A Quantitative Evaluation of the Lead Leg Block and its Contributions to Velocity

Abstract

All through this submit we’ll take a more in-depth have a look at varied features of the lead leg block in pitching, trying by means of our biomechanics database to higher describe how the lead leg block works to allow pitchers to throw more durable. To briefly summarize the primary findings:

-Athletes with extra knee extension after foot plant throw more durable (even inside their very own throws) on common.

-Athletes with extra COG deceleration after foot plant throw more durable on common

-COG deceleration correlates with entrance knee extension considerably

-The block driving quicker or extra complete pelvis rotation after footplant doesn’t distinguish more durable and softer throwers

-Each max vertical and anterior/posterior Floor Response Forces correlate with velocity – with the course of that max pressure various by athlete and never being a big driver on common of pitch velocity

– Many of the related lead leg positions at footplant don’t correlate notably with pitch velocity or the standard of the block.

Intro

With our final weblog on the lead leg block being from 2015, we’ve since built-in our biomechanics lab into our coaching course of for all athletes coaching in-gym and picked up hundreds of throws. Now we have a novel assortment of excessive constancy information with a plethora of pitchers from varied talent ranges and velocities as much as 100mph within the dataset to investigate what the toughest throwers do nicely – which then informs our coaching processes.

Now we have touched on blocking briefly in different blogs since then, comparable to our preliminary SPM weblog, nevertheless we’re dedicating house right here to digging in with extra detail- in addition to analyzing the database with the throwers who’ve assessed within the lab since then. We’re varied discrete metrics right here, so this received’t be as subtle technically as the complete sign evaluation within the SPM weblog, however is ample to deal with a wide range of particular questions and hypotheses of curiosity.

We examine three main kinematic elements of blocking: knee extension, linear middle of gravity velocity deceleration, and pelvis rotation. Then we’ll assessment our pressure plate information to contemplate the bottom response forces. To wrap up, we think about how a pitcher’s touchdown place at foot-plant elements into how nicely an athlete is ready to block throughout the kinematic elements thought of.

Knee Extension

How necessary is extending the entrance knee?

To outline knee extension, we have a look at the angle of the entrance knee at foot-plant and at ball launch and calculate the distinction between them. A constructive worth signifies that the knee extends from FP to BR.

Evaluating the throws from every athlete with a repeated measures correlation, we get a reasonably sturdy (within the context of biomechanics correlations to velocity being pretty low throughout the board) correlation of r = 0.29. That is fairly just like the r = 0.27 evaluating entrance knee extension and velocity between completely different throwers. That’s, each athletes who prolong their knee extra throw more durable than athletes who prolong their knees much less and athletes throw more durable once they prolong their knee extra on particular throws of theirs – on common.

A pair examples for example what this seems like:

Positive aspects 34° of knee extension.

Loses 6° of extension.

A nonlinear mannequin suits the information higher,  with the important thing perception being the steep drop off on the low finish – which is to say that athletes who sink into much more flexion at BR relative to the place they have been at FP have essentially the most to achieve by enhancing. On the excessive finish, it does pattern up once more barely, which appears to be pushed by a pair athletes who throw reasonably exhausting with essentially the most knee extension.

If extending the knee is sweet, does that imply flexing the knee in the beginning is particularly dangerous?

For this, we seemed on the most flexed place an athlete reaches between foot plant and ball launch and checked out how rather more flexed this was relative to the knee angle at foot-plant – to contemplate how dangerous it’s to sink into the lead leg extra after foot-plant.

That is strongly associated to how a lot the athlete’s capable of prolong their knee between FP and BR- which ought to come as no shock (with extension being the inverse of flexion and us contemplating a portion of the identical time interval).

Put one other method, should you leak into extra flexion after foot-plant, it’s more durable to have your knee get extra prolonged than it was at footplant. This is smart, since we’re measuring extension in opposition to the worth at foot-plant, so should you sink into 5 levels of extra flexion within the time proper after foot-plant, you now have much less time to increase the knee earlier than ball launch and you’ve got an extra 5 levels it is advisable prolong by means of simply to get again to the place to begin – a lot much less get extra prolonged.

A pair examples illustrating how sinking into extra flexion can differ from the extension from FP to BR for example what every particularly seems like by itself, although they’re typically associated to one another.

