Effects of Training With Free Weights Versus Machines on Muscle Mass

Are Weights Better than Machines?

Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.


Fitness professionals frequently compare free weight exercises to machine exercises. However, this distinction should not be drawn in black-and-white terms.

While barbell back squats activate more muscles than Smith machine squats, that doesn't automatically mean one is superior to another. Furthermore, some machines featuring "cam" pulley systems allow users to choose resistance levels that more closely mirror strength curves.


Strength training enthusiasts often believe that using free weights rather than machines will produce greater muscle growth. This belief stems from their more difficult nature requiring users to balance themselves while shifting a heavy load; consequently these exercises stimulate more muscle growth as the body releases more testosterone necessary for muscle expansion and development. Unfortunately, though this approach might leave users more sore afterwards!

However, when looking at research more closely this is not true. Studies that compare free weights and machines have revealed similar increases in muscle mass and thickness gains between both groups; additionally both experience an increase in protein synthesis process as well as muscle glycogen levels.

Reasons may include free weights' greater potential to induce muscle damage and fatigue than machines, making them better at stimulating the mTOR pathway. Machines, however, offer benefits by maintaining consistent mechanical tension during movements which helps minimize stress on muscles resulting in less fatigued muscle groups - making it ideal for beginners or those wanting to minimize injury risks.

Machines offer another advantage of working out with machines: isolating specific muscles for more targeted and controlled workouts. For example, using a leg extension machine enables you to isolate just your quad, making targeting that muscle group much simpler without worrying about other parts of the leg or knee joint as much.

Machines also tend to be safer for beginners or people recovering from injuries who cannot use free weights safely, making machines an attractive alternative. Working out on machines may also simply feel more comfortable for some individuals than free weight exercises; especially if they struggle to keep upright posture while performing free weight exercises.

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Muscle Size

At any gym, most people can be seen clustered around machines such as the pec deck and lateral raise machine. Meanwhile, others prefer free weights like barbells, dumbbells and squat racks which they claim provide more muscle-building benefits than machines.

Although compound movements (exercises that involve multiple muscles at once) will engage more muscles at once, including those necessary for stabilization and support joints, weight machines can still help you build bigger muscles depending on which exercise you choose. Many weight machines target one or two specific muscles at once so you can concentrate on growing those targeted muscle(s). Furthermore, certain machine exercises allow for direct training of one muscle at a time without using nearby joints, potentially helping prevent joint pain in the process.

Free weights also engage more stabilizer muscles than weight machines, helping you strengthen your core, back, and legs while training the target muscles. This not only makes strength training more effective at building muscle mass but can help avoid injuries while improving performance in other athletic endeavors. Many find more enjoyment and motivation in strength training with free weights rather than machines.

Free weights have the advantage of providing more personalized resistance levels throughout your workout, helping to provide you with a comprehensive workout in less time - saving valuable gym time in the process! This flexibility also provides greater efficiency for workouts at home versus machines in terms of time savings and effectiveness.

Ideally, to maximize the results of your workouts and make significant gains in muscle, most of your training should focus on free weights; however, that doesn't preclude including some machine exercises in your routine.

Study results published in "Journal of Strength and Conditioning Research" indicate that both groups gained muscle. Testosterone was increased moreso by using free wieghts but it made no difference between the two grpups when it came to buildning muscle mass.

Researchers concluded this indicates that using both forms of training simultaneously or individually is optimal approach to building muscle mass.

Lean Tissue

Virtually any group of experienced weight lifters will swear that free weights are superior to machines in terms of muscle activation and stimulating growth. A barbell back squat, for instance, recruits more quads, hamstrings, glutes and calves than does its Smith machine counterpart squat.

Free weights offer several distinct advantages over machines in terms of training multiple muscle groups simultaneously. Machines only focus on working the targeted muscle, leaving other muscles out to stabilize its movement pattern uninvolved.

This may not be an issue if your goal is merely strength building, but could become problematic if you want to build maximum muscle and develop excellent movement pattern coordination.

Exercise using free weights helps stimulate localized muscle growth by increasing lactic acid accumulation within working muscles and stimulating protein synthesis, as well as mitigating central nervous system (CNS) fatigue which may limit hypertrophy.

Studies on novice weight trainers using either free weights or machines revealed similar increases in muscle size and strength gains, suggesting it does not matter which you use to begin their weight training journey.

If you're new to weight lifting, however, the choice between free weights or machines doesn't really matter; both approaches provide similar results.

However, if you want to develop muscle quickly and efficiently, free weights should form the bulk of your workouts. Free weights will help increase total strength faster while providing greater balance, movement pattern coordination and core stability benefits than machines can.

Though machine exercises should be part of any routine, especially if targeting muscle groups such as calves that can be challenging to train with free weights.

For example, using a seated calf machine is much more convenient than lying on the floor with heavy barbell across thighs. Free weight training remains key if combined with some machine exercises for targeted lower leg training from different angles.

One such research paper revealed that 24 weeks of training with either seated machine-based program or standing free weight-based program resulted in similar increases in lean muscle mass gains. If unfamiliar with proper technique for each exercise, injuries could occur and results might not materialize as expected.

Studies have indicated that free weights may be better at stimulating the mTOR pathway than machines. The mTOR pathway is responsible for growth-promoting hormone production as well as muscle damage stimulation leading to protein synthesis.

Free weights also offer several other advantages over machines: compound movements targeting multiple muscle groups at once as well as single joint, isolation exercises.

Additionally, machine exercises may be challenging for beginners or those with poor posture as they strain joints and back muscles. If you plan to use one of these machines, ensure you hire a trainer who can demonstrate how best to use it to avoid injuries.

Machine exercises may limit range of motion and cause muscle imbalances due to being predetermined. This can be problematic as many effective muscle-building movements include high reps and eccentric contractions that require you to control weight movement through its full range.

When this control is compromised, muscles fatigue more quickly and it won't be possible for you to complete as many reps.


While fitness 'experts' often pit free weights against machines, there's no clear-cut winner between the two forms of equipment; both options may prove effective depending on your goals and muscle-targeting efforts.

Machines provide you with the opportunity to isolate a muscle group and focus on just movement, while free weights require you to also take into account stabilization, which may be more challenging. Therefore, machines have greater applicability for daily life activities such as carrying furniture or playing sports than free weights do.

However, machine exercises may fail to address large muscle groups (such as abs, obliques and spinal erectors ) or lead to improper form that increases damage. Also, swinging motion machines can create momentum that drives loads forward; making them inappropriate for beginners.

Use of free weights requires great balance and takes practice to master. For some people this can be intimidating and limit workouts which could reduce muscle gains.

Machines also offer another advantage by accommodating body biomechanics, providing greater resistance during weak points (e.g. the midpoint of a bench press). This can help minimize muscle damage while creating an optimal training effect. 

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