Her 8800 - jeg spammer lige din log lidt Æg - hope you don't mind:
Parallel (100-110 degrees) and deep squats (125-140 degrees) are better:
Quote:
Joint moments of force and quadriceps muscle activity during squatting exercise
P. Wretenberg 1 , Y. Feng 1 , F. Lindberg 1 , U. p. Arboreilus 1
Scandinavian Journal of Medicine & Science in Sports
Volume 3 Issue 4, Pages 244 - 250
KEYWORDS
squatting exercise • Olympic weightlifting • hip • knee • joint load • EMG • biomechanics
ABSTRACT
The relationship between hip and knee joint load and quadriceps muscle activity during squatting exercise to different depths was studied. Eight young national class Olympic weightlifters performed squatting exercise to 4 different knee flexion angles; 45°, 90°, parallel and deep squats. They held a barbell across their shoulders with a weight of 65% of their one-repetition maximum. The loading moments of force about the hip and knee joints were calculated using a semidynamic method. Video was used for motion recording and electromyograhy for recording activity from die vastus lateralis, rectus femoris and biceps femoris muscles. The loading moment on the hip joint increased significantly from the 90° squat to the parallel, but there was no difference between the parallel and the deep. For the knee joint, there was no difference between the 45°, 90° and parallel, but for the deep squat the loading moment increased significantly. The muscular activity generally increased with increasing squatting depth, but mere were only minor insignificant differences between the parallel and the deep squats. We conclude that knee joint load can be limited by doing parallel instead of deep squats and that this will not decrease quadriceps muscle activity. To limit hip moment, the squat should not be deeper than 90°.
Deep squats aren't that bad:
Quote:
J Appl Biomech. 2006 Nov;22(4):305-13.Links
Tibiofemoral joint contact force in deep knee flexion and its consideration in knee osteoarthritis and joint replacement.Nagura T, Matsumoto H, Kiriyama Y, Chaudhari A, Andriacchi TP.
Department of Orthopedic Surgery, Keio University, Shinjyuku, Tokyo, Japan.
The aim of the study was to estimate the tibiofemoral joint force in deep flexion to consider how the mechanical load affects the knee. We hypothesize that the joint force should not become sufficiently large to damage the joint under normal contact area, but should become deleterious to the joint under the limited contact area. Sixteen healthy knees were analyzed using a motion capture system, a force plate, a surface electromyography, and a knee model, and then tibiofemoral joint contact forces were calculated. Also, a contact stress simulation using the contact areas from the literature was performed. The peak joint contact forces (M +/- SD) were 4566 +/- 1932 N at 140 degrees in rising from full squat and 4479 +/- 1478 N at 90 degrees in rising from kneeling. Under normal contact area, the tibiofemoral contact stresses in deep flexion were less than 5 MPa and did not exceed the stress to damage the cartilage. The contact stress simulation suggests that knee prosthesis having the contact area smaller than 200 mm2 may be problematic since the contact stress in deep flexion would become larger than 21 MPa, and it would lead damage or wear of the polyethylene.