Visible for what not gaining flexion seems like (-0.78°)  – with minimal extension from FP to BR (7°)

Visible for what gaining flexion seems like (-12°)  – with extension from FP to BR (16°)

Trying on the relationship between sinking into extra flexion with velocity, we see a weaker pattern than with utilizing knee extension from FP to BR – with many of the noticed pattern being that it’s dangerous to sink into a whole lot of flexion (plot beneath). This relationship is notably weaker than for extension particularly intra-subject the place the r = 0.13 versus 0.29. That’s, an athlete’s throws individually, those the place they prolong their knees extra are likely to correspond to those they threw more durable extra strongly than those the place they sink into extra flexion do – although there’s a weak relationship for sinking into flexion as nicely.

Given the connection between extending the knee from FP to BR and sinking into extra flexion after FP, it is smart to ask if including in how a lot flexion an athlete sinks into impacts their velo after you account for the impact it has on their complete quantity of extension that they acquire. If we throw them in a mixed a number of regression mannequin, we see solely a marginal acquire in mannequin match relative to the mannequin with simply the distinction in knee extension angle (r^2 = 10.34 vs 10.21), suggesting that the connection above between avoiding sinking into flexion and throwing more durable is expounded to how avoiding sinking into extra flexion makes it simpler to increase the knee extra – or some shared mechanism that impacts each – slightly than some extra worth it could present by itself.

To use that interpretation, should you sink into a lot of flexion, it’s going to make it extremely tough to increase your knee in any respect. Nonetheless, should you sink into a bit little bit of flexion – however are capable of prolong your knee (just like the second instance from above), that’s doubtless much less trigger for concern and certain preferable to holding the identical angle the whole time from foot-plant to ball-release.

Moreover, heavier pitchers (r = -0.15) and pitchers who transfer quicker (r = -0.21) each on common sink into very barely extra flexion which can be fascinating to look at.

Effectively what about how briskly you prolong your knee? 

To the touch on entrance knee extension angular velos as nicely, we begin with the three mostly calculated factors: at foot-plant, at ball launch, and the max worth.

Max Entrance Knee Extension Angular Velocity and Entrance Knee Extension Angular Velocity at BR are strongly correlated with one another – so are doubtless redundant.

Each max and at BR correlate decently with velocity – and are comparable in energy with reference to correlation with velocity (r = 0.25 inter-subject, r = 0.20 intra-subject).

Thus, these doubtless present some data and are helpful for assessing blocks, and both one might be used interchangeably.  Athletes who’ve bigger variations between the 2 – who peak their knee extension velo earlier than BR – don’t on common throw notably more durable or slower (r = -0.065 with velocity).

entrance knee extension angular velo at foot-plant (how shortly they’re extending their knee as they plant their foot) – we see a a lot weaker relationship (r = 0.05 intra- and inter- topic). A quadratic match is a smidge higher (the place extending or flexing the knee quickly going into foot-plant are each not optimum) – besides, nonetheless pretty weak to the purpose that I wouldn’t put a lot weight on it.

Be aware that that is weakly correlated with a few of the different entrance knee metrics mentioned above: r = ~0.2 with entrance knee extension from FP to BR (inter- and intra- athlete), r – ~0.15 with max entrance knee extension angular velo (inter- and intra-athlete), r = 0.13 inter- and r=-0.01 intra with entrance knee extension angular velo at br. Which is to say that it does relate some to these different measures – which can be a part of why it has a small quantity of predictive energy.

A pair examples for example how entrance knee extension angular velo at FP can differ from entrance knee extension from foot-plant to ball-release to indicate what it’s particularly measuring:

Positive aspects 35° of extension however from -238°/sec ext velo at FP

Positive aspects 35° of extension however from -238°/sec ext velo at FP

Killing Linear Momentum

How necessary is decelerating middle of gravity motion in the direction of the plate?

One other principal element of the block is lowering linear momentum and transferring that vitality up the chain. Following on Kyle Lindley’s thought for a change in momentum metric , we calculated a metric for the change in COG velocity within the course between the rubber and the plate, from its max to the minimal worth between FP and BR.

Be aware that we see a pattern the place athletes who transfer down the mound quicker are capable of decelerate extra – since they’ve a larger peak worth to work off of. We are able to management for this relationship and get how a lot a specific athlete slows down their COG relative to how a lot we’d count on given their peak COG. That is fairly just like the proportion metric Lindley first calculated – although we take residuals slightly than utilizing a ratio to keep away from the assumptions ratios require, and don’t multiply by weight to keep away from introducing any explanatory energy since heavier athletes will on common throw more durable.

You could possibly hypothesize that stopping COG instantly after foot-plant is an important and looking out all the best way up until ball-release is a comparatively very long time interval to take a look at. If we have a look at solely the primary half of the window from FP to BR (so if, for instance, FP is at body 220 and BR is at 240, frames 220-230) to get an thought of how shortly athletes sluggish their COG shortly after foot-plant, this metric is much less predictive of velocity (r = 0.15 inter-athlete and r = 0.04 intra-athlete).

