Resistance training for improving physical performance, aesthetics, and health does not need to be complicated. The vast majority of people can experience substantial progress in these three areas by consistently performing a few multi-joint exercises that train the major movement patterns. Variations of horizontal presses and pulls, vertical presses and pulls, squats, and hip hinges are certainly effective for strengthening and hypertrophying a large amount of muscle mass, but some muscles will be neglected to a rather meaningful degree. Consequently, we can use assistance exercises to fill in the gaps, but a sizable amount of muscle mass may still be neglected by the assistance exercises commonly selected by many lifters.
Identifying which muscles are or are not adequately overloaded by widely utilized multi-joint exercises can help guide efficient selection of assistance exercises due to the law of diminishing returns. As the set volume for a particular muscle group increases up to a certain threshold, the magnitude of the hypertrophic response will tend to increase in turn (31). Given that strength can improve through neural adaptations (e.g. enhanced motor unit recruitment), muscular hypertrophy is not necessary to experience an increase in strength (17, 35). Nonetheless, muscle size is a major contributor to maximal force production potential, and inducing muscle hypertrophy is of great value for achieving both long-term strength and aesthetic goals (12). You can read more about how strength is influenced by muscle size in Stronger By Science articles by Greg Nuckols. The relationship between training volume and hypertrophic adaptations certainly varies among different individuals and also among different time points in a lifter’s life. Nutrition, sleep, genetics, performance enhancing drug usage, prior training history, training frequency, exercise selection, proximity to failure during each set, and inter-set rest intervals all likely have the potential to impact how someone will be affected by changes in volume. This wide degree of possible variation can result in apparently contradictory research findings with regard to how volume influences hypertrophy.
However, I am confident in asserting that the law of diminishing returns applies to everyone with respect to volume’s effect on gains. At some point, increasing volume for a particular muscle group will result in only a marginal return relative to the time and effort required to perform the higher volume training, and no additional increases in muscle size or strength may be induced with further increases in volume (1, 24). For instance, many lifters who train their hamstrings twice per week may experience a meaningful benefit if they progress from performing three sets to six sets per session for their hamstrings. However, progressing from 10 to 13 hamstring sets per session may not result in any detectable benefit for the majority of lifters if sets are performed fairly close to failure and rest intervals are sufficiently long to mostly recover between sets. Some individuals may experience slightly greater progress with these very high volumes, while others may experience a slightly slower rate of progress if their recovery capacities are exceeded.
Rather than investing your finite time and energy into very high volumes for some select major muscle groups, you may achieve greater overall muscle growth through reaping the benefits of picking low-hanging fruit by performing a few sets of exercises that target otherwise neglected muscles. Even if the muscles that you allocate training volume toward are smaller than those whose volume is somewhat reduced, you can still experience a net increase in total body muscle mass due to the law of diminishing returns. For example, the calves are smaller than the quads, but performing three sets of calf raises might stimulate greater overall hypertrophy than three sets of hack squats if you already perform five sets of leg presses and five sets of leg extensions in your lower body training sessions, but you don’t currently do any calf training. In this case, adding more hack squats has the potential for some individuals to experience slightly greater quad development, but the magnitude of effect is likely eclipsed by the hypertrophic response that would be stimulated by the addition of three sets for the otherwise neglected calves.
Beyond contributing to a greater total body muscle mass, adding a minimal effective dose of volume for muscles which were previously not targeted may help enhance your resiliency by eliminating weak links and increasing stability of the joints they cross. A wide variety of muscles function isometrically as stabilizers during different movements, but these movements may provide a rather poor stimulus for increasing the size and strength of such muscles, particularly for people who are beyond the novice phase. For instance, the rotator cuff muscles help stabilize the shoulder joint while bench pressing, but bench pressing may not be an effective means of developing the rotator cuff muscles.
Let’s take a look at three commonly neglected movements that train muscles that may otherwise not be effectively targeted in many programs. Keep in mind that if you have not been consistently training some of these muscles, you likely can make meaningful gains with the addition of rather low volumes, such as performing two sets twice per week. A number of the muscles which will be covered lie deep to other muscles, so they will not be directly visible. Nonetheless, increasing the size of these muscles can still result in visible changes by increasing the total thickness of the region in which they are situated. For example, the rhomboids are nearly completely covered by the trapezius, but hypertrophying the rhomboids can result in a noticeable increase in upper back thickness.
