Pool-Based Surfboard Elicits Activation of Posterior Shoulder Muscles During a Surfing Stroke.

ABSTRACT: Pexa, BS, Johnston, CD, Elder, EE, Ford, KR, Patterson, MQ, and Myers, JB. Pool-based surfboard elicits activation of posterior shoulder muscles during a surfing stroke. J Strength Cond Res 38(7): 1300-1304, 2024-Surfboard paddling may activate posterior shoulder muscles, which are critical to baseball pitchers' injury risk and performance. The purpose of this study was to measure posterior shoulder muscle activation during different phases of the surf stroke (propulsion vs. recovery) on a pool-based surfboard. Twenty healthy active adult subjects completed a familiarization and testing session with the pool-based surfboard. During the testing session, electromyography (EMG) sensors were placed on 6 posterior shoulder muscles: latissimus dorsi, infraspinatus, posterior deltoid, upper trapezius, middle trapezius, and lower trapezius. Subjects completed 4 laps in a pool at 3 separate resistances (low, moderate, and heavy) in a randomized order. The peak EMG signal during each phase (propulsion and recovery) was recorded. A 2-way within subject ANOVA (resistance-by-phase) with post hoc Bonferroni's corrections was used to identify differences in EMG activation. There was a significant main effect of phase for the latissimus dorsi (F = 91.3, p < 0.001), upper trapezius (F = 36.5, p < 0.001), middle trapezius (F = 33.8, p < 0.001), and lower trapezius (F = 21.6, p < 0.001). The latissimus dorsi demonstrated higher activation during the propulsion phase (p < 0.001), and all trapezius muscles demonstrated higher activation during the recovery phase (p < 0.001). There was a significant main effect of resistance for the posterior deltoid (F = 3.4, p = 0.043), with higher muscle activation in the low resistance trials compared with the heavy resistance trials (p = 0.036). Recreationally active individuals demonstrate activation of the posterior shoulder when using a pool-based surfboard. This pool-based surfboard may be beneficial to activate the posterior musculature and may be more accessible than standard surfing to baseball athletes.

Influence of Baseball Training Load on Clinical Reach Tests and Grip Strength in Collegiate Baseball Players.

CONTEXT: A baseball-specific training load may influence strength or glenohumeral range of motion, which are related to baseball injuries. Glenohumeral reach tests and grip strength are clinical assessments of shoulder range of motion and upper extremity strength, respectively. OBJECTIVE: To examine changes in glenohumeral reach test performance and grip strength between dominant and nondominant limbs and high, moderate, and low baseball-specific training-load groups. DESIGN: Repeated-measures study. SETTING: University laboratory and satellite clinic. PATIENTS OR OTHER PARTICIPANTS: Collegiate baseball athletes (n = 18, age = 20.1 ± 1.3 years, height = 185.0 ± 6.5 cm, mass = 90.9 ± 10.2 kg). MAIN OUTCOME MEASURE(S): Participants performed overhead reach tests (OHRTs), behind-the-back reach tests (BBRTs), and grip strength assessments using the dominant and nondominant limbs every 4 weeks for 16 weeks. Percentage change scores were calculated between testing times. After each training session, participants provided their duration of baseball activity, throw count, and body-specific and arm-specific ratings of perceived exertion. We classified them in the high, moderate, or low training-load group based on each training-load variable: body-specific acute:chronic workload ratio (ACWR), arm-specific ACWR, body-specific cumulative load, and arm-specific cumulative load. Mixed models were used to compare training-load groups and limbs. RESULTS: The arm-specific ACWR group demonstrated as main effect for OHRT (F = 7.70, P = .001), BBRT (F = 4.01, P = .029), and grip strength (F = 8.89, P < .001). For the OHRT, the moderate training-load group demonstrated a 10.8% greater increase than the high group (P = .004) and a 13.2% greater increase than the low group (P < .001). For the BBRT, the low training-load group had a 10.1% greater increase than the moderate group (P = .011). For grip strength, the low training-load group demonstrated a 12.1% greater increase than the high group (P = .006) and a 17.7% greater increase than the moderate group (P < .001). CONCLUSIONS: Arm-specific ACWR was related to changes in clinical assessments of range of motion and strength. Clinicians may use arm-specific ACWR to indicate when a baseball athlete's physical health is changing.

Variability in the identification and reporting of overuse injuries among sports injury surveillance data collectors.

