Content uploaded by Diogo Cardozo
Author content
All content in this area was uploaded by Diogo Cardozo on Jul 10, 2016
Content may be subject to copyright.
Content uploaded by Diogo Cardozo
Author content
All content in this area was uploaded by Diogo Cardozo on Jul 05, 2016
Content may be subject to copyright.
Content uploaded by Diogo Cardozo
Author content
All content in this area was uploaded by Diogo Cardozo on Jul 02, 2016
Content may be subject to copyright.
Content uploaded by Diogo Cardozo
Author content
All content in this area was uploaded by Diogo Cardozo on Jul 02, 2016
Content may be subject to copyright.
Content uploaded by Diogo Cardozo
Author content
All content in this area was uploaded by Diogo Cardozo on Jul 02, 2016
Content may be subject to copyright.
Content uploaded by Diogo Cardozo
Author content
All content in this area was uploaded by Diogo Cardozo on Jul 02, 2016
Content may be subject to copyright.
HUMAN MOVEMEN T
43
JOINT-ANGLE SPECIFIC STRENGTH ADAPTATIONS INFLUENCE
IMPROVEMENTS IN POWER IN HIGHLY TRAINED ATHLETES
doi: 10.1515/humo-2016-0006
2016, vol. 17 (1), 43– 49
* Corresponding author.
MATTHEW R. RHEA1
*, JOSEPH G. KENN
2, MARK D. PETERSON
3, DREW MASSEY
4,
RObERTO SIMãO
5, PEDRO J. MARIN
6, MIKE FAVERO
7, DIOGO CARDOzO
5, 8, DARREN KREIN
9
1 A.T. Still University, Mesa, Arizona, USA
2 Carolina Panthers, National Football League, Charlotte, North Carolina, USA
3 University of Michigan, Ann Arbor, Michigan, USA
4 Game Time Sports and Training, Columbia, Tennessee, USA
5 Rio de Janeiro Federal University, Rio de Janeiro, Brazil
6 CYMO Research Institute, Valladolid, Spain
7 Logan High School, Logan, Utah, USA
8 Granbery Methodist College, Juiz de Fora, Brazil
9 Indianapolis Colts, National Football League, Indianapolis, Indiana, USA
AB STR ACT
Purpose. The purpose of this study was to examine the influence of training at different ranges of motion during the squat
exercise on joint-angle specific strength adaptations. Methods. Twenty eight men were randomly assigned to one of three
training groups, differing only in the depth of squats (quarter squat, half squat, and full squat) performed in 16-week training
intervention. Strength measures were conducted in the back squat pre-, mid-, and post-training at all three depths. Vertical
jump and 40-yard sprint time were also measured. Results. Individuals in the quarter and full squat training groups improved
significantly more at the specific depth at which they trained when compared to the other two groups (p < 0.05). Jump height
and sprint speed improved in all groups (p < 0.05); however, the quarter squat had the greatest transfer to both outcomes.
Conclusions. Consistently including quarter squats in workouts aimed at maximizing speed and jumping power can result in
greater improvements.
Key words: vertical jump, speed, squat depth, performance enhancement, sports conditioning
Introduction
The ultimate goal of a sports conditioning program
is to enhance each individual athlete’s athletic potential
through a structured program of physical development
and injury prevention [1]. To this end, specificity of train-
ing is a concept that should be of great importance to
sports conditioning professionals. The body will adapt
in very specific ways to meet the demands of a specific,
re-occurring stress [2]. Resistance training that mimics
the movements and demands of a given sport may en-
hance performance in that sport through specific ad-
aptations in neuromuscular performance.
Siff [2] detailed this concept in a more complex,
neurophysiologic manner stating that “it is vital to re-
member that all exercise involves information process-
ing in the central nervous and neuromuscular systems,
so that all training should be regarded as a way in which
the body’s extremely complex computing systems are
programmed and applied in the solution of all motor
tasks”. It is important to consider how the specific stress
applied to an athlete’s body in conditioning will effect
or stimulate the neuromuscular system, as well as how
conditioning can result in improved information pro-
cessing and physiological performance in specific sport
skills.
