Changes in Youth Baseball Pitching Biomechanics: A 7-Year Longitudinal Study.

BACKGROUND: Pitching biomechanics are associated with performance and risk of injury in baseball. Previous studies have identified biomechanical differences between youth and adult pitchers but have not investigated changes within individual young pitchers as they mature. HYPOTHESIS: Pitching kinematics and kinetics will change significantly during a youth pitcher's career. STUDY DESIGN: Descriptive laboratory study. METHODS: Pitching biomechanics were captured in an indoor laboratory with a 12-camera, 240-Hz motion analysis system for 51 youth pitchers who were in their first season of organized baseball with pitching. Each participant was retested annually for the next 6 years or until he was no longer pitching. Thirty kinematic and kinetic parameters were computed and averaged for 10 fastballs thrown by each player. Data were statistically analyzed for the 35 participants who were tested at least 3 times. Within-participant changes for each kinematic and kinetic parameter were tested by use of a mixed linear model with random effects ( P < .05). Least squares means for sequential ages were compared via Tukey's honestly significant difference test ( P < .05). RESULTS: Three kinematic parameters that occur at the instant of foot contact-stride length, lead foot placement to the closed side, and trunk separation-increased with age. With age, shoulder external rotation at foot contact decreased while maximum shoulder external rotation increased. Shoulder and elbow forces and torques increased significantly with age. Year-to-year changes were most significant between 9 and 13 years of age for kinematics and between 13 and 15 years for normalized kinetics (ie, scaled by bodyweight and height). CONCLUSION: During their first few years, youth pitchers improve their kinematics. Elbow and shoulder kinetics increase with time, particularly after age 13. Thus, prepubescent pitchers may work with their coaches to improve the motions and flexibility of the players' bodies and the paths of their arms. Once proper mechanics are developed, adolescent pitchers can focus more on improving strength and power.

Long-term Outcomes After Ulnar Collateral Ligament Reconstruction in Competitive Baseball Players: Minimum 10-Year Follow-up.

BACKGROUND: Ulnar collateral ligament reconstruction (UCLR) has afforded baseball players with excellent results; however, previous studies have described only short-term outcomes. PURPOSE: To evaluate long-term outcomes after UCLR in baseball players. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: All UCLRs performed on competitive baseball players with a minimum 10-year follow-up were identified. Surgical data were collected prospectively and patients were surveyed by telephone follow-up, during which scoring systems were used to assess baseball career and post-baseball career outcomes. RESULTS: Of 313 patients, 256 (82%) were contacted at an average of 12.6 years; 83% of these baseball players (90% pitchers) were able to return to the same or higher level of competition in less than 1 year, but results varied according to preoperative level of play. Baseball career longevity was 3.6 years in general and 2.9 years at the same or higher level of play, but major and minor league players returned for longer than did collegiate and high school players after surgery (P < .001). Baseball retirement typically occurred for reasons other than elbow problems (86%). Many players had shoulder problems (34%) or surgery (25%) during their baseball career, and these occurrences most often resulted in retirement attributable to shoulder problems (P < .001). For post-baseball career outcomes, 92% of patients were able to throw without pain, and 98% were still able to participate in throwing at least on a recreational level. The 10-year minimum follow-up scores (mean ± standard deviation) for the Disabilities of the Arm, Shoulder and Hand (DASH), DASH work module, and DASH sports module were 0.80 ± 4.43, 1.10 ± 6.90, and 2.88 ± 11.91, respectively. Overall, 93% of patients were satisfied, with few reports of persistent elbow pain (3%) or limitation of function (5%). CONCLUSION: Long-term follow-up of UCLRs in baseball players indicates that most patients were satisfied, with few reports of persistent elbow pain or limitation of function. During their baseball career, most of these athletes were able to return to the same or higher level of competition in less than 1 year, with acceptable career longevity and retirement typically for reasons other than the elbow. According to a standardized disability and outcome scale, patients also had excellent results after UCLR during daily, work, and sporting activities.

Trunk axial rotation in baseball pitching and batting.

The purpose of this study was to quantify trunk axial rotation and angular acceleration in pitching and batting of elite baseball players. Healthy professional baseball pitchers (n = 40) and batters (n = 40) were studied. Reflective markers attached to each athlete were tracked at 240 Hz with an eight-camera automated digitizing system. Trunk axial rotation was computed as the angle between the pelvis and the upper trunk in the transverse plane. Trunk angular acceleration was the second derivative of axial rotation. Maximum trunk axial rotation (55 +/- 6 degrees) and angular acceleration (11,600 +/- 3,100 degrees/s2) in pitching occurred before ball release, approximately at the instant the front foot landed. Maximum trunk axial rotation (46 +/- 9 degrees) and angular acceleration (7,200 +/- 2,800 degrees/s2) in batting occurred in the follow-through after ball contact. Thus, the most demanding instant for the trunk and spine was near front foot contact for pitching and after ball contact for batting.

