Effect of Forearm Position on Glenohumeral External Rotation Measurements in Baseball Players

2021 ◽  
pp. 194173812110329
Author(s):  
W. Ben Kibler ◽  
Aaron Sciascia ◽  
John Stuart Mattison Pike ◽  
Michael Howell ◽  
Kevin E. Wilk
Keyword(s):  
Injury Risk ◽  
External Rotation ◽  
Level Of Evidence ◽  
Cross Sectional ◽  
Baseball Players ◽  
Minor League Baseball ◽  
Minor League ◽  
Level 3 ◽  
Motion Measurements ◽  
Throwing Motion

Background: Alterations in glenohumeral internal rotation (GIR), glenohumeral external rotation (GER), and the total arc of motion (TAM) have been linked with increased injury risk in the shoulder and elbow. These motions have been routinely measured with the forearm in neutral rotation (GIRN, GERN, TAMN). GER capacity appears to be especially important. The throwing motion, however, requires forearm pronation as GER occurs to achieve optimal cocking (GERP). No previous studies have evaluated GERP to determine GER capacity or pronated TAM (TAMP) values. Hypothesis: There would be significant differences between GERN and TAMN and between GERP and TAMP. Study Design: Cross-sectional. Level of Evidence: Level 3. Methods: Sixty asymptomatic male Minor League Baseball players (32 pitchers, 28 position players) participated in the study and were tested on the first day of spring training. Passive range of motion measurements were recorded using a long-arm bubble goniometer for GIRN, GERN, and GERP on both arms. TAM was calculated separately as the sum of internal and external rotational measurements under neutral and pronated conditions. Results: Within pitchers and position players, all measurements were statistically reduced for the throwing arm ( P ≤ 0.03) except for GERN of the pitchers. GERP measures were significantly less than GERN for both arms of each group ( P < 0.01): pitchers throwing arm +11.8°/nonthrowing arm +4.8°, position players throwing arm = +8.6°/nonthrowing arm +4.0°. Conclusion: The forearm position of pronation, which appears to be mediated by tightness of the biceps, decreases GER capacity and TAM. GER and TAM should be calculated in neutral and pronated positions, considering that 80% of the players have a demonstrated difference between 8° and 12°. Clinical Relevance: Measurement of GERP more accurately reflects the GER required in throwing, allows better quantification of the motion capacity necessary to withstand the loads in throwing, and may suggest interventions for at risk athletes.

scholarly journals The Relationship Between Humeral Torsion and Arm Injury in Baseball Players: A Systematic Review and Meta-analysis

2020 ◽  
Vol 12 (2) ◽  
pp. 132-138
Author(s):  
Joshua K. Helmkamp ◽  
Garrett S. Bullock ◽  
Allison Rao ◽  
Ellen Shanley ◽  
Charles Thigpen ◽  
...  
Keyword(s):  
High School ◽  
Systematic Review ◽  
Injury Risk ◽  
External Rotation ◽  
Level Of Evidence ◽  
Baseball Players ◽  
Shoulder Range Of Motion ◽  
Competition Level ◽  
Humeral Torsion ◽  
The Relationship

