Thanks for the great question! It's not really an issue in terms of effectiveness - it's more about each individual, their lifestyle, and training goals. I'll try and make it simple with the pros and cons of each. First off, if you are interested in hypertrophy (increasing muscle size), muscle mass will increase at a lesser rate if performing weight training and a cardio program concurrently - whether it's on the same day or not. However combining both is very effective for weight loss and overall health. A few good things about doing everything on the same day are: it requires less number of days in the gym; and your weight warm up is already built in to your cardio session so it's time effective. The cons are that you may feel less energetic about doing the second portion of your workout after going hard on the first; and the sessions may run long in order to fit everything in. The pros of splitting your workout up are: you are more recovered between you cardio and weight sessions and thus you feel fresher and it's easier to put all your energy (psychological and physical) into one; you may be able to fit more exercises in if you are limited on time per day. The cons of the split include: more days in the gym (up to 6 to see desired improvements). So as you can see, there is no clear answer - it really depends on you! For more help on setting up an efficient program that's right for you, please contact Chris at 220-4196 for more information about our reasonably priced Personal Training Services.