Ok, so this article doesn’t really have anything to do with dates…but I needed a catchy headline so bear with me. I’m sure most have you have heard something along the lines of “you should do your weight training first and cardio after” or even “only do cardio on rest days”.
Where does this idea come from, anyway? Well, it’s actually a pretty reasonable explanation. I’ll try and keep most of the explanation pretty easy to understand. I’ll try and highlight why, at a physiological level, it makes sense to do your resistance training before your cardio.
Aerobic vs Anaerobic Exercise
The first thing we should come to understand to help us answer our question is the difference between aerobic and anaerobic. To keep things simple, aerobic implies something is performed in the presence of oxygen, and anaerobic implies the opposite—without oxygen. While a single exercise probably isn’t entirely one or the other, here’s a few examples of both:
- Weight Lifting
After looking at a few of these examples, it should be relatively apparent that anaerobic exercise tends to be exercise performed for a short duration at a HIGH intensity. Yeah, there’s a reason it burns when you’re squatting big weight. Aerobic, on the other hand, would be exercise performed at a longer duration but generally LOWER intensity. The zones aren’t necessarily black and white, though. It’s entirely possible to have an exercise begin at the aerobic side of the spectrum and become anaerobic as you continue the movement!
This article does a pretty good job explaining the distinction—A good way to test this for yourself is exercise at a moderate intensity and very slowly increase the intensity until you hit a point where you can’t go any longer. If you have a heart rate monitor, you now have a pretty good idea of where you start to dip into the anaerobic zone while exercising.
Energy For Anaerobic Exercise
Well, energy for each of these types of exercises is generated by slightly different mechanisms. Anaerobic exercise relies primarily on available glucose to create energy. To keep it simple, this means you need to have energy sources that are quickly available and easy for your body to use to fuel the exercise. This is why it’s usually a good idea to eat carbohydrates before a weight training session!
Ever wonder why your muscles “burn” when you lift weights? Well, it’s because of lactic acid buildup. The process by which you fuel anaerobic workouts is called Anaerobic Glycolysis—or the conversion of glucose to lactate. This process is VERY efficient at providing you energy quickly (ATP, in this case), but the by-product is lactate. The “burn” you feel in your muscles is a result of the buildup of this!
Energy For Aerobic Exercise
Aerobic exercise, on the other hand, doesn’t rely nearly as much on available glucose. Recall that aerobic means “in the presence of oxygen”. With aerobic exercise, your ol’ pal oxygen helps you out quite a bit. During an aerobic period, glycolysis gets to make use of oxygen to help you avoid the lactate by product. The result of this is that aerobic exercise can be performed for a much longer duration than anaerobic exercise!
You start to move into the anaerobic zone when you exceed your body’s ability to refuel your muscles with oxygen. You’ll notice this—you start feeling the “burn” in your muscles, and it becomes impossible to keep your muscles working past a certain point. You’ve hit your lactate threshold when the burn becomes so intense that you can’t go any longer!
“So what does this have to do with weights before cardio?”
Recall that anaerobic exercise absolutely requires carbohydrate stores to help fuel the movement—you can’t rely on oxygen. That’s not to say that doing cardio won’t use up these stores as well, though. Consumed carbohydrates are readily available, and your body is going to do what it does best–be efficient.
If you do your cardio BEFORE weight training, you run the risk of using some of that precious glucose! You NEED this for effective weight training, whereas aerobic activity like running can rely more on oxygen and stored glycogen to fuel the exercise.
What’s more—if you perform cardio after you’ve depleted some glycogen, you get to rely more on fat metabolism for some of your energy! So the benefit is twofold:
- You use your carbohydrates for fueling an intense weight training (anaerobic) session
- You use more fat metabolism when it comes time to do your cardio
“Am I shooting myself in the foot if I do cardio first, then?”
Maybe not. A lot of having an effective weight training routine is just doing what works for you! If you’re the type that prefers to run first, and you still have enough energy to lift with intensity, then by all means do that! Or maybe your primary goal is to be a faster runner, in which case cardio/interval training first might make more sense.
I think most people will find that weights first and cardio later tends to be the most effective approach, though. Personally, I couldn’t imagine doing any reasonable amount of cardio and then squats afterwards! It’s all about experimenting and finding out what works best for you, though.
Well, I hope this was helpful. I’m a huge nerd so I find it incredibly interesting to learn more about our internal processes that fuel our workouts. Well, what are you waiting for? Get out there and go crush some weights! Just save the cardio for afterwards. Or….don’t do it at all and just do a set of 20 rep squats. If one set of these doesn’t make you feel like death, you truly have an iron will.
Stay tuned for more on the subject!