Elitetrack: Sport Training & Conditioning

Try getting ATG in that.

I only have time to answer the point about hamstring activation prior to gc.  The vastus also becomes active at the same time.  Also, as Wiemann points out and I don’t know if it is still true the hamstring can also act a knee extensor while acting as a hip extensor, even if it were not still true, a co-contraction of hamstring and vastus would provide stiffness at the knee joint during support (this idea seems more plausible, although the role of gastroc is not defined in the study as it must also play a role in overall stiffness at the knee as well).  Obviously the Wiemann study doesn’t discuss any hip flexors or their role during sprinting and thus discussion on total action about the hip joint cannot be discussed with reference only to the Wiemann study.  I know their are studies out there with data on knee flexors and hip flexors during sprinting.  I will find them, but I am almost certain there is a high degree of activation of both extensors and flexors at all three joints in the connecting the thigh and shank.

I have a good understanding of muscle activation patterns during walking, running, and sprinting. My understanding is that much of the agonist-antagonist contraction is to increase stiffness and power transfer from the hip and lumbar extensors. I’m really more concerned with whether the the co-contraction results in deceleration of the thigh prior to ground contact. I can’t see how it would and like I said, even if it did, there’s still massive active hip extension through the overwhelming majority of the downward portion of the swing phase.

I won’t disagree with hip extension throughout the downward portion of the leg swing and I won’t disagree that max strength work in fuller ROM squats allows one to increase angular velocity of those joints with a greater angular impulse.  However I do have a couple of questions, is that greater angular impulse directly related to changing/increasing leg stiffness?  If that higher angular velocity is through a greater ROM, is it enough for that velocity to offset the change in ROM?  I still believe even with greater angular velocities generated the muscles in the legs have to deal with those velocities to produce the stiffness necessary to maintain speed and given that step ratse are set to preferred internal controlling (coordinated) structures, most likely to keep a stabilized motor pattern based on leg stiffness and compliance of the previous step and the ROM of the current step as well as the momentum of the COM.  This is all set up in the acceleration pattern is it not? I think it is, the acceleration pattern transistions from a more concentric ssc initiated cyclic activity to a more reactive, elastic ssc-compliant activity in which ROM at each joint goes through a greater to smaller ROM while in contact with the ground as ground contact time decreases.  Even though the activity itself requires greater overall ROM in each joint throughout the unsupported phases of each step.  For some reason, my training progressions fell in line with moving from greater ROM work while in contact with the ground to smaller ones and from smaller ROM work in joints while not in contact with the ground to larger ROM work. 

I just gravitated to it naturally trying to find out what worked.  Remember I used to work long to short, but I changed to a short to long approach with some ends to middle type work as recovery/conditioning in tempo and special endurance 2 as the long end with acceleration and maxV as those the short and speed endurance/special endurance I as the middle.  However most of the work early on is acceleration/maxV work as opposed to tempo/spec II.

dbandre - 14 May 2008 07:59 PM

...is that greater angular impulse directly related to changing/increasing leg stiffness?

I can’t think of any reason to suggest it wouldn’t. It would presumably lead to a stronger co-contraction of leg musculature prior to impact.

If that higher angular velocity is through a greater ROM, is it enough for that velocity to offset the change in ROM?

Not sure I understand. Why does anything need to be offset?