Why Is Range Of Motion Important? A Guide By Dr. Arthur Lynch

A Guide By Dr. Arthur Lynch

// Introduction

Muscular strength, defined as the ability to exert force under a given set of conditions (1), is an important attribute for performance across many sporting contexts (2).  Measures of muscular strength have been shown to correlate highly with several indicators of sporting performance (2), including sprint speed, jumping performance, change of direction ability and power output across a variety of sports (3,4,5). Also, increasing muscular strength through strength training has been shown to positivity impact these same indicators of sporting performance (6,7,8,9,10).

The performance enhancing effects of strength training are not exclusive to strength and power sports, but also help to improve performance in  endurance sports too (11,12). It’s this link between strength training and indicators of sporting performance that forms the basis of strength and conditioning for improving sports performance. The quantitative nature of strength (in other words, the numerical data that strength testing provides) lends itself well to monitoring over time (i.e. can you lift more weight now than you did when you last tested?). However, certain strength tests can be prone to a lack of standardization, especially where range of motion (ROM) in the exercise that is being tested. Manipulation of ROM can confound testing results and ultimately questions whether or not the athlete has actually improved strength or the test is just under different circumstances. There is a considerable amount of evidence to suggest that greater performance adaptations are achieved where longer ranges of motion are utilised in strength training. The aim of this article is to highlight why ROM standardization in strength testing is important and why a lack of standardization is more pervasive then you might have otherwise thought. As an added extra, the article will also highlight the possible advantages of using longer ranges of motion during strength training.

// The Importance Of Standardization - An Analogy

Let’s say you decide to test your 100m sprint time.

Following a period of time, you retest your sprint time and find that you were able to complete the test in a faster time. However, you go on to discover that the person timing your sprint forgot to start the stopwatch until after you left the start line. You’re quite obviously frustrated, and you’re now  unsure as to whether or not you actually improved on your sprint time, or whether the lower number on the stopwatch we’re purely down to tester error. Essentially, this is what happens when you don’t standardize the ROM in your strength testing.

// Standardising Range Of Motion In Strength Testing - Focusing On The Squat

Whilst ROM standardization is an important consideration during strength performance testing, for the purpose of this article I’m going to focus on the one repetition maximum (1RM) squat - one of the events in the sport of Powerlifting and a very common strength assessment within the field of strength and conditioning. In addition, (and based on the available literature), getting stronger in the squat has been shown to correlate with improved performance in a number of sporting tasks,(6, 7, 10) which highlights the potential usefulness of the squat as a training exercise, as well as the need to conduct the 1RM squat assessment properly. The 1RM squat is a good model to use here, as this test is particularly susceptible to ROM manipulation (we all know that one guy who tries to half squat their way to higher numbers, right?). This can be the fault of the athlete/subject (i.e. the tendency amongst some to reduce the ROM as the weight on the bar increases). Alternatively, the coach or experimenter can be to blame too.

ROM manipulation in the squat is often the result of the athlete reducing their squat ROM (also referred to as squat “depth”) in an attempt to lift more weight. Additionally, it can also be the fault of those conducting the test. This is an issue that plagues powerlifting, where different “interpretations” of what ought to be a fairly easily understood rule (that the crease of the hip must drop below the top of knee) are observed between (and sometimes within) federations. In fact, it could be argued that this is also an issue within the scientific literature too, where squat depth can vary substantially.

And this creates an issue...

If a modified squat depth is used within a particular study and the depth is specified (often with the visual aid of an image depicting what the particular squat depth looks like), then it’s easy for the reader to interpret and understand what that actually means. The research is transparent. Frustratingly, this is not always the case though, and it’s not uncommon for researchers to provide a somewhat vague definitions of modified squat depth. To illustrate this point, check out Table 1. Some of the operational definitions are not only vague, but suggest squat depth criteria wasn’t  precise.

// If This Is An Issue At The Level Of The Scientific Literature, Is It Any Wonder That It Is An Issue In Practice?

Note that full knee extension = 0° of knee flexion. Results displayed as mean values with the standard deviation in brackets. * no standard deviation was provided.

// So, Why Does This Actually Matter? Let’s Break This Down…

// Relative Muscular Effort

At this point you may be thinking “so what? Why does this really matter?”. Figure 1 is taken directly from a paper by Bryanton et al. (21). It documents the influence of squat depth and barbell load at a given position in the entire squat ROM on the relative muscular effort of the knee extensors (i.e. your quadriceps). Notice how profound of an effect squat depth has on the relative muscular effort of the knee extensors? Similar results were observed for the hip extensors in this particular study, whereby the relative muscular effort was greatest in the deepest squat position. Practically, this makes sense and explains why athletes would be inclined to cut depth, because squatting deeper is harder! For training purposes, the data also suggests that squatting deeper may in fact provide a more robust stimulus to the knee extensors leading to greater performance gains.

Figure 1 - The effects of barbell load at varying squat depths A) and squat depth at varying barbell loads B) on knee extensor relative muscular effort (Taken from Bryanton et al. 2012).

