Re: Full Range Squats vs Half Squats

[Guest guest]

I turned up a few electromyographic studies of muscle activity

comparisons with full and half squats. I was keen to see what

differences existed between these two forms for particular muscle

groups.

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, et al.

http://tinyurl.com/23jgd2

" CONCLUSIONS: 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. "

Gluteus maximus (GM) activation was 35.4% with full squat compared to

28% for parallel squat. This is significant but perhaps not

substantial considering that for most people a full squat demands

less weight.

Significantly, no differences were seen in hamstring activation

(biceps femoris) in this study between full and parallel squats.

(Other hamstring muscles not measured, eg, ST, SM.)

In this Japanese study: AN ELECTROMYOGRAPHIC ANALYSIS OF FOUR

METHODS IN SQUAT TRAINING. Sogabe Akitoshi (Konan University, Japan),

lower leg muscle involvement was also measured (TA and GAS).

Half-squat:

AL:84.8%, VM:90.3%, VL:90.2%, RF:73.1%, BF:98.8%,

TA:78.3%, GAS:110.1%

Full-squat:

AL:65.4%, VM:106.9%, VL:100.2%, RF:166.6%,

BF:99.2%, TA:130.4%, GAS:117.1%

http://docs.ksu.edu.sa/PDF/Articles24/Article240921.pdf

Again, this study seems *not* to show advantage for hamstring (BF)

involvement in full squats, although clearly the lower leg muscles

get a hammering with the full squat. However, to reiterate, for many

squatters half squats may involve heavier weights than full squats.

Interestingly, the full squat also bakes the rectus femoris

significantly more than in the half squat, at least in this study,

which is perhaps not what we mostly hear.

I'm not an expert in interpreting studies such as these and there may

be more definitive work elsewhere. Can anyone post a validated

position that describes advantages for hamstring and glute

development with full squats over half or parallel squats?

(I understand the needs of Olympic lifters of course.)

Gympie, Austalia

>

> In a previous post some weeks back I stated that half squats or

squats

> done to a 90 degree knee bend were more stressful than full or ATG

> squats. Although I still haven't found the relevant research

> citations, I did come across this quote:

>

> ALWAYS DO FULL SQUATS

>

> Partial Squats are never good. They neglect the hips and hamstrings.

> When an athlete stops above parallel, his knees and joints are

forced

> to halt the downward MOMENTUM. But once the athlete goes below

> parallel that stress is transferred to the more powerfull groups in

> the hips, lumbars, hamstrings and adductors. Full squats keep all

> those muscle groups proportionally strong.

>

> Bill Starr

> Strength Coach

> Hopkins University

>

> September 1,1997

>

> W.G.

> Ubermensch Sports Consultancy

> San Diego, CA

>

[Guest guest]

> Again, this study seems *not* to show advantage for hamstring (BF)

> involvement in full squats, although clearly the lower leg muscles

> get a hammering with the full squat. However, to reiterate, for

many

> squatters half squats may involve heavier weights than full squats.

>

> Interestingly, the full squat also bakes the rectus femoris

> significantly more than in the half squat, at least in this study,

> which is perhaps not what we mostly hear.

>

> I'm not an expert in interpreting studies such as these and there

may

> be more definitive work elsewhere. Can anyone post a validated

> position that describes advantages for hamstring and glute

> development with full squats over half or parallel squats?

>

****

Taken from PurePowermag (Vol 6. No 2 - Don't Know Squat)

In a review of squat research, , PhD, of Duke Uni Medical

Center in Durham, North Carolina, concluded that the quad, hamstring,

and calf (gastrocnemius) activity in the squat ranged from moderate

to high through the full ROM . He and other researchers concluded

that the muscular activity increased as the knee was bent, with the

greatest activity in a full squat.

Interestingly, the vastus lateralis and medialis contribute about the

same amount of work, about 40 to 50% more than the rectus femoris. To

put this a bit more in perspective, here are some values based on

peak electromyography (EMG, a machine that records muscle activity)

data obtained from California State University in Northridge :6 8

Muscle Descent Ascent

vastus lateralis 47% 58%

biceps femoris 25% 47%

adductor magnus 37% 59%

gluteus maximus 28% 53%

erector spinae 58% 57%

While all of this is going on, particularly changes in activity in

your quads as you bend your knee, the same can't be said for the back

of your thigh, particularly the semimembranosus and semitendinosus .

