Bogus Biomechanics, Asinine Anatomy: Part I

About the Author: Eric Cressey

Kinesiology Myths that Need to Die

By Eric Cressey

Call me anal-retentive, but when intelligent, experienced writers make incorrect statements in their publications, it makes me question their credibility. As we all know only too well, myths abound in the area of weight training (“high reps for toning”) and nutrition (“protein is evil”). Since the kinesiology and biomechanics realm is my area of expertise, erroneous statements tend to get on my nerves even more. With that in mind, here’s my opportunity to vent with respect to ten of those myths.

Myth #1: You can train the “medial deltoids.”

I always get a kick out of it when some of the most brilliant strength coaches (I can think of at least five) write about training the medial head of the deltoids with lateral raises or some other shoulder-specific exercise. These are some brilliant guys, so I never have the heart to speak up and tell them that “medial deltoids” don’t even exist. Incorporating exercises for this imaginary head is not only impossible, but attempting to do so represents a fundamental lack of knowledge of anatomy.

The term “medial” is a directional term that means “toward the midline” of, in this case, the body. From the anatomical position – standing, arms at sides, palms supinated (facing forward), the head of the deltoid that is sandwiched between the anterior and posterior deltoid fibers is actually the farthest away from the midline of the body of all of the heads of the deltoid. If anything, it should be called the lateral head! As such, these fibers are referred to as the “middle deltoid,” a term that correctly identifies their position between the anterior and posterior deltoid.

Myth #2: You can work on your left and right “bicep” and “tricep.”

These muscles both have more than one head, so you’d be better off saying, “You can work on your left and right biceps and triceps.” Now that we’ve got the terminology down in a broad sense, let’s look at the specific anatomy and how one can prioritize certain heads over the others. An important principle of which you should be aware is active insufficiency, a scenario that occurs when a two-joint muscle cannot contribute optimally to concentric action (i.e. shortening) at one joint because it is already shortened at another. In the case at hand, the long head of both the biceps and triceps can be preferentially recruited or excluded (for the most part) by avoiding or encouraging active insufficiency, respectively.

The long (lateral) head of the biceps crosses both the elbow and shoulder joint (and the radio-ulnar joint to act as a supinator, but we won’t worry about that right now), acting as an elbow and shoulder flexor. To maximally recruit the long head of the biceps, we need to eliminate one of these joint actions. As such, our options are to a) maintain shoulder extension (preferably past neutral) while flexing the elbow joint (e.g. incline curls) and b) flex the shoulder joint while maintaining elbow extension (e.g. front raise). Both scenarios avoid active insufficiency and force the long head of the biceps to bear the brunt of the load. Likewise, if we want to focus our efforts on the short (medial) head of the biceps, we simply flex the elbow with the shoulder flexed (e.g. preacher curls); because the long head of the biceps is already shortened at the shoulder, it can’t contribute effectively to elbow flexion.

The long head of the triceps also crosses the shoulder and elbow, but it acts in extension at both joints. If you want to overload this head of the triceps, you can a) maintain shoulder flexion while extending the elbow (e.g. overhead or lying extensions) and b) maintain elbow flexion while extending the shoulder (e.g. bent-arm pullover), although the latter option tends to recruit the lats and teres major more extensively. To reduce involvement of the long head of the triceps in favor of overloading the medial and lateral heads, simply extend the elbow with the shoulder extended (e.g. variations of pressdowns and dips).

Myth #3: The traps are just the muscles between your shoulders and neck; they can be trained with just shrugs.

This is an unfortunate misconception that has led to countless shoulder injuries in anatomy-ignorant lifters. The trapezius is actually a very large muscle that essentially spans from the lumbar spine all the way to the base of the skull. It can be divided into the lower, middle, and upper fibers; each of the three divisions has unique functions, so it’s almost easiest to think of them as separate muscles altogether (much like the different heads of the deltoid). The lower fibers are responsible for scapular depression, retraction, and upward rotation. The middle fibers contribute to scapular retraction, elevation, and upward rotation. Finally, the upper fibers contribute to scapular elevation retraction, and upward rotation, and extension, lateral flexion, and contralateral rotation of the neck. Interestingly, as you may have inferred, the different fibers of the trapezius can act as both antagonists (elevation and depression) and synergists (retraction and upward rotation) to each other! Perhaps more importantly, you hopefully can tell that shrugs only directly train scapular elevation and the upper traps, so you need to use a wider variety of exercises to achieve complete trapezius development. If you didn’t pick up on that, you’re hopeless; go play in traffic. The rest of you should note that the lower and middle trapezius both play crucial roles in maintaining scapular stability and proper posture, two factors with definite implications in terms of overall shoulder health.

Myth #4: Close-grip bench presses are good for the “inner” chest.

I’ve read a lot of anatomy books, but I’ve never come across the inner head of the pectoralis major. There are clavicular (upper) and sternal (lower) fibers, but selective recruitment of these fibers is a function of angle of inclination of the bench and different movement patterns rather than grip width. Bringing your grip closer together will recruit more triceps, though.

Myth #5: Your body doesn’t know the differences between similar exercises that target similar musculature.

I have been surprised to see this coming from a few prominent writers in the bodybuilding and strength and conditioning industries, so I thought this article would be a good place to air my disagreement with such a statement. Essentially (and pardon the stereotype), this is bodybuilding logic. For the most part, in the bodybuilding world, there are only muscles; in the quest to be big, and not strong or proficient at some athletic endeavor, many bodybuilders completely overlook the role of the nervous system in exercise selection.

