Brief Review
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The Use of Free Weight Squats in Sports: A
Narrative Review—Squatting Movements,
Adaptation, and Sports Performance: Physiological
Michael H. Stone,1 Guy Hornsby,2 Satoshi Mizuguchi,1 Kimitake Sato,3 Daniel Gahreman,1 Marco Duca,1
Kevin Carroll,1 Michael W. Ramsey,1 Margaret E. Stone,1 and G. Gregory Haff4
1
Center of Excellence for Sport Science and Coach Education, Department of Sport, Exercise, Recreation and Kinesiology, East
Tennessee State University, Johnson City, Tennessee; 2School of Sport Sciences, College of Applied Human Sciences, West Virginia
University, Morgantown, West Virginia; 3Peak Force International, Taichung, Taiwan; and 4School of Medical and Health Sciences,
Edith Cowan University. Joondalup, Western Australia
Abstract
Stone, MH, Hornsby, G, Mizuguchi, S, Sato, K, Gahreman, D, Duca, M, Carroll, K, Ramsey, MW, Stone, ME, and Haff, GG. The use
of free weight squats in sports: a narrative review—squatting movements, adaptation, and sports performance: physiological. J
Strength Cond Res 38(8): 1494–1508, 2024—The squat and its variants can provide numerous benefits including positively
affecting sports performance and injury prevention, injury severity reduction, and rehabilitation. The positive benefits of squat are
likely the result of training-induced neural alterations and mechanical and morphological adaptations in tendons, skeletal muscles,
and bones, resulting in increased tissue stiffness and cross-sectional area (CSA). Although direct evidence is lacking, structural
adaptations can also be expected to occur in ligaments. These adaptations are thought to beneficially increase force transmission
and mechanical resistance (e.g., resistance to mechanical strain) and reduce the likelihood and severity of injuries. Adaptations
such as these, also likely play an important role in rehabilitation, particularly for injuries that require restricted use or immobilization of
body parts and thus lead to a consequential reduction in the CSA and alterations in the mechanical properties of tendons, skeletal
muscles, and ligaments. Both volume and particularly intensity (e.g., levels of loading used) of training seem to be important for the
mechanical and morphological adaptations for at least skeletal muscles, tendons, and bones. Therefore, the training intensity and
volume used for the squat and its variations should progressively become greater while adhering to the concept of periodization and
recognized training principles.
Key Words: strength, specificity, resistance training, lower-body strength
Introduction
The importance of muscular strength should not be underestimated. Strength is the ability to produce force against an external resistance (181,183); its dynamic application provides
a mechanism for movement (F 5 ma). Because of its relationship to
movement, strength is an integral aspect underpinning sport performance capability. Furthermore, strength should be thought of as
a “vehicle” that carries with it numerous characteristics important
for sport performance (1,39,50,52,64,66,71,176,179). The basic
characteristics of maximum strength enhancement promotes several characteristics of importance to sport; these characteristics are
shown in Table 1.
Note, among weaker athletes, likely including most athletes (189),
evidence indicates that strength training alone produces equal or
superior results in enhancing rate of force development (RFD),
power, etc. compared with power or speed training alone
(1,39,41,102). This is especially evident when performed in an integrated fashion within a holistic sport training program (189,213).
Numerous authors indicate that the squat is one of the most
important exercises for increasing the strength of the athlete and
the overall development for a variety of sports, particularly the
Address correspondence to Michael H. Stone, Stonem@etsu.edu.
Journal of Strength and Conditioning Research 38(8)/1494–1508
ª 2024 National Strength and Conditioning Association
lower body (12,29,154,207). Among relatively untrained, welltrained and various athlete groups, improvements in squatting
ability and capacity have been shown to result in improvements in
lower-body strength, jumping ability (19,88), change of direction
ability (19,88), and sprinting performances (34), all of which can
be critical components of sporting success.
Numerous examinations of squat training have shown gains in
maximum strength both dynamically (1RM) and using isometric
test (19,46,82,190). In addition, it is widely reported that the use
of squatting movements enhances speed-strength characteristics,
associated concentric muscle actions (e.g., static vertical
jump) (19,82,84,85,167,210), and jumping motions using
a stretch shortening cycle (e.g., countermovement jump)
(6,9,10,19,38,39,82,84,89,182,185,191). The vertical jump has
also been related to sprinting performance. Because of the widely
reported interrelationships between strength and vertical jump
performance and the fact that vertical jump capacity relates to
sprinting performance, it is logical that strength characteristics
would be generally positively correlated to both sprinting and
jumping. Indeed, there are several studies that have noted a positive relationship between squat strength and sprinting performances (33,34,39,129,171). Based on this line of reasoning, for this
review, the intention of the authors is to highlight and to provide
an exploration of the potential benefits of using squats as a primary resistance training movement for athletes.
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Table 1
Basic characteristics associated with increased maximum
strength.
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Magnitude of force production—greater peak and average forces can be produced,
allowing for higher velocities and power outputs to be achieved with absolute
submaximal loads
Greater peak and average power output—work can be accomplished at a higher rate
Greater ability to develop and respond to stretch shortening cycles (SSC)
Increased absolute endurance, especially high-intensity exercise endurance (HIEE)
through an enhanced mechanical efficiency and exercise economy and altered
metabolism and a reduced central nervous system fatigue that can allow more total work
to be accomplished
Greater rate of force development (RFD)—faster muscle activation, greater force during
critical periods—important for acceleration
Greater and more efficient motor unit synchronization, which is important for ballistic
movements
Greater postural/positional strength that can underpin superior balance and enhance the
ability to hold static and dynamic positions and perform better during static and dynamic
performances
Some evidence suggests that force sensitivity and sensation can be superior (may be
a result of strength training partially independent of maximum strength)—modulate
force production ability may be superior
Literature was gathered from Google Scholar and PubMed.
With few exceptions, literature cited was confined primarily to
those studies using free weights. The literature cited was limited to the back squat, and front squat, and their derivatives
(e.g., partial, speed squats). Free weights and squat type (back
or front) were chosen as these are commonly used in the
training of athletes worldwide. Although, other forms of
squats, such as overhead and Zercher squats, are used in
training to a greater or lesser extent, there is limited research
available exploring their efficacy.
Key words and phrases (English) used in the search included,
“squats,” “front Squats,” “strength,” “strength-endurance,”
“power endurance,” and “high intensity exercise.”
Squat Training and Strength Development
Examining the scientific literature, it is apparent that squatting
movements used as a primary part of sport-specific strength
training programs result in substantial increases in overall lowerbody dynamic and isometric maximum strength in a variety of
populations (19,34,46,82,89).
