To get great results from your training be it cardio gains or muscle gains or just health gains, it is very important to get your training program right its no use doing 5 sets of 15 reps if you goal is to be a power-lifter, you'll just never get there if your not lifting high weights for low reps and doing compound movements like clean and jerk and dead-lifts and most importantly of all overloading your muscles. But if your goal is to improve your fitness build bone density or just tone up 5 sets of 15 is probably fine.
Similarly its also not the best training plan for a long distance runner to just run the distance they are aiming for, yes your cardio system will get a great work out but and you'll know that you can make the distance but you'll struggle to get faster if you don't do resistance training especially on your legs or if you don't do interval training to increase your VO2 max which helps you run faster for longer.
In short there are different training programs for everyone's goals and for different people wanting to achieve the same goals. In the end the best training for you is probably the training you enjoy the most. the reasons for this are obvious if your not enjoying a work out your unlikely to stick at it.
Now this can pose a problem for people wanting to get fit who just don't like to work out who have tried all sorts of sports training program and activities but just can't stick with them. But if your problem is that you don't want to spend hours at the gym or running in the park you don't have to if you structure your work outs properly you should be able to get a great full body work out in 30-40 minuets including cardio.
Using training ideas like supersets or trisets and doing cardio exercises like star jumps or stepping between your sets is a great way to both shorten the length of your work out, without compromising results. It will also help you to mix up your workouts training in different ways shocks your body and can help you to avoid the dreaded plateau if your a seasoned trainer or getting bored if your just starting out.
Stay tuned I'll have more on this soon.