// Inflating The True Performance Value

Ramping up the values is likely the most important consideration with regards to ROM standardization in the squat. Referring back to Table 1, it’s not uncommon to see different squat depths compared within the same group of subjects (e.g. full squat vs. partial squat). Modifying the 1RM squat ROM in this way leads to pretty large differences in 1RM values. This highlights just how important it is to standardize squat depth. As previously discussed, using a shorter ROM can allow you to lift substantially more weight. Now, some of the comparisons outlined in Table 1 are somewhat extreme, but still useful to illustrate the point. For example, Bazyler et al.(15) reported mean 1RM values of 152.21 kg and 223.27 kg for the full and partial squat respectively, so almost 50 % more weight was lifted in the partial squat. However, the partial ROM only required subjects to achieve 80° of knee flexion in the bottom position, which is quite a short ROM. What’s more likely to happen  in practice is a slight reduction in depth in an attempt to lift more weight - again, we all know those who cut depth to add a few pounds on the bar. How much 1RM inflation that leads to will depend on the individual, how much they cut depth by etc. Nevertheless, these studies do highlight the influence of squat depth on weight lifted in the 1RM squat test.

// Bottom Line? Hit Full Depth!

// Training Adaptations

So far the focus has been almost exclusively on squat depth standardization as it relates to strength testing, with little to no mention of how ROM affects training adaptations. However, there is evidence in support of adopting  deeper squat depths for the purpose of improving overall performance. Hartmann et al. (6) compared the adaptive response to 10 weeks of full ROM back squat, full ROM front squat or quarter ROM back squat training in a group of male and female subjects. Whilst strength was improved to the greatest extent in the movement that was trained by the respective groups (an example of specific adaptation to imposed demands maybe), it was observed that subjects who performed either full ROM back or front squats achieved significant increases in squat jump and counter-movement jump performance, with no improvements observed in those who only performed quarter ROM back squats.

Here’s another example. Bloomquist et al. (17) compared 12 weeks of either deep (120° of knee flexion) or shallow (60° of knee flexion) back squat training and observed superior results in the deep squat training group for increased in jump performance, muscle cross sectional area and overall strength (1RM deep squat, shallow squat and isometric knee extension strength). Pallarés et al. (13) compared the effects of full, parallel and half squat training for 10 weeks in a group of resistance trained males. Improvements in power output, countermovement jump height and 20 meter sprint time were greatest in the full depth squat group, followed by the parallel squat group, with trivial to no improvements observed in the half-depth squat group. Kubo et al. (16) compared the effects of full vs. half squat training for 10 weeks in a group of male subjects. No differences were observed for increases in quadriceps muscle volume between groups post training (i.e. both increased to a similar extent), with greater increases in adductor muscle volume observed following the full squat training compared to the half squat training.

The results from a study by  Rhea et al. (20) run somewhat against the grain though. In this project, subjects performed full ROM, half ROM or quarter ROM back squat training for 16 weeks. Whilst all groups improved various performance test results  (vertical jump height, 40 yard sprint time), improvements were greatest following quarter squat training. Whilst this suggests there may be some merit to quarter squat training for improving overall performance, the vast majority of the literature indicates that deeper squat training results in superior improvements in performance.

I’ve gone to great lengths to outline the literature in this area, but it needs  to be noted that most of the available studies have not been conducted in highly trained individuals. This means that if you are dealing with athletes who have been strength training for a number of years and are already pretty strong, the results you get from full vs. partial range of motion squat training may differ.

// Caveats To The Universal Application Of Full Range Of Motion Squat Testing

Up to now I’ve spent quite a bit of time advocating for the use of full ROM squatting, both in testing and training. I’m probably coming across as a shill for Big ROM. However, practically speaking, there are some very genuine reasons for certain athletes stopping short of  full depth squat in their training. In this context, it’s perfectly justified to use a modified ROM. However, for the purpose of performance monitoring over time, this modified ROM needs to be quantified so that repeat testing can be conducted under the same conditions. Previously, coaches have done this using either a pin squat or a squat to a box, depending on the preference of the coach and quantified either by measuring the athlete’s joint angles (e.g. hip, and knee angles) at the lowest point in the ROM, by recording the height of the squat box or by recording the the height of the pins in the squat rack. The innovation of technology has made this process efficient and seamless now with instantaneous feedback on ROM now being possible.

Introductory video on Output Sports AVBT pathway, to learn more about it, go to the suggested article below!

https://www.youtube.com/watch?v=b4RZWHYoLsE

// A Final Point To Consider

The purpose of this article isn’t to throw shade coaches who avoid full range of motion squatting in their training and testing. The aim is to create an awareness of the issues around 1RM squat depth standardization as well as the potential benefits of full range of motion squat training for improving overall athletic performance. However, there are genuine reasons for using modified squat depths with athletes and that ought to be acknowledged.

// References

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2. Suchomel TJ, Nimphius S, Stone MH. The importance of muscular strength in athletic performance. Sports medicine. 2016;46(10): 1419-1449. doi:10.1007/s40279-016-0486-0.

3. Baker D, Nance S. The relation between strength and power in professional rugby league players. The Journal of Strength & Conditioning Research. 1999;13(3):224-229. doi:10.1519/1533-4287.

