Finger forces in fastball baseball pitching

A Retrospective Analysis of Major League Baseball Hit-by-Pitch Rates before and after the Crackdown on Foreign Substance Use

OBJECTIVE

Determine whether there was an increased incidence of hit-by-pitch events in Major League Baseball (MLB) following the decision to enforce the foreign substance ban for pitchers during the 2021 season.

DESIGN

Descriptive Epidemiological Study.

SETTING

Major League Baseball hit-by-pitch data from publicly available Web sites ( mlb.com and fangraphs.com ).

PARTICIPANTS

Major League Baseball players during the 2017, 2018, 2019, 2021, and 2022 seasons.

INDEPENDENT VARIABLES

Hit-by-pitch exposure data by season and individual pitch type.

MAIN OUTCOME MEASURES

Hit-by-pitch incidence rates from the 2017 to 2019 seasons (preenforcement) and the 2021 to 2022 seasons (postenforcement). Rates were compared with incidence rate ratios (IRRs).

RESULTS

Hit-by-pitch incidence rate increased from 2.66 to 3.06 per 1000 total pitches (IRR, 1.15 [95% CI, 1.08-1.23]; P < 0.0001) following the enforcement. Incidence rates for 2017, 2018, and 2019 did not differ from each other individually, but incidence rate of all 3 seasons individually were significantly lower than that for the 2021 season ( P < 0.005). Sliders were 29% more likely to hit batters following the enforcement ( P = 0.0015).

CONCLUSIONS

Major League Baseball batters were hit by pitches at a significantly higher rate following the league's crackdown on foreign substance use for the 2021 seasons compared with the same time of year during the 2017 to 2019 seasons. This was followed by a slight regression toward preenforcement levels during the 2022 season.

Using a Sensor-Embedded Baseball to Identify Finger Characteristics Related to Spin Rate and Pitching Velocity in Pitchers

BACKGROUND

Previous investigations have shown a positive relationship between baseball pitching velocity and the kinetic chain involved in pitching motion. However, no study has examined the influence of finger characteristics on pitching velocity and rate of spin via a sensor-embedded baseball.

METHODS

Twenty-one pitchers volunteered and were recruited for this study. An experimental baseball embedded with a force sensor and an inertial measurement unit was designed for pitching performance measurement. Finger length and strength were measured as dependent variables. Spin rate and velocity were independent variables. Pearson product-moment correlations (r) and intraclass correlation coefficients (ICCs) determined the relationship between finger characteristics and pitching performance.

RESULTS

Finger length discrepancy, two-point pinch strength, index finger RFD (rate of force development), middle finger impulse, and force discrepancy had significant correlations with spin rate (r = 0.500~0.576, p ≤ 0.05). Finger length discrepancy, two-point pinch, three-point pinch strength, index and middle finger RFD, middle finger impulse, and force combination had significant correlations with fastball pitching velocity (r = 0.491~0.584, p ≤ 0.05).

CONCLUSIONS

Finger length discrepancy, finger pinch strength, and pitching finger force including maximal force and RFD may be factors that impact fastball spin rate and fastball pitching velocity.

Predictors of batting and pitching performance in the USA baseball prospect development pipeline

This study examined the relationship between psychomotor abilities and baseball performance by analysing data from 379 athletes who participated in the USA Baseball, Prospect Development Pipeline (PDP). Hit and pitch metrics were generated during practice sessions using the RapsodoTM System. Data were compared through exploratory factor analysis and hierarchical regression. Factor analysis grouped batter's PDP evaluations into four latent variables accounting for 63% of variance. Pitcher performance grouped into three factors accounting for 51% of variance. Regression on batter data revealed a significant demographic/anthropometric base model with height, weight, and age that accounted for 58% of the batted ball speed (R2 = 0.581). Player position explained 2% of the variance (R2 = 0.604), and PDP evaluation scores contributed an additional 3% (R2 = 0.631). Regression of pitcher data showed a significant base demographic/anthropometric model accounting for 36% of fastball pitch speeds (R2 = 0.363), with the PDP evaluation scores adding 6% additional variance (R2 = 0.424). Uniformly, assessments of lower body strength added the greatest predictive information. Hand grip strength did not correlate with pitch metrics. While demographics/anthropometrics are major contributors to batted and pitched ball speed, position and psychomotor variables add statistically significant contributions and may be of practical value for player selection.

