Weights before cardio.
I'm not going to pretend that this info came from me. Here's what BSL taught me, and I quote:
"Your body has 3 basic forms of stored energy:
1) Creatine-Phosphate/ATP - VERY explosive energy, like dynamite. This happens w/o oxygen, it's anaerobic....the byproduct is lactic acid, that's why you get the burn at intense levels. Stored in muscle tissue. When you are being chased by a Mountain Lion, you're burning this stuff big-time!!!
2) Glycogen - Moderately explosive, like gasoline. This requires oxygen....so it's aerobic. Stored in muscle tissue, liver, etc. When you are running, swimming or pushing hard on the cardio, this is burning.
3) Fat - slow burning energy, like wood burning. Also requires oxygen...so it's aerobic. Stored in fat cells. This is what your body will fall back on as an energy supply....but only when your blood-sugar is low, and this starts to happen after approx. 20 minutes of exercise (or so theory has it).
Weight-lifting is intense exercise, it demands "explosive" fuel...that generally means a blend of Glycogen & Creatine-Phosphate/ATP...not so much fat. Fat burns (can be oxidized/utilized) at a very slow rate...so the saying goes: you can't burn fat fast enough to fuel a muscle contraction when weight-training.
So you wanna do your weight-training when your blood is all full of sugars and use-up all the strong energy. Your muscles need all that energy to perform their work. That's why your not supposed to weight-train for over an hour, cause you only have so much stored up & ready to go..after an hour you may start into catabolism, where your muscles start using surrounding muscle-tissue as energy. As the theory goes.
AFTER weight-training your blood-sugar is low and your body is depleted: now is the time to strike! Your body will be turning to it's reserves...the precious precious FAT. Fat can only burn at a slow rate, so you just need to get into a moderate/slow aerobic exercise and get it on....that's when you can really start melting fat off your body. "
Sounded good to me, so that's what I do. I recently had my trainer advise the same protocal--2 votes!