Accordingly, alterations in the range of motion for
a given exercise may, theoretically, result in different adap-
tations. Squat depth has been a topic of much discussion
in the field and literature [3–11] with primary focus
centering on strength improvements at different training
depths. More broadly, this debate is an issue of joint-angle
specificity, which has been examined for comparable
strength improvements [12–17]. The topic of joint-an-
gle specificity was initially examined with isometric
and isokinetic training, which was shown to increase
strength at or near the angles trained, and at or near
angular velocities trained, with little or no adaptation
at other angles/velocities [17].
Three primary squat depths have been characterized
and discussed in the literature [18], including partial/
quarter squats (40–60 degree knee angle), parallel/half
squats (70–100 degree knee angle), and deep/full squats
(greater than 100 degree knee angle). Range of motion
variation during the squat exercise influences various
biomechanical factors that relate to specificity of move-
ment pattern, and can affect the development of force,
rate of force development, activation and synchroniza-
M.R. Rhea et al., Joint-angle specific strength adaptations
44
HUMAN MOVEMEN T
tion of motor units, and dynamic joint stability. There-
fore, the manner in which an exercise changes based
on range of motion is an important concept to examine.
The purpose of this study was to examine the in-
fluence of training at different squat depths on joint-
angle specific strength as well as transfer to several sports-
related performance variables. Understanding the effects
of training at different ranges of motion can help the
strength and conditioning professional to apply the most
effective training strategy and further the performance
enhancement advantages of evidence-based training
prescriptions.
Material and methods
Subjects
Male college athletes of all sports at various schools
(Division I, II, III and Junior College) were invited to
participate in this research. Inclusion criteria included:
1) minimum of 2 years of consistent year-round training,
2) a minimum parallel squat 1RM of at least 1.5 times
body weight, and 3) no physical condition that would
impair aggressive sports conditioning and high-intense
resistance training. A total of 38 athletes volunteered
to participate. Of those, 32 met the minimum strength
requirement. Two subjects experiencing tendonitis in
the knee were excluded prior to group assignment.
Two subjects withdrew during the initial testing peri-
od, resulting in 28 total subjects entering the training
portion of the study. The methods and procedures for
this study were evaluated and approved by an Institu-
tional Review Board for research with Human Subjects
and all participants provided informed consent. The
majority (n = 24) of the subjects were football players,
with track (n = 1), basketball (n = 2), and wrestling (n = 1)
completing the sport backgrounds. Random assignment
resulted in 3 groups with similar anthropometric meas-
ures, strength, and training experience. Descriptive data
are presented in Table 1.
Procedures
Trained staff familiar with proper testing procedures
and data handling performed all testing. Those con-
ducting the pre-, mid-, and post-tests were blinded to
the group assignment of each subject to avoid any po-
tential bias. Experienced coaches implemented and over-
saw the training program to ensure proper execution,
tempo, and adherence to the prescribed program.
Strength testing was performed in accordance with
published guidelines of National Strength and Condi-
tioning Association [19]. Subjects performed one rep-
etition maximum (1RM) testing at each of the three
squat depths (quarter, half, and full) in three separate
sessions, randomized in order, with a minimum of 72
hours between testing sessions. All 1RM values were
achieved within 3 attempts. In a fourth and final testing
session designed to examine the reliability of the strength
data, each subject repeated the 1RM testing procedures
for each depth (Intraclass Correlation Coefficient rang-
ing from 0.95–0.98). Non-significant differences (p > 0.05)
were found between 1RM values on the different testing
days at each specific depth tested; however, the highest
1RM for each depth was utilized for data analysis. Testing
at week 8 was performed in a 7-day period with each
depth randomly tested on a separate day a minimum
of 48 hours apart. Post-intervention testing was per-
formed according to the same protocols explained for
the pre-testing.
