Comparison of Pain Characteristics, Strength, and Movement Patterns in Adolescents With Juvenile Fibromyalgia and High Versus Low Fear of Movement.

Physical activity avoidance and fear of movement (FOM) is often observed in individuals with chronic musculoskeletal pain, along with difficulties coping with pain. There is little research regarding how FOM may also relate to reduced physical strength and altered movement patterns that may perpetuate a cycle of pain, FOM, and disability. The objective of this observational study was to compare how adolescents with juvenile fibromyalgia (JFM) exhibiting high versus low FOM (Tampa Scale of Kinesiophobia-11) differed on patient-reported measures of pain, fatigue, catastrophizing and pain interference, and performance-based measures of strength, postural control, and biomechanical function. Participants were youth with JFM (N = 135, Meanage = 15.6 years, 88.9% female) enrolled in an ongoing clinical trial who completed self-report questionnaires and standardized tests, including knee and hip strength, the Star Excursion Balance Test, and the Drop Vertical Jump (with 3 dimensional motion capture). Participants were categorized into Low, Medium, and High FOM groups based on Tampa Scale of Kinesiophobia-11 tertile scores. Relative to the Low FOM group, the High FOM group reported significantly greater fatigue, pain interference and catastrophizing, as well as reduced dominant leg knee strength. Additionally, those with high FOM showed altered lower-extremity movement patterns. This preliminary study highlights the importance of combining self-reported measures of symptoms and functioning with physical assessments to gain a more comprehensive view of the impact of FOM in patients with chronic musculoskeletal pain. The results could inform the development of more precise interventions to reduce FOM using a combination of behavioral and exercise-based interventions. PERSPECTIVE: The results of this study demonstrate the association between FOM, fatigue and pain interference in adolescents with JFM, as well as preliminary evidence for altered movement patterns in that may predispose them to further pain/injury and activity avoidance. GOV REGISTRATION: NCT03268421.

Cueing Dancers to "Externally Rotate From the Hips" Improves Potentially Injurious Ankle Joint Angles and Contact Forces During a Demipointe Ballet Position.

Introduction: The demipointe dance position puts the ankle at high risk of overuse injury and posteromedial ankle pain due to increased ankle valgus forces. Previous work has shown that creating lower limb external rotation intrinsic to demipointe with hip external rotation reduces foot pronation that causes ankle valgus stress. Therefore, the purpose of this work was to examine long axis rotation kinematics of the hip, knee, and ankle as well as the ankle joint contact forces in demipointe to better understand the biomechanical impact(s) of the specific cue to increase hip external rotation in this position. Methods: Three-dimensional motion capture and force plate data were collected from 23 contemporary or ballet pre-professional dancers (age: 19.94 ± 1.34 years) who each performed 3 dancer-selected (DS) demipointe positions and 3 demipointes with the cue to "externally rotate from the hips." Results: The cue to increase hip external rotation resulted in significantly increased hip external rotation angle [DS: 37.5; 9.42° (median; interquartile range), Cued: 39.9; 10.8°, P < .0001)] and significantly reduced ankle eversion angle (DS: 8.13; 11.4°, Cued: 7.77; 10.3°, P = .023). However, total turnout angle was also significantly decreased (DS: 75.8; 7.91°, Cued: 75.4; 7.73°, P < .0001), which is undesirable for proper esthetic performance of demipointe. Total ankle joint force remained unchanged, but ankle eversion force was significantly reduced (DS: 15.3; 4.18 %bodyweight (BW), Cued: 14.7; 4.99 %BW, P < .0001) with use of the cue. Discussion/Conclusion: Utilization of a cue to increase hip external rotation was successful in increasing hip contribution to turnout angle and reducing injurious ankle eversion force. Further coaching using this cue may allow dancers to produce these advantageous mechanics while maintaining turnout angle.

Kinematic and kinetic comparison between preprofessional pitchers from the Dominican Republic and the United States.