Let’s start with the most basic arguments against this logic. As Mel Siff points out, “Subtle differences apparently as insignificant as a change in grip, stance or head position in regular training can cause significant neural changes which control the way in which the athlete executes a given skill (1).” When we change our grip on standing dumbbell curl variations, for instance, we can shift the emphasis within the elbow flexors among the biceps brachii, brachioradialis, and brachioradialis (among other muscles). Like I said, we’re starting with the basics, but let’s now make our example a bit more complex by comparing a preacher curl and a standing dumbbell curl. As I mentioned before, there are obvious muscular recruitment changes that occur due to the aforementioned active insufficiency of the long head of the biceps with the flexed-humerus position. Likewise, there are implications in terms of force production capabilities. According to Siff,

Many studies indicate that, in all of the diverse isolated single-joint movements, changes in strength apparently depend upon the role and functions of the joint mechanisms and the relative disposition of the body’s links relative to one another. Changes in joint angle alter the conditions of muscular work, since muscle length and angle of pull are changed. Muscular strength and leverage change, and consequently, so does the torque (i.e. moment of force) produced by the muscles about a joint (1).

Keep in mind that the above quote only refers to single-joint movement; as I’m sure you can imagine, when multiple joints are involved, recruitment patterns can differ even more dramatically. Because joint angle affects how muscles produce force, there are clear implications in terms of the overall training effect. For instance, at joint orientations, rate of force development (RFD) will be faster than at others; when dealing with athletes, this is an important consideration. Moreover, strength increases over the entire range of motion depend to a large degree on the joint angle in training at which maximum muscular tension is attained (1). If this strongest position is avoided (via partial reps, for example), the magnitude of the strength increases may be compromised.

Now, let’s go back to the preacher curl versus standing dumbbell curl example. Not only are recruitment patterns different within the elbow flexor musculature, but contributions (or lack thereof) from the rest of the kinetic chain are also altered. Far more stabilization must take place at multiple joints in the latter exercise because of the standing position and the lack of support for the upper arms. This underscores the importance of basing all training programs on core exercises; they simply involve more musculature and train recruitment patterns that are functional for our daily lives. It also demonstrates the differential training effect of, say, a floor press when compared to a 2-board press. Both have their place in training programs, but the latter involves greater muscle recruitment and loading in a fixed distance traveled by the bar.

Now, let’s take this a step further. Which is more neurally draining: a 1RM barbell curl or a 1RM deadlift? If you answered “the curl,” it’s time to start taking your lower body training more seriously. Very simply, the deadlift is more taxing because it requires more work (force times distance) to be done. Increasing both the force and distance components necessitate increased muscular recruitment via increased neural output. One step further: is a full ROM 1RM barbell curl more neurally draining than a ½ curl? Assuming the same weight it utilized, of course (force stays the same, but distance is greater). However, let’s assume you can use enough additional weight on the ½ curl to offset the reduction in distance, and the overall work is the same for both exercises. Then, you certainly have a conundrum. In a broad sense, the neural demands are similar; however, differences exist in terms of rate coding and fiber recruitment, depending again on joint orientation.

Here’s where a lot of folks want to end the discussion (if they’re even gotten this far without getting bored or confused). If we’ve established that subtle variations in exercises won’t markedly change the overall impression left on the nervous system, then we can go ahead and bench 52 weeks per year as long as we change our rep ranges and tempo of execution, right? Yes, but since when is lifting weights about “avoiding stagnation,” and not about “getting hella beeeg, fast, and strong?” That’s right; I’m talking about optimization of training here. Read on…

Training has a far more profound impact on the nervous system than just fiber recruitment. Most attention in the literature is focused on the efferent (motor) and not the afferent (sensory, or feedback) component on the nervous system. However, varying exercise selection – just like varying speed of execution, loading, and volume – is crucial to developing afferent pathways as well. Specifically, I’m referring to the joint receptors.

  • Pacinian corpuscles are rapidly adapting receptors that are highly sensitive to vibration frequency, acceleration, and deceleration.
  • Golgi-Mazzoni corpuscles are sensitive to compression of the joint capsule, therefore supplying crucial information to the CNS regarding how close one is to the end of the range of motion.
  • Ruffini endings are sensitive to capsular stretching with respect to speed and direction; this information complements that gathered by the Pascinian corpuscles.
  • Golgi ligament endings are sensitive to tension and stretch on ligaments, whereas free nerve endings (nociceptive and nonnociceptive) may respond to a variety of mechanical and biochemical stimuli (2,3).

The CNS cannot act without information upon which to base its actions, so efficiency of these joint receptors is of paramount importance in determining not only success, but injury prevention (e.g. knowing when to fire a muscle to decelerate a movement). For this reason, re-education of joint receptors should be an important focus in all rehabilitation and prehabilitation programs. The best way to train these receptors is to expose them to a wide variety of speeds, loads, and positions.

The last few paragraphs are just my two cents on the issue, so I suppose calling this one a “myth” is somewhat of a stretch.


Next month, I’ll cover five more myths that need to be banished from weight rooms for the rest of eternity. In the meantime, be leery of everything you hear from the self-proclaimed gurus at your gym.


1. Siff, M. Supertraining: 6th Edition. Supertraining Group, 2003.

2. Tiberio, D. Unpublished. 2004.