Context: Humeral torsion (HT) has been linked to various injuries and benefits. However, the exact interplay between HT, shoulder range of motion (ROM), competition level differences, and injury risk is unclear. Objective: To determine the relationship between HT, ROM, and injury risk in baseball players. Secondarily, to determine HT based on competition level. Data Sources: PubMed, Embase, Web of Science, CINAHL, and Cochrane databases were searched from inception until November 4, 2018. Study Selection: Inclusion criteria consisted of (1) HT measurements and (2) arm injury or shoulder ROM. Study Design: Systematic review. Level of Evidence: Level 3. Data Extraction: Two reviewers recorded patient demographics, competition level, HT, shoulder ROM, and injury data. Results: A total of 32 studies were included. There was no difference between baseball players with shoulder and elbow injuries and noninjured players (side-to-side HT difference: mean difference [MD], 1.75 [95% CI, –1.83 to 2.18]; dominant arm: MD, 0.17 [95% CI, –1.83 to 2.18]). Meta-regression determined that for every 1° increase in shoulder internal rotation (IR), there was a subsequent increase of 0.65° in HT (95% CI, 0.28 to 1.02). HT did not explain external rotation (ER ROM: 0.19 [95% CI, –0.24 to 0.61]) or horizontal adduction (HA ROM: 0.18 [95% CI, –0.46 to 0.82]). There were no differences between HT at the high school, college, or professional levels. Conclusion: No relationship was found between HT and injury risk. However, HT explained 65% of IR ROM but did not explain ER ROM or HA ROM. There were no differences in HT pertaining to competition level. The majority of IR may be nonmodifiable. Treatment to restore and maintain clinical IR may be important, especially in players with naturally greater torsion. HT adaptation may occur prior to high school, which can assist in decisions regarding adolescent baseball participation.

scholarly journals Differences in Lower Extremity Movement Quality by Level of Sport Specialization in Cadets Entering a United States Service Academy

2021 ◽  
pp. 194173812199409
Author(s):  
CPT Connor B. Venrick ◽  
Story F. Miraldi ◽  
Lindsay J. DiStefano ◽  
Karen Y. Peck ◽  
LTC Matthew A. Posner ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Injury Risk ◽  
Level Of Evidence ◽  
Cross Sectional ◽  
Movement Quality ◽  
Youth Athletes ◽  
Increased Risk ◽  
Level 3 ◽  
Service Academy ◽  
Sectional Analysis

Background: Sport specialization in youth athletes is associated with increased risk for musculoskeletal injury; however, little is known about whether sport specialization is associated with lower extremity movement quality. The purpose of this study was to examine differences in lower extremity movement quality by level of sport specialization in US Service Academy cadets. Hypothesis: Cadets who report an increased level of sport specialization would have a lower level of movement quality than those who are less specialized. Study Design: Cross-sectional analysis from an ongoing prospective cohort study. Level of Evidence: Level 3. Methods: Cadets completed the Landing Error Scoring System (LESS) and a baseline questionnaire evaluating level of sport specialization during high school. Data were analyzed using separate 1-way analysis of variance models. Results: Among all participants (n = 1950), 1045 (53.6%) reported low sport specialization, 600 (30.8%) reported moderate sport specialization, and 305 (15.6%) reported high sport specialization at the time of data collection during the first week. Ages ranged from 17 to 23 years. Men (1491) and women (459) reported comparable specialization levels ( P = 0.45). There were no statistically significant differences in lower extremity movement quality by level of specialization for all subjects combined ( P = 0.15) or when only men were included in the analyses ( P = 0.69). However, there were statistically significant differences in movement quality by level of specialization in women ( P = 0.02). Moderately specialized women had the best movement quality (mean, 4.63; SD, 2.21) followed by those with high specialization (mean, 4.90; SD, 2.08) and those with low levels of specialization (mean, 5.23; SD, 2.07). Conclusion: Women reporting moderate sport specialization had improved movement quality and significantly better LESS scores compared to those with high/low specialization. Clinical Relevance: Athletes, especially women, should be encouraged to avoid early sport specialization to optimize movement quality, which may affect injury risk.

scholarly journals The Influence of Asymptomatic Hypermobility on Unanticipated Cutting Biomechanics

2021 ◽  
pp. 194173812199906
Author(s):  
Ivana Hanzlíková ◽  
Jim Richards ◽  
Josie Athens ◽  
Kim Hébert-Losier
Keyword(s):  
Injury Risk ◽  
External Rotation ◽  
Cruciate Ligament ◽  
Joint Hypermobility ◽  
Mean Difference ◽  
Initial Contact ◽  
Level Of Evidence ◽  
Cross Sectional ◽  
Acl Injuries ◽  
Peak Knee

