We’ve brought up the concept of exercise variations several times on social media and we always get an interesting result. Reponses are typically split, with half of the responders saying variation is unnecessary and the other half swearing by its importance. The group that aren’t fans of variation often state that progressive overload is the only necessity when making gains and cite all sorts of fitness websites or trainers to support their claim. And that statement certainly isn’t false. However, they’re missing out on the full definition of progressive overload, so let’s start the discussion there.
What is Progressive Overload?
Many often think that progressive overload is simply an increase in weight, however, that’s just one facet of progressive overload. According to strength and conditioning mastermind, Dr. Tudor Bompa, there are actually 6 ways to create progressive overload (12):
- Change Loading Patterns – this is simply increasing weight.
- Change Contraction Type – this can be done by performing heavy eccentrics or pausing reps.
- Change Contraction Speed – this is done by either performing a movement incredibly slow or incredibly fast.
- Change Equipment – this can be done by moving from dumbbells to a barbell to handle more weight.
- Change Training Phases – this can be done by changing your entire training program to focus on a new goal
- Change Exercises – this is actually Bompa’s second method but I placed it at the end for greater dramatic effect. Yes, changing exercises is a major form of progressive overload!
So, what would the haters say now? Progressive overload is definitely necessary to make further gains – but! Exercise variation is a form of progressive overload! Strength and conditioning legends, Dr. Steven Fleck and Dr. William Kraemer, also include exercise variation as a key component in their discussion on the methods of progressive overload (26) Fleck and Kraemer also offer a distinguished difference between progressive overload and progressive resistance. Progressive resistance is just increasing weight, but progressive overload is increasing the stress of a given exercise by any means possible (26) – much like the list given above. If you want to argue with the likes of Bompa, Fleck, and Kraemer, be my guest. But that wouldn’t be a wise decision, now would it?
Okay, so the gods of strength and conditioning research all agree that variation is important, so let’s go over why this is the case.
Why is Variation Important?
It’s first worth pointing out that individual adaptations to a training program can greatly differ. Studies have shown that subjects undergoing a training program experience different levels of strength and size gains even though they performed the same protocol (1,52). This is reason alone to add different exercises to your program – maybe you don’t respond well to certain exercises or rep ranges and need to do something different.
In addition, studies have shown that varying exercises is more effective for strength gains than simply performing the same exercise over and over again (27). We know that mechanical tension is the # 1 stimulus for growth (51), and a stronger muscle will able to produce more force and experience more tension which will lead to greater growth in the long term. We see this shown in studies that find a strong correlation between muscle strength and muscle size (2).
The most important reason to add variation for bodybuilders, however, has nothing to do with strength. As we’ll touch on more in a minute, almost every exercise variation for any given body part will force activation patterns of the muscle to change. Studies have shown that the most activated portion of a muscle in a given exercise will grow the most in a long-term program (7,53). This is due to the fact that almost every muscle can be divided into neuromuscular compartments in which differing portions of specific compartments will be activated during certain exercises (7). These different levels of activation almost always lead to what researchers term, “regional hypertrophy,” or, “nonuniform hypertrophy,” in that the most active compartment of a muscle in any exercise will grow the most (7,52).
We’ll get more into that in a second, but let’s first talk about some other aspects of exercise variation that people often overlook when considering variation.
Changing an exercise doesn’t always mean you’re inducing a biomechanical change – that’s just one form of exercise variation. You can also change the repetition speed, weight used, repetition number, range of motion, and rest period length to induce specific adaptations. This is outlined by the SAID Principle, which stands for, “Specific Adaptations to Imposed Demands.” These changes are more physiological in nature, but variation is variation, right?
Repetition Speed is one way to add variation to an exercise without changing anything mechanical. This can be done by performing speed squats or tempo squats rather than normal squats. Studies have shown that speed squats will promote more power development and will cause the trained muscle to retain more Type IIx muscle fibers (40). However, performing slower reps will increase strength more than power and is more likely to promote hypertrophy when performed with enough weight/fatigue (30). Both methods are still technically a squat, but each will promote different adaptations and constitute as variation.
Changing the weight used or repetition number during an exercise is another form of variation that can also promote different adaptations. We’ll talk about both of these at the same time since they’re highly related – heavy weights will force lower reps and vice-versa. Taking heavy weights and light weights to failure will result in similar hypertrophy gains, however, using heavy weights will increase strength to a greater degree while lighter weights will improve endurance more so (44). Therefore, doing squats with heavy weights vs lighter weights is technically the same exercise from a mechanical standpoint, but each loading pattern induces a very different stimulus for adaptation. Therefore, load variation is still technically a form of variation within the same exercise.