Introduction: Pitching biomechanical efficiency is defined as the association between pitch velocity and arm kinetics. Pitching mechanics inefficiency, an increase in arm kinetics without the resultant increase in pitch velocity, can lead to increased arm strain, increasing arm injury risk. The purpose of this study was to compare arm kinetics, elbow varus torque and shoulder force, in preprofessional United States (US) and Dominican Republic (DR) pitchers. Kinematics that are known to influence elbow varus torque and shoulder force as well as a representative of pitch velocity (hand velocity) were also compared. Methods: A retrospective review was performed on baseball pitchers from the DR and US who participated in biomechanical evaluations conducted by the University biomechanics laboratory personnel. Three-dimensional biomechanical analyses were performed on US (n = 37) and DR (n = 37) baseball pitchers. Potential differences between US and DR pitchers were assessed through analysis of covariance with 95% confidence intervals [95% confidence Interval (CI)]. Results: Preprofessional DR pitchers experienced increased elbow varus torque compared with their US counterparts [DR: 7.5 (1.1); US: 5.9 (1.1) %BWxH; Beta: -2.0 (95% CI: -2.7, -1.2) %BWxH], despite throwing fastballs with slower hand velocity [DR: 3,967.1 (939.4); US: 5,109.1 (613.8) °/s; Beta: 1,129.5 (95% CI: 677.5, 1,581.4) °/s]. DR and US pitchers demonstrated similar shoulder force [DR: 136.8 (23.8); US: 155.0 (25.7); Beta: 0.4 (95% CI: -1.2, 19.7) %BW]. Discussion: Increased elbow varus torque although decreased hand velocity suggests inefficient pitching mechanics among DR pitchers. Inefficient pitching mechanics and increased elbow torque should be considered when developing training programs and pitching plans for professional pitchers from the Dominican Republic.

Biomechanical Analysis of the Throwing Athlete and Its Impact on Return to Sport.

Throwing sports remain a popular pastime and frequent source of musculoskeletal injuries, particularly those involving the shoulder and elbow. Biomechanical analyses of throwing athletes have identified pathomechanic factors that predispose throwers to injury or poor performance. These factors, or key performance indicators, are an ongoing topic of research, with the goals of improved injury prediction, prevention, and rehabilitation. Important key performance indicators in the literature to date include shoulder and elbow torque, shoulder rotation, kinetic chain function (as measured by trunk rotation timing and hip-shoulder separation), and lower-extremity mechanics (including stride characteristics). The current gold standard for biomechanical analysis of the throwing athlete involves marker-based 3-dimensional) video motion capture. Emerging technologies such as marker-less motion capture, wearable technology, and machine learning have the potential to further refine our understanding. This review will discuss the biomechanics of throwing, with particular attention to baseball pitching, while also delineating methods of modern throwing analysis, implications for clinical orthopaedic practice, and future areas of research interest. LEVEL OF EVIDENCE: V, expert opinion.

Relationship between ground reaction force and throwing arm kinetics in high school and collegiate pitchers.

BACKGROUND: Throwing a baseball requires the transmission of forces generated in the lower extremity, through the trunk, to the upper extremity, and ultimately translates to the ball. A disruption in the functioning of the lower extremities could lead to altered upper extremity kinematics and increased load exerted on the shoulder and elbow. The purpose of this study was to examine the relationship of ground reaction forces (GRF) on the drive and stride sides and kinetics of the throwing arm in high school and collegiate baseball pitchers. METHODS: In this retrospective cross-sectional study, data that were previously collected during a pitching evaluation were analyzed. Fifty high school pitchers and 26 collegiate pitchers had received a pitching evaluation. Multiple regression analysis was used to examine the relationships between variables. RESULTS: Only the drive leg medial force was determined to be a significant predictor of maximum shoulder external rotation torque. Maximum elbow valgus torque was not correlated with any GRF variables and ball speed was only weakly correlated with stride leg medial force. There were no significant differences in GRFs between the high school and college pitchers. CONCLUSIONS: Due to the limited relationships present, other factors such as muscle strength, coordination, kinematics, or stride technique may overshadow the effects of GRF in highly skilled pitchers and warrant further investigation. Understanding this relationship will be important to both enhancing performance and avoiding injury.

