The Importance of Timing Vertical Force and Pelvis Rotation
A recent thread on Twitter by Driveline Baseball’s Director of Player Development, Sam Briend, highlighted a similarity in the ground mechanics of striking and throwing sports that is rarely discussed. For those who are unfamiliar, Driveline is one of the leading organizations that specializes in data-driven training of baseball hitters and pitchers. They’ve done a ton to pioneer new philosophy and the integration of technology with instruction and training.
Briend’s entire thread is instructive and evidence of the enriched coaching experience that technology offers, but something that stood out to us was the importance of timing pelvic rotation and foot contact (and lead leg force).
THREAD: I put this together as a way to help visualize kinetic sequencing a bit easier. Thanks to our mocap assessment I’ve spent a lot of time looking at athletes sequencing and its importance in both health and performance, so I’m going to break it down for you a bit. pic.twitter.com/8u99guWcmD— Sam Briend (@SBriend97) February 28, 2019
“For me this is the most important piece in creating proper sequencing. If the timing of the pelvis opening into foot plant is off, we won’t be able to utilize the lead leg and maximize the rotational uncoiling of the upper body.”
One of the core messages of Briend’s post was to emphasize the importance of having the hip open (to home plate) prior to foot plant with front leg, but it also underscores the importance of adequate strength and stability in the lead leg to generate speed up the kinetic chain.
“When the lead leg hits, if the pelvis has opened enough, eccentric braking forces begin driving energy up the chain. Pelvis rotational speeds (~761.9°/s) spike around foot contact and are maximized slightly post by athletes with good blocks.”
Lead Leg Force is a hallmark of many high-velocity pitchers and a KPI for coaches and trainers (here’s a great post from Driveline outlining the importance of lead leg mechanics in pitching). One of the key indicators of force is flexion of the lead knee. If flexion increases from foot plant to ball release, it’s indicates a loss of potential power, often referred to as a collapsed front knee. Here’s a thread from Kyle Rogers, Driveline’s Lead Strength Trainer, discussing how he evaluates and trains force in the lead leg.
From his biomechanics report, we can see that his front knee flexion increased from 51 degrees at foot contact to 52 degrees at ball release. Ideally we want front knee flexion to decrease meaning that our lead leg is slamming on the breaks and propelling the trunk into flexion. pic.twitter.com/SfdydbL5CH— Kyle Rogers (@KyleRogers18) March 5, 2019
We’ve talked a lot about the importance of lead leg force in golf. Whether creating speed, resisting early extension or generating rotation, understanding the function of the lead leg is critically important in golf.
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Justin Thomas and Jimmy Walker represent two of the extremes in lead leg extension on TOUR. Look at the change from lead arm parallel to impact. Jimmy maintains flexion while Thomas’ lead knee is almost in hyperextension.
There is more variance in golf than in baseball pitching, but the principles for how, why and when vertical force occurs in relation to pelvis turn are very similar.
Here’s Sasho MacKenzie during a breakout session at the PGA Show. Since he’s using Rory as an example, here’s a GIF that captures his squat well:
Golfers don’t stride like pitchers do, but there is an important period during transition in which the lead leg is less weighted.
“Even though we want to get that force under the lead leg as high as we can as early as we can, we don’t want it to peak too soon or else it’s going to prevent us from rotating.” – Dr. Sasho MacKenzie
Sasho’s analogy of the shot putter offers a great visual for other rotational athletes. Pay attention to Ashton Eaton, Olympic Gold Medalist in the decathlon, during a shot put attempt here:
Before the foot hits the toe board, the athlete has clearly opened their hips to the sector. Now their lead leg block is able to facilitate rotation up the chain, not impede it.
Most golfers won’t completely unweight their lead foot while rotating their hip, but they need to take advantage of the opportunity create hip rotation before they’ve maximized force under the lead foot.
One of the advantages of using BodiTrak is that we are able to assess not only the magnitude of force, but also the timing of force. Although much less discussed, the latter is nearly as important as the former.