Changing the range of motion of an exercise is another method of variation that could also be considered both a form of progressive overload and exercise variation. We all know that you can use more weight in a quarter squat as opposed to a deep squat, and the same idea applies to a rack pull or floor press compared to a deadlift and bench press, respectively. This increase in weight is obviously a progressive overload, but interestingly enough, size gains are also specific to the range of motion used. Greater range of motion almost always results in greater overall size gains; however, partial range of motion movements can also offer regional hypertrophy benefits. One study found that deep squats were better for developing the entire quadriceps, especially the distal portion closer to the knee. On the other hand, partial squats were just as effective at promoting gains in the musculature closer to the hip (10). Why is this the case?
Greater range of motion movements will more than likely promote longitudinal muscle hypertrophy, which involves an increase in muscle length. This is why deep squats promote better gains in the distal quad. However, shortening the range of motion so that the muscle is working in a shortened state can also promote gains based off of the shape the fiber is in while it’s producing force. Partial squats will cause the quads to produce force in a shortened state which means the fiber is more bulged than elongated – this can actually result in specific adaptations to increase muscle fiber diameter (myofibrillar hypertrophy) whereas reps in an elongated state increase muscle fiber length (9).
Lastly, the SAID Principle heavily applies to the functionality of an exercise. Studies have shown that movements that emphasize horizontal hip extension (like hip thrusts) are better for improving tasks that involve this joint action, like broad jumps and sprinting. However, movements that involve vertical hip extension (like squats) are better for increasing vertical jump height (19). These findings underline the importance of movement variation for athletes when multiple skills have to be developed at once. If you only squat to increase hip strength, you’re likely not going to see optimal gains in sprint or broad jump performance.
So, the point has basically been driven home. Exercise variation is not just biomechanical; altering the physiological stress of the exercise by changing reps, speed, weight used, or rest period length can all influence exercise adaptations – and routinely making all of these changes is necessary for long term gains. However, we now have to appease all of the bodybuilders who have sat through all of the boring strength and conditioning talk. Let’s go over how important movement variation is for promoting full development of all the major muscle groups.
How Can Variation Affect Gains?
What we’re going to do in this section is touch on all of the major muscle groups and the research into their many movement variations. It’ll be easy to see how certain muscle groups can be affected by different exercises and how important this may be for overall gains when considering regional hypertrophy and the Law of Accommodation.
The Law of Accommodation (when considering lifting) simply states that the adaptation to a given exercise will diminish over time and eventually stop all together if you continue doing the same exercise (12). So, with the concepts of regional hypertrophy and the Law of Accommodation in mind, how should we add variation to each muscle group?
It’s always funny when we hear people say that variation is pointless, yet their chest workouts always involve using decline, flat, and incline angles for flyes and presses. Guess what, sucker? That’s variation! Studies have consistently shown that changing the angle of a bench press can change regional activation in the chest, with incline angles attacking the upper chest and flat/decline angles emphasizing the lower chest (31). Grip width can also alter activation patterns, with close grip bench hitting the upper pecs more (8) and wide grip bench offering more lower pec activation (32). Since we know that regional activation is associated with regional hypertrophy (53), it’s obvious that movement variation is important for full chest development.
In addition to mechanical variations, changing repetition ranges is also an effective method for training the pecs. Studies show the pecs consist of about 60% fast twitch fibers (47). This means they should mostly be trained with heavier weights and longer rest periods, but they’ll also be very prone to metabolite accumulation which makes them a great candidate for training methods that maximize metabolic stress.
For full chest development, movement and load variation are absolutely necessary.
Interestingly enough, grip widths or hand placements during pull-ups/pulldowns don’t really change maximal activation readings in the lats. However, these alterations can change the pattern of activation and the muscle moment arm so that certain portions of the lats are contributing to force production either at different joint angles or for shorter/longer period of time based on what grip type is used (21). So, the lats might be one muscle group that tons of variation isn’t absolutely necessary for, but the lats also probably have the greatest variety of exercises that you can use to destroy them.
This effect is also similar when comparing rows to pulldowns – both offer similar maximal activation levels for the lats, however, each angle will induce a different activation pattern or muscle moment arm that may place certain muscle compartments under greater tension at differing joint angles or for longer amounts of time (33). In addition, the lats are about a 50-50 split between fast and slow twitch fibers (47) so using a wide repetition range is smarter than restricting yourself to the 8-12 rep range all of the time.