Positional relationship between ball and fingers for accurate baseball pitching

Accurately throwing an object to a target position repeatedly is one of the specific human motor skills. The final arrival position of a thrown ball can be determined by its physical state at release. In baseball pitching, reducing the variability of the velocity angle of the ball at release (release angle) is important for reducing the variability of the pitch location. Although previous studies have suggested that hand and finger movements are important for accurate throwing, their relationship with the release angle has not yet been investigated in detail. This study focused on the positional relationship between the ball and fingers, which is considered to be closely related to ball movement as an action point of the force, and examined its relationship with the variability of release angle. To obtain accurate finger positions relative to the ball without impeding movement or sensation, an automatic image recognition technology based on deep learning was employed. This approach revealed a noteworthy correlation between the lower middle finger positions prior to acceleration peaks and the reduced variability in release angle, emphasizing the importance of consistent finger positioning during the pre-release phase. This finger positioning of the pitchers with low variability in the release angle is suggested to be robust against the spatial variability of ball movement.

A new category of "Aha!" driven by touch: A grip sensation into the directional seam on a baseball

We report an "Aha!" experience which differs from conventional Aha's studied over a century in psychological science. The Aha we introduce is driven by touch instead of the visual and verbal modalities widely studied to date. It can occur when gripping a baseball, with a simple input that the red seam on the ball has a direction. Aided by a symmetry analysis and subsequent survey over literature, we show how our mental and physical representation of a baseball can change suddenly by the seam direction and unravel the factors that make the tactile sense into a joyful-and-insightful sensation. Our study sets a new category of Aha driven by touch, opens a new path to investigate the role of touch in our cognition process, reveals the seam direction as a new degree of freedom in baseball aerodynamics and pitching mechanics, and deepens the insights into throwing a baseball from our fingertips.

Evaluation of flexor digitorum superficialis function in adolescent baseball players

Hypothesis and/or Background

Increased flexor digitorum superficialis (FDS) tendon activity can be a therapeutic target for elbow disorders in adolescent baseball players. The proportion of adolescent baseball players who can use FDS independently is unknown, and which finger is most often used remains unclear. This study investigated whether adolescent baseball players intentionally used FDS on each finger.

Methods

Adolescent baseball players were recruited and assessed for FDS function for each finger using the standard technique.

Results

Sixty-nine participants (mean age: 10.4 years) were recruited. Participants numbered 33, 56, 59, and 25 on the throwing side and those numbered 28, 46, 54, and 33 on the nonthrowing side could independently flex the proximal interphalangeal joint while holding their palms in the index, middle, ring, and small fingers, respectively. When assessing both throwing and nonthrowing participants, a significant number of participants could independently flex the proximal interphalangeals of the ring and middle fingers but had difficulty with the index and small fingers (P < .001). No significant difference was noted between the throwing and nonthrowing participants in any finger (P > .05).

Discussion and/or Conclusion

One study reported that participating baseball players with elbow pain have more medial elbow joint space than those without pain symptoms. In another study on finger movements during pitching motion, the force of the thumb, index, middle, and ring fingers was greatest immediately before maximum external rotation. According to both reports, FDS function, especially in the index finger, can be a therapeutic target for medial-sided elbow injuries in adolescent baseball players.

High elasticity of the flexor carpi ulnaris and pronator teres muscles is associated with medial elbow injuries in youth baseball players

OBJECTIVES

The purpose of the present study was to measure the elasticities of the forearm flexor-pronator muscles in youth baseball players and examine their relationships with medial elbow injuries.

METHODS

We examined the strain ratios (SR) of the flexor digitorum superficialis (FDS), flexor carpi ulnaris (FCU), and pronator teres (PT) in 89 youth baseball players with medial epicondylar fragmentation (injury group) and in 142 healthy baseball players (control group). An index of muscle elasticity was determined using ultrasound strain elastography. The SR of each muscles was compared between the injury and control groups, and the SR of the both side arms was compared within group. Moreover, multivariable logistic regression analyses were conducted to examine the association of forearm muscle elasticity with medial elbow injuries.

