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Electromyographic activity in superficial muscles of the thigh and hip during the back squat to three different depths with relative loading

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Introduction: Inconclusive previous research on squat depth and the evoked electromyography (EMG)activity muddles our understanding of muscle recruitment in the back squat. This study determined EMGactivity as a function of squat depth in four superficial muscles of the lower limb using relative loading. Method: Eight resistance trained males (mean ± SD age: 21 ± 1 years) performed back squats to partial,parallel and full depth using depth-relative 5-repetition–maximum loads. Muscle activity in the vastus medialis oblique (VMO), vastus lateralis (VL), gluteus maximus (GM), and biceps femoris (BF) during the concentric and eccentric phases of the squat was determined using surface electromyography. Peak (PeakEMG), mean (Mean EMG), and integrated (iEMG) EMG normalised to their respective maximum voluntary isometric contraction (MVIC) for each muscle were evaluated. Results: Three-way Anovas and Sidak post-hoc analysis revealed significant effects for squat type (p =0.021 - 0.001), squat phase (p = 0.001), and muscle (p = 0.001). The significant differences were between the partial and the parallel squat (p = 0.016 - 0.001); for iEMG significant effects were also found between the partial and full squat (p = 0.001). The VMO elicited the highest EMG activity (e.g., Peak EMG 93.4 ± 36.9%MVIC; parallel squat, concentric) and the BF the lowest (e.g., Peak EMG 49.9 ± 14.7%). Greater GM activity occurred in parallel squats compared to full squats (mean difference in Peak EMG = 9.1% MVIC). Conclusion: The findings suggest that squatting to the parallel position or lower induces optimal contractile stimulation of the quadriceps. Squatting to parallel depth maximises EMG activation of the GM, possibly due to a more advantageous external moment arm or a reduction in neural drive at greater depths.
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Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 57
ISSN 2201-5655 © 2016, Australian Institute of Fitness
ORIGINAL RESEARCH
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Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 58
INTRODUCTION
The free barbell back squat is a closed-chain,
multi-joint movement frequently incorporated into
the strength and conditioning programmes of
athletes 1,2,WLVLPSHUDWLYHWKDWFRDFKHVDUHHTXLSSHG
with underlying research evidence regarding the
contribution of different muscles of the lower limb
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in the lifting technique are applied in an attempt to
target certain muscle groups by altering the joint
torques 3,4+RZHYHUWKHSK\VLRORJLFDOVWUHVVHV
associated with high levels of muscle activity and
time-under-tension are central to stimulating a
training effect 5; simply shifting joint torques does
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determine the potential effectiveness of an exercise
variation and the associated neuromuscular adaptive
stimulus 6; whereby, measures typically include peak
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which an athlete descends in the squat is one
approach that may permit favourable outcomes in
muscle activity and concomitant physiological
perturbations, and hence optimise neuromuscular
DGDSWDWLRQVLQDWKOHWHV([LVWLQJOLWHUDWXUHVXSSRUWV
that small alterations in squat technique can impact
on the muscle activity evoked 77KHWKUHHVTXDW
depths most commonly adopted in strength training
are the partial squat, parallel squat, and full squat 8,9
It has been reported that with increased hip and
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these joints increases in the concentric phase 5$Q
increase in muscle activity and concomitant stimuli
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+RZHYHU%U\DQWRQet al. 5 used inverse dynamics to
compute net joint moments and an isokinetic
dynamometer matched for joint angle at each squat
depth to establish a maximal force for relative
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moments are a product of both mechanical leverage
and muscle tension, and involve all muscles acting to
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analysis must be employed for the analysis of the
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depths is the research by Caterisano and colleagues
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partial, parallel and full squats during the concentric