The traps, on the other hand, are another muscle group that many will train at several angles for optimal development. The middle traps are best activated during horizontal rows (33) whereas the upper traps are more active in shrugs, upright rows (37), and deadlifts (16). The lower traps are most activated in pull-ups or pulldowns (6), so using a wide variety of pulling exercises is necessary for full trap development. In addition, the traps are mostly slow twitch fibers, with about 60-70% of the muscle being slow twitch (29). Therefore, using high reps for the traps is a great strategy, but going heavy occasionally can also present a new stimulus for growth.
Recall that individuals can show a great variety of responses to a training program – some make gains while others don’t (1). This is an important idea to remember when planning back training – maybe certain grip types, machines, or exercises just don’t offer the best training stimulus FOR YOU and your individual biomechanics. Add variation to your training to see which exercises YOU respond best to.
The shoulders have an insane range of motion and, therefore, are activated during just about every upper body exercise. Interestingly enough, bench press variations and overhead press variations all offer similar activation in the front deltoid muscle (8). However, using free weights as opposed to machines also increases medial deltoid activation more due to the increase in stability requirements (13), so use both methods according to your goals on that day.
Shoulder activation also differs between using dumbbells and barbells for overhead press, with dumbbells offering slightly more activation (41). However, more overall weight can be used with barbell presses, so both variations are necessary when considering progressive overload. In addition, greater weight can be used in the seated overhead press as opposed to a standing press, however, a standing press will also offer more core activation, so, again, pick variations according to your goals!
The rear deltoids are also active during pulldowns of various grip widths (46), however, isolating the rear deltoids with dumbbells or machines is going to be a better method of achieving maximal activation. The shoulders are one group where a massive amount of variation is pretty tough – there’s only so many ways you can do an overhead press. In addition, the shoulders are heavily involved in benching motions as well.
Regardless, variation is still important in shoulder training as any seasoned vet knows that the shoulders are the most common overuse injury site in bodybuilders (24). Changing equipment type, pressing angle, and repetition ranges can help keep these issues at bay – which is incredibly important for long term boulder shoulder gains.
As far as biceps exercises go, studies have shown that changing the angle of your shoulder joint during a curl can change the activation patterns of the biceps. So standing curls, preacher curls, and seated incline curls all involve different activation patterns and achieve peak mechanical load at different positions in the range of motion (4). This means that for full biceps development, you need to train them at various shoulder angles.
As far as the triceps go, studies have actually shown that all three heads of the triceps fatigue at different rates (3). This means that each head of the triceps probably consists of a different percentage of slow vs. fast twitch fibers and, therefore, needs a wide range of repetitions for full development. In addition, research has found that changing shoulder angle also alters triceps activation in various exercises (11). The greater flexion angle your shoulder is in, the greater activation you can expect out of the triceps long head (34). This means that overhead triceps movements will be best for targeting the long head of the triceps, while movements with elbow closer to the ribs will target the other heads better.
Studies have also shown that the triceps are highly active in both flat and decline bench press, but not as much during incline bench (8). In addition, using a barbell offers more triceps activation than benching with dumbbells (42), so if your goal is to build your triceps, focusing on barbell bench variations may be a better idea. Again, all sorts of angles and equipment types need to be used for full development!
Both the biceps and triceps groups are fast twitch-dominant (47), meaning they’re best trained by heavier weights and low-to-moderate reps. However, they’ll also be very prone to metabolite accumulation, so metabolic stress methods should also be used.
The glutes are an interesting muscle group because studies have found that they are highly active during squats, with deeper squats being most effective for maximizing activation compared to parallel or quarter squats (14). However, if you want to maximize glute activation, you need to be performing movements where the glutes are most active at the top of the exercise (54). This occurs to a greater degree in deadlifts compared to squats, but to a maximal degree in hip thrusts (17).
As far as variations are concerned, increasing your stance width and turning your toes out on squats can increase glute activation compared to normal stances (39,49), however, you can probably squat deeper in a more normal stance. In addition, you can also place your feet higher on a leg press sled to get a little more glute activation (20), but it’s probably not the best movement for the glutes. If you love your banded glute walks, band placement can also alter glute activation levels and patterns (15), so don’t be afraid to use a wide range of those as well.
Movements emphasizing a wider stance or utilizing bands at the ankles or knees will also likely offer preferential growth to the upper glutes. This is due to the fact that the upper glute area primarily consists of the glute medius muscle which is a primary mover for hip abduction and external rotation – both of which are occurring in wide stance movements and band walks.
The glutes are mostly a slow twitch muscle group (45), so they’ll probably be best-developed using higher reps. However, heavy weights will also present a new stimulus for growth. Squats of all stances should be done as deep as possible, while deadlift variations and hip thrust variations are necessary for optimal glute development.
