Should you use free weights or machines for strength training?

Once upon a time, in a faraway land, there was a village where all the people lifted weights several times a week.

Strong, happy, and healthy, they convened regularly for workouts, and spotted each other while they did free weight squats, bench presses, and many other exercises.

Nearby, there was another village, and the people of that village also lifted weights several times a week. However, in that village lived an inventor, and this inventor had developed machines that could be used for strength training.

Consequently, when the people of this second village convened regularly for workouts, they did machine squats, machine bench presses, and many other exercises. And they too were strong, happy, and healthy.

The rivalry between the two villages was very fierce, and they each criticized the other for using what they believed was totally inappropriate approach to strength training.

“Your movement patterns are unnecessarily constrained,” claimed the strong, happy, and healthy people of the first village. “You are hurting yourselves, and it will catch up with you eventually.”

“It is unnecessarily risky to lift unrestrained weights,” claimed the strong, happy, and healthy people of the second village. “You are risking great hurt to yourselves, and it will catch up with you eventually.”

This debate went on for many years, and nothing noteworthy happened, except that the people in both villages continued to be strong, healthy, and happy (except when they were debating the benefits of training with free weights vs. machines, when they became stressed and unhappy).

Eventually, a young man from the first village fell in love with a woman in the second village. He visited her in secret, but while he was traveling to see her, he could not help noticing the strong, healthy, and happy villagers of the second village as they used machines to do strength training.

After a while, he realized that there was nothing wrong with using machines to do strength training. And so one day, he stood up in the first village, in the place where they lifted weights, and explained to everyone that they were wrong, and that both free weights and machines could be used to help people become strong, healthy, and happy.

Angry, the people of the first village seized him, beat him, and cast him out.

Saddened, he picked himself up, brushed himself down, and limped away. Many years later, he founded a third village in that area, where everyone convened regularly for workouts. And they did both free weight and machine squats, free weight and machine bench presses, and many other exercises, according to what they felt like doing on the day.

And they were all strong, happy, and healthy, and they never became stressed by arguing about which type of exercise was best.


What is the point of this story?

From a behavioral perspective, the moral of the story is, of course, that many people feel lost without having something to argue about, and do not welcome the thought of losing that.

And, from a sports science perspective, the point is that strength training with any type of resistance (whether free weights or machines) can be used to help people become strong, happy, and healthy.

But that does not mean that both types of strength training cause *exactly* the same effects. And this is important to consider, if we are using strength training to help athletes prepare for sports.

For example, if we improve our ability to do squats in a Smith machine, we will not usually improve our ability to do free weight squats by anywhere near as much, even if the movement pattern is *nearly* identical in the two exercises.

This seems to happen because of stability-specific strength gains.


What are stability-specific strength gains?

Strength gains are specific to the type of stability that we use during strength training.

For example, if we do bench presses in a Smith machine, we will improve our Smith machine bench press one repetition maximum (1RM). We will also increase our 1RM free weight barbell bench press, albeit to a lesser extent. And we will also increase our 1RM free weight dumbbell bench press, albeit to an even smaller extent.

Conversely, if we do free weight dumbbell bench presses, we will improve our free weight dumbbell bench press 1RM. We will also increase our free weight barbell bench press 1RM, albeit to a lesser extent. And we will also increase our Smith machine bench press 1RM, albeit to an even smaller extent.

Essentially, there is a spectrum of stability.

If we train with a great deal of stability (the Smith machine bench press), we tend to improve strength under very stable conditions most. If we train with little stability (the dumbbell bench press), we tend to increase strength under less stable conditions most.


Why does this happen?

When we first lift weights under unstable conditions, such as when doing dumbbell bench presses, this causes a lot of involvement from the antagonist (opposing) and synergist (stabilizing) muscles.

Initially, the antagonist (opposing) muscles actually impede our ability to lift a weight, by acting to resist the movement. In contrast, our synergist (stabilizing) muscles help us balance.

After we do dumbbell bench presses for a while, we improve coordination and balance, and this allows us to reduce the involvement of our antagonist (opposing) muscles, while increasing the involvement of our synergist (stabilizing) muscles.

This reduces resistance to movement, and we *express* greater strength, which we perceive as a (very large) strength gain. In the early days of training, the agonist (prime mover) muscle does not really improve its ability to produce force by as much as our improved dumbbell bench press 1RM might suggest, although it does increase to a degree. Only later, once we have learned to coordinate the movement, can we really challenge this working muscle.

Conversely, when we use the Smith machine to do bench presses, there is little involvement from the antagonist (opposing) or synergist (stabilizing) muscles, and so most of the strength gains we observe are from overloading the agonist (prime mover) muscle directly.

This overload of the agonist (prime mover) muscle could lead to gains in maximum force producing ability by various mechanisms, including increases in muscle size, tendon stiffness, ability to transmit force laterally, or voluntary activation.

Naturally, when we come to attempt a free weight bench press 1RM, that strength gain does not transfer as well as we might expect it to, simply because we have not learned to coordinate the antagonist (opposing) and synergist (stabilizing) muscles in the right way.


What is the takeaway?

Strength gains are specific to the type of stability that we use during strength training.

When we train with unstable exercises, we improve coordination and balance, reduce the involvement of our antagonist muscles, reduce their resistance to movement, and thereby *express* greater strength, which we perceive as a (very large) strength gain on the trained exercise (which does not transfer well to more stable exercises).

When we train with unstable exercises, most of the strength gains occur from overloading the agonist muscle directly. This overload of the agonist muscle likely causes gains in maximum force producing ability by various mechanisms, but strength gains will not transfer as well as we might expect to less stable exercises, simply because we have not learned to coordinate the antagonist and synergist muscles.