Vertical jump testing was performed according to
protocols previously published [19]. Immediately fol-
lowing the dynamic warm-up in the first two testing
sessions, all subjects were tested for their vertical jump
using the Vertec (Vertec Sports Imports, Hilliard, OH).
Subjects were given 3 attempts with the maximum height
recorded. Non-significant differences were found be-
tween the two testing sessions (p > 0.05) but the highest
jump height was recorded for data analysis.
Sprint testing was performed according to protocols
previously published [19]. Following the dynamic warm-
up in the first two testing sessions, all subjects performed
a 40-yard sprint test. Electronic timing for the sprint
was conducted with a wireless timing system (Brower
Timing Systems, Draper, Utah). Subjects were given 2
attempts in each session with the maximum speed re-
corded. Non-significant differences were found between
the two testing sessions (p > 0.05) but the fastest speed
was recorded for data analysis.
All aspects of the training program were identical
for each group with the exception of squat depth and
absolute load. Within subject strength differences at
each depth, due to the biomechanical disadvantage
with increased depth, resulted in greater absolute loads
being used at quarter and half squat depths. However,
relative loads were the same for each group. The program
Table 1. Baseline Descriptive Data
Group Age
(years)
Weig ht
(kg)
Pre-Quarter 1RM
(kg)
Pre-Half 1RM
(kg)
Pre-Full 1RM
(kg)
Pre-V J
(cm)
Pre-40
(sec)
QTR 21.4 (3.2) 86.5 (25.6) 167.67 (13.95) 151.51 (15.12) 129.54 (17.23) 75.92 (15.06) 4.68 (0.18)
HALF 20.7 (2.1) 95.7 (32.1) 162.12 (12.22) 146.72 (11.54) 125.50 (14.09) 77.03 (11.05) 4.73 (0.18)
FULL 21.3 (1.3) 92.1 (23.8) 164.09 (13.18) 151.82 (12.80) 125.91 (18.38) 73.91 (14,25) 4.76 (0.20)
1RM – 1 repetition maximum, VJ – vertical jump, 40 – 40 yard sprint
M.R. Rhea et al., Joint-angle specific strength adaptations
45
HUMAN MOVEMEN T
followed a daily undulating periodization sequence with
intensity progressing from 8RM, 6RM, 4RM, to 2RM
then reverting back to 8RM. Training weight was esti-
mated using 1RM prediction equations based on the
1RM measures at the specific depth of training group,
with notations made for rep ranges in each workout
that required adjustments to the predicted values.
A split training routine was implemented to enable
greater monitoring and control of lower body exercises.
Lower body exercises (squats, power cleans, lunges, re-
verse hamstring curls, and step ups) were performed on
Monday and Thursday, and upper body exercises per-
formed on Tuesday and Friday. Squats (65%) and pow-
er cleans (25%) made up 90% of the training volume for
the lower body with the other exercises added for general
athletic preparation but at low volumes in each session
(1–3 sets) and were identical for all three groups. Exercise
order was kept constant for all groups and subjects.
Wednesday, Saturday, and Sunday were designated as
rest days with no exercise prescribed or allowed.
Lower body workouts included 4–8 sets of squats,
at the prescribed depth, followed by each of the other
exercises. A linear periodization adjustment in volume
was made throughout the training program (weeks 1–2:
8 sets; weeks 3–4: 6 sets; weeks 5–6: 4 sets; weeks 7–10:
8 sets; weeks 11–14: 6 sets; weeks 15–16: 4 sets). A three-
minute rest was provided between each set. This re-
sulted in total volume, relative intensity, and workout
sessions that were equated across the 16-week training
intervention for all groups.
Squat depth was taught and monitored via video-
taping throughout the training program. The first group
performed full squats (FULL) with range of motion de-
termined by the top of the thigh crossing below parallel
to the floor and knee angles exceeding 110 degrees of
flexion. The half squat group (HALF) trained at depths
characterized by the top of the thigh reaching parallel
to the floor with knee angles approximately 85–95 de-
grees of flexion. The final group performed quarter
squats (QTR) with range of motion involving a squat
to approximately 55–65 degrees of knee flexion. Dur-
ing the initial sessions, and during all testing, a goni-
ometer (Orthopedic Equipment Company, Bourbon,
Indiana) was used to measure the appropriate depth.
