Author : Ryan Lewis Crotin
Publisher :
ISBN 13 :
Total Pages : 294 pages
Book Rating : 4.:/5 (859 download)
Book Synopsis A Kinematic and Kinetic Comparison of Baseball Pitching Mechanics Influenced by Stride Length by : Ryan Lewis Crotin
Download or read book A Kinematic and Kinetic Comparison of Baseball Pitching Mechanics Influenced by Stride Length written by Ryan Lewis Crotin and published by . This book was released on 2013 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current workload metrics and ball velocity records have been dubious in identifying clear overuse mechanisms of injury, raising greater interest in pathomechanics research, where most work has been focused on the critical instant, spanning the throwing arm's acceleration and deceleration phases. Since throwing arm kinematics and kinetics are lowest from the onset of the pitching delivery, the majority of research neglects biomechanical interactions occurring before stride foot contact (SFC). In light of this, the current dissertation established a new framework of study, examining stride length effects on baseball pitching performance, where lower extremity joint dynamics from the onset of the delivery through to ball release, ground reaction force profiles, as well as global pelvic and trunk kinematics are anticipated to be affected by altered propulsion and bracing biomechanics. The dissertation investigated the effect of stride length through seven studies. To determine an overall representation of stride length impacts on the kinetic chain and temporal events, linear and angular momentum analyses were performed for the total body and throwing arm. Trunk-throwing arm momentum exchanges were represented by momentum compensation ratios to identify the proportion of the throwing arm to the total body momentum (contributed mostly by the trunk). In the results, stride length affected the instant of SFC, as longer strides increased single support generation and abbreviated the duration of the brace-transfer phase. Momentum relationships most consequential to phase time affects entailed greater leading axis momentum for pitchers with longer strides, while greater transverse momentum later in the pitching delivery was seen with shorter strides, which had been considered compensatory for reduced propulsion prior to SFC. The second study differentiated propulsion and bracing ground reaction force profiles, as vertical weighting, anterior-shear forces and their normalized impulses were greater for longer strides prior to SFC, while thereafter, the drive foot applied braking forces in tandem with the stride leg. Shorter strides minimized drive foot posterior-shear force, maintained propulsion after SFC in double support, and applied peak vertical weighting of the stride leg near ball release. Affected ankle dynamics were featured in the third study, which related to the aforementioned differences in ground reaction force profiles. Longer stride's drive ankle applied greater propulsion dynamics prior to SFC with closed-chain dorsiflexor moments thereafter to assist braking and landed the stride foot with greater heel-strike.^Shorter strides maintained drive ankle propulsion dynamics after SFC, minimized hind ankle braking, landed more in toe-strike, and required greater stride ankle braking dynamics during acceleration. Bilateral knee flexion-extension dynamics were investigated in succession where greater propulsive dynamics during generation and greater hind leg extension kinetics were found with longer strides, believed to increase inertial and frictional effects in braking effects. Maintained propulsion after SFC, greater stride knee flexion and extension power occurred with shorter strides. In the fifth study, femoral-acetabular hip dynamics revealed greater internal rotation and abduction, which facilitated greater maximum drive hip kinetics in extension prior to SFC with longer strides. Following SFC, longer strides generated greater stride hip extension power in braking and eccentrically slowed internal rotation in greater stride hip flexion. Longer strides improved stride hip biomechanics to better moderate internal pelvic rotation toward home plate and added stability, throwing from a lowered position within a wider base of support. Shorter strides revealed greater stride hip extension, believed to elevate the center of mass within a narrower base of support, reducing stability to most likely minimized braking to maintain drive hip propulsion kinetics and expedite internal pelvic rotation in double support after SFC. The sixth study, proximal segment kinematics were examined as longer strides anterior pelvic rotation, forward trunk flexion, upward pelvic rotation, non-dominant trunk bending, as well as internal rotation kinematics of the trunk and pelvis were greater prior to SFC. Thereafter, the kinematics mentioned above were greater for shorter strides. Lastly, pelvic-trunk separation angles and proximal plyometric effects denoted stride length influences upon the transverse pelvic-trunk rotational couple.^Greater separation occurred prior to SFC with longer strides with peak separation found shortly thereafter. Shorter strides further counter-rotated the pelvis away from home plate at the onset of the pitching delivery and also coordinated peak separation later in the delivery near the acceleration phase, producing greater proximal plyometric effects at BR, evidenced by a 3. 3-fold faster internal rotation velocity of the trunk than that of the pelvis. Our exploration drew several overall conclusions: 1) Stride length is critical to event timing between the onset of delivery and the beginning of brace-transfer phase, 2) Longer strides increase drive leg propulsion dynamics prior to SFC and initiates tandem braking effects (drive and stride leg braking dynamics) thereafter in slowing trunk angular momentum prior to the critical instant, 3) Pitchers with longer strides tend to release each pitch in greater double support (greater drive and stride foot weighting into the ground), 4) Shorter strides maintain propulsion in double support following SFC, minimizing drive leg braking, delaying stride leg braking and increasing transverse trunk momentum prior to the critical instant, and 5) Shorter strides have a greater tendency to be pathomechanic, as elevated internal rotation velocities of the trunk near the critical instant appear to disrupt transverse momentum transfer to the throwing arm. Performance outcomes were found statistically equivalent between conditions suggesting that stride length and accompanied biomechanics can be highly variable in skilled pitchers without impacting competitive performance. Since most stride lengths are attained through maintenance of peak ball velocity, many desired strides may be flawed, susceptible to exertion, and encourage throwing arm pathologies. This work draws attention to the need for further work exploring stride length optimization, intimating a rationale that adjusting stride length as a percentage of body height mitigates undesired lower extremity, pelvic, and trunk biomechanics through appropriating propulsion and bracing dynamics.