4. Wisløff U, Castagna C, Helgerud J, Jones R, Hoff J. Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players. British journal of sports medicine. 2004;38(3):285-288. doi:10.1136/bjsm.2002.002071.

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6. Hartmann H, Wirth K, Klusemann M, Dalic J, Matuschek C, Schmidtbleicher D. Influence of squatting depth on jumping performance. The Journal of Strength & Conditioning Research. 2012;26(12):3243-3261. doi:10.1519/JSC.0b013e31824ede62.

7. Keiner M, Sander A, Wirth K, Schmidtbleicher D. Long-term strength training effects on change-of-direction sprint performance. The Journal of Strength & Conditioning Research. 2014;28(1):223-231. doi:10.1519/JSC.0b013e318295644b.

8. Seitz LB, Reyes A, Tran TT, de Villarreal ES, Haff GG. Increases in lower-body strength transfer positively to sprint performance: a systematic review with meta-analysis. Sports medicine. 2014;44(12):1693-1702. doi:10.1007/s40279-014-0227-1.

9. Styles WJ, Matthews MJ, Comfort P, Effects of strength training on squat and sprint performance in soccer players. The Journal of Strength & Conditioning Research. 2016;30(6):1534-1539. doi:10.1519/JSC.0000000000001243.

10. Wirth K, Hartmann H, Sander A, Mickel C, Szilvas E, Keiner M. The impact of back squat and leg-press exercises on maximal strength and speed-strength parameters. The Journal of Strength & Conditioning Research. 2016;30(5):1205-1212. doi:10.1519/JSC.0000000000001228.

11. Beattie K, Carson BP, Lyons M, Kenny IC. The effect of maximal-and explosive-strength training on performance indicators in cyclists. International journal of sports physiology and performance. 2017;12(4):470-480. doi:10.1123/ijspp.2016-0015.

12. Beattie K, Carson BP, Lyons M, Rossiter A, Kenny IC. The effect of strength training on performance indicators in distance runners. The Journal of Strength & Conditioning Research. 2017;31(1):9-23. doi: 10.1519/JSC.0000000000001464.

13. Pallarés JG, Cava AM, Courel-Ibáñez J, González-Badillo JJ, Morán-Navarro R. Full squat produces greater neuromuscular and functional adaptations and lower pain than partial squats after prolonged resistance training. European Journal of Sport Science. 2019;20(1):115-124. doi:10.1080/17461391.2019.1612952.

14. Williams JA. A comparison of hip and knee torques produced during a maximal effort full and partial back squat. 2015. Dissertations and Theses @ UNI. 189. https://scholarworks.uni.edu/etd/189

15 Bazyler CD, Sato K, Wassinger CA, Lamont HS, Stone MH. The efficacy of incorporating partial squats in maximal strength training. The Journal of Strength & Conditioning Research. 2014;28(11):3024-3032. doi: 10.1519/JSC.0000000000000465.

16. Kubo K, Ikebukuro T, Yata H. Effects of squat training with different depths on lower limb muscle volumes. European journal of applied physiology. 2019;119(9):1933-1942. doi:10.1007/s00421-019-04181-y.

17. Bloomquist K, Langberg H, Karlsen S, Madsgaard S, Boesen M, Raastad T. Effect of range of motion in heavy load squatting on muscle and tendon adaptations. European journal of applied physiology.  2013;113(8):2133-2142. doi: 10.1007/s00421-013-2642-7.

18. McMahon GE, Morse CI, Burden A, Winwood K, Onambélé GL. Impact of range of motion during ecologically valid resistance training protocols on muscle size, subcutaneous fat, and strength. The Journal of Strength & Conditioning Research. 2014;28(1):245-255. doi:10.1519/JSC.0b013e318297143a

19. Contreras B, Vigotsky AD, Schoenfeld BJ, Beardsley C, Cronin J. A comparison of gluteus maximus, biceps femoris, and vastus lateralis electromyography amplitude in the parallel, full, and front squat variations in resistance-trained females. Journal of applied biomechanics. 2016;32(1):16-22. doi:1 0.1123/jab.2015-0113.

20. Rhea MR, Kenn JG, Peterson MD, Massey D, Simão R, Marin PJ, Favero M, Cardozo D, Krein D. Joint-angle specific strength adaptations influence improvements in power in highly trained athletes. Human movement. 2016;17(1):43-49. doi:10.1515/humo-2016-0006.

21. Bryanton MA, Kennedy MD, Carey JP, and Chiu LZ. Effect of squat depth and barbell load on relative muscular effort in squatting. The Journal of Strength & Conditioning Research. 2012;26(10):2820-2828. doi:10.1519/JSC.0b013e31826791a7.

// About The Author

Dr. Arthur Lynch is a muscle physiologist based in the University of Limerick, Ireland. Dr. Lynch’s doctorate investigated the use of the isometrics squat as an assessment tool in an applied strength and conditioning context. Dr. Lynch is an international powerlifter and coaches with CityGym Limerick and the renowned Sigma Nutrition.