Effects of technique variations on knee biomechanics during the squat and leg press.
Medicine & Science in Sports & Exercise. 33(9):1552-1566, September 2001.
ESCAMILLA, RAFAEL F.; FLEISIG, GLENN S.; ZHENG, NAIQUAN; LANDER, JEFFERY E.;
BARRENTINE, STEVEN W.; ANDREWS, JAMES R.; BERGEMANN, BRIAN W.; MOORMAN,
CLAUDE T. III
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.
Ziel: Vergleich Kniebeugen und Beinpresse
Variationen
- niedere und hohe Fußposition bei der Beinpresse,
- breiter und schmaler Stand
- gerade und 30° nach außen gedrehte Fußstellung
Ergebnisse:
- keine Unterschiede bei gerade und 30° nach außen gedrehter Fußstellung
- bei der Kniebeuge tr eten höhere Muskelkräfte für quadriceps und harmsting als bei der
Beinpresse (hohe und niedere Fußposition)
- breiter Stand und hohe Fußposition größere Kraft harmstring als schmaler Stand und hohe Fußposition
- schmaler Stand Kniebeuge g rößere Kraft harmsting als breiter Stand Kniebeuge

High- and low-bar squatting techniques during weight-training
[Applied Sciences: Biodynamics]
WRETENBERG, PER; FENG, YI; ARBORELIUS, ULF P.
Kinesiology Research Group, Department of Neuroscience, Karolinska Institute, S-171 77,
Stockholm, SWEDEN
Submitted for publication December 1993.
1. ABSTRACT TOP
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. parallel squat - the knees are flexed until the posterior borders of the hamstrings muscles are parallel to the floor deep squat - the knees are maximally flexed low bar - the bar is either centered across the shoulders just below the spinous process of the C7 vertebra high-bar - on the back across the spine of the scapula rm - repetition maximum
Methode: Acht Gewichtheber führten Kniebeugen mit high bar und sechs Power-lifter führten
Kniebeugen mit low bar bei einem Gewicht (65% vom RM) aus.
Ergebnisse: Max. Hüftmoment 230Nm bei tiefen und 216 Nm bei mittleren Kniebeugen für die
Gewichtheber
Die Powerlifters hatten 324 Nm bei der tiefen und 309 bei der mittleren Kniebeuge
Kniemoment 191 (tief) und 131 (mittlere) - Gewichtheber
139 (tief) und 92 (mittlere) – Powerlifter
Die Oberschenkelmuskulatur wurde leicht stärker bei den Power lifter aktiviert als bei den
Gewichthebern.

Force/velocity and power/velocity relationships in squat exercise
Journal European Journal of Applied Physiology
Publisher Springer Berlin / Heidelberg
Abderrehmane Rahmani, Fabrice Viale, Georges Dalleau, JeanRené Lacour
The purpose of this study was to describe the force/velocity and power/velocity relationships obtained during squat exercise. The maximal force (F
0
) 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 (r 2 =0.83-0.98, P < 0.05-0.0001).
The extrapolated F
0
was 23% higher than the measured isometric force (P < 0.001), 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° of knee flexion), whereas the dynamic forces were measured through a range of movements (from 90° to 180°). The power/velocity relationship was parabolic in shape for each subject (r 2 =0.94-0.99, P < 0.01-0.0001). 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 ( W£ max
) 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 W£ max
from the power/velocity equation showed that it would be reached for a load close to body mass, or even under unloaded conditions.
Ziel:
Beschreibung von Kraft- Geschwindigkeits- und Leistungs-
Geschwindigkeitsverlauf während
Kniebeugen
Methode:
15 internationale Abfahrer führten maximal-dynamische und isometrische Kniebeugen mit einer geführten Hantelstange aus.
Gewicht zwischen 60 und 180 kg
Ergebnisse:
Linearer Zusammenhang zwischen Kraft und Geschwindigkeit
Kein Zusammenhang zwischen isometrischer und dynamischer Messung
Höchste Leistung bei 60 kg Zusatzgewicht, allerdings könnte die höchste Leistung wahrscheinlich bei geringerem Gewicht erreicht werden.

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° 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° 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° 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.