EMG data: muscle activation
|
bs |
fs |
Hamstring
(biceps femoris and semitendinosus) |
Higher |
Lower |
Quadriceps |
|
|
Vastus lateralis |
Lower |
Higher |
Rectus femoris |
Lower |
Higher |
Vastus medialis |
Similar |
Similar |
Low back (erector spinae) |
Lower |
Higher |
Biomechanical analysis |
|
|
Compressive force |
Higher |
Lower |
Knee extensor moments |
Higher |
Lower |
Shear stress |
Similar |
Similar |
The authors suggest that if you have knee problems, such as ligament damage or meniscus tears, or if you have problems with osteoarthritis, then you may want to stick with the front squat since compressive forces can damage knee cartilage.
Compression forces, as their name implies, are forces that flatten or squeeze a material. In the case of the knee, compression forces squeeze cartilage.
Shear forces (stresses) are forces that run perpendicular (90°) from the material — in this case the knee. Imagine a stack of books. Now imagine trying to remove one book from the middle of the pile without disturbing the others. You probably wouldn’t try to retrieve that book by grabbing its edge and pulling it upwards; you’d probably push the book sideways and try to slide it out, right? That’s shear force.Gullett JC, Tillman MD, Gutierrez GM, Chow JW. A biomechanical comparison of back and front squats in healthy trained individuals. Journal of Strength and Conditioning Research. 2009 Jan;23(1):284-92.
References
1. Baechle TR and Earle R. Essentials of Strength and Conditioning (2nd ed). Champaign: Human Kinetics, 2000: 366-369.
2. Escamilla, RF. [link widoczny dla zalogowanych Użytkowników]. Med Sci Sports Exerc. 2001 Jan; 33(1): 127-41. Review.
3. Andrews JG, Hay JG and Vaughan CL. Knee shear forces during a squat exercise using a barbell and a weight machine. Biomechanics VIII B.H. Matsui and K. Kobayashi, eds. Champaign: Human Kinetics, 1983: 923-927.
LUO tlumacz bo mnie juz powoli krew zalewa a ty pisales ze masz cierpliwosc...