2022 Mar;52(3):601-612. doi: 10.1007/s40279-021-01587-7. Epub 2021 Nov 10. PMID: 34757594; PMCID: PMC8891239. C
Vechin FC, Conceição MS, Telles GD, Libardi CA, Ugrinowitsch C. Interference Phenomenon with Concurrent Strength and High-Intensity Interval Training-Based Aerobic Training: An Updated Model. Sports Med. 2021 Apr;51(4):599-605. doi: 10.1007/s40279-020-01421-6. Epub 2021 Jan 6. PMID: 33405189.
Wilson JM, Marin PJ, Rhea MR, Wilson SM, Loenneke JP, Anderson JC. Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. J Strength Cond Res. 2012 Aug;26(8):2293-307. doi: 10.1519/JSC.0b013e31823a3e2d. PMID: 22002517.
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