INTERmuscular and INTRAmuscular Strength/Coordination and Why That’s Important

FIRST, what is the difference between these two things and what do they mean?

INTERmuscular refers to a group of muscles working together, or synchronizing, to complete an action or generate force.

INTRAmuscular refers to a single muscle’s action or ability to create force.

     I have found the difference between the two hard to keep straight in my head but I’ll explain how keep them organized and not get them confused. I think it might be a little out there, but stick with me, and if you are thoroughly confused by the end, I apologize. 

     INTRAmuscular has an “A” in it. “A” is the first letter in the alphabet. First means one, and one muscle is performing the action. INTERmuscular, on the other hand, means that a group of muscles are performing the action (more than one muscle). For example, a bicep curl or isolation exercise is considered INTRAmuscular strength/coordination, whereas the bench press involves a multitude of different muscles working together and is INTERmuscular strength/coordination.  

Why is this important?

     Higher-level athletes and experienced lifters will show a better synchronization of their muscles to produce more purposeful movement. In other words they have very good INTERmuscular skill. This allows the athlete or lifter to use as many of their muscles as possible, in unison, to create an action or force. A good example is to take a look at any throwing athlete, like a shot-putter or pitcher. It takes A LOT of INTERmuscular coordination to get maximal amount of force to go into the implement being throw, the shot put or baseball. Despite the differences I just outlined, INTERmuscular and INTRAmuscular strength/coordination go hand in hand. 

     All things being equal INTERmuscularly, INTRAmuscular ability will set the difference between two athletes. This doesn’t happen in the real world, due to biomechanical differences among individuals, but the concept is important. If the muscles contributing to the action are stronger INTRAmuscularly, the athlete or lifter with better INTRAmuscular strength will outperform the other.

      If athletes and lifters are equal INTRAmuscularly, their INTERmuscular ability will set them apart. This is the more important of the two, in my opinion. Motor patterns and movement efficiency are key to attaining the highest level of physical performance possible. For example, if you take a look at a newbie in the gym trying to dumbbell bench, they have a very hard time stabilizing the weight and moving it in an efficient line from point A to B (Figure 1). The lifter who has more skill and has developed a more conditioned motor pattern will move the weight much more efficiently from point A to B and will, more likely than not, be able to lift more weight. 

     From this diagram you can see the interplay between the two and how they impact performance. You cannot just have one or the other; you must have a combination of both. Both INTRAmuscular and INTERmuscular strength come with time and practice. It is important to remember, especially if you are a new lifter or are acquiring a new skill, to take it slow and progressively work your way into it. Even if your muscles have the INTRAmuscular strength to lift a weight and/or do an activity, if the INTERmuscular ability isn’t there, things can go wrong. This is when injuries happen. Take the time to learn the INTERmuscular ability and learn the motor pattern and movement efficiency. The skill and strength will come with time.


Ryan Goodell, CSCS

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