The human body has over 600 muscles, many of which are quite small, so it would be nonsensical to advocate or discuss direct training for all of them. However, some of the muscles which may commonly go untrained are larger than you likely think and, when grouped together with other muscles performing the same function, they may constitute a sizable amount of total muscle with a meaningful degree of growth potential. To help understand the size of these muscles, the volume of lower body muscles will be compared to the volume of the gluteus maximus (the largest lower body muscle), while the mass of upper body muscles will be compared to the mass of the lats (the largest back muscle), just to give you a point of comparison (8, 36).
If you add a low volume of one exercise for a particular movement into your program, I recommend selecting a variation that provides a meaningful amount of tension to the exercise’s prime movers in a stretched position. A growing body of evidence indicates that doing so can allow a muscle to experience stretch-mediated hypertrophy (13, 16, 25, 30). As a result, partial ROM exercises performed at short to moderate muscle lengths may be suboptimal for inducing hypertrophy compared to a full ROM or partial ROM exercise which loads a muscle at long peak lengths. For each of the three movements that will be discussed in this article, I will mention a variety of possible exercise variations because not everyone has access to the same training tools, but keep in mind that selecting an exercise that applies tension to the working muscles in a stretched position will likely be optimal.
Scapular Protraction
The serratus anterior and pectoralis minor produce scapular protraction – forward movement of the shoulder blade (6). Together, the mass of these muscles has been measured to be 9% greater than the lats, primarily due to the serratus anterior, which has a volume just 10% smaller than the lats (36). Before I ever read through the actual data on the sizes of different muscles, I would have never imagined that the serratus anterior is this large, and consequently, that the absence of any scapular protraction exercise in my program resulted in such a sizable amount of muscle mass being neglected. The serratus anterior also plays a major role in maintaining a functional and healthy shoulder by upwardly rotating the scapula as the arm is elevated to enable full range of motion of the shoulder (20). Weakness of this muscle may contribute to the development of scapula winging, a painful disorder characterized by a protruding scapula which restricts shoulder mobility and strength (14).
You can directly target the serratus anterior and pectoralis minor with multi-joint exercises that incorporate scapular protraction into a horizontal press, or with a single joint exercise where scapular protraction exclusively occurs. The “pushup plus,” where scapular protraction is performed during the concentric phase of a pushup while scapular retraction occurs during the eccentric phase, is a viable means of loading these muscles at the same time as the pectoralis major, triceps, and the deltoid’s anterior (i.e. front) head. If you do not yet have the strength to achieve full scapular protraction during the standard pushup plus, you can use a modified version where your hands are placed onto an elevated surface such as a bench. If this variation is too difficult, you can further regress the intensity by performing the movement against a wall with a forward lean of the torso. Similar to the pushup plus, you can also add scapular protraction to a cable or elastic band horizontal press to train the serratus anterior and pectoralis minor with a multi-joint exercise. Alternatively, you can perform scapular protraction as its own exercise by utilizing either your bodyweight or an external load provided by cables or elastic bands. In these instances, you would assume the same starting position as the aforementioned multi-joint exercises, and perform the same scapular movement without motion occurring at the shoulder or elbow joints.
Pushup Plus
Bodyweight Scapular Protraction
Cable Scapular Protraction Press
Cable Scapular Protraction
Dual Cable Scapular Protraction
You can also perform a pure scapular protraction exercise or a multi-joint scapular protraction exercise with free weights when lying down on your back in the supine position. In contrast to the other variations, a supine scapular protraction exercise can restrict dynamic scapular range of motion if the scapula contacts the ground or bench before full retraction occurs.
Supine Dumbbell Partial ROM Scapular Protraction
Supine Dumbbell Partial ROM Scapular Protraction Press
While this may inevitably occur if the exercise is performed bilaterally, you can perform a unilateral variation with a dumbbell in a manner that enables a greater scapular retraction ROM. To do so, you would maintain a back arch and a fully retracted position for the scapula on the side that is not being trained.
Supine Dumbbell Full ROM Scapular Protraction
Supine Dumbbell Full ROM Scapular Protraction Press
A scapular protraction exercise performed through a partial ROM from a resting to protracted scapula position can certainly be used to strengthen and hypertrophy the serratus anterior and pectoralis minor. Nonetheless, I recommend finishing the eccentric phase of each rep in a position of full scapular retraction in order to load these muscles at long lengths where stretch-mediated hypertrophy may be induced.
Hip Flexion
Hip Flexion, which is the forward movement of the thigh, is performed by the iliacus, psoas major, rectus femoris, tensor fasciae latae, and sartorius, which collectively constitute a volume of muscle approximately 12% greater than the gluteus maximus (7, 8, 19, 26).
