Alles wat je wou weten over de squat . . .

Author
Wreckless
Super Heavy Weight
2006/11/12 10:24:05 (permalink)
0

Alles wat je wou weten over de squat . . .

maar nooit durfde te vragen.
 
The Importance of Knowing Squat
Frederick C. Hatfield, Ph.D., MSS
http://www.dolfzine.com/page253.htm

I Know Squat
Part 2: Proper Squatting Techniques
http://www.dolfzine.com/page285.htm

------------------
Purepowermag
Don't know Squat
Krieger, Wagman, Wagner

-------------------
Front Squat Techniques
Dr. Mel Siff
http://staff.washington.edu/griffin/front_squat.html

----------------------
Those Squats and Myths:
by Dr. Mel Siff
http://nbaf.com/nbaf/feb7pgi.htm

---------------------
Biomechanics Research Squat, Bench, Deadlift
Dave Sandler
http://www.strengthpro.com/ca/swis02.pdf

------------------------
List of Exercises associated with upper leg/hip
Robert Newton, Ph.D.
http://www.bsu.edu/webapps/strengthlab/exregion.asp?id=8

----------------------
Squat quotes from the experts
http://www.strengthcats.com/SquatQuote.PDF

Research:
Med Sci Sports Exerc 2001 Jun;33(6):984-98

A three-dimensional biomechanical analysis of the squat during
varying stance widths

Escamilla RF, Fleisig GS, Lowry TM, Barrentine SW, Andrews JR

PURPOSE: The purpose of this study was to quantify biomechanical
parameters employing two-dimensional (2-D) and three-dimensional (3-
D) analyses while performing the squat with varying stance widths.
METHODS: Two 60-Hz cameras recorded 39 lifters during a national
powerlifting championship. Stance width was normalized by shoulder
width (SW), and three stance groups were defined: 1) narrow stance
squat (NS), 107 ± 10% SW; 2) medium stance squat (MS), 142 ± 12% SW;
and 3) wide stance squat (WS), 169 ± 12% SW.

RESULTS: Most biomechanical differences among the three stance groups
and between 2-D and 3-D analyses occurred between the NS and WS.
Compared with the NS at 45 degrees and 90 degrees knee flexion angle
(KF), the hips flexed 6-11 degrees more and the thighs were 7-12
degrees more horizontal during the MS and WS. Compared with the NS at
90 degrees and maximum KF, the shanks were 5-9 degrees more vertical
and the feet were turned out 6 degrees more during the WS. No
significant differences occurred in trunk positions.

Hip and thigh angles were 3-13 degrees less in 2-D compared with 3-D
analyses. Ankle plantar flexor (10-51 N.m), knee extensor (359-573
N.m), and hip extensor (275-577 N.m) net muscle moments were
generated for the NS, whereas ankle dorsiflexor (34-284 N.m), knee
extensor (447-756 N.m), and hip extensor (382-628 N.m) net muscle
moments were generated for the MS and WS. Significant differences in
ankle and knee moment arms between 2-D and 3-D analyses were 7-9 cm
during the NS, 12-14 cm during the MS, and 16-18 cm during the WS.

CONCLUSIONS: Ankle plantar flexor net muscle moments were generated
during the NS, ankle dorsiflexor net muscle moments were produced
during the MS and WS, and knee and hip moments were greater during
the WS compared with the NS. A 3-D biomechanical analysis of the
squat is more accurate than a 2-D biomechanical analysis, especially
during the WS.

----------------

Res Q Exerc Sport 1989 Sep; 60(3):201-8

A preliminary comparison of front and back squat exercises

Russell PJ, Phillips SJ

The purpose of this study was to compare the knee extensor demands
and low back injury risks of the front and back squat exercises.
Highly strength-trained college-aged males (n = 8), who performed
each type of squat (Load = 75% of front squat one repetition
maximum), were filmed (50 fps) from the sagittal view. The body was
modeled as a five link system. Film data were digitized and reduced
through Newtonian mechanics to obtain joint forces and muscle
moments. Mean and individual subject data results were examined.

The maximum knee extensor moment comparison indicated similar knee
extensor demands, so either squat exercise could be used to develop
knee extensor strength. Both exercises had similar low back injury
risks for four subjects, but sizable maximum trunk extensor moment
and maximum lumbar compressive and shear force differences existed
between the squat types for the other subjects.

