For a complete body fitness workout, I highly recommend this article on rowing! While it was written about how the Apple Watch apps work with rowing, I actually found this article very informing on the benefits of rowing compared to most cardio workouts. He also shows you how to do it right which, includes instructional video.
I have been rowing to warm up for my weight workouts for a while now, and I can say from experience, it’s the most complete workout I have gotten on one machine. Legs, butt, core, and upper body all have a part in this awesome workout, and I feel like I just finished a crossfit class for bad-boys when done. Now, I’m all about weights, but do this right, and it’s all the workout you need if you want to change it up every once in a while.