RESULTS

The SR of the FCU and PT of the throwing arm were significantly higher in the injury group than in the control group (both P < .001). In the injury group, the SR of the FCU was higher in the throwing arm than in the non-throwing arm (P < .001), but no difference was noted for the PT. Multivariable logistic regression analyses showed that a 0.1 increase of the SR of the FCU of the throwing arm (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.14-1.48) and PT of the throwing arm (OR 1.41, 95% CI 1.19-1.67) and the non-throwing arm (OR 1.31, 95% CI 1.12-1.54) was significantly associated with an increased prevalence of medial elbow injuries.

CONCLUSION

High elasticities of the FCU of the throwing arm and PT of both the arms were observed in individuals with medial elbow injuries, and were associated with increased prevalence of medial elbow injuries. These findings may be characteristic of medial elbow injuries in youth baseball players.

Estimation of tangential finger force and its relationship with the spin rate of pitched fastball

This study had two objectives: (a) estimating the force exerted by pitchers in generating the spin of a fastball and (b) examining the factors that influence the spin rate of a fastball. Thirteen baseball pitchers participated in this study. The resultant forces acting on the ball was measured using an accelerometer placed in the baseball, and the force was decomposed into two frequency components using maximal overlap discrete wavelet transform. The intraclass correlation coefficients (ICC) between the integration of the high-frequency component of acceleration and the variation in the tangential velocity was high (ICC(3,1) = 0.64 ± 0.16). The ball spin per velocity (SPV) was significantly correlated with the peak value of the high-frequency component of the resultant forces (r = 0.66, p < 0.01). The high-frequency component of the resultant forces reflected the force in the tangential direction, and this force was one of the factors that adjusted the ball spin rate. The SPV did not significantly correlate with the peak value of the low-frequency component of the resultant forces (r = 0.50, p > 0.05). This indicates that decomposing the resultant forces into two frequency components is necessary to investigate the function of the finger during pitching.

The relationship between changes in elbow valgus laxity and forearm flexor strength during repetitive pitching

This study examined the changes in the medial elbow joint space width and forearm flexor strength due to repetitive pitching and analysed the relationships among these factors. Thirty-one collegiate baseball players pitched seven sets of 15 pitches each. The medial elbow joint space width, grip strength, and forearm flexor strengths were measured before pitching and after each set. These parameters were compared at baseline and after pitching for each set. Additionally, the relationships between changes in the medial elbow joint space and forearm flexor strength were examined for each set. The medial elbow joint space width significantly increased after four sets compared to baseline values. Compared to baseline values, grip strength decreased significantly after one set, wrist flexion and radial deviation after six, and ulnar deviation after five. However, changes in the medial joint space compared to baseline values after each set were not significantly correlated with changes in forearm flexor strength variables. Therefore, repetitive pitching causes an increase in elbow valgus laxity and a decrease in forearm flexor strength. However, the decrease in forearm muscle strength does not explain the increase in elbow valgus laxity.

Finger friction with leather and seam of new and used softballs with and without rosin powder

The purpose of this study was to investigate the friction of finger against polyurethane-coated leather and seam surfaces of new and used softballs. The effects of seam alignment (across and along the seam) and chalk/rosin powder application were also investigated. The coefficient of static friction (COF) was evaluated on 14 college female softball players who rubbed the pad of their index finger on a test surface fixed on a biaxial force plate. The mean COF of the new leather was 1.04, and those of the seam were 1.16 for the across condition, and 1.07 for the along condition. The leather-seam difference in COF was significant. The used ball's leather and seam had lower COF than those of the new ball. The seam alignment difference did not reach the level of significance. For both new and used balls, the application of chalk/rosin powder to the finger reduced COF, and the reduction was greater on the leather than on the seam. It was concluded that the outer cover of softballs, and especially the seam portions, is equipped with reasonably high friction under natural finger condition. The friction is reduced in used balls and with the use of chalk/rosin powder.

