Lead Leg Research Articles

Machine learning and statistical prediction of fastball velocity with biomechanical predictors

In recent years, one of the most important factors for success among baseball pitchers is fastball velocity. The purpose of this study was to (1) to develop statistical and machine learning models of fastball velocity, (2) to identify the strongest predictors of fastball velocity, and (3) to compare the models' prediction performances. Three dimensional biomechanical analyses were performed on high school (n = 165) and college (n = 62) baseball pitchers. A total of 16 kinetic and kinematic predictors from the entire pitching sequence were included in regression and machine learning models. All models were internally validated through ten-fold cross-validation. Model performance was evaluated through root mean square error (RMSE) and calibration with 95% confidence intervals. Gradient boosting machines demonstrated the best prediction performance [RMSE: 0.34; Calibration: 1.00 (95% CI: 0.999, 1.001)], while regression demonstrated the greatest prediction error [RMSE: 2.49; Calibration: 1.00 (95% CI: 0.85, 1.15)]. Maximum elbow extension velocity (relative influence: 19.3%), maximum humeral rotation velocity (9.6%), maximum lead leg ground reaction force resultant (9.1%), trunk forward flexion at release (7.9%), time difference of maximum pelvis rotation velocity and maximum trunk rotation velocity (7.8%) demonstrated the greatest influence on pitch velocity. Gradient boosting machines demonstrated better calibration and reduced RMSE compared to regression. The influence of lead leg ground reaction force resultant and trunk and arm kinematics on pitch velocity demonstrates the interdependent relationship of the entire kinetic chain during the pitching motion. Coaches, players, and performance professionals should focus on the identified metrics when designing pitch velocity improvement programs.

Dynamic Balance is Similar Between Lower Extremities in Elite Fencers.

BackgroundFew studies have quantified dynamic balance in fencers despite previous suggestions that balance training may be beneficial for these athletes. Generally, asymmetry in dynamic balance performance between the left and right legs can be an indicator of lower extremity injury risk and used to monitor rehabilitation progress. Fencing is recognized as an asymmetric sport, therefore, differences in dynamic balance may exist among uninjured athletes.Hypothesis/PurposeThe primary objective of this investigation was to evaluate whether asymmetry of dynamic balance is present in uninjured national-level fencers. It was hypothesized that elite uninjured fencers would demonstrate superior dynamic balance on the lead-leg of their fencing stance. A secondary objective was to compare dynamic balance performance of elite fencers to previously published data from high-level athletes participating in other sports.Study DesignDescriptive Laboratory StudyMethodsFourteen uninjured elite competitive fencers were recruited. Subjects self-reported the lead leg of their fencing stance. Each participant performed the Y-Balance test (YBT), which represented a measurement of dynamic balance control, on both legs. Reach distances were recorded directly from a commercially available YBT apparatus. Four reach distances were recorded: anterior, posteromedial, posterolateral, and a composite measure was calculated. Distances were leg length-normalized and expressed as a percentage. Sample averages and standard deviations were derived for the four YBT measurements.ResultsThere were no significant differences in reaching distance between the lead and trail legs in any of the four YBT measures (p ≥ 0.65). Fencers appeared to demonstrate larger normalized reach distances in the posterolateral and posteromedial directions than other athletes.ConclusionsThe results of this study indicate that dynamic balance is not significantly different between the lead and trail legs in elite fencers, despite the asymmetrical nature of their sport. The apparent symmetry of dynamic balance control in uninjured fencers means that the YBT could be used in this population for monitoring progress during training and rehabilitation.Level of Evidence2b

Variability in the Center of Mass State During Initiation of Accurate Forward Step Aimed at Targets of Different Sizes