Background: Generalized joint hypermobility is an important risk factor for knee injuries, including to the anterior cruciate ligament (ACL). Examining movement patterns specific to hypermobile individuals during sport-specific movements could facilitate development of targeted recommendations and injury prevention programs for this population. Hypothesis: Asymptomatic hypermobile participants will present kinematics measures suggestive of a greater risk of noncontact knee or ACL injuries. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: Forty-two (15 asymptomatic hypermobile and 27 nonhypermobile) individuals performed unanticipated side-step cutting on their dominant and nondominant legs. Ankle, knee, hip, pelvis, and trunk angles in all planes of motion were collected during the first 100 ms after initial contact using a 3-dimensional infrared system. Precontact foot-ground angles were also extracted. Data from hypermobile and nonhypermobile groups were compared using multiple regression models with sex as a confounder. When nonsignificant, the confounder was removed from the model. Effect sizes (Hedge g) were calculated in the presence of significant between-group differences. Results: Hypermobile individuals presented with lower minimum knee valgus angles with a mean difference of 3.5° ( P = 0.03, Hedge g = 0.69) and greater peak knee external rotation angles with a mean difference of −4.5° ( P = 0.04, Hedge g = 0.70) during dominant leg cutting, and lower peak ankle plantarflexion angles with a mean difference of 4.5° ( P = 0.03, Hedge g = 0.73) during nondominant leg cutting compared with nonhypermobile individuals. Conclusions: Based on current scientific evidence, however, the identified differences are not crucial biomechanical injury risk factors that could predispose asymptomatic hypermobile individuals to noncontact knee or ACL injuries. Clinical Relevance: Further research is needed to highlight differences between hypermobility groups. Knowledge of the differences between these groups may change the physical activity recommendations, prevention of injury, and rehabilitation approaches.

scholarly journals Prevalence and Consequences of Sport Specialization Among Little League Baseball Players

2021 ◽  
pp. 194173812097095
Author(s):  
Eric G. Post ◽  
Michael D. Rosenthal ◽  
Andrew T. Pennock ◽  
Mitchell J. Rauh
Keyword(s):  
Cross Sectional Study ◽  
Patient Reported Outcome ◽  
Online Questionnaire ◽  
Level Of Evidence ◽  
Cross Sectional ◽  
Baseball Players ◽  
Little League ◽  
Patient Reported ◽  
Youth Baseball ◽  
Level 3

Background: Baseball is one of the most popular boy’s youth sports, and there has been a rise in the rates of certain overuse injuries among players. Specialization has been identified as a risk factor for overuse injury in high school athlete populations, but there is little understanding of the prevalence or consequences of sport specialization in Little League baseball players. Hypothesis: Sport specialization will be highly prevalent among Little League baseball players and specialization will be associated with worse throwing arm health. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: A total of 246 Little League baseball players (male; N = 241; age, 9.5 ± 1.6 years) between 7 and 12 years old completed an anonymous, online questionnaire with their parent’s assistance. The questionnaire consisted of participant demographics and baseball participation information, including sport specialization status and the Youth Throwing Score (YTS), a valid and reliable patient-reported outcome measure for youth baseball players. Results: Only 29 (11.8%) players met the criteria for high specialization. Approximately one-third of all players (n = 77; 31.3%) reported participating in baseball year-round or receiving private coaching outside of their league (n = 81; 32.9%). Highly specialized athletes demonstrated worse scores on the YTS on average compared with low-specialization athletes (mean [SE]: 56.9 [1.6] vs 61.1 [1.2]; P = 0.01). Similarly, pitching in the previous year ( P < 0.01) or traveling overnight regularly for showcases ( P = 0.01) were associated with a worse score on the YTS. Conclusion: While the prevalence of high sport specialization was low among Little League baseball players, other behaviors associated with specialization such as year-round play and the receiving of private coaching were more common. Highly specialized Little League players demonstrated worse throwing arm health compared with low-specialization players. Clinical Relevance: Little League players and their parents may represent a potential target audience for dissemination campaigns regarding sport specialization.