Generally, training with full or parallel squats for 10–12 weeks
results in statistically significant increases of ;12–40% in the
1RM (19,89). As would be expected, over a similar short training
period, better trained subjects would realize smaller improvements in squat performance (200).
Based on the examination of the training response to ½ back
squats, there is typically a 17–40% increase in maximum strength
after only 7–10 weeks of training in relatively untrained individuals (39,89,214). This type of training can also increase the
relative squat (per kg body mass) strength. For example, Hartmann et al. (89) found short-term training (i.e., 10 weeks) in
previously untrained male athletes with a relative squat strength
of 1.05 3 body mass (initial value) increased the parallel to approximately 1.3 3 body mass. In athletic populations, 7–8 weeks
of full and ½ back squat training have resulted in a 12–25% increase in maximal squat strength (34,155,167,168).
Although peak strength gains are commonly measured using
1RM values, gains can also be measured using “nonspecific”
measurements, such as isometric testing (110,192). However, the
gains in maximum strength are generally smaller when strength is
quantified using these types of nonspecific measurements (195).
For example, 12 weeks of full squats (dynamic multi-joint closed
kinetic chain) resulted in small but statistically significant increased knee extension MVC (single joint) at 75° (6 6 2%, p ,
0.05) and 105° (8 6 1%, p , 0.05), whereas parallel squats
resulted in a nonstatistically significant increase in knee extension
MVC at 40° (6 6 3%, p . 0.05) and 75° (2 6 2%, p . 0.05) (19).
As an alternative to single-joint isometric testing, isometric (multijoint isometric) measures that allow somewhat greater positional
or mechanical specificity can also be used to track strength
alterations (27,82,155,214).
When considering isometric force-time curve assessments, it is
clear that there can be an angle-specific adaptation resulting from
the characteristics of the training exercise (19,65,89,113,214).
However, based on the current body of scientific evidence,
squatting through a full range of motion results in an increased
MVC at a variety of joint angles (19,81,83,89).
It becomes apparent that regardless of whether dynamic
(i.e., 1RM) or isometric (i.e., MVC) assessments are made, squats
are effective training exercises for increasing lower-body strength.
However, it is difficult to make clear comparisons between the
various training studies presented in the literature because there
are differences in the training methods, duration of training, and
Table 2
Relationship between absolute back squat strength and jumping performance.*
Back squat
Author
Blackburn and Morrissey (18)
Carlock et al. (26)
Helgerud et al. (91)
Kirkpatrick et al. (112)
Nuzzo et al. (152)
Peterson (156)
Requena et al. (163)
Requena et al. (164)
Wisløff et al. (207)
Subjects/athletes
Physiotherapy students
Weightlifters
Soccer players
Rugby league forwards
Rugby league backs
Male athletes
Collegiate athletes
Sprinters
Soccer players
Soccer players
Type
Half
Full
Half
Half
Parallel
Half
Half
Half
Half
Correlation (r)
1RM (kg)
Countermovement vertical jump height
74.8 6 28.7
163.6 6 51.2
176 6 16.2
140.2 6 26.2
132.7 6 9.4
170.8 6 22.6
110.4 6 38.8
171.7 6 21.2
119.5 6 26.2
171.7 6 21.2
0.72†
0.52†
0.38
0.57‡
nr
Static vertical jump height
0.22
0.86†
0.18
0.50†
0.78†
nr
nr
nr
0.58†
nr
nr
0.50†
nr
*nr 5 not reported.
†p , 0.05.
‡p , 0.01.
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Table 3
Relationship between relative back squat strength and jumping performance.*
Back squat
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Author
Subjects/athletes
Carlock et al. (26)
Kirkpatrick et al. (112)
Weightlifters
Rugby league forwards
Rugby league backs
Soccer players
Male athletes
Collegiate athletes
Sprinters
College students
Helgrud et al. (91)
Nuzzo et al. (152)
Peterson (56)
Requena et al. (64)
Young and Bilby (214)
Full
Half
Half
Parallel
Half
Half
Half squat (machine)
Correlation (r)
1RM (kg.kg21)
Type
Countermovement vertical jump height
nr
1.56 6 0.20
1.61 6 0.13
1.48 6 0.26
1.93 6 0.21
1.47 6 0.37
1.92 6 0.17
2.79 6 0.30
Static vertical jump height
0.69†
0.42†
nr
0.72†
0.23
0.69†
0.85†
0.32
0.47†
nr
nr
nr
nr
nr
*nr 5 not reported.
†p , 0.05.
.
methods used to assess strength gains. Therefore, further research
that clearly outlines the variables used to create a well-structured
training program is warranted.
Squat and Jumping Performance. Several authors have suggested
that sporting success is largely predicated by the development of
strength and power, which both play a large role in vertical jump
performance (122,138,162,178,183). Of note, is the observation
that the ability to jump is considered one of the fundamental skills
for success in numerous sports (22,25,54,69,70,89,100,122,156).
Based on previous research, the vertical jump is a reliable predictor
of sporting success in American football (140), soccer
(72,144,207), ice hockey (15), sprint cycling (184), and numerous
other sports (50). Successful vertical jump performance is therefore
predicated by the ability to generate maximal forces and
express those forces rapidly to maximize jumping height
(1,10,80,122,137). Because strength underpins vertical jumping
ability, it is widely believed that increases in maximum leg strength
are related to improvements in vertical jumping performance
(6,10,18,19,38,39,82,84,85,167,182,185,190,191).
Although not all research show strong correlations
(91,152,163), strong relationships between leg strength and vertical jump performance have been reported between the absolute
1RM in the half and full back squat and countermovement vertical jump height in untrained students (18), weightlifters (26),
soccer players (164,207), rugby league athletes (112), and various
collegiate athletes (156) (Table 2). In addition, support for this
relationship can be noted as a result of the strong relationships
that have been reported between the absolute 1RM and the static
vertical jumps of weightlifters (26), soccer players (91), sprinters,
and various male athletes (152). Based on the current body of
research, it seems that approximately 25–75% of the variance in
the countermovement vertical jump performance can be
explained by the athlete’s absolute back squat strength (181).
Although absolute strength seems to be an important contributor
to an athlete’s ability to jump, it may be more important to consider
the athlete’s relative strength levels. Bobbert (20) have reported that
the size of the jumper and the amount of force that is generated
relative to the size of the jumper can dictate acceleration before
takeoff and the overall vertical displacement achieved. Therefore,
Table 4
Relationship between absolute back squat strength and sprinting performance.*
Correlation coefficient (r)
Absolute strength and sprint time
Back squat
Author
Subjects/athletes
Type
Baker and Nance (8)
Rugby league
Full
Brechue et al. (21)
Chaouachi et al. (30)
Comfort et al. (35)
Cronin and Hansen
(42)
Cunningham et al.