Motor control for forward step initiation begins with anticipatory postural adjustments (APAs). During APAs, the central nervous system controls the center of pressure (CoP) to generate an appropriate center of mass (CoM) position and velocity for various task requirements. In this study, we investigated the effect of required stepping accuracy on the CoM and CoP parameters during APA for a step initiation task. Sixteen healthy young participants stepped forward onto the targets on the ground as soon as and as fast as possible in response to visual stimuli. Two target sizes (small: 2 cm square and large: 10 cm square) and two target distances (short: 20% and long: 40% of the body height) were tested. CoP displacement during the APA and the CoM position, velocity, and extrapolated CoM at the timing of the takeoff of the lead leg were compared among the conditions. In the small condition, comparing with the large condition, the CoM position was set closer to the stance limb side during the APA, which was confirmed by the location of the extrapolated center of mass at the instance of the takeoff of the lead leg [small: 0.09 ± 0.01 m, large: 0.06 ± 0.01 m, mean and standard deviation, F(1, 15) = 96.46, p < 0.001, η2 = 0.87]. The variability in the mediolateral extrapolated center of mass location was smaller in the small target condition than large target condition when the target distance was long [small: 0.010 ± 0.002 m, large: 0.013 ± 0.004 m, t(15) = 3.8, p = 0.002, d = 0.96]. These findings showed that in the step initiation task, the CoM state and its variability were task-relevantly determined during the APA in accordance with the required stepping accuracy.

The Relationship of some Kinematic Variables to the Performance of Backhand Clear Stroke with Accuracy in Badminton Players

The study aimed to: - Recognize the values of a number of bio kinematical variables for the performance of the backhand clear stroke for badminton players. - Recognize the values of the accuracy test for the performance for the backhand clear stroke of badminton players. - Recognize the relationship between a number of bio kinematical variables and the accuracy values of the backhand clear stroke for badminton players. In order to verify the objectives of the study, the researchers assumed the following: - The existence of a significant relationship between the values of a number of biokinematical variables and the accuracy values of the backhand clear stroke for badminton players. The researchers used the descriptive approach with the correlational style, for its convenience to the study nature, The research sample was selected from the players of the elite clubs registered with the Iraqi Badminton Federation, and the research sample consisted of (7) players The researchers concluded: - The increase of preparing phase time of the backhand clear stroke is directly related to accuracy. - The relationship between the hitting arm's shoulder angle and the free-arm elbow angle with accuracy was direct at the maximum return of the racket, while the relationship was inverse with the forearm with the racket angle variable in the backhand clear stroke skill. - The relationship was direct between accuracy and the lead leg's knee angle variable and inversely with the ankle angle at the moment of the shuttlecock impact in the backhand clear stroke skill.

Comparison of Countermovement and Preferred-Style Jump Biomechanics in Male Basketball Players

The purpose of this study was to investigate and compare the biomechanics of countermovement (CMJ) and preferred-style (PrefJ) jumps. Eight male basketball players (age: 19 ± 1 year; height: 1.84 ± 0.14 m; mass: 92.8 ± 11.4 kg) participated in a cross-sectional study for which they performed max effort CMJ and PrefJ while motion capture and force plate data were recorded. The CMJ were performed according to common procedures. For the PrefJ, the eight players chose to use a short approach run and a step-in jump, with a clear lead and trail leg foot contact pattern. Vertical ground reaction forces (GRF), center-of-mass (COM) parameters, as well as hip, knee, and ankle flexion angles, extension velocities, net joint moments, powers, and work were all calculated and used for analysis. Bi-lateral data from the CMJ were averaged, whereas lead and trail leg data from the PrefJ were kept separated. The PrefJ was characterized by greater jump height and GRF and shorter contact times. Joint-level differences indicated that the PrefJ was characterized by larger joint kinetics. Importantly, very few biomechanical variables of the CMJ and PrefJ were correlated, which suggests that each jump type is characterized by unique movement strategies. Since PrefJ may better represent athlete- and sport-specific movement pattern, these findings could have implications for assessing and monitoring neuromuscular performance of basketball players.

