The Stride Leg

Here we go with a geeky blog post about throwing mechanics.  As you may or may not know I am in the midst of doing some research for my master’s degree where I am looking at the correlation of various lower body power tests and throwing velocity.  As a result I am reading a lot about what the legs do during the act of throwing a baseball.  Today I am taking a more in-depth look at the stride leg.

If you like this post you might like my post of the ground reaction forces of pitching where I discuss the trail leg in more detail.

https://lehmansbaseball.wordpress.com/2010/12/20/ground-reaction-forces-of-pitching/

Here we go.

Proper lead leg positioning at foot plant allows for optimal rotation of the hips, pelvis and trunk (Dillman, Fliesig, Andrews – 1993) which is crucial to provide the most effective transfer of energy through the kinetic chain.

The strength of the front leg is an important factor in creating optimal throwing velocity.  Matsuo et al. (2001) demonstrated this when they measured 12 kinematic and 9 temporal parameters between high velocity and low velocity pitchers and found that the amount of flexion and extension of the front knee was significantly different between the two groups.

Matsuo et al (2001) identified four common knee movement patterns with their subjects.  Eighty three percent of the high velocity versus 35% of the low velocity throwing group was classified as displaying either the “A” or “B” patterns which displayed more knee extension than the “C” or “D” patterns.  Sixty nine percent of the high velocity group was categorized in the “A” pattern which showed small amounts of both knee flexion and extension (50-60 degrees) during the initial 60% of the time interval between front foot contact (0%) and instant of ball release (100%).  From the 60% to the 100% interval time mark the knee extended from approximately 55 to 30 degrees.  Only 9% of the low velocity group was classified as having the “A” pattern.  At the other end of the spectrum is the “D” pattern where the front knee continued to flex from approximately 20 to 50 degrees throughout the entire pitching motion 0-100% time interval.  Seventeen percent of the low velocity group demonstrated the “D” pattern while none of the high velocity group fell into this category.

“A” & “B” knee movement – more extension = faster baseball

“C” & “D” knee movement – more flexion = slower baseball

This supports the data presented by Escamilla et al (1998) which reported that collegiate pitchers demonstrated knee extension just prior to maximum external rotation of the glenohurmeral joint during a fastball pitch.  The front knee continued to extend throughout the throwing motion as the trunk moves forward and rotates towards the intended target during which time the arm accelerates.  This ability to brace the front knee allowing for optimal forward trunk tilt and rotation was identified as a characteristic of high velocity pitchers by Elliott et al. (1998).

Prime example of knee flexion into extension

Similar knee movement patterns are also seen in elite level javelin throwers who display the ability to produce a clear double flexion extension pattern which is seen in the “A” pattern in the Matsuo et al.(2001) study.  During the javelin throw the role of the front knee is to brace the body in order to aid in the transfer of energy from the ground up the kinetic chain to the trunk and upper extremity which are accelerating forward. (Whiting et al 1991)

High velocity cricket bowlers have also been shown to exhibit similar front knee movement patterns.  Wormgoor et al. (2010) demonstrated that greater front knee extension at ball release was the biomechanical factor that correlated the highest with throwing velocity.

Ground Reaction Forces

After front foot contact the lead foot applies a braking force in order to slow down the forward momentum and begin to transfer the kinetic energy back and up the kinetic chain.  When the arm is in maximal external rotation the front leg applies approximately 1.5 times body weight while also applying braking forces of nearly 0.75 times body weight.  (MacWilliams et al. 1998)

Max External Rotation – point of max ground reaction force from the stride leg

This study also reported that high wrist velocity was highly correlated with both landing anterior shear force “braking”(r2=0.70) and landing resultant force (r2=0.88) at the point of ball release.  Basically the more force exerted by the front leg translated into higher throwing velocities.

Muscle Activation

Campbell et al. (2010) reported high levels of EMG activity in the stride leg that exceed 100% of MVIC with the high values seen during the arm cocking (phase 3) and acceleration (phase 4).  During the arm cocking phase the Gastrocnemius, Vastus Medialis, Rectus Femoris, Gluteus Maximus and Bicep Femoris produced mean values of 140, 166, 167, 108 and 99% of MVIC respectively.

Pitching Phases – Fleisig et al. 1996

During the arm acceleration phase the Gastroc, VM, RF, GM and BF produced mean values of 126, 89, 47, 170 and 125 of MVIC respectively.   The stride leg functions to dynamically stabilize the hip and knee joints in a single leg stance to maintain standing posture for the trunk and upper extremity to pivot about in order to produce an efficient follow through.

