The quick answer is, unless your priority is stamina and endurance, then cardio should always be done after weights. Let’s unpack this a little.
Muscle Ultimately Burns More Calories
If you are maximizing total calorie burn, sure. Cardio burns more calories in a given 30 minute session than weights. I’d recommend this for marathon athletes, obstacle course runners, etc. Just like any sport, your training should prioritize that which caters to your sport.
For anyone looking to build muscle over the long run, there's an adaptation that takes place when you lift weights. That creates a signal to build more muscle, so you can handle the stimulus being given (aka a workout session with a given load). As you build more muscle, you burn more calories at rest. Muscle is calorically expensive to hold onto your frame. This is what’s so great about resistance training. It’s the only form of exercise that allows you to burn more calories the longer you do it. For those dieting, it’s even more important, because the stress of an appropriate lifting session tells the body to hold onto that calorically expensive muscle. Cardio on the other hand, prioritizes burning fat first, but over time, preserving fat for survival.
Cardio Beforehand will Affect Your Progress
Doing cardio beforehand can also hinder your workout session. This obviously is no good if gaining size is your goal. Weights require so much focus, energy, and demand to execute properly. You want every available resource you can summon to help achieve that. In fact, to emphasize this example, I encourage you to try doing a 30 minute cardio session before your workout one day, and then afterwards on the other day. How did it feel?
I know for me, I feel a little tired going into my workout. This not only may prevent me from maximizing my performance (and thus not maximizing my gains), but it also puts me at a higher risk for injury. Running on the other hand, requires no mental effort.
What if You Need to Warm Up?
The only thing left to consider is those of us who like to get the blood flow going before a lift. Sure, a light jog for 10 minutes can do that, but it’s not really priming the muscles you’re about to work. In other words, you’re really not getting that much of a proper warm up.
If warming up is your concern, then you need to know a TRUE warm up means activating the muscles you are about to work for that session. So, if you are going to hit maybe the back or chest that day, how would running on a treadmill be beneficial for increasing blood flow to that area?
A better use of that 10 minutes is to choose 2 exercises for each area of the body you are about to hit that day. For example:
Upper Body - Handcuffs to rotation,threading the needle, and wall slides
Trunk/Core - Lizard with rotation, windmills, and deadbugs
Lower Body/Hips - 90/90, Single Leg Bridge, and active pigeon
You should find not only do you wake up the muscles are normally dormant in most of us before going into a lift (scapula muscles, hips, low back, etc.), but that your muscles actually feel way more warmed up and primed going into your major lifts. If you aren’t sure what those exercises above are, or want more details into how priming works, be sure to check out our MAPS Prime Program or check out all the free resources on our YouTube Page. 
