Back Leg Drive Increases Pitching Velocity And Reduces Risk Of Injury

Understanding how the back leg drive influences the kinetic chain, contributes to velocity and reduces the risk of injury needs to be covered much more in depth. There are still many coaches who don’t believe in teaching the back leg drive in baseball and, in my humble opinion, that is a huge mistake. The back leg drive is one of the most important components in the pitching delivery and it is severely undercoached. The goal of this article will be to shed light on the importance and function of the back leg drive for both pitching velocity and health.

Ground Reaction Forces Power Jumping, Running, Throwing

In jumping, running and throwing the body pushes force into the ground to create movement.  We cannot see force, but we can see the results it produces. A vertical jump is a great example of force. The jumper applies enough force to the ground to overcome his bodyweight, gravity and friction. This excessive force then launches the jumper into the air. Same thing for sprinting. A sprinter pushes force into the ground to accelerate the body forward. The more force that is pushed into the ground the faster they will go. During the stride phase of throwing the back leg is the only leg attached to the ground. It’s role is to push force into the ground to accelerate the pitcher towards the target and power energy through the kinetic chain. The more force you push through the ground, the more potential for throwing velocity and arm health.

The tendency of all pitchers in the study to develop high levels of force in the direction of the pitch, combined with the finding that pitchers who developed the largest forces (normalized to body weight) threw fastest, seems to contradict the theory that pitching is a “controlled fall.” The pitching motion depends on significant contributions from the lower limbs to create forward impetus. The exact contributions of each segment to the pitching motion will require further study using a complex multisegmental dynamic model.

Based on this study, we hypothesize that the push-off forces in the direction of the pitch (AP shear) initiate the forward momentum of the entire body. The greater this magnitude, the more kinetic energy there is in the direction of the pitch. - Characteristic ground-reaction forces in baseball pitching. (2)

Ground reaction forces are important contributors to throwing motion. The proximal to distal (lower to upper extremity) sequential segmental motion allows for maximal force production until ball release. - Stride length: the impact on propulsion and bracing ground reaction force in overhand throwing (6)

Linear And Angular Motion In The Pitching Delivery

Biomechanists often divide movement into three categories: linear, angular and general. Linear motion is an object moving in a straight line. Angular motion is when an object rotates about an axis. General motion occurs when linear motion and angular motion combine. This is an important aspect to understand in the back leg drive as there is both linear and angular motion involved in the movement. Measuring the pitching delivery with motion capture technology allows us to see unique details on how a pitcher transfers energy from the ground, to the hips, trunk and arm. For example, the kinematic sequence looks at the angular velocity of the pelvis, trunk and arm to see how the player is sequencing energy through the kinetic chain. This is important for both velocity and health!

Ball velocity is generated during the overhead baseball pitch via efficient force transmission up the kinetic chain, from the lower body up and outward to the throwing hand. The kinematic sequence, or the sequential timing pattern of peak angular velocities of body segments during a pitch, provides insight to segment position and motion control that drives the kinetic chain. Previous publications report an ideal kinematic sequence (KS) where the timing of each body segment’s peak angular velocity occurs in a proximal-to-distal (PDS) pattern resulting in greater ball velocity and reduction in throwing arm injury risk. - Baseball Pitchers’ Kinematic Sequences and Their Relationship to Elbow and Shoulder Torque Production. (4)

The pelvis is the first link in the kinematic sequence. The higher the angular velocity of the pelvis the greater the potential of the transfer energy through the trunk, arm and finally the ball. Wouldn’t it make sense that the drive leg (the only leg attached to the ground at this point in the pitching delivery) plays a significant role in enhancing linear and angular velocity of the pelvis?