scholarly journals Exceeding Pitch Count Recommendations in Little League Baseball Increases the Chance of Requiring Tommy John Surgery as a Professional Baseball Pitcher

2017 ◽  
Vol 5 (3) ◽  
pp. 232596711769508 ◽  
Author(s):  
Brandon J. Erickson ◽  
Peter N. Chalmers ◽  
Michael J. Axe ◽  
Anthony A. Romeo
Keyword(s):  
Ulnar Collateral Ligament ◽  
Professional Baseball ◽  
Level Of Evidence ◽  
Baseball Players ◽  
Minor League Baseball ◽  
Elbow Injury ◽  
World Series ◽  
Little League ◽  
Minor League ◽  
Tommy John

Background: Empirical evidence has suggested a connection between youth pitch counts and subsequent elbow injury. For players within the Little League World Series (LLWS), detailed historical player data are available. Some of these players progress to both professional play and require an ulnar collateral ligament reconstruction (UCLR). Purpose: To determine the percentage of LLWS pitchers who proceed to play professional (major or minor league) baseball, the rate of UCLR in former LLWS pitchers who played professional baseball, and the risk to those who exceeded current pitch count recommendations while playing in the LLWS. Study Design: Cohort study; Level of evidence, 3. Methods: All LLWS pitchers from 2001 through 2009 from all teams and countries were identified, and all performance data were extracted. A professional (major and minor league) baseball database was then searched to determine whether each former LLWS pitcher played professional baseball. These professional players were then searched for using publicly available databases to determine whether they underwent UCLR. Results: Overall, 638 adolescents pitched in the LLWS between 2001 and 2009; 62 (10%) progressed to professional play. Of the 56 minor league players, 25 (45%) pitched. Of the 6 Major League Baseball players, 3 (50%) pitched. Three former LLWS pitchers (5%) who played professionally underwent UCLR. In former LLWS pitchers who exceeded pitch counts and played professionally, 50% (2/4) required UCLR, while only 1.7% (1/58) of those who did not exceed pitch count recommendations required UCLR ( P = .009). Similarly, among former LLWS pitchers who subsequently played professionally, 23.1% of those who played as a pitcher required UCLR while 0% of those who also played other positions required UCLR ( P = .008). Conclusion: Progression from LLWS pitching to professional baseball is uncommon. Among youth players, both diversification (playing other positions besides pitcher) as well as following current pitch limit regulations may protect against UCLR.

scholarly journals Comparative Analysis of the Nonoperative Treatment of Elbow Ulnar Collateral Ligament Injuries in Professional Baseball Players with and without Platelet-Rich Plasma

2018 ◽  
Vol 6 (7_suppl4) ◽  
pp. 2325967118S0008 ◽  
Author(s):  
Peter Douglas McQueen ◽  
Christopher L. Camp ◽  
Aakash Chauhan ◽  
Brandon J. Erickson ◽  
Hollis G. Potter ◽  
...  
Keyword(s):  
Recovery Time ◽  
Platelet Rich Plasma ◽  
Ulnar Collateral Ligament ◽  
Nonoperative Treatment ◽  
Return To Play ◽  
Professional Baseball ◽  
Collateral Ligament ◽  
Baseball Players ◽  
Minor League Baseball ◽  
Minor League