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Previous research report that lifted load decreases
with squat depth due to mechanical factors that
include a greater range of motion through which the
load must be moved and thus an increased time
under tension and concomitant demands on the
muscle, and an unfavourable length-tension
relationship created by the increased muscle lengths
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strategy is required in the squat movement since the
joint moments, muscle activity, relative contribution
of the lower limb joints, and lifted load are
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limitation of previous research 10, the same absolute
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Therefore, the maximum exercise intensity possible
at each depth was not used; posing implications for
muscle activity 1,57KHJUHDWHULQWHQVLWLHVDVVRFLDWHG
with increased squat depth would thereby ostensibly
elicit greater muscle activity in the prime movers 5,7
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5HVHDUFK13 found a sudden increase in hip and
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from full squats, consistent with pertinent literature
regarding increases in activity after transitioning from
the eccentric to the concentric phases of the
movement 2,4+RZHYHUWKHUHVXOWVRI 5REHUWVRQet
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parallel depth only; however, the study does not
compare muscle activity between squats to different
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Unlike the quadriceps femoris, which have
demonstrated near maximal levels of recruitment
Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 59
during full squats 13, hamstring activity during the
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contributing minimally to the movement in terms of
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times less activity in the hamstrings muscles relative
to the quadriceps; however, squat depth comparisons
DUHODUJHO\DEVHQW*RUVXFKDQGFROOHDJXHV15
examined the effect of squat depth on the
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the vasti are moderately-to-highly active, while the
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in the back squat 13$OVRWKHOLWHUDWXUHLVHTXLYRFDO
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in the back squat; intensities which are most
conducive to maximal strength development 16
Therefore, the aim of this study was to determine
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at different depths of the back squat using relative
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METHODOLOGY
Experimental Design
Participants were requested to attend three data
collection sessions separated by at least 72 hours to
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instantaneous changes in muscle activation to be
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amplitude over the entire movement 177KHL(0*
best illustrates mechanical work performed by the
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VKDQNDQJOHRI DSSUR[LPDWHO\)LJXUH7KH
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determined based on the acetabulofemoral joint
distinctly below the horizontal plane of the knee
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the instant the desired squat depth was reached, an
investigator situated to the side of the participant
provided verbal cues to participants instigating the
concentric portion of the lift; video analysis was used
to verify that each depth was achieved 107RDFFRXQW
for circadian variations 6, experimental testing and
09,&WULDOVZHUHXQGHUWDNHQFRQVLVWHQWO\EHWZHHQ
••
Figure 1. Partial (a), parallel (b) and full squat (c) depths.
Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 60
WKHKRXUVRI DPDQGSP)XUWKHUPRUH
participants were asked to abstain from any lower
body resistance training or exhaustive activity in the
48 hours preceding all testing to ensure no muscle
soreness was present that may have compromised
WKHYDOLGLW\RI WKHGDWD7HVWLQJZDVFRQGXFWHGXVLQJ
a randomised and counterbalanced repeated
measures design to mitigate order effects 18
Participants
(LJKWKHDOWK\PDOHVRI PHDQ6'DJHRI 
years, height of 176 ± 5 cm, mass of 80 ± 9 kg, and
training experience in the free barbell back squat of 5
\HDUVZHUHUHFUXLWHG([FOXVLRQFULWHULD
encompassed a history of lower body injury or
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preventing full squat depth reached safely using
correct squatting technique was contraindicated 19, as
ZDVH[FHVVLYHOXPEDUÁH[LRQDWWULEXWDEOHWRLQKHUHQW
anatomical or immobility induced posterior pelvic tilt
