As was mentioned previously in the "Workout of the Week" email, our shoulder joints are complex beasts...And in turn, the muscles that control action at this joint (the deltoid complex) have to be universally functional to keep up.
Let's run through a quick anatomy refresher:
1) The deltoids (delts) are made up of three main subdivisions: the anterior (front), lateral (side) and posterior (rear) heads.
2) While each has their own specific plane that they dominate, the muscles fibers all funnel down into the same attachment point which is what creates that beautiful "diamond" separation that we all know and envy.
3) Because of this common insertion and near-360º of fiber arrangement around the joint, it is safe to say that we can consider the delt complex as having a "sum>parts" relationship.
4) Due to the pliability needed to control the ball-and-socket shoulder joint, our delts are designed specifically to withstand a TON of volume of work while having minimal fiber lengthening via stretch (this reduces the potential for muscle damage).
So now that we have gotten that out of the way, where do machine laterals fit into this equation and why are we interested in overloading the eccentric?
At a basic level, maximizing hypertrophy means being able to effectively overload all aspects of a joint's range-of-motion as well as the the muscle's fiber lengths.
Think of the quads for example; we can train the lengthened position of the fibers by performing reverse Nordic curls, the mid-range with a squat, and the shortened range with machine leg extensions. With the quads, we have an advantage with programming due to how we can stagger and bias exercise selection and execution depending on our goals and desired stimulus.
Bringing it back to the delts, we can effectively refine our potential overloading exercise patterns down to overhead press and raise variations (yes I know there are more but stick with me here)...But even within these options, it's hard to really classify the overhead press as strictly a delt pattern due to the reliance on the triceps, traps and, to a lesser degree, the pecs. This leaves us with lateral raise variants and other exercises that could fall into the category of "abduction of the shoulder."
Now, I don't know about you, but I can think of about a million different ways that I can raise my arms. Every subtle angle, rotation, lever length, and change of torso positioning results in a new stimuli. Granted, there is going to be a lot of cross-over and 90% of these aren't even going to be worth doing, but this just goes to show how unique our delts actually are.
We have a muscle group that works in every plane, can handle metric tons of volume and is structurally resistant to damage.
Now you can see how creating a program to truly maximize the growth potential of the delts is going to quickly run into logistical issues due to not being able to extract much stimulus per unit of volume...We have to increase this somehow.
In strolls the Machine Lateral!
Returning to the quads example, being able to overload different aspects of the muscle we're targeting is crucial to our success. With our machine lateral, the tension being distributed to our delts is going to be even from the start of the rep to the end, and we're going to be working within stable conditions with no energy being wasted due to inefficiencies. Contrast this to a standing DB lateral which places no demand on the delts at the bottom of the rep (where we are strong), some demand in the middle of the ROM (where we are strongest) and the max demand at the top of the rep (where we are the weakest). It's pretty clear which variation/modality will have the best stimulus-to-volume ratio.
We should now be able to extrapolate that, under equivalent conditions, the machine lateral is going to beat out pretty much every other delt movement in ability to propagate hypertrophic outcomes. This is great news and all, but we're not satisfied just yet...there is more stimuli extraction to be done.
It's time for our partner to shine!
Though we can comfortably and easily control eccentrics with machine laterals in a way that free-weights (and even cables) aren't optimized for, we are still not able to get that elusive stretch through our delts at the bottom of the ROM. If you weren't aware, loading a muscle under stretch (think of a stiff leg deadlift) is a driver of hypertrophy that is relatively independent from the primary mechanisms that we tend to design our programs around (mechanical tension, metabolic stress, etc). And muscle groups that are architected in a way that subjects them to greater forces under stretch have a slight advantage when it comes to possible growth vectors. The delts, unfortunately, are not in this category, so we have to think outside the box on how we can simulate the stretch-under-load conditions which are characterized by microscopically sheering muscle fibers (don't worry, this is a good thing in moderation).
Having our partner add even resistance to the eccentric is our golden ticket!
Before you come out guns blazing, let's set some ground rules for how to approach this technique:
1) Choose a load that would be hard for 15 normal reps.
2) Perform the concentric on your own and then have your partner apply pressure ONLY during the eccentric.
3) The resistance should be strong and consistent from top to bottom, but it should NOT be an isometric. The goal here is a controlled 5 count eccentric.
4) As fatigue sets in, the partner will have to adjust their pressure to account for the delts' reduced force output. When this pressure is reduced by 50% from the initial, the set should be over. Ideally, this should fall between 4-6 reps.
5) Because the idea here is to create additional muscle damage, this technique should be used intentionally and sparsely.
It should now be apparent just how large of a role the partner will play in this. Make sure to evaluate this position in the same way you would look for a trusted spotter; if they look like they would let you get stuck under a bar while spotting, they probably aren't a great fit for eccentric-overloading here. But if you can find that special someone, be prepared to have your delts (and mind) blown by this technique!