That metric for COG distinction throughout the entire interval from FP to BR does relate some with entrance knee extension – although notably not completely. As you’ll be able to see within the plots beneath, for a selected entrance knee extension worth there’s a diffusion when it comes to the COG distinction metric:

A pair examples exhibiting how these don’t at all times line-up (that I believed have been fascinating):

Knee extension of 6, however has the highest worth when it comes to killing max COG velo- residual of 0.6.

Entrance knee extension of 36, however COG decel residual  of -0.32 which is  in the direction of the decrease finish.

Be aware that ideally we’d separate out the deceleration of the COG of the decrease half from the higher half. With the COG being the typical weight place of all segments, this metric doesn’t account for athletes who decelerate their decrease half and use that to propel their higher half in the direction of the goal greater than others (because the examples above illustrate). 

Pelvis Rotation and Rotational Acceleration

How necessary is ending Pelvis Rotation and rising Pelvis Rotational Velo after Foot-plant?

The third main element of the block that’s usually talked about (together with changing the linear momentum up the chain, and the knee extending) is driving/ending rotation of the pelvis:

To analyze this, we have a look at how a lot the pelvis rotates between foot plant and ball launch (so pelvis angle at BR – pelvis angle at FP) – which doesn’t notably relate to pitch velo (r = -0.07 inter- and r = 0.10 intra-athlete). 

Be aware that that is strongly associated with pelvis rotation at foot-plant (plot beneath). That’s athletes who land with a extra closed pelvis on common rotate their pelvis extra between foot-plant and ball launch. Controlling for this relationship (to take a look at athletes who rotate their pelvis greater than we’d count on given their pelvis rotation at footplant) doesn’t strengthen the connection with velocity (r = -0.06 inter- and r= 0.10 intra-athlete once more).

pelvis rotational velo slightly than simply the positions, we in contrast pelvis rotational velo at FP with the max after FP (technically 1 body after to keep away from any overlap for individuals who solely decelerate after) as much as BR.

We see a small portion (7.8%) of athletes who’s max pelvis rotational velo after FP isn’t any larger than their pelvis rotational velo at FP, with guys on common rising their pelvis rotational velo by 136°/sec from FP to their max earlier than BR.

This doesn’t correlate notably with velo (r = -0.07 inter-subject and r = -0.01 intra-subject)

This does relate reasonably with pelvis rotation at FP – the place guys who’ve extra closed pelvises at foot plant acquire extra pelvis rotational velo by ball launch (a few of which can be coming from having slower rotating pelvises at FP and a few from having a bigger arc to speed up by means of).

To supply a pair visible examples of what outlier pelvis rotational velo positive factors appear to be – for reference:

Pelvis Rot Velo Acquire of 425 – 98th percentile

Pelvis Rot Velo Acquire of -36 – 1st percentile

We are able to equally have a look at entrance hip inner rotation positional adjustments and entrance hip inner rotation velo since that captures rotation across the entrance hip that will present extra context with reference to femur positioning than simply world pelvis rotation, however we get equally weak and non-notable outcomes for change in entrance hip IR from BR to FP (r = 0.007 inter- and r = 0.09 intra-athlete) and max hip ir velo from between FP and BR (r = -0.03 inter- and r= 0.01 intra-athlete).

Evaluating Blocks

How ought to we weigh the completely different elements when evaluating blocks provided that there’s some overlap between them?

All that being stated – how ought to we account for these completely different elements when evaluating a block? To reply this query we constructed a a number of regression mannequin predicting velocity taking within the variables from the completely different elements of blocking. This permits us to calculate one of the best linear method for predicting velocity utilizing completely different variables. Thus, it offers a option to calculate how we’d count on completely different variables to contribute to velocity whereas controlling for the opposite enter variables, and due to this fact determine what distinctive data every variable provides.

With Entrance Knee Extension from FP to BR and the COG decel metric correlating essentially the most with velocity on their very own, it’s not stunning that they supplied the most important improve in mannequin explanatory energy. Including entrance knee extension angular velo at BR and the max worth on high of those two didn’t improve efficiency – so evidently the knowledge these would add is already captured in these two preliminary metrics. Equally, we additionally examined out including pelvis rotation associated metrics to see if they might present up as extra notable when controlling for the impact of the opposite elements of blocking, and it nonetheless got here up as not including a lot.

Trying on the high blocks by this mixed metric (hereby dubbed the composite block metric), we see the highest performers are these with essentially the most lead knee extension with some guys getting a bit extra credit score as a result of they decelerate their COG extra successfully, although in addition they straighten their knees decently as nicely.

