"Don't squat in the Smith machine" is one of the most repeated pieces of gym advice. So is the reply that it is perfectly good for building legs. Both claims can be tested, and several studies have done so.

How the two squats differ

Free-weight barbell squat Smith machine squat
Bar path Free, set by the lifter Guided by rails, vertical or at a slight angle depending on the model
Balance The bar must be balanced forwards, backwards and side to side The rails handle balance; you move the bar up and down
Foot position Feet under the bar Feet can be placed under or in front of the bar
Bar weight Usually a 20 kg Olympic bar Varies by model; often lighter, and some are counterbalanced
Stopping safely Needs a rack with safety arms, or spotters Hooks and safety stops along the rails

Bar paths vary between models. Life Fitness lists a 7-degree bar angle for its Signature Series Smith machine, for example, while Matrix describes a 90-degree path on its Magnum Smith machine. Bar weights vary too, from 7 kg to 13.6 kg on the machines we list in How much does a leg press weigh without plates?.

Is it harder to squat on a Smith machine?

Usually it is easier to lift more. In a study of 16 men and 16 women who were tested for one-repetition maximums on both, the squat maximum was greater on the Smith machine than with free weights, although the difference was significant for the women only. The bench press went the other way, with greater maximums using free weights (Cotterman et al., 2005).

There are good reasons for this. The rails take over balance, you can place your feet where you are strongest, and the bar itself may be lighter or counterbalanced. Because Smith machines differ so much, a Smith squat number only compares with other numbers on the same machine.

What muscle activity studies show

  • In a small study of six people, each squatting their own eight-repetition maximum, muscle activity was higher in the free-weight squat for the gastrocnemius (34%), biceps femoris (26%) and vastus medialis (49%), and 43% higher on average across all muscles measured. Activity in the vastus lateralis and in the lower back and abdominal muscles measured did not differ significantly (Schwanbeck et al., 2009).
  • A review of squat EMG research concluded that the free barbell squat produces higher overall muscle activity than squats in a Smith machine, the leg press or the leg extension (Clark et al., 2012).

EMG measures how strongly muscles are activated during a set. It does not measure growth, and the training studies below give a more direct answer about results.

What training studies show

  • Similar leg growth. In 59 young men with strength-training experience, groups trained the squat for about six weeks on a Smith machine, with free weights or with free weights on wobble boards. Vastus lateralis thickness increased by 6.3%, 3.8% and 4.4% respectively, and the differences between training groups were not significant (Saeterbakken et al., 2019).
  • Strength stayed specific. In the same study, the Smith machine group improved more on the Smith squat than on the free-weight squat (Saeterbakken et al., 2019).
  • The same pattern with free weights vs Smith machine. When active young adults trained the squat for eight weeks with free weights or on a Smith machine, each group improved more when tested on its own equipment, and vastus lateralis size increased similarly in both (Marcos-Frutos et al., 2025).
  • Pooled evidence. Across 13 studies comparing free-weight and machine training, muscle growth did not differ, while strength gains were specific to the training equipment (Haugen et al., 2023).

So the Smith machine builds the legs about as well as the barbell squat over the periods studied. If your goal is a bigger free-weight squat, though, you need to practise the free-weight squat.

Foot position and where the work goes

Because the bar is guided, a Smith machine lets you place your feet in front of the bar, something you cannot do with a free bar. That changes how the work is shared between the knees and hips.

A study of free-barbell squats shows the principle. When a barrier stopped the knees from travelling forward past the toes, knee torque fell but hip torque rose substantially, and the trunk and shins leaned further forward. The authors concluded that appropriate joint loading may require the knees to move slightly past the toes (Fry et al., 2003).

Applied to the Smith machine, feet placed further forward keep the shins more upright and shift work towards the hips, while feet placed under the bar let the knees travel forward and put more demand on the quadriceps. No Smith machine study we have seen tested this directly, so treat it as a principle and choose the stance that feels strong and comfortable for you.

When to use each

Situation Better choice
You want a bigger barbell squat, for sport or competition The barbell squat, because strength is specific
You want bigger legs Either; many lifters use both, or add a hack squat or leg press
You train alone and want to push close to failure The Smith machine, or a barbell squat in a rack with safety arms set
You want less balance demand, for example when fatigued or returning to training The Smith machine
You want to bias the quadriceps or the hips The Smith machine, with the feet under or in front of the bar

Two cautions apply. A guided bar is not automatically safe: the rails fix the bar's path, so set your feet and the bar so that the path suits your body, and set the safety stops just below your lowest position. And because Smith machines differ in bar weight, angle and counterbalance, keep your training records machine by machine. If you are equipping a gym, our commercial gym equipment list shows where racks and Smith machines fit on the floor.

For more leg options, we compare the hack squat and leg press, and our hypertrophy guide explains how to count squat variations in your weekly sets.

The bottom line

For building leg muscle, the Smith machine squat is a legitimate exercise that works about as well as the barbell squat in the studies available. The barbell squat demands more balance and more stabilising work and is the one to practise for free-weight strength. Choose by your goal, your supervision and your comfort, and record your numbers on the same machine.

References

  1. Clark DR, Lambert MI, Hunter AM. Muscle activation in the loaded free barbell squat: a brief review. J Strength Cond Res. 2012;26(4):1169–1178. doi:10.1519/JSC.0b013e31822d533d
  2. 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(1):169–176.
  3. Fry A, Smith C, Schilling B. Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res. 2003;17(4):629–633. doi:10.1519/00124278-200311000-00001
  4. Haugen ME, Vårvik FT, Larsen S, Haugen AS, van den Tillaar R, Bjørnsen T. Effect of free-weight vs. machine-based strength training on maximal strength, hypertrophy and jump performance: a systematic review and meta-analysis. BMC Sports Sci Med Rehabil. 2023;15(1):103. doi:10.1186/s13102-023-00713-4
  5. Marcos-Frutos D, Miras-Moreno S, Márquez G, García-Ramos A. Comparative effects of the free weights and Smith machine squat and bench press: the important role of specificity for strength adaptations. Int J Sports Physiol Perform. 2025;20(2):292–300. doi:10.1123/ijspp.2024-0274
  6. Saeterbakken AH, Olsen A, Behm DG, Bardstu HB, Andersen V. The short- and long-term effects of resistance training with different stability requirements. PLoS One. 2019;14(4):e0214302. doi:10.1371/journal.pone.0214302
  7. Schwanbeck S, Chilibeck PD, Binsted G. A comparison of free weight squat to Smith machine squat using electromyography. J Strength Cond Res. 2009;23(9):2588–2591. doi:10.1519/JSC.0b013e3181b1b181
  8. Life Fitness. Signature Series Smith Machine (SSM), product specifications, checked October 2026. lifefitness.com
  9. Matrix Magnum Smith Machine (MG-PL62), product page, checked October 2026. johnsonfitness.com

Further reading

This article is general information about training and equipment. It is not medical advice. Speak to a qualified professional before starting a new exercise programme, particularly if you have an injury, a health condition or have been inactive.