The latter data revealed that with the influence of trunk inclination
either exercise had the greatest low back injury risk (i.e., with
greater trunk inclination: greater trunk extensor demands and lumbar
shear forces, but smaller lumbar compressive forces). For these four
subjects low back injury risk was influenced more by trunk
inclination than squat exercise type.

----------------------

J Biomed Eng 1988 Jul;10(4):312-8

Potential of lumbodorsal fascia forces to generate back extension
moments during squat lifts

McGill SM & Norman RW

The lumbodorsal fascia (LDF) has been implicated in numerous
biomechanical interpretations of low back mechanics as a tissue that
provides support to the lumbar spine during demanding load bearing.
One hypothesis is that oblique abdominal muscle forces contribute to
trunk extensor moment by transforming lateral abdominal tension into
longitudinal tension via the LDF. However, a review of the anatomical
literature supports the hypothesis that extensor forces in the LDF
result from tension within the latissimus dorsi muscle. The purpose
of our work was to evaluate the potential of the LDF to generate
trunk extensor moment using two mathematical models: one that
activated the LDF with the abdominals and another that activated the
LDF with the latissimus dorsi. Efforts were made to represent the
anatomy as accurately as possible.

The results from three subjects performing six squat lifts each,
suggested that the potential of the LDF to contribute significant
extensor moment has been overestimated. In fact, the issue of whether
the LDF is activated by the abdominals or the latissimus dorsi is
irrelevant because neither strategy appeared able to generate sizable
extensor moments in the type of lift studied.

-------------------

Eur J Appl Physiol 2001 Mar; 84(3):227-32

Force/velocity and power/velocity relationships in squat exercise

Rahmani A, Viale F, Dalleau G, Lacour JR

The purpose of this study was to describe the force/velocity and
power/velocity relationships obtained during squat exercise. The
maximal force (F0) was extrapolated from the force/velocity
relationship and compared to the isometric force directly measured
with the aid of a force platform placed under the subject's feet.
Fifteen international downhill skiers [mean (SD) age 22.4 (2.6)
years, height 178 (6.34) cm and body mass 81.3 (7.70) kg] performed
maximal dynamic and isometric squat exercises on a guided barbell.
The dynamic squats were performed with masses ranging from 60 to 180
kg, which were placed on the shoulders.

The force produced during the squat exercise was linearly related to
the velocity in each subject (r2 = 0.83-0.98). The extrapolated F0
was 23% higher than the measured isometric force, and the two
measurements were not correlated. This may be attributed to the
position of the subject, since the isometric force was obtained at a
constant angle (90 degrees of knee flexion), whereas the dynamic
forces were measured through a range of movements (from 90 degrees to
180 degrees).

The power/velocity relationship was parabolic in shape for each
subject (r2 = 0.94-0.99). However, the curve obtained exhibited only
an ascending part. The highest power was produced against the
lightest load (i.e., 60 kg). The maximal power (Wmax) and optimal
velocity were never reached. The failure to observe the descending
part of the power/velocity curve may be attributed to the upper
limitation of the velocities studied. Nevertheless, the extrapolation
of Wmax from the power/velocity equation showed that it would be
reached for a load close to body mass, or even under unloaded
conditions.

-------------------

Med Sci Sports Exerc 1986 Aug;18(4):469-78

Biomechanics of the squat exercise using a modified center of mass bar

Lander JE, Bates BT, Devita P

The purpose of the study was to investigate the effects of load
height on selected performance characteristics of a squat exercise. A
lower center of mass bar was designed that allowed the integrity of
the squat exercise to be maintained while possibly reducing the
chances of injury. Five trials were performed with the center of mass
of the bar was set at shoulder height (C1) and lowered 18% (C2) and
36% (C3) of the subject's height below the normal bar position using
the inverted "U" bar. All trials were filmed as the subjects lifted
on a force platform. A balloon catheter was inserted into the
subject's recta to monitor intra-abdominal pressure (IAP).

High correlations were found between IAP, joint moment, and force
data. Many of the critical parameters occurred just after the lowest
squat position. Significant differences in trunk angle excursion and
trunk angular velocity indicated a greater ease of hip extension for
the center of mass bar conditions. No differences were observed
between conditions for thigh and knee angles and joint moments
indicating kinematic similarity for the lower extremity.

