Friday, December 7, 2018

Does Doug Brignole Know Dip Physics?

In my last post I critically analyzed Doug Brignole's claims about squat physics.  I showed that although he bills himself as a biomechanics expert, in that article he made several basic mistakes in his analysis of squat physics that indicate that he did not have a good grasp of basic physics concepts when he wrote that article.

Brignole has also written a couple of articles on the biomechanics of dips, in which he claims that dips are not an effective exercise for either the pectorals or the triceps.  In this post I will show that he makes the same mistakes in these articles as he did in the squat article.  Moreover, I will argue that dips are a reasonably good pectoral exercise.  Further, after showing that Brignole's critique of dips as a triceps exercise is flawed,  I will explain the actual biomechanical reason that no multi-joint pressing movement is a very good triceps exercise.

Brignole's Flawed Analysis of Dips

In an article entitled "Evaluating Parallel Bar Dips as a Pectoral Exercise" Brignole wrote:

“The only way to stretch the pectoral fibers, is to cause the insertion of the pectoral muscle to move away from the origin of the fibers (located on the sternum).  This requires that we move the arm laterally - straight out to the side of the torso - away from the sternum. Conversely, the contraction of the pectoral muscles would require the insertion of the pectoral muscles (on the upper arm bone) to move maximally toward the origin of the fibers (located on the sternum).

“This is precisely what occurs when performing a Flat (prone) Dumbbell Press.  The upper arm swings out, away from the sternum - and then back toward the sternum.  Ideally - the goal is maximum range of motion.  So the wider the distance between the origin and the insertion (in the stretch position) - the better.  Likewise, the closer the distance between the origin and the insertion (in the contraction) - the better.  The Flat Dumbbell Press is - therefore - a good chest exercise for pectoral development.”
Brignole is correct that the pectoral insertion must move away from the sternum to stretch the pectoral muscle.  However, it is false that “This requires that we move the arm laterally - straight out to the side of the torso.”  Moving the arm into extension behind the body, as in dips, also moves the pectoral insertion away from the origin on the sternum, and also stretches the pectoral muscle.

Brignole continues:
“Ideally - the goal is maximum range of motion.  So the wider the distance between the origin and the insertion (in the stretch position) - the better." [bold added] 
“But that is not what happens during a Parallel Bar Dip.  Instead of having the upper arm bone move laterally - to the side of the torso - it moves more in a backward direction.  This is due to the fact that the bars are stationary.  They don’t move laterally - the way dumbbells move with us, out to the sides.  This forces are elbows to go back (posteriorly), instead of out (laterally).  So, even though we might be in the lowest (stretch) position, our pectoral insertion has not moved as much laterally (to the side) as it would have on a Dumbbell Press, a Butterfly Machine, a Cable Crossover, or even a Bench Press.  All of those exercises cause the upper arm bone to move outward - laterally (to the sides) - away from the sternum and the origin of the pectoral fibers.”
The pectoral insertion is fixed on the humerus.  Unless you detach the humerus from the joint, you can’t increase the maximum distance of the insertion from the origin, you can only change the orientation of the displacement, either to the side (abducted and externally rotated) or to the rear (adducted and internally rotated) of the body.

There is no law of physiology that requires that the arm move laterally in order to stretch or activate the pectorals.  Any action which moves the insertion of the pectoral away from the origins will stretch it.  When dipping, your arms move behind the torso.  Consequently, the insertion of the pectorals moves away from the origins, stretching the pectorals.  As the pectorals contract, the humerus is drawn from behind the body toward the sternum.

In fact, if you move your arms into the extended position achieved in dipping, then rotate the arm in the shoulder to assume the position of the bottom of the dumbbell bench press, you will find that the pectoral insertion on the humerus is for practical purposes in the same distance from the origin on the sternum. 


The main difference is that in the bench press position advocated by Brignole the arm is abducted and externally rotated.  There is very little difference in the length (stretch) of the pectorals.   In the following video I demonstrate that for practical purposes the length of the pectorals or distance of the pectoral insertion on the humerus from the sternum does not change as the arms move from the bench press bottom position to the dips bottom position.  


If anything, the dips involve a very slightly greater stretch.  This is due to the fact that the shoulder's posterior extension range of motion is greater than the transverse extension range.  When you bench press with the range of motion I demonstrate in the video above, you will notice a very distinct limit in the shoulder at the bottom; you may even experience discomfort as I do.  The elbow will not go further behind the torso until you adduct the arm (bring it closer to the body).  This is due to the intrinsic limit of the shoulder joint.  Hence, performing dumbbell bench presses in this fashion may not be the safest way to treat the shoulder.