PURPOSE: This study examined variability in identifying and reporting overuse injuries among Certified Athletic Trainers (ATs). METHODS: This cross-sectional study of ATs participating in the National Collegiate Athletic Association's Injury Surveillance Program, utilized a novel online-only survey, consisting of seven hypothetical clinical scenarios representing various clinical presentations including overuse and acute elements. Participants reported clinical opinions regarding the role overuse played in each scenario (major contributor, not a major contributor, not enough information) and probability (0-100%) of classifying each scenario as having an overuse injury mechanism, then completed open-ended questions addressing their decision-making process. RESULTS: 74 ATs (25%) completed the survey. Six of the seven scenarios generated discordance in responses among the participating ATs. Variability in AT decisions involved: the progression of injury, duration of symptoms, and activity at time of injury. CONCLUSION: Developing a formalized definition of overuse injury may improve consistency and standardize methods for identifying and reporting overuse injuries within injury research.

Infraspinatus Cross-Sectional Area and Shoulder Range of Motion Change Following Live-Game Baseball Pitching.

CONTEXT: Following a baseball pitching bout, changes can occur to glenohumeral range of motion that could be linked to injury. These effects are in part due to the posterior shoulder's eccentric muscle activity, which can disrupt muscle contractile elements and lead to changes in muscle cross-sectional area (CSA), as measured by ultrasound. OBJECTIVE: To assess changes in muscle CSA, and range of motion immediately before and after pitching, and days 1 to 5 following pitching. DESIGN: Repeated measures. SETTING: Satellite athletic training room. PATIENTS: Ten elite college baseball pitchers participating in the fall season (age: 18.8 [1.2] y, height: 189.2 [7.3] cm, mass: 93.1 [15.3] kg, 8 starters, 2 long relievers). INTERVENTION: A pitching bout of at least 25 pitches (63.82 [17.42] pitches). MAIN OUTCOME MEASURES: Dominant and nondominant infraspinatus CSA, as measured by ultrasound, and glenohumeral range of motion including internal rotation (IRROM), external rotation (ERROM), and total rotation range of motion (TROM) before pitching, after pitching, and days 1 to 5 following the pitching bout. RESULTS: Dominant limb CSA significantly increased day 1 after pitching, and returned to baseline on day 2 (P < .001). Dominant and nondominant TROM did not change until day 5 (4.4°, P < .001) and day 3 (4.5°, P < .001), respectively, where they increased. Dominant IRROM was significantly decreased for 3 days (day 1: 1.9°, P < .001; day 2: 3.1°, P < .001; day 3: 0.3°, P < .001) following pitching and returned to baseline on day 4, with no such changes in the nondominant limb. Dominant external rotation significantly increased immediately post pitching (4.4°, P < .001) but returned to baseline by day 1. CONCLUSIONS: The results of the study demonstrate that infraspinatus CSA does not recover until 2 days following pitching, and IRROM does not recover until 4 days following pitching. Baseball pitching elicits damage to the posterior shoulder muscle architecture, resulting in changes to physical characteristics that last up to 4 days following pitching.

Rate of Upper Extremity Injury in High School Baseball Pitchers Who Played Catcher as a Secondary Position.

CONTEXT: Many high school pitchers play another position after they have finished pitching for the day or on their rest days from pitching. Because of the cumulative demands on the arm, pitchers who also play catcher may have a greater risk of developing a throwing-related shoulder or elbow injury. OBJECTIVE: To compare the rate of throwing-related upper extremity injuries between high school baseball pitchers who also played catcher as a secondary position and those who did not play catcher. DESIGN: Prospective cohort study. SETTING: Field laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 384 male high school baseball pitchers were recruited from 51 high school teams. Pitchers who reported their secondary position as catcher were classified into the pitcher/catcher group and those who did not report playing catcher as a secondary position were classified into the other group. MAIN OUTCOME MEASURE(S): Participants completed a demographic questionnaire preseason and then athlete participation and injury status were tracked during the subsequent season. Athlete-exposures were monitored and the shoulder and elbow injury proportion rates were calculated. RESULTS: Athlete-exposures did not differ between groups ( P = .488). The pitcher/catcher group's risk of shoulder or elbow injury was 2.9 times greater than that of the other pitchers (15% versus 5%; injury proportion rate = 2.9; 95% confidence interval = 1.03, 8.12). CONCLUSIONS: Pitchers who reported also playing catcher were at a greater risk of sustaining a throwing-related shoulder or elbow injury than the other pitchers. These findings suggest that pitchers should consider not playing catcher as their secondary position in order to allow adequate time for recovery and to decrease their overall throwing load. Serial physical examinations of pitchers/catchers during the season may be useful in determining if their physical characteristics are changing during the season because of the cumulative throwing load.

