Hi everyone, I'm Dr. Paul Henning, I live and work in Natick, Massachusetts (near Boston) at the United States Army Research Institute of Environmental Medicine where I'm a part of the Military Performance Division.

Our overall mission is to conduct research to enhance physical performance of military occupational tasks or prevent decrements due to physical overload, operational stress and nutritional deprivation. My day to day work includes running and overseeing research protocols, writing new protocols and writing manuscripts for publication.

Although my job is busy and involves many deadlines and some traveling, I make it a priority to workout and eat healthy. I typically workout in the morning with weights and do some ICE sessions a few times a week. It helps that I live really close to Gold’s Gym (like, right next door)! I have competed in bodybuilding in the past and may compete again in the future. It is a pleasure for me to be a part of Team Metabolic Precision. I have known Dr. Paul Cribb for many years and can’t say enough about my respect for him.

Each month I'll help keep you up-to-speed by providing you with the latest research in training and nutrition to enhance performance. In this article, I'd like to provide some recent findings on a key exercise, the barbell squat. 

Free Weight vs. Smith Machine Squatting

Bodybuilders and strength athletes generally prefer “free weight exercises” with barbells and dumbbells over machines because they are unstable and thus provide greater capacity to recruit more muscle.[1] On the other hand, the benefit of machine weighted devices is they are easier to use for beginners and don’t require spotters.

The Smith machine is a piece of equipment found in most gyms. It consists of a barbell that is fixed within steel rails, allowing only vertical movement. Behind each vertical post (runner) is a series of slots on which the barbell can be hooked. The Smith machine allows an individual to perform barbell squats, bench press and other barbell lifts.

However, unlike an ordinary barbell, the Smith machine need not be re-racked after a set of repetitions, it can be secured at any point. This is a big reason why this machine has become popular in gyms – it can make the lift safer for those who weight train without a spotter.

Very few studies have compared a similar movement pattern using free weights and machine in order to determine which is optimal for muscle recruitment and activation.

Researchers from the University of Saskatchewan, Canada recently conducted a study to assess electromyographic (EMG) activity of prime movers and stabilizers during a regular barbell squat (free weights and Smith machine with a maximal load for 8 reps.[2]

EMG evaluates and records electrical activity produced by skeletal muscles.[3] The researchers hypothesized that the Smith machine squat would evoke higher upper leg muscle activity because of less requirement to stabilize. In the free weight squat, the researchers suspected that activity of muscles in the trunk and lower leg would be higher because of the need to stabilize throughout the movement.

So what did the results say....

Results showed that the free weight squat educed a 34%, 26%, and 49% higher EMG mean absolute value from gastrocnemius, biceps femoris and vastus medialis muscles, respectively. Recordings from the vastus lateralis muscle were also higher in the free weight squat.

Therefore, the prime-mover muscles were activated at a higher level during the free weight squat.

In fact, when averaged across all muscle groups, the free weight squat elicited a 43% higher EMG compared to Smith machine squat.[2]

To clarify, this study was designed like a typical training session -  the participants used heavy weights for a determined "maximum-effort number of reps. In this case, 8RMs were used. Contrary to the author’s hypothesis, leg muscles showed greater EMG activity with free weight squatting compared to Smith machine squatting.

What do these results mean for you....

When it comes to exercise selection for effective workouts, its vital to chose the exercises that will recruit and activate the most muscle. Greater activation of muscle during functional lifts like the squat ensure faster, better results in strength and leg shape over time.

When training legs, the regular free weight squat is superior for recruiting and activating more muscle than the Smith machine squat.

Barbell squats are a difficult exercise to perfect. For great results and injury-free training, it’s crucial to learn the proper biomechanics and technique of this exercise. See the fantastic MP instructional video on this exercise. Plus, I recommend utilizing a Certified Trainer to help perfect your technique. Also, make sure to have a spotter when utilizing heavy loads.

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1. Haff G. Roundtable discussion: Machines versus free weights. Strength and Conditioning Journal 2000;22:18-30.
2. Schwanbeck S, Chilibeck PD, Binsted G. A comparison of free weight squat to Smith machine squat using electromyography. J Strength Cond Res 2009;23:2588-91.
3. Kamen G. Electromyographic Kinesiology. . In: Robertson Dea, ed. Research Methods in Biomechanics. Champaign, IL: Human Kinetics; 2004.
4. Cotterman ML, Darby LA, Skelly WA. Comparison of muscle force production using the Smith machine and free weights for bench press and squat exercises. J Strength Cond Res 2005;19:169-76.

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