Kinetic Analysis of the Fingers Under Different Ball Velocities During Overarm Throwing

The purpose of this study is to examine changes in the kinetic parameters of the fingers caused by differences in ball velocity during overarm throwing. Six baseball players participated in the study, and the kinetics of the wrist and metacarpophalangeal (MP) joint were calculated using an inverse dynamics method. The results of Tukey's multiple comparison tests showed that the torque and work of the wrist increased with increasing ball velocity (p < .05), indicating that wrist torque and work contributed to the adjustment of ball velocity. Peak MP joint torque also increased with ball velocity (p < .05), although the work of the MP joint remained relatively constant. We conclude that MP joint torque and work contribute to the achievement of stable ball release rather than adjusting ball velocity.

Ultrasonographic digital blood flow measurement in professional baseball pitchers - A quantitative and comparative study with non-throwers

BACKGROUND

Vascular disorders in throwing athletes can occur from the thoracic outlet to the fingertips. The occurrence of these disorders around the shoulder is well known, and treatment options have been established for them. However, the occurrence of vascular pathology in the digital arteries in elite baseball pitchers is unclear, and treatment options have not yet been established. We hypothesized that asymptomatic professional baseball pitchers often have existing pathological changes in their digital blood flow; therefore, we quantitatively measured the blood flow in the index finger using ultrasonography and compared the results to those of non-baseball players.

METHODS

Seven asymptomatic professional baseball pitchers (pitcher group) and 11 healthy volunteers (control group) were included. The flow velocity, flow volume and vessel resistance index of the ulnar digital artery of the index finger were measured just distal to the proximal interphalangeal joint using pulsed wave Doppler in two positions: 1) with the proximal interphalangeal (PIP) joint relaxed (10-15° flexed) and 2) with the PIP joint passively extended (0-5°).

RESULTS

The mean flow velocity and flow volume were lower in the extended position than in the relaxed position in both groups. In the dominant hand, which was the throwing hand in the pitcher group, the mean flow velocity and the flow volume in the relaxed position were significantly lower in the pitcher group than in the control group. The vessel resistance index in the relaxed position of the dominant hand was significantly higher in the pitcher group than in the control group. In the nondominant hand, there was no significant difference in any parameter between the two groups.

CONCLUSIONS

Asymptomatic professional baseball pitchers may have a pathological change in digital blood flow in the throwing hand. As treatment options for this condition have not yet been established, it is of utmost importance to carry out periodic examination and prevention before the condition progresses to the symptomatic end stage.

Influence of pitching grip on shoulder and elbow injuries in junior baseball players, focusing on hand length and the metacarpophalangeal joint angle

[Purpose] We investigated the relationship of pitching grip with hand length and index finger metacarpophalangeal joint angle. [Participants and Methods] A total of 650 junior baseball players divided into two groups according to whether they experienced shoulder or elbow pain were divided into two groups based on their pitching grip, i.e., those who held the ball with the ulnar side of the thumb and those who held it with the finger pad of the thumb. The metacarpophalangeal joint angle was measured while the participants held a ball. [Results] The average hand length was 16.3 ± 1.4 cm for those holding the ball with the ulnar side of the thumb and 15.8 ± 1.2 cm for those holding it with the finger pad of the thumb. Hand length and metacarpophalangeal angle were significantly greater in the group using the ulnar side of the thumb. The two groups showed no significant differences in the distribution of grip type or history of shoulder/elbow pain. The index finger metacarpophalangeal angle and shoulder/elbow pain were significantly lower in the pain group. [Conclusion] With respect to the pitching grip for junior baseball players, we recommend a slightly flexed rather than extended position with the metacarpophalangeal angle.

