Indoor rowing machines, commonly called ergs by rowers, can give total and exhausting workouts. When you're selecting an erg, the options start with magnetic- vs. air- vs. water-based resistance.
Magnetic-based ergs are generally the cheapest and work well in private homes because they make the least noise. Although there are some very good magnetic ergs, most of are low quality and frequently do not have enough range of movement to allow a proper rowing stroke. They may not work well for rowing training.
The most common erg uses a flywheel to create air resistance. This type of erg is durable with a very smooth motion and is far more comfortable to use than a magnetic erg. Air-resistance ergs can be very loud and a little more expensive, but they are the most popular variety, and are used for training in almost every boathouse and in indoor rowing competitions.
The third and most expensive type of erg uses a water chamber to provide resistance. These ergs feature a very smooth stroke and come the closest to simulating actual rowing. They work well in private homes because they are very quiet and are generally more attractive than other ergs, frequently constructed with wood instead of metal or plastic.
All three ergs will give you a vigorous workout, so choose one that feels comfortable to sit on and row and always use proper technique. Any erg can cause back pain and other problems if you use it incorrectly.