Here, the greatest activity in the hamstring group was observed as

you blast out of the hole, specifically when your knee is bent at 50

to 70 degrees and the greatest activity in the biceps femoris was

found during the ascent phase.

But you need to bear in mind that the hamstrings cross two joints. Therefore,

it's difficult to determine if they contract concentrically (the positive part

of contraction) or eccentrically (the negative part of contraction). Some

scientists believe that the two motions actually cancel themselves out. Since

peak gastrocnemius activity was recorded at a knee bend of 60 to 90 degrees and

this muscle, too, spans two joints, it's difficult to determine its exact

contribution to the movement.

======================

Knee biomechanics of the dynamic squat exercise.

Med Sci Sports Exerc. 2001 Jan;33(1):127-41.

Escamilla RF.

PURPOSE: Because a strong and stable knee is paramount to an athlete's or

patient's success, an understanding of knee biomechanics while performing the

squat is helpful to therapists, trainers, sports medicine physicians,

researchers, coaches, and athletes who are interested in closed kinetic chain

exercises, knee rehabilitation, and training for sport.

The purpose of this review was to examine knee biomechanics during the dynamic

squat exercise. METHODS: Tibiofemoral shear and compressive forces,

patellofemoral compressive force, knee muscle activity, and knee stability were

reviewed and discussed relative to athletic performance, injury potential, and

rehabilitation.

RESULTS: Low to moderate posterior shear forces, restrained primarily by the

posterior cruciate ligament (PCL), were generated throughout the squat for all

knee flexion angles. Low anterior shear forces, restrained primarily by the

anterior cruciate ligament (ACL), were generated between 0 and 60 degrees knee

flexion. Patellofemoral compressive forces and tibiofemoral compressive and

shear forces progressively increased as the knees flexed and decreased as the

knees extended, reaching peak values near maximum knee flexion. Hence, training

the squat in the functional range between 0 and 50 degrees knee flexion may be

appropriate for many knee rehabilitation patients, because knee forces were

minimum in the functional range.

Quadriceps, hamstrings, and gastrocnemius activity generally increased as knee

flexion increased, which supports athletes with healthy knees performing the

parallel squat (thighs parallel to ground at maximum knee flexion) between 0 and

100 degrees knee flexion. Furthermore, it was demonstrated that the parallel

squat was not injurious to the healthy knee.

CONCLUSIONS: The squat was shown to be an effective exercise to employ during

cruciate ligament or patellofemoral rehabilitation. For athletes with healthy

knees, performing the parallel squat is recommended over the deep squat, because

injury potential to the menisci and cruciate and collateral ligaments may

increase with the deep squat. The squat does not compromise knee stability, and

can enhance stability if performed correctly. Finally, the squat can be

effective in developing hip, knee, and ankle musculature, because moderate to

high quadriceps, hamstrings, and gastrocnemius activity were produced during the

squat.

===================================

Carruthers

Wakefield, UK

[Guest guest]

Thanks for the for the research studies on squats

guys. The more the better. But people need to

remember a few things when considering the research.

First off EMG activity is only measuring the

electrical activity of the muscles, which only

approximates the actual amount of muscle fiber

contraction(a very good approximation, but it does not

shed light on the actual functionality of the muscles,

only animal research where we can cut them open and

observe it can address this). EMG activity also does

not take into account the ability of the person to

actually be strong and supple enough to actually move

through a large range of motion as is done in the full

squat. As has been stated on here before, the

majority of people in the world can't even do a full

squat without holding onto something, or falling on

their butt, or doing it with their legs ten feet apart

(a bit of an exaggeration, but you get my point)!

Research tells us that active range of motion is a

much better predictor of elite athletic prowess than

maximal strength and this needs to be considered when

we look at these kind of things.

In addition, when reading these studies it has to be

taken into account that correct form and position when

doing the squat (which is not always addressed in

these research studies) will make a big difference as

to the EMG activity that is exhibited by the various

muscles being measured. A great research study (which

might have been done already, I still need to look

into it) would be to compare the EMG activities of

people whose squat technique is extremely good and can

do full squats easily and compare it to those people

who can lift a decent amount of weight in the half

squat, but have issues doing full squats (shouldn't be

hard to find). This might give us a better idea as to

what the EMG activity should look actually like.