Pitchers also showed an increase in average pelvic angular velocity during the arm cocking phase (FFC to MER) as velocity increased. In accordance with the kinetic link theory and the law of conservation of angular momentum, the increase in average pelvic velocity allows more energy to be transferred to the upper torso, which rotates after the pelvis. The increase in energy transfer to the upper torso was realized as average upper torso velocities increased during the arm acceleration phase (MER to Rel). Theoretically, the increased upper torso velocities allowed more energy to be transferred from the trunk to the throwing arm, and ultimately to the ball, to produce higher ball velocities. - Relationship of pelvis and upper torso kinematics to pitched baseball velocity. (1)

Back Leg Drive Powers Hip To Shoulder Separation

Not only does the back leg drive influence linear/angular velocity of the pelvis and accelerate the body forward, but it also powers hip to shoulder separation. Hip to shoulder separation is commonly accepted in the pitching world as a vital biomechanic component. However, there seems to be a lack of understanding of how the back leg (driving force through the ground) powers the pelvis into an open position. Concentric plantar flexion, knee extension and hip extension of the drive leg aka “triple extension” powers the pelvis open and accelerates the body down the mound. Just as triple extension powers the jumper into the air or accelerates the sprinter out of the blocks. The back leg drive is vital for healthy high velocity throwing. One study found that high velocity pitchers can generate greater hip extension/abduction and knee extension in the drive leg compared to low velocity pitchers (5).

In the pivot leg, joint torques during hip abduction, hip internal rotation, and knee extension were significantly greater in the high velocity group than in the low velocity group (Table 5). Campbell et al. (2010) reported that the gastrocnemius, vastus medialis, gluteus maximus, and biceps femoris of the pivot leg elicited average muscle activity levels of 75, 68, 73, and 48% of their respective maximal voluntary isometric contractions from stride knee peak flexion to stride foot contact, which promoted concentric plantar flexion, knee extension, and hip extension. In the current results, the ankle joint torque was similar between the two groups.

Taking current results into account together with the report of Campbell et al. (2010), it is likely that as compared to low-ball-velocity pitchers, high-ball-velocity pitchers can generate greater momentum by hip extension/abduction and knee extension in the pivot leg for accelerating the body forward. - Kinematic and kinetic profiles of trunk and lower limbs during baseball pitching in collegiate pitchers. (5)

Back Leg Drive Accelerates Body Down The Mound And Increases Stride Length

3rd party research has shown that the back leg drive is responsible for accelerating the pitcher down the mound. This not only increases throwing velocity, but also stride length and perceived velocity. Perceived velocity is essentially a fastball looking faster than it really is because the pitcher is releasing the ball closer to the hitter. That’s a benefit, but the real benefit comes from the more efficient biomechanics of a longer stride that help to keep a pitcher healthy. One study looking at stride length found that increasing stride length may be considered injury protective. It also found that shorter strides created more arm lag, hyperangulation and elbow adduction which are all red flags for injury. Essentially, longer strides incorporate more linear energy through back leg drive, front leg extension and forward trunk tilt which assist in allowing the throwing arm to ride along with the trunk more efficiently. The shorter strides rely on less linear energy and back leg/front leg ground reaction forces. This leads to more angular or rotational energy and the injury prone biomechanics.

The shortened strides exacerbate throwing arm lag and elicit deficient momentum exchanges between the trunk and throwing shoulder which allows for damaging shoulder and elbow joint kinematics and kinetics through repetitive high velocity hyperangulation (Keeley, Oliver, Dougherty, & Torry, 2015; Ramsey & Crotin, 2016). Given greater drive and stride leg braking assists alignment of the throwing arm in the scapular plane of the trunk, increasing stride length may be considered injury protective (Keeley et al., 2015). In contrast, increased propulsion following stride foot contact combined with reduced drive and stride leg braking was evident with shortened strides. - Stride length: the impact on propulsion and bracing ground reaction force in overhand throwing (6)

Back Leg Drive Decreases The Risk Of Injury

csm_vertical-jump-test_2f999733b4.jpg

A longer stride can be considered injury protective if it is coming from an explosive back leg drive. A pitcher can lengthen his stride by letting his front leg swing open. This would be him relying more on momentum to increase stride length rather than his back leg creating a powerful triple extension to accelerate the body. Sparta Science, a company out of the Bay Area, uses force plates to test and assess athletes. They found that force plate metrics can predict players that are susceptible to elbow injury. Basically, in testing counter movement jump they found that players who utilize more momentum as opposed to explosive strength in a jump were more prone to elbow injury. My hypothesis would be that pitchers who rely more on momentum as opposed to explosive strength in their back leg drive are more susceptible to arm injury.

