Barbell Medicine - From Bench to Bedside

Debate around how deep you should squat is one example of a range of motion (ROM) controversy. Range of motion (ROM) can be defined as the degree of movement occurring at a specific joint during an exercise (Pallares 2021). Range of motion can be increased or decreased by altering aspects of positioning such as stance or grip width, using equipment such as pins or boards, or altering the start/end position of an exercise.

Range of motion is assessed by examining joint movement and the lengthening/shortening of target musculature from the start of the movement until the end. For example, we can measure the range of motion at the elbow joint in a biceps curl. An individual can use a larger ROM by flexing the elbow (“curling”) from a fully extended position (180*) until the forearms contact the upper arm, whereas they could reduce the ROM by curling from the same start position to just 90*, or even starting from 90* and then curling until the forearms touch the upper arm.

The ROM used in training influences muscle adaptation. These adaptations include the way muscles generate force, the range of positions available for improved force production, joint stability, and the architecture of the muscle itself, among others. Marusic 2020 While the definitions of “full” and “partial” ROM vary depending on the exercise and goals of training, the important point is that we can distinguish between longer ranges of motion that take the joints (and involved muscles) through their complete physiologic range, and partial ROMs, which involve a smaller portion of the total available ROM for a given joint.

So which is better: deep squats (full ROM), or squatting to 90 degrees (partial ROM)? In this article we’ll explore the evidence on the topic, and then provide some practical recommendations.

ROM Considerations for Strength

Strength describes muscular force that is measured or demonstrated in a specific context. Improvements in muscular strength result from both neurological and structural changes. There are many different types of strength based on the unique demands of an activity. Certain competitive sports have defined standards for minimum ranges of motion, e.g. the hip crease must come below the top of the knee during a squat in powerlifting. That being said, there doesn’t seem to be a single “best” ROM for general purposes. Additionally, since multiple lines of evidence show that strength adaptations are specific to the joint angle trained, it is plausible that a larger range of motion may offer the widest range of benefits, whereas shorter ranges of motion can be incorporated for sport-specific demands. Kitai 1989 Thepaut-Mathieu 1988 Lindh 1979 Weiss 2000 

Let’s take a closer look at the data here:

In support of larger ROM

  • Bloomquist et al., 2013 showed that deep squatting leads to significant improvements in both shallow and deep squats, whereas shallow squats only significantly improved shallow squats.
  • Pallarés et al., 2019 found that full squats lead to greater improvements in full, parallel, and half squat 1 rep maxes than either parallel or half squat training.
  • Hartmann et al., 2012 showed that quarter squat training did not lead to significant improvements in vertical jump performance, but deep back and front squats did. 

In support of partial ROM

  • Rhea et al., 2016 showed that quarter squats led to greater improvements in sport skills such as maximal speed and jumping power in highly trained athletes.
  • Kubo et al., 2019 found that half squats are more effective for improving half squat 1 rep max and full squats are more effective for improving full squat 1 rep maxes. In other words, squat strength is specific to the range of motion trained.

Taken together, these results suggest that full squats are more effective for strength development over a greater ROM, and thus contribute to a larger general base of physical adaptations. However, that doesn’t mean that partial ROM squats should never be programmed.

Strength adaptations are specific to range of motion, movement velocity, contraction type, muscle lengths, joint angles, and many other variables.. The more similar an exercise is to the strength ‘test’, the more transference there is likely to be from training in that fashion. We’d therefore expect partial squats – particularly those that mimic a vertical jump’s joint angles, velocity, etc., to have more transference to a vertical jump performance than squat variants that are less similar. In other words, squatting to 90 degrees may be superior to full depth if the goal is to enhance sports skills such as sprinting and jumping, due to greater joint-angle and velocity specificity. Rhea 2016 McBride 2002 

It’s worth noting that studies such as Pallarés et al. (2019) contradict the findings of Rhea et al. (2016) despite utilizing similar methodologies. Pallarés et al. (2019) used a 10 week protocol that started at 4 sets of 8 at 60% 1RM and progressed to 5 sets of 4 at 80%1RM in a linear fashion (in other words, number of repetitions decreased as load increased). Meanwhile, Rhea et al. (2016) used a daily undulating periodization sequence (same exercise, different loading depending on the day) where subjects progressed from 8RM, 6RM, 4RM, to 2RM, and then back to 8RM. Both of these strategies would likely better be suited for increasing low velocity strength given the proximity to failure and load selection for each set. Indeed, the velocity of the exercise must also reflect the demands of the sport. Behm 2012 