Safety bars were raised or lowered in the squat rack
for each subject to provide a visual gauge of the depth
required. The coach provided immediate feedback if
a slight alteration in depth was needed within a set.
A minimum of 30 workouts (out of 32) was required
to be included in the final data analysis. This ensured
that all subjects included in the analysis had completed
roughly the same amount of work throughout the pro-
gram. All 28 subjects met this requirement.
Statistical analyses
Data were analyzed using PASW/SPSS Statistics 20.0
(SPSS Inc, Chicago, IL, USA). The normality of the data
was checked and subsequently confirmed with the Sha-
piro–Wilk test. Dependent variables were evaluated with
a repeated measures analysis of variance (ANOVA) on
group (QTR; HALF; FULL) × time (Baseline; Mid; Post).
When a significant F-value was achieved, pairwise com-
parisons were performed using the Bonferroni post hoc
procedure. The level of significance was fixed at p 0.05.
Partial Eta squared statistics ( 2) were analyzed to de-
termine the magnitude of an effect independent of sam-
ple size. Pre/Post effect sizes were calculated for each
group and performance measure [20]. The coefficient
of the transfer was then calculated from squat result
gains to vertical jump and sprinting speed via a calcu-
lation reported by Zatsiorsky [21]:
Transfer = Result Gain in nontrained exercise/Re-
sult Gain in trained exercise
Result Gain = Gain in performance/Standard de-
viation of performance
The associations between different measures were
assessed by Pearson product moment correlation at base-
line time. Values are expressed as mean ± SD in the text,
and as mean ± SE in the figures.
Results
Quarter squat – 1RM-test
A group × time interaction effect was noted for quar-
ter squat test (p = 0.002; 2 = 0.545; see Figure 1a). A main
effect of the group was observed (p < 0.001; 2 = 0.652),
as well as a main effect of the time was noted (p = 0.012;
2 = 0.322).
Half squat – 1RM-test
A group × time interaction effect was noted for half
squat test (p < 0.001; 2 = 0.563; see Figure 1b). However,
there was no significant a main effect of the group was
observed (p > 0.05; 2 = 0.002). A main effect of the time
was noted (p < 0.001; 2 = 0.930).
Full squat – 1RM-test
A group × time interaction effect was noted for full
squat test (p < 0.001; 2 = 0.647; see Figure 1c). However,
there was no significant a main effect of the group was
observed (p = 0.074; 2 = 0.278). A main effect of the
time was noted (p < 0.001; 2 = 0.623).
Vertical Jump Test
A group × time interaction effect was noted for ver-
tical jump test (p < 0.001; 2 = 0.689; see Figure 2).
However, there was no significant a main effect of the
group was observed (p > 0.05; 2 = 0.146). A main ef-
fect of the time was noted (p < 0.001; 2 = 0.795).
M.R. Rhea et al., Joint-angle specific strength adaptations
46
HUMAN MOVEMEN T
Sprint Test
A group × time interaction effect was noted for ver-
tical jump test (p < 0.001; 2 = 0.615; see Figure 3). How-
ever, no significant main effect of the group was observed
(p > 0.05; 2 = 0.232). A main effect of the time was
noted (p < 0.001; 2 = 0.836).