(43)
Helgerud et al. (91)
Kirkpatrick et al. (112)
Football
Basketball
Soccer players
Rugby league
Parallel 170.5 6 28.2
Half
Half
142.3 6 25.3
Parallel
Rugby union
Deep
186.2 6 22.6
Soccer players
Rugby league
forwards
Rugby league backs
Sprinters
Soccer players
Soccer players
Half
Half
176 6 16.2
140.2 6 26.2
132.7 6 9.4
Half
Half
Half
149.0 6 12.0
119.5 6 26.2
171.7 6 21.2
Requena et al. (163)
Requena et al. (164)
Wisløff et al. (207)
1RM (kg)
3RM (kg)
4.5
m
5m
157.9 6
18.8
9.1
m
10 m
15 m
20 m
30 m
36.6
m
20.06
40 m
20.19
0.11
143 6 13.4
nr
20.63†
20.60‡
20.05
20.68†
20.65‡
20.01
20.65
20.29
0.17
20.25†
20.51†
20.28†
20.38
20.94†
20.57‡
20.47†
20.26
20.20†
20.54†
20.49†
20.71†
*nr 5 not reported.
†p , 0.05.
‡p , 0.01.
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Table 5
Relationship between relative back squat strength and sprinting performance.*
Correlations (r)
Relative back squat
Author
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Baker and Nance
(8)
Brechue et al. (21)
Comfort et al.
(33,34)
Comfort et al. (35)
Cunningham et al.
(43)
Helgrud et al. (91)
Kirkpatrick et al.
(112)
Subjects/
athletes
Type
1RM (kg.kg21)
Rugby league
Full
Football
Rugby league
Recreational
Soccer players
Rugby union
Parallel 1.69 6 0.33
Half
1.78 6 0.27
1.77 6 0.33
Half
1.97 6 0.34
Deep
Soccer players
Rugby league
forwards
Rugby league
backs
Football players
Half
Half
McBride et al.
(136)
Meckel et al. (142) Sprinters
Requena et al.
Sprinters
(164)
3RM
(kg.kg21)
4.5 m
5m
9.1 m
10 m
20 m
30 m
36.6 m
20.39
nr
20.34
20.62‡
20.52‡
20.55†
nr
1.48 6 0.26
1.56 6 0.20
1.61 6 0.13
Parallel 1.94 6 0.33
Half
Half
Relative strength and sprint time
20.45†
1.92 6 0.20
1.92 6 0.17
100 m
20.53†
20.67‡
20.30 20.32
20.46‡
20.45‡
40 m
20.66†
20.55†
20.44‡
20.60†
20.53‡ 20.59† 20.56‡
20.50‡
20.89‡
*nr 5 not reported.
†p , 0.05.
‡p , 0.01.
relative strength levels may be more important when examining the
relationship between squat and jumping performances (Table 3).
Considering the relative ½ and parallel back squat 1RM,
a moderate-to-large relationship has been reported with countermovement vertical jumps (112,152,212). Strong correlations
have been found between the relative ½ squat maximum strength
and countermovement vertical jump in collegiate athletes (156).
In addition, the relative full back squat 1RM has been reported to
be strongly associated with countermovement vertical and static
vertical jump height (26).
In summary, it seems that lower-body strength, as indicated by
the absolute and particularly the relative 1RM back squat, is
substantially related to vertical jump performance. Therefore, it
seems that the use of loaded squatting movements in the preparation of athletes who need to maximize vertical jump performance is warranted.
Squat Training and Jumping Performance. In the scientific literature, there are numerous studies ranging from 5 to 24 weeks in
duration, which demonstrate that increases in deep or parallel
back squat strength (1RM) translate into improvements in
countermovement jump and static jump performance
(9,19,39,41,85,87,88,94,102,105,109,143,192,197,201,209).
Although, the percent gain and magnitude of effect were moderate (as calculated by the authors of this article), studies using
short-duration training (,5 weeks), basketball players (93), and
American football players (94) have not shown statistically significant improvements in jumping performance. Such short
studies may be of insufficient duration, thus not allowing time for
the strength gains achieved in the back squat to be translated into
countermovement jumping performances (91).
Although not all (74,93,121,130,168,199), most studies indicate
that 7.5–10 weeks of training targeting strength gains, with the use of
½ squats, produced substantial static (6,19,31,37,40,89,194,195)
and countermovement (19,40,89,194,195,206,214) vertical jump
performance gains among relatively untrained subjects with a low
initial performance capability. Interestingly, the parallel squat has
demonstrated the greatest gains in strength and the greatest transfer
of training effects to jumping movements based on the method of
Zatsiorsky (216) and Zatsiorsky et al. (218). This method (coefficient of transfer) estimates the degree of trained exercise transfer
to a nontrained performance measure using the following equations:
Result gain ¼
Gain of performance
Standard deviation of performance
Coefficient of transfer ¼
Result gain in nontrained performance
:
Result gain in trained performance
The higher the calculated training scores, the greater the
transfer of training effect. Based on these calculations, the parallel
back squat produces the greatest positive transfer of training
effects to jumping movements (199).
Collectively, it seems that based on the majority of the findings
in the scientific literature increases in 1RM squat strength, especially relative squat strength (absolute per kg body mass), can lead
to increases in vertical jump performance. One aspect that is of
particular importance in assessing the improvement of squat
strength and its influence on vertical jump performance deals with
force impulse. Often among study participants or athletes gaining
weight, the vertical jump does not show concomitant alterations
over time (187). However, the impulse does increase (i.e., greater
body mass same jump height). It is of note that in many of the
studies indicating that squat training did not alter jump height,
body mass did increase, indicating an increased impulse and thus
a positive training effect (187).
In addition, the depth of the squat may play an integral role in
mitigating the transfer of training effects from the squat to
jumping tasks. Even though there is compelling evidence that
improvements in squat strength correspond to improvements in
vertical jump performance, more research is needed to fully
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Squats in Sport: Terminology and Biomechanics (2024) 38:8
understand the improvements and how these alterations are
stimulated by increasing squatting strength.
