Open vs Closed Chain Knee Training

[Guest guest]

Here is some interesting research which examines knee kinematics and compares

the various forces produced in the knee joint by exercises such as squats,

leg presses and knee extensions.

Note in the first two articles that the old therapeutic favourite, knee

extensions, stresses the ACL (anterior cruciate ligament), whereas the squat

and leg press do not (note in the last article that this relates to the type

of squat being used). The compressive force between femur and tibia is also

greatest during knee extensions. Note, however, that PCL (posterior cruciate

ligament) is exposed to about twice the force during the squat compared with

knee extensions. No doubt these findings will be of interest to therapists

on this list. One clear message is that knee extensions should be avoided as

a primary method of ACL rehabilitation.

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Zheng N, Fleisig GS, Escamilla RF, Barrentine SW

An analytical model of the knee for estimation of internal forces during

exercise. J Biomech 1998 Oct; 31(10): 963-7

An analytical model of the knee joint was developed to estimate the forces at

the knee during exercise. Muscle forces were estimated based upon

electromyographic activities during exercise and during maximum voluntary

isometric contraction (MVIC), physiological cross-sectional area (PCSA),

muscle fiber length at contraction and the maximum force produced by an unit

PCSA under MVIC. Tibiofemoral compressive force and cruciate ligaments'

tension were determined by using resultant force and torque at the knee,

muscle forces, and orientations and moment arms of the muscles and ligaments.

An optimization program was used to minimize the errors caused by the

estimation of the muscle forces. The model was used in a ten-subject study of

open kinetic chain exercise (seated knee extension) and closed kinetic chain

exercises (leg press and squat). Results calculated with this model were

compared to those from a previous study which did not consider muscle length

and optimization.

Peak tibiofemoral compressive forces were:

3285 ± 1927 N during knee extension.

3155 ±755 N during leg press

3134 ± 1040 N during squat

Peak posterior cruciate ligament tensions were:

1868 ± 878 N during squat,

1866 ± 383 N during leg press

959 ± 300 N for seated knee extension.

No significant anterior cruciate ligament (ACL) tension was found during leg

press and squat.

Peak ACL tension was 142 ±257 N during seated knee extension.

It is demonstrated that the current model provided better estimation of knee

forces during exercises, by preventing significant overestimates of

tibiofemoral compressive forces and cruciate ligament tensions. >

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Escamilla RF, Fleisig GS, Zheng N et al

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).

METHODS: 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 (Open Chain)

when the knee was near full extension. OKCE (Open Chain) produced more rectus

femoris activity while CKCE (Closed Chain) 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 (Closed Chain) ,

and increased with knee flexion. Tension in the anterior cruciate ligament

was present only in OKCE (Open Chain), 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.

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Escamilla RF, Fleisig G S et al

Effects of technique variations on knee biomechanics during the squat and leg

press. Med Sci Sports Exerc 2001 Sep; 33(9):1552-66

PURPOSE: The specific aim of this project was to quantify knee forces and

muscle activity while performing squat and leg press exercises with technique

variations.

METHODS: Ten experienced male lifters performed the squat, a high foot

placement leg press (LPH), and a low foot placement leg press (LPL) employing

a wide stance (WS), narrow stance (NS), and two foot angle positions (feet

straight and feet turned out 30 degrees ).

RESULTS: No differences were found in muscle activity or knee forces between

foot angle variations. The squat generated greater quadriceps and hamstrings

activity than the LPH and LPL, the WS-LPH generated greater hamstrings

activity than the NS-LPH, whereas the NS squat produced greater gastrocnemius

activity than the WS squat. No ACL forces were produced for any exercise

variation. Tibiofemoral (TF) compressive forces, PCL tensile forces, and

patellofemoral (PF) compressive forces were generally greater in the squat

than the LPH and LPL, and there were no differences in knee forces between

the LPH and LPL. For all exercises, the WS generated greater PCL tensile

forces than the NS, the NS produced greater TF and PF compressive forces than

the WS during the LPH and LPL, whereas the WS generated greater TF and PF

compressive forces than the NS during the squat. For all exercises, muscle

activity and knee forces were generally greater in the knee extending phase

than the knee flexing phase.

CONCLUSIONS: The greater muscle activity and knee forces in the squat

compared with the LPL and LPH implies the squat may be more effective in

muscle development but should be used cautiously in those with PCL and PF

disorders, especially at greater knee flexion angles. Because all forces

increased with knee flexion, training within the functional 0-50 degrees

range may be efficacious for those whose goal is to minimize knee forces. The

lack of ACL forces implies that all exercises may be effective during ACL

rehabilitation.

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Stuart MJ, Meglan DA, Lutz GE, Growney ES, An KN

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.

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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.

