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What You Must Know About Smith Machines
9/18/2018 12:21:39 PM

The Smith machine is unquestionably one of the single most popular resistance training machines in commercial gyms. In fact, partly due to safety concerns with average gym trainees performing barbell squats and bench presses, many gym owners have replaced power racks and bench press stations with Smith machines. What are the downsides of this trend?
Jack LaLanne, an American fitness celebrity who invented the leg extension machine and the cable crossover, came up with the idea for the Smith machine in the 1950s. He goal was to develop a machine that would enable the user to perform heavy squats without a spotter. LaLanne told Rudy Smith about his idea, reportedly sketching a design on the back of a napkin, and Smith took the drawing to equipment designer and builder Paul Martin. Martin developed the prototype, and Smith got the machine installed in a Vic Tanny gym in Los Angeles.
As a starting point for this discussion, a Smith machine is a barbell that moves along steel guide rods in a vertical direction. The more popular versions are slightly inclined, which many find more comfortable for exercises such as squats and bench presses. The operating mechanism consists of hooks attached to the bar that can be rotated to rack and unrack the weight, along with adjustable safety supports that can stop the barbell at a specific height. The safety supports enable the user to safely perform exercises to failure without a spotter (although for liability purposes we must say that a spotter should be used on all heavy lifts).
The barbell used with a Smith machine usually weighs about 45 pounds, but a few additional pounds are added to that starting weight from the guide rod cylinders the bar is attached to. Because many gym users want to use lighter starting weights for some exercises, especially if they are used for rehabilitation, many Smith machines come with a counter-balance pulley system that reduces the starting resistance. Depending on the manufacturer, the starting weight could be as light as five pounds. As such, someone who does a Smith machine squat with a pair of 45-pound plates on each side could be lifting 190 pounds, not 225.
Although Smith machines are considered safer than free weights, consider that many serious accidents – including at least one death – have been reported using this equipment. According to Dr. Marc Rabinoff, a sports/liability expert who has consulted in over 500 ligations in the health and fitness industry, injuries using Smith machines often occur because the user did not know how to properly use the machine or ignored safety guidelines. Specifically, they didn’t place the safety supports in a position to catch a failed lift at the appropriate height.
Rabinoff has consulted on litigations that occurred when individuals became quadriplegics by guillotining themselves during a Smith machine bench press or collapsing at the bottom of a Smith machine squat (which is less of an issue with free weights as the user can often toss the weight off their shoulders). One lawsuit occurred when a company made a Smith machine with fixed safety supports, believing that at the height the stoppers were set a spine would bend, not break. Rabinoff said that in one case, while performing a Smith machine squat with this machine the user’s spine broke.
The Smith machine is often considered a functional movement like the free bar squat because a barbell is used. Not quite. Although you can perform many of the same movements with a Smith machine as you can with a barbell, because the bar moves along a fixed path there is less need for stabilization, creating structural imbalances in the muscles.
With a free weight squat, the bar can move in different planes of motion so that the body can position itself into the most advantageous positions to produce force. With a Smith machine squat you are forced into a specific bar path, just as you would be with a leg press or hip thrust sled. Research has shown that muscle activation using EMG analysis “…averaged over all muscles during the free weight squat was 43% higher when compared to the Smith machine squat.” As such, there is not a direct correlation between how much you can squat on a Smith machine and how much you can do in a regular squat. It can be frustrating for those who have made significant gains in their Smith machine squat to find that their free weight squat performance did not improve to an equal degree.
In addition to regular squats, many trainees like to perform Smith machine squats such that their feet are in front of the bar to attempt to increase the work of the quadriceps. It also reduces the stress on the lower back, as the lift resembles more of a hack squat. However, because the hamstrings are less activated during a Smith machine squat compared to a free weight squat, this exercise can create extreme stress on the ACL.
For the upper body, it’s been argued that because the shoulder functions in three planes of motion and the Smith machine bar only travels in one plane, Smith machine presses could create relative weakness in the rotator cuff muscles. Further, this fixed movement pattern could, over time, create a repetitive stress injury (RSI) such as tendonitis (in which the tendons become inflamed). True, but if someone has an injury that prevents them from performing barbell shoulder or bench presses, using a Smith machine temporary until the injury heals will help the user to at least maintain their strength and muscle mass levels until they can return to free weights.
Another problem with the argument that Smith machines cause RSI from pattern overload is that the same could be said about any machine exercise that moves the body in a fixed path. Thus, one way to avoid pattern overload is to simply change your exercises frequently and occasionally include some free weight movements to work the stabilizing muscles. Sure, barbell and dumbbell shoulder presses rule, but it’s fine to occasionally train your shoulders with a Smith machine shoulder press, a vertical press machine, and a lateral raise machine. You can even combine these exercises, such as by starting with barbell shoulder presses and finishing off with a few additional sets of Smith machine shoulder presses to failure.
Smith machines are here to stay. Yes, they have their limitations, but used wisely they can be a valuable tool to help you stay motivated to train by providing variety to your workouts.
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