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Smith machines are a relatively well-known piece of fitness equipment. How does it compare to doing exercises with free weights?
A smith machine is a steel construction where a barbell can go up and down in a fixed trajectory. Additionally, you can rack this barbell at different heights by turning the bar. Free weights are basically any weight that can move freely.
For most people in most situations, exercises with free weights will be a better choice than using a smith machine. They train more muscles/muscle fibers, balance, allow more variety, etc. These things will be helpful for most fitness goals.
That being said, using a smith machine can also make sense in a few cases.
The main ones are temporarily doing smith machine squats to gain initial confidence in this exercise, in certain recovery situations, and doing calf raises if this exercise is not available in machine form.
Additionally, you may have a personal preference for the smith machine. In this last case, you likely still want to switch it up with the free weight variations of the exercises.
Quick overview smith machine vs free weights
Free weights are a big category of fitness equipment options but there are still some general differences between these and the smith machine. Some of the most important ones include:
- For most people in most situations, free weights will be the better choice.
- Smith machines require and train balance less.
- Free weights train balancing muscles more. This is often an advantage but in certain specific situations this could be a downside.
- It is generally easier to create muscle imbalances on a smith machine.
- When you do an exercise with the same weight in smith machine form vs free weights form, the free weights variation will typically be harder.
- Smith machine can initially help you gain confidence in doing back squats without a spotter.
- Something like a barbell + squat rack is generally cheaper than a smith machine. On the other hand, dumbbell sets can sometimes be more expensive than both of these.
To repeat the first difference, most people will benefit more from free weights in most situations.
With both smith machines and free weights, you can work most of the important big muscle groups. Free weights, especially one-handed options like dumbbells, tend to be more convenient for certain muscles but both can work.
That being said, “working muscles” can be done in different ways. The smith machine will do this differently than free weights.
Muscles are made up of many smaller parts including muscle fascicles which are in turn made up of other smaller parts which includes muscle fibers.
When you move a weight with a muscle all of these smaller parts work together to do the movement. However, what muscles and muscle fibers you engage in what ratios can vary.
A smith machine and barbell squat work the same big muscles/muscle groups (glutes, quadriceps, calves, hamstrings, etc.) but on a smaller scale, the barbell squat will work more different muscle fibers due to the extra balancing, adjusting, and slightly varying upward angle.
Additionally, balancing can also just engage other big muscle groups more. For example, one study measured that smith machine bench presses engage the medial deltoid less than free weight bench presses (1).
Lastly, a different study compared the muscle activation in smith machine squats and barbell back squats with weights they could lift 8 times (so different weights for each exercise).
They measure that the barbell back squats caused 34% more EMG activity in the gastrocnemius (calf muscle), 26% more in the biceps femoris (hamstring muscle), and 49% more in the vastus medialis (quadriceps muscle) without significant differences in other muscles (2).
In short, the smith machine and free weight counterparts can work the same big muscle groups. Even so, free weights tend to work more different muscles and muscle fibers at the same time.
For some situations, this more focused aspect of the smith machine can be a benefit. However, most people will benefit the most from the way free weights engage their muscles.
Potential muscle imbalances
Muscle imbalances are when certain muscles are stronger than other muscles.
This can mean that your left biceps are a lot stronger than your right biceps but also that your quadriceps are overdeveloped compared to your hamstrings.
Both types of muscle imbalances can increase your injury risk and look off from an aesthetic standpoint.
It is typically easier to create and harder to resolve muscle imbalances with the smith machine. For example, if you push more with one leg than the other in a smith machine squat, you can still raise the bar relatively easily.
This is also possible in a barbell squat but to a lesser extent since that would cause you to tip the free-weight barbell one way and lose balance.
Next, one-handed free weights like dumbbells are often great for strengthening and growing the muscles on one side more than the other.
Lastly, smith machines allow you to do compound exercises in ways where you strengthen muscles in a different ratio than doing the same movement with free weights or in your daily life. This can increase your injury risk.
Range of motion
For the most part, human bodies are made of the same components. However, the length and ratios of these components can vary.
As an example, the length of the thigh bone/femur (bone of the upper leg) can vary. Both between individuals and in relation to the length of other bones.
This makes it so the optimal upward motion during exercises like a back squat can vary between individuals.
An issue of a smith machine is that it does not take these personal differences into account. The bar just goes straight up and down no matter who is using the machine.
This can make it so you don’t go through full range of motions during certain exercises. For optimal muscle growth and strengthening this is generally recommended.
Additionally, you can again train muscles in a ratio that is not optimal for you personally.
Balance requirements and training
Balance and coordination are skills that you can train by doing activities that are challenging in these areas.
When it comes to balance skill requirements and training, free weights are generally more challenging but also train this more than smith machines.
For resistance training beginners this extra help could be useful for a few repetitions to get used to the technique of the exercise. That being said, even these individuals will likely benefit from moving on to free weights fast.
One example of an exception exercise is weighted calf raises if you don’t have a specific machine available. Doing this exercise with free weights makes it really hard to focus on growing and strengthening your calves due to the balance requirements.
Need for spotter
Besides the fixed trajectory of the barbell, another distinct feature of the smith machine is the ability to rack the bar at different heights.
The bar of a smith machine has a hook on each side and the smith machine has small bars at different heights for these hooks. By turning the smith machine bar you can rack it at these different heights.
This is mostly relevant for doing back squats if you don’t have safety bars and/or a spotter available. For exercises like the bench press, you could also use dumbbells up to a certain weight if you don’t have a spotter.
Something to keep in mind is that this hook system is not completely mistake-proof. Always be careful during your workouts, both when using a smith machine and its alternatives.
Which one is harder?
All of the differences above can make you wonder whether this makes free weights exercises harder than their smith machine counterparts.
One study investigated the differences in 1 repetition maximum (1RM) weight between regular vs smith machine squats and regular vs smith machine bench presses.
They measured that the smith machine squat 1RM was higher than the free weight squat (so free weights were “harder”) (3).
On the other hand, they measured that the 1RM weight for the free weight bench press was higher than the smith machine bench press 1 RM (so free weights were “easier”).
One downside of this study is that they don’t mention the experience level of the lifters. Differences in technique skill levels could play a role.
In short, one study implies that whether free weights or the smith machine are harder, depends on the specific exercise. The study suggests free weight squats are harder but free weight bench presses are easier than the smith machine versions.
Lastly, you may be considering getting either a smith machine or free weights for your home gym. In that case, how much these options cost matters.
A barbell with a squat rack is typically slightly cheaper than a smith machine. In turn, both options are typically cheaper than a complete dumbbell set.
Something to keep in mind when looking at the prices of both barbells and smith machines is that you often have to order weight plates separately at an extra cost.