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Lutz GE, Palmitier RA, An KN, Chao EY

Comparison of tibiofemoral joint forces during open-kinetic-chain and

closed-kinetic-chain exercises J Bone Joint Surg Am 1993 May; 75(5):732-9

The purpose of this study was to analyze forces at the tibiofemoral joint

during open and closed-kinetic-chain exercises. Five healthy subjects

performed maximum isometric contractions at 30, 60, and 90 degrees of knee

flexion during open-kinetic-chain extension, open-kinetic-chain flexion, and

closed-kinetic-chain exercises. Electromyographic activity of the quadriceps

and hamstrings, as well as load and torque-cell data, were recorded.

Tibiofemoral shear and compression forces were calculated with use of a

two-dimensional biomechanical model.

The results showed that, during the open-kinetic-chain extension exercise,

maximum posterior shear forces (the resisting forces to anterior drawer) of

285 ± 120 newtons (mean and standard deviation) occurred at 30 degrees of

knee flexion and maximum anterior shear forces (the resisting forces to

posterior drawer) of 1780 ± 699 newtons occurred at 90 degrees of knee

flexion.

The closed-kinetic-chain exercise produced significantly less posterior shear

force at all angles when compared with the open-kinetic-chain extension

exercise. In addition, the closed-kinetic-chain exercise produced

significantly less anterior shear force at all angles except 30 degrees when

compared with the open-kinetic-chain flexion exercise. Analysis of

tibiofemoral compression forces and electromyographic recruitment patterns

revealed that the closed-kinetic-chain exercise produced significantly

greater compression forces and increased muscular co-contraction at the same

angles at which the open-kinetic-chain exercises produced maximum shear

forces and minimum muscular co-contraction.

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Toutoungi DE, Lu TW, Leardini A, Catani F, O'Connor JJ.

Cruciate ligament forces in the human knee during rehabilitation exercises.

Clin Biomech (Bristol, Avon) 2000 Mar; 15(3): 176-87

OBJECTIVE: To determine the cruciate ligament forces occurring during typical

rehabilitation exercises.Design. A combination of non-invasive measurements

with mathematical modelling of the lower limb.Background. Direct measurement

of ligament forces has not yet been successful in vivo in humans. A promising

alternative is to calculate the forces mathematically.

METHODS: Sixteen subjects performed isometric and isokinetic or squat

exercises while the external forces and limb kinematics were measured.

Internal forces were calculated using a geometrical model of the lower limb

and the " dynamically determinate one-sided constraint " analysis procedure.

RESULTS: During isokinetic/isometric extension, peak anterior cruciate

ligament forces, occurring at knee angles of 35-40 degrees, may reach 0.55x

body-weight. Peak posterior cruciate ligament forces are lower and occur

around 90 degrees. During isokinetic/isometric flexion, peak posterior

cruciate forces, which occur around 90 degrees, may exceed 4x body-weight;

the anterior cruciate is not loaded. During squats, the anterior cruciate is

lightly loaded at knee angles up to 50 degrees, after which the posterior

cruciate is loaded. Peak posterior cruciate forces occur near the lowest

point of the squat and may reach 3.5x body-weight.

CONCLUSIONS: For anterior cruciate injuries, squats should be safer than

isokinetic or isometric extension for quadriceps strengthening, though

isokinetic or isometric flexion may safely be used for hamstrings

strengthening. For posterior cruciate injuries, isokinetic extension at knee

angles less than 70 degrees should be safe but isokinetic flexion and deep

squats should be avoided until healing is well-advanced.

RELEVANCE: Good rehabilitation is vital for a successful outcome to cruciate

ligament injuries. Knowledge of ligament forces can aid the physician in the

design of improved rehabilitation protocols.

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The following study showed that closed chain exercise (the squat) produces

far greater improvement in " functional " strength and jumping ability than

open chain exercise (knee extension). Even though tests showed significant

improvements in isotonic strength, this strength did not transfer to the

isokinetic knee extension, confirming what we already know, namely that

strength training tends to be very specific. Yet, there are still those who

doggedly avoid the squat and maintain that knee extension and similar types

of machine training are just as good for sporting function.

Augustsson J, Esko A, Thomee R, Svantesson U

Weight training of the thigh muscles using closed vs. open kinetic chain

exercises: a comparison of performance enhancement J Orthop Sports Phys

Ther 1998 Jan; 27(1):3-8

Dept of Rehabilitation Medicine, Goteborg University, Sweden.

Resistance training is commonly used in sports for prevention of injuries and

in rehabilitation. The purpose of this study was to compare closed vs. open

kinetic chain weight training of the thigh muscles and to determine which

mode resulted in the greatest performance enhancement.

Twenty-four healthy subjects were randomized into a barbell squat or a knee

extension and hip adduction variable resistance weight machine group and

performed maximal, progressive weight training twice a week for 6 weeks. All

subjects were tested prior to training and at the completion of the training

period. A barbell squat 3-repetition maximum, an isokinetic knee extension

1-repetition maximum, and a vertical jump test were used to monitor effects

of training. Significant improvements were seen in both groups in the barbell

squat 3-repetition maximum test.