An Analysis of In Vivo Hip Kinematics in Elite Baseball Batters Using a Markerless Motion-Capture System

PurposeThe aim of this study was to investigate the kinematics of the asymptomatic baseball batter’s hips by comparing passive range of motion (PROM) and real-time active hip range of motion (AROM) and determine whether differences in ROM exist between lead and trail hips.MethodsParameters of passive hip ROM were obtained using a goniometer and physical examination standards. Active hip ROM during batting swings was captured with the Dynamic Athletic Research Institute’s markerless motion-capture system.ResultsTwenty-nine elite-level baseball players were recruited for participation. Comparison of lead and trail hips showed no significant differences in PROM. Statistically significant differences in AROM were found between lead and trail legs with large effect sizes for flexion (mean difference [MD°], 11.22), extension (MD°, 30.30), abduction (MD°, 6.24), adduction (MD°, 18.63), external rotation (MD°, 14.87) and total arc of rotation (MD°, 17.17) (P < .001 for all). External rotation in the lead hip approached maximum passive endpoint during early phases of the swing, whereas trail hip extension reached maximum passive endpoint during follow-through.ConclusionThere is a significant difference in the AROM of the lead and trail hips during the batting swing, with active extension in the trail hip, active external rotation of the lead hip, and total arc of rotation of the lead hip nearing their respective passive endpoints and suggesting a potential for bony interaction in the hips of baseball batters.Level of EvidenceLevel 3, Cross-Sectional Study.

Hip Abduction Strength: Relationship to Trunk and Lower Extremity Motion During A Single-Leg Step-Down Task in Professional Baseball Players.

BackgroundThe single-leg step down task (SLSD) is a clinical tool to assess movement and control of the lower extremity and trunk. Hip abduction weakness may impact movement quality during the SLSD, however the relationships between movement and strength are unclear.PurposeTo determine the relationship between hip abduction isometric strength and movement during the SLSD of trunk lean, pelvic drop, knee valgus, and hip flexion.Study DesignCross sectional, cohort studyMethodsOne hundred-eighteen Minor League baseball players (age=21.6 ± 2.0 years; n=68 pitchers, n=50 position players) participated. Bilateral hip abduction isometric strength was measured using a handheld dynamometer (HHD), and then multiplied by distance from the greater trochanter to the HHD and expressed as hip abduction torque. Video cameras captured the SLSD, with participants standing on one leg while lowering their contralateral heel to touchdown on the floor from a 0.203m (8in.) step. Trunk lean, trunk flexion, pelvic drop, knee valgus, and hip flexion were measured using Dartfish at heel touchdown. A value of 180° indicated no knee valgus. Pearson correlations examined the relationships between hip abduction torque and SLSD motions.ResultsThere were no significant correlations for position players. For pitchers, on the lead leg increased hip abduction torque weakly correlated with a decrease in knee valgus (r= 0.24, p=0.049). Also for pitchers on the trail leg, increased hip abduction torque weakly correlated with decreased pelvic drop (r= -0.28, p=0.021).ConclusionHip abduction strength contributes to dynamic control of the trunk and legs. Specifically in pitchers, hip abduction weakness was related to increased movement of the lower extremity and lumbopelvic regions during the dynamic SLSD task. These deficits could translate to altered pitching performance and injury.Levels of Evidence2.

Ankle dorsiflexion deficit in the back leg is a risk factor for shoulder and elbow injuries in young baseball players

The relationship between ankle joint function and throwing-related injuries has not been demonstrated. We hypothesized that limited ankle joint range of motion (ROM) was related to risk factors for shoulder and elbow injuries in young baseball players. This 12-month prospective cohort study evaluated the age, height, weight, playing position, shoulder, elbow, and ankle function of 228 enrolled baseball players. Shoulder and elbow injuries were tracked during the season. Univariate and multivariate analyses were performed to identify risk factors for shoulder and elbow injuries among participants divided into non-injured and injured groups. Univariate analysis showed that age, height, weight, ROM of elbow flexion in the dominant arm, muscle strength ratio of shoulder abduction, and the likelihood of being a pitcher or a catcher were significantly greater in the injured group than in the non-injured group. ROM of shoulder abduction-external/internal rotation, shoulder total arc on the dominant arm, ankle joint dorsiflexion, and plantar flexion on the back (non-lead) and front (lead) legs were significantly less in the injured group than in the non-injured group. In conclusion, ROM dorsiflexion deficits in the back leg, shoulder abduction-external rotation in the dominant arm, ROM increase in elbow flexion on the dominant side, older age, and being a pitcher were significant independent risk factors for injury.