IAP was always least for C2 and C3, while compression, shear, and
back muscle forces did not differ. It was estimated that the greater
IAP was responsible for relieving back muscle forces and compression
by up to 15 and 21%, respectively, and increased stress with the
weight at shoulder height stimulated a response for greater IAP to
help alleviate the stresses on the spine.

----------------------

Med Sci Sports Exerc 1990 Feb;22(1):117-26

The effectiveness of weight-belts during the squat exercise

Lander JE, Simonton RL, Giacobbe JK

The purpose of this study was to examine the effectiveness of weight-
belts during the performance of the parallel squat exercise. Six
subjects were filmed (40 fps) as they performed three trials at each
of three belt conditions (NB, none; LB, light; HB, heavy) in random
order and three load conditions (70, 80, 90% 1RM (one repetition
maximum] in increasing order. The parameters examined were collected
and interfaced to a computer via an analog-to-digital (A/D)
converter: ground reaction forces, intra-abdominal pressure (IAP),
and EMG for the rectus abdominus (RA), external oblique (EO), and
erector spinae (ES) muscles. Most differences were observed during
the 90% 1RM condition, and only they are presented in this paper.
Maximum IAP values were always greater (P less than 0.05) for the
weight-belt conditions (LB, 29.2; HB, 29.1 greater th an NB, 26,8
kPa). Similar results were observed for the mean IAP. The integrated
EMG (iEMG) activity of the muscles and adjusted mean values for back
compressive force and back muscle force followed a similar but
opposite pattern, with NB being the greatest. ES mEMG/(L5/S1) values
for HB (18.1%) were the least, followed by LB (20.01%) and NB
(22.3%). Few differences were observed between belt types.

These data suggest that a weight-belt can aid in supporting the trunk
by increasing IAP.

-------------------

Med Sci Sports Exerc 1985 Oct; 17(5):613-20

Lumbar spine loading during half-squat exercises

Cappozzo A, Felici F, Figura F, Gazzani F

Evaluation of the compressive load acting on the lumbar spine (L3-L4)
during half-squat exercises executed with a barbell resting on the
subject's shoulders was undertaken. The kinematics of the upper body
segments of two male and two female subjects as well as the barbell
were described using data obtained by means of an optoelectronic
system (CoSTEL). L3-L4 compressive load was calculated using a model
of the anatomy of the trunk musculoskeletal system. Filtered surface
electromyographic trunk flexor recordings from the obliquus externus
and rectus abdominis and trunk extensor erectores spinae muscles as
well as measurement of the ground reaction forces were also carried
out for predicted result validation.

During half-squat exercises with barbell loads in the range 0.8 to
1.6 times body weight the compressive loads on the L3-L4 segment vary
between 6 and 10 times body weight. Erectores spinae contraction
force was predicted to be between 30 and 50% of the relevant maximal
isometric force.

The magnitude of trunk flexion was found to be the variable which
influenced most spinal compression load.

-----------------

Med Sci Sports Exerc 1989 Oct; 21(5):613-8

Effect of load, cadence, and fatigue on tibio-femoral joint force
during a half squat

Hattin HC, Pierrynowski MR, Ball KA

Ten male university student volunteers were selected to investigate
the 3D articular force at the tibio-femoral joint during a half squat
exercise, as affected by cadence, different barbell loads, and
fatigue. Each subject was required to perform a half squat exercise
with a barbell weight centered across the shoulders at two different
cadences (1 and 2 s intervals) and three different loads (15, 22 and
30% of the one repetition maximum). Fifty repetitions at each
experimental condition were recorded with an active optoelectronic
kinematic data capture system (WATSMART) and a force plate (Kistler).
Processing the data involved a photogrammetric technique to obtain
subject tailored anthropometric data. The findings of this study were:

1) the maximal antero-posterior shear and compressive force
consistently occurred at the lowest position of the weight, and the
forces were very symmetrically disposed on either side of this
halfway point;

2) the medio-lateral shear forces were small over the squat cycle
with few peaks and troughs;

3) cadence increased the antero-posterior shear (50%) and the
compressive forces (28%);

4) as a subject fatigues, load had a significant effect on the
antero-posterior shear force;

5) fatigue increased all articular force components but it did not
manifest itself until about halfway through the 50 repetitions of the
exercise;

6) the antero-posterior shear force was most affected by fatigue;

7) cadence had a significant effect on fatigue for the medio-lateral
shear and compressive forces.