Kinematic changes using weightlifting shoes on barbell back squat.

The purpose of this study was to validate a higher degree of foot segment angle by wearing the weightlifting (WL) shoes and to determine the kinematic differences between WL shoes and running shoes during the barbell back squat. College-aged individuals volunteered to participate in this study (N = 25). After warm-up, subjects performed 60% of 1RM barbell back squat. Reflective markers were placed on lower extremity joints and end of the bar to create segments to analyze kinematics of the barbell back squat from a 2-dimensional view. Three separate repeated measure analyses of variance were used at p = 0.05. Results showed that there was a difference between the footwear conditions; foot segment angle of 3.5° (p < 0.05) and trunk lean of 22 mm (p < 0.05) were captured when wearing WL shoes. However, thigh segment peak flexion angle was not statistically different (p = 0.37). Wearing WL shoes seems to be beneficial in reducing the overall trunk lean, because this position is believed to reduce the amount of shear stress in the lower back area. Back squat with WL shoes also increased foot segment angle and possibly contributes to greater muscle excitation in knee extensors. Weightlifting shoes did not help reach thigh segment closer to horizontal as compared with the running shoe condition. It is recommended that WL shoes be used by those who are prone to displaying a forward trunk lean and who aim to increase knee extensor activation.

Biomechanical comparison of baseball pitching and long-toss: implications for training and rehabilitation.

STUDY DESIGN: Controlled laboratory study. OBJECTIVES: To test for kinematic and kinetic differences between baseball pitching from a mound and long-toss on flat ground. BACKGROUND: Long-toss throws from flat ground are commonly used by baseball pitchers for rehabilitation, conditioning, and training. However, there is controversy over the biomechanics and functionality of such throws. METHODS: Seventeen healthy, college baseball pitchers pitched fastballs 18.4 m from a mound to a strike zone, and threw 37 m, 55 m, and maximum distance from flat ground. For the 37-m and 55-m throws, participants were instructed to throw "hard, on a horizontal line." For the maximum-distance throw, no constraint on trajectory was given. Kinematics and kinetics were measured with a 3-dimensional, automated motion analysis system. Repeated-measures analyses of variance, with post hoc paired t tests, were used to compare the 4 throw types within pitchers. RESULTS: At foot contact, the participant's shoulder line was nearly horizontal when pitching from a mound and became progressively more inclined as throwing distance increased. At arm cocking, the greatest amount of shoulder external rotation (mean ± SD, 180° ± 11°), elbow flexion (109° ± 10°), shoulder internal rotation torque (101 ± 17 Nm), and elbow varus torque (100 ± 18 Nm) were measured during the maximum-distance throws. Elbow extension velocity was also greatest for the maximum-distance throws (2573°/s ± 203°/s). Forward trunk tilt at the instant of ball release decreased as throwing distance increased. CONCLUSION: Hard, horizontal, flat-ground throws have biomechanical patterns similar to those of pitching and are, therefore, reasonable exercises for pitchers. However, maximum-distance throws produce increased torques and changes in kinematics. Caution is, therefore, advised in the use of these throws for rehabilitation and training.

The effect of pitch type on ground reaction forces in the baseball swing.

Coaches have identified the batter's weight shift as a critical component for promoting proper timing and balance in a baseball swing. Analysing the weight shift through maximum horizontal (Fx) and vertical (Fz) ground reaction forces (GRFs) of professional batters (N = 29; height = 185 +/- 6 cm; mass = 92 +/- 9 kg), the purpose of this study was to compare GRFs among swings against fastballs and changeups. General linear models were used to compare three conditions of interest: successful results against fastballs, successful results against changeups, and unsuccessful results against changeups. Batters had a similar loading mechanism and initial weight transfer from back foot to front foot regardless of pitch type, but peak front foot GRFx and GRFz occurred with significantly different magnitudes and at significantly different times, depending on the pitch type and hit result. Peak front foot GRFs were greater for successful swings against fastballs compared to both successful and unsuccessful swings against changeups. Peak front foot GRFs of unsuccessful swings against changeups occurred, on average, 15-20 ms earlier than successful swings against changeups and 30-35 ms earlier than successful swings against fastballs, quantifying how a changeup can disrupt the coordination of a hitter's weight shift.