Prime composite block rating

2nd highest

eighth greatest, which this pitcher achieves by having elite COG decel in addition to good lead knee extension

Floor Response Forces

How do floor response forces relate to these kinematic measures of the block and to velocity?

With the addition of pressure plates to our lab and processing pipeline, we’ve got the flexibility to dissect the lead leg block even additional past what you’ll be able to decide up from video and movement seize – by floor response forces.

Whereas we’ve completed a pair case research earlier than pressure plate information comparable to in these blogs from 2016 and 2017; none of those have anyplace near the pattern of pressure plate information we’ve been capable of acquire with the set-up in our lab now – the place we’ve got greater than 800 distinctive periods with pressure plate information.

lead leg floor response pressure damaged up into X/Y/Z elements for the anterior-posterior/lateral/and vertical elements, we see that the anterior-posterior and vertical elements correlate to velocity with comparable energy (r = 0.38 for x, and r = 0.44 for z) – whereas the y element (going between first and third) doesn’t as strongly (r = 0.19). 

Nonetheless all of those are inflated by the truth that heavier athletes throw more durable throughout the pattern of HS/School/Professional athletes we’ve got right here – in order that confounds the connection noticed right here.

After we management for body-weight, the correlation for all three of the elements drops off some, however the vertical and anterior-posterior elements winds up in an analogous neighborhood to what we noticed for the important thing kinematic measures of the lead leg block (r = 0.19 for x, r = 0.23 for z, r = 0.1 for y – and r = 0.25 for the max magnitude contemplating all three elements). 

An fascinating consequence right here is that the X and Z elements each correlate with comparable energy to velocity – whereas a few of the earlier literature had discovered the X element to matter extra – in smaller samples. If we think about the course of the pressure (the place 90 levels is all vertical pressure, and 0 levels is all horizontal pressure with no vertical element), we see no correlation to velo. That’s, on common there doesn’t appear to be a common suggestion for what angle you need to goal to place pressure into the bottom throughout all athletes, however merely that placing extra pressure into the bottom along with your lead leg is best.

Evaluating the max Lead Leg pressure into the bottom with the Block Composite Rating calculated from the completely different kinematic areas we see that they’re correlated, however that correlation isn’t all that prime in context of what you would possibly count on (r = 0.26). Which is to say that the kinematic measures give us some thought of the pressure put into the bottom, however there’s extra element that we’re capable of get at leveraging the pressure plates that doesn’t present up within the kinematic measures – giving us one other measure software for assessing and diagnosing athlete’s coaching wants.

Positioning

How does touchdown positioning have an effect on this composite block metric and the completely different blocking metrics?

The desk above exhibits the inter-subject (evaluating completely different athletes) and intra-subject (evaluating throws from every athlete) correlations evaluating completely different metrics of curiosity for blocking with foot-plant positioning metrics. Relationships I believe could also be of curiosity highlighted in orange. The relationships between these varied touchdown place metrics and our composite block metric are all very weak – which suggests to me that touchdown place is just not the first determinant of an athlete’s blocking means.

We thought of 4 positional metrics at foot-plant – entrance knee flexion, entrance ankle dorsi/plantar flexion, pelvis rotation, and hip inner/exterior rotation. For every of those, I took a have a look at how they in comparison with ball velo, the composite block metric, detailed above, after which entrance knee extension from FP to BR, entrance knee flexion from FP to the min after FP, COG decel after FP, and Max Entrance Knee Extension Angular Velo which have been the primary metrics mentioned above.

Entrance Knee Flexion at FP

First we think about the angle of the knee at foot-plant, because it’d appear that how this angle is initially set would considerably have an effect on how the block works. Fast visible demonstration of the variability we see:

35° on left (third percentile)                                                                       68° on proper (98th percentile)

Thus a bigger quantity is a extra flexed knee at foot-plant. Many of the relationships come again as non-notable when combining the inter- and intra- athlete evaluation.

The one relationship that’s notable in each is the connection between entrance knee flexion and sinking into extra flexion after foot-plant – we get r = 0.26 evaluating completely different session-level averages per athlete and r = 0.2 evaluating all throws inside every athlete. 

This relationship signifies that having a extra bent knee at foot-plant results in sinking into flexion much less after foot-plant. Which may appear counterintuitive at first, however because the knee is already extra bent, it’s much less more likely to bend much more. Moreover, it’s attainable that the athlete has a specific joint angle that they’re stronger in – so by touchdown in a extra flexed place – that might theoretically be extra advantageous for extending out of.