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Squat and Sprint Performance. Running speed and more importantly the ability to accelerate during sprinting based activities are
critical components for success in performance-based improvements (132). This ability is a critical attribute that encompasses
performance in numerous individual and team sports
(25,30,55,58,69). For example, when examining Rugby Union
players (69), the ability to accelerate is considered one of the
critical attributes because the average sprint duration during
a match is only approximately 3 seconds in duration
(47,48,55,56). Taken collectively, it is very apparent that the
ability to accelerate and sprint at high velocities should be a key
target for most strength and conditioning professionals.
Careful inspection of acceleration and sprinting characteristics
reveals a clearly defined relationship between the ability to exert
a given ground reaction force (GRF) and subsequent running
velocity (202,203,208). Strong correlations have been reported
between GRF magnitude, impulse, and the ability to accelerate
and achieve higher velocities during sprinting actions (99,199).
During the acceleration phase of sprinting, it is evident that athletes must accelerate their center of mass (CoM), through an explosive concentric force production, generated by both the knee
and the hip extensor muscles (46,59,61,132,205). Thus, expression of high concentric forces and power is required to generate
high velocities during this time frame (143). On achieving maximal running speed, forward propulsion is accomplished by the
actions of the hip and ankle extensors (143,205). During this
phase of sprinting, each foot strike can occur in less than 0.1
seconds and can result in vertical GRF in excess of 5 times body
weight (143). These findings highlight the critical importance of
developing the athlete’s overall lower-body strength and ability to
express high power outputs. Therefore, it is universally accepted
that to develop acceleration and sprinting speed, athletes should
use lower-body strength training methods, including squats, to
enhance these capacities (8,45,46).
When examining the relationship between lower-body
strength and sprinting ability, studies that have used single-joint
exercises such as the leg extension performed in either an isometric or an isokinetic condition have found no (164), small
(17,53,212), or moderate (149) relationships between strength
and sprinting performance. Conversely, when multi-joint exercises, such as the squat, have been examined, stronger relationships have been found between maximum strength and sprinting
performance (175). Indeed, when ½, parallel, or deep back squat
have been correlated with various sprint performance distances,
moderate-to-nearly-perfect correlations have been found
(8,30,42,43,91,112,163,207) (Table 4).
Calculation of the relationship between absolute back squat
strength and sprinting performances between 5 and 40 m resulted in
minor-to-nearly-perfect correlations (30,36,91,112,136,163,207).
For example, Comfort et al. (35) indicated that among youth soccer
players, the absolute 1RM ½ back squat is strongly correlated with
5 m (r 5 20.60, p , 0.01) and 20 m (r 5 20.65, p , 0.01) sprint
times. Although there are several studies that demonstrated large-tonearly-perfect correlations between the absolute ½ back squat and
sprint times, there are several studies that report trivial-to-small
correlations (17,42,43,112). For example, among Rugby League
athletes, Cronin and Hansen (42) and Kirkpatrick and Comfort
(112) reported trivial-to-small correlations between sprint times at 5,
10, 30, and 40 m and the absolute 1RM in the parallel and ½ back
squat. Interestingly, it seems that these data indicate that weaker
correlations exist between absolute back squat performance and
sprint times at various distances in sports such as rugby and football,
where the athletes tend to have a large overall body mass. Conceptually, this would make sense as Weyland and Davis (201) indicated
that intermediate levels of massiveness are conducive for optimizing
human speed. Thus, it may be more appropriate to examine the
relationships between relative back squat strength and sprinting
performance to better understand the impact that squatting exercises
and training have on performance (21).
The most common method for determining relative strength is
to simply divide the weight lifted by the body mass of the athlete
(101). When squats are expressed relative to body mass,
moderate-to-very-large relationships to sprinting performance
have been noted (8,21,33,35,43,112,136,142,163) (Table 5).
This increased relationship has been illustrated by Baker and
Nance (8), who reported large correlations between the relative
3RM full back squat and 40-m sprint time (r 5 20.66, p , 0.01) in
Rugby League athletes. When the absolute 3RM values are used to
examine this relationship with the same athletes, the correlation is
substantially reduced (r 5 20.19, p . 0.05). Similarly, among
American football players, the relationship between the 1RM relative parallel back squat and the 36.6-m sprint resulted in a strong
relationship (21,136). In addition, among sprint athletes, the half
back squat is correlated with the 10 m (r 5 20.53, p , 0.01), 30 m
(r 5 20.56, p , 0.01), 40 m (r 5 20.50, p , 0.01), and 100 m
(r 5 20.89, p , 0.1) (21,133). In addition, Keiner et al. (108)
reported that relative parallel back squat of youth soccer players
explains 36% of the variance (r 5 20.60) in their 30-m sprint performance. Collectively, when relative back squat maximum strength
is examined, between 19 and 79% of the variance in sprinting performance between distances of 5–100 m can be explained.
Although dividing the back squat RM values by the athlete’s
body mass is a common practice, it is well documented that
strength does not increase in direct proportion to body mass gains
in trained individuals (91,101). Jaric (101) suggested that the athletes’ body size may affect the strength testing results and that the
principle of “geometric similarity” should be considered. Based on
this principle, muscle force-generating capacity should be proportional to either body height squared (H2) or body mass raised to
the two-thirds power (m2/3). In addition, Jaric (101) recommended
that to truly understand relative strength, the load lifted should be
allometrically scaled by dividing the load lifted by body length
squared (H2) or a body-volume-related index raised to the twothirds power (m2/3). Ultimately, there are very few studies in the
scientific literature that have been investigations of the association
of allometrically scaled squat performance and sprinting performance. Helgerud et al. (91) examined ½ squat 1RM scaled relative
to body mass and scaled allometrically and their relationship to
sprinting performance. When the 20-m sprint time was correlated
with relative ½ back squat 1RM (kg.kg21), there was a nonsignificant moderate correlation (r 5 20.33, p 5 0.14). However,
an allometrically scaled ½ back squat 1RM (kg.kg20.67) correlated
to sprint time was substantially larger (r 5 20.41, p 5 0.07),
agreeing with the findings of Swinton et al. (190).
These data suggest that allometrically scaled metrics may reveal
stronger relationships than previously noted between back squat
strength and sprinting performance. Therefore, future research
should investigate allometrically scaling the squat 1RM by dividing
its value by the mass of the subject raised to the two-thirds power.
In summary, it seems that both absolute and relative strength
levels as expressed during various types of back squats are related
to
acceleration
and
sprinting
performance
(8,30,33,43,91,112,136,156,163,207). Thus, scaled results likely
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produce stronger relationships, but more research is needed to
confirm this contention. However, the common belief that
squatting abilities are an important contributor to sprinting speed
and acceleration seems to be justified by the scientific literature.
