Training with free weights or machines? That is the question here

Claudio Viecelli

28-5-2025

Translation: machine translated

Weight bench and free weights or machines with guided movements? How do you train more effectively and healthily? What can lead to heated discussions in gyms, I want to take a sober and scientific look at here.

The question of whether training with free weights or machine-based training is more effective has been around as long as strength equipment. The answers from trainers, athletes and sports enthusiasts are as varied as April weather. I try to look at the topic systematically and develop an understanding of the question and how to answer it.

In this article, free weights refer to dumbbells and barbells that have any mass. Machines are defined as devices that (usually) have a weight block and a pin for selecting the training resistance. In most cases, exercises on weight machines are performed in a fixed plane of motion, whereas with free weights this is more flexible and involves greater variation in the lever arm.

Where is the greater risk of injury?

Let's first look at the risk of injury. The American College of Sports Medicine argues that the demands on technique are lower with machine-based training and therefore the risk of injury is also lower [1].

Kerr and his research team examined exercise-associated injuries in people who visited an emergency department in the USA between 1990 and 2007 [2]. Approximately 970,801 accidents were reported during this period. The average age of the patients was 27.6 years (age range: 6 - 100 years), 82.3% of whom were men. At 25.3%, the upper body was the most injured body region, followed by the lower body with 19.7% of cases.

The researchers also analysed the frequency of injuries by training equipment. Free weights accounted for the largest proportion of injuries at 90.4%. 33.6% were hand injuries, followed by 33.5% foot injuries. At 65.5%, the injuries mainly resulted from dropping the weights and the associated injuries. 10.4% of the injuries resulted from body parts becoming trapped between the weights, 9.8% were self-inflicted injuries, 7.9% were overload injuries, 3.3% were falls and 3.1% resulted from lifting/pulling injuries. The actual execution of the exercise therefore did not contribute to the risk of injury, but rather the dropping of weights.

Whether free weights are really more dangerous in the execution of the exercise can at least be questioned. I am not aware of any longitudinal studies that have investigated a causal relationship between the risk of injury when performing an exercise with free weights or machine-based exercises. I therefore doubt that there really is a difference in the risk of injury.

Advantages and disadvantages of free weights

One of the biggest advantages of free weights such as dumbbells or barbells is obvious and that is the cost factor. As dumbbells can be used for a wide range of exercises, they are much more cost-effective than strength equipment, which is usually limited to one or a few muscle groups. Another point is that dumbbells have no limitations in terms of body proportions and can therefore cover the entire spectrum of body sizes, leg and arm lengths, etc. They are also indispensable in certain sports such as powerlifting or Olympic-style weightlifting and cannot be replaced by machines due to their specificity.

The force caused by gravity means that dumbbells can only generate resistance in the vertical plane, i.e. perpendicular to the earth. Therefore, free weights can only create resistance to the movement of the body in this direction. This must be taken into account when positioning the body to perform an exercise. Certain exercises such as leg extensions, leg curls and/or rotational movements of the upper body are therefore difficult to perform with free weights.

Advantages and disadvantages of strength equipment

Strength machines are widely accepted and are less daunting, especially for older people, compared to free weights. As mentioned above, they allow you to train practically all muscle groups

The cost factor can be seen as a disadvantage. Whether machines also require more space than a weight set and the associated weight benches and/or weight plates can be discussed. Also worth mentioning is the fact that strength equipment uses an eccentric to depict a strength curve that does not necessarily correspond to the physiological strength curve [3].

Muscular considerations

A characteristic of the musculature is that it can generate force. Where the externally imposed resistance comes from, from free weights or from a weight machine, is irrelevant.

Strength training with free weights requires greater muscle coordination, as the instability of the free weights must be compensated for [4]. In muscles that work together to perform a joint movement, higher electrical activity was observed in the muscle compared to machine-based training [5,6]. The same observation was made by a research team led by Schwanbeck [7], who investigated the electrical activity in the leg muscles during squats on the barbell compared to squats on the Smith machine. Does this higher myoelectric activity also result in greater muscle growth?

The answer is no, or rather the question cannot be answered unequivocally. This is mainly due to the fact that there are no long-term studies showing a causal relationship between myoelectric activity and hypertrophy and the interpretation and conclusions of surface electromyography measurements [8,9]. The greater myoelectric activity may also be due to the greater demand on the stabilisation of the dumbbells [6,10].

