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Squats: Hamstrings or quads?

Bigtex

Bigtex

VIP Member
Aug 14, 2012
914
1,343
Years ago when I worked for Muscle and Fitness I had done an article on training legs. The new editor who I did not get along with wanted me to change my article because he didn't agree with what I had written. Anyway, I described the squats as an exercise that not only worked the quads but also the hamstrings and glutes at the same time. Easy to determine......quite working legs for a month and do squats, your hamstring will kill you. This educated jackass insisted the quads are the only muscle that is active. Despite being a pretty good powerlifter and having a PhD this guy said that what I had described is impossible. .

So what is happening? Unlike most muscle groups the legs work in a much different fashion to stand up or do a squat. This is explained by the Lombard's paradox (1) which describes a paradoxical muscular contraction in humans. When rising to stand from a sitting or squatting position, both the hamstrings and quadriceps contract at the same time, despite their being antagonists to each other.

The rectus femoris biarticular muscle acting over the hip has a smaller hip moment arm than the hamstrings. However, the rectus femoris moment arm is greater over the knee than the hamstring knee moment. This means that contraction from both rectus femoris and hamstrings will result in hip and knee extension. Hip extension also adds a passive stretch component to rectus femoris, which results in a knee extension force. This paradox allows for efficient movement, especially during gait.

Typically we’re taught that muscles work in pairs- as one contracts the other relaxes to facilitate movement- this is referred to as ‘reciprocal inhibition’. However there are certain circumstances where this might not be the case (force coupling of the local and global spinal muscles may well be an example). Another example is that of the relationship between the quads and hamstrings through a flexion-extension cycle such as a squat.

LOMBARD’S PARADOX refers to the biomechanics of a squat patterns where there is simultaneous contraction of both the anterior and posterior thigh muscles. The theory is as follows:

• The hamstrings have a greater moment arm than the rectus femoris (RF) at the hip
• The quadriceps have a greater moment arm at the knee in comparison to the hamstrings

So what?

• As the hamstrings act on the hip but attach farther away from its axis of rotation than the RF; they can generate a greater amount of force than the RF. This allows hip extension to take place
• At the knee, the RF (as well as the VMO, VL and VI) attach further away from the axis of rotation in the knee than the hamstrings do, and as such can generate more force, allowing knee extension to take place.

1. Lombard, W.P., & Abbott, F.M. (1907). The mechanical effects produced by the contraction of individual muscles of the thigh of the frog. American Journal of Physiology, 20, 1-60
 
C

charger69

Member
Jul 4, 2017
70
53
Thank you for that. I do realize that the hams are invoked in squats, but I never really thought in depth like you laid it out.


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The Phoenix

The Phoenix

VIP Member
Jul 29, 2014
709
433
You use both but I assign squats with quads days (I split front and back sides).
 
C

C T J

Crossfit VIP
Jan 24, 2013
2,424
683
my glute/ham tie-in and quads are always blasted after squat day.
 
The other Snake

The other Snake

VIP Member
Aug 19, 2016
610
648
Years ago when I worked for Muscle and Fitness I had done an article on training legs. The new editor who I did not get along with wanted me to change my article because he didn't agree with what I had written. Anyway, I described the squats as an exercise that not only worked the quads but also the hamstrings and glutes at the same time. ....
Please tell me you're fukkin kidding.

I'd love to hear him talk about what muscles are activated in the DL. LOL
 
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