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E\DQH[SHULHQFHG6WUHQJWK&RQGLWLRQLQJFRDFKE\
ascertaining whether the participants were able to
maintain heel contact with the ground during full
VTXDWVDQGH[FHVVLYHOXPEDUÁH[LRQZDVJDXJHG
visually by the coach based on own experience and
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participants elicited medium and large statistical
effect sizes 207KHVWXG\ZDVDSSURYHGE\WKH(WKLFV
&RPPLWWHHDW(GJH+LOO8QLYHUVLW\
Squat Technique
Participants performed the back squat wearing
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shoulder width apart while maintaining a naturally
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was held using a pronated grip at a width as narrow
DVVKRXOGHUÁH[LELOLW\DQGWKRUDFLFPRELOLW\ZRXOG
permit, and placed behind the neck across the upper
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retracted 16'XULQJWKHVTXDWWKHNQHHVZHUHDOLJQHG
with the toes and tracked them throughout the
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rotation of the hips was given to facilitate this action
and mitigate gravity induced hip adduction torque
and deleterious knee valgus in the presence of
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lumbar and thoracic spinal regions maintained their
natural or slightly extended curvatures throughout
the movement, with slight hyperextension of the
cervical spine, as participants faced forward 22
/XPEDUDQGWKRUDFLFVSLQDOFXUYDWXUHDQGIRUZDUG
lean were visually monitored by the experienced
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excessive forward lean was when the hips rose up too
quickly relative to the shoulders from the start of the
ascent, in which case the data were discarded and the
trial repeated 103DUWLFLSDQWVZHUHLQVWUXFWHGWR
´FRQWUROµWKHLUGHVFHQWDQGQRWWR´ERXQFHµRII 
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were permitted due to their attenuation effect on
(0*DFWLYLW\1
Familiarisation Trial and 5RM Procedures
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common place in strength training programs and
within the recommended repetition range for
developing maximum strength 167KH50ORDGDW
each depth was used to allow the prescription of
relative loading 7'XULQJDIDPLOLDULVDWLRQVHVVLRQ
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kg at each squat depth; ten minutes recovery was
SURYLGHGEHWZHHQWKH50WULDOV17KHSDUWLFLSDQWV
performed two warm up sets before attempting the
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consideration to circadian rhythm 6DOO50WULDOV
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Electromyography Procedures
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guidelines and oriented parallel with the muscle
Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 61
ÀEUHV27RUHGXFHVLJQDODUWHIDFWWKHVNLQDWWKHVLWHV
of electrode placement was shaved, and cleansed
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connected to the electrodes via a two-snap lead and
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These modules housed a reference electrode which
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relayed wirelessly from the modules to the telemetric
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MVICs
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normalisation technique 24 and its exclusivity in
providing estimates of the degree of motor-unit
recruitment relative to a muscle’s maximum
activation potential, permitting comparisons between
muscles 18,237KHIROORZLQJWDVNVKDYHEHHQLGHQWLÀHG
as eliciting maximum muscle activity and were
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was performed with the participants assuming a
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approximately 90° and full extension of their right
hip 217KHYDVWL09,&VZHUHDFKLHYHGZKLOHVHDWHG
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approximately 60° and 90°, respectively 25$SSO\LQJ
a resistance great enough to deny movement, a
maximum effort knee extension was then performed
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DQGRI KLSÁH[LRQZKLOHVHDWHG25,26; though a
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pad placed atop the upper thighs prevented any
unwanted movement of the thighs or hips during the
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cue to contract the muscle as quickly as possible 1
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isometric efforts were performed for each muscle
group, intervened by a minimum of two minutes to
lessen fatigue effects 17KHKLJKHVW(0*UHDGLQJ
obtained from these repetitions subsequently
denoted the normalisation reference for the