Comparison of OnBaseU Tests with Biomechanical Motion Analysis in Youth Baseball Pitchers.

BACKGROUND: The OnBaseU screen was developed to evaluate a baseball pitcher's ability to perform movement patterns key to pitching. However, due to lack of validation, it is unclear what application is ideal for this screen. PURPOSE: To compare four OnBaseU tests to relevant pitching mechanics measured using 3D motion capture to evaluate if the OnBaseU screen can be used to assess pitching mechanics. The secondary purpose was to compare OnBaseU and 3D motion capture seated trunk rotation test results to determine the validity of the OnBaseU test. METHODS: OnBaseU screening and 3D motion capture pitching evaluations were completed for 103 adolescent pitchers (age = 15.2 ± 1.29 years; height = 1.80 ± 0.0866 m; weight = 76.2 ± 13.8 kg). A motion capture seated trunk rotation test was also conducted on 80 of the 103 youth players (age = 15.2 ± 1.32 years; height = 1.80 ± 0.0889 m; weight = 75.7 ± 13.9 kg). RESULTS: Stride length and OnBaseU side step walkout test data were moderately correlated, and all other comparisons were not correlated or were minorly correlated. No significant differences were found between kinematics from players who obtained different OnBaseU scores, except for stride lengths during pitching of players who scored a 1 or 3 on the OnBaseU side step walkout test (p<0.01). Further, OnBaseU and motion capture seated trunk rotation tests were not correlated (r = 0.003) and not found to be statistically associated (p = 0.83). CONCLUSION: Results from this study indicate that the OnBaseU clinical assessment screen may not have use in assessing pitching mechanics and that visual grading criteria used in the OnBaseU seated trunk rotation test may not be accurate. LEVEL OF EVIDENCE: 3.

Relationship Between Clinical Scapular Assessment and Scapula Resting Position, Shoulder Strength, and Baseball Pitching Kinematics and Kinetics.

BACKGROUND: Scapular assessment is important in examining overhead athletes, but there is inconsistency in scapular clinical assessment and its relation to pathology. PURPOSE: To determine the relationship between clinical scapular assessment and biomechanical scapula resting position, shoulder strength, and pitching shoulder kinematics and kinetics. STUDY DESIGN: Descriptive laboratory study. METHODS: Two clinicians performed scapular assessments and graded the scapula as presence or absence of scapular dyskinesis. Shoulder external rotation (ER) and internal rotation (IR) strength were collected. The 3-dimensional biomechanics of the scapula resting position (upward/downward rotation, IR/ER, and anterior/posterior tilt) were assessed while participants stood at rest, and pitching kinematics (maximum shoulder ER, shoulder abduction, shoulder horizontal abduction, shoulder rotation velocity) and kinetics (maximum shoulder distraction force) were assessed when participants pitched off the portable pitching mound that was engineered to meet major league specifications. RESULTS: A total of 33 high school baseball pitchers (age, 16.3 ± 1.2 years; height, 184.0 ± 6.9 cm; weight, 76.8 ± 20.8 kg; hand dominance: left, 9 [27%]; right, 24 [73%]; pitch velocity, 34.7 ± 2.3 m/s) participated in this study. Of them, 15 participants had scapular dyskinesis, and 18 had normal scapulothoracic rhythm. No differences were observed for upward/downward rotation or anterior/posterior tilt, shoulder ER, shoulder abduction, or shoulder distraction force, based on the presence of scapular dyskinesis. Pitchers with scapular dyskinesis demonstrated significantly greater scapular resting IR position (effect size [ES], 0.80; 95% CI, 0.06 to 1.54; P = .020), greater nondominant shoulder ER to IR strength ratio (ES, 0.49; 95% CI, -0.02 to 1.00; P = .018), and decreased shoulder rotation velocity (ES, 14.66; 95% CI: 12.06 to 17.25; P = .016). Pitchers with greater anterior tilt demonstrated greater shoulder rotation velocity (r = -0.48; P = .006). CONCLUSION: Pitchers with scapular dyskinesis had greater scapular IR, greater nondominant shoulder ER to IR strength ratio, and reduced shoulder rotation velocity. CLINICAL RELEVANCE: Scapular assessment may be more influenced by differential IR than upward rotation or anterior tilt. Scapular dyskinesis has no competitive performance advantage among amateur athletes. Greater understanding is needed to decipher the critical threshold between beneficial and maladaptive scapular movement patterns.

