Squat

[carla]

Jeg vil gerne have stærere muskler i for- og baglår (i forbindelse med løb) og forsøger med squat øvelsen, men det gør ondt i knæene - hvad gør jeg mon galt ? Skal man bruge begge ben lige meget eller er der mest fokus på det foreste eller bagerste ben ?

(jeg har tendens til løberknæ og vil derfor prøve at styrketræne for jeg har prøvet alt andet)

[Steve999]

Det lyder som lunges du snakker om. Ved squat skulle benene gerne stå ved siden af hinanden.

http://www.motiononline.dk/oev_biblio/squat.htm

Der kan du se øvelsen.

Få evt. en instruktør til at vise dig den.

et par tips:

Sørg for at holde knæene så langt tilbage som muligt. Helst bag tæerne.

Hold dig fra at squatte i det såkaldte Smith-stativ hvor stangen er "låst fast"

Kør helt i bund. Dvs røven i jorden. På denne måde skåner du dine knæ bedst.

[BrianH]

Du skal IKKE køre helt i bund. Det er kun til vandret. Det er det sidste stykke, der er dårligt for knæene - især meniskerne. Det står der forresten også i den artikel her fra siden, som du henviser til.

[Steve999]

*BEEP* wrong answer.

Tjek min tråd helt nede i bunden.

[BrianH]

"The "not going beyond parallel" theory still holds some water for those who

are post-surgical or who've been diagnosed as having patellofemoral

dysfunction."

Måske skulle man overveje, når hun siger, at hun har tendenser til at få ondt i knæene ved vægttræning - om det er så smart at anbefale dybe squats - jeg tror det ikke! Hvad nytte har en øger hypertrofi(/hyperplasi), hvis man bliver nødt til at opgive træningen efter kort tid?

Ligeledes henviser jeg lige til en artikel, der giver mig ret :-)

http://www.ncbi.nlm.nih.gov/entrez/query.f...p;dopt=Abstract

(Redigeret af BrianH 1:48 pm - Feb. 27, 2001)

[Mikkel Gybel]

Nu er Testoterone Magazine ikke lige det tidsskrift, jeg ville fæste mest lid til.

Der findes nok ikke mange steder i denne verden, hvor der er flere myter om hvad der er godt eller skidt end indenfor bodybuilding.

[Jens Andersen]

I dette tilfælde vil jeg give Brian fuldstændig ret, da en stor belastning samt en fuld bøjning af knæet presser menisken meget.

Jeg selv er et udemærket eksempel da jeg få to år siden flækkede menisken i højre knæ samt skadede menisken i venstre, efter overtræning med vægte og kamptræning (Jiu-jitsu, Taekwondo)

I dag er jeg færdig med at dyrke seriøs sport da min menisk i højre knæ ikke rigtig stod til at redde - Så mit råd er artikel eller ej at ikke at bøje knæet mere end vandret med vægtbelastning.

Jens Andersen

[Guest]

Her er lidt information omkring dybe squats, benspark, bencurl mv. som jeg har fået fra en forsker jeg kender i USA.

/Niels

Escamilla RF   Knee biomechanics of the dynamic squat exercise   Med Sci

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

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.

My Note:  Epidemiological studies comparing Weightlifting and Powerlifting

injury patterns do not corroborate the suggestion above that deep squats are

necessarily more risky than half squats.  Some biomechanical studies even

state that half squats impose a greater patellofemoral force than full

squats, so that they may be inherently less safe.  Some coaches and lifters

stress that it is relaxation of the muscles at the bottom of the squat which

makes the full squat more dangerous and that the full squat per se is not

morre dangeorus than the half squat. Almost heretically, other lifters remark

that ballistic recoil off tensed muscles out of the deep squat position is

safer than slow controlled squatting, but I have not come across any research

which substantiates this point of view.

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

Escamilla RF, Fleisig GS, Zheng N, Barrentine SW, Wilk K & Andrews JR    

Biomechanics of the knee during closed kinetic chain and open kinetic chain

exercises.   Med Sci Sports Exerc 1998 Apr; 30(4): 556-69

PURPOSE: Although closed (CKCE) and open (OKCE) kinetic chain exercises are

used in athletic training and clinical environments, few studies have

compared knee joint biomechanics while these exercises are performed

dynamically. The purpose of this study was to quantify knee forces and muscle

activity in CKCE (squat and leg press) and OKCE (knee extension). M

ETHODS: Ten male subjects performed three repetitions of each exercise at

their 12-repetition maximum. Kinematic, kinetic, and electromyographic data

were calculated using  video cameras (60 Hz), force transducers (960 Hz), and

EMG (960 Hz). Mathematical muscle modeling and  optimization techniques were

employed to estimate internal muscle forces.

