Is the mind-muscle connection broscience?

The mind-muscle connection is a concept from bodybuilding circles that made it into exercise science. The mind-muscle connection refers to our ability to sense how well a muscle is being trained and our ability to selectively activate our target muscles during an exercise. The idea is that a good neural connection between your brain and a muscle allows you to feel how well you’re training that muscle and thereby adjust your program. For example, a bodybuilder may forsake an exercise because they can’t get a good mind-muscle connection and replace it with an exercise they feel more strongly in the target muscles. The mind-muscle connection is also purported to give us the ability to make our bodies preferentially recruit our target muscles. By focusing on the target muscles while you exercise, you can feel them more, and this is taken as a sign those muscles are activated more and will therefore grow more.

But are our feelings in line with the facts? In my last article, I covered if we can actually sense how much tension a muscle experiences. Now let’s turn to the other side of the mind-muscle connection: our ability to volitionally emphasize certain muscles during an exercise with the power of our mind. Can we intentionally change our muscle recruitment levels by focusing on a muscle, and if we can, will that make the muscle grow more? Can we make a muscle activate more with the power of our mind and thereby get better gains?

Attentional focus

A study by Calatayud et al. (2016) put the first question to the test in a group of trained men. The men were benching over 2 plates on average. The researchers investigated how bench press EMG muscle activity in the triceps and chest changed when the men pressed without instructions compared to when they tried to isolate their chest or triceps. The researchers tested this at various intensities from 20% to 80% of 1RM. The result was a clear trend in decreasing effectiveness of attentional focus at higher training intensities. At 20-40% of 1RM, the trainees experienced higher pec activity when focusing on their chest and higher triceps activity when focusing on their triceps, with no other differences in muscle activity. They certainly didn’t isolate the pecs, but they definitely emphasized them. So overall a win for the mind-muscle connection. However, at 50% and 60% of 1RM, something unintended happened. Trying to isolate the pecs still successfully emphasized the pecs, but trying to isolate the triceps started to increase not just triceps but also pec activity by an identical amount (4-5%: more on this later). At 80% of 1RM, the mind-muscle connection failed entirely: there was no more effect of either instruction on either muscle. The men only performed 3 reps at each intensity, so these results suggest that the mind-muscle connection ceases to be effective when training anywhere close to failure.

A replication study by Paoli et al. (2019) had similar findings. They found no significant effect of the mind-muscle focus on pec activity at either 50% or 80% of 1RM, but there was a significant effect on triceps activity at both intensities.

 

Similar but slightly different results have been found for rows as well. Fujita et al. (2020) compared 2 groups performing seated rows at 70% of 1RM until they lost movement velocity (so quite submaximal but not nearly as submaximal as the previous study), either with no instructions or with the instruction to ‘pull from the back’. During the set as a whole, muscle activity as measured by median EMG frequencies did not significantly differ between the groups for any muscle. The researchers concluded: “Verbal instruction seems to have little effect on increasing myoelectric activity of these targeted muscles in an entire set of resistance training.” When we zoom in on the muscle activity over time, we do see some effect at the start of the set. Pulling from the back increased lat activity during the first 2 reps by 15%. Interestingly, pulling from the back also decreased posterior deltoid activity by 14%. Midway through the set, posterior delt activity was still suppressed compared to the control group, whereas lat activity was no longer increased. At the end of the set, there was no difference in either muscle’s activity anymore, nor was there any difference in any other muscle throughout the whole set. Overall, these findings confirm that we can only enhance target muscle activity with attentional focus during very submaximal training. The effect fades as we get anywhere close to muscle failure.

Lifting explosively also seems to negate any effects of the mind-muscle connection. Calatayud et al. (2018) replicated their study on trying to isolate the pecs or triceps during the bench press with a new variable: lifting tempo. One group benched with a controlled 2-2 tempo: lifting the weight up over 2 seconds and lowering it for 2 seconds. The other group used an explosive tempo, pushing the weight up as fast as possible and then lowering it over 2 seconds. Both groups performed 3 reps at 50% of 1RM. The controlled tempo group could emphasize their pecs or triceps by thinking about them, but the explosive tempo group could not. Thus, it seems that an explosive lifting tempo decreases our ability to target muscle groups with our mind, just like a higher training intensity or getting closer to muscle failure.

