I’ve been reading about this idea that different exercises that target the same muscle groups not only develop different muscle groups to different extents, but that they also develop those muscle groups in different ways.
i.e. one twin who never does anything other than chins for their lats will have not only different sized lats than their bro who only does rows for their lats, but the two people will also have somewhat different shapes to their muscles as well.
is this broscience bs y/n?
Evidence desperately needed.
Yes.
I mean… if doing 20 chin ups made my social breadth wider does it count?
In a general sense: yes, some literature indicates that muscle shape can adapt to exercises that are modified in specific ways.
However, it is a fairly unreasonable assumption within the context of the question as it was asked because the question does not specify contraction type, range of motion, or external resistance type - only exercise selection. Due to the exact phrasing of the question: no, performing either of the specified movements will not cause muscle shape changes unique to the movement itself. This would only be true if the movement also involved modification to the contraction type, range of motion, or external resistance of the movement.
Okay so just to be 100%, crystal clear, you’re saying that when chris beardsey was talking about “regional hypertrophy” in “strength is specific”, he was not implying that you would see differences in regions of the muscle adapting AT ALL on the basis of exercise selection alone, but only on the factors you mentioned?
The only inherent difference is the range of motion difference due to the extra shoulder flexion involved with chin-ups, which I will define as being done with wrists supinated and hands gripping the bar at approximately shoulder width.
Per the AAOS, there is a full 240º of movement available between the extremes of shoulder flexion (180º) and shoulder extension (60º), which is what we should consider as the true full range of motion available for training the lats, since the lats perform shoulder extension (and therefore eccentrically control/resist shoulder flexion).
Purely based on my eyeballs (so take this as you wish) it is rare that trainees perform the chin-up with around 170º of shoulder movement. Their shoulder rarely passes 170º of flexion since their humerus usually ends up at some point in front of their ear due to torso angle - humerus directly beside their ear is usually 180º of flexion on the average person, meaning that the torso and arms would be in a straight vertical line. Their humerus rarely passes a textbook neutral position (directly at their side) when the lats are maximally shortened due to the chin-up bar preventing further movement. It is very possible that anthropometric differences and implements used to perform this movement can cause individuals to utilize more or less than my estimated 170º on this movement, so I think a very fair estimated range of motion figure for this movement would be a maximum of 170-190º.
Purely based on my eyeballs (so take this as you wish) it is rare that trainees perform a row with more than 150º of shoulder movement. Assuming that the trainee will perform this movement in a strict fashion, their shoulder rarely passes 90º of flexion (humerus at the height of the shoulder joint). Assuming that the trainee will be performing this movement to maximum shoulder extension (elbow behind the torso as far as possible), they might achieve 60º of shoulder extension. It is very possible that anthropometric differences and implements used to perform this movement can cause individuals to utilize more or less than my estimated 150º on this movement, so I think a very fair estimated range of motion figure for this movement would be a maximum of 150-170º.
Not only do neither of these movements train the lats through their full available range of motion, but I question the ability of this extra 20º (roughly) of movement to produce any meaningful amount of regional hypertrophy considering that the data on this topic involved individuals performing knee strengthening exercises with an extra 40º of movement (McMahon et al., 2014). This is almost double the range of motion difference that I have estimated for this discussion.
But, those are just my estimates and conclusions. Train however you think is best in accordance with your interpretation of the best available data.
References
McMahon, G. E., Morse, C. I., Burden, A., Winwood, K. & Onambélé, G. L. (2014). Impact of range of motion during ecologically valid resistance training protocols on muscle size, subcutaneous fat, and strength. The Journal of Strength & Conditioning Research, 28(1), 245-255.