Free weights vs machines for building muscle explained
Opinions differ regarding if free weights or machines are better for improving strength and/or muscle mass. We explain the differences and how to decide what is right for you

Free weights versus machines for building muscle and improving strength

Which is better?

Our gym in Taren Point receives emails, phone calls and visits every day from people who are keen to get more serious about training, improving their strength and building muscle. So one of the most common questions I get asked relates to the use of machines versus free weights in terms of what might be “better” or more efficient to achieve specific goals.

Like a lot of things relating to the human body, opinions differ regarding if free weights or machines are better for improving strength and/or muscle mass. Some say free weights like squats and other compound lifts are best for increasing muscle size. Whereas others may suggest that machines can better isolate muscles and are optimal for growth.

For improving strength, free weights are generally suggested to be best. Likewise, if you want to get better at power-lifting, it’s sometimes suggested to do the power-lifts themselves (squat, bench press and deadlift) and not waste time using machines. 

So, who is right? Well we’ve written this guide using current literature & evidence available on free weights versus machines for increasing muscle mass and strength. This is an example of our ethos & the depth we go to for any member of our gym to ensure that whatever you are doing in your training be it for strength, to powerlift or even conditioning that it makes sense & will yield results.

Free weights versus machines for improving strength

 

If someone wants to get stronger, are they best using free weights or machines? The question will depend on what strength means to the individual. For example, strength might mean for someone in being stronger during day-to-day life activities. Whereas to someone else, strength may relate to the maximum weight they can lift for one repetition.

Some research has been done comparing the two training modalities on strength improvements. Heidel et al., 2022 conducted a meta-analysis to measure how strength was affected by free weights and machines [1]. Results showed strength improvements depended on how strength was tested. Individuals who used free weights achieved greater strength gains in free weight strength than those who used machines. Those who used machine-based training made greater strength improvements on machines than those who used free weights. Strength improvements did not vary between free weights and machines on an unfamiliar task. For example, testing leg extension, despite groups not specifically training for this.

However, this does not mean that machine exercises cannot make someone stronger at free weights, and vice versa. Rossi Et al., 2018 had subjects perform leg press only, barbell squats only, or a combination of leg pressing and squats, 2 times per week for 10 weeks. Squat strength increased by 76.2% in the squat only group, 53.9% in the squat + leg press group, and 21.1% in the leg press only group. Leg press strength improved in all 3 groups, with no significant differences between groups [2].  

The lack of difference in leg press strength between groups could have potentially been because of the range of motion the knee joints went through. During the leg press, the knee joint only went through 90 degrees of knee flexion, whereas in the squat, the knees went through 120 degrees of flexion. Squats may have been just as effective for increasing leg press strength as the ROM the knees went through covered the ROM the knees experienced during leg pressing. Other factors may have come into play with the lack of difference in leg press strength between groups. But it is not clear why these findings differed from the meta-analysis.

Does being hyper-specific improve strength gains better to using exercise variety?

 

Since strength improvements generally increase the most on the specific exercise being performed, for example, if you want to get stronger at barbell squats, then barbell squatting will get you stronger at this exercise. Does this mean we only need to train the specific exercise we want to get stronger at? Or should we use a range of exercises to maximise strength on a specific exercise? 

Fonseca Et al., 2014 tested this question. I’m going to summarise the study briefly as the full results are not relevant for this post. One group of subjects smith machine squatted twice a week (constant group) for 12 weeks, versus a group which performed smith machine squats, leg press, lunges and dead-lifts (varied group). Total volume was equated between groups. In the constant group, all the volume was allocated to squats. In the varied group, squat volume was approx. 52-57% less than the constant group as the remaining volume was allocated to other exercises. The varied group increased smith machine squat 1RM more compared to the constant group, even with performing less than half of the squatting volume [3].   

The reasons to why using a variety of exercises being better for increasing 1RM strength is unclear. The authors speculated that exercise variety optimised neural drive to the muscles (the electrical stimulation from the spinal cord to the muscles to make them contract), which improved strength. This research suggests that being hyper specific and doing a single exercise (for example, only squat, bench press and dead-lift) with no exercise variations or accessories may not be optimal for increasing 1RM strength, compared to using a variety of exercises [3].  