Percent change (Table 2) and effect size calculations
(Table 3) demonstrated the greatest changes in strength
at the specific depth at which each group trained. QTR
squat improved 12% in the quarter squat 1RM, HALF
14% at half 1RM, and FULL improved 17% in the full
squat 1RM. For VJ and 40-sprint, the QTR squat group
showed the greatest treatment effect (VJ: 0.75; Sprin:
–0.58), followed by HALF (VJ: 0.48; Sprint: –0.35),
with FULL showing the lowest magnitude of training
effect (VJ: 0.07; Sprint: –0.10). Transfer calculations
(Table 4) somewhat mimicked the other trends in the
data with QTR showing the greatest transfer to VJ (0.53),
with HALF next (0.28), and FULL showing the least
amount of transfer (0.06). For sprinting speed, QTR
showed the greatest transfe (–0.41) with HALF second
(–0.20) and FUL (–0.09) again showing the least trans-
fer. Finally, correlation analysis (Table 5) demonstrated
stronger relationships between the QTR squat group
and both VJ (r = 0.64) and Sprint (r = –0.74) perfor-
mances followed by HALF (r = 0.43 and r = –0.57) and
FULL (r = 0.31 and r = –0.49).
Discussion
Taken collectively, these findings support the use of
shortened ranges of motion during squat training for
improvements in sprint and jump performance among
highly trained college athletes. This conclusion should
stimulate further consideration among strength and con-
* significantly different from Baseline (p < 0.05)
# significantly different from Mid (week 8) (p < 0.05)
† significantly different compared with the QTR group (p < 0.05)
‡ significantly different compared with the HALF group (p < 0.05)
Figure 1. Squat tests. Values are mean ± SE (QTR Group,
n = 9; HALF Group, n = 9; FULL Group, n = 10)
* significantly different from Baseline (p < 0.05)
# significantly different from Mid (week 8) (p < 0.05)
† significantly different compared with the QTR group (p < 0.05)
Figure 2. Vertical Jump Test. Values are mean ± SE
(QTR Group, n = 9; HALF Group, n = 9;
FULL Group, n = 10)
* significantly different from Baseline (p < 0.05)
# significantly different from Mid (week 8) (p < 0.05)
† significantly different compared with the QTR group (p < 0.05)
Figure 3. Sprint test. Values are mean ± SE (QTR Group,
n = 9; HALF Group, n = 9; FULL Group, n = 10)
M.R. Rhea et al., Joint-angle specific strength adaptations
47
HUMAN MOVEMEN T
ditioning coaches regarding the use of quarter squats in
a sports conditioning program. Further examination of
the risks, benefits, and implementation of squats of var-
ious depths is warranted, and will be discussed here.
Weiss et al. [7] conducted a study examining deep
and shallow squat (corresponding to half and quarter
squats in our study) and leg press training on vertical
jump among untrained college students. Their study
failed to find any significant changes in vertical jump for
either group regardless of squat depth but two transfer
calculations suggested greater transfer from the half
squat training program to vertical jump. They did find
statistically significant improvements in 1RM squat at
the angle of training. The half squat group also improved
1RM at the quarter squat depth; however, the quarter
squat training group did not improve 1RM performance
in the half squat test. Our findings concur with the
joint-angle specific improvement in strength relative
to the angle where training occurred but differ in that
our study did not show an improvement in quarter
squats in the half or full squat training groups. Addi-
tionally, we found far less transfer from deep squat training
to vertical jump. Several distinct differences exist be-
tween these two studies, perhaps accounting for the dif-
ferent findings. Our study utilized very highly trained
athletes training with free weights instead of untrained
college students who trained with machines. Our study
was also nearly twice the length (16 weeks compared
to 9 weeks). It is notable that in our study, the mid-test
data (8 weeks) showed no significant findings, highlight-
ing the need for longer studies to examine these impor-
tant training issues more critically. It is also possible that
as an individual becomes more highly trained, joint-
angle specific adaptations are more pronounced and
detectable.