Elasticity of the Flexor Carpi Ulnaris Muscle After an Increased Number of Pitches Correlates With Increased Medial Elbow Joint Space Suppression

ABSTRACT

Saito, A, Namiki, Y, and Okada, K. Elasticity of the flexor carpi ulnaris muscle after an increased number of pitches correlates with increased medial elbow joint space suppression. J Strength Cond Res 35(9): 2564-2571, 2021-This study aimed to measure the medial elbow joint space and elasticity of the forearm flexor-pronator muscles in repetitive pitching and to determine which of the forearm flexor-pronator muscles contribute to elbow valgus stability during pitching. Twenty-six collegiate baseball players performed 7 sets of 15 pitches. The medial elbow joint space and elasticity of the pronator teres, flexor carpi radialis, flexor digitorum superficialis (FDS), and flexor carpi ulnaris (FCU) were measured using ultrasonography before pitching and after every 15 pitches. Correlations among the rate of change of these parameters were analyzed using Pearson's correlation coefficients. The medial elbow joint space increased after 60 or more pitches compared with that before pitching (all p < 0.001; effect size [ES]: 0.44-1.22). FDS and FCU elasticity increased after 45 and 60 pitches or more in contrast to that before pitching, respectively (FDS: p = 0.047 and p < 0.001, respectively; ES: 1.05-1.42, FCU: p = 0.011 and p < 0.001, respectively; ES: 1.11-1.48). After 75 or more pitches, the rate of change of FCU elasticity correlated negatively with that of the medial elbow joint space (r = -0.395, r = -0.454, and r = -0.404, after 75, 90, and 105 pitches, respectively). Increased FCU elasticity after repetitive pitching correlated with suppression of the increase of the medial elbow joint space. The FCU may be the primary dynamic stabilizer against the elbow valgus force, and evaluation of the FCU elasticity may be important for preventing elbow injuries.

Relationships Between Clinically Measured Upper-Extremity Physical Characteristics and Ball Spin Rate in Professional Baseball Pitchers

ABSTRACT

Wong, R, Laudner, K, Evans, D, Miller, L, Blank, T, and Meister, K. Relationships between clinically measured upper-extremity physical characteristics and ball spin rate in professional baseball pitchers. J Strength Cond Res 35(5): 1331-1337, 2021-During baseball pitching, physical characteristics of the shoulder, elbow, wrist, hand, and fingers have been hypothesized to be critical to creating ball spin. The purpose of this study was to determine if pitchers with greater shoulder, elbow, wrist, and finger range of motion (ROM), arm and hand length, wrist strength, or grip and finger strength would produce greater ball spin than those with less physical characteristics. Ninety, asymptomatic, professional baseball pitchers participated (age = 24.5 ± 3.9 years; height = 189.9 ± 6.1 cm; body mass = 92.6 ± 10.6 kg). Goniometers and a digital level were used to measure shoulder, elbow, wrist, and finger ROM, a tape measure was used to assess arm and hand lengths, and handheld dynamometers were used to measure wrist, grip, and finger strength. Ball spin was measured using a 3-dimensional Doppler radar and video system. Standard multiple regression analyses showed no significant relationships existed between ball spin and any of the upper-extremity ROM or limb length variables (R2 = 0.01-0.03; p = 0.40-0.94). However, there was a significant relationship for the summation of wrist strength (R2 = 0.24, p = 0.03). Both time to wrist extension strength {B = 0.50 (95% confidence interval [CI]: 0.23-0.76), p = 0.001} and radial deviation strength (B = 0.41 [95% CI: 0.15-0.66], p = 0.002) were significant predictors within this model. These results demonstrate that the rate of ball spin during a pitch may be partially altered by increasing wrist extension acceleration and radial deviation strength. However, the subsequent clinical measurements of shoulder, elbow, wrist, and finger ROM, arm and hand length, and grip and finger strength were not associated with ball spin.

Skeletal muscle metabolism on whole-body positron emission tomography during pitching

Background

Electromyography (EMG) has been used for evaluating skeletal muscle activity during pitching. However, it is difficult to observe the influence of movement on skeletal muscle activity in deep-lying regions of the trunk and extremities using EMG. An alternative method that may be used is the measurement of glucose metabolism of skeletal muscle using positron emission tomography-computed tomography (PET-CT). This technique is a reliable measure of muscle metabolism, demonstrating a high correlation with the intensity of muscle activity. This study aimed to evaluate whole-body skeletal muscle metabolism during pitching using PET-CT.

