Cardio or weight training, what should you do first in a workout? I’m sure you’ve heard both answers, but has anyone actually given you the right answer? If they have, have they explained the reason why? Let’s explore this topic further to uncover a little of the science behind sequencing cardio and weight training into a workout.
The answer to nearly every training question is really dictated by what you’re trying to get out of a workout. So with that said, if an aerobic adaptation is most important to you, you should do that first in a workout. If a muscular fitness adaptation (say, strength) is important to you, then you should lift first in a workout. Truthfully I could stop there, as that pretty much gives you the answer, but let’s dig down a layer to investigate why this is the case.
Cardio Before Weight Training for Aerobic Adaptation
If you were to put weight training before cardio, muscular fatigue would become the limiting factor to aerobic exercise performance. Since the whole goal of aerobic training is to stress the heart, lungs, and metabolism of the body, if the muscles give out first (because they’re fatigued from strength training) you won’t maximally stress the cardiovascular system. This means less optimal aerobic adaptation and wasted workout time. Additionally, if you place too much stress on the lower body’s soft tissues (such as the Achilles or Patellar Tendons from hard calf or quad exercises, respectively), you could eventually end up with a pretty significant overuse injury.
Weight Training Before Cardio for Muscular Fitness Adaptation
Since nearly all muscular fitness changes are governed by the nervous system, you REALLY shouldn’t fatigue it before you strength train. Being able to recruit (call on) as many muscle fibers as possible is the key to effective strength training. If you do cardio before weight training, you fatigue the motor areas of your brain that send the important signals to the nerves near the muscle to tell them to contract. You also fatigue those very same muscle nerves. Since nerve tissue takes so long to recover, you would virtually render a strength training workout completely ineffective if you did too much cardio beforehand. Finally, cardio will deplete nutrients your muscles need to fuel contraction. During aerobic exercise, you have an alternative fuel you can burn (fat), but during resistance training, you can only breakdown carbohydrate. If those carbs get used up during cardio, you’ll literally have no gas left in the tank for proper strength training.
So the answer to the question of weights first or cardio depends on what you want to get out of the workout (i.e., what’s important to you), and now you know why!