Hip and Knee Flexion training

[k_dean_curtis]

Squats and Deadlifts hit hip and knee extension. However, for hip and knee flexion, which is very important for sprinting, I cannot see from the biomechanics texts how the Rectus Femoris and Biceps Femoris short head are being trained by such lifts. These are susceptible to injury in sprinting.

Isometric contraction is not adequate for these dynamic movers, i.e. not the same as the erectors, et al.

What is the SS stance on training these muscles?
Thanks

[Mark Rippetoe]

You cannot see how all the hamstrings and all the quads are not made stronger by squats and deadlifts? Sez here you've been on the boards for 8 years. You haven't read the books?

[k_dean_curtis]

Coach Rip,
Thanks for responding. I have all 3 books: SS, PP, BBRx. Have read them many times and understand them.

The biomechanics texts say that both muscles mentioned contract isometrically in hip and knee extension. On the concentric phase the rectus is shortening at the knee and lengthening at the hip, total length does not really change, hence an isometric contraction. Is this statement correct?

If the above is correct, are isometrics good enough for the flexors?
Thanks

[Mark Rippetoe]

This statement is correct, as we point out on Saturday morning at the seminar in the discussion of the squat. I don't understand your question.

[k_dean_curtis]

Sorry for the confusion.
If said contraction is isometric, then your assertion is that IS good enough to strengthen and grow the flexors.
Same for many other muscles in the big lifts, e.g. neck, traps, etc.
Thanks for your time.

[Mark Rippetoe]

If the squat and deadlift go from 200/275 to 405/475, what has happened to the strength of the particular muscles you're worried about?