What does it do? If you're looking for a complete workout then the rowing machine is ideal for you: it works 80% of the body's muscles, mostly your upper body and legs (arms, biceps, back, abs and leg muscles).
How do I choose the right one? The more comfortable it is, the better! The ideal rowing machine has a central rowing structure with air resistance (this produces the same effect as being on the water) proportional to rowing speed. It's also worth choosing one that's silent, foldable, hard-wearing and has a programmable computer so you can track the progress of your workout.
How often should I use it? Since this machine uses so many muscles, it's best to not use it every day. Instead, use it for around 30 minutes once or twice a week, increasing your heart rate to a suitable level.
WaterRower rowing machine, £900.