Cardio Kills Gains? What 43 Studies Tell Us About Lifting and Running
The myth that won’t die — and why the science says something completely different
Picture this: You’re lacing up your running shoes after a solid leg day, and that guy from the gym — you know the one — shakes his head in disgust. “You’re throwing away your gains right now.”
Sound familiar?
You’ve heard it echoed in every gym, fitness forum, and Instagram comment section: “Cardio kills gains.” Maybe you’ve even lived it, skipping morning runs because you’re terrified they’ll sabotage your squat progress. Or perhaps you’re a runner who’s convinced that touching a barbell will turn you into a slow, bulky mess.
Here’s the truth: You’ve been lied to.
Not maliciously, but the fitness industry has been misinterpreting research for decades, turning nuanced scientific findings into oversimplified rules that don’t reflect reality. Today, we’re diving deep into what 43+ studies reveal about concurrent training (doing both cardio and strength work).
Spoiler alert: the story is far more optimistic than you’ve been told.
The Study That Started It All (And Why Everyone Got It Wrong)
In 1980, the Hickson study first identified the “interference effect.” This single piece of research has been cited endlessly to support the idea that cardio and strength training don’t mix.
However, here’s the context everyone conveniently ignores: the participants were doing cardio six days a week for 40+ minutes per session. We’re talking nearly 5 hours of additional cardio weekly on top of strength training. These weren’t casual fitness enthusiasts — they were essentially trying to become elite endurance athletes while powerlifting.
The dosage makes the poison, and this study used a lethal dose.
What Happens When We Look at the Big Picture
Fast-forward to 2012, and researchers Wilson and colleagues gave us our first comprehensive view through a meta-analysis of 21 studies involving 422 participants. Their findings initially seemed to confirm our worst fears:
“Concurrent training reduced strength gains by 31% compared to strength training alone.”
Scary, right? But here’s the crucial context that gets conveniently omitted: this reduction was compared to doing only strength training. The participants were still getting stronger, just not as dramatically as they would have if they’d completely avoided cardio.
Think of it this way: if you could gain 10 pounds of muscle doing only strength training, concurrent training might net you 7 pounds instead. Still impressive, considering you’re simultaneously improving cardiovascular health, endurance, and overall fitness capacity.
But the story gets even better.
The Plot Twist That Changes Everything
In 2021, researchers Petersen and colleagues published an updated meta-analysis including 43 studies, more than double the original analysis. Their findings fundamentally challenged the conventional wisdom:
“Well-trained individuals show minimal interference effects when concurrent training is properly programmed.”
Translation: if you know what you’re doing, the interference between cardio and strength training becomes almost negligible.
Meanwhile, a 2018 meta-analysis by Sabag and colleagues revealed another game-changing insight:
“High-intensity interval training showed 50% less interference compared to moderate-intensity steady-state cardio.”
Suddenly, the picture crystallises. The type of cardio matters just as much as whether you do it at all.
The Order Effect: Why Sequence Trumps Everything
Here’s where things get fascinating. Murlasits and colleagues’ 2018 meta-analysis examined something most people never consider: the order of concurrent training. Their findings were revelatory:
“Strength training first resulted in significantly better strength outcomes, while endurance training first favored endurance adaptations.”
The culprit? “Residual fatigue.” Whatever you do first gets the benefit of your fresh energy and neurological drive. What you do second gets the leftovers.
This isn’t just academic theory — it has immediate practical implications:
If strength is your priority: Lift first, cardio second (or separate days entirely)
If endurance is your priority: Cardio first, strength second
If both goals matter equally: Alternate which comes first, or separate sessions by 6+ hours
The Runners’ Revenge: When Cardio Helps Your Gains
Ready for a mind-bender? Multiple meta-analyses show that strength training can dramatically improve running performance, while moderate cardio can enhance strength training recovery and work capacity.
Berryman and colleagues analysed 24 studies and discovered:
“Strength training improved running economy by 3–5% with no negative effects on VO2max.”
For the lifters reading this: moderate cardio can improve recovery between sets, enhance work capacity, and support muscle growth by improving nutrient delivery and metabolic flexibility.