Joint-angle specificity has been suggested to relate to
neurological control [17]. Thepaut-Mathieu et al. [14]
found increases in EMG activity at trained joint angles
Table 2. Percet changes in performane measures
Group Quarter Squat Half Squat Full Squat VJ 40 sprint
QTR 0.12 0.06 0.02 0.15 –0.02
HALF 0.07 0.14 0.00 0.07 –0.01
FULL 0.00 0.05 0.17 0.01 0.00
VJ – vertical jump; 40 – 40 yard sprint
Table 3. Effect size calculations based on squat depth
Group Quarter 1RM Half 1RM Full 1RM VJ 40 sprint
QTR 1.41 0.62 0.12 0.75 –0.58
HALF 0.88 1.76 0.02 0.48 –0.35
FULL 0.05 0.59 1.14 0.07 –0.10
ES – (post-pre)/pre-test SD
Table 4. Coefficient of transfer calculations
Group Quarter 1RM Half 1RM Full 1RM VJ 40 sprint
QTR 1.00 0.44 0.08 0.53 –0.41
HALF 0.51 1.00 0.01 0.28 –0.20
FULL 0.05 0.52 1.00 0.06 –0.09
coefficient of transfer – result gain in nontrained exercise/result gain in trained exercise
Table 5. Bivariate correlations between strength capacities at different squat depths, vertical jump height, and sprint speed
(n = 28)
Group Quarter 1RM Half 1RM Full 1RM VJ 40 sprint
Quarter 1RM 1 0.847** 0.722** 0.6 40** – 0 .740 **
Half 1RM 0.847** 10.693** 0.428* – 0. 567**
Full 1RM 0.722** 0.693** 10.309 –0.490**
VJ –0.640** 0.428* 0.309 1– 0.779**
Sprint 0.740** – 0.567** – 0.490** –0.779** 1
** correlation is significant at the 0.01 (2-tailed)
M.R. Rhea et al., Joint-angle specific strength adaptations
48
HUMAN MOVEMEN T
compared to untrained joint angles suggesting an increase
in neural drive at the specific angles trained. Those data
highlight the complexity of the nervous system pro-
cesses for gathering information and responding to motor
challenges. It appears that the nervous system gathers
information relative to joint angles, contraction type, and
angular velocities during training, responding with adap-
tations specific to those training demands.
An examination of the differences in squat 1RM at
the three different depths in the current study provides
valuable information relative to joint-angle specific loads
and may assist in the development of an explanation
of why quarter squats transfer more to jumping and
sprinting speed. First, the quarter squat range of motion
matches more closely the hip and knee flexion ranges
observed in jumping and sprinting. That said, on average,
athletes were able to squat 30–45% more in a quarter
squat compared to the full squat depth (10–20% more
when compared to half squat depth). Using 1RM test-
ing at full squat depths to calculate and apply training
loads through a full squat range of motion, results in
training loads at the top of the range of motion repre-
senting less than 70% of maximum lifting capacity in
that range of motion. Consistently training at 60–80%
of maximum capacity may promote strength gains in
less trained populations but would not be considered
sufficient for optimal strength development among more
highly trained populations [22]. Quarter squats would
not be expected to improve full squat strength due to
the lack of stress applied in full squat joint angles and the
data in the current study supports that assertion. But
the load during full squats appears to be insufficient
to promote significant gains in strength in the quarter
squat joint angles in highly trained populations. Thus,
the loads that are calculated for training are specific to
the joint angles at, or near, the angle at which testing
occurs. They do not represent optimal training loads for
all angles in the range of motion.
Isometric research [15] has shown that strength im-
provements only occur at or near the joint-angles where
training occurs. Our data support this concept, as all of
our groups were similar in gains at the half squat depth;
however, significant differences were found at quarter
and deep squats based on the training depths. The con-
cept of joint-angle specificity as it relates to resistance
training has generally been described as improvements
in function at the joint-angles where training occurs.
Under this philosophy, conventional thought has sug-
gested that athletes must train through a full range of
motion to ensure adaptations at all joint-angles. Given
the data of the current study, it seems that strength im-
provements are specific to joint-angles that are sufficiently
overloaded, not just joint-angles where training occurs.
Therefore, we propose a change in perspective, based
on the current data and theory, to reflect the concept
of joint-angle overload.