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Experimental Procedures
Participants undertook a standardised warm-up,
comprising activation exercises, dynamic stretching
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incremental warm-up sets of 6 repetitions at 40%,
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the warm-up, participants performed 3 consecutive
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repetitions, rather than 5, were used to circumvent
possible fatigue induced deterioration of technique
that may affect relative muscle contribution during
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set up perpendicular to the line of action at
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the partitioning of data into respective concentric
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variable physiological and biochemical states and
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consequentially compromising the reliability of data
23,247KLVWHFKQLTXHKDVSUHYLRXVO\GHPRQVWUDWHG
KLJKLQWUDFODVVFRUUHODWLRQFRHIÀFLHQWV,&&V 
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back squat 29(DFKWULDOZDVLQWHUVSHUVHGZLWKWHQ
minutes of rest to allow fatigue to fully dissipate and
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back squat was performed inside a power rack, while
Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 62
two spotters, one at each end of the barbell, were
present during each lift to ensure safety 16
Statistical Analyses
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normality of raw data assumption was performed
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44SORWV$VVHVVPHQWRI WKHQRUPDOLW\RI UHVLGXDOV
and homogeneity of residuals assumptions was
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inspect homoscedasticity, and Cook’s distance 305DZ
data were mathematically transformed using a
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L(0*ZLWKLQVTXDWW\SHVVTXDWSKDVHVDQGPXVFOH
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tests were performed on any measure that achieved a
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2 was
interpreted based upon the guidelines of 20; that is, a
Ƨp
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0
20
40
60
80
100
120
140
VMO VL GM BF
% M VIC
Muscle ( Concentr ic)
Partial Parallel Full
0
20
40
60
80
100
120
140
VMO VL GM BF
% M VIC
Muscle ( Eccentr ic)
Partial Parallel Full
0
20
40
60
80
100
120
140
VMO VL GM BF
% M VIC
Muscle ( Concentr ic)
Partial Parallel Full
0
20
40
60
80
100
120
140
VMO VL GM BF
% M VIC
Muscle ( Eccentr ic)
Partial Parallel Full
0
20
40
60
80
100
120
140
VMO VL GM BF
% M VIC
Muscle ( Concentr ic)
Partial Parallel Full
0
20
40
60
80
100
120
140
VMO VL GM BF
% M VIC
Muscle ( Eccentr ic)
Partial Parallel Full
Figure 2. Peak EMG presented as mean + SD normalised to
MVIC.
Figure 3. Mean EMG presented as mean + SD normalised to
MVIC.
Figure 4. iEMG presented as mean + SD normalised to MVIC.
Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 63
SDUDOOHO902 9/ IXOO902 
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activity of the vasti in the parallel compared to the
partial squat is likely due to the mechanical
disadvantage that occurs as a result of the initial
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reported 1 that during concentric contractions, neural
drive to the quadriceps is greater for intermediate
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the quadriceps femoris in the partial squat may in
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rates 11HJOLJLEOHGLIIHUHQFHVLQ(0*DFWLYLW\ZHUH
found between the parallel and full squats in both
YDVWLPXVFOHVIRUDOO(0*SDUDPHWHUV7KLVÀQGLQJLV
in agreement with Wretenberg and colleagues 31, who
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9/EHWZHHQSDUDOOHODQGIXOOVTXDWV+RZHYHU
5REHUWVRQ et al. 13IRXQGWKDWSHDN9/DFWLYLW\ZDV
maximum at the bottom of the squat suggesting that
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RESULTS
0HDQ6'3HDN(0*0HDQ(0*DQGL(0*
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(0*DFWLYLW\ZDVKLJKHULQWKHFRQFHQWULFSKDVH
7KHJHQHUDOWUHQGRI (0*DFWLYLW\ZDVFKDUDFWHULVHG
by a progressive reduction in activity in the order
902KLJKHVWDFWLYLW\9/*0%)ORZHVW
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2 yielded medium and large effects
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DISCUSSION
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9/ GXULQJWKHFRQFHQWULFSKDVH)LJXUHV
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Table 1: Statistically signicant results of the three-way Anova
and Sidak post-hoc statistical tests (Peak EMG).