You may argue these participants simply didn’t have a good mind-muscle connection, because they weren’t trained enough. However, training experience does not seem to improve our ability to isolate muscle groups by focusing on them. Daniels et al. (2017) replicated the above bench press study design in a group of well-trained (average bench 126 kg / 278 lb) and a group of untrained participants. Neither group successfully managed to increase muscle activity in their triceps or chest by focusing on them. And again they only performed 3 reps at 80% of 1RM, so they weren’t even training hard yet. There was even a negative effect when the 2 groups’ data were combined: trying to emphasize the chest decreased activation of the short head of the triceps without increasing activation of the chest or anterior deltoids. These findings suggest that the mind-muscle connection could even be counterproductive with heavier weights, regardless of how well-trained you are.

Fujita et al. (2019) again found no effect of internal attentional focus on muscle activity, neither in untrained nor trained participants, during a set of seated rows to failure at 70% of 1RM. The control group was simply instructed to perform as many reps as possible, while the internal cue group was given the instruction to pull with their back and focus on pulling their elbows back. An instructor also palpated their lats to enhance the mind-muscle connection, evidently to no avail.

Overall, paying attention to the mind-muscle connection during your training doesn’t appear to be effective to emphasize the muscle groups you’re focusing on, unless your idea of ‘training hard’ means having some difficulty checking your Instagram feed during leg extensions. When training explosively, with heavy weights or close to failure, most research finds no effect of a mind-muscle focus on that muscle’s level of activation. Why isn’t focusing on the mind-muscle connection effective?

It’s because our brains are too awesome. The motor cortex – the part of our brain that coordinates movement – is really good at its job. Your brain’s motor cortex functions like a Bayesian system that has been fine-tuned over millions of years of evolution. Most movements, like walking, are so complex in terms of muscle recruitment pattern that our conscious thought can’t remotely govern this task as well as you can do intuitively. Even the brightest mathematicians can still barely create robots that walk with a semblance of elegance across uneven terrain. In this respect, trying to take over complex movements with your conscious thought is like trying to hack a computer by poking into its motherboard with a kitchen knife. In fact, just thinking of a complex movement like running while you’re doing it reduces movement efficiency. This reduced efficiency is also what happens when we use internal cues like focusing on a specific muscle.

Internal vs. external cues

When we tell our brains what we want to achieve with a movement, it will optimize our muscle recruitment pattern to achieve this very efficiently, generally with the minimum energy expenditure necessary for the target outcome. For example, if you want to throw a dumbbell at someone doing curls in the squat rack, you don’t have to think about which muscles you’re going to use. You can just think: “This goes there” and your brain will automatically coordinate the movement for you. You can decide if you want to optimize for accuracy or power and your muscles will intuitively activate accordingly. These cues that you give yourself are called external cues: your attentional focus goes to something outside your own body. (Note: don’t actually throw dumbbells at people in the gym. It’s impolite.)

In contrast, focusing on the mind-muscle connection is a form of internal cueing: you focus on something inside your body, namely the target musculature. Internal cues result in worse performance than external cues across a wide variety of movement tasks, including maximal force production and repetition performance [2, 3, 4]. For example, Nadzalan et al. (2020) found that subjects can generally perform 1 to 2 more repetitions during squats or deadlifts with a 10RM load when thinking of lifting as much weight as possible (external focus) instead of when thinking about using their legs (internal focus). The external focus also increased average ground reaction forces, meaning the subjects put more force into the ground: this suggests that total force production and thereby muscle mechanical tension were higher.

An external focus is also best for long-term strength development. Nadzalan et al. (2019) in untrained men and Taylor et al. (2017) in strength-trained athletes both found significantly greater improvements in squat and deadlift strength in people training with an external focus than people training with an internal focus. Ghanati et al. (2022) also found greater improvements in hip strength, stability and athletic performance tests in athletes completing a training program with an external vs. internal attentional focus.

Internal cues, such as focusing on your quads during squats, are bad for performance, because they disrupt the optimized muscle recruitment pattern that your brain would otherwise have used. For the mathematics lovers, internal cues result in constrained instead of unconstrained optimization in the brain.

Internal cues should also be unnecessary if your exercise selection is good. A good exercise for a muscle will strongly, often maximally, activate that muscle. That’s the whole point of the exercise. For example, the bench press involves horizontal flexion against resistance. Since the pecs are a horizontal flexor, they contract to perform the movement. Lifting as much weight as possible thus requires maximum pec force production, tension and muscle activation. You don’t have to focus on the pecs to achieve this. Your brain will do it automatically if the goal is maximum performance. In other words, internal cues result in inefficient movements.