Chad Scheitel, MA, CSCS

Minneapolis, MN

--- carruthersjam wrote:

>

>

> > Again, this study seems *not* to show advantage

> for hamstring (BF)

> > involvement in full squats, although clearly the

> lower leg muscles

> > get a hammering with the full squat. However, to

> reiterate, for

> many

> > squatters half squats may involve heavier weights

> than full squats.

> >

> > Interestingly, the full squat also bakes the

> rectus femoris

> > significantly more than in the half squat, at

> least in this study,

> > which is perhaps not what we mostly hear.

> >

> > I'm not an expert in interpreting studies such as

> these and there

> may

> > be more definitive work elsewhere. Can anyone post

> a validated

> > position that describes advantages for hamstring

> and glute

> > development with full squats over half or parallel

> squats?

> >

>

> ****

> Taken from PurePowermag (Vol 6. No 2 - Don't Know

> Squat)

>

> In a review of squat research, , PhD, of Duke

> Uni Medical

> Center in Durham, North Carolina, concluded that the

> quad, hamstring,

> and calf (gastrocnemius) activity in the squat

> ranged from moderate

> to high through the full ROM . He and other

> researchers concluded

> that the muscular activity increased as the knee was

> bent, with the

> greatest activity in a full squat.

> Interestingly, the vastus lateralis and medialis

> contribute about the

> same amount of work, about 40 to 50% more than the

> rectus femoris. To

> put this a bit more in perspective, here are some

> values based on

> peak electromyography (EMG, a machine that records

> muscle activity)

> data obtained from California State University in

> Northridge :6 8

>

> Muscle Descent Ascent

> vastus lateralis 47% 58%

> biceps femoris 25% 47%

> adductor magnus 37% 59%

> gluteus maximus 28% 53%

> erector spinae 58% 57%

>

> While all of this is going on, particularly changes

> in activity in

> your quads as you bend your knee, the same can't be

> said for the back

> of your thigh, particularly the semimembranosus and

> semitendinosus .

> Here, the greatest activity in the hamstring group

> was observed as

> you blast out of the hole, specifically when your

> knee is bent at 50

> to 70 degrees and the greatest activity in the

> biceps femoris was

> found during the ascent phase.

>

> But you need to bear in mind that the hamstrings

> cross two joints. Therefore, it's difficult to

> determine if they contract concentrically (the

> positive part of contraction) or eccentrically (the

> negative part of contraction). Some scientists

> believe that the two motions actually cancel

> themselves out. Since peak gastrocnemius activity

> was recorded at a knee bend of 60 to 90 degrees and

> this muscle, too, spans two joints, it's difficult

> to determine its exact

> contribution to the movement.

>

> ======================

> Knee biomechanics of the dynamic squat exercise.

>

> Med Sci Sports Exerc. 2001 Jan;33(1):127-41.

> Escamilla RF.

>

> PURPOSE: Because a strong and stable knee is

> paramount to an athlete's or patient's success, an

> understanding of knee biomechanics while performing

> the squat is helpful to therapists, trainers, sports

> medicine physicians, researchers, coaches, and

> athletes who are interested in closed kinetic chain

> exercises, knee rehabilitation, and training for

> sport.

>

> The purpose of this review was to examine knee

> biomechanics during the dynamic squat exercise.

> METHODS: Tibiofemoral shear and compressive forces,

> patellofemoral compressive force, knee muscle

> activity, and knee stability were reviewed and

> discussed relative to athletic performance, injury

> potential, and rehabilitation.

>

> RESULTS: Low to moderate posterior shear forces,

> restrained primarily by the posterior cruciate

> ligament (PCL), were generated throughout the squat

> for all knee flexion angles. Low anterior shear

> forces, restrained primarily by the anterior

> cruciate ligament (ACL), were generated between 0

> and 60 degrees knee flexion. Patellofemoral

> compressive forces and tibiofemoral compressive and

> shear forces progressively increased as the knees

> flexed and decreased as the knees extended, reaching

> peak values near maximum knee flexion. Hence,

> training the squat in the functional range between 0

> and 50 degrees knee flexion may be appropriate for

> many knee rehabilitation patients, because knee

> forces were minimum in the functional range.

>

> Quadriceps, hamstrings, and gastrocnemius activity

> generally increased as knee flexion increased, which

> supports athletes with healthy knees performing the

> parallel squat (thighs parallel to ground at maximum

> knee flexion) between 0 and 100 degrees knee

> flexion. Furthermore, it was demonstrated that the

> parallel squat was not injurious to the healthy

> knee.

