Study: the muscle strength of positive thoughts

Positive thinking and training your muscles with it? It is possible, and it has everything to do with the way our muscles are controlled. In the article on muscle memory, I discussed the connection between the brain and the muscles. By performing actions such as writing and cycling, your brain sends signals to the muscles. The more often you send these signals, the stronger this connection between the muscle and the brain becomes.

This type of "muscle memory" is what makes practice lead to mastery. But what happens if you do send the signals without performing the action? For example, if you imagine that you are cycling and, through positive thinking, perform all the related actions. Does the connection also become stronger, so that you benefit from it when you actually start cycling? Yes, that does seem to be the case in the studies I discuss in this article.

Thinking positively about the exercise during rest between sets

Researchers from the University of Lyon had 21 students with no strength training experience train three times a week for four weeks.

They had them perform the leg press and chest press. The test group (called the MI group in the study, after "motor imagery") was asked to visualize performing the exercise during the rest between sets. The control group (CTRL) performed neutral tasks. After three weeks, the researchers looked at the difference in increase in maximal strength, number of repetitions and muscle size between the two groups. The increase in strength on the leg press in particular showed a significant difference.

The MI group was instructed to visualize and feel the correspondent contractions during the rest period, whereas the CTRL group carried out a neutral task. The maximal voluntary contraction (MVC) and the maximal number of repetitions (MR) using 80% of the pre-test MVC weight were measured. Although both MI and CTRL groups enhanced their strength through the training sessions, the leg press MVC was significantly higher in the MI group than in the CTRL group (p<0.05)

In the chart below you can see the difference in results for maximal strength on the leg press and chest press between the control group (white) and the test group (black). On the leg press especially, you can see a clear difference in strength and endurance (number of reps). The increase in leg circumference was also greater in the group that visualized the exercise in between. In the arms and chest (the chest press), the differences were smaller.

	MI	Control
Bench press (kg)	+6.23	+7.75
Leg press (kg)	59.77	42
Bench press (reps 80 % 1RM)	+3.78	+2.9
Leg press (reps 80 % 1RM)	+17.75	+12.8
Circumference right arm (cm)	+0.11	+0.15
Circumference left arm (cm)	+0.06	+0.05
Circumference chest (cm)	1.0	0.0
Circumference right leg (cm)	+0.25	+0.1
Circumference left leg (cm)	+0.75	+0.15

It can therefore add value to avoid chatting between sets and instead silently visualize the execution of the next set as if you were performing it in your mind.

"Try to imagine yourself performing the motor sequence with your eyes closed, by perceiving the different movements just as if you had a camera on your head, and feel the body's sensations", was the researchers' instruction. "You have to see and feel only what you would see and feel if you had to perform this particular skill (bench press or sled leg press). Imagine the movement using the most comfortable way for you, and make sure not to contract your muscles."

Incidentally, the researchers unfortunately did not look at, or try to control for, circumstances such as the participants' training status, diet, body composition and participation in recreational sport during the study period. These are circumstances that can influence the outcome.

Better recovery of torn tendons through imagined training

Researchers from UMC Groningen looked at the recovery time of a repaired tendon in the forearm (the flexor of the fingers). After surgery, recovery takes an average of 12 weeks. Especially in the second week, the repaired tendon is still so weak that it can tear again if overloaded. Prolonged splinting, however, can cause adhesion, the sticking together of organs or tissues, in this case for example muscles. Good recovery therefore depends on the right load, not too little and not too soon or too much. The researchers from Groningen wondered whether there was a way to stimulate the tendon more without loading it more. They started from the knowledge that reduced functionality of limbs after surgery is partly caused by the fact that the function is temporarily forgotten because it is no longer being performed. As a result, it has to be learned again, which delays recovery. They therefore investigated whether recovery improves by thinking about performing this function, in this case bending the fingers.

"In the past, it has been shown that sensory input not exclusively results from actually performed movements. Imagined movements without actually moving the limbs (motor imagery) also generate sensory input."

They tested this on 25 patients who had all just been admitted with torn tendons and underwent surgery (they started with 28, but two of them also turned out to have a fracture, while in a third patient the tendon turned out to be intact). In the first four weeks after surgery, according to the normal procedure, they were not allowed to do anything with their fingers. During this period, the researchers had half of the patients do imagined exercises for the fingers. They had to imagine making a fist and flexing their wrist, holding this for three seconds, and then extending the wrist and fingers again. They had to do this 10 times per set. Each day they did eight such sets. After this, the normal rehabilitation period began, during which the researchers looked at the difference in recovery between the test group and the control group. In one test, an image of a hand on a screen showed one finger lighting up each time. The patient then had to touch it with the real finger. In the chart next to it, you can see the differences in speed between the test group and the control group. This showed that the people who had imagined using their fingers recovered faster than the people who had not. They also looked at differences in strength. However, they found no significant differences there.