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Squat Training and Sprint Performance. Examination of the relationship between squat training and sprint performance gains
demonstrated that increases in absolute or relative half or deep
back squat maximum strength results in improvements in
sprinting performance (34,39,92,104,108,109,121,133,170).
Relatively untrained or weaker subjects seem to experience
improvements in sprinting performance as a result of increasing
absolute and relative squat strength (39). For example, in relatively weak individuals, Cormie et al. (39) reported that after
10 weeks of back squat training, there was a statistically significant increase in relative ½ back squat performance (31.2 6 2.3%)
that corresponded to a statistically significant improvement in
40 m (2.2 6 1.9%) sprint time. However, as might be expected,
Kiener et al. (109) indicated that as squat strength improves, it
explains less of the variance in sprinting performance.
Considering athlete groups, including juniors, evidence indicates that increasing absolute and relative lower-body maximum
strength (1/2 and full squats) has substantial impact on running
speeds, particularly over the initial first 5–10 m of a sprint
(34,91,108,109,168,175). The greater improvements in the first
5–10 m were expected because the greatest forces are required
during this time frame, and it contains the initial acceleration
phase of sprinting.
Not all training studies have reported improvements in
sprinting performance that corresponded to increases in squatting
performance (171). However, combined training programs, using
combinations of the full squat, ½ squat, ¼ squat (Figure 1A–C),
jump squat, and plyometrics, have resulted in a small improvement in sprinting performance (79,183,186). This finding is in
line with a number of authors who recommend that a mixed
method of training that targets maximal strength (i.e., back squat)
and power development (e.g., plyometrics, weightlifting, jump
squats) in a logical order may be needed when attempting to
maximize athletic development (79,102,179,183,186).
Collectively, the contemporary body of scientific evidence
indicates that increased back squat strength, particularly relative
back squat strength can result in improvements in sprinting performance. Although this contention seems to be based on sound
science, again, more research is warranted to truly understand the
role squatting has in the development of sprinting performance.
Squatting Depth and Performance. One common question in the
applied literature is what squat depth offers the best transfer of
training to actual sports performance. Zatsiorsky (216) suggested
that various depths of squats should be performed depending on
the phase of the annual training plan. For example, during offseason periods, he recommended a 70–30% split between deep
and partial squatting movements. More recently, Zatsiorsky and
Kraemer (217) suggested that if the sporting movement requires
high force to be applied in a short movement segment, there is no
reason to perform full squats. Thus, it promotes a form of anglespecificity–based transfer of training effect. Conversely, Hartmann et al. (89) questioned this line of thought and offered
compelling evidence that this may not be an accurate or appropriate recommendation. To achieve a maximal vertical jump
height, the applied impulse can be modified through the acceleration sequence. Specifically, one could modify the eccentric phase
by increasing descent velocity, minimize transition time,
maximize RFD, and optimize the impulse with targeted training
methods to optimize jumping height (37,40,89). Ultimately, the
training goal when targeting jumping improvements is to increase
the size of the overall impulse, which is applied during a specified
time frame (89). Hartmann et al. (89) suggested that the recommendation to limit the range of motion (ROM) to better match
the competition movement presented by Zatsiorsky et al. (216)
does not allow for the optimization of the overall impulse during
jumping movements. In support of this contention based on recent research into the squats depth, full squatting movements
produce superior improvements in vertical jump performance
when compared with parallel (19) or partial squats (89). in addition, Hartmann et al. (89) suggest that the full or parallel squat
exercise allows for an elevated force development that is available
across a full range of knee joint angles. Overall, the full squat
allows for the development of lower-body strength capacities
throughout a full ROM serving as the foundation from which
sport-specific technique training, such as those observed in
competitive movements such as sprinting and jumping, can be
developed. Specifically, the deep joint positions achieved in the
full squat supply the required neural and morphological stimuli
necessary to develop the knee and hip extensors ability to positively influence acceleration. To maximize the transfer of training
effects to reactive speed-strength sports, a mixed-methods approach in which heavily loaded and ballistic strength exercises,
that can include partial squat movements, is required
(7,79,89,183). Based on this line of thought, Hartmann et al. (89)
suggested that the full back squat should rarely be removed from
a periodized training program even during competitive periods
because it is essential for maintaining lower-body strength. Indeed, full squats (including full front squats) can develop and
maintain muscle volume better than partial squats (124). By
maintaining strength over a full ROM (i.e., full squats), the athlete
is then better able to safely handle the high relative and absolute
loads associated with speed strength methods such as plyometrics
and speed training.
From a specificity standpoint, examination of strength gains
indicates training with the full squat resulted in statistically
greater gains in full back squat strength, whereas training with the
¼ back squats resulted in superior gains in the ¼ back squat 1RM
(19) (Figure 2). Importantly, scientific literature provides substantial evidence indicating that the depth of the squat exhibits
a training specificity effect and seems to affect the overall performance capacity (19,89). Collectively, data suggest that full
back squats produce a superior transfer of training effect to
jumping movements. For example, Bloomquist et al. (19) reported that 12 weeks of full back squat training resulted in a statistically greater increase in the countermovement vertical jump
performance (113 6 2%) compared with a ¼ back squat (17 6
4%). Similar alterations were noted in the static jump (19).
Hartmann et al. (89) examined the effects of training with
various depths of squats on jumping performance. After 10 weeks
of training, the full back squat group displayed a statistically
greater increase in countermovement and static jumps (CMJ 5
17.79 6 5.43%; SJ 5 15.83 6 6.06%) compared with the ¼
back squat group (CMJ 5 20.01 6 6.77%; SJ 5 12.68 6
7.75%). Interestingly, when the ¼ back squat was compared with
the deep front squat, it was noted that the full front squat also
resulted in a statistically greater increase in countermovement
jump (18.29 6 6.15%) and static jump (17.19 6 7.33%) when
compared with the ¼ back squat. In addition, there seemed to be
a conformity of motion quality existing between full front and full
back squats (Figure 3). Specifically, the full front squat 1RM
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Figure 1. A) Full squat, (B) ½ squat, and (C) ¼ squat.
statistically increased (percentage) after training only with the full
back squat, which was similar to the gain achieved by training
only with the full front squat. Conversely, training with the ¼
back squat resulted in essentially no alteration in 1RM front squat
strength (Figure 3). Considering the percent change in the full
back squat 1RM, training with either the full front or the full back
squat resulted in a statistical increase. Training with only the ¼
back squat resulted in a statistically significant percent reduction
in the full back squat 1RM (Figure 3). Finally, the greatest percent
gains in ¼ back squat strength came from training with the ¼
back squat. Training with both the full front and the full back
squat resulted in increases in the ¼ back squat 1RM but the
greater percent change occurred in response to the full back squat
(Figure 3). Ultimately, based on the current data, training with full
front and back squatting movements have the ability to transfer
strength gains between one another (77,89). Collectively, the data
suggest that full squatting movements have the potential to better
“translate” strength gains, allowing for the development of
strength capacities necessary to induce large increases in vertical
jump performance.