Methods

Ten uninjured, skilled, adult pitchers, who were active at college or professional level, threw 40 baseballs at maximal effort before an intravenous injection of 37 MBq of ¹⁸F-fluorodeoxyglucose (FDG). Subsequently, additional 40 balls were pitched. PET-CT images were obtained 50 min after FDG injection, and regions of interest were defined within 72 muscles. The standardized uptake value (SUV) of FDG by muscle tissue per unit volume was calculated, and the mean SUV of the pitchers was compared with that of a healthy adult control group who did not exercise before the measurements. Statistical analysis was performed using a t-test, and P < 0.05 was considered statistically significant.

Results

Whole-body PET images showed a significant increase in glucose metabolism in the muscle groups of the fingers and toes in both the throwing and non-throwing sides. Additionally, asymmetric increases in glucose metabolism were observed in the muscles of the thigh.

Conclusions

This is the first study to evaluate whole-body muscle metabolism during pitching using PET-CT. Our findings would be useful in determining the training required for pitchers, and can be further applied to other sporting activities that involve throwing.

Kinetic analysis of the wrist and fingers during fastball and curveball pitches

This study had two objectives: (a) revealing kinetic parameter differences at the fingers during a fastball and curveball, and (b) examining timing control between the wrist and finger torques. The participants were eight baseball pitchers. The kinetics of the wrist and fingers were calculated using an inverse dynamics method. The peak torque and work of finger adduction during the curveball was significantly larger than that during the fastball. During the fastball pitch, the maximal correlation coefficient between the wrist flexion torque and finger flexion torque was very high (r = 0.94 ± 0.05). The reasons for this result are twofold: (a) the extrinsic finger muscles cross the wrist (biarticular muscle) and (b) the wrist flexion torque during the fastball pitch acts in the direction of acceleration of the ball. During the curveball pitch, we found two typical types of wrist and finger torque control. Furthermore, the two pitchers exerted large wrist extension and radial torque, and finger adduction torque. Although the other six pitchers hardly exerted these torques, they exerted wrist flexion torque predominantly. It was considered that the six pitchers selected wrist flexion torque as the control for the fastball and curveball pitch to confuse the batter.

Effects of Rosin Powder Application on the Frictional Behavior Between a Finger Pad and Baseball

Rosin powder, which is composed of magnesium carbonate powder and pine resin, is often used as a grip-enhancing agent in baseball pitching. However, the effect of rosin powder on friction at the baseball-human finger interface remains unclear. This study aimed to investigate the effect of rosin powder on the friction coefficient between a baseball and a finger using sliding friction tests. Ten young adult males participated in this study who were asked to slide the index finger of their dominant hand over the leather skin of a baseball adhered to the force sensor, which was not a real baseball pitching situation. Our findings suggest that rosin powder application stabilizes friction under both dry and wet conditions; that is there was less dependence of the friction coefficient on the normal force and less variation in the friction coefficient among individuals. For most participants, the friction coefficient was not necessarily increased by the presence of rosin powder at the finger pad-leather sheet interface under dry conditions. However, under wet conditions, rosin powder application increased the friction coefficient compared with the non-powdered condition in the large normal force condition, indicating the efficacy of rosin powder as a grip-enhancing agent.

Sport Biomechanics Applications Using Inertial, Force, and EMG Sensors: A Literature Overview

In the last few decades, a number of technological developments have advanced the spread of wearable sensors for the assessment of human motion. These sensors have been also developed to assess athletes' performance, providing useful guidelines for coaching, as well as for injury prevention. The data from these sensors provides key performance outcomes as well as more detailed kinematic, kinetic, and electromyographic data that provides insight into how the performance was obtained. From this perspective, inertial sensors, force sensors, and electromyography appear to be the most appropriate wearable sensors to use. Several studies were conducted to verify the feasibility of using wearable sensors for sport applications by using both commercially available and customized sensors. The present study seeks to provide an overview of sport biomechanics applications found from recent literature using wearable sensors, highlighting some information related to the used sensors and analysis methods. From the literature review results, it appears that inertial sensors are the most widespread sensors for assessing athletes' performance; however, there still exist applications for force sensors and electromyography in this context. The main sport assessed in the studies was running, even though the range of sports examined was quite high. The provided overview can be useful for researchers, athletes, and coaches to understand the technologies currently available for sport performance assessment.