The quads are best-trained with squat and lunge variations. Front squats and back squats offer similar activation levels and patterns; however, front squats cause this with much less weight required (18). Front squats will also offer a greater challenge to the mid- and upper back due to the load placement, so these can be a great option for improving overall strength. Not surprisingly, free weight squats offer more quad activation than Smith machine squats (5), however, Smith machine squats can still be a great mind-muscle connection builder and are also great when you’re beat up from free weight training.
Squat stance can also increase or reduce glute involvement depending on stance width (39) which can, in turn, alter activation patterns in the quads. Reducing glute involvement by adopting a narrower stance will increase tension on the quads during a squat and vice-versa. However, a wide stance will offer more activation for the outer quad (39), so multiple stance widths need to be used for full quad development. Ultimately, whatever stance allows your torso to stay the most upright throughout the movement will likely be your best quad builder, so experiment with variations until you find this position. Ankle mobility can also play a role here but that’s outside the scope of this piece.
In addition, lunges have been shown to increase outer quad activation to a greater degree than squats (22), so adding lunge variations to your program is necessary for improving your quad sweep. In addition, performing leg press with one leg at a time has also been shown to increase activation in the tear drop muscle (vastus medialis) more than using both legs (50). Single leg movements are absolutely necessary for attacking individual quad muscles and helping add balance to your legs.
Leg extensions are also necessary for building the middle quad muscle as it is not overly active during squats or lunges (22). Turning your toes in or out can also change activation patterns during leg extensions (48), so be sure to add variation to even the simplest of exercises.
It’s pretty easy to see that movement variations are important for full quad development. You can definitely build a solid set of wheels on squats alone, but squats will also offer very little hamstrings development. And, annoyingly enough, even though squats don’t really build the hamstrings, hamstring strength can be a massive limiting factor in squat strength (38). Therefore, adding hamstrings isolation movements to your program is necessary to build your squat.
Lastly, the quads are pretty close to a 50-50 split when concerning fiber types (28). This means that a wide repetition range should be used to maximize development in both the slow and fast twitch fibers.
The hamstrings are the last muscle group we’ll cover here. The hamstrings are incredibly interesting when it comes to movement variations. The hamstrings exhibit something called, “preferential activation,” due to the fact that they cross both the hip and knee joint, but perform opposing actions at each (43). This is why they’re not overly active in a squat – they are performing opposing actions at the hip and knee and don’t really change length to a great degree during squats, lunges, or leg press. Deadlifts appear to be the best compound movement for building the hamstrings as they rely much more on hip extension than knee extension and, subsequently, cause much more hamstrings activation (36). However, loaded knee flexion doesn’t occur during the deadlift, so doing deadlifts alone will not optimize hamstrings development.
Like we said before, the hamstrings can be preferentially activated. This means that movements like leg curls and glute ham raises will preferentially activate the lower half of the hamstrings while exercises like good mornings and RDLs will activate the upper hamstrings to a greater degree (43). So, if you want full hamstrings development, you have to perform both types of movements!
Lastly, the hamstrings are, again, about a 50-50 slow twitch-fast twitch fiber split (23). This, again, means a large repetition range can (and should) be utilized for maximizing development.
Now that the proverbial dead horse has been beat, I think it’s pretty clear that movement variation is incredibly important for maximizing muscular development. A very major takeaway from this piece is that movement variation is a form of progressive overload – moving to new or more difficult exercises can create a new stimulus for growth and strength gains (12,26,51).
Lastly, if you have ever performed an incline bench press, changed your squat stance, or performed preacher curls, you have done an exercise variation. Exercise variations do not have to be fancy inventions with all sorts of moving parts and resistance types. Changing angles, equipment, repetition speed, repetition range, rest period length, and range of motion can all be considered exercise variation as they all impose a unique stimulus for growth and adaptation.
Ultimately, adding variation to your program can keep things from getting stale. The minute you get bored and complacent is the minute you stop making progress. Keep things interesting and keep progressing!
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From being a mediocre athlete, to professional powerlifter and strength coach, and now to researcher and writer, Charlie combines education and experience in the effort to help Bridge the Gap Between Science and Application. Charlie performs double duty by being the Content Manager for The Muscle PhD as well as the Director of Human Performance at the Applied Science and Performance Institute in Tampa, FL. To appease the nerds, Charlie is a PhD candidate in Human Performance with a master’s degree in Kinesiology and a bachelor’s degree in Exercise Science. For more alphabet soup, Charlie is also a Certified Strength and Conditioning Specialist (CSCS), an ACSM-certified Exercise Physiologist (ACSM-EP), and a USA Weightlifting-certified performance coach (USAW).