Currently, there is an increased interest in researching the
effects of squatting depth and its effects on strength gains,
jumping performance, and the translation of strength gains to
athletic performance. Indeed, although research indicates that the
full squat is a foundational exercise, some relatively recent research indicates that partial ROM squats in conjunction with full
squats may be an effective training method for improving maximal strength as measured by a full squat 1RM and an isometric
squat peak force (13). In addition, enhancement of early isometric
force-time curve characteristics was noted in male athelets with
previous strength training experience (13). Bazyler et al. (13) also
noted that partial squats may be beneficial for strength-power
Figure 2. 1RM changes in the ¼ squat and full back squat after 12 weeks (19).
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Figure 3. Comparison of 1 RM for the front squat, back squat, and ¼ squat: transfer effects (89).
athletes during a strength-speed block or while peaking for
competition (13). It should also be noted that the addition of
ballistic movements, such as jumps in combination with squats,
may provide additional benefits for explosiveness and power
development (27,196). Ultimately, when attempting to increase
the strength capacity of the lower body, it is important to note that
more research should be conducted to verify all these findings.
Aspects that are not well studied include the differential training
level effects, sequential ordering of exercises both acutely and
over a training period, combination training (mixed partial and
full squats), the use of speed squats, and the effect of partial
movements among athletes that may already be well-trained in
the full squat.
Squats and Muscle Hypertrophy
Alterations in CSA and architecture of muscle, along with the
nervous system alteration, offers primary mechanisms for the
enhancement of force production and therefore performance
(11,96,173). Briefly, based on the available literature, the squat
can be an effective exercise for inducing hypertrophy of the gluteus maximus and the entire quadriceps, primarily the vastus
muscles with lesser effects noted for the rectus femoris
(124,150,165). Substantial evidence indicates that relative activation and subsequent hypertrophy from the back squat is quite
low for the hamstrings (134,165). Evidence suggests deeper
squats, particularly full back squats, may be more hypertrophic
for the gluteus maximus, although squat depth deeper 90° of knee
flexion may not provide additional hypertrophy of the knee
extensors (134,165). Inhomogeneous hypertrophy can occur
both within and between muscles as a result of resistance training
(215). Indeed, although limited, studies of the squat have also
demonstrated
intramuscle
inhomogeneous
hypertrophy
(57,165). It is apparent that squat variations (57) and weightlifting training including squats and pulling movements (106) and
speed of movement alterations (78) can induce different degrees
of inhomogeneous hypertrophy.
Importantly, inhomogeneous alterations in muscle and connective tissue, CSA, and architecture, as a result of squat training,
could alter the quadriceps moment of inertia and the moment
arms of muscle ‘‘compartments,’’ associated limb moments, and
influence force transmission and the muscular force expression
(57,102). Considering the performance results of selective hypertrophy, these alterations could be biomechanically beneficial
to high-force or high-power movements used in training and
performance. However, it is also theoretically possible that the
selection of inappropriate exercises for a particular sports group
could negatively affect performance. For example, compared with
back squats, some evidence indicates that front squats better activate the gluteus and quadriceps muscle, particularly the vastus
medialis (2013) and may provide a greater overall intramuscle
hypertrophy adaptation. Interestingly, faster sprinters (running)
display considerable proximal quadriceps hypertrophy and
smaller overall pennation angles compared with lesser sprinters
(128). So, introducing a squatting exercise(s) (i.e., front squats)
that would create considerable distal quadriceps hypertrophy or
markedly alter pennation angle could result in decreased sprint
performance.
Implications for Prehabilitation and Rehabilitation
Injuries commonly affect at least one of the following tissues:
skeletal muscle, tendon, ligament, cartilage, and bone. The
probability and severity of tissue injury depends, in part, on their
functions, mechanical, and structural characteristics (204). For
example, many noncontact injuries can be regarded as a tear of
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different levels in a tissue (e.g., microtear to complete tear in
Achilles tendon). Theoretically, the severity of a tissue tear can be
reduced by increased stiffness and stress capacity (material
strength). Besides stiffness and mechanical tension, other mechanical properties are often considered important for injury
prevention and severity reduction. These are different types of
force (e.g., compression, shear force, and torsion), anisotropic
property, deformation, mechanical stress and strain, modulus of
elasticity, and viscoelasticity (204). Furthermore, tissue content
(e.g., collagen, elastin), density, and CSA associate with mechanical properties. Literature suggests that physical activities can
alter tissue function, mechanical, and structural characteristics
(204). A properly designed resistance training programs provides
mechanical overloading, resulting in these adaptations
(2,66,103,153,180), likely reducing the probability and the severity of injuries.
Skeletal Muscle and Intramuscular Extracellular Matrix. Longterm resistance training increases the CSA of a skeletal muscle
(2,66). This is an important characteristic of resistance training
for both performance and rehabilitation, particularly when
skeletal muscle atrophy is apparent after an injury requiring immobilization or reduced use. Furthermore, the intramuscular
extracellular matrix (IEM), which includes the endomysium,
perimysium, and epimysium (160), responds to mechanical
loading and increases collagen synthesis similarly to increased
protein synthesis in skeletal muscle (115,135). Although more
research is needed, increased collagen synthesis can be regarded as
important evidence that the IEM adapts to mechanical loading
(105,135,174). This adaptation should increase its resistance to
mechanical loading, reducing skeletal muscle injuries such as
muscle strains. Moreover, when a muscle strain occurs, it is
usually in or near a myotendinous junction (193). Although, research is scarce, the effects of resistance training, running
(44,117), and ladder-based resistance training (158) have been
reported to cause the morphology of the myotendinous junction
to change in animals, which can be related to an increased support
and stabilization of force transmission (157). Furthermore,
structural alterations at the myotendinous junction should increase mechanical resistance (e.g., resistance to strain) and decrease injury potential.
Regarding reduced skeletal muscle injury risk and rehabilitation, the squats and variations allow exercise with moderate to heavy loads safely (refer to the section on safety). Range
of motion has been suggested to be one of the key stimuli for
skeletal muscle hypertrophy (68,95). Although all muscles may
not hypertrophy to the same extent (165), movements performed
with a greater versus lesser ROM seem to be more efficient and
effective when performed for the same sets, repetitions, and percentage of 1RM (19).