Finally, the arm action involved in dipping is fundamental to using the arms to climb over obstacles or climb up trees or out of ditches, when you must push yourself upward with your arms on surfaces that do not move.  Since these are actions that would be required when navigating our ancestral habitat, I argue that the body evolved to do the basic dipping motion.  In contrast, during evolution, our ancestors probably never put heavy objects in their hands, and, lying on their backs, moved their arms as one does in a dumbbell bench press.  Certainly such action was not required for survival!  Hence, it is unlikely that the shoulder joint is optimally adapted to such an exercise.  I believe this is revealed in the fact that bench presses are a common cause of shoulder pathologies to the extent that one such pathology is called “bench presser’s shoulder.

Brignole goes on to claim that dips do not produce a strong contraction in the pectorals either:
“In the contraction phase of the Parallel Bar Dip, it's also less-than-ideal.  The best contraction of the pectoral muscle, occurs when we maximally shorten (flex) it.  This is achieved when we bring the upper arms forward, in front of our body, and toward the center.  This causes the muscle insertions (high on the upper arms) to move maximally toward the muscle origin (on the sternum).”
Although it may appear that the dumbbell bench press (or push ups on rings) will produce a greater contraction of the pectorals than parallel bar dips, this may not be the case.  First, the resistance curve of a dumbbell bench press is such that when the weights are crossing in front of the chest toward the sternum, the resistance to pectoral contraction is at its minimum.  The direction of the resistance (perpendicular to the ground) is 90 degrees out of phase with the direction of pectoral fiber contraction (pulling the arms together on the horizontal plane).  To load the pectorals, the load would have to be pulling the arms apart, but in a dumbbell bench press the load is balanced on the ends of the arms, putting little effective load on the pectorals.  Thus, the multi-joint exercise Brignole is advocating as “better than” dips fails to satisfy the very criterion he is using to criticize dips!

Moreover, the dumbbell bench press does not train the pectoral function of shoulder depression at all.  Shoulder depression produces a strong pectoral contraction.  In fact, if you simultaneously depress and internally rotate your shoulder – the position achieved at the top of parallel bar dips – you can produce an intense pectoral contraction similar to an arm cross motion against resistance, even though the pectorals have not maximally shortened.  In fact at the top of dips the pectorals are strongly recruited to keep the arms adducted and shoulder girdle depressed under the load (body).

The photo below clearly shows that the pectorals are strongly contracted when at the top of a dip, and well stretched when in the bottom position. 
Image source: Natural Aesthetic Bodybuilding
Every exercise has limitations.  Brignole himself advocates at least two exercises for the pectorals:  dumbbell bench presses and cable arm cross overs.  In my view, these two have similar ranges of motion.  Due to the mobility of the shoulder joint and multi-functionality of the pectorals, there is no one exercise that can effectively train all of those functions.  As I noted, the bench press does not train the pectoral function of shoulder depression as well as the bar dip (if at all).  I argue that if you perform bar dips and an arm cross over exercise (ring push ups or arm cross) you are training more pectoral functions than if you follow Brignole’s prescription. 

Brignole recommends the following exercise as a replacement for dips:


About this exercise, he writes:
"This cable movement runs parallel to the pectoral fibers (...as it should), provides better pectoral stretch than Dips, and provides better pectoral contraction the [sic] dips.  Plus, you can dial in the exact weight that feels right.  You're not obligate [sic] to use your entire bodyweight."
One major problem with this exercise is that it has limited loading potential.  The pectorals are a large and potentially very strong muscle.  Obviously many, many people can do dips with their entire body weight, and a good number can use well more than body weight.  Ironically, if you use this exercise that Brignole recommends instead, once you get strong enough to use a load equal to your body weight, you will not be able to do this movement,  When the external resistance and your body weight are the same, when you push on the handles you will lift your body off the floor and  it will turn into a dipping exercise!

Brignole continues:
“Interestingly, you’ll notice that - during a parallel bar dip - the upper arm bones travel along a pathway that is more parallel to the muscle fibers of the anterior deltoids.  And - sure enough - Dips hit the anterior deltoids MORE than they hit the pectorals, precisely for that reason.”
This is just plain wrong.  When dipping (concentric action), the main shoulder action is a combination of depression, flexion, transverse flexion, and internal rotation.

Shoulder flexion is a primary function of the clavicular head of the pectorals (upper pectorals) and the pathway of the humerus is aligned parallel to the upper pectoral fibers which are practically parallel to those of the anterior deltoids. 

Shoulder depression, transverse flexion, and internal rotation are all performed by the pectorals, not the anterior deltoid.

Moreover, the main functions of the anterior deltoid are shoulder abduction and flexion: raising the arm away from the side or above the shoulder from the front.  This is because the fibers of the anterior deltoid pull the humerus upward toward the clavicle where the deltoid originates.   Neither of these actions is involved in dips.