Variables F
ratio df pȘp2power
Squat type 4.1 2,156 0.018 0.05 0.72
Squat phase 228.0 1,156 0.001 0.61 1.00
Muscle 101.0 3,156 0.001 0.67 1.00
Squat type * Phase 9.2 2,156 0.001 0.11 0.98
Squat phase * Muscle 10.3 3,156 0.001 0.17 1.00
Sidak post-hocs
Squat type
Partial vs. parallel 0.016
Muscle
VMO vs. GM 0.001
VMO vs. BF 0.001
VL vs. GM 0.001
VL vs. BF 0.001
GM vs. BF 0.001
Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 64
IXUWKHU
7KHPRVWSURPLQHQWÀQGLQJZDVWKDWVTXDWWLQJWR
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)LJXUH7KLVÀQGLQJRSSRVHVWKHUHVXOWVRI 
Caterisano et al. 10ZKRUHSRUWHGWKH*0VLJQLÀFDQWO\
more active in the full squat, and the mechanical
DQDO\VLVFDUULHGRXWE\%U\DQWRQet al5 who reported
that the largest hip joint moment and relative
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RXUÀQGLQJVXEVWDQWLDWHVRWKHUUHSRUWV13 that found
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ERWWRPRI DIXOOVTXDWWRDSDUDOOHOGHSWK
7KHKLJKHU*0DFWLYLW\LQWKHSDUDOOHOVTXDWPD\
EHH[SODLQHGE\DQXPEHURI IDFWRUV([DPLQDWLRQRI 
the time-motion analysis of the full squat 1 reveals
WKDWWKHH[WHUQDOPRPHQWDUPLPSRVHGRQWKH*0
appears to attenuate once the participant descends
EH\RQGWKHSDUDOOHOSRVLWLRQDVGRUVLÁH[LRQLV
maximised and the femur to shank angle is reduced,
bringing the acetabulofemoral joint closer to the
vertical plane of the bar 17KLVREVHUYDWLRQVXEPLWV
WKDWOHVVWRUTXHDQGWKXVOHVV(0*DFWLYLW\RI WKH
*0LVUHTXLUHGWRRYHUFRPHLQHUWLDDJDLQVWWKHOLIWHG
load compared to the parallel squat 22+RZHYHUQR
published kinematic data exists to substantiate this
FODLP$OVRLWPD\EHVSHFXODWHGWKDWLQFUHDVHG
relative muscular effort of the knee extensor with
greater squat depth 5DQGKLJKHU902(0*DFWLYLW\
)LJXUHVPD\UHGXFHWKHPXVFXODUGHPDQGRQ
WKH*0$QRWKHUIDFWRUWKDWPD\H[SODLQZK\*0
muscle activity did not increase in the full squat is the
role of soft tissue in supporting the load at the end
RI UDQJHRI PRWLRQ,WKDVEHHQVXJJ HVWHGWKDWDQ
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conducive to muscle force production 3 and
suggestive that perhaps less activation is required to
generate tension in the partial squat 22,WLVXQFOHDU
ZKHWKHUWKHDQJOHRI KLSÁH[LRQSHDNVDWWKHSDUDOOHO
depth and remains constant, whereby muscle length
and involvement would not necessarily change as the
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IRUWKHKLJKHU*0DFWLYLW\DWSDUDOOHOGHSWK
Table 2: Statistically signicant results of the three-way Anova
and Sidak post-hoc statistical tests (Mean EMG).
Variables F
ratio df pȘp2power
Squat type 3.9 2,156 0.021 0.05 0.70
Squat phase 205.6 1,156 0.001 0.57 1.00
Muscle 166.6 3,156 0.001 0.76 1.00
Squat type * Phase 4.9 2,156 0.009 0.06 0.80
Squat phase * Muscle 13.3 3,156 0.001 0.02 1.00
Sidak post-hocs
Squat type
Partial vs. parallel 0.07*
Muscle
VMO vs. GM 0.001
VMO vs. BF 0.001
VL vs. GM 0.001
VL vs. BF 0.001
GM vs. BF 0.001
* Approaching significance
Table 3: Statistically signicant results of the three-way Anova
and Sidak post-hoc statistical tests (iEMG).