Objectives: In the setting of ulnar collateral ligament (UCL) injury, surgical reconstruction of the UCL is not always selected, as it leads to a prolonged recovery time and return to play rates between 67-95%. To date, there is limited data on outcomes following nonoperative treatment in this population. Orthobiologics, such as platelet-rich plasma (PRP), have recently been used as an adjunct therapy for standard nonoperative treatment including rest and physical therapy for UCL injuries. The objective of this study was to determine if the addition of PRP injections in professional baseball players with UCL injuries reduces recovery time, lowers the likelihood of surgery, and increases the return to play rate compared to traditional nonoperative treatment. Methods: The Health and Injury Tracking System (HITS) database was searched from 2011-2015 for Major and Minor league baseball players with Grade I, II or III UCL injuries. Standard demographic, injury, and return to play data was obtained for all players. MRI’s for 353 athletes were reviewed by a musculoskeletal radiologist and graded accordingly. Outcomes were compared between players who received PRP injections in addition to traditional nonoperative treatment (PRP group) and players who received traditional nonoperative treatment alone (No PRP group). Statistical analysis was performed using Student’s T-test and Chi-square for parametric data. Kaplan Meier’s analysis was used for estimating longevity of the treatment. Results: A total of 544 Major and Minor League Baseball players with UCL tears underwent an initial course of nonoperative treatment (active rest & rehabilitation) for their injury between 2011-2015. Of these, 133 underwent PRP injections plus rehab and 411 underwent rehab alone. There was a significantly higher proportion of Major League Baseball players in the PRP group compared to the No PRP group (25.6% vs 9.0%, P<0.001). There was no difference between the two cohorts in regard to the grade of UCL tear (Figure 1). The players in the PRP group had a significantly longer time before returning to a throwing program compared to the No PRP group (64 days vs 51 days, P<0.001). The mean time from injury date to PRP injection was 14.5 days, which may explain the difference in time to return to throwing. The return to play rate in a live game without surgery was significantly lower in the PRP group compared to the No PRP group (46% vs 57%, P=0.03). There was no difference in the proportion of athletes requiring UCL reconstruction (58% vs 51%) or the time to surgery (154 days vs 178 days) between the two groups. Kaplan Meier survivor analysis showed no difference between the PRP and No PRP groups with regard to longevity of the native UCL (Figure 2). Conclusion: Among Major and Minor League Baseball players who were treated nonoperatively for a UCL injury between 2011-2015, 24% underwent PRP injections prior to rehab. Compared to traditional nonoperative rehab alone program, players who received PRP injections experienced a significantly longer time before returning to throwing, which may be in part due to the delay between the injury date and PRP injection. PRP injections did not appear to have a significant effect on the likelihood of surgical intervention.

scholarly journals The Impact of Workload on the Evolution of Hip Internal and External Rotation in Professional Baseball Players Over the Course of the Season

2018 ◽  
Vol 6 (2) ◽  
pp. 232596711775210 ◽  
Author(s):  
Christopher L. Camp ◽  
John M. Zajac ◽  
Dave Pearson ◽  
Dean Wang ◽  
Alec S. Sinatro ◽  
...  
Keyword(s):  
External Rotation ◽  
Professional Baseball ◽  
Level Of Evidence ◽  
Baseball Players ◽  
Increased Risk ◽  
Hip Range Of Motion ◽  
Hip Motion ◽  
Hip Internal Rotation ◽  
Loss Of Motion ◽  
The Impact

Background: Although restricted hip range of motion (ROM) is associated with an increased risk for injuries in baseball players, the evolution of hip ROM over the season remains undefined. Hypothesis: Hip ROM profiles would be symmetric between hips and positions (pitchers vs position players) but would decrease from preseason to postseason. Additionally, it was hypothesized that this decrease in motion would correlate with workload. Study Design: Cohort study; Level of evidence, 2. Methods: Bilateral hip ROM was assessed in 96 professional baseball players (54 pitchers, 42 position players) preseason and postseason. ROM comparisons were made between lead and trailing hips, pitchers and position players, and preseason and postseason measures. The change from preseason to postseason was correlated with player demographics and measures of workload for pitchers and position players. Results: Preseason hip ROM was symmetric between hips; however, pitchers demonstrated increased preseason lead hip internal rotation (IR) ( P = .018) and bilateral hip total ROM (TROM) ( P < .020) compared with position players. From preseason to postseason, position players lost 7° of external rotation (ER) ( P ≤ .005 ). In pitchers, the loss of IR correlated with increased pitches ( P = .016) and innings ( P = .037), while the loss of ER ( P = .005 ) and TROM ( P = .014) correlated with increasing mean fastball velocity. Workload for position players did not correlate with motion loss. Conclusion: Symmetric hip ROM profiles should be anticipated in baseball players; however, pitchers may have increased preseason IR and TROM and postseason ER and TROM relative to position players. Although loss of motion correlated with workload in pitchers, this was not the case for position players. Hip motion should be monitored over the course of the season. This is particularly true for pitchers who lose IR as workload increases, which may place them at a greater risk for injuries.