In dips, the load is pulling the shoulder end of the humerus downward.  To prevent this load from pulling the torso away from the humerus (i.e. separating the shoulder), something must counter this pull. 

The entire pectoralis major is primarily responsible for pulling the humerus forward and clavicle downward.  You can confirm this for yourself.  Put your left hand on your right pectoral.  Now, keeping your body upright, move your hand toward the floor, as if you were doing a one arm dip.  You will feel your pectoral contract strongly.  Now internally rotate your humerus (turn upper arm so that your elbow goes outward).  This is the upper position of dips and it produces a very strong pectoral contraction. 
Dipping Image Source: Brignole's Article; Force vectors and legend added.
Now do the same with your left hand on your right anterior deltoid.  You will find that the anterior deltoid does not contract.  Now raise your right arm above your head (arm vertical flexion).  You will find that your anterior deltoid strongly contracts. 

The anterior deltoid action of shoulder flexion is antagonistic to the requirements for performing a dip.  Due to the need for shoulder depression, the anterior deltoid is relatively quiet during dips.

The prime movers in dips are the pectorals and the anterior deltoid is only a weak synergist because dips do not involve the main actions of the anterior deltoid which are arm abduction and flexion.

Brignole's Flawed Analysis of Tricep Action in Dips

In his article entitled “‘Bench Dips’ for Triceps: Good or Bad ?”  Brignole also claims that dips, particularly bench dips, fail to provide any challenging load to the triceps. 

Here is his reasoning:
“In analyzing any exercise, one of the most important questions to ask ourselves is this: does the lever, which is operated by your target muscle, cross resistance?
“In this case, your target muscle is the triceps.  The triceps operates the forearm lever - meaning that it moves the forearm lever, by extending the elbow (note: the forearm lever is also operated by the biceps, but in the opposite direction).”
In this passage Brignole makes the same basic mistake he made in his article “Do You Know Squat.”  In discussing squat mechanics, he incorrectly alleged that the quadriceps can only move the lower leg, but in my critique of that article I proved that if the lower leg is held fixed, the quadriceps will move the upper leg.

Here he alleges that the triceps can only move the forearm.  If you fix the upper arm (don’t allow it to move) and contract the triceps, then, yes, the triceps will move the forearm to extend the elbow and bring it into alignment with the upper arm (humerus).  In this case the triceps’ insertion moves towards its origin (on the humerus and scapula).  This occurs in open-chain exercises such as the push-down or overhead elbow extension.

However, if the upper arm is held fixed, contraction of the triceps will move the upper arm to extend the elbow and bring the humerus in alignment with the forearm.  In this case the triceps’ origin moves toward the insertion.  This happens in closed-chain exercises such as push ups, bench presses, and dips.

Brignole continues:
“So here’s the initial question phrased a bit more specifically: does resistance (gravity, in this particular case, since there is no pulley or machine being used) cross the forearm lever?"
Here he confuses resistance with gravitational force and (perhaps accidentally) implies that gravity is not involved when using a pulley or machine.  In resistance exercise, gravity is always involved in the provision of the resistance unless the resistance is provided by hydraulics or some elastic medium like a spring or elastic band.  If body weight or external weights are involved, as in most pulleys and machines used in exercise, then gravity is involved in providing resistance.

However, gravity is not the resistance.  Gravity is a force that acts on matter to produce what we call mass or weight.  In the absence of gravitational force, no mass or weight is possible.  However, gravity itself is not mass or weight.  When you lift iron discs, are you lifting gravity or units of gravity?  No, you are lifting weights or masses which provide resistance only if in a gravitational field and not buoyed by a denser medium.

In addition, Brignole completely ignores the actual source of resistance in dips, which is the mass of the dipper’s body (plus any attached loading, whether weights, bands, etc.).  As shown in the figure below, the triceps are acting against the action of the load suspended at the proximal end of the humerus i.e. the body.  That load is acting to bend the elbow, which is the fulcrum of a third class lever, and the triceps act to straighten the elbow against this load.  Hence the triceps – actually, the two shorter heads of the triceps, see below – are in fact subjected to a load.

Dipping Image Source: Brignole's Article; Force vectors and legend added.