Comparative Pitching Biomechanics Among Adolescent Baseball Athletes: Are There Fundamental Differences Between Pitchers and Non-pitchers?

BACKGROUND: Approximately 25% of youth baseball players pitch, with most young athletes predominately playing multiple positions. While some youth baseball players may primarily pitch, other players may only pitch on occasion, potentially creating a pitching skill level discrepancy. Understanding potential kinematic and kinetic differences between pitching and non-pitching baseball players can inform injury risk reduction strategies for amateur athletes. PURPOSE/HYPOTHESIS: To analyze differences in pitching biomechanics for fastballs, breaking balls, and change-ups in adolescent youth baseball players that identify as pitchers and non-pitchers. STUDY DESIGN: Retrospective cross-sectional study. METHODS: Baseball players were designated as pitchers or non-pitchers, who then threw fastballs (FB), breaking balls (BB), and change-ups (CH) during a biomechanical assessment. T-tests, Mann-Whitney U tests, and ANOVAs with Bonferroni correction, and effect sizes (ES) were performed. RESULTS: Sixty baseball players (pitchers = 40; non-pitchers = 20; Age: 15.0 (1.1); Left-handed: 15%; Height 1.77 (0.09) m; Weight: 70.0 (12.5) kg) threw 495 pitches (FB: 177, BB: 155, CH: 163) for analysis. Pitchers threw 2 m/s faster and produced greater trunk rotation velocity (ES: 0.71 (95% CI: 0.39, 1.30, p<0.0001) than non-pitchers. Furthermore, pitchers demonstrated greater ground reaction force for FB compared to CH (ES: 0.48 (95% CI: 0.01, 0.94), p<0.0001). No other biomechanical differences were observed between pitchers and non-pitchers or between pitch types. CONCLUSION: Despite throwing at greater velocity for all pitch types, baseball players that identify primarily as pitchers had overall similar kinematics and kinetics in comparison to baseball players that primarily identify as non-pitchers. Self-identified pitching baseball athletes have improved force transfer strategies for ball propulsion, utilizing different force production and attenuation strategies across different pitch types when compared to non-pitchers. Coaches should consider that novice pitchers may potentially have dissimilar trunk and ground reaction strategies in comparison to primary pitchers when designing appropriate pitch loading and recovery strategies. LEVEL OF EVIDENCE: 3.

THE RELATIONSHIP OF RANGE OF MOTION, HIP SHOULDER SEPARATION, AND PITCHING KINEMATICS.