A potential explanation is due to the differences in training status of participants between studies. For example, similar improvements in power, velocity, and jump height have been observed in relatively untrained individuals when exposed to heavy strength training or high velocity specific training. Cormie 2010 Rhea et al. (2016) studied college athletes who squatted 1.39 times bodyweight on average, while the subjects in Pallares et al. (2019) squatted 1.14 times bodyweight on average. It’s possible that no significant differences were observed between groups because the subjects were relatively less-trained, and would exhibit less benefit from higher specificity training. Ultimately, I’d chalk up the discordant results to interindividual differences between subjects.

A program better suited for developing the sport skills such as sprinting and jumping would likely involve at least some training with a load that maximizes the power output. Cormie 2011 Wilson 1993 Loturco 2018 For the squat, this is likely around 30-70% of an individual’s 1RM. Soriano 2015 While the total volume (sets x reps) required to drive adaptation will vary between individuals, sets should be divided such that velocity loss across a set is minimized if the goal is to maximize muscular power. Weakley 2019 In sum, the loads used and subsequent velocity loss likely observed were not appropriate for improving power, thereby making conclusions about ROM less significant.

We should also consider the training status of the individual when deciding what ROM to employ. Those who are newer to resistance training are likely to respond more robustly to a given stimulus, perhaps reducing the need for very specialized training. Ahtiainen 2003 Latella 2020 Ribeiro 2015 For example, untrained individuals can increase muscle mass simply by walking. Konopka 2014 For individuals who are newer to resistance training, the focus should be more on developing a wide base of physical adaptations rather than hyperspecialization.

Overall, we expect that greater similarities in properties such as ROM, muscle length, movement velocity, contraction type, etc., the greater the transference between a given exercise and the strength “test”. However, when one or more of these is altered, it may have unexpected effects on the desired outcomes. Ultimately, range of motion may depend on each person’s style and preferences, and will also likely change over time. While there are constraints for range of motion that guide us when choosing exercises for strength, it’s important to consider the individual’s response and preferences. 

ROM Considerations for Hypertrophy

Muscular hypertrophy is an increase in the size of an existing muscle fiber. There are two plausible mechanisms by which a longer ROM may augment hypertrophy. First, a larger ROM involves more muscle mass, thereby increasing training economy by driving more hypertrophy per rep or exercise. Second, as mechanical tension is one of the primary mechanisms driving muscle anabolism, stretch imparted on the muscle fiber with longer ROM would result in greater hypertrophy. Let’s see what the data show here:

In support of Full ROM

  • Pinto et al., 2012 showed that training the biceps through a larger ROM (0*-130* flexion) lead to greater increases in muscle thickness compared to partial ROM (50*-100* flexion)
  • McMahon et al., 2014 found that a training program comprised of back squats, knee extensions, leg press, Bulgarian split squats, and lunges  exercises trained through a larger ROM (0-90*) lead to greater increases in quadriceps muscle size compared to a shorter ROM (0-50* knee flexion)
  • McMahon et al., 2013 showed that performing the barbell back squat, leg press, Bulgarian split squat, and forward lunge through a larger ROM provides better long-term retention of training adaptations compared to shorter ROM. 
  • Kubo et al., 2019 found that training the back squat through a full ROM (0*-140*) led to significantly greater increases in muscle volume of the adductors and gluteus maximus compared to a partial ROM (0*-90*). Of note, there was no difference in the volumes of quadriceps muscles with the full squat (4.9 ± 2.6%) and partial squat (4.6 ± 3.1%).
  • Bloomquist et al., 2013 demonstrated superior increases in quadriceps growth of full squats (0*-120*)compared to shallow squats (0*-60*). 

In support of partial ROM

  • Oranchuk et al., 2018 found that isometric training (no change in muscle length) at longer muscle lengths (the initial ROM of a leg extension where knee is mostly bent) elicited greater increases in muscle size (1.16% per week with angles >70*) compared with isometric training at shorter lengths (the end ROM of a leg extension where knee is more straight; 0.47% per week with angles ≤60*. See photo below.)
  • Pedrosa et al., 2021 showed that partial range of motion leg extensions at long muscle lengths produced larger increases in muscle size than full ROM and partial ROM at shorter muscle lengths. Further, training the quads at longer muscle lengths appears to cause more muscle growth at more distal regions (towards the knee in this case).
  • Goto et al., 2019 demonstrated that partial ROM through the mid-range of the barbell lying triceps extension produced superior increases in muscle size (48.7 ± 14.5%) compared to the full ROM group (28.2 ± 10.9%).