>

> CONCLUSIONS: The squat was shown to be an effective

> exercise to employ during cruciate ligament or

> patellofemoral rehabilitation. For athletes with

> healthy knees, performing the parallel squat is

> recommended over the deep squat, because injury

> potential to the menisci and cruciate and collateral

> ligaments may increase with the deep squat. The

> squat does not compromise knee stability, and can

> enhance stability if performed correctly. Finally,

> the squat can be effective in developing hip, knee,

> and ankle musculature, because moderate to high

> quadriceps, hamstrings, and gastrocnemius activity

> were produced during the squat.

>

> ===================================

> Carruthers

> Wakefield, UK

>

[Guest guest]

For anyone:

do you think technique used in the studies makes a difference in the muscle

activity studies? for example, a powerlifting squat, sitting way back, knees

behind toes vs. a basic ATG squat where the knee may cross the plane of the

toes.

just wondering why the science seems to be running opposite of what we'd expect

in terms of hamstring and glute activation.

Mark , MS, ATC, CSCS

Camillus, NY, USA

[Guest guest]

>

> For anyone:

> do you think technique used in the studies makes a difference in

the muscle activity studies? for example, a powerlifting squat,

sitting way back, knees behind toes vs. a basic ATG squat where the

knee may cross the plane of the toes.

> just wondering why the science seems to be running opposite of what

we'd expect in terms of hamstring and glute activation.

>

******

Here are a few relevant abstracts:

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, s 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.

======================

From Dave Sandler's presentation Biomechanics of the Lifts (2001?)

Kinematic Squat Analysis

• McLaughlin, et. al.(1977)

– all lifters showed a " sticking point "

– greater horizontal hip and knee

displacement in less-skilled lifters (LSL)

– greater trunk angle in LSL

– bar velocity on descent greater in LSL

creating greater " bounce "

– ascent bar velocity is similar at initial drive

but less during sticking point in (LSL)

=========================

• Fry, A. (1993a,

– slight angle outward in feet allow knee to

track in line with feet and also to attain

squat depth

– an upright posture is preferred

– forward lean is necessary, however, to

obtain proper mechanics

– low bar squats result in greater forward

lean

===========================

• Escamilla, R. (2001)

– Powerlifters use more hip force then knee

as compared to other lifters

• Greater trunk lean involves more hip and back

– Low bar squats elicit greater contribution

from the hamstrings, decreasing ACL

strain, as well as shear and compressive

knee forces

– Vasti muscles are more active then rectus

femoris

– Hamstrings more active in ascent

============================

Kinetic Squat Analysis

• McLaughlin, et. al (1978)

– Trunk extensors produce more torque than

thigh and lower leg

– Trunk lean affects torque distribution

inversely

– Highly-skilled lifters maintain a more erect

trunk position, causing thigh extensor

dominant lifting

– These results suggest a lifting paradox

exists with trunk lean and thigh and trunk

contribution

==========================

Kinetics of Soft Tissue

• Escamilla R. (2001)

– Quads generate 2000N to 8000N of force

– Ultimate failure of PCL and ACL are estimated at 4000N

and 2160N respectively

– Failure of the patellar tendon is estimated between

10,000N and 15,000N

– Quadriceps rupture unlikely: quadriceps tendon strength

is greater then that of the patellar tendon (about 35%-

40% thicker).

– Knee shear no different in narrow vs wide stance,

however, tibial compressive force is greater in wide

stance – suggests foot modification absorbs sheer at

the knee due to tracking changes

===========================

Patellar Kinetics in Squats

• Escamilla R. (2001)

– Patella compressive force is greater as depth of

squat increases (max force between 50o and 80o)

– Patella compressive force is greater eccentrically

– No difference in patella compressive force with

feet angled out or in

– Patella compressive force is greater in wide

stance squatting

– Powerlifters had lower patella compressive force

– Low bar squat produces greater hip extensor

torques while high bar squats produced greater

knee extensor torques

– Powerlifters show less patellar compressive force

========================================

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

A preliminary comparison of front and back squat exercises.

PJ, 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.

==================================

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.

=======================

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, kson 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.

==============================

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.

*** 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.

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.

========================

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.

*** 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.

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.

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.

*** 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.

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.

=======================

Carruthers

Wakefield, UK