Pitching Mechanics: Do Certain Mechanics Predispose Pitchers to Shoulder Injuries?

Pitching mechanics require a complex biomechanical combination of energy production and transfer up the kinetic chain. The throwing motion can be broken down into six different phases: 1) wind-up, 2) stride/early cocking, 3) late cocking, 4) acceleration, 5) deceleration, and 6) follow-through. While variations in the throwing motion amongst pitchers are common, there are specific kinematic factors that may increase their risk of a significant shoulder injury. The objective of this chapter is to present the pitching mechanics which have been reported in the peer-reviewed literature to have a significant effect on upper extremity rotational kinetics and increase a pitcher's risk of shoulder injury. These include lead leg landing spot and knee flexion angle, trunk rotational timing and positioning, and shoulder range of motion and positioning.

The effect of curve running on distal limb kinematics in the Thoroughbred racehorse.

During racing, injury is more likely to occur on a bend than on a straight segment of track. This study aimed to quantify the effects of galloping at training speeds on large radius curves on stride parameters and limb lean angle in order to assess estimated consequences for limb loading. Seven Thoroughbred horses were equipped with a sacrum-mounted inertial measurement unit with an integrated GPS, two hoof-mounted accelerometers and retro-reflective markers on the forelimbs. Horses galloped 2–4 circuits anticlockwise around an oval track and were filmed at 120 frames per second using an array of ten cameras. Speed and curve radius were derived from GPS data and used to estimate the centripetal acceleration necessary to navigate the curve. Stride, stance and swing durations and duty factor (DF) were derived from accelerometer data. Limb markers were tracked and whole limb and third metacarpus (MCIII) angles were calculated. Data were analysed using mixed effects models with a significance level of p < 0.05. For horses galloping on the correct lead, DF was higher for the inside (lead) leg on the straight and on the curve. For horses galloping on the incorrect lead, there was no difference in DF between inside and outside legs on the straight or on the curve. DF decreased by 0.61% of DF with each 1 m s-2 increase in centripetal acceleration (p < 0.001). Whole limb inclination angle increased by 1.5° per 1 m s-1 increase in speed (p = 0.002). Limb lean angles increase as predicted, and lead limb function mirrors the functional requirements for curve running. A more comprehensive understanding of the effects of lean and torque on the distal limb is required to understand injury mechanisms.

Biomechanics Metrics Associated With Golfing Prowess

PURPOSE: The biomechanics of the golf swing have been studied extensively but specific metrics related to golfing proficiency have not been identified. The purpose of this study was to compare golf swing biomechanics between proficient and average golfers and thereby identify specific metrics associated with golfing proficiency. METHODS: Twenty-two male golfers were categorized as proficient (golf index <6, n=10) or average (golf index 10-24, n=12). Three-dimensional kinematics and ground reaction forces (GRF) were recorded as subjects hit standard golf balls into a net using a driver. Angular velocities of the pelvis, trunk, lead arm and golf club, as well as X-factor, were calculated from the kinematic data. GRF under the lead and back legs are expressed as a % of bodyweight. The effect of golf proficiency on golf swing biomechanics was assessed using independent samples t-tests. RESULTS: Proficient golfers were younger (26±6 yr vs. 48±16 yr, P=0.001) but did not differ in height (P=0.114) or weight (P=0.330). Peak pelvis and trunk velocities were higher (P=0.004) in proficient golfers (525.1±91.6 deg/s and 621.8±89.4 deg/s, respectively) versus average golfers (414.3±67.7 deg/s and 521.3±75.5 deg/s, respectively) but peak club velocity was not different (2509.8±226.1 deg/s vs. 2446.6±420.3 deg/s; P=0.675). Proficient golfers had greater X-factor at the top of the backswing (56.0±6.0 degrees vs. 44.1±11.4 degrees, P=0.008), greater peak X-factor (61.4±5.7 degrees vs. 49.3±11.8 degrees, P=0.008) and greater X-factor at ball impact (34.2±5.8 degrees vs. 22.5±6.5 degrees, P=0.001). Proficient golfers had a higher peak GRF on the lead leg compared with average golfers (142±17 %BW vs. 122±18 %BW, P=0.018), while paradoxically having a lower lead leg GRF at ball impact (56±18 %BW vs. 89±17 %BW, P<0.001). CONCLUSIONS: The higher X-factor in proficient golfers is indicative of a more effective use of elastic energy in the trunk that is sustained through ball impact. The GRF data indicate that proficient golfers more effectively loaded the lead leg during the initiation of the downswing and more effectively unloaded the lead leg prior to ball impact. In conclusion, golf swing proficiency appears to be a function of a more effective transfer of power from the ground and a more effective use of elastic energy in the trunk.

