How Does A Smith Machine Work?

Features

The Smith machine is constructed in a manner similar to a lifting cage. However with the Smith machine, the barbell is affixed to the equipment and positioned within two vertical guide rails. The barbell moves smoothly on linear bearings--on some machines, little more than a fingertip is required to push the unweighted bar up on the guide rails. The Smith machine bar has a fixed plane of movement which can only be moved up and down in a vertical path. Weight plates are added to the ends of the bar to increase resistance.

Benefits

The primary attraction of the Smith machine is its perceived safety. Men who want to "work heavy" with flat or incline bench presses would normally use a spotter to grab the weights if a muscle fails from exhaustion or in event of injury. The Smith machine allows lifters to feel more secure than they would if lifting heavy free weights during a solo workout.

The Smith machine has a dozen or more hooks which allow the bar to be parked at any position along the rail by simply rotating the bar. Many models are designed with adjustable stoppers, which can be placed to automatically stop the barbell at a selected height, providing protection for the lifter during an emergency.

Any barbell exercise regularly performed with free weights where the barbell rests on the shoulders or moves vertically up and down can also be performed on the Smith machine. Smith machine exercises might include shrugs, deadlifts, close stance or sumo squats, reverse lunges, military presses, incline and flat bench presses, and lying triceps extensions.

Cons

Since the Smith machine locks the bar into a fixed plane of movement, the weight is balanced by the machine. This fact means that the neuromuscular benefits achieved with free weights with regards to balance and stabilization are not achievable with the Smith machine.

The movement pattern of the body is considered to be biomechanically incorrect, in that the natural arching motion and core recruitment required while using free weights is unavailable. These abnormal movement patterns may diminish long-term strength gains and increase risk of injury in the active (working) joints.

There is also little to no core recruitment required when performing squats or reverse lunges with the Smith machine, which ultimately creates poor functional flexibility, muscular imbalances and a weak core.