There goes pattar dropping knowledge again
Very interesting. Especially when comparing max ground force rear vs front leg.Taken from: Fortenbaugh, David. "The biomechanics of the baseball swing." (2011).
GRFz would be the scale measurement and BW=bodyweight
For the stride portion phase:
"Throughout the stride, the trail foot pushed with a constant GRFx of 21% BW
while the GRFz gradually rose from 86% BW to a peak value of 92% BW around −500
59 ms and then began to fall back down to 83% BW.
For swing initiation phase (not sure how he defined this but lets just assume it is close to what we call launch):
"This phase was marked by major movements in the lower body and moderate
movements in the upper body. The lead foot GRFx increased rapidly from 11% BW to
its maximum value of 50% BW while GRFy peaked at 28% BW around −123 ms. By
definition, the lead foot GRFz rose quickly during the swing initiation phase from 50%
BW to its maximum value of 130% BW. The trail foot GRFy also peaked during this
phase (24% BW) around −127 ms, while the trail foot GRFz waned from 47% BW to
34% BW."
For swing acceleration phase (after initiation until contact):
"The lower body was still very active during the beginning of the swing
acceleration phases, while very rapid movements in the upper body occurred just before
BC at the end of phase. All of the GRF dissipated during this phase, both in the lead foot
(Fx: −50% BW to −13% BW; Fy: 24% BW to −5% BW; Fz: 130% BW to 64% BW) and
the trail foot (Fx: 10% BW to −3% BW; Fy: 20% BW to 1% BW; Fz: 34% BW to 15%
BW). "
During the stride, turn the pelvis perpendicular to the pitch while keeping the shoulders parallel to the pitch. At the same time point the front foot toward the pitcher. Stride against a bent front knee. From this position, the front hip is aligned over the knee which is aligned over the toes. Classic squat position. Now push against the front leg using the big muscles. Since the leg can't move the ground, the extension moves the front hip rearward creating greater core torque."Why not move in such a way that the large muscles get involved? "
Tell me more please.
I think the torque move, the rear leg externally rotating while bearing weight and moving the pelvis in the opposite, is a part of the swing. It sets up the hip to shoulder separation and torque the torso.Meant to add to this thread but I got busy!
BobbyS... you left out some very important info on hip rotators.
With a flexed (hinged) hip...the glutes become internal femur rotators (moment arms).
So if a leg is stabilizing..such as the front leg when it catches the weight...they will become external pelvis on femur rotators on same side as the stabilizing leg.... as they go to hip extension. I believe at 90 degrees hip flexion... those glutes are considered a major internal rotator.. There are variations with the various degrees...but this is very important when looking at the hips in a swing. Also why teaching active glutes, hip hinging and extension is important imo.
The torque move mentioned...where the leg torquing into the ground and the pelvis moving in opposite direction....isn't part of the swing. Not saying you were saying that.... I say that because one twitter guru early in the year was touting that as if he had found the holy grail of hitting. That move is great for fielding and cutting but not part of the swing.
If you look closely at the two videos of TM and the boy...the weight bearing knee begins to internally rotate before that move. It gives up the internal rotation because the weight stays on the one leg...then externally rotates. That initial knee movement would of continued to go down and in with the rear hip still loaded. Thats my definition of rear leg driver. Really could care less if someone calls it forward fall though. What ever works for the girl.
To Julray...as far as the original question in this thread.... consider how the knee goes down and in... with a stable/loaded rear hip.....and how the hips move in the opposite direction of lateral spinal flexion (tilt, scrunch, ect)....and how that opens the hips, clears the hips ect. Easy to feel standing on one leg and tilting rearward.
From there with glutes activated...hip extension will take care of the rest of rotation. I don't even mention hip rotation with most of the girls.