This inefficiency can sometimes masquerade as greater muscle activity. Remember that Calatayud et al. (2016) found that trained men trying to isolate the triceps at 50-60% of 1RM during the bench press increased not just triceps but also pec activity equally? That’s probably because the internal cue made the exercise as a whole more difficult, which effectively increases the training intensity. A weight that’s 60% of your 1RM may become 65% of your 1RM when you use internal cues, as those can make you weaker. It wasn’t so much the power of the mind-muscle connection but rather just inefficient movement.

Similarly, a study by Snyder & Fry (2012) found that trying to isolate the pecs during 3 bench press reps at 80% of 1RM was in fact successful for the pecs, in contrast to all the other studies, but it also increased front delt activity. In fact, shoulder activity went up a bit more than chest activity (17% vs. 13%) when trying to isolate the chest. Triceps activity only went up with a mind-muscle focus at 50% of 1RM, not at 80% of 1RM, as in most research. So again, it wasn’t so much that the mind-muscle connection really selectively enhanced the training stimulus for the target musculature but rather that a mind-muscle focus created an inefficient movement that made the exercise harder.

Analogously, remember that Nadzalan et al. (2020) found that focusing on the legs during squats and deadlifts decreased how many reps they could do and how much force they produced, suggesting lower total muscle tension? They also found that the mind-muscle connection increased quad and hamstrings EMG activity. The higher muscle activity despite lower total force production was likely due to greater inefficiency of movement, as well as the shorter duration of the set due to being able to perform fewer reps. These findings may at first glance appear to support the effectiveness of a mind-muscle focus (although sometimes for the wrong muscles), whereas they likely just represent inefficient movement, resulting in higher muscle activity levels by ‘virtue’ of making very submaximal exercise harder. As the research shows, these effects disappear when training with heavier weights, when training remotely close to failure or when lifting explosively.

We see a similar effect of making exercises artificially harder in blood flow restriction research, where occluding the triceps also increases chest muscle activity and occluding the legs also increases glute activity. Blood flow restriction training increases muscle activity levels and muscle growth just as much in the occluded as the non-occluded muscles [2]. It makes the overall exercise more difficult, raising the effective percentage of your 1RM that you’re lifting and thereby increasing muscle activity levels when using light weights.

It’s worth noting that inefficient movement can sometimes be useful when injured. In situations where you deliberately want to use lighter weights, a mind-muscle focus could help you maintain decent muscle stimulation with lighter weights. However, just lowering the weights or implementing blood flow restriction is arguably a more reliable method to achieve the same effect, likely with better strength development in the process.

That one study

Muscle activity aside, what about muscle growth? If a mind-muscle focus doesn’t increase the activation of the muscle you’re focusing on and it decreases total force production of the set, it logically can’t increase muscle growth in that muscle. In fact, if your reps go down but muscle activity levels don’t go up, as most research finds, this should reduce the total tension the muscle experiences. It would be nice to test this experimentally. Unfortunately, we have only one study that has tested the effect of internal cueing on muscle growth.

Schoenfeld et al. (2018) compared 2 groups training with either the instruction to “get the weight up” or the instruction to “squeeze the muscle” during barbell curls and leg extensions. The training consisted of 4 sets of 8-12 reps to failure twice a week. After the 10-week training program, the internal cue group did not gain more muscle in their quads, but they did gain more muscle in their biceps. Total body skeletal muscle mass and body composition did not differ across groups. Unfortunately, the authors did not report dynamic strength development and training volumes, so we can’t see if the internal focus negatively affected how much weight the participants could lift, as we would expect based on the other research. They did report isometric strength development, which did not significantly differ across groups.