It is suggested that improvements in muscular fit-
ness will occur at the joint-angles that are sufficiently
overloaded by the load placed upon them. In the con-
ventional approach to measuring 1RM values at either
a parallel or deep squat depth, and then performing
squats at a certain percentage of that 1RM through
a parallel or deep squat range of motion, the joint-angles
involved in jumping and sprinting may not be sufficiently
overloaded for maximal gains. Returning to the con-
cepts proposed by Siff [2] regarding information pro-
cessing during training, it is suggested that the neuro-
muscular system perceives, and adapts to, stresses applied
during quarter squats much differently than full squats.
It is also important that the strength and condition-
ing professional differentiate between transfer and value.
If the goal of a specific workout were to enhance sprint-
ing or jumping, quarter squats would be the most ef-
fective range of motion based on the current data. But
other squat depths may have value in preparing the
athlete for competition, and coaches should examine
the benefits, and risks, associated with squats of varying
depths. If or when value exists, regardless of the amount
of transfer directly to a given sports skill, an exercise or
range of motion should be used to ensure that the athlete
gains the full value of that exercise.
Different EMG activation patterns have been shown
with various squat depths [10] and may provide evidence
of specific value outside of transfer to sport skills. Full
squats were shown to result in greater gluteus maximus
activation with decreased hamstring involvement. Thus,
squat depth may preferentially target recruitment of dif-
ferent muscle groups. Understanding the exact benefits
or drawbacks of different exercises and ranges of motion
is imperative to optimal training and strength and con-
ditioning professionals should place high value on edu-
cating themselves and their clients regarding the pros
and cons of a certain exercise or range of motion.
An additional consideration when selecting squat
variations is the different stresses that each variation
presents to the athlete. Schoenfeld [18] provides a de-
tailed review of the various stresses that occur at the
ankle, knee, and hip joints during the squat exercise at
various depths. With changing loads and ranges of mo-
tion, stress appears to vary substantially. The increased
load in a quarter squat, combined with the increased
anterior shear force in that range, could present added
risk of overuse injury if athletes only performed quar-
ter squats. The same could be said of all squat depths
and the best approach for health and performance en-
hancement may be to include different squat variations
(i.e. back, front, split) at all three squat depths. Squats
of different depths may need to be considered as sepa-
rate exercises, or tools, employed for various purposes
or to target specific muscles. A mixture of different squat
depths, much like the use of various different exercises
throughout a training program, may be the optimal ap-
proach to developing the total athlete. However, based
on the data from this study, it is clear that the use of qua r-
ter squats is not only helpful, but also necessary for pro-
moting maximal sprinting and jumping capabilities.
M.R. Rhea et al., Joint-angle specific strength adaptations
49
HUMAN MOVEMEN T
Conclusions
In summary given the significantly greater transfer
to improvements in sprinting and jumping ability, the
use of quarter squats during sports conditioning is recom-
mended. Including quarter squats in workouts aimed
at maximizing speed and jumping power can result in
greater improvements in sport skills. While squats throug h
a full range of motion may be useful in a general sports
conditioning regimen, strength and conditioning pro-
fessionals should consider the integration of quarter
squats for maximizing sprinting and jumping ability.
References
1. Kenn J., The coach’s strength training playbook. Coaches
Choice, Monterey 2003.
2. Siff M.C., Supertraining. Supertraining Institute, Denver,
Colorado 2003.
3. Chandler T.J., Wilson G.D., Stone M.H., The squat exer-
cise: attitudes and practices of high school football coaches.
Natl Strength Cond Assoc J, 1989, 11 (1), 30–36.
4. Chandler T.J., Wilson G.D., Stone M.H., The effect of the
squat exercise on knee stability. Med Sci Sports Exerc,
1989, 21 (3), 299–303. Available from: http://journals.
lww.com/acsm-msse/pages/articleviewer.aspx?year=19
89&issue=06000&article=00012&type=abstract
5. Klein K.K., The deep squat exercise as utilized in weight
training for athletes and its effects on the ligaments of
the knee. JAPMR, 1961, 15 (1), 6–11.
6. Wilson G.J., Newton R.U., Murphy A.J., Humphries B.J.,
The optimal training load for the development of dynamic
athletic performance. Med Sci Sports Exerc, 1993, 25 (11),
1279–1286. Available from: ournals.lww.com/acsm-msse/
pages/articleviewer.aspx?year=1993&issue=11000&art
icle=00013&type=abstract.
