Geschatte leestijd: 10 minutenHardcore bodybuilders have been swearing by it for years: “Free weights are more effective than training on fitness machines”. A recent study indeed shows that testosterone levels and growth hormone levels rise more after a training session with free weights than after a comparable session using machines. The same applies to cortisol, although this difference appears to be too small to be statistically significant.
The research: Squats increase hormone levels more than leg presses
Yesterday, the summary of a study on this topic was published “ahead of print”, which will soon appear in The Journal of Strength & Conditioning Research (1). However, the full text of this study, written to obtain a master’s degree, was already available (2).
Free weight exercises appear to induce greater hormonal responses to resistance exercise than machine weight exercises utilizing similar lower-body multi-joint movements and primary movers.
A.A. Shaner, University of Texas
The introduction of the study states that no previous research has been conducted on this topic. This is remarkable in itself, given that it is a recurring point of discussion.
The researcher indicates a desire to investigate the different direct effects of resistance training on testosterone, growth hormone, and cortisol, using both free weights and machines.
Study setup
The researchers had 10 trained men perform 6 sets of 10 repetitions of squats and leg presses of comparable intensity. The repetitions were done at an intensity of 80% of their one-repetition maximum (1RM), the maximum weight they could lift for one repetition. This 1RM was determined in two previous sessions for both exercises. There was a week of rest between the different exercises.
Blood values were measured at four different times: immediately before and after the training, 15 and 30 minutes after the training. They measured the levels of testosterone, growth hormone, and cortisol, as well as factors such as heart rate, changes in plasma volume, and fatigue as experienced by the men.
Testosterone, squat vs. leg press
Here are the differences. The researchers observed that, for example, testosterone immediately after squat training had increased by over 31% compared to almost 22% when leg presses were done. This difference decreased over time, and after half an hour, there was no difference.
Growth hormone, squat vs. leg press
For growth hormone, they also observed a greater increase after squats than after leg presses. After squats, the growth hormone level had increased by 4650%. After the leg press, it was “only” 833%. In contrast to testosterone, the difference in growth hormone was still significant after half an hour.
Cortisol, squat vs. leg press
Both growth hormone and testosterone work anabolically, instructing the body to build tissue, including muscles, from available resources, the amino acids in the blood. Cortisol, on the other hand, works catabolically, breaking down muscle tissue to free up these resources for energy. For muscle growth, an optimal cortisol/testosterone ratio means low cortisol and high testosterone (3).
In this regard, the researcher himself refers to various studies showing that cortisol rises immediately after heavy exertion involving large muscle groups (4 through 9) and that there is a positive correlation between the level of exertion and the degree to which cortisol rises (10 through 13).
Therefore, the researcher also examined the effect of squats and leg presses on cortisol. They observed that cortisol increased more after squats than after leg presses, but this difference was not statistically significant (potentially caused by chance).
Criticisms of the study
When I had only read the summary, I had some modest criticisms of the study and the conclusion. However, in the full report, it is clear that the researcher is aware of these issues. The question remains why the study’s design was not changed to address these objections.
Free weights vs. a machine: Squats and leg presses are not comparable
If you want to compare the effect of training with free weights to training with a machine, you should try to find two exercises that are truly comparable.
The conclusion of the researcher does not align, in my opinion, with what he writes himself in the full report (2). In the conclusion, he writes that squats and leg presses are comparable exercises: “utilizing similar lower-body multi-joint movements and primary movers.”
However, this is not the case. Especially the lower back, for example, is much more involved in squats than in leg presses. The researcher does not specifically mention the lower back, but he does refer to research showing that squats involve more muscle mass (14) and that this leads to a higher increase in testosterone (15).
Instead of the leg press, for example, it could have been compared to a “squat machine”, preferably one where the back is not supported so that it can move forward and backward freely as with squats.
Don’t get me wrong. It’s very interesting to know what the difference is between squats and leg presses. There are many people who simply dislike squats because they find it a difficult exercise (barbell on the neck, balance). For them, it is useful to point out the benefits of the squat as demonstrated in these types of studies. However, I think it goes too far to extrapolate the conclusion to the difference between free weights and machines in general.
Interestingly, although it was confirmed that the total load during the squat was greater than during the leg press, the participants in the study did not experience any difference in fatigue after doing both exercises.
Differences per exercise
Additionally, I would have liked to see a comparison between two exercises (free weights and machine) targeting a different, smaller muscle group. As mentioned, testosterone increases more when more muscle mass is involved. Therefore, the difference in hormone effects between free weights and machine training might be much smaller when looking, for example, at the biceps.
But, to be fair, the researcher indicates that his study specifically addresses compound exercises (exercises involving multiple muscle groups) targeting the lower body. He himself does not extend the conclusions to training with free weights and machines in general.
Small sample size
Finally, ten participants are a very small population from which to draw conclusions. Personal differences will have a greater influence, and the likelihood that the chosen individuals are not representative is relatively high.
And what about other studies?
The fact that the researcher says there have been no previous studies on this topic is not true. I found at least one study comparing the effect of squatting with free weights and on a Smith machine on testosterone and cortisol (16). And I am sure that there are more of them.
In general, these studies show that testosterone increases more after squatting with free weights than on a Smith machine, although the difference is not always significant. However, these studies often show no difference in cortisol levels.
In conclusion, the present study does confirm that there is a difference in hormone responses between free weight and machine exercises. However, I think it is not justified to conclude that free weight exercises are more effective for this reason alone. I do believe that free weight exercises are generally more effective than machine exercises. However, this is mainly because they allow more freedom of movement, which is not possible with a machine.