Free weights versus machines for improving muscle size (hypertrophy)

 

In the meta-analysis by Heidel et al., 2022, their results found that gains in muscle size were the same between subjects who performed machines only or free weights only. This suggesting that equal amounts of whole-body muscle can be made using either free weights or machines [1]. The lack of differences between groups may be because the muscles were exposed to the same relative amount of effort (proximity to failure). Therefore, the muscles experiencing a comparable stimulus for muscle growth from both training modalities due to similar amounts of mechanical stress.

However, there are some caveats to consider. Increases in muscle size do not appear to be uniform across all muscle heads and regions of a muscle [4]. For example, Zabaleta-Korta Et al., 2021 had subjects perform 5 weeks of smith machine squats or leg extensions, three times per week, using 4 sets of 12 repetitions to failure. Results showed the rectus femoris only grew in the leg extension group but did not reach statistical significance in the smith machine squat group. Additionally, only the central region of the vastus lateralis grew in the smith machine squat group [5].  

Likewise, Costa Et al., 2021 had two groups of subjects to perform 9 weeks of resistance training with either using the same exercises for each muscle group, three times a week or using a variety of exercises for each muscle group each session (Table 1). Muscle thickness of the proximal (closet part of muscle from the body), middle and distal (farthest part of the muscle from the body) of the lateral and anterior thigh, elbow flexor and extensor muscles were measured via ultrasound. In the variety group, all the measured sites of each muscle grew. In the non-varied, all the muscle sites grew except for the middle of the lateral thigh and the proximal end of the elbow flexors [6]. Thus, it appears the non-varied group did not provide enough stimulus to the areas of the muscles which did not grow. Whereas the varied group was able to stimulate all of their muscles.   

Although whole body muscle growth does not appear to be different between free weight and machines, it’s likely that free weights and machines place differing amounts of tension across the heads and areas of muscles. As a result, using machines with free weights is likely ideal to promote even muscle growth across all areas of muscles.  

Muscle mass may be associated with strength gains

 

There is debate to whether increasing muscle size causes increases strength. In theory, it makes sense that adding more muscle (contractile tissue) will allow for more force to be produced per muscle contraction. If this is true, more muscle should equal more strength. However, this is not the case, individuals can get stronger without gaining muscle, and also, can gain muscle without getting stronger [7].  

It is unclear exactly how much gaining muscle contributes to increasing strength, as it is difficult to measure. One issue is that changes in muscle size are not solely contributed to increasing areas of the muscle which contribute to producing force. Non-contractile components within a muscle (parts within a muscle which do not cause a muscle contraction) can hypertrophy and make a muscle visually appear bigger. This is one reason why muscles can get bigger without seeing increases in strength [7].  

However, from a practical standpoint, it has been shown that muscle size is a predictor of strength within power lifters. Ye Et al., 2013 found strong correlations between muscle mass and powerlifting performance in 20 elite male power-lifters [8]. Individuals with more muscle mass had larger powerlifting totals. Similar results were also found by Brechue Et al., 2002 whereby muscle thickness measured via ultrasound on 20 elite power lifters was strongly correlated to squat, bench press and dead-lift strength. The strongest lifters had the thickest muscle measurements [9]. 

Although it is unclear how much muscle size contributes to strength gains, data from power lifters repeatedly show that the strongest lifters generally have more fat-free mass relative to weaker lifters. For this reason, it is likely that increasing muscle size will help improve 1RM strength on the squat, bench press and dead-lift. 

At the current time, I have not found data which compares fatigue accumulation between free weights and machine weights. But for whoever is reading this, at the same relative effort (proximity to failure), I am going to assume on average, more people will agree that a set of 10 repetitions on squats to failure is more fatiguing than doing the same on a leg press. Adding in machine exercises with free weights may be an efficient way to accumulate muscle mass whilst managing fatigue. This may help with improving 1RM strength and power-lifting performance, opposed to solely using free weights. 

Strength training in practical terms

 

Replacing free weights with machines
Strength increases best on the specific exercise being used. However, strength gains can carry over from one exercise modality to another, particularly if both exercises have similar joint actions and range of motions. If you cannot use free weights for a period such as being on holiday or injured, replacing free weight exercises with machines which use similar joint actions and ROMS may be effective for as a minimum, maintaining strength gains, or possibly increasing strength. 