-----------------------
***Note comments from Dr Siff

Med Sci Sports Exerc 1997 Apr; 29(4):532-9

EMG analysis of lower extremity muscle recruitment patterns during an
unloaded squat.

Isear JA Jr, Erickson JC, Worrell TW.

During an unloaded squat, hamstring and quadriceps co-contraction has
been documented and explained via a co-contraction hypothesis. This
hypothesis suggests that the hamstrings provide a stabilizing force
at the knee by producing a posteriorly-directed force on the tibia to
counteract the anterior tibial force imparted by the quadriceps.
Research support for this hypothesis, however, is equivocal.

Therefore, the purposes of this study were 1) to determine muscle
recruitment patterns of the gluteus maximus, hamstrings, quadriceps,
and gastrocnemius during an unloaded squat exercise via EMG and 2) to
describe the amount of hamstring-quadriceps co-contraction during an
unloaded squat.

Surface electrodes were used to monitor the EMG activity of six
muscles of 41 healthy subjects during an unloaded squat. Each subject
performed three 4-s maximal voluntary isometric contractions (MVIC)
for each of the six muscles. Electrogoniometers were applied to the
knee and hip to monitor joint angles, and each subject performed
three series of four complete squats in cadence with a metronome (50
beats.min-1). Each squat consisted of a 1.2-s eccentric, hold, and
concentric phase. A two-way repeated measures ANOVA (6 muscles x 7
arcs) was used to compare normalized EMG (percent MVIC) values during
each arc of motion (0-30 degrees, 30-60 degrees, 60-90 degrees, hold,
90-60 degrees, 60-30 degrees, 30-0 degrees) of the squat. Tukey post-
hoc analyses were used to quantify and interpret the significant two-
way interactions.

Results revealed minimal hamstring activity (4-12% MVIC) as compared
with quadriceps activity (VMO: 22-68%, VL: 21-63% of MVIC) during an
unloaded squat in healthy subjects. This low level of hamstring EMG
activity was interpreted to reflect the low demand placed on the
hamstring muscles to counter anterior shear forces acting at the
proximal tibia.

---------

*** The following study showed that if you wish to exercise the
glutes, then a full depth squat is highly recommended.

J Strength Cond Res 2002 Aug; 16(3): 428-32

The effect of back squat depth on the EMG activity of 4 superficial
hip and thigh muscles.

Caterisano A, Moss RF, Pellinger TK, Woodruff K, Lewis VC, Booth W,
Khadra T.

The purpose of this study was to measure the relative contributions
of 4 hip and thigh muscles while performing squats at 3 depths. Ten
experienced lifters performed randomized trials of squats at partial,
parallel, and full depths, using 100-125% of body weight as
resistance. Electromyographic (EMG) surface electrodes were placed on
the vastus medialis (VMO), the vastus lateralis, (VL), the biceps
femoris (BF), and the gluteus maximus (GM). EMG data were quantified
by integration and expressed as a percentage of the total electrical
activity of the 4 muscles.

Analysis of variance (ANOVA) and Tukey post hoc tests indicated a
significant difference in the relative contribution of the GM during
the concentric phases among the partial- (16.9%), parallel- (28.0%),
and full-depth (35.4%) squats.

There were no significant differences between the relative
contributions of the BF, the VMO, and the VL at different squatting
depths during this phase. The results suggest that the GM, rather
than the BF, the VMO, or the VL, becomes more active in concentric
contraction as squat depth increases.

----------------

*** This study concluded that that stance width does not cause
significant isolation within the quadriceps but does influence muscle
activity on the medial thigh and buttocks.

Med Sci Sports Exerc 1999 Mar;31(3):428-36

Stance width and bar load effects on leg muscle activity during the
parallel squat.

McCaw ST, Melrose DR.

PURPOSE: Altering foot stance is often prescribed as a method of
isolating muscles during the parallel squat. The purpose of this
study was to compare activity in six muscles crossing the hip and/or
knee joints when the parallel squat is performed with different
stances and bar loads.