The Relationship Of Stride Length And Joint Stresses Among Adolescent Female Fastpitch Softball Pitchers

PURPOSE: During the softball windmill pitch delivery, power is generated from the lower extremities and transferred up through the kinetic chain out to the throwing hand. At time of stride, the lead lower extremity incurs significant momentum breaking forces that could contribute to injury risk. Joint angle positions at the time of stride may vary based on stride length and extreme ranges of stride length may correlate with biomechanics that are associated with vulnerability to injury. This study investigates the relationship between stride length and 1) joint angles of the lead lower extremity at time of stride and 2) peak joint torques of the lead hip and throwing shoulder during the softball windmill pitch. METHODS: 17 pitchers (mean age= 15.4 ± 1.4 y) underwent 3D biomechanical analysis of 80 fastballs using a 20 motion capture camera system (Vicon Motion Systems Ltd UK) at 240 hz. A 15-segment whole-body model for each pitcher was created. Ankle, knee, hip, and pelvis angles of the lead lower extremity and peak hip and shoulder torques at time of stride were calculated within a biomechanical analysis software (Visual 3D v6, C-Motion). Analyses included 2-tailed Pearson correlations. RESULTS: Stride length correlated positively with peak shoulder external rotation torque (r= 0.245, p= 0.029), lead ankle eversion/inversion, and hip flexion/extension angle at time of stride. Stride length negatively correlated with lead knee valgus/varus, hip abduction/adduction, hip rotation, and pelvis flexion/extension angle at the time of stride (Table 1). No other correlations were observed. CONCLUSION: The most prevalent reported injuries among softball pitchers occur at the shoulder, hip, and low back. Study findings suggest that pitch instruction on lead leg joint position at time of stride as well as stride length may be important for injury prevention during fast pitch softball pitching.

Comparison of the Difference of Ankle Range of Motion and Hip Strength in Both Legs of Fencing Athletes with Ankle Instability

Background: Ankle sprain in the Lead Leg Side (ALLS) is common in fencing athletes, and studies comparing the ankle range of motion (ROM) and strength of both legs are insufficient. Objectvies: To compare the ankle ROM and hip strength between two legs in fencing athletes who has ankle instability in the lead leg side. Design: Cross-sectional design. Methods: Seven fencing athletes with ankle instability participated in this study, and they randomly assigned into ankle in the Lead Leg Side (ALLS) and ankle in the Rear Leg Side (ARLS). Instability was determined by the Cumberland Ankle Instability Tool (CAIT), and then joint ROM and hip muscle strength were measured. Results: There were significant differences in dorsiflexion ROM, hip strength (extension and abduction) between the ALLS with ankle instability and ARLS (P<.05). Conclusion: This study suggests that the ankle ROM and hip muscle strength of ARLS are greater than ALLS in fencing athletes with ankle instability.