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

2019 ◽  
Vol 48 (2) ◽  
pp. 481-487
Author(s):  
Justin M. Chan ◽  
John Zajac ◽  
Brandon J. Erickson ◽  
David W. Altchek ◽  
Christopher Camp ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Range Of Motion ◽  
External Rotation ◽  
Significant Risk ◽  
Case Series ◽  
Significant Risk Factor ◽  
Professional Baseball ◽  
Level Of Evidence ◽  
Baseball Players ◽  
Shoulder Flexion

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.

scholarly journals Shoulder Range of Motion and Baseball Arm Injuries: A Systematic Review and Meta-Analysis

2018 ◽  
Vol 53 (12) ◽  
pp. 1190-1199 ◽  
Author(s):  
Garrett S. Bullock ◽  
Mallory S. Faherty ◽  
Leila Ledbetter ◽  
Charles A. Thigpen ◽  
Timothy C. Sell
Keyword(s):  
Range Of Motion ◽  
External Rotation ◽  
Meta Analysis ◽  
P Value ◽  
High Quality ◽  
Level Of Evidence ◽  
Baseball Players ◽  
Shoulder Range Of Motion ◽  
Methodologic Quality ◽  
Arm Injuries

Objective Arm injuries in baseball players are a common problem. The identification of modifiable risk factors, including range of motion (ROM), is essential for injury prevention. The purpose of this review was to assess the methodologic quality and level of evidence in the literature and to investigate the relationship between shoulder ROM and the risk of arm injuries in baseball players. Data Sources Relevant studies in PubMed, CINAHL, Embase, and SPORTDiscus published from inception to August 1, 2017. Study Selection Only studies that encompassed healthy baseball cohorts who were assessed for shoulder ROM and prospectively evaluated for injuries throughout a baseball season or seasons were included. Data Extraction Six articles met the search criteria. Only 3 studies were included in the meta-analysis due to disparate participant groups. Data Synthesis The modified Downs and Black scale (0–15 points) was used to analyze methodologic quality. Study quality ranged from 11 to 14. Four studies received high-quality (≥12) and 2 studies received moderate-quality (≥10) scores. The overall pooled analysis demonstrated that absolute and internal-rotation deficits (–5.93 [95% confidence interval {CI} = –9.43, –2.43], P &lt; .001 and 4.28 [0.71, 7.86], P = .02, respectively) and absolute total ROM (TROM; –6.19 [95% CI = –10.28, –2.10]; P = .003) were predictors of injury, and these data exhibited homogeneity (absolute IR P value = .77, I2 = 0%; IR deficit P value = .41, I2 = 0%; absolute TROM P value = .78, I2 = 0%). No significance was observed for absolute external rotation (–2.86 [95% CI = –6.56, 0.83], P = .13), which had data with high heterogeneity (P = .003; I2 = 83%). A deficit in horizontal adduction was a predictor of injury (–8.32 [95% CI = –12.08, –4.56]; P &lt; .001); these data were homogeneous but yielded a moderate heterogenic effect (P = .16; I2 = 50%). Conclusions High-quality evidence demonstrated that deficits in throwing-arm TROM and IR were associated with upper extremity injury in baseball players. Heterogeneity across studies for horizontal adduction suggested that this may be a modifiable risk factor for injury, but it requires further research.

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