METHODS: Nine male lifters served as subjects. Within 7 d of
determining IRM on the squat with shoulder width stance, surface EMG
data were collected (800 Hz) from the rectus femoris, vastus
medialis, vastus lateralis, adductor longus, gluteus maximus, and
biceps femoris while subjects completed five nonconsecutive reps of
the squat using shoulder width, narrow (75% shoulder width), and wide
(140% shoulder width) stances with low and high loads (60% and 75%
1RM, respectively). Rep time was controlled. A goniometer on the
right knee was used to identify descent and ascent phases. Integrated
EMG values were calculated for each muscle during phases of each rep,
and the 5-rep means for each subject were used in a repeated measures
ANOVA (phase x load x stance, alpha = 0.05).

RESULTS: For rectus femoris, vastus medialis, and vastus lateralis,
only the load effect was significant. Adductor longus exhibited a
stance by phase interaction and a load effect. Gluteus maximus
exhibited a load by stance interaction and a phase effect. Biceps
femoris activity was highest during the ascent phase.

CONCLUSION: The results suggest that stance width does not cause
isolation within the quadriceps but does influence muscle activity on
the medial thigh and buttocks.

-----------------

*** This study confirmed that there are significant differences in
muscle recruitment patterns between the trunk extensor and hip
extensor strategies of squatting throughout the range of movement.
Unfortunately many personal trainers and fitness "authorities" are
sufficiently aware of these differences.

Spine 1994 Mar 15;19(6):687-95

Electromyographic activity of selected trunk and hip muscles during a
squat lift. Effect of varying the lumbar posture.

Vakos JP, Nitz AJ, Threlkeld AJ, Shapiro R, Horn T.

Electromyographic (EMG) activity of selected hip and trunk muscles
was recorded during a squat lift, and the effects of two different
lumbar spine postures were examined. Seven muscles were analyzed:
rectus abdominis (RA), abdominal obliques (AO), erector spinae (ES),
latissimus dorsi (LD), gluteus maximus (GM), biceps femoris (BF), and
semitendinosus (ST). The muscles were chosen for their attachments to
the thoracolumbar fascia and their potential to act on the trunk,
pelvis, and hips. Seventeen healthy male subjects participated in the
study. Each subject did three squat lifts with a 157-N crate, with
the spine in both a lordotic and kyphotic posture. The lift was
divided into four equal periods. EMG activity of each muscle was
quantified for each period and normalized to the peak amplitude of a
maximal voluntary isometric contraction (MVIC). A two-way analysis of
variance (ANOVA) for repeated measures was used to analyze the
effects of posture on the amplitude and timing of EMG activity during
the lift.

Two patterns of EMG activity were seen: a trunk muscle pattern (RA,
AO, ES, and LD) and a hip extensor pattern (GM, BF, ST).

1. In the trunk muscle pattern (TP), EMG activity was greatest (in
RA, AO, ES, and LD) in the first quarter and decreased as the lift
progressed.

2. In the hip extensor pattern (HP), EMG activity was least (in GM,
BF, ST) in the first quarter, increased in the second and third
quarters, and decreased in the final phase of the lift.

Differences were seen among subjects and in the timing of the muscle
activity in all muscles.

----------------

*** This study showed that there are major differences in muscle
recruitment and joint torque between Weightlifting and Powerlifting
squats. In particular, Weightlifters distribute the load more
equally between hip and knee, whereas Powerlifters put relatively
more load on the hip joint. The thigh muscular activity was found to
be slightly higher for powerlifters. Note that Sumo style squats
were not examined in this study, but it would probably have been
found that this places even greater load on the hips as compared with
the knees.

Med Sci Sports Exerc 1996 Feb;28(2):218-24

High- and low-bar squatting techniques during weight-training.

Wretenberg P, Feng Y, Arborelius UP.

Eight Swedish national class weightlifters performed "high-bar"
squats and six national class powerlifters performed "low-bar"
squats, with a barbell weight of 65% of their 1 RM, and to parallel-
and a deep-squatting depth. Ground reaction forces were measured with
a Kistler piezo-electric force platform and motion was analyzed from
a video record of the squats. A computer program based on free-body
mechanics was designed to calculate moments of force about the hip
and knee joints. EMG from vastus lateralis, rectus femoris, and
biceps femoris was recorded and normalized. The peak moments of force
were flexing both for the hip and the knee.