Peak horizontal ground reaction forces and impulse correlate with segmental energy flow in youth baseball pitchers

The purpose of this study was to determine associations between horizontal ground reaction force (GRF) kinetics and energy flow (EF) variables in youth baseball players. Twenty-four youth baseball players pitched fastballs in an indoor laboratory while motion capture and force plate data were collected. Horizontal GRF variables were extracted (peak GRF and GRF impulse) while EF was calculated by integrating magnitudes of mechanical powers transferred into and out of the pelvis, trunk, and arm segments via joint force power (JFP) and joint moment power (JMP) components. Peak propulsive GRF of the drive (back) leg correlated with EF into proximal segments, whereas peak braking GRF of the stride (lead) leg correlated with EF into distal segments. Furthermore, peak GRF of the drive leg and GRF impulse of both legs correlated with the JFP components of EF into the pelvis and trunk segments. In contrast, peak GRF and GRF impulse of the stride leg both correlated with the JMP components of EF into the arm segment. These results suggest that horizontal GRF impulse from the drive and stride leg contribute to EF between major segments of the lower and upper extremity. In addition, these results also suggest that propulsion kinetics of the drive leg play a role in transferring linear power via the pelvis and trunk segments in the throwing direction of the pitch, whereas braking kinetics of the stride leg play a role in creating rotational power that is transferred between the trunk and arm segment via the shoulder joint.

Visuomotor Transformation for the Lead Leg Affects Trail Leg Trajectories During Visually Guided Crossing Over a Virtual Obstacle in Humans.

When walking around a room or outside, we often need to negotiate external physical objects, such as walking up stairs or stepping over an obstacle. In previous studies on obstacle avoidance, lead and trail legs in humans have been considered to be controlled independently on the basis of visual input regarding obstacle properties. However, this perspective has not been sufficient because the influence of visuomotor transformation in the lead leg on the trail leg has not been fully elucidated due to technical limitations in the experimental tasks of stepping over physical obstacles. In this study, we investigated how visuomotor transformation in the lead leg affected movement trajectories in the trail leg using a visually guided task of crossing over a virtual obstacle. Trials for stepping over a physical obstacle were established followed by visually guided tasks in which cursors corresponding to the subject’s lead and trail limb toe positions were displayed on a head-mounted display apparatus. Subjects were instructed to manipulate the cursors so that they precisely crossover a virtual obstacle. In the middle of the trials, the vertical displacement of the cursor only in the lead leg was reduced relative to the actual toe movement during one or two consecutive trials. This visuomotor perturbation resulted in higher elevation not only in the lead limb toe position but also in the trail limb toe trajectories, and then the toe heights returned to the baseline in washout trials, indicating that the visuomotor transformation for obstacle avoidance in the lead leg affects the trail leg trajectory. Taken together, neural resources of limb-specific motor memories for obstacle crossing movements in the lead and trail legs can be shared based on visual input regarding obstacle properties.

Fast Bowler\u2019s knee \u2013 anteromedial articular impingement

PurposeTo describe a series of impingement lesions found on the anterior aspect of the medial femoral condyle in international cricketers.MethodsSeven international level fast bowlers presented to our clinic with knee pain in the lead leg between 2005 and 2013. The mean age of the patients was 26.7 years (20–29 years). In all patients a careful history and examination was undertaken followed by appropriate investigations. Conservative management and arthroscopic surgery were performed on these cases. We aimed for a pain free quiet knee with resolved oedema on MRI and return to sport.ResultsMRI images showed oedema in the medial femoral condyle in all patients and 4 patients also had associated cartilage loss. These 4 patients underwent arthroscopic surgery whereas the other 3 were less symptomatic and were managed conservatively. All patients returned to international cricket at an average of 6 months in the non-operative group and 8 months in the operative group.ConclusionAnterior impingement of the anteromedial femoral condyle can be a potentially serious lesion in the fast bowler. A strong index of suspicion regarding this lesion has to be exercised when a fast bowler attends with knee pain and effusion.

Biomechanical Factors Leading to High Loading in the Anterior Cruciate Ligament of the Lead Knee During Golf Swing

For golf swing, the soft tissue structure resisting joint compression and internal rotation of the knee at low flexion angle may be susceptible for a lead knee injury. Therefore, anterior cruciate ligament (ACL) rupture is one of the potential injuries that may occur from repeated stress during golf. The current study was purposed to investigate the biomechanical factors that lead to high ACL load in the lead knee during golf swing. The joint kinematic data of the lead leg and trunk, joint kinetic data of the lead knee, ground reaction force, and the external knee moments were compared between the low and high ACL loading groups. The results demonstrated an increased amount of frontal plane moment arm and external knee adduction (varus) moment just after ball impact for the high ACL loading group. These observations were associated with a characteristic difference in the upper body motion and were the main contributors to the elevated ACL force of the lead knee. The mechanism that generates a high amount of ACL loading during golf swing, which involves the application of external knee adduction moment just after ball impact, may differ from conventional non-contact ACL injury mechanisms that associated with dynamic valgus loading during injury circumstance.