The magic word? Moderate.
What “Moderate” Actually Means (The Evidence-Based Sweet Spot)
Based on the collective research, here are the scientifically backed guidelines for concurrent training:
Volume Sweet Spot
2–3 cardio sessions per week
20–30 minutes per session
150–200 total weekly minutes (including warm-ups)
Intensity Guidelines
Prioritise HIIT over steady-state when possible
Sprint intervals show minimal interference
Keep easy days easy, hard days hard
Timing Strategies
6+ hours between sessions for same-day training
Strength first if strength is the priority
Consider alternating days for optimal recovery
The Real Culprits Behind “Cardio Kills Gains”
If the research is clear, why does this myth persist? Usually, it comes down to these preventable mistakes:
Excessive Volume: Most people experiencing interference are doing 5+ cardio sessions weekly for 45+ minutes. That’s not moderate — that’s endurance athlete territory.
Poor Recovery: Adding cardio without adjusting sleep, nutrition, or stress management creates overtraining, not interference.
Inadequate Nutrition: Concurrent training demands more calories and better timing. Under-eating whilst doing both is like building a house whilst someone steals your bricks.
Mismatched Goals: Trying to peak for both a powerlifting meet and a marathon simultaneously isn’t an interference problem — it’s a planning problem.
Your Action Plan: Train Smarter, Not Harder
Here’s what 43+ studies spanning four decades tell us: concurrent training works brilliantly when programmed intelligently.
The question isn’t whether you can do both — it’s whether you should, based on your actual goals.
If Maximum Strength Is Your Priority
Limit cardio to 2 sessions weekly
Always lift first
Prioritise recovery between sessions
If Endurance Performance Is Your Goal
Add 2–3 strength sessions weekly
Emphasise heavy lifting (70%+ 1RM)
Cardio gets priority in scheduling
Focus on strength that transfers to your sport
If General Fitness Is Your Aim
You have maximum flexibility
Moderate amounts of both work synergistically
The “interference effect” becomes largely irrelevant
Focus on consistency over perfection
If You Want to Be a Well-Rounded Human
Congratulations — concurrent training was designed for you
Balance based on what you enjoy most
Adjust volume based on life stress and recovery
Remember: the best programme is the one you’ll follow
The Bottom Line: It’s Time to Get Specific
So here’s your homework: Define your primary goal. Then train accordingly.
Not “get fit” or “be healthy” — those are too vague to guide your decisions. What do you want? To deadlift twice your bodyweight? Run a sub-20-minute 5K? Feel confident in a swimsuit? Have the energy to chase your kids around?
Once you know that, everything else becomes simple. Your training becomes purposeful. Your recovery becomes intentional. Your nutrition becomes strategic.
The beauty of concurrent training isn’t that it lets you do everything — it’s that it lets you do what matters to you whilst building a foundation of general fitness that makes life better.
Your gains — and your heart — will thank you.
References
Wilson, J. M., Marin, P. J., Rhea, M. R., Wilson, S. M., Loenneke, J. P., & Anderson, J. C. (2012). Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. Journal of Strength and Conditioning Research, 26(8), 2293–2307.
Murlasits, Z., Kneffel, Z., & Thalib, L. (2018). The physiological effects of concurrent strength and endurance training sequence: A systematic review and meta-analysis. Journal of Sports Sciences, 36(11), 1212–1219.
Petersen, K., Hansen, M., Aagaard, P., & Madsen, K. (2021). Interference effect of aerobic training on strength and power in resistance-trained individuals: A systematic review and meta-analysis. Sports Medicine, 51(10), 2085–2094.
Sabag, A., Najafi, A., Michael, S., Esgin, T., Halaki, M., & Hackett, D. (2018). The compatibility of concurrent high intensity interval training and resistance training for muscular strength and hypertrophy: A systematic review and meta-analysis. Journal of Sports Sciences, 36(21), 2472–2483.
Berryman, N., Mujika, I., Arvisais, D., Roubeix, M., Binet, C., & Bosquet, L. (2018). Strength training for middle-and long-distance performance: A meta-analysis. International Journal of Sports Physiology and Performance, 13(1), 57–63.