7. Weiss L.W., Frx A.C., Wood L.E., Relyea G.E., Melton C.,
Comparative effects of deep versus shallow squat and leg-
press training on vertical jumping ability and related
factors. J Strength Cond Res, 2000, 14 (3), 241–247.
8. Escamilla R.F., Knee biomechanics of the dynamic squat
exercise. Med Sci Sports Exerc, 2001, 33 (1), 127–141.
Available from: http://journals.lww.com/acsm-msse/pages/
articleviewer.aspx?year=2001&issue=01000&article=
00020&type=abstract.
9. Rogers L., Sherman T., Leg press versus squat. Strength
Cond J, 2001, 23 (4), 65 – 69.
10. Caterisano A., Moss R.F., Pellinger T.K., Woodruff K.,
Lewis V.C., Booth W. et al., The effect of back squat depth
on the EMG activity of 4 superficial hip and thigh mus-
cles. J Strength Cond Res, 2002, 16 (3), 428–432.
11. Drinkwater E.J., Moore N.R., Bird S.P., Effects of changing
from full range of motion to partial range of motion on
squat kinetics. J Strength Cond Res, 2012, 26 (4), 890– 896,
doi: 10.1519/JSC.0b013e318248ad2e.
12. Lindh M., Increase of muscle strength from isometric
quadriceps exercises at different knee angles. Scand J
Rehabil Med, 1979, 11 (1), 33 –36 .
13. Knapik J.J., Mawdsley R.H., Ramos M.U., Angular speci-
ficity and test mode specificity of isometric and isokinetic
strength training. J Orthop Sports Phys Ther, 1983, 5 (2),
58–65, doi: 10.2519/jospt.1983.5.2.58.
14. Thepaut-Mathieu C., Van Hoecke J., Maton B., Myoelec-
trical and mechanical changes linked to length speci-
ficity during isometric training. J Appl Physiol, 1988, 64 (4),
1500 –1505.
15. Kitai T.A., Sale D.G., Specificity of joint angle in isometric
training. Eur J Appl Physiol Occup Physiol, 1989, 58 (7),
744–748, doi: 10.1007/BF00637386.
16. Weir J.P., Housh T.J., Weir L.L., Electromyographic evalu-
ation of joint angle specificity and cross-training after iso-
metric training. J Appl Physiol, 1994, 77 (1), 197–201.
17. Weir J.P., Housh T.J., Weir L.L., Johnson G.O., Effects
of unilateral isometric strength training on joint angle
specificity and cross-training. Eur J Appl Physiol Occup
Physiol, 1995, 70 (4), 337–343, doi: 10.1007/BF00865031.
18. Schoenfeld B.J., Squatting kinematics and kinetics and
their application to exercise performance. J Strength
Cond Res, 2010, 24 (12), 3497–3506, doi: 10.1519/
JSC.0b013e3181bac2d7.
19. Baechle T.R., Earle R.W., Essentials of strength training
and conditioning. 3rd edition. Human Kinetics, Cham-
paign 2008.
20. Rhea M.R., Determining the magnitude of treatment
effects in strength training research through the use of
the effect size. J Strength Cond Res, 2004, 18 (4), 918–920.
21. Zatsiorsky V.M., Science and practice of strength train-
ing. Human Kinetics, Champaign 1995.
22. Rhea M.R., Alvar B.A., Burkett L.N., Ball S.D., A meta-
analysis to determine the dose response for strength devel-
opment. Med Sci Sports Exerc, 2003, 35 (3), 456–464, doi:
10.1249/01.MSS.0000053727.63505.D4.
Paper received by the Editor: September 22, 2015
Paper accepted for publication: March 21, 2016
Correspondence address
Matthew Rhea
Kinesiology Department
A.T. Still University
5850 East Still Circle, Mesa
AZ 85206, USA
e-mail: mrhea@atsu.edu