Equal Losses control strategy for all switches of intermediate frequency heating power supply

The energy loss of the switches of the lead legs and lag legs during the operation of the intermediate frequency heating power supply using the traditional full bridge control method has a certain difference, and the greater the power of the device, the more obvious the difference. This phenomenon seriously affects the reliability of high-power intermediate frequency heating power supplies. In this paper, the original full-bridge inverter drive is adjusted, and the conditions for implementing ZVS are analyzed. Finally, the equal losses control strategy for all switches is achieved by using the waveform generated by the FPGA controller.

Upper Extremity and Hip Range of Motion Changes Throughout a Season in Professional Baseball Players

Background: Loss of upper and lower extremity range of motion (ROM) is a significant risk factor for injuries in professional baseball players. Purpose/Hypothesis: The purpose was to determine changes in ROM in professional baseball players over the course of a single season and their careers. We hypothesized that pitchers and position players would lose ROM, specifically total shoulder motion (total ROM [TROM]) and hip internal rotation (IR), over the course of a season and their careers. Study Design: Case series; Level of evidence, 4. Methods: Upper and lower extremity ROM measurements were recorded during pre-, mid-, and postseason on all professional baseball players for a single organization between 2011 and 2018. ROM measurements were compared for pitchers and position players over the course of the season and their careers. Also, ROM measurements over the pre-, mid-, and postseason were compared between pitchers and position players. Results: A total of 166 professional baseball players (98 pitchers, 68 position players) were included. Pitcher hip external rotation (ER; P < .001), IR (P = .010), and TROM (P < .001) for lead and trail legs decreased over the course of the season. Pitcher shoulder ER (P = .005), TROM (P = .042), and horizontal adduction (P < .001) significantly increased over the course of the season. Position player shoulder flexion (P = .046), hip ER (P < .001, lead leg; P < .001, trail leg), and hip TROM (P = .001; P = .002) decreased over the course of the season. Position player shoulder ER (P = .031) and humeral adduction (P < .001) significantly increased over the course of the season. Over the course of pitchers’ careers, there was decreased shoulder IR (P = .014), increased shoulder horizontal adduction (P < .001), and hip IR (P = .042) and hip TROM (P = .027) for the lead leg. Position players experienced loss of hip TROM (P = .010, lead leg; P = .018, trail leg) over the course of their careers. Pitchers started with and maintained more shoulder ER and gained more shoulder TROM over a season as compared with position players. Conclusion: Pitchers and position players saw overall decreases in hip ROM but increases in shoulder ROM over the course of the season and career.

Functional Laterality of the Lower Limbs Accompanying Special Exercises in the Context of Hurdling.

Background: The purpose of this study was to investigate the lateralization of the lead leg during special exercises and the relationship with athletic performance throughout a hurdling session. Methods: Thirty-eight physical education students participated in the study. A novel three-part “OSI” test (walking over hurdles arranged in a circle, spiral, and straight line) was performed, and various hurdle practices (jogging and running) were selected as research tools. The lead leg selected by the participants was taken into consideration, and the relationship between the chosen lead leg and athletic performance in the five tests was established. Results: The lateralization of the lead leg changed depending on the shape of the running course. The results of further analysis showed (i) no correlation between the use of the right leg as the lead leg in three tests conducted at a marching pace, and (ii) a significant positive correlation between tests performed at the marching and running paces. Conclusion: Hurdlers flexibly change the dominant leading leg depending on the shape of the running course. The results of this research could prove helpful in the training of athletes for hurdling competitions, especially young runners in 400-m hurdles involving straight and corner tracks.