Like I said this was going to be a geeky read but if you made it this far I thank you for your time.  I am putting a big push on this thesis of mine so if you liked this kind of blog post there will be more to follow.

Graeme Lehman

Advertisements

8 comments

  1. adrian

    I enjoyed the article very much but I have seen comments before about front knee extension putting large amounts of strain on the lead hip joint and increasing the chance of injury to that hip. Do you have any research on injury frequency of pitchers who pitch with the type “a” knee flexion/extension pattern?

    Also do knee extension patterns influence loads on shoulder and elbow joints or are the unrelated?

    P.S. Hope to see you at the Cannons practices soon.

  2. Michael Yessis

    Some good information here.

    Probably an oversight but because you used it more than once, I recommend you check your spelling on breaking forces.

    I question your statement that the stride leg extension allows for transfer of the forces from the leg up in a kinetic chain. Shouldn’t it be transfer of the forces of the upper body into the ball (javelin)? In essence, is it not a forward transfer of kinetic forces as opposed to a vertical?

    • Graeme Lehman

      Dr Yessis,
      First of all I am very humbled that you would read some of my work and I am honored that you like some of the information that I have written.
      In regards to the “braking” vs. “breaking”. It was an oversight on my part – in fact my supervisor, Dr. Behm, commented on this same point during the initial reviewing stages of my thesis.

      In my opinon the leg extension of the front leg allows for an optimal transfer of energy created by the lower body – namely the momentum created by the back leg in the frontal plane. This energy is then coupled with the energy created by the upper body (torso rotation, internal shoulder rotation, elbow extnesion) which is then ultimately transfered to the ball/javelin.
      The front leg acts as a stable platform to allow the maximal amount of energy to be transfered without any energy “leaking”. I recently heard the analogy of a sling shot in regards to the front leg. The front leg acts as a the frame and the arm of the user. If these are not strong the elastic component of the sling shot cannot create transfer energy to the implement being shot. This is how I have been teaching the importance of front leg strength to my baseball players and it seems to resonate with them.
      Thanks again for reading.
      Graeme Lehman

  3. Pingback: The Big League Athlete Combine – How to Better Test for Baseball Playing Ability | Lehman's Baseball
  4. Don Ervin

    This is a nice informative site with good questions to talk about.
    Dr. Flesig has as others do when diagramming pitchers initial body movements when exiting the rubber, they omit the initial hip movement following the knee lift, there should be a photo in between the 2nd and 3rd photo showing the hip moving at the peak of the knee lift without any stopping or hesitation then as the hips move to their maximum distance the stride foot and leg then follow and execute their proper body height matching stride length movement.
    First things first. {The first initial, body movement when exiting the rubber} is the {“HIPS”.}
    Before talking about either the stride foot and leg and the ground force action of the rear drive foot and leg I find it most important to talk about how momentum and power are generated prior to these foot and leg actions to enable them to function properly.
    The first body movement of virtually every pitcher observed nowadays whether it be major league or amateur the stride foot and leg are the first body movements executed.
    The {Hips} must lead the way, the {HIPS} must be the first body movement executed when exiting, accelerating away from the rubber, The stride foot and leg must follow the hips through weight shift and on to a proper decelerated stride foot touch stabilized plant down followed by hip to shoulder separation, followed by an externally rotated laid back to internally rotated extended throwing arm to ball release and a nice final flat back follow through position, remember we must learn how to get the body to do the physical work instead of just the arm.
    Dr. Andrews, his associates and several other experts have brought to the baseball communities table that the pitchers body in movement, motion from the rubber to it’s final flat back finish position should operate,function within a series of sequenced chained reactive body movements to be executed at the proper time in their proper sequence.
    Great Base Ball-N
    Don Ervin
    dfervin32@yahoo.com

  5. Don Ervin

    Hey Graeme,
    Keep your great informative baseball comments coming, you are really bringing great knowledgeable baseball information to the baseball communities table, now if people in general would come out of their old conventional wisdom’s, opinionated boxes and learn to teach pitching in particular the way it should be executed the body would execute most of the physical action instead of the arm which would in turn minimize the possibility of serious elbow and shoulder problems leading to surgery.
    We desperately need experts of your status and knowledge here in Springfield, Mo. to educate people on these very important finer points of individual pitching skills that you talk about.

  6. Don Ervin

    Graeme,
    I am very anxious to hear back from you concerning my former comments on the pitching sequence photo’s displayed above which show the first body movement after knee lift peak to be the stride foot and leg instead of the hips.
    Don Ervin
    dfervin32@yahoo.com

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s