Originally Posted by koffee brown
It is not a MUST that one must do both aerobic and weights on the same day. That's erronous thinking. However, you should be doing both aerobic activity and weight training and incorporating full body weight training, not just select muscles.
Having said that, it is better to start with weight training, then move to aerobic training. If anything, you can fatigue your muscles too easily with aerobic training, so better to do your resistance training first, then follow it up with your aerobic training.
Bottom line- do weights, then aerobics. And as long as you're getting in a full body workout two times per week (or however you split it up), you're doing pretty good.
Koffee
But you risk injury to the muscles if you just walk into a gym and start lifting. Same with stretching ... if you walk in and plunk yourself down on the stretching mats and go to it, you could tear something. It has been proven that it is a good idea to warm up first.
That warmup doesn't have to be a full-blown sprint on the treadmill or anything, but walking, or a light jog, or a spin on the exercise bike, for at least 10 minutes - enough to get your heart rate up a bit and get some blood flowing - will warm up your muscles so that you can continue with weightlifting and stretching.
And as for two times per week ... well, the recommended amount of exercise is now 60 minutes per day, 5 to 6 days a week. That doesn't necessarily mean weightlifting 6 days a week, or jogging/cycling 6 days per week, but we should be active in some way almost every day.
Just another comment ... when I was heavily into bodybuilding many years ago, my trainer put me onto a 4-day weightlifting cycle, as follows:
Day 1: Back, Biceps, Abs
Day 2: Triceps, Shoulders, Chest, Abs
Day 3: Legs, Abs
Day 4: off
And the reason for that is so that the muscles have recovery time in between, because we all know that muscle grows during rest and recovery, not during the actual act of weightlifting or exercise. With that cycle, I would workout my back muscles (for example) on Day 1. On Day 2, the back muscles would still probably come into play a little bit. On Day 3, I would hardly use my back muscles at all, and then I'd rest ... so my back muscles would essentially have 2.5 days off.
I'm just getting back into this all again, so I'm not following that cycle yet, but I hope by Christmas I'll be there.