Does this mean that full ROM squats are superior for hypertrophy than squatting to 90 degrees? If the goal is strictly to maximize lower body growth, it appears so. Overall, the data suggest a fairly consistent relationship between larger ROM, muscle length, and hypertrophy outcomes, both total and regional. Given the superiority of a larger ROM for exercises like squats and leg extensions, I would opt for as close to a full ROM squat as an individual can perform consistently. For most people this will likely fall somewhere in between 90* and full depth, but if the goal is to maximize hypertrophy across the whole muscle, or in the largest amount of musculature possible, larger ROM is your best bet. However, some recent research has shed light on potential applications of partial ROM training for hypertrophy.

At a high level, we can describe a muscle as either “lengthening” (eccentric) or “shortening” (concentric) during a movement. We can further define “complete” ROM as fully lengthening and shortening, and “partial” ROM as neglecting a significant portion of either the lengthening or shortening.  Partial ranges of motion carried out at longer muscle lengths (i.e., initiating the movement in the stretched position and terminating it before fully shortening it) likely produce superior results compared to those carried out at shorter muscle lengths, and may produce similar results compared to full ROM (refer to figure above for how a partial ROM at longer muscle lengths would look for the biceps curl). However, given the paucity of evidence we advise against utilizing partial ROMs for a significant portion of training, and opt for working the muscle through the majority of its available ROM whenever possible.

ROM Considerations for Pain/Injury

We now understand that pain is a complex experience that involves many more variables than just the status (or damage) of the tissues. Cohen 2018 The experience of pain can be influenced by a number of biological, psychological, and social/environmental factors that are collectively referred to as biopsychosocial factors. Moseley 2007

Having many degrees of freedom of movement is likely beneficial, as we want people to be competent in a variety of movement options for completing tasks. As such, we don’t want to completely avoid training or exposure to certain movements, ranges of motions, or positions that folks may face in sport or life. In situations where someone has pain or sensitivity with a specific position or movement, the goal is to pick exercises that are somewhat “threatening”, but tolerable.

For example, if a deadlift from the floor causes significant pain in an individual’s lower back, but they can tolerate a “hinge pattern” by doing block pulls from below the knee, then we might start there and progressively lower the blocks to increase tolerance to the movement. A caveat here is that the weight on the bar needs to be managed in a way that doesn’t elicit intolerable symptoms. For a more in-depth discussion of pain science and managing pain in training, check out the article Austin wrote here.

In favor of full ROM

  • More degrees of freedom for completing tasks
  • Increased capacity to tolerate exposure to a variety of stimuli

In favor of partial ROM

  • Allows individual dealing with pain to modify training to manage symptoms

Using a larger ROM exposes the musculoskeletal system to a wider range of stimuli (e.g., joint angles, muscle lengths, and positions), which likely offers additional capacity to handle whatever challenges are thrown our way during both athletic endeavors and everyday life. Meanwhile, partial ROM training can be useful to allow an individual to continue training while dealing with pain/injury. However, the goal should be to gradually work through larger ranges of motion until the individual is no longer restricted and the desired capacity is restored. We prefer a wide range of movements, positions, and therefore ROM too, as focusing too much on a particular movement (or collection of movements) can lead to an increased risk of overuse injury. Campbell 2021 In other words, building proficiency in a wider variety of tasks reduces overuse injury risk and provides more options for completing tasks. 

So which is better for dealing with pain and injury: full ROM or squats to 90 degrees? If an individual experiences pain when squatting below 90 degrees (but not to 90 degrees), then it may make sense to incorporate partial ROM squats for a time. The movement should also be repeatable, efficient, and meet the points of performance imposed by yourself, a coach, or the sport. For example, if the individual in question is a competitive powerlifter, they will have to work towards depth that meets the powerlifting requirements. This will likely involve gradually squatting deeper, with or without equipment such as boxes or pins, which can help in these contexts by providing physical cues and/or offloading the weight at a certain point in the movement. Ultimately, we want to introduce variation that reflects the individual’s preferences, performance needs, and what they can tolerate.