When the hip is in a low angle of flexion, the adductor longus and pectineus, which together have a volume that is 27% of the gluteus maximus, also have rather favorable moment arms for flexing the hip (7, 8, 19, 26). A muscle’s moment arm is the perpendicular distance between the line of force a muscle produces and the rotational axis of the joint upon which it acts. Torque is the product of a force multiplied by a moment arm, so a muscular moment arm quantifies the leverage a muscle has for generating torque in a particular plane of motion and consequently its ability to contribute to a joint movement. When the hip is near a neutral position, the adductor brevis and to a lesser degree the gracilis can also secondarily assist in generating hip flexion torque while exhibiting a combined volume that is about 24% of the gluteus maximus (8, 19, 26). As the hip flexion angle increases, the moment arms these four hip adductor muscles have for flexing the hip steadily decrease, so they will likely no longer be effectively trained as hip flexors once the angle of hip flexion exceeds 30° (7, 26).
A very similar relationship exists between hip flexion torque and the angle of hip flexion, such that maximal hip flexion torque peaks near a neutral hip position and progressively declines at higher angles of hip flexion (4, 9). Consequently, strength at high angles of hip flexion will likely be the limiting factor during a hip flexion exercise unless the resistive torque steadily decreases as the angle of hip flexion increases throughout the concentric phase of the exercise.
Some abdominal-focused movements such as hanging leg raises or reverse crunches can involve both hip flexion and trunk flexion simultaneously and are therefore a viable means of training hip flexor muscles and the rectus abdominis (i.e. the “six-pack” muscle) at the same time. An advantage of these exercises is their accessibility, because bodyweight alone can provide a sufficiently challenging level of resistance for many individuals. Due to its ability to provide peak resistive torque near a neutral hip position, the reverse crunch may effectively train a greater amount of muscle mass than a hanging leg raise where peak resistive torque occurs at 90° of hip flexion if full ROM reps are exclusively utilized. During the initial 30° of hip flexion where the hip adductor muscles can meaningfully contribute to generating hip flexion torque, resistive torque is minimal during a hanging leg raise but maximal during a reverse crunch. A possible method to amplify hip adductor muscle stimulation during a set of hanging leg raises is to perform progressively shorter ROM reps after you can no longer perform full ROM reps due to fatigue accumulation. If you terminate the set once you can no longer reach a high degree of hip flexion, the hip adductor muscles may be suboptimally stimulated. However, if you continue the set until you can no longer achieve even a low degree of hip flexion, all of the hip flexor muscles may be effectively targeted. You can readily adjust the intensity of hanging leg raises to your current level of strength by altering your knee angle. Compared to a flexed knee position, an extended knee position provides a greater magnitude of resistive torque during this exercise by shifting the body’s center of mass further out in front of the hip and trunk. Consequently, you can progress by decreasing the angle of knee flexion used for this exercise over time.
Hanging Leg Raise
Reverse Crunch
On a side note, it is worth mentioning that exercises like reverse crunches and hanging leg raises are sometimes performed with a technique that causes hip flexion to be the only dynamic joint action that is trained. If trunk flexion does not occur during these exercises, the rectus abdominis will still be activated, as it functions isometrically to resist the anterior pelvic tilt, which may otherwise be produced by contraction of the hip flexor muscles. For some individuals with prior injuries that result in discomfort or pain being experienced when flexing the lumbar spine, this technique may be preferable to one that utilizes dynamic trunk flexion. Like dynamic training, isometric training certainly has the potential to induce muscle hypertrophy if it provides a potent enough stimulus to the working fibers (23). To my knowledge, the research examining changes in muscle size after similarly designed dynamic or isometric resistance training interventions is limited to just two studies, neither of which assessed trained subjects (10, 27). They reported different outcomes after using rather dissimilar training protocols and have a combined age of 98 years, so a firm conclusion cannot be reasonably drawn from the available evidence. I am skeptical that merely resisting anterior pelvic tilt during a hip flexion exercise would be as effective in inducing rectus abdominis hypertrophy as an exercise which includes dynamic trunk flexion, particularly for trained individuals. However, empirical data on this matter is presently lacking.
When opting to utilize a single-joint hip flexion exercise, a multi hip machine can be a very useful tool due to its ability to apply resistance in an extended hip position with a readily adjustable load that facilitates incremental progression. Alternatively, you can use ankle weights or elastic bands to perform hip flexion exercise from a supine (i.e. lying on your back) or standing position. While hip flexion exercise may also be performed from a seated position, this variation would not be my first choice due to it training less overall muscle mass.
