While gyms, health clubs, and spas contain acres of the newest and most expensive equipment, they still cannot improve on the kinds of basic, free weight exercises that can be done in the comfort of one's own home. Anyone wishing to build a home gym, either as a supplement to their health club membership or as their primary place of exercise, would do well to keep the following basic principles in mind.

The first and most basic consideration for weight training is the weights themselves. Two options are available, standard plates and Olympic plates. Unless you already own a large amount of standard weights, Olympic weights are far and away the best option. These plates come in larger sizes, and have a two inch hole in their center.

What makes Olympic weights special is the bar, which has movable collars. These collars help prevent the transfer of momentum from the lifter to the weights themselves, and promote a more natural, smoother motion.

The other key piece of weight training equipment for most users will be the bench. The brands and models of weight benches are bewildering, but the key things you want to look for are adjustablity, the width of the bar supports, the quality of the padding, and the thickness of the supporting bar running beneath the bench itself.

Adjustable benches allow for a different range of exercises and body-types. Be sure the bar supports are at least four feet apart -- not only is this more stable, but it will not interfere with the lifter having a proper grip on the bar.

A note on machines: while some machines provide exercises that cannot be done with free weights, the overwhelming majority of machines merely duplicate a free weight exercise. Machines have their uses, but should not be considered a primary form of training as they do not allow for the body's natural range of motion, and can create strength imbalances. They also will not strengthen a lifter's joints and connective tissue as free weight training does.

From a basic weight set and bench intermediate users will want to explore other options. Dumbells are valuable training aids, either as an alternative to barbell exercises or as a way of training muscle groups in isolation.

A power rack or cage is the ultimate in home gym safety, as a lifter can exercise within its rectangular frame and pursue heavy squats and bench presses secure in the knowledge that the rack's safety pins will prevent injuries. Other basic equipment includes chalk, for grip, and knee wraps or weight belts to protect an area during heavy lifts -- though users should never become too dependent on these aids.