Let's talk about stabilisation and make the following assumptions: Let the mass to be moved for an exercise be identical. Once it is represented by dumbbells and once by a machine. Which exercise is most likely to involve more mechanical work? In the machine-based exercise [7,11]. The body prioritises stability over strength development [12,13]. This means that high demands on stabilisation during a strength training exercise have a negative effect on strength. Put simply, the body needs more energy for a stable posture than for the actual exercise. If the stability is provided by the machine, it can invest all its strength in the exercise.

What now? Free weights or machines?

Strength training - with free weights or machines - leads to an increase in strength and muscle mass. Now the arguments of the advocates of free weights are already echoing in my head. They argue that training with free weights is much more functional and has a greater carry-over into everyday life. In some cases, the aversion to equipment goes so far that it is explicitly discouraged.

To develop an understanding, let's look at the knee joint. This can be flexed or extended. The quadriceps femoris muscle (the anterior thigh muscle) is responsible for extending the knee joint. It is formed by four muscle heads. It is connected to the patella via the patellar tendons. This in turn is connected to the tibia, i.e. the lower leg bone, via the patellar ligament. The tensile force caused by the contraction of the quadriceps femoris muscle, which acts on the patella, stretches the leg. The function of this muscle is therefore to stretch the leg.

The quadriceps femoris muscle can be specifically trained on the leg extension machine. Why should this targeted training be non-functional? Due to the volume work performed by the muscles, the increase in muscle cross-section is also accompanied by an increase in strength. Even if this is not in a 1:1 ratio [14,15]. If strength training now increases strength and muscle mass and thus provides articles for the corresponding function, i.e. stretching the leg, surely this must also manifest itself in everyday functions?

Studies show the same efficiency

In older people, the strength in the legs is measured using the so-called chair stand test or sit-to-stand test. For this test, people are asked to stand up from a chair as quickly as possible without using their arms. The time is measured. This was analysed in a study with senior citizens over the age of 65 at [16] . The study included 17 people aged between 65 and 75 and 12 people aged over 85. They completed 12 weeks of whole-body strength training. The legs were trained on the leg press and leg extension. This was done three times a week. The machine-based strength training in both groups resulted in a highly significant (P < 0.001) decrease in the time it took people to get up from a chair. This was due to the increase in strength in both age groups with no significant difference between the groups (P > 0.05).

In the comparison between free weights and conventional equipment, a research team from Spain only varied the execution, i.e. with free weights or machine-based [17]. The remaining training descriptors were identical between the modalities. Strength, muscle growth and joint pain were measured in 38 trained men over a period of 8 weeks. They trained three times a week. Both groups significantly increased their strength (P < 0.001) with no differences between the groups (P > 0.216). The same result was reflected in hypertrophy with no significant difference between the groups (P > 0.05). There were also no significant differences between the groups in terms of joint pain (P > 0.144). Training with free weights or with machines was therefore equally effective. The same conclusion was reached in a recently published systematic review and meta-analysis [18].

Conclusion

Both forms or modalities of training increase strength and muscle mass and are equally effective. The choice of modality therefore depends on personal preferences or training goals. Training on unstable surfaces makes sense for athletes of several sports. A combination of both forms of training is therefore also effective. The argument that one form of training is superior to another must be invalidated by the fact that the muscle does not know the origin of the externally applied force. The only thing the muscle wants is to generate torque. If demands are placed on stabilisation, these are at the expense of strength development.

It should also be emphasised once again that older people benefit greatly from (machine-based) strength training. As it is easier in terms of coordination, training with machines can make it easier for seniors to start strength training.

References

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16. Verdijk LB, Van Loon L, Meijer K, Savelberg HHCM. One-repetition maximum strength test represents a valid means to assess leg strength in vivo in humans. https://doi.org/101080/02640410802428089. Routledge ; 2009;27: 59-68. doi:10.1080/02640410802428089

17. Marzuca-Nassr GN, Alegría-Molina A, SanMartín-Calísto Y, Artigas-Arias M, Huard N, Sapunar J, et al. Muscle Mass and Strength Gains Following Resistance Exercise Training in Older Adults 65-75 Years and Older Adults Above 85 Years. Int J Sport Nutr Exerc Metab. Human Kinetics; 2023;1: 1-9. doi:10.1123/IJSNEM.2023-0087
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Claudio Viecelli

Biologe

claudio.viecelli@keyoniq.com

Molecular and Muscular Biologist. Researcher at ETH Zurich. Strength athlete.

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