3 Reasons Why You Should Perform Cardio After Lifting

If you want to get bigger and stronger, here's why you should save cardio until your last set of curls.

In the past, you may have felt like you’ve needed to choose between being a lifter or being a runner. Well, you don’t. Not only are both disciplines good for you, but they complement each other. The cardio you gain from running will grant you more endurance to lift more weights for more reps, translating to more muscle. On the flip, strength training will build up your calves, quads, and core — the main muscles that allow you to run more powerfully.

So you know you can (and maybe should) run, even a little, in addition to strength training. However, now the question becomes, “when do I run in my workout?” Based on the title of this article, you can probably guess the answer. Running after you lift keeps you fresher for the weights, lets you lift heavier, and increases your muscle-building potential. Below, we’ll dive into the science and expand on those three reasons.   

It Prevents Pre-Workout Fatigue

There are more complicated, science-based reasons for this below, but cardio is tiring, and being tired before you lift weights robs you of more muscular endurance, focus, and energy to lift. Running on the treadmill is one of the healthiest activities you can do for your body, but excessive running can leave an athlete tired, which will impact the amount of force they can produce.

 

 
 
 
 
 
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If your muscles or nervous system is even slightly impaired, then you’ll have a tough time performing optimally under the bar. Not to mention, fatigue can also impact your mental sharpness, which may leave you with a lack of focus. This can be especially true for those who lift later in the day and already have a hard time with mental focus. This 2018 study of endurance athletes showed that mental fatigue impairs your endurance and cognitive abilities. (1)

You’ll Lift Heavier Weights

Excessive cardio pre-lift can also deplete the energy system you need to lift the heaviest amount of weight you’re capable of. 

The body has three types of energy systems: ATP-PC, glycolytic, and oxidative. These energy systems are important for different physical activities, and all shine under different circumstances. For example, a sprinter will employ more of their ATP-PC energy system, while a marathon runner will use more of their oxidative system. Each energy system plays a different role depending on the activity. Here’s the time it takes each one to be utilized: 

  • ATP-PC Energy System: (+/-) 12 seconds
  • Glycolytic Energy System: 30-seconds – two minutes
  • Oxidative Energy System: two-plus minutes

Keep in mind these are estimates, and many factors will influence the effects each energy system has on different lifters. The table below provides different scenarios when each energy system is used for cardiovascular and resistance training.

Cardiovascular Training Resistance Training 
APT-PC – Short, all-out sprints ATP-PC – Heavy lifts in 1-3 rep range
Glycolytic – 400-800 meter runs Glycolytic – Heavier lifts in 4-8 rep range
Oxidative – 800+ long-duration runs Oxidative – High-rep work 10+

So here’s what all that info means for you: If you’re performing high-intensity sprint work, then you’ll tax energy systems that heavier lifts require as well. This is why lifting should take priority over cardio training when performed on the same day. If you sprint before your workout, you would have used up all the energy your body has to lift weights — the APT-PC energy system. 

For example, your body only holds so much glycogen in your muscles that can be used for training, which comes primarily from the glycolytic energy system. If you use the amount you have stored for cardio before lifting, your strength and power output may suffer due to a lack of energy resources.

With that in mind, you’ll have two scenarios:

  • Do you want to break up high-intensity resistance/cardio work into different days?
  • Or do you want to perform a full high-intensity resistance/cardio all on the same day?

This will be up to the lifter based on the training being performed. Some athletes will benefit from doing an all-out high-intensity day — e.g., functional athletes — while others might benefit from breaking them up — e.g., strongman athletes. Rest after training days should also be considered when answering the above scenario. 

What will benefit your training goals best?

You’ll Be Primed to Build More Muscle

Enzymes are chemicals in your body responsible for creating chemical reactions in your body, including building muscle, and some enzymes have been hypothesized to conflict with resistance and cardio training.

The enzyme mTOR (mechanistic target of rapamycin), for example, is a key player in protein synthesis and has been seen to elevate post-workout. This elevation can last up to 48-hours post-workout. And the enzyme AMPK (5′ adenosine monophosphate-activated protein kinase) has been seen to be produced more so after low-intensity-based exercise. 

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What’s more, studies have demonstrated how these two enzymes influence each other while performing cardio or resistance training, and the effects may impact your performance. A study from 2011 suggests that increased AMPK acutely produced during endurance training lowered mTOR signaling. (2) A hypothesis from another study suggests that AMPK and mTOR’s linkage revolves around AMPK’s ability to override mTOR signaling. (3)

Simply put: If you perform cardio before lifting, you’ll be lowering the effects of the enzyme responsible for building muscle. 

The overriding of mTOR may slow down the rate or amount of protein synthesis you experience post-workout. For someone interested in packing on the most amount of strength and size as they can — like a bodybuilder — this can be counter-productive. This factor is on the lower-end of importance. Fatigue and energy demands will play a much larger role in your overall gains in each style of training.

In Conclusion

Cardio and lifting can co-exist, but there should be a strategy behind how you program them. If building strength and muscle is your main focus, then you’ll benefit most from performing your cardio post-lift. When deciding where and how to program cardio and resistance training into your regimen, consider your sport, training style, rest, and training history.

More Running & Lifting Content

If you’re interested in learning more about running, lifting, or pairing the two, then check out these other articles from BarBend

References

  1. Slimani M, Znazen H, Bragazzi NL, Zguira MS, Tod D. The Effect of Mental Fatigue on Cognitive and Aerobic Performance in Adolescent Active Endurance Athletes: Insights from a Randomized Counterbalanced, Cross-Over Trial. J Clin Med. 2018;7(12):510. Published 2018 Dec 3. doi:10.3390/jcm7120510.
  2. Mounier R, Lantier L, Leclerc J, Sotiropoulos A, Foretz M, Viollet B. Antagonistic control of muscle cell size by AMPK and mTORC1. Cell Cycle. 2011 Aug 15;10(16):2640-6. doi: 10.4161/cc.10.16.17102. Epub 2011 Aug 15. PMID: 21799304.
  3. Kimura N, Tokunaga C, Dalal S, Richardson C, Yoshino K, Hara K, Kemp BE, Witters LA, Mimura O, Yonezawa K. A possible linkage between AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) signalling pathway. Genes Cells. 2003 Jan;8(1):65-79. doi: 10.1046/j.1365-2443.2003.00615.x. PMID: 12558800.

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