Variables F
ratio df pȘp2power
Squat type 22.1 2,156 0.001 0.22 1.00
Squat phase 165.7 1,156 0.001 0.51 1.00
Muscle 112.8 3,156 0.001 0.68 1.00
Squat type * Phase 4.3 2,156 0.015 0.05 0.74
Squat phase * Muscle 9.5 3,156 0.001 0.15 1.00
Sidak post-hocs
Squat type
Partial vs. parallel 0.001
Partial vs. full 0.001
Muscle
VMO vs. GM 0.001
VMO vs. BF 0.001
VL vs. GM 0.001
VL vs. BF 0.001
GM vs. BF 0.001
Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 65
7KH%)ZDVPRUHDFWLYHDWSDUDOOHO0HDQ(0* 
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during the concentric phase, similarly to the vasti and
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differences were found between parallel and full
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the eccentric phase, both knee extensors were active
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reported previously 18RI DQG
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lower than those reported by the other studies, as is
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compared to other work 13, which is unexpected as
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Nonetheless, while the back squat provides an
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risk from squatting below parallel have since been
dispelled and such forces are no longer considered
an issue when concerning a healthy knee joint 22,32
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thus prompt a disproportionate development of
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must be cognizant of the necessity to incorporate
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imbalance in muscle activation and reduce the
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is associated with risk factors such as hamstrings
inhibition during antagonistic co-activation, reduced
knee joint stability and resulting anterior tibial
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susceptibility to injury 337KLVLVSDUWLFXODUO\
pertinent in female athletes in whom inherent
quadriceps to hamstrings dominance is apparent 34,
and highly applicable to athletic performance where
lateral cutting manoeuvres and landing forces
demand effective joint stability 35
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2 and high statistical power were achieved
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care was taken to ensure electrode placement sites
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days separate from the experimental trials which may
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To this end, it would be expedient to analyse trunk
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CONCLUSIONS
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squat provides an effective training stimulus for
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Thus, supplementary strength training exercises may
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full squats than in the partial squat during the
concentric phase, and in the eccentric phase with
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vasti in the parallel compared to the partial squat is
likely due to mechanical disadvantage and greater
neural drive to the quadriceps at intermediate and
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Volume 5, Issue 3, December 2016 | JOURNAL OF FITNESS RESEARCH 66
activity in parallel squats compared to full squats
which may be explained by a number of factors
related to external moment arm, relative muscular
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ACKNOWLEDGEMENTS
The authors would like to acknowledge the
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barbell load on relative muscular effort in
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concentric and eccentric squat force relationships
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Journal of Strength and Conditioning Research.
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electromyograms obtained from healthy
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... Modifications of the squat, including changes in depth, stance width, and barbell placement, have been suggested to promote alternate muscle activation and muscular adaptations [30,31]. Changing squat depth is a simple modification to the traditional back squat that has been the subject of many research studies [30][31][32][33]. ...
... Modifications of the squat, including changes in depth, stance width, and barbell placement, have been suggested to promote alternate muscle activation and muscular adaptations [30,31]. Changing squat depth is a simple modification to the traditional back squat that has been the subject of many research studies [30][31][32][33]. A squat to 20 deg knee flexion was found to elicit lower vastus medialis oblique (VM) and vastus lateralis (VL) cocontraction than a squat to 50 deg or 80 deg [33]. ...
... A squat to 20 deg knee flexion was found to elicit lower vastus medialis oblique (VM) and vastus lateralis (VL) cocontraction than a squat to 50 deg or 80 deg [33]. Similarly, parallel and deep squats were found to provoke higher average activation and integrated electromyography of the VM and VL when compared to partial squats [31]. The effect of depth on posterior chain activation, hip extensor to knee extensor co-contraction (HE:Q), and sex, however, was unexamined. ...
