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Lead Leg Block in Pitchers

Updated: May 5, 2022

What is a lead leg block in pitching?


If you frequent baseball Twitter, then you are probably familiar with the concept of a lead leg block during pitching. If you are unfamiliar with the idea, then you have come to the right place. I want to breakdown what exactly a lead leg block is, why it matters, and what we can do about it. Before we get too far into this, I am not a pitching coach so I am going to explain the mechanics just so that you are familiar with what I am talking about. After that I will be focusing more on joint and muscle forces as well as training. If you are here for pitching mechanics talk then you are in the wrong place.


It is important to understand what the lead leg block looks like in a high level pitcher. Below are several snapshots of Billy Wagner’s delivery.


lead leg block pitching
Rdikeman at the English Wikipedia, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons

Look at his front leg after it makes contact with the ground. It goes from a bent position to a straight position to a very straight position. This is the “block” that is created. When someone pitches, they may follow through and step forward or to the side, but they do not walk down the mound. The reason for this is that the anchoring of the lead leg gives you an axis to rotate around.


Imagine you were trying to punch someone as hard as possible. If you are right handed, you would naturally plant your left foot in front of you and twist to punch. Now imagine walking towards someone and trying to punch them while still walking. You would have significantly less force behind the punch because there is no anchor point between you and the ground. The lead leg is not just passively stopping you, it is creating power by pushing into the ground and sending force up through your body.


Part of the OnBase University screen looks for lead knee collapse. In their system, once the pitcher’s lead foot makes contact with the ground, the knee should not bend anymore. Any bend of the knee is losing potential energy that could be translated up the chain. Imagine trying to lunge and punch someone while your knee is bending, there is a loss of power. Here is an image of a Little League pitcher demonstrating a bent knee after delivering the ball.


lead leg block pitching
https://pxhere.com/en/photo/591057

His body is continuing to glide towards the plate. In order to reach full potential with pitching, not only do we want each segment to accelerate, we also want the segment below it to decelerate. The 4 main segments in the kinematic sequence of pitching are the pelvis, torso, shoulder, and hand. If you kept all 4 segments rotating, you would spin off the mound and lose most of your power. Instead, you want the pelvis to accelerate, but as the torso begins to accelerate the pelvis should decelerate. This pattern continues up the chain. Another visual is cracking a whip. You rapidly accelerate your hand, but you come to a stop to create the momentum. If you simply waved your hand around quickly without stopping there would be no force transfer.


Here is a gif of Shohei Ohtani when he pitched in Japan courtesy of drivelinebaseball.com


lead leg block pitching

Ohtani threw 101 mph while in Japan, so he is clearly transferring power well. Notice how quickly his lead leg extends. He actually has to hop to catch himself because of how quickly it extends and how much force it creates.


Why does lead leg block matter in pitching?


Now that we understand what the lead leg block is and how it works, why do we care about it? I talked about creating a stable base, but this is not where the work stops for the lead leg. Once you release the ball, it has to act as your primary brakes. The back leg is in the air at this point so it is useless and all of the force goes into your lead leg. Our bodies are intuitively very good at protecting themselves. If your brakes are not strong enough to stop the car, then your body will not allow you to accelerate too fast.


Pretend that you could somehow only train the accelerator muscles with throwing. You built up those muscles to the point where you could throw 90 miles per hour. However, you did not train the decelerator muscles, and they can only stop 65 miles per hour. Your body has two options at this point: limit the acceleration or risk it. In most cases, your bodies will limit our acceleration to protect themselves. We can actually go faster than we typically imagine.


Overspeed training takes advantage of this phenomenon by tricking our body into removing the brakes. Imagine running downhill. Your body has the ability to move faster to keep up with the hill and prevent you from faceplanting. If you could somehow unlock that speed on flat ground you could run much faster.


Unlocking greater acceleration can be beneficial for performance, but it also leads to the second option of risking injury if our decelerators are not strong enough. Imagine running down a hill and there is a wall at the bottom of the hill. Your body will typically slow you down so that you do not run into the wall. If you wanted to run as fast as possible, you would not slow down, but you might hit the wall. Throwing 90 miles per hour with brakes that only support 65 miles per hour can only work for so long. A strong lead leg block can provide enhanced deceleration and actually increase acceleration. Below is an example of overspeed training gone wrong courtesy of tenor.com


lead leg block pitching

Research has shown the benefits of a strong lead leg block. The first study by McNally, et al. showed that ground reaction force generated by the lead leg was a significant predictor of velocity. They studied the force generated by both legs and found that the force from the back leg was not relevant to velocity. This is surprising because it might be logical to think that pushing off aggressively from the mound would increase velocity, but it did not and lead leg force was largely responsible instead. It is important to understand that ground reaction force is a measure of force exerted by the lead leg but also what is returned to it from the ground.


Imagine standing on a box and stepping off, but when you land you try to jump as high as possible. You are going to push into the ground as hard as you are able because the ground will return that force. The lead leg block is a similar phenomenon where driving the front foot into the ground will send a force up the leg and lead to pelvic rotation.


Another study by Matsuo, et al. looked at 21 physical factors between high and low velocity pitchers. Lead knee extension angular velocity was one of the main factors associated with high velocity pitchers. The harder throwers actually extend their knee more rapidly than the slower throwers. An important factor to consider is whether the knee extension velocity is a cause or effect. Most pitchers are not attempting to lock their lead knee as fast as possible while pitching. Instead, this movement happens from the ground reaction force traveling up the leg and being transferred into rotational energy. Lead knee extension angular velocity is a good metric to examine, but it is probably a marker for other factors.


How to improve lead leg block


As previously mentioned, I come to the lead leg block from a physical perspective. There are many excellent pitching coaches that can improve your mechanics and help you on the mound. However, problems with a lead leg block can often be strength or power related. Look at two simple exercises that you have probably seen before: the lunge and the single leg deadlift (single leg deadlift picture courtesy of openfit.com)


lead leg block pitching