RESULTS: Overall, the squat  generated approximately twice as much hamstring

activity as the leg press and knee extensions. Quadriceps  muscle activity

was greatest in CKCE when the knee was near full flexion and in OKCE when the

knee was  near full extension. OKCE produced more rectus femoris activity

while CKCE produced more vasti muscle  activity. Tibiofemoral compressive

force was greatest in CKCE near full flexion and in OKCE near full  

extension. Peak tension in the posterior cruciate ligament was approximately

twice as great in CKCE, and  increased with knee flexion. Tension in the

anterior cruciate ligament was present only in OKCE, and occurred near full

extension. Patellofemoral compressive force was greatest in CKCE near full

flexion and in the mid-range of the knee extending phase in OKCE.

CONCLUSION: An understanding of these results can help in choosing

appropriate exercises for rehabilitation and training.

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

Stuart MJ, Meglan D, Lutz G, Growney E & An K  Comparison of intersegmental

tibiofemoral joint forces and muscle activity during various closed kinetic

chain exercises.   Am J Sports Med 1996 Nov-Dec; 24(6): 792-9

The purpose of this study was to analyze intersegmental forces at the

tibiofemoral joint and muscle activity during three commonly prescribed

closed kinetic chain exercises: the power squat, the front squat, and the

lunge.

Subjects with anterior cruciate ligament-intact knees performed repetitions

of each of the three exercises using a 223-N (50-pound) barbell. The results

showed that the mean tibiofemoral shear force was posterior (tibial force on

femur) throughout the cycle of all three exercises. The magnitude of the

posterior shear forces increased with knee flexion during the descent phase

of each exercise. Joint compression forces remained constant throughout the

descent and ascent phases of the power squat and the front squat. A net

offset in extension for the moment about the knee was present for all three

exercises. Increased quadriceps muscle activity and the decreased hamstring

muscle activity are required to perform the lunge as compared with the power

squat and the front squat.

A posterior tibiofemoral shear force throughout the entire cycle of all three

exercises in these subjects with anterior cruciate ligament-intact knees

indicates that the potential loading on the injured or reconstructed anterior

cruciate ligament is not significant. The magnitude of the posterior

tibiofemoral shear force is not likely to be detrimental to the injured or

reconstructed posterior cruciate ligament. These conclusions assume that the

resultant anteroposterior shear force corresponds to the anterior and

posterior cruciate ligament forces.

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

Wilk KE, Escamilla R, Fleisig G, Barrentine S, Andrews J & Boyd M   A

comparison of tibiofemoral joint forces and electromyographic activity during

open and closed kinetic chain exercises.    Am J Sports Med 1996 Jul-Aug;

24(4): 518-27

We chose to investigate tibiofemoral joint kinetics (compressive force,

anteroposterior shear force, and  extension torque) and electromyographic

activity of the quadriceps, hamstring, and gastrocnemius muscles  during open

kinetic chain knee extension and closed kinetic chain leg press and squat.

Ten uninjured male  subjects performed 4 isotonic repetitions with a 12

repetition maximal weight for each exercise. Tibiofemoral  forces were

calculated using electromyographic, kinematic, and kinetic data. During the

squat, the maximal  compressive force was 6139 ± 1708 N, occurring at 91

degrees of knee flexion; whereas the maximal  compressive force for the knee

extension exercise was 4598 ± 2546 N (at 90 degrees knee flexion). During the

closed kinetic chain exercises, a posterior shear force (posterior cruciate

ligament stress) occurred throughout the range of motion, with the peak

occurring from 85 degrees to 105 degrees of knee flexion. An anterior shear

force (anterior cruciate ligament stress) was noted during open kinetic chain

knee extension from 40 degrees to full extension; a peak force of 248 ± 259 N

was noted at 14 degrees of knee flexion. Electromyographic data indicated

greater hamstring and quadriceps muscle co-contraction during the squat

compared with the other two exercises.

During the leg press, the quadriceps muscle electromyographic activity was

approximately 39% to 52% of maximal velocity isometric contraction; whereas

hamstring muscle activity was minimal (12% maximal velocity isometric

contraction). This study demonstrated significant differences in tibiofemoral

forces and muscle activity between the two closed kinetic chain exercises,

and between the open and closed kinetic chain exercises.

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

Pandy MG & Shelburne K  Dependence of cruciate-ligament loading on muscle

forces and external load.    J Biomech 1997 Oct; 30(10): 1015-24

A sagittal-plane model of the knee is used to predict and explain the

relationships between the forces developed by the muscles, the external loads

applied to the leg, and the forces induced in the cruciate ligaments during

isometric exercises.