Article
The squat is an essential exercise for strengthening lower body musculature. Although squats are frequently employed to improve lower extremity strength and neuromuscular control, differences between sexes and slight modifications, such as squat depth, can dramatically alter muscle recruitment and thus the foci of the exercise. The purpose of this study was to assess the effect of sex and squat depth on lower extremity coactivation and kinematics. Twenty recreationally active (women=10) participants were recruited. The first visit consisted of one repetition maximum testing. For the second visit, muscle activation was recorded of the gluteus maximus, semitendinosus, biceps femoris, vastus medialis, vastus lateralis, rectus femoris, and gastrocnemius. Reflective markers were placed on the lower body for 3D motion capture. Participants performed a series of squats to 90° knee flexion and 120° knee flexion. Benjamin-Hochberg procedure was employed and the alpha level was set at .05. Knee flexion (p<.001), adduction (p<.001), and external rotation (p=.008) were reduced during 90° compared to deep squats. Hip flexion, abduction, and external rotation were greater in deep squats (p<.001). Males had greater hip extensor to quad (HE:Q) co-contraction in 90° compared to deep squats (p=.007); females produced greater posterior chain activation in deep squats (p=.001) on ascent. When comparing sexes, males displayed greater HE:Q in the 90° squat during ascent (p=.013). The addition of deep squats into a preventative training program could be beneficial in reducing deficits prevalent in females and decrease injury incidence.
... A major part of the studies found the main activity on the vastus lateralis, vastus medialis, and rectus femoris, in this order (Aspe & Swinton, 2014;Contreras et al., 2015Contreras et al., , 2016da Silva et al., 2017;Delgado et al., 2019;Ebben et al., 2009;Eliassen et al., 2018;Gorsuch et al., 2013;Hammond et al., 2016;Iversen et al., 2017;Korak et al., 2018;Robbins, 2011;Schwanbeck et al., 2009;Wu et al., 2019;Yavuz et al., 2015). Only one study found major activation on the biceps femoris than on each of these three aforementioned muscles . ...
... High-bar squat (P) observed a slightly higher activation on the gluteus in the full-ROM squats in comparison to the other two modalities, other authors found no differences, or even higher gluteus activity values in the parallel squats (da Silva et al., 2017;Hammond et al., 2016). The effect of this technical modification was only assessed in the high-bar squat. ...
... As can be seen in the results, there are technical and electromyographical variations when the position of the bar changes (Pham et al., 2020). For instance, the load in the performance of a high-bar squat, a front squat, or an overhead squat, is shared between the knees and the hips (Comfort et al., 2018), with the main focus on the vastus lateralis and medialis as knee extensors (Aspe & Swinton, 2014;Contreras et al., 2015Contreras et al., , 2016Delgado et al., 2019;Ebben et al., 2009;Hammond et al., 2016). In turn, a higher hip involvement has been reported in the low-bar squat (Glassbrook et al., 2017(Glassbrook et al., , 2019Wretenberg et al., 1996). ...
Article
Full-text available
The squat is one of the most commonly used resistance exercises for performance and health due to its biomechanical and neuromuscular similarities to a wide range of athletic and everyday activities. There is a large number of squat variations (based on the descent depth, width of the stance, bar placement) with significant biomechanical and neuromuscular differences between them. The aim of this study was to systematically review the scientific literature to gather data on the muscular activation of the lower limb during different variants of the squat exercise. High-bar squat (full range of motion, to parallel and partial range of motion), low-bar squat, front squat, overhead squat and guided squat on Smith machine were included in the analysis. 30 articles met the inclusion criteria and were reviewed. Quality of the included studies was analysed with the PEDro scale. Main findings were that in the squat exercise activation of the knee-extensors is predominant. However, different activation patterns were observed with different distances between the feet, different depths, hips rotation or flexion, intensities. For instance, low-bar squat involves a greater hip hinge and thus, provokes major activation on the hip-extensors than other squat variations. It is worth highlighting that similar activation patterns were observed between the front squat and the high-bar squat. The variation with least activation was the guided squat. The evidence presented in this study may help the strength and conditioning professionals and practitioners with the exercise selection depending on the muscular targets and the individual characteristics of the athlete. Keywords: Electromyographic activity; Resistance exercise; Quadriceps; Gluteus; Hamstrings; Calves.
... Earth-based simulations of partial gravity environments can provide a platform to be employed for determining the degree of muscle activity (electromyography -EMG) relative to the maximum that can be achieved, in addition to relative muscle comparisons. [8] The latest and least functionally limited hypogravity analog to emerge is the lower body positive pressure (LBPP) box treadmill. [9] Enclosing volunteers' lower limbs inside an air-tight inflatable chamber, attached at the waist, the LBPP box utilizes pressure differentials to generate lift and alter the weight of the participant as desired. ...