The researchers did note that the results may have been negatively affected by the fact that they could not check whether the patients in the test group really imagined the exercises often enough and long enough. To guide this somewhat, they asked the patients to keep a log of when they did their exercises. This showed that not everyone had followed the instructions. The result might otherwise have been larger.

Making muscles grow by thinking positively about training

For a similar reason, other researchers from Groningen looked at the effect of imagined training on the calf muscles. This was also to speed up recovery from, for example, a broken ankle, and here too they wondered whether imagined training can help during the period when the patient is not yet allowed to do anything. They divided 29 people into three groups. One group did imagined training, the second group did real, low-intensity training, and the third group did nothing. The group that trained for real did so by lying on their back on a mat with their feet flat against a wall and then pushing off with the toes without letting the back move over the mat. In this case, only the weight of the legs served as resistance. The second group watched a film of someone performing calf raises with a barbell on the back (standing on the toes and lowering again) and had to imagine that they were doing the exercise. In the group that imagined the training, strength increased by 36%. In the group that had trained for real, this was 13%.

"Plantar-flexor torques were measured before, during, directly after, and 4 weeks after the training period. At the end of a 7-week training program, significant differences were observed between the maximal voluntary torque production of the imagery training group (136.3 +/- 21.8% of pretraining torque) vs. the low-intensity training group (112.9 +/- 29.0%; P < 0.02) and the control group (113.6 +/- 19.2%; P < 0.02). The results of this study show that imagery training of lower leg muscles significantly increased voluntary torque production of the ankle plantar-flexor muscles and that the force increase was not due to nonspecific motivational effects. Such muscle strengthening effects might be beneficial in rehabilitation for improving or maintaining muscle torque after immobilization."

An imagined workout as an alternative to a missed workout

Due to circumstances, you miss a workout. You already see your training split being ruined and wonder how you should now divide your training across the days. According to researchers from Justus Liebig University Giessen in Germany, you can solve this by simply doing the workout in positive thoughts. They had 43 sports students follow a training program for four weeks. In it they trained the bench press, leg press, triceps extension and calf raise. They did this twice a week in four sets of 15 repetitions. After that, the experiment began in a new four-week period. They divided the students into three groups. The first group (M0) did only "real" strength training. The second group, the test group, was divided into three groups:

M25. This group replaced 25% of the real training with imagined training.
M50, this group replaced 50%.
M75 replaced 75%.

Percentage increase in strength, real training versus imagined training. Non-practiced refers to the untrained muscles.

The third group (CO) served as the control group and did "nothing".

Training was done three times a week (either real or imagined), for a total of 12 training sessions. The training consisted of four sets of isometric training. This static load was performed in this case with the usual training machines for the exercises mentioned above, but adjusted so that static loading could be trained in a fixed position. With the leg press, for example, tension was held at an angle of 100 degrees. Four sets were done of two maximal isometric contractions of five seconds followed by 10 seconds of rest. Between the different exercises they took 90 seconds of rest. The groups that also performed imagined training sessions were instructed to imagine as well as possible that they were doing the exercises, including the associated feeling, but without actually tensing the muscles.

"They were instructed to imagine maximal contraction efforts as vividly as possible, using kinesthetic imagery ("you should imagine the sensation associated with a contraction effort, but your muscles must stay relaxed")"

Maximal isometric strength was measured before and after the experiment. Test groups M25, M50 and M75 showed a slightly smaller increase in strength than the group that had only done real training (M0) (3.0% compared with 4.2%). However, they showed a "significantly greater improvement" than the group that did nothing, whose strength had actually decreased (-0.2%).

"Naturally, strength training cannot be carried out without highly intensive real effort. However, high-intensity isometric strength training sessions can be partly replaced by IMC training sessions without any considerable reduction in strength gains. This holds at least for athletes at the recreational level. Moreover, we have shown that IMC training is also effective after a prior 4-week physical strength training phase. Our findings support the assumption that IMC training is an adequate supplementary method for improving muscle strength."

Beforehand, tests were also used to see how well the subjects could imagine something. The results showed that the better the imagery ability, the greater the increase in strength and reaction time.
Another example of the power of the mind

The Americans also contributed to research into the muscle-strengthening power of the mind. Researchers from The Lerner Research Institute in Cleveland had eight subjects mentally train the biceps for 12 weeks, five days a week and 15 minutes a day, by imagining biceps curls. A second group of eight people imagined training the little finger, in which they had to imagine pushing the little finger outward against resistance (ABD). The little finger and this movement were chosen deliberately because this function is almost never used and they wanted to compare the difference in result with a frequently used muscle. A third group of eight people trained the little finger for real and a fourth group of six people did nothing (CTRL).

