Well, obviously it depends on what you’re trying to accomplish through exercising. If you’re interested in weight loss and/or general fitness, then it’s best to do a minimum of 2 strength training workouts per week (optimally 3 or 4 times) and 3 to 5 cardio workouts per week (minimum of 30 minutes – optimally 45 minutes) working within your target exercising heart rate (or on a scale of 1 to 10 of intensity – you should be between a 5 and 7). To get even more benefit, at least one of those cardio workouts should be an interval training workout, which is basically where you alternate between “work” and “rest” intervals through the duration of your exercise session. For example, you run for 1 minute, walk for 3 minutes… whatever will cause you to work at a REALLY high intensity for a short duration and then recover for a longer duration. This will increase your metabolic rate and cause you to burn even more calories at rest for as much as 24 to 48 hours after your workout.
You also want to avoid overtraining. For every 8 to 12 weeks of consistent weight training, it’s a good idea to take a week off to let your body rest and recover. You can still do cardio during that week, but just take a week off from the weights. Whenever I start to feel run down, achy and sore, tired to the point of exhaustion during the day, irritable, and depressed – I know this is my body’s way of telling me to STOP! So, I’ll listen to the cues my body gives me to take it down a notch. In fact, I just took a week off last week from the weights and was back at it today. I had an awesome workout.
I hope this helps you in designing your own workout program. The main thing to keep in mind is to be consistent, not perfect!