Taken together, working towards a relatively large range of motion for a variety of exercises will allow an individual the most options for performing both everyday tasks and movements in the gym. However, utilizing partial ROMs may allow someone to continue to train in a manner that is tolerable when dealing with pain. If somebody is not dealing with significant symptoms, then our general recommendation is to perform all training with a relatively large ROM.

ROM Considerations for Health

Strength training results in both general and specific health benefits, where health can be defined as “the ability to adapt and self-manage in the face of social, physical, and emotional challenges.” Huber 2011 Indeed, there is a strong correlation between physical strength and reduced risk of all-cause mortality across the lifespan. Volaklis 2015 Stamatakis 2018 Ortega 2012 Ling 2010 Li 2018 

Resistance training is unique in that it drives relatively large increases in force production and muscle size while maintaining or improving bone mineral density. Egan 2013; Hughes 2018 While these adaptations in physical capacity allow us to maintain a better quality of life throughout our lifespan, it’s tough to know whether a larger ROM is better than a shorter ROM when it comes to health. Let’s once again look at the data:

In favor of full (in this case, some) ROM

  • Neves et al.,  2021 found that dynamic resistance training led to improvements in bone mineral density and reductions in bone loss while isometric resistance training did not.
  • Wang et al., 2019 showed that there is a strong association between muscle mass and health, so you could argue in favor of larger ROMs as a means to develop more muscle mass. However, having more muscle mass does not seem to provide more protection from carrying too much body fat Knowles 2021
  • Developing more degrees of freedom for completing tasks can allow for more physical independence as we age

In favor of partial ROM

  • Baz-Valle et al., 2019 shows that adherence to a program is improved with self-selected exercises, so if somebody will adhere better to a program with a shorter ROM, then I would opt for that. 

To my knowledge, there’s no evidence directly examining the effects of different ranges of motion on longitudinal health outcomes, so for now we should probably assume the null, i.e., that there aren’t significant differences from small changes in ROM — unless taken to the extreme, such as a program composed solely of isometric contractions, or only performing movements through a quarter of the available ROM.

So what’s better for health: full ROM or squats to 90*? In this case, I don’t think it would make much of a difference, particularly if the individual is engaging in other exercises that train the legs through more of the available ROM. There is likely an inflection point where differences in ROM do make differences in outcomes, but where that falls depends on the outcome being discussed. The definition of “health” presented by Huber (2011) emphasizes the individual’s ability to adapt to and self-manage physical challenges. Training through a larger ROM extends the unique benefits of resistance training to a larger range of physical capabilities, thereby increasing the number of options we have for completing tasks. Ultimately, this allows us to maintain a higher degree of physical independence as we age and engage in tasks that are meaningful to us for longer. Combined with the association between muscle mass and health, and the relationship between larger ROM and lean mass accretion, training through a larger ROM likely offers more benefits than a smaller ROM.

There are many different ways to get these benefits that lead to the breadth of adaptations that come with resistance training, but as far as it pertains to ROM considerations, we want to use a relatively large ROM most of the time. With that said, we should temper our confidence in this claim until more data compare different ROMs on meaningful health outcomes.

Summary

Hopefully now that you’ve read this article (and not just skipped to the end) you understand the major flaw in typical squabblers arguing about “the one correct way to squat”. Range of motion should not be viewed as a black-and-white issue; in reality it’s a nuanced topic warranting the consideration of several factors. Since strength is specific to the joint angles, movement velocity, and contraction type, the ROM must be adequate to meet the demands of the sport. Some sports may benefit from training that emphasizes shorter ROMs with appropriate loads for executing movements quickly, while others require larger ROMs to train the stretch-shortening cycle. Similarly, given that training through larger ROMs tend to produce greater increases in muscle size compared to shorter ROMs, the majority of hypertrophy training should be carried out through larger ROMs, with the caveat that partial ROMs performed at long muscle lengths may provide similar benefit. 

For individuals dealing with pain during movement, we want to select a ROM that is somewhat threatening, but is tolerable. For these individuals, full range of motion squats may not be feasible. Ultimately, this exposure allows us to maintain more degrees of freedom and options for completing tasks. While you probably shouldn’t engage in a purely isometric resistance training program (nor is that practical for most people), the importance of ROM is unclear as it pertains to meaningful health outcomes. However, given that training through a relatively large ROM offers the most benefit for strength and hypertrophy and allows us a wider breadth of options for completing tasks, that would be our recommendation.

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