Brignole continues:
“Does the forearm lever interact perpendicularly, with gravity, during Bench Dips?  Answer: essentially - no.  Throughout the movement - whether you are in the ‘up’ position, or in the ‘down’ position - the forearm is almost entirely parallel to gravity.  A lever that is perfectly parallel to resistance is neutral, which means that the muscle that operates that lever is mostly unchallenged. [bold added]
“When you observe someone performing Bench Dips, you’ll notice that the upper arm lever does cross resistance.  A lever that crosses resistance is active, which means that the muscle that operates that lever is being fully loaded by the resistance.  During Bench Dips, it is the frontal deltoid that is doing most of the work, because it is the muscle mostly responsible for operating the upper arm lever in the pathway of this particular movement.”
He is correct that the forearm is parallel to gravity, and a neutral lever, when doing dips (and push ups and bench presses).  He is also correct that the active lever in dips (and push ups and bench presses) is the upper arm (humerus).

However, he is wrong that the triceps are not involved in moving the upper arm in dips, and he is also wrong that the frontal deltoid is doing most of the work.

As I stated and illustrated above, when the forearm is fixed, contraction of the triceps will move the humerus and any load attached to it.   Since the humerus (upper arm) is an active lever in dips, the triceps are in fact substantially loaded during dips.  The triceps is the only muscle that can straighten the elbow against the resistance that is bending the elbow and drawing the proximal end of the humerus (at the shoulder) toward the ground.

Hence, Brignole is confused.  By stating or suggesting that the triceps are “mostly unchallenged” because the forearm is parallel to gravity, Brignole has revealed that he most certainly does not understand the mechanics of this exercise, despite his claim to being a biomechanics expert.

Moreover, the more upright the torso is during the dipping motion, the longer the tricep moment arm and hence the more load on the triceps.  This is exactly what is accomplished in the bench dips Brignole is criticizing.

The figure below compares a parallel bar dip with torso leaning forward (sometimes called “chest dips”) and the bench dip with torso placed in front of the shoulders.  A forward lean places the line of resistance (R) between the shoulder and the elbow.  This results in the shoulder moment arm being longer than the elbow moment arm.  Consequently, the bar dip with the torso leaning forward directs the resistance toward the muscles involved in shoulder transverse flexion and depression, namely the pectorals.  On the other hand, the bench dip with the torso placed vertically below the shoulder minimizes the shoulder moment arm while maximizing the elbow moment arm, resulting in a greater load on the triceps.



The Real Reason Dips Aren’t Ideal For Training Triceps

All that said, dips, push ups and bench presses are not specific exercises for the triceps for a different reason. 

The long head of the tricep crosses both the elbow and shoulder joint.  During the concentric action of these exercises, the long head of the tricep simultaneously contracts at the elbow joint and stretches at the shoulder joint; this limits the contraction.  During the eccentric action of these exercises, the tricep must simultaneously stretch at the elbow joint and contract at the shoulder joint; this limits the stretch.  Consequently the long head of the triceps can neither stretch fully nor contract forcefully during these exercises.  This type of limitation is called active insufficiency.

The long head of the triceps has best length-tension when the shoulder is flexed and elbow is extended, as in overhead triceps extensions.  In short, dips, push ups and bench presses are not the best exercises for triceps development because they produce an unfavorable length-tension of the muscle, known as active insufficiency.

The other two heads of the triceps do contribute to elbow extension during dips and presses, especially when the torso is held more upright or in front of the shoulders as in bench dips. However, they are the smallest heads of the triceps.  Bench or upright torso dips are a poor choice for training the triceps because they address only the two smallest heads of the triceps.  You will then need to do another exercise for the long head.  This is not time efficient, and in addition since any exercise that properly trains the long head will also train the other heads, you may easily overtrain the two shorter heads of the triceps since they are typically a fatigue-sensitive muscle having a high ratio of type 2 ("fast twitch") fibers, and these heads are already doing some work in dips, push ups, overhead presses or handstand push ups, etc..

For efficient training and avoiding excessive training for the triceps one should choose a tricep isolation exercise that trains all three heads intensely at once.  The best is some variation of overhead extensions because the long head of the triceps is most efficient when the shoulder is flexed. 

Summary

Doug Brignole does have a good grasp of the mechanics of the dipping exercise as they apply to either the pectorals or the triceps.  He appears to have little or no grasp of the concept and importance of moment arm.  He asserts that dips are a poor exercise for the pectorals, claiming that the pectorals are neither fully stretched nor adequately contracted in performance of dips.  I have shown that these claims do not stand up to critical evaluation.

Although he correctly understands that dips are not an optimal exercise for triceps, his explanation, based on analysis of the leverage, is incorrect.  He appears to believe that the triceps can only move the forearm, when in fact, if the forearm is fixed, the two shorter heads of the triceps will act to move the upper arm.  He makes no mention of how the biarticulate long head of the triceps is put into active insufficiency in dipping motions.  

If Brignole makes these same flawed arguments in his forthcoming book The Physics of Fitness, I am surprised that he has obtained endorsements from people who should have a better grasp of biomechanics than he has displayed in his articles on the squat and dips. 



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