Multi Hip Hip Flexion
Lying Ankle Weight Hip Flexion
Lying Banded Hip Flexion
Seated Ankle Weight Hip Flexion
Hip Abduction
In a neutral hip position, hip abduction, which is the movement of the thigh out away from the midline of the body, is primarily produced by the gluteus medius, gluteus minimus, and tensor fasciae latae, which together have a volume equivalent to 58% of the gluteus maximus (8, 18, 19, 26). The sartorius, piriformis, and rectus femoris also assist with abducting the hip and collectively have a volume that is 56% of the gluteus maximus (8, 18, 19, 26). Similar to how greater hip flexion torque can be generated near a neutral hip position compared to a moderately high degree of hip flexion, maximal hip abduction torque peaks in an adducted hip position and decreases as these muscles shorten with increasing angles of hip abduction (2, 11, 21, 22, 29, 38).
Additionally, as the angle of hip flexion increases, the hip abduction moment arms of the gluteus medius and gluteus minimus steadily decline until these muscles can no longer contribute to producing hip abduction torque when the hip flexion angle nears 90° (7, 26, 37). In contrast, hip abductor moment arms of the piriformis, obturator internus, and gemellus superior increase as the hip flexes to the extent that they function as primary hip abductors in 75-105° of hip flexion (7, 26, 34). These muscles belong to the short hip external rotator group, which as the name suggests, externally rotates the hip when the hip is in or near a neutral position (19). The changes in muscular moment arms that occur at different angles of hip flexion will result in some hip abduction exercises training a meaningfully greater amount of muscle mass than others. While the piriformis, obturator internus, and gemellus superior help stabilize the hip joint, they are rather small with a collective volume equivalent to approximately 10% of the gluteus maximus (8, 39). Together the gluteus medius and gluteus minimus have a volume which is five times greater than these muscles, so a hip abduction exercise performed with close to 0° of hip flexion will target a noticeably greater amount of muscle than a hip abduction exercise performed with close to 90° of hip flexion (8).
The tensor fasciae latae, rectus femoris, and sartorius can generate hip abductor torque at either 0° or 90° of hip flexion (7). However, the tensor fasciae latae is quite small with a volume which is about 8% of the gluteus maximus, and the rectus femoris and sartorius have meaningfully better leverage for producing other joint movements such as hip flexion (8).
My recommendations for selecting a hip abduction exercise mirror those previously discussed for hip flexion exercises. For the sake of maximizing training efficiency, I recommend selecting a hip abduction that involves close to a neutral hip position, if you opt to perform only one hip abduction exercise. Consequently, an exercise using a side lying or standing position would be preferable to a seated hip abduction exercise for training the greatest amount of muscle. This is not to say that seated hip abduction exercises are bad by any means. They simply target less total muscle mass than other variations.
For the same reasons that a multi hip machine is a very effective implement for training hip flexion, so too is it very well-suited to train hip abduction. With a slightly flexed hip position, you can use this machine to train the hip abductor muscles in a stretched position which may be difficult to achieve with other exercises. Similar to hip flexion, you can also use ankle weights or elastic bands to perform a hip abduction exercise in a standing or side-lying position.
Multi Hip Hip Abduction
Side Lying Ankle Weight Hip Abduction
Side Lying Banded Hip Abduction
Additionally, you can train hip abductor muscles without the need for any equipment through side plank variations. The exercise can be completely isometric in nature if the side plank position is statically maintained, which requires the hip abductor muscles nearest to the ground to act isometrically in order to prevent the pelvis from dropping. If the standard version where the elevated foot remains on top of the bottom foot is too challenging, you can regress the intensity by placing your knees or both feet on the ground. Alternatively, you can progress the intensity by keeping the top hip in an isometrically abducted position or by dynamically abducting and adducting this side while the bottom hip abductors continue to function isometrically.
Side Plank Regression
Side Plank Progression
Enhancing isometric hip abduction strength may be particularly advantageous to strength athletes who perform loaded carries and/or walk out heavy squats such as strongmen and powerlifters who compete without a monolift. At any moment when only one foot is in contact with the ground, the hip abductors which are on the same side as the stance limb must stabilize the pelvis by functioning isometrically to resist pelvic drop in the frontal plane (19). Successfully doing so during a squat walkout, farmer’s walk, or yoke walk with maximal or near maximal loads can be a considerable challenge, and insufficient hip abduction strength may limit performance (15). Even if an athlete possesses the minimum amount of hip abduction strength required for a squat walkout, further enhancing hip abduction strength may still be beneficial for some powerlifters. Instead of struggling to perform a maximal walkout, an athlete may feel psychologically encouraged in his/her ability to complete a squat if a reserve of hip abduction strength is present and the walkout requires less relative effort.