The closed kinetic chain group improved 23 kg (31%), which was significantly

more than the 12 kg (13%) seen in the open kinetic chain group. In the

vertical jump test, the closed kinetic chain group improved significantly, 5

cm (10%), while no significant changes were seen in the open kinetic chain

group.

A large increase of training load was observed in both subject groups;

however, improvements in isotonic strength did not transfer to the isokinetic

knee extension test. The results may be explained by neural adaptation,

weight training mode, and specificity of tests.

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This study also concluded that closed kinetic chain training appears to be

more effective than joint isolation exercise in restoring function in

patients with patellofemoral pain and dysfunction.

Stiene HA, Brosky T, Reinking MF, Nyland J, Mason MB.

A comparison of closed kinetic chain and isokinetic joint isolation exercise

in patients with patellofemoral dysfunction. J Orthop Sports Phys Ther 1996

Sep;24(3):136-41

Recently, there has been attention to the clinical application of closed

kinetic chain and joint isolation exercise. Our purpose was to compare the

effect of joint isolation and closed kinetic chain exercise on quadriceps

muscle performance and perceived function in patients with patellofemoral

pain. Twenty-three patients participated in an 8-week training period and

were assigned to either a closed kinetic chain or a joint isolation exercise

training group. An 8-inch (20.3 cm) retro step-up test was performed at

baseline, 8 weeks, and 1 year. Seated knee extension testing was measured at

baseline and at 8 weeks using peak concentric torque on an isokinetic

dynamometer at 90 degs/sec, 180 degs/sec, and 360 degs/sec. Perceived

functional status was rated as excellent, good, fair, or poor based on

questionnaire response.

Statistical analysis showed that both groups had significant improvement in

peak torque at all speeds, but only the closed kinetic chain group showed

significant improvement in closed kinetic chain testing and perceived

functional status. We concluded that closed kinetic chain training may be

more effective than joint isolation exercise in restoring function in

patients with patellofemoral dysfunction.

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The findings in the following study demonstrate that maximum knee motion may

not necessarily correspond to the highest forces in the ACL. They also

suggest that hamstring co-contraction with quadriceps is effective in

reducing excessive forces in the ACL especially between 15-60 degs of knee

flexion. This would appear to show that the powerlifting style of squatting

with butt pushed strongly backwards, with glutes and hamstrings strongly

involved, decreases force in the ACL. This has two implications - the

powerlifting squat tends to protect the ACL, but decreases the conditioning

effect on the ACL. The weighlifting " deep knee bend " type of squat may then

offer a superior method of conditioning the ACL, suggesting that powerlifters

or athletes who wish to strengthen their ACLs should periodically include

full weightlifting squats in their routines.

Li G, Rudy TW, Sakane M, Kanamori A, Ma CB, Woo SL

The importance of quadriceps and hamstring muscle loading on knee kinematics

and in-situ forces in the ACL

J Biomech 1999 Apr;32(4):395-400

This study investigated the effect of hamstring co-contraction with

quadriceps on the kinematics of the human knee joint and the in-situ forces

in the anterior cruciate ligament (ACL) during a simulated isometric

extension motion of the knee. Cadaveric human knee specimens (n = 10) were

tested using the robotic universal force moment sensor (UFS) system and

measurements of knee kinematics and in-situ forces in the ACL were based on

reference positions on the path of passive flexion/extension motion of the

knee.

With an isolated 200 N quadriceps load, the knee underwent anterior and

lateral tibial translation as well as internal tibial rotation with respect

to the femur. Both translation and rotation increased when the knee was

flexed from full extension to 30 degs of flexion; with further flexion, these

motion decreased.

The addition of 80 N antagonistic hamstrings load significantly reduced both

anterior and lateral tibial translation as well as internal tibial rotation

at knee flexion angles tested except at full extension. At 30 degs of

flexion, the anterior tibial translation, lateral tibial translation, and

internal tibial rotation were significantly reduced by 18, 46, and 30%,

respectively. The in-situ forces in the ACL under the quadriceps load were

found to increase from 27.8 ± 9.3 N at full extension to a maximum of 44.9 ±

13.8 N at 15 deg of flexion and then decrease to 10 N beyond 60 deg of

flexion. The in-situ force at 15 degs was significantly higher than that at

other flexion angles.

The addition of the hamstring load of 80 N significantly reduced the in-situ

forces in the ACL at 15, 30 and 60 degs of flexion by 30, 43, and 44%,

respectively. These data demonstrate that maximum knee motion may not

necessarily correspond to the highest in-situ forces in the ACL. The data

also suggest that hamstring co-contraction with quadriceps is effective in

reducing excessive forces in the ACL particularly between 15 and 60 degs of

knee flexion.

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Dr Mel C Siff

Denver, USA

Supertraining/