Valgus stability is enhanced by flexor digitorum superficialis muscle contraction of the index and middle fingers

Background

Flexor digitorum superficialis (FDS) muscle provides dynamic stabilization and medial elbow support for ulnar collateral ligament (UCL). The FDS contraction significantly affects the medial joint distance (MJD) through grip contraction. However, it remains unclear whether FDS activity alone contributes to medial elbow stability, or together with the activation of the flexor digitorum profundus during grip contraction, and which finger’s FDS is the main contributor to elbow stability. We investigated the resistive effects of isolated FDS contraction in individual fingers against valgus stress in the elbow joint using stress ultrasonography (US).

Methods

We investigated 17 healthy males (mean age, 27 ± 5 years). Valgus stress US was performed using the Telos device, with the elbow at 30° flexion. MJD was measured for each arm during 3 separate conditions: at rest (unloaded), under valgus load (50 N) (loaded), and under valgus load with FDS contracted in individual fingers (loaded-contracted).

Results

MJD was significantly longer when loaded (5.4 ± 0.4 mm) than unloaded (4.1 ± 0.2 mm, P = 0.007) or loaded-contracted (4.6 ± 0.3 mm, P = 0.003) for each finger. When loaded-contracted, MJD differed statistically between the index and ring fingers (P = 0.03) and between the middle and ring fingers (P = 0.04). However, the difference between the index and middle fingers was not statistically significant (P = 0.08).

Conclusions

Individual FDS contraction, particularly of the index and middle fingers, contributes most to stabilization against valgus stress. Thus, injury care programs should incorporate FDS exercises of these fingers.

Rehabilitation and Prehabilitation for Upper Extremity in Throwing Sports: Emphasis on Lacrosse

Lacrosse imposes multiple simultaneous physical demands during play including throwing and catching a ball while holding a crosse, running, cutting, and jumping. Often, these skills are completed while experiencing contact from another player leading to both on-and-off platform movements. Other motions include defensive blocking and pushing past defenders. Repetitive motions over sustained durations in practice or competition impart mechanical stresses to the shoulder or elbow joints, supportive muscles, and connective tissue. Preparation for lacrosse participation involves bilateral optimization of strength and durability of stabilizer muscles. Passing and shooting skills are encouraged to be equally effective on both sides; therefore, symmetric strength and flexibility are vital for prehabilitation and rehabilitation efforts. This article will: 1) provide insights on the upper-extremity musculoskeletal demands of lacrosse and related sports with similar throwing motion and 2) describe prehabilitation and rehabilitation methods that improve athlete durability and reduce likelihood of upper-extremity injury.

Contribution of interaction torques during dart throwing: Differences between novices and experts

We examined if experts and novices show different utilization of the torque components impulses during dart throwing. Participants threw darts continuously at a dartboard aiming for the centre (target bull's eye). The upper-limb joint torque impulses were obtained through inverse dynamics with anthropometric and motion capture data as input. Depending on the joint degree of freedom (DOF) and movement phase (acceleration and follow-through), three main strategies of net torque (NET) impulse generation through joint muscle (MUS) and interaction (INT) torque impulses were highlighted. Firstly, our results showed that the elbow flexion-extension DOF leads the movement according to the joint leading hypothesis. Then, considering the acceleration phase, the analysis revealed differences in torque impulse decomposition between expert and novices. For the glenohumeral (GH) joint abduction-adduction and for wrist flexion, the INT torque impulse contributed positively to NET joint torque impulse in the group of experts unlike novices. This allowed to lower the necessary MUS torque impulse at these DOFs. Also, GH axial rotation was actively controlled by muscle torque impulse in the group of experts. During the follow-through, the experts used the INT torque impulse more proficiently than novices to break the elbow extension. The comparison between experts and novices through inverse dynamics document the link between the exploitation of interaction torques impulses and expertise in dart throwing for which the main objective is precision rather than velocity.