In the group that trained the little finger mentally, strength increased by 35%. In the group that trained the biceps mentally, this was 13.5%. Unfortunately, for real training they only looked at the little finger, where strength increased by 53%. The most interesting difference is therefore that of the mentally trained group compared with the group that did nothing. In the control group that did nothing, strength did not increase significantly, neither for the finger nor for the biceps. Respectively 35% and 13.5% growth in muscle strength compared with zero growth is a good argument for doing an imagined workout instead of doing nothing.

"The improvement in muscle strength for trained groups was accompanied by significant increases in electroencephalogram-derived cortical potential, a measure previously shown to be directly related to control of voluntary muscle contractions. We conclude that the mental training employed by this study enhances the cortical output signal, which drives the muscles to a higher activation level and increases strength."

Researchers from The University of Iowa also performed a comparable study on the developed muscle strength of the left little finger after real, imagined or no training. Besides looking at the developed strength, they also used EMG to look at muscle tension during tensing, imagining or doing nothing. To test the theory that initial muscle strength is developed by developing the connection between the brain and the muscle, and not by the contraction itself, they also looked at what happened in the untrained right little finger. What they discovered was that not only did the mentally trained left little finger grow in muscle strength, but so did the untrained right little finger.

Trained group: Left = + 30% Right = + 10%
Mentally trained group: Left = + 22% Right = + 14%
Untrained group: Left = + 3.7% Right = + 2.3%

The EMG showed comparable results. The untrained side therefore also benefits from the connections that are strengthened between the brain and the muscles.

Getting stronger by watching a workout

Many of you will have watched men like Schwarzenegger in Pumping Iron, Kai Greene in A New Breed and/or Ronnie Coleman in On The Road. Watching a DVD of, about or by a bodybuilder can provide a strong stimulus to start training. Personally, I also find it very pleasant to put on such a DVD during home workouts. This is not only good for motivation, but also produces more strength during the workout, provided you are doing the same exercises at the same time as those being performed in the film you are watching. Japanese researchers from Kyoto University came to this conclusion. They had 16 subjects squeeze a spring with fingers and thumb, 90 times per minute. The researchers measured the force with which it was squeezed. They saw that when the squeezing on the screen happened at the same time as the subject's contraction, the spring was squeezed with more force. Perhaps a tip for the gym to hang up some screens and play films with titles like those mentioned above?

The power of color

If you are going to watch one of those films, then A New Breed by Kai Greene is especially recommended. Not only because Kai Greene is the ambassador of the mental aspect of bodybuilding ("The mind is everything"), but simply because he wears red clothing. And seeing the color red makes you able to generate more strength than, for example, green. That was the conclusion of researchers from Knox College in Galesburg (US). They had 20 subjects look at a red wall for one minute and then squeeze a dynamometer twice, measuring the average force. After that they did the same, but had them look at a green wall. Another 20 subjects did it in reverse order, first green and then red, to cancel out the effects of order. Their study showed that looking at the red screen led to more strength. Of the 40 subjects, 26 were able to exert more force after looking at the red screen.

The researchers Pellegrini and Schauss performed a similar study on the difference between looking at a blue card or a pink card. Both men and women could generate more grip strength after looking at blue.

Another tip for the gym then: red or blue walls?

Conclusion

With the exception of the studies on the influence of color, all the studies mentioned are based on strengthening the neurological connection with the muscles. Many people already knew that you get better at something by repeating it often in positive thought. Think, for example, of skiers who visualize the descent at the top of the slope and have already gone down the slope many times in their minds before they appear at the start. I myself advise my students in Kobujutsu (an armed Japanese martial art) to repeat the material they have learned in their minds, just as a dancer mentally repeats choreography. In the past, I myself could not sleep before I had mentally repeated a newly learned kata several times. We often do this to strengthen memory so that, "in real life", you can concentrate on execution. The studies discussed here, however, show that a physical change also takes place in the muscles themselves. The increase in strength can still be attributed to improved coordination through mentally repeating the movement. In other words, the muscles are not stronger, your brain simply knows how to use them better. That is why the first study, on visualizing during the rest between sets, is so interesting. In that study, the growth in muscle size was also examined. The fact that those muscles also grew faster through thought implies that a physical change occurs in the muscles themselves. As a bodybuilder, of course, you are already happy with extra strength caused by the brain so you can train heavier during the workout. But you only become truly happy if your muscles also actually grow through the thought of training.

So use it to your advantage!

References

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• S. Hirose et a. Viewing hand grip enhances observer's grip force in a body-part-specific manner. Neuroreport. 2009 Oct 28;20(16):1477-80.)
• B.J. O'Connell et al. Grip strength as a function of exposure to red or green visual stimulation. Percept Mot Skills. 1985 Dec;61(3 Pt 2):1157-8.
• R.J. Pellegrini & A.G. Schauss Muscle strength as a function of exposure to hue differences is visual stimuli. Journal of orthomolecular psychiatry, 9, 144-147