The mean peak moments of force at the hip were for the weightlifters
230 Nm (deep) and 216 Nm (parallel), and for the powerlifters 324 Nm
(deep), and 309 Nm (parallel). At the knee the mean peak moments for
the weightlifters were 191 Nm (deep) and 131 Nm (parallel), and for
the powerlifters 139 Nm (deep) and 92 Nm (parallel). The
weightlifters had the load more equally distributed between hip and
knee, whereas the powerlifters put relatively more load on the hip
joint. The thigh muscular activity was slightly higher for the
powerlifters.

--------------

***The following study concluded that the use of a weight belt during
squats may affect the path of the barbell and speed of the lift
without altering electric activity of the muscles. This suggests that
the use of a weight belt may increase explosive power by increasing
the speed of the movement without compromising the joint range of
motion or overall lifting technique. So much for all the claims about
belts being of no value in lifting.

J Strength Cond Res 2001 May;15(2):235-40

The effects of a weight belt on trunk and leg muscle activity and
joint
kinematics during the squat exercise.

Zink AJ, Whiting WC, Vincent WJ, McLaine AJ.

Fourteen healthy men participated in a study designed to examine the
effects of weight-belt use on trunk- and leg-muscle myoelectric
activity (EMG) and joint kinematics during the squat exercise.

Each subject performed the parallel back squat exercise at a self-
selected speed according to his own technique with 90% of his IRM
both without a weight belt (NWB) and with a weight belt (WB).
Myoelectric activity of the right vastus lateralis, biceps femoris,
adductor magnus, gluteus maximus, and erector spinae was recorded
using surface electrodes. Subjects were videotaped from a sagittal
plane view while standing on a force plate. WB trials were completed
significantly faster than NWB trials over the entire movement and in
both the downward phase (DP) and upward phase (UP).

No significant differences in EMG were detected between conditions
for any of the muscle groups or for any joint angular kinematic
variables during either phase of the lift. The total distance
traveled by the barbell both anteriorly and vertically was
significantly greater (p 0.01) in the WB condition than the NWB
condition. The velocity of the barbell was significantly greater
both vertically and horizontally during both the DP and UP in the WB
condition as compared with the NWB condition.

These data suggest that the use of a weight belt during the squat
exercise may affect the path of the barbell and speed of the lift
without altering myoelectric activity. This suggests that the use of
a weight belt may improve a lifter's explosive power by increasing
the speed of the movement without compromising the joint range of
motion or overall lifting technique.

overgenomen van supertraining
#1

2 Replies Related Threads

    flupn
    Super Heavy Weight
    RE: Alles wat je wou weten over de squat . . . 2006/11/12 18:15:57 (permalink)
    0
    * Powerlifting Squats (wide, intermediate or narrow stance)
    * Olympic Squats (also called "High Bar Squats" or "Bodybuilding Squats"knipoog
    * Safety Squats
    * Twisting Squats
    * Lunge Squats
    * Side Lunge Squats
    * Partial Squats
    * Box Squats
    * Jefferson Squats
    * Hack Squats (with barbell or machine)
    * Leg Presses (angle of weight ascent ranging from 0 degrees to 90 degrees)
    * Overhead Squats (also called snatch grip squats)
    * Magic Circle Squats (also called Raider squats)
    * Sissy Squats
    * Front Squats
    * Platform Squats
    * Zane Squats
    * Platz Squats (Olympic squats done with a bent bar)
    * Bear Squats
    * Front Harness Squats
    * True Squats


    dit heb ik gevonden in het eerste artikel, maar kan er mij iemand duiding geven bij deze namen, ik heb gezocht op google maar voor de meeste vind ik geen resultaten...


    EDIT: heb net zelf het antwoord op mn vraag gevonden, maar misschien toch nuttig voor iemand:

    http://www.drsquat.com/articles/diddley.html
    #2
    ErEf
    Growing pains BFF AD
    RE: Alles wat je wou weten over de squat . . . 2006/11/12 23:52:07 (permalink)
    0
    #3
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