Free weight exercises have other advantages as well, such as working out stabilizing muscles and training balance. There is less difference in hormone effects than this study suggests.
Therefore, the researcher also looked at the effect of squats and leg presses on cortisol. They observed that cortisol did increase more after squats than after leg presses, but that this difference was not statistically significant (potentially caused by chance).
Criticisms of the study
When I had only read the summary, I had some modest criticisms of the study and the conclusion. However, in the full report, it is clear that the researcher is aware of these issues. The question remains why the study’s design was not changed to address these objections.
Free weights vs. a machine: Squats and leg presses are not comparable
If you want to compare the effect of training with free weights to training with a machine, you should try to find two exercises that are truly comparable.
The conclusion of the researcher does not align, in my opinion, with what he writes himself in the full report (2). In the conclusion, he writes that squats and leg presses are comparable exercises: “utilizing similar lower-body multi-joint movements and primary movers.”
However, this is not the case. Especially the lower back, for example, is much more involved in squats than in leg presses. The researcher does not specifically mention the lower back, but he does refer to research showing that squats involve more muscle mass (14) and that this leads to a higher increase in testosterone (15).
Instead of the leg press, for example, it could have been compared to a “squat machine”, preferably one where the back is not supported so that it can move forward and backward freely as with squats.
Don’t get me wrong. It’s very interesting to know what the difference is between squats and leg presses. There are many people who simply dislike squats because they find it a difficult exercise (barbell on the neck, balance). For them, it is useful to point out the benefits of the squat as demonstrated in these types of studies. However, I think it goes too far to extrapolate the conclusion to the difference between free weights and machines in general.
Interestingly, although it was confirmed that the total load during the squat was greater than during the leg press, the participants in the study did not experience any difference in fatigue after doing both exercises.
Differences per exercise
Additionally, I would have liked to see a comparison between two exercises (free weights and machine) targeting a different, smaller muscle group. As mentioned, testosterone increases more when more muscle mass is involved. Therefore, the difference in hormone effects between free weights and machine training might be much smaller when looking, for example, at the biceps.
But, to be fair, the researcher indicates that his study specifically addresses compound exercises (exercises involving multiple muscle groups) targeting the lower body. He himself does not extend the conclusions to training with free weights and machines in general.
Small population
Finally, ten participants are a very small population from which to draw conclusions. Personal differences will have a greater influence, and the likelihood that the chosen individuals are not representative is relatively high.
And what about other studies?
The fact that the researcher says there have been no previous studies on this topic is not true. I found at least one study comparing the effect of squatting with free weights and on a Smith machine on testosterone and cortisol (16). And I am sure that there are more of them.
In general, these studies show that testosterone increases more after squatting with free weights than on a Smith machine, although the difference is not always significant. However, these studies often show no difference in cortisol levels.
In conclusion, the present study does confirm that there is a difference in hormone responses between free weight and machine exercises. However, I think it is not justified to conclude that free weight exercises are more effective for this reason alone. I do believe that free weight exercises are generally more effective than machine exercises. However, this is mainly because they allow more freedom of movement, which is not possible with a machine.
Free weight exercises have other advantages as well, such as working out stabilizing muscles and training balance. There is less difference in hormone effects than this study suggests.
As a limitation of the study, the researcher himself mentions the limited number of participants, which is 36 (46 minus 10 dropouts), which is still more than in the study with which I started this article.
Differences between men and women
However, the number of participants must be divided between men and women, resulting in a smaller sample size per group (15 men, 21 women). Given the differences between genders, as shown in this research among others, the differences between free weights and machines must be examined separately for each gender.
At the same time, as mentioned, this provides insight into the differences in how men and women respond to training with free weights on one hand and machines on the other. For example, it appears that in men, the testosterone/cortisol ratio increased immediately after training (on average across all types of training, both free weights and machines). Testosterone therefore increased proportionally more than cortisol. This was hardly the case in women.
Free weights or machine training: Does it matter?
I think the wrong question is asked in the study. It’s not so much about the difference between free weights or machine training. Both are just the application of two different training principles: Training through compound exercises on one hand and isolation exercises on the other.
As I mentioned, it matters which exercises are compared. How comparable are the exercises for a comparison between a machine and free weights? The smarter the machine is in simulating the free movement of free weights, the more useless it actually becomes to measure the differences. At most interesting for a manufacturer who wants to show that his squat machine is the only one that is truly comparable to squatting with a barbell and is safe enough for your grandma to train with.
Studies like this one reaffirm to me the benefits of compound exercises. Exercises involving multiple muscle groups at once, increasing total muscle mass used, resulting in more hormone production.
Isolation exercises, on the other hand, are a very effective means to ensure that the muscle groups you train that day are really pushed to the limit. For example, leg extensions before or after squats to ensure that the quadriceps leave the gym more fatigued that day than the lower back.
Therefore, in my opinion, you should not read these kinds of studies with the goal of determining the best way to train. In practice, it’s the application of multiple training principles that leads to success. It’s useful to know why those principles work to your advantage.
References
- Shaner, Aaron A. et al. The acute hormonal response to free weight and machine weight resistance exercise. Journal of Strength & Conditioning Research:POST ACCEPTANCE, 22 November 2013. doi: 10.1519/JSC.0000000000000317
- http://digital.library.unt.edu/ark:/67531/metadc149661/m2/1/high_res_d/thesis.pdf
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