Entrance Ankle Dorsi-flexion at FP

Entrance ankle dorsi/plantar flexion goes to be decently associated to entrance knee flexion angle (r = 0.40), however I believed it will be fascinating to contemplate as nicely, since they don’t line up 100%.

Ankle dorsiflexion at 59°                                                   Ankle dorsiflexion at 91°

Right here, many of the relationships come again non-notable, so it doesn’t appear to be an enormous determiner of somebody’s means to dam, particularly since there’s no notable correlation to ball velo or the composite block metric.

Pelvis Rotation at FP

After trying on the lead leg positions particularly, we think about pelvis rotation (axially, so omitting anterior/posterior tilt and lateral tilt of the pelvis on this evaluation) subsequent – as if the pelvis is open sufficient is usually thought of a think about blocking means.

A fast visible at excessive and low pelvis rotation numbers for example:

Pelvis Angle at 15°                                                                        Pelvis Angle at 65°

There’s a negligible relationship between pelvis rotation at FP and ball velo (r = 0.08 between-athlete, r = 0.02 within-athlete) and pelvis rotation at FP and the composite block metric (r = -0.04 inter-athlete, and r = 0.03 intra-athlete) – which instantly qualifies the significance of getting the pelvis open at foot-plant for blocking. If getting the pelvis open was a prerequisite for with the ability to block, you’d count on more durable throwers and higher blockers to get their pelvis extra open – which on common they don’t.

We do see that athletes who land with extra open pelvises on common sink much less into flexion after footplant (in addition to intra-subject – the place athletes sink much less into flexion after foot-plant on throws the place their pelvis is extra open). The correlations listed here are the strongest of any of those touchdown place correlations  (r = 0.34 inter-, and r= 0.45 intra-subject). By touchdown with the pelvis extra open, an athlete might keep away from sinking into extra flexion however within the course of additionally scale back the period of time they’ve for his or her leg to impart pressure into the bottom earlier than ball launch – and thus simply be buying and selling off sinking into a bit little bit of flexion on the expense of getting time to place pressure into the bottom.

If somebody is sinking into a whole lot of flexion and never getting any extension, it’s attainable that opening the pelvis extra up might assist, by affording them much less time to take action – however I don’t suppose that totally addresses the difficulty of lack of extension given the dearth of a relationship between pelvis angle and throwing more durable or blocking higher (as measured by the composite block rating)

Hip ER at FP

Final one on the docket is Hip IR/ER. It  is a little more refined when it comes to with the ability to see it than the opposite touchdown place metrics. Now we have a pair athletes with extra excessive values for example:

Low Hip IR/ER at FP of -25°                                            Excessive Hip IR/ER at FP of 46

°

This metric is trying on the rotation of the entrance femur relative to the pelvis. When on the lookout for it, you’ll be able to see the athlete on the left have his femur turned inwards in relation to the pelvis versus the athlete on the fitting who has his turned out.

We see extra Hip ER at FP associated to sinking into extra flexion after FP, and getting much less extension of the knee between FP and BR. From athletes with excessive hip ER values (screenshots beneath) – we are able to see how being extra externally rotated might put an athlete in a disadvantageous place to have the ability to prolong the knee. Nonetheless, as with the opposite touchdown place metrics, Hip ER at FP doesn’t relate notably to throwing more durable or blocking higher typically, so this can be a attainable choice to discover with athletes with excessive ER, however isn’t one thing that essentially weighs closely when evaluating and troubleshooting an athlete’s blocking means.

Conclusion

The flexibility to investigate mechanics from all of the pitchers who’ve come by means of the lab permits us to carefully take a look at out a wide range of hypotheses to find out what distinguishes exhausting throwers from slower throwers. We see our exhausting throwers extending their knees extra and quicker, placing extra pressure into the bottom vertically and horizontally, and slowing their middle of gravity down greater than the slower throwers on common. 

Thus, trying out knee extension offers a useful check-point when contemplating an athlete’s mechanics – which pertains to the athletes means to decelerate their physique and switch that vitality up the chain and put pressure into the bottom. We don’t see the standard of the lead leg block being dictated by the place an athlete lands in – suggesting that the lead leg block is a talent/motion that doubtless must be educated (with drills like rockers, roll-ins and drop-steps) – and received’t essentially tackle itself utterly simply by altering how an athlete strikes into foot-plant.

Whereas we’ve aimed to be thorough right here, there’s at all times extra areas to research. We touched on pressure plate elements on this evaluation, however there’s additional evaluation on the timing of floor response forces and the connection between placing pressure into the bottom and the way that coincides with completely different actions. Moreover that, the function of energy and mobility on blocking means is usually talked about and could be fascinating to debate right here, however that’s an evaluation for one more time.