This study demonstrates that elbow injuries are more likely to occur with athletes that rely on momentum as impulse is defined as the change in momentum. This hypothesis is further strengthened by the negative significant relationship of vertical jump; if the athlete jumps higher and uses more impulse they achieved this greater result by utilizing more momentum rather than explosive strength reflected by the other force plate variables which are divided by time rather than multiplied. Therefore, this testing indicates that players susceptible to elbow injury based on force plate metrics can be predicted. - Force Plate Metrics Predictive of UCL Injuries (10)

Summary

The back leg drive increases pitching velocity and reduces the risk of injury. Ground reaction forces power jumping, running and throwing. The back leg drive pushes force into the ground through concentric plantar flexion, knee extension and hip extension (triple extension) to accelerate the body. This influences the linear and angular motion in the pitching delivery. It also increases stride length and powers the pelvis open to enhance hip to shoulder separation. Pitchers need to build their training programs around developing the leg power, mobility and biomechanics to efficiently use their kinetic chain in a proximal to distal fashion. This is the most efficient way to train pitching velocity while simultaneously reducing the risk of injury.

If you want to learn more please follow us on social media (Twitter, Instagram, Facebook,) @stevenguadagni (Youtube) @5toolsportsscience and feel free to send in video of your pitching or hitting mechanics for a free analysis. If you want to train with us we have several options. Come down for Long Term Training at our facility, Remote 1 on 1 Online Training from home or The 5 Tool Prospect Manual and Nutrition Manual. Learn how to optimize your mechanics and perform at the highest level possible! Hope you guys enjoyed the article. Please don’t hesitate to reach out if you have any questions.

References

  1. Stodden, David F., et al. "Relationship of pelvis and upper torso kinematics to pitched baseball velocity." Journal of applied biomechanics 17.2 (2001): 164-172.

  2. MacWilliams, Bruce A., et al. "Characteristic ground-reaction forces in baseball pitching." The American journal of sports medicine 26.1 (1998): 66-71.

  3. Campbell B.M., Stodden D.F., Nixon M.K. (2010) Lower extremity muscle activation during baseball pitching. Journal of Strength and Conditioning Research 24(4) 964-971.

  4. Scarborough, Donna Moxley, et al. "Baseball Pitchers’ Kinematic Sequences and Their Relationship to Elbow and Shoulder Torque Production." Orthopaedic Journal of Sports Medicine 7.7_suppl5 (2019): 2325967119S00429.

  5. Kageyama, Masahiro, et al. "Kinematic and kinetic profiles of trunk and lower limbs during baseball pitching in collegiate pitchers." Journal of sports science & medicine 13.4 (2014): 742.

  6. Ramsey, Dan K., and Ryan L. Crotin. "Stride length: the impact on propulsion and bracing ground reaction force in overhand throwing." Sports biomechanics 18.5 (2019): 553-570.

  7. Ramsey, D. K., & Crotin, R. L. (2016). Effect of stride length on overarm throwing delivery: Part II: An angular momentum response. Human Movement Science, 46, 30–38. doi:10.1016/j. humov.2015.11.021.

  8. Ramsey, D. K., Crotin, R. L., & White, S. (2014). Effect of stride length on overarm throwing delivery: A linear momentum response. Human Movement Science, 38, 185–196. doi:10.1016/j. humov.2014.08.012.

  9. Keeley, D. W., Oliver, G. D., Dougherty, C. P., & Torry, M. R. (2015). Lower body predictors of glenohumeral compressive force in high school baseball pitchers. Journal of Applied Biomechanics, 31, 181–188. doi:10.1123/jab.2011-0229

  10. Hawkins, Steadman. “Force Plate Metrics Predictive of UCL Injuries.” Force Plate Metrics Predictive of UCL Injuries - Sparta Science, 2015, www.spartascience.com/resources/force-plate-metrics-predictive-of-ucl-injuries.

steven guadagnibaseball training, baseball, pitching drills, pitch faster, pitching mechanics, pitching, pitching injury, improve pitching mechanics, arm pain, back leg drive, 90 mph, throw harder, how to throw harder