BACKGROUND: When pitching a baseball, pelvic and trunk pitching kinematics play an integral role in momentum transfer from the lower extremity to the upper extremity. However, it is unknown how hip and trunk ROM and hip shoulder separation interplay with pelvic and trunk pitching kinematics. HYPOTHESIS/PURPOSE: To determine the relationship between clinical trunk and hip range of motion (ROM) and pitching biomechanical pelvis and trunk kinematics, and kinematic sequencing. STUDY DESIGN: Controlled biomechanical study. METHODS: High school pitchers were assessed for trunk rotation via motion capture and hip ROM via a goniometer prior to pitching. Trunk rotation was designated as dominant and non-dominant sides, and hips as stance and lead limbs. Pitchers threw four fastballs during three dimensional biomechanical assessment. Spearman's Rho correlations were performed between trunk and hip ROM, and trunk and hip biomechanical kinematics, and kinematic pitching sequence. RESULTS: Thirty-two pitchers (mean age: 16.3 ± 1.2 years, height = 184.0 ± 6.9 cm, mass = 76.8 ± 20.8 kg) were included in this study. Their mean pitch velocity was 34.7 ± 2.3 m/s, peak pelvis rotation velocity: 669.1 ± 95.5 deg/s, and peak trunk rotation velocity: 1084.7 ± 93.0 deg/s. There were no differences between dominant and non-dominant side trunk rotation, or between stance and lead hip ROM. There were no significant relationships between trunk or hip ROM and pitching kinematics. There was a significant relationship between hip shoulder separation and peak trunk rotation velocity (r = 0.390, p=0.027). There was a significant relationship between pitch velocity and peak trunk rotation velocity (r = 0.478, p = 0.006). There were no other significant relationships between pitching kinematics or kinematic sequencing. CONCLUSION: Hip shoulder separation is related to trunk rotation velocity, and ultimately pitch velocity. These ROM measurements can be used as normative values for hip shoulder separation in high school pitchers. LEVEL OF EVIDENCE: 3.

The relationship between pitch velocity and shoulder distraction force and elbow valgus torque in collegiate and high school pitchers.

BACKGROUND: The relationship between pitch velocity, shoulder distraction force, and elbow valgus torque is not well understood. The purpose of this study was to (1) determine the association between baseball pitch velocity and shoulder distraction force and (2) determine the association between baseball pitch velocity and elbow valgus torque. A subpurpose was to determine these same associations within subgroups of college baseball and high school baseball pitchers. METHODS: Collegiate and high school baseball pitchers were biomechanically analyzed; variables extracted from the pitching reports included fastball pitch velocity, shoulder distraction force, and elbow valgus torque. Linear regression was performed to analyze the relationship between fastball velocity and shoulder and elbow kinetics. Subgroup analyses were then performed for college and high school pitches. Coefficients and 95% confidence intervals (95% CI) were calculated, with R squared (r2) used to assess model fit. RESULTS: A total of 70 pitchers (college: n = 23; high school: n = 47) were included in this study. There was a positive weak linear relationship between pitch velocity and shoulder distraction force (3.24 %body weight [BW] [95% CI: 2.07, 4.40], r2 = 0.32, P < .001) and elbow valgus torque (0.16 %body weight × height [BW × H] [95% CI: 0.11, 0.20], r2 = 0.44, P < .001). College pitchers did not exhibit a relationship between pitch velocity and shoulder distraction force (1.44 %BW [95% CI: -2.50, 5.38], r2 = 0.02, P < .001), whereas high school pitchers did exhibit a weak positive linear relationship between pitch velocity and shoulder distraction force (3.69 %BW [95% CI: 2.25, 5.14], r2 = 0.36, P < .001). Both college and high school pitchers exhibited a weak positive relationship between pitch velocity and elbow valgus torque (college: 0.15 %BW × H [95% CI: 0.05, 0.25], r2 = 0.29, P < .001; high school: 0.16 %BW × H [95% CI: 0.09, 0.22], r2 = 0.36, P < .001). DISCUSSION: Pitching velocity exhibited a weak positive linear relationship with both shoulder distraction force and elbow valgus torque. However, only high school pitchers were observed to have a weak positive linear relationship between pitch velocity and shoulder distraction force, whereas both college and high school pitchers exhibited a weak positive relationship between pitch velocity and elbow valgus torque. These findings suggest that older pitchers may attenuate shoulder forces with increased pitch velocity due to physical maturity or increased pitching mechanical skill in comparison with younger pitchers.