Specific exercises vs variations
If your goal is to increase strength on the squat, bench press and dead-lift, doing these exercises is important for increasing strength specifically on these movements. However, being hyper specific and only doing these exercises with no variations or accessory movements may not be optimal to maximise strength. Adding in some machine work with free weights will probably be better for improving strength gains versus doing the specific exercise on its own.   

Balancing even vs specific muscle growth
Whole body muscle growth appears to be similar between machines and free weighs when total training volume and intensity are matched. Free weights may be limited in fully stimulating all muscle heads and regions of muscles. If your goal is to promote even muscle growth across all muscles and you predominantly only use free weight exercises, you should probably add in some machine work in conjunction. 

Muscle mass is probably additive to improving strength. If you want to maximise strength gains over the long term, you should have periods of training which are focused on increasing muscle size. Machines may carry less fatigue relative to free weights and are less time consuming to perform. Doing some machine exercises is probably efficient for accumulating some easy training volume with less fatigue, opposed to using free weighs alone for muscle gains. The extra muscle mass may carry over to improving 1RM strength. 

References

  1. Heidel, K.A., Z.J. Novak, and S.J. Dankel, Machines and free weight exercises: a systematic review and meta-analysis comparing changes in muscle size, strength, and power. J Sports Med Phys Fitness, 2022. 62(8): p. 1061-1070.
  2. Rossi, F.E., et al., Strength, body composition, and functional outcomes in the squat versus leg press exercises. J Sports Med Phys Fitness, 2018. 58(3): p. 263-270.
  3. Fonseca, R.M., et al., Changes in exercises are more effective than in loading schemes to improve muscle strength. J Strength Cond Res, 2014. 28(11): p. 3085-92.
  4. Zabaleta-Korta, A., E. Fernández-Peña, and J. Santos-Concejero, Regional Hypertrophy, the Inhomogeneous Muscle Growth: A Systematic Review. Strength & Conditioning Journal, 2020. 42(5): p. 94-101.
  5. Zabaleta-Korta, A., et al., The role of exercise selection in regional Muscle Hypertrophy: A randomized controlled trial. J Sports Sci, 2021. 39(20): p. 2298-2304.
  6. Costa, B.D.V., et al., Does Performing Different Resistance Exercises for the Same Muscle Group Induce Non-homogeneous Hypertrophy? Int J Sports Med, 2021. 42(9): p. 803-811.
  7. Schoenfeld, B., et al., Resistance Training Recommendations to Maximize Muscle Hypertrophy in an Athletic Population: Position Stand of the IUSCA. International Journal of Strength and Conditioning, 2021. 1.
  8. Ye, X., et al., Relationship between lifting performance and skeletal muscle mass in elite powerlifters. J Sports Med Phys Fitness, 2013. 53(4): p. 409-14.
  9. Brechue, W.F. and T. Abe, The role of FFM accumulation and skeletal muscle architecture in powerlifting performance. Eur J Appl Physiol, 2002. 86(4): p. 327-36.
Paul Attard
Paul Attard

Paul is the founder and head coach of SPC Performance Lab. Paul has been coaching since 2014 and has worked with all different types of people. From first timers learning the basics, all the way up to the experienced power-lifting competitors.

He tailors his approach depending on the needs, goals and experience of the individual. Paul has extensive theoretical and practical coaching experience.

- Masters of Sports & Exercise Science (Strength & Conditioning)
- Bachelor’s degree in Exercise & Sports Science with First Class Honours
- Competed and won multiple natural body-building shows & power-lifting competitions.
- Held an Australian power-lifting record.

Free advice

SPC Performance Lab is a gym in Taren Point in the Sutherland Shire, Sydney NSW. It is a private gym that offers strength training, powerlifting and body building training. The gym is open 24 hours, 7 days a week with membership options that include casual or regular visits.

Paul also provides a choice of personal training one on one or the option of online coaching.

Share the Post:

More free advice

How to low bar squat for strength training and powerlifting

This article is a complete and detailed guide on how to low-bar squat efficiently. By following the technique points outlined in this article, you can maximise the weight you can squat and minimise injury risk.

VIEW ARTICLE
How to improve your squat depth to achieve a full squat range of motion squat

This article will cover the main variables that affect an individual’s ability to achieve a full-depth squat. The main factors to consider are flexibility and mobility, squat technique and individual anthropometrics. Each of these will be explained in detail along with practical applications for improving your squat depth.

VIEW ARTICLE