Clear relationships between intensity, the magnitude of mechanical stress, and collagen synthesis have yet to be established.
If mechanical loading from exercise increases collagen synthesis,
consequently altering morphology and mechanical properties of
the IEM and myotendinous junctions, it seems reasonable to
speculate that higher intensity with sufficient volume-load can
induce a greater magnitude of changes. Furthermore, Andersen
et al. (3) reported that conventional rehabilitation exercises are
limited in their abilities to provide higher intensity compared with
typical resistance training exercises such as the squat. This finding
suggests that as the process of rehabilitation progresses, it is important to incorporate typical resistance training exercises such as
the squat to provide sufficient overload.
Tendon and Ligament. Compared with skeletal muscle adaptations, there is less research examining tendon and ligament
adaptations to resistance training. Research on tendon and ligament alteration can be important, particularly to understand the
effectiveness of resistance training on prevention and rehabilitation of injuries such as anterior cruciate ligament tear.
Tendons. Human tendons are metabolically active tissues (114)
readily adapting to physical activities (24,90,115). A bout of
physical activity can result in elevated levels of autocrine and
paracrine factors such as transforming growth factor beta 1 and
insulin-like growth factor 1 and an increase in collagen synthesis
(90). It seems that human tendons do hypertrophy (90); however,
the hypertrophy seems to be largely confined to the proximal and
distal ends of tendons (120,177). The exact training induced architectural alterations likely depend on the specific training
method (62,123,141).
Increases in content and changes in mechanical properties of
human tendons in response to training have been reported
(28,62). Increases in tendon stiffness and estimates of tendon
content (e.g., the amount of collagen) occurred as early as
2 months postisometric training (123,125). However, it seems
that the level of mechanical loading must exceed a certain
threshold for a tendon CSA to increase (4,5,120) and that the
degree of tissue remodeling and increased tendon CSA seems to
depend on the magnitude of mechanical strain (198,219). Thus,
resistance training seems to be an effective method to induce tissue
adaptations in tendons (157,158). Although direct evidence
seems to be lacking, increased tendon CSA and content and
changes in tendon mechanical properties are speculated to reduce
tendon injury risk, such as Achilles tendon rupture. In addition,
resistance training performed in particular manners (e.g., eccentric or heavy-slow resistance training) has been reported to be an
effective treatment method for chronic tendinopathy
(107,119,131,166), particularly in male athletes (116). Although
not optimum for strength gains, one heavy slow resistance
training session has also been reported to be effective in tendinopathy rehabilitation (146) and may be more effective than
a corticosteroid injection in reducing pain over a 12-week period (119).
Scant research exists on squatting adaptations, such as the
patellar tendon. Early study reported that there were no changes
in patellar tendon CSA after 12 weeks of training using parallel
squat or 120° internal knee angle partial squats (19). However,
a variation of the squat, eccentric declined squats, have been
reported to be effective in reducing pain in chronic patellar tendinopathy, indicating that the patellar tendon undergoes a level of
mechanical stress sufficient to elicit physiological changes
(119,211). Importantly, evidence also indicates that tendon hypertrophy in concert with muscle CSA alterations (177).
The exact mechanisms of how eccentric declined squat can aid
in healing chronic patellar tendinopathy are not clear. However,
the loaded eccentric component seems to be a key factor in
treating chronic tendinopathy (147). Furthermore, although declining (squat depth: to an 85° knee angle, with 180° being the full
extension and to parallel) seems to increase mechanical loading
on the patella tendon (67,118), this does not mean that the squat
and variations do not have any degree of mechanical loading on
the patellar tendon. In fact, Frohm et al. (67) reported tension
greater than 6,000 N in the patellar tendon during a Bromsman
parallel squat (a bilateral eccentric overloaded squat performed
with a loaded barbell, to which steel wire cables were attached to
move the barbell up and down at a preset velocity) on a flat
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surface. A Bromsman squat may not produce exactly the same
stimulus as the typically performed squat. However, a similar
level of tension in the patellar tendon is expected during the squat.
In addition, it is rather unreasonable to speculate that the morphology, mechanical properties, and/or content of the patellar
tendon do not adapt to the squat when the knee extension exercise
and isometric sled squat at a 90° knee angle showed increases in
the patella tendon CSA and changes in mechanical properties
such as stiffness (120,126).
Besides the patella tendon, the Achilles tendon is speculated to
undergo large mechanical loading during the squat as the plantar
flexors are reported to be highly activated at knee angles ranging
from 105° to 119° (180° 5 full extension) compared with smaller
knee angles (23). More research on these parameters is
encouraged.
Ligaments. Although there seems to be a paucity of research on
adaptations of ligaments to any type of training in humans, including resistance training, evidence indicates that weightlifters,
training at least for 10 years, have greater CSAs of the anterior
and posterior cruciate ligaments than a control group (75). Evidence also indicates that high-level spring board divers and figure
skaters have hypertrophied knee ligaments, especially on the
“drive leg” for divers and the landing leg of skaters (14). There is
also an accumulation of biochemical research showing increased
ligamentous cellular activities (e.g., stimulated proliferation of
fibroblasts) and collagen synthesis (directly measured or inferred
from mRNA expression) in response to mechanical strain of ligaments (86,97,111,144,148,197). Without more direct evidence
from training studies in humans, the degree of resistance training
(including squats)-induced adaptation in ligaments cannot be
ascertained. However, the literature suggests that resistance
training has substantial potential to alter ligament tissue leading
to reduced risks, severity of injuries, and can aid in injury prevention and a rehabilitation process back to play.
Many studies have been conducted to examine mechanical
stress on anterior cruciate ligament (ACL) during different types
and depths of squat. Most of these studies reported that bilateral
squats (performed to 90–110° knee angles and parallel) do not
place an alarming level of mechanical stress on the ACL, particularly compared with other modalities such as an isokinetic knee
extension (16,62,159,172,186,196,209). In addition, the PCL is
reported to undergo a greater level of mechanical tension during
a squat (to a 95° knee angle) than the ACL, although the level of
mechanical stress still seems to be much smaller than its maximum
tensile strength (60,161). These findings have 2 implications.
First, a squat can place mechanical stress on the anterior and
posterior cruciate ligaments without a high risk of injury.