... [29] When acquiring the MVIC for the GM, the subjects assumed a prone quadruped position, maximally extending the right hip with the knee flexed to 90°. [8,27,30] ...
Article
Context: With a long duration return mission to Mars on the horizon, we must learn as much about the environment and its influence on the musculoskeletal system as possible to develop countermeasures and mitigate deleterious health effects and maladaptation. Aims: To determine the influence of simulated Mars gravity on the activity of four locomotor muscles while walking, in comparison to 1 G, using lower body positive pressure (LBPP). Material and methods: A total of 14 male subjects (mean age: 20.6 ± 2.4 years) performed bouts of walking in both simulated Mars gravity (0.38 G) and Earth gravity (1 G) using an LBPP device. The dependent variables were the muscle activity evoked in the tibialis anterior, vastus lateralis, gluteus maximus and lateral portion of the gastrocnemius, measured using electromyography and expressed as percentages of maximum voluntary isometric contractions, and heart rate (HR). For statistical analysis, a paired t-test was performed. Statistical significance was defined as P < 0.05. Results: No significant differences in muscle activity were found across conditions for any of the investigated muscles. A significant mean difference in the HR was identified between Earth (105.15 ± 8.1 bpm) and Mars (98.15 ± 10.44 bpm) conditions (P = 0.027), wherein the HR was lower during the Mars trial. Conclusions: The Mars environment may not result in any deteriorative implications for the musculoskeletal system. However, if future research should report that stride frequency and thus activation frequency is decreased in the simulated Mars gravity, negative implications may be posed for muscle retention and reconditioning efforts on the Red Planet.
... Future studies should consider tri-planar full-body motion to further elucidate the differences between failed and successful back squat attempts. Other studies have found foot placement and squat depth influence weight lifted, vertical velocity, and joint moments [6,8,36,37]. Thus, future work in this area may also consider allowing athletes to perform squats with their own form. ...
Article
Previous literature suggests the sticking region, the transition period between an early peak concentric velocity to a local minimum, in barbell movements may be the reason for failing repeated submaximal and maximal squats. This study determined the effects of load on lower extremity biomechanics during back squats. Twenty participants performed the NSCA's one-repetition maximum (1RM) testing protocol, testing to supramaximum loads (failure). After completing the protocol and a 10-minute rest, 80% 1RM squats were performed. Statistical parametric mapping was used to determine vertical velocity, acceleration, ankle, knee, and hip sagittal and frontal plane biomechanics differences between 1RM, submaximum, and supramaximum squats (105% 1RM). Vertical acceleration was a better discriminative measure than velocity, exibiting differences across all conditions. Supramaximum squats emphasized knee moments, whereas 1RM emphasized hip moments during acceleration. Submaximum squats had reduced hip and knee moments compared to supramaximum squats, but similar knee moments to 1RM squats. Across all conditions, knee loads mirrored accelerations and a prominent knee (acceleration) to hip (sticking) transition existed. These results indicate that 1) submaximum squats performed at increased velocities can provide similar moments at the ankle and knee, but not hip, as maximal loads and 2) significant emphasis on hip strength is necessary for heavy back squats.
Article
Full-text available
Electromyography (EMG) is widely used in controlling the signal in manipulating the robot assisted rehabilitation. In order to manipulate a more accurate robot assisted, the feature extraction and selection were equally important. This study evaluated the performance of time domain (TD) and frequency domain (FD) features in discriminating EMG signal. To investigate the features performance, the linear discriminate analysis (LDA) was introduced. The present study showed that the FD features achieved the highest accuracy of 91.34% in LDA. The results were verified by LDA classifier and FD features showed best classification performance in EMG signal classification application. Index Terms-Electromyography (EMG), time domain (TD), frequency domain (FD) and linear discriminant analysis (LDA)
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