One of the most frequently asked questions I get as a fitness professional is, "If I am going to do my cardio and strength training on the same day, which comes first?"
Experts are definitely split on this issue. The majority of fitness experts will advise you to do the cardio after the weight training, because if you do cardio first, it uses up much of the energy source for your anaerobic work (strength training) and fatigues the muscles before their most strenuous activity. This same view holds that strength training first will deplete the muscles' stored carbohydrates (glycogen or sugar), and therefore, will enhance fat burning during the cardio workout due to the lack of available sugar for fuel.
However, there is no credible, concrete research that proves this, and what it should really come down to are your fitness goals.
For instance, if your primary goal is to increase your aerobic endurance or lose body fat, then you should perform cardio first. If your primary goal is to increase muscular strength, then do strength training first. To get the most out of your workout, perform the exercise that is most important to your goals first, when you are not fatigued.
If your fitness goals include overall improvements, finish your workout with the type of exercise you enjoy most.
I see a lot of people who have set a goal of losing fat around their belly and they spend an hour on the bench press or doing tons of curls. Why? Because they are good at those and they see the results. The problem is that when they are done with those, they are too fatigued or don't have time to have a quality cardio workout.
The same applies to the folks I talk to who want to firm up their arms but don\'t like to lift weights because they don't want to "get big".
Lifting weights does not automatically equal "big," and you won\'t firm those muscles on the treadmill. Spend 10 minutes at the beginning of your workout working on your legs, chest, back, shoulders and arms and then go for your stair stepping marathon. You will be shocked at how much more toned you become.
The bottom line is this, it is better for you to have consistency in your exercise than to worry about the two extra calories you might burn from doing weights or cardio first. Analyze your goals and plan your workouts to reach those goals. Before you know it, your bellies will begin flattening out without sacrificing any of your chest or bicep size. Additionally, your triceps will have incredible shape and you will still be able to take the stairs to the top of Mt. Everest.