Whether the level of mechanical stress provided by a squat is
sufficient to result in beneficial adaptations is still not clear because of the lack of research. However, the observed greater CSA
of the anterior and posterior cruciate ligaments in competitive
weightlifters, speed skaters, and divers supports the idea that the
level of mechanical stress can be sufficient to induce adaptations
of the morphology and potentially mechanical properties and
content particularly as weightlifters perform many squats (full
depth) on a regular basis (75). Second, the squat can be used
safely, particularly for rehabilitation at some point after an ACL
surgery. Previous studies have reported minimal levels of mechanical stress on the ACL during a squat (to 90 and 85° knee
angles) (16,60). However, for rehabilitation after a PCL surgery,
more caution should be exercised as a peak tensile force of approximately 1,500 to 2,200 N has been reported during a squat
(to a 85° knee angle) with a 12RM load (60). Although stance
width may play a role, these values seem to be below the reported
maximal tensile strength of the PCL of 4,000 N (60). Regarding
different variations of the squat, Kulas et al. (127) reported that
mechanical stress on the ACL is reduced when individuals are
instructed to moderately lean forward (75° internal knee angle)
during a unilateral squat. However, an upright unilateral squat
(75° internal knee angle) was still estimated to induce a peak
strain value of only 3.50% as compared with 2.94% of maximum
tensile strength with single-leg squat with forward trunk lean in
the ACL. The peak strain value of an upright unilateral squat is
comparable with strain values reported during the bilateral squat
(to a 90° internal knee angle) and is still small (16). At the same
time, this finding should be taken with caution as the study was
conducted without loading, and thus, the finding might not be
entirely applicable to loaded unilateral squats.
Bone. Bone tissues are also responsive to physical activities, especially closed kinetic chain exercises and are particularly responsive to mechanical stimuli of a large magnitude or of a high
loading rate (76). Of different types of physical activities, resistance training seems to be able to provide a potent stimulus for
bone (76,134). Resistance training increases bone mineral density, content, and mass over a wide range of age for both sexes
(76). Although, impact exercises such as hopping also induce
bone tissue adaptations; these adaptations are mainly observed
only in the proximal end of the femur (e.g., the femoral neck)
(134). Resistance training also induces bone tissue adaptations in
the L-spine and the femoral neck (134). Differences between
exercises are likely because of the heavy load placed on the axial
skeleton using resistance exercises, such as the squat. Moreover,
certain types of resistance training exercises are capable of providing a high rate of mechanical loading (e.g., explosive exercises
such as weightlifting movements and speed squats). Indeed,
weightlifters have been reported to have greater bone mineral
density both in the L-spine and femoral neck than age-matched
controls (36). Advantages of resistance training in providing
stimuli to bone seem to be the ability to provide a large magnitude
of loading progressively, and safely overloading specific areas
that are common sites of fracture such as L- and T-spines, greater
trochanter, and intertrochanteric and femoral neck regions, particularly under conditions of reduced bone mineral density, content, and, or mass (73,76).
The squat is effective in providing a mechanical stimulus to
bone tissues. Studies and reviews showed that weight-bearing
exercises are effective in inducing bone adaptations in the lowerextremity (e.g., femur trochanter and femoral neck) (76,98,151).
Furthermore, the squat places a high magnitude of mechanical
loading on the spine. This, in turn, results in bone tissue adaptations in the lumbar spine, which might be difficult with other
modes of exercise such as weight-supportive exercises (e.g.,
swimming) or typical impact exercises (e.g., running) (134,169).
Mosti et al. (145) reported that heavy ½ squat training using
a machine down to a 90° knee angle induced 2.9 and 4.9% increase in bone mineral content of the L-spine and femoral neck,
respectively, over the course of 12 weeks. Moreover, Dickerman
et al. (49) reported that a male powerlifter holding the squat
world record exhibited L-spine bone mineral density of ; 2 3
average men of the same age. In addition, the estimated spinal
loading during the world record squat was more than double the
previously estimated upper limit of compressive force for the
human spine. However, the powerlifter had a normal physical
examination, with no abnormalities in the spine (e.g., no
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Squats in Sport: Terminology and Biomechanics (2024) 38:8
neurological deficits, spinal pain, signs of compressive disc diseases, and neural foraminal canal stenosis). Synthesis of these
reports suggests that the squat may be one of the most effective
exercises to induce bone tissue adaptations at least in the spine
and the proximal end of the femur.
and reduce the likelihood and severity of injuries. (b) These
same adaptations are also expected to play an important role
in rehabilitation particularly in injuries that require restricted
use or immobilization of body parts and thus lead to consequential reduction in the CSAs and alterations in mechanical
properties of tendons, skeletal muscles, and ligaments. (c)
Intensity (e.g., levels of loading used) seems to be important
for the mechanical and morphological adaptations for at least
skeletal muscles, tendons, and bones. Therefore, intensity for
the squat and its variations should progressively become
greater while adhering to the concept of periodization and
recognized training principles.
Squats Mitigate the Risk of Lower Limb Injuries
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It is well-established that resistance training attenuates the risk of
sports injuries by increasing the structural strength of tendons,
ligaments, cartilage and connective tissues (63). Performing regular resistance training also increases joint stability through
greater muscle recruitment and enhanced rate of muscle activation that increases musculotendinous stiffness, resulting in more
support for a joint (188).
Heavy squats improve the overall and lower extremity
strength, which could reduce the risk of injury among athletes.
To evaluate this theory, Case and his colleagues investigated
the efficacy of relative strength level in 1RM barbell back
squats as a predictor of seasonal lower-extremity injuries.
Their data were collected from Division 1 male football players
and female volleyball and softball athletes. They reported
a significant difference between the relative back squat
strength among injured and uninjured athletes. The authors
concluded that male athletes with relative squat strength below
2.2 and female athletes below 1.6 in sports mentioned above
could be at a greater risk of lower-extremity injuries
throughout a sporting season.
Researchers in other sports also reported a significant difference in control of the lower extremities between injured and
noninjured athletes. For example, Dix et al. (51) reported
a larger hip abduction angle in female soccer players who suffered from ACL injuries. A larger hip abduction angle (valgus
knees) occurs during deceleration and cutting in soccer, which is
the result of suboptimal base strength and poor lower extremities control. The authors concluded that programs that address
proximal control and strength of lower extremities can prevent
ACL injuries in female soccer players. These findings were further supported by a study conducted on senior and junior female
Australian Rules Football and soccer players. The researchers
developed a multivariate prediction model consisting of countermovement jump peak take-off force, dynamic knee valgus,
and ACL injury history. Their prediction model classified ACL
injured from uninjured football players with a total accuracy of
78% (32).
Collectively, it seems that resistance training programs that
include heavy squats are not only beneficial to overall athletic
performance but also can reduce the risk of injuries in both sexes
by enhancing the structural strength of soft tissues, activation of
involved muscles, and increased joint stability.
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