Effects of the bench shirt on sagittal bar path.

Powerlifting, like many sports, uses specialized equipment to enhance performance and decrease the chance of injury. The purpose of this exploratory study was to determine whether wearing a bench press shirt would alter the natural mechanics of the bench press, causing a more efficient lift when pressing the same weight as without the bench shirt. Participants (n = 5) completed 2 series of 1-repetition maximum (1RM) bench press tests, with 1 week of rest in between 1 series without the bench shirt (no-shirt), and 1 series with a bench shirt (bench shirt). Results revealed that the vertical bar path ranges were significantly less in the bench shirt condition (35.7 +/- 4.8 cm) compared with the no-shirt condition (40.2 +/- 7.0 cm) (p < 0.05). Significant differences were found between the bar's optimal (81.4 +/- 14.2 cm) and observed (96.7 +/- 19.1 cm) total distances traveled in the no-shirt condition (p < 0.01), but no significant differences were found between the bar's optimal (71.6 +/- 12.7 cm) and observed (86.3 +/- 10.5 cm) total distances traveled in the bench shirt condition. These findings suggest that the bar path in bench shirt trials is more efficient and consistent than in the no-shirt trials. This pattern demonstrates that a bench shirt can improve load capacity. It is also possible that the bench shirt decreases the forces that act on the shoulder for a given weight and, thus, may decrease the risk of injury.

Baseball pitching biomechanics in relation to injury risk and performance.

CONTEXT: Baseball pitching kinematics, kinetics, ball velocity, and injuries at the shoulder and elbow are related. EVIDENCE ACQUISITION: PubMed and Sport Discus were searched for original studies published between 1994 and 2008. Relevant references in these studies were retrieved. Inferential studies that tested relationships between kinematics and kinetics were included, as were studies that tested relationships between kinematics and ball velocity. Descriptive studies that simply quantified kinematics and/or kinetics were excluded. RESULTS: SEVERAL KINEMATIC PARAMETERS AT THE INSTANT OF FOOT CONTACT WERE ASSOCIATED WITH INCREASED UPPER EXTREMITY KINETICS: front foot position, front foot orientation, shoulder abduction, and shoulder horizontal adduction. The timing of shoulder external rotation, pelvis rotation, and upper trunk rotation was associated with increased kinetics and decreased ball velocity. Low braking force of the lead leg and a short stride were associated with decreased ball velocity. Decreased maximum shoulder external rotation, shoulder abduction, knee extension, and trunk tilt were also associated with decreased ball velocity. As pitchers develop, kinematic values remain similar, their variability reduces, and kinetic values gradually increase. Slight kinematic variations were seen among pitch types, although the kinetics of fastballs and curveballs were relatively the same; changeup kinetics were the lowest. As pitchers fatigued, kinetic values remained constant, but increases in arm pain were reported. CONCLUSIONS: Several kinematic parameters were related to joint kinetics and ball velocity. To enhance performance and reduce injury risk, pitchers need to learn proper fastball mechanics at an early age. A changeup is recommended as a safe secondary pitch to complement the fastball; the curveball can be added after fastball and changeup mechanics are mastered. Avoiding overuse and pitching while fatigued is necessary to minimize the risk of arm injury.

The biomechanics of situational baseball: execution and perception of left-handed pitchers' simulated pick-off moves to first base.

The aim of this study was to provide an in-depth analysis of the pick-off play in baseball. Ten collegiate left-handed pitchers and nine base-runners participated in this study. The pitchers were videotaped with four cameras to derive three-dimensional data while performing deliveries in the directions of first base and home plate in a laboratory setting. Deliveries were performed from flat ground. Differences between these deliveries were measured through ten selected joint and segment angles. The base-runners completed two distinct procedures in which they viewed video footage of left-handed pitchers and estimated the intended delivery direction. Base-runners were subsequently interviewed to determine the reasoning behind their decisions. The pitchers' data revealed differences between delivery types in nearly all of the selected angles (P < 0.01). The base-runners' data demonstrated that their ability to discriminate delivery types improved when allowed more viewing time per trial (P < 0.01). Additionally, commonalities exist among the base-runners' focal points on the pitcher while making decisions regarding delivery direction and the kinematic differences between deliveries in left-handed pitchers. The practical significance of these results, however, may be more difficult to interpret.