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March 15, 2018

The Mind-Muscle Connection: A Key to Maximizing Growth?

In this case, it appears the bros were right…!

For as long as I can recall, bodybuilders have been preaching the importance of a mind-muscle connection for maximizing muscle development. In case you’re not aware, a mind-muscle connection (a variation of the concept in the field of motor learning known as an “internal focus of attention”) is the process of actively thinking about the target muscle during training and then feeling it work through the full range of motion. According to theory, this strategy maximizes stimulation of the muscles you’re trying to target in a given exercise while reducing the involvement of “secondary” movers. This combination hypothetically should result in greater growth.

Hypothetically….

Numerous studies have confirmed that a mind-muscle connection does in fact increase activation of the target muscle as measured by a technique called electromyography. However, higher activation of a muscle doesn’t necessarily mean it will hypertrophy to a greater extent over the course of a long-term training program. To my amazement, no one had endeavored to investigate whether adopting a mind-muscle connection during training actually had a beneficial effect on muscle growth in a controlled, long-term study.

So the curious science nerd that I am, I took it upon myself to find out. Here’s the scoop on our recently published paper on the topic.

What We Did
30 college-aged men agreed to participate in the study and were randomly assigned to either train with an internal focus (mind-muscle connection) or an external focus. All participants performed 4 sets of arm curls and leg extensions for 8 to 12 RM on 3 non-consecutive days per week, with sets carried out to muscular failure. Every rep of every set was supervised by one of my research assistants. The mind-muscle group was instructed to “squeeze the muscle” on each rep while the external focus group was instructed to “get the weight up.” The exercise portion of the program lasted 8 weeks with a week taken for testing immediately before and immediately following the training period.

As those of you who follow my work undoubtedly know, the vast majority of my studies are carried out in subjects with resistance training experience. However, in this case I decided to use untrained subjects.

Why?

Well, trained individuals tend to get hardened into a given attentional focus (called a “deep basin” in motor learning). It’s therefore difficult to get these individuals to change their focus during training. This would be especially problematic in a study such as this since there is no way to be sure what the lifter is actually thinking when training. An untrained lifter is a blank slate and thus we could be more confident that he would follow the prescribed attentional focus strategy.

I also chose to use only single joint exercises for the study. The reasoning here is that it’s easier to focus on a given muscle during a single joint lift. Squats, rows and presses involve multiple primary muscle movers that makes it difficult for a lifter – particularly one with no training experience – to focus on a given single muscle. What’s more, multijoint exercises require more of a learning curve to coordinate movement patterns in the early stages of training, which would further impair the ability to develop a mind-muscle connection as well as delaying the onset of hypertrophy in favor of neural adaptations.

What We Found
After 8 weeks of consistent training, subjects who used a mind-muscle condition had almost double the muscle growth in the biceps brachii compared to those using an external focus (12.4% vs 6.9%, respectively). Alternatively, muscle growth for the quadriceps was similar between conditions. From a maximal strength standpoint, isometric strength of the elbow flexors increased substantially more for the internal focus group while knee extensor strength was markedly greater for the external focus group.

What We Learned
The novel finding of the study was that superior gains in biceps hypertrophy were made by employing an internal focus of attention. Based on these findings, it appears the bros were right; employing a mind-muscle connection enhances muscle growth.

But wait a sec; if that’s the case, then how come attentional focus did not seem to matter for thigh hypertrophy…?

Although it’s impossible to say for sure since we didn’t attempt to investigate mechanisms, a possible reason is that subjects simply found it easier to focus on the biceps as opposed to the quads. This is logical given that the upper extremities are used for fine motor skills (i.e. picking things up, writing, etc) while the lower extremities are involved in gross motor skills (i.e. walking, kicking, etc). Thus, people tend to be more conscious of their arm muscles and less so of the leg musculature. The fact that the subjects were untrained would seemingly contribute to this discrepancy. I’d hypothesize that well-trained lifters would be better able to focus on the quads when training and thus achieve better hypertrophy. This needs further study.

Here’s the take home: It appears beneficial to adopt a mind-muscle connection if your goal is to maximize muscle growth. Instead of worrying about a specific tempo, simply focus on the muscle being trained and visualize it working throughout the full range of motion. Now this comes with the caveat that findings are specific to a moderate rep range; using heavy loads (i.e. 3-5 reps) may preclude the ability to take advantage of this strategy as your focus would conceivably have to shift to just getting up the weight as efficiently as possible. Importantly, this is just one study and shouldn’t be taken as the be-all-end-all on the topic. Hopefully more longitudinal studies will be conducted on the topic to draw more definitive conclusions. Future research should look to compare internal versus external focus strategies using multi-joint exercises in trained lifters to better understand how a mind-muscle connection impacts growth.

For further insights, check out the video I did for Omar Isuf’s YouTube channel below. I discuss the nuances of the topic and their relevance to practical application in a lifting program.