The geometry of the model bones is adapted from cadaver data. Eleven elastic

elements describe the geometric and mechanical properties of the cruciate

ligaments, the collateral ligaments, and the posterior capsule. The model is

actuated by 11 musculotendinous units, each unit represented as a

three-element muscle in series with tendon. For isolated contractions of the

quadriceps, ACL force increases as quadriceps force increases for all flexion

angles between 0 and 80 degrees; the ACL is unloaded at flexion angles

greater than 80 degrees. When quadriceps force is held constant, ACL force

decreases monotonically as knee-flexion angle increases. The relationship

between ACL force, quadriceps force, and knee-flexion angle is explained by

the geometry of the knee-extensor mechanism and by the changing orientation

of the ACL in the sagittal plane.

For isolated contractions of the hamstrings, PCL force increases as

hamstrings force increases for all flexion angles greater than 10 degrees;

the PCL is unloaded at flexion angles less than 10 degrees. When hamstrings

force is held constant, PCL force increases monotonically with increasing

knee flexion. The relationship between PCL force, hamstrings force, and

knee-flexion angle is explained by the geometry of the hamstrings and by the

changing orientation of the PCL in the sagittal plane.

At nearly all knee-flexion angles, hamstrings co-contraction is an effective

means of reducing ACL force. Hamstrings co-contraction cannot protect the ACL

near full extension of the knee because these muscles meet the tibia at small

angles near full extension, and so cannot apply a sufficiently large

posterior shear force to the leg. Moving the restraining force closer to the

knee-flexion axis decreases ACL force; varying the orientation of the

restraining force has only a small effect on cruciate-ligament loading.

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

Note what this next reference says about squats versus knee extension

exercises:

Yack HJ, Collins C &  Whieldon T   Comparison of closed and open kinetic

chain exercise in the anterior cruciateligament-deficient knee.   Am J Sports

Med 1993 Jan-Feb; 21(1): 49-54

The purpose of this study was to quantify the amount of anterior tibial

displacement occurring in anterior cruciate ligament-deficient knees during

two types of rehabilitation exercises: 1) resisted knee extension, an open

kinetic chain exercise; and 2) the parallel squat, a closed kinetic chain

exercise. An electrogoniometer system was applied to the anterior cruciate

ligament-deficient knee of 11 volunteers and to the uninvolved normal knee in

9 of these volunteers. Anterior tibial displacement and the knee flexion

angle were measured during each exercise using matched quadriceps loads and

during the Lachman test.

The anterior cruciate ligament-deficient knee had significantly greater

anterior tibial displacement during extension from 64 degrees to 10 degrees

in the knee extension exercise as compared to the parallel squat exercise. In

addition, the amount of displacement during the Lachman test was

significantly less than in the knee extension exercise, but significantly

more than in the parallel squat exercise. No significant differences were

found between measurements in the normal knee.

We concluded that the stress to the anterior cruciate ligament, as indicated

by anterior tibial displacement, is minimized by using the parallel squat, a

closed kinetic chain exercise, when compared to the relative anterior tibial

displacement during knee extension exercise.

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

Note what this reference says about exercises, such as supine leg curls,

which significantly recruit gastrocnemius during rehabilitation after knee

injury.  This information should be carefully considered by any therapists

who still insist on treating cruciate ligament injuries with leg curls.

Durselen L, Claes L & Kiefer H   The influence of muscle forces and external

loads on cruciate ligament strain.   Am J Sports Med 1995 Jan-Feb; 23(1):

129-36

We know it is important to avoid excessive strain on reconstructed ligaments,

but we do not know how individual muscles affect cruciate ligament strain. To

answer this, we studied the effect of muscle forces and external loads on

cruciate ligament strain.

Nine cadaveric knee joints were tested in an apparatus that allowed

unconstrained knee joint motion. Quadriceps, hamstring, and gastrocnemius

muscle forces were simulated. Additionally, external loads were applied such

as varus-internal or valgus-external rotation forces. Cruciate ligament

strain was recorded at different knee flexion angles. Activation of the

gastrocnemius muscle significantly strained the posterior cruciate ligament

at flexion angles larger than 40 degrees. Quadriceps muscle activation

significantly strained the anterior cruciate ligament when the knee was

flexed 20 degrees to 60 degrees and reduced the strain on the posterior

cruciate ligament in the same flexion range. Activation of the hamstring

muscles strained the posterior cruciate ligament when the knee was flexed 70

degrees to 110 degrees. Combined varus and internal rotation forces

significantly increased anterior cruciate ligament strain throughout the

flexion range.

The results suggest that to minimize strain on the ligament after posterior

cruciate ligament surgery, strong gastrocnemius muscle contractions should be

avoided beyond 30 degrees of knee flexion. The study also calls into question

the use of vigorous quadriceps exercises in the range of 20 degrees to 60

degrees of knee flexion after anterior cruciate ligament