Programming Recommendations
If you do not have experience performing any of these three movements and now wish to incorporate some or all of them into your resistance training program, I recommend that you begin doing so by adding a low volume, such as two sets for each movement twice a week. Untrained individuals have been measured to experience significant strength and hypertrophic adaptations by performing a single set of an exercise to volitional fatigue 2-3 times per week (5, 32, 33). Even if you have been consistently resistance training for many years, muscles which have not been effectively loaded by the exercises you have been performing may still respond to the addition of direct training in a manner similar to a novice.
None of the exercises for these three movements impart meaningful axial loading and most of the muscles which function as prime movers during these movements do not act as prime movers for commonly performed multi-joint exercises. Consequently, adding a low volume of the aforementioned movements is unlikely to interfere with your current training, and you can readily integrate the exercises which train these muscles into any session, or even an active recovery day. While adding a couple of sets of these movements at the end of an existing workout would not require much extra time training, it could still extend the time commitment for a session and impose an opportunity cost. To get the most out of your finite training time, you can incorporate these movements into a dynamic warmup or non-competing supersets along with other exercises. If you have a low work capacity and are not accustomed to these techniques, you may notice a minor reduction in performance on some of the pre-existing exercises in your program when you initially incorporate these new exercises. However, any interference will likely subside as your work capacity improves, after you acclimate to using these methods for a few weeks.
With a non-competing superset, you can perform a set of one of the three movements after completing a set of another exercise training different muscles. For instance, you can directly follow a bench press set with a hip abduction set during the rest period before the next bench press set. If you use rest intervals which are sufficiently long to recover between sets, this technique should not require any additional workout time or reduce the quality of the exercises already included in your training program. You can also utilize non-competing giant sets when you sequentially perform sets of three or more exercises which target different muscle groups. For instance, you can include a barbell row, hip flexion exercise, and scapular protraction exercise together in a giant set which targets a large amount of muscle mass in a brief period of time.
The main constraint that may present in non-competing superset and particularly giant set exercise selection is equipment availability. For instance, if you train in a busy commercial gym, utilizing a barbell, multi hip machine, and cable station for the aforementioned giant set example may provoke ire among other lifters. If you crank up the volume in your headphones, avoid making eye contact with other humans, forgo the application of deodorant, and aggressively talk to yourself between sets, the likelihood that someone will approach you and interfere with your giant set will be substantially minimized. Alternatively, you can utilize variations which require only one piece of shared equipment for a giant set. For example, you can perform a barbell row, reverse crunch, and pushup plus together without needing multiple types of equipment.
In addition to including the three movements into supersets/giant sets, programming them into a dynamic warmup is an efficient strategy. As the name suggests, increased body temperature is a key benefit of a general warmup due to the favorable physiological effects that result in enhanced force production and oxygen delivery (3, 28). While 5-10 minutes of low intensity aerobic exercise can induce this increased temperature, so too can a low volume of some of the exercises discussed in this article with the added benefit of hypertrophying and strengthening some otherwise neglected muscles. You can use any of the three movements as part of your dynamic warmup, but you may find that hip flexion and hip abduction are particularly suitable to begin a lower body workout, and scapular protraction works similarly well to start an upper body session.
With a scapular protraction press, such as the pushup plus, strength of the serratus anterior and pectoralis minor will be the limiting factor rather than strength of the pectoralis major, triceps, and deltoid’s anterior head when proper technique is used. Consequently, even if you perform sets of this exercise until technical failure (i.e. when full scapular protraction can no longer be achieved) during a dynamic warmup, these pressing muscles should not be meaningfully fatigued for subsequent pressing exercises.
Conclusions
Regardless of where they are implemented, I recommend adding a low volume of some of these exercises to your program if increasing whole body muscularity and strength is a goal of yours. Scapular protraction, hip flexion, and hip abduction may not be the most popular movements, nor would I consider them to be indispensable components for most resistance training plans to be effective. Nonetheless, they can provide the distinct advantage of targeting a notable amount of muscle mass that may otherwise go neglected and allow you to reap the benefits of picking these low-hanging fruits from the tree of gains.
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The tensor fasciae latae anatomy image was published in Henry Gray’s Anatomy of the Human Body (1918), is in the public domain, and can be found at https://commons.wikimedia.org/wiki/File:Gray430_with_TensorFasciaLata.png.
The short hip external rotator muscle anatomy image was created by Beth O’Hara, is licensed as a Creative Commons work, and can be found at https://commons.wikimedia.org/wiki/File:Posterior_Hip_Muscles_1.PNG.
All other muscle anatomy images were published by “BodyParts3D, © The Database Center for Life Science”, are licensed as Creative Commons works, and can be found at http://lifesciencedb.jp/bp3d/.