Why would ‘squeezing the muscle’ be effective for barbell curls but not leg extensions? If the mind-muscle focus significantly improved muscle growth, it should have affected both muscles, but the results were movement-specific. It’s plausible that the ‘muscle squeezing’ group had better exercise technique. You can’t mess up a leg extension, but instructing untrained, college-aged males to ‘get the weight up’ during barbell curls to failure often results in something that looks more like a supinated power clean than a strict biceps curl. The elbows come forward, they skimp on the range of motion and they lean back during the curl. Instead, the authors speculated that the participants couldn’t ‘establish a mind-muscle connection’ with their quads because they were untrained. This explanation requires the hypotheses that the mind-muscle connection varies per muscle group, that trained individuals have a better mind-muscle connection than untrained individuals and that attentional focus increases muscle growth despite most research finding negative effects on force production and no effect on muscle activity. Given that multiple studies have failed to find any effect of training status on our ability to isolate muscle groups and that there is no evidence that these mechanisms differ per muscle group, this theory is highly questionable and convoluted. Better exercise technique is a much simpler explanation that aligns better with the mechanistic research and doesn’t require multiple additional hypotheses (Occam’s Razor).

Speaking of the difference between attentional focus per se and better technique, some people use the mind-muscle focus deliberately as a cue to improve exercise technique. This can work, at least during isolation movements. Focusing on the mind-muscle connection generally reduces ego lifting and makes people perform isolation movements stricter. However, it’s probably more effective to directly think of the exercise technique that you want so that your motor cortex can optimize that exact movement. The more direct the technique cue, the better, research finds. For example, Beach et al. (2018) found that instructing people to ‘not round their spine’ during object lifting (deadlifting essentially) was significantly more effective to prevent spinal flexion than the cue to ‘use your legs’ or ‘bend with your knees and hips’. The
motor cortex is incredibly good at its job, so when you instruct it what its job is (lift the weight without rounding the spine), it will do it well. In that same vein, if you want to do something like keep your elbows at your sides during barbell curls, it’s probably more effective to just think of exactly that: keep your elbows in place. This is likely more efficient than thinking of the biceps.

In sum, the limited body of evidence we have does not support the bodybuilding idea that focusing on a muscle makes it activate more and thereby grow more. Most evidence indicates that when you’re training hard, we can’t increase muscle activation further, because it’s already maximal. Focusing on performance normally maximizes force output and muscle activity, which should thereby maximize muscle tension if you perform the right exercises with good technique. We also know that focusing on the mind-muscle connection, and internal cues in general, decrease how much weight we can lift and how many reps we can perform with a given weight. We have only 1 highly ambiguous study on how this affects muscle growth. The primary stimulus for muscle growth – mechanical tension – should align with force output, so how could muscle growth increase without making a muscle more active and while decreasing performance?

Conclusions

The mind-muscle connection is not total broscience, but there is also no convincing evidence to supports its use. It’s questionable if humans are biologically equipped to accurately sense mechanical tension or muscle activity. The existing research suggests subjective and objective muscle activation don’t consistently align and there are clearly many cases where how much we feel a muscle does not correspond with muscle activity or tension. In our recent study on squats vs. hip thrusts, we found that all participants felt hip thrusts better in their glutes, yet hip thrusts were objectively no more effective than squats for the glutes. We also don’t appear capable of significantly isolating muscle groups by focusing on them during high-effort exercise, not even if we’re very well-trained. The effects of attentional focus on muscle activity are limited to very submaximal exercise. During intensive training, our motor cortex will automatically optimize muscle activity levels to maximize performance, if we tell it that performance is the goal. Research finds that focusing on performance and exercise technique is more effective for both than focusing on the mind-muscle connection. For muscle growth, muscle tension should also be maximized by maximizing force output, although empirically we’re limited to just a single highly ambiguous study.

If how well we feel a muscle was the best determinant of muscle growth, we should all be chasing the pump and muscle soreness. We’d all be training each body part very infrequently with a high volume per session, using moderate rep ranges and performing partial reps in the mid-range of motion with relatively short rest intervals, post-failure techniques and high exercise variety. Guess what: that’s exactly how most bros train and research has debunked all of these practices as optimal [2, 3]. The hallmark of broscience is basing your training practices on your feelings and trying to rationalize those with science. Although definitive evidence is lacking, I think this also applies in large part to the mind-muscle connection. I recommend designing your training programs primarily based on scientific evidence and biomechanics. How an exercise feels is certainly a consideration, but you should be skeptical of blindly trusting that how much you feel an exercise in a muscle is a direct measure of how much muscle you’ll gain from it. You may feel a pump or a stretch or some metabolic activity, but there’s no telling if this accurately corresponds to mechanical tension. The path to truth is not paved by sensations but by science, logic and data. Facts over feelings.