Medial Elbow Joint Space Increases With Valgus Stress and Decreases When Cued to Perform A Maximal Grip Contraction.

BACKGROUND: Previous research indicates that the amount of valgus torque placed on the elbow joint during overhead throwing is higher than the medial ulnar collateral ligament (UCL) can tolerate. Wrist and finger flexor muscle activity is hypothesized to make up for this difference, and in vitro studies that simulated activity of upper extremity musculature, specifically the flexor digitorum superficialis and flexor carpi ulnaris, support this hypothesis. PURPOSE: To assess the medial elbow joint space at rest, under valgus stress, and under valgus stress with finger and forearm flexor contraction by use of ultrasonography in vivo. STUDY DESIGN: Controlled laboratory study. METHODS: Participants were 22 healthy males with no history of elbow dislocation or UCL injury (age, 21.25 ± 1.58 years; height, 1.80 ± 0.08 m; weight, 79.43 ± 18.50 kg). Medial elbow joint space was measured by use of ultrasonography during 3 separate conditions: at rest (unloaded), under valgus load (loaded), and with a maximal grip contraction under a valgus load (loaded-contracted) in both limbs. Participants lay supine with their arm abducted 90° and elbow flexed 30° with the forearm in full supination. A handgrip dynamometer was placed in the participants' hand to grip against during the contracted condition. Images were reduced in ImageJ to assess medial elbow joint space. A 2-way (condition × limb) repeated-measures analysis of variance and Cohen's d effect sizes were used to assess changes in medial elbow joint space. Post hoc testing was performed with a Bonferroni adjustment to assess changes within limb and condition. RESULTS: The medial elbow joint space was significantly larger in the loaded condition (4.91 ± 1.16 mm) compared with the unloaded condition (4.26 ± 1.23 mm, P < .001, d = 0.712) and the loaded-contracted condition (3.88 ± 0.94 mm, P < .001, d = 1.149). No significant change was found between the unloaded and loaded-contracted conditions ( P = .137). CONCLUSION: Medial elbow joint space increases under a valgus load and then decreases when a maximal grip contraction is performed. This indicates that wrist and finger flexor muscle contraction may assist in limiting medial elbow joint space, a result similar to findings of previous research in vitro. CLINICAL RELEVANCE: Muscle activation of the upper extremity limits the medial elbow joint space, suggesting that injury prevention programs for throwing athletes should incorporate exercises for the elbow, wrist, and hand to limit excessive medial elbow joint space gapping during activities that create high valgus load.

Capture of Time-Loss Overuse Soccer Injuries in the National Collegiate Athletic Association's Injury Surveillance System, 2005-2006 Through 2007-2008.

CONTEXT: Overuse injuries are reported to account for nearly 50% of sports injuries and, due to their progressive nature and the uncertainty regarding date of onset, are difficult to define and categorize. Comparing the capture rates of overuse injuries between injury-surveillance systems and medical records can clarify completeness and determinants of how overuse injuries are represented in injury-surveillance data. OBJECTIVE: To estimate the capture rate of time-loss medical-attention overuse injuries in men's and women's soccer in the National Collegiate Athletic Association Injury Surveillance System (NCAA ISS) compared with medical records maintained by certified athletic trainers and assess the differences in completeness of capture and factors contributing to those differences. DESIGN: Capture-recapture study. SETTING: Fifteen NCAA institutions provided NCAA ISS and medical record data from men's and women's soccer programs from 2005-2006 through 2007-2008. PATIENTS OR OTHER PARTICIPANTS: National Collegiate Athletic Association men's and women's soccer players. MAIN OUTCOME MEASURE(S): Time-loss medical-attention overuse injuries were defined as injuries with an overuse mechanism of injury in the NCAA ISS or medical records. Capture rates were calculated as the proportion of total overuse injuries classified as having overuse mechanisms in the NCAA ISS and the NCAA ISS and medical records combined. RESULTS: The NCAA ISS captured 63.7% of the total estimated overuse mechanisms of injury in men's and women's soccer players. The estimated proportion of overuse injury mechanisms captured by both the NCAA ISS and medical records was 37.1%. The NCAA ISS captured more overuse injury mechanisms in men's soccer than in women's soccer (79.2% versus 45.0%, χ2 = 9.60; P = .002) athletes. CONCLUSIONS: From 2005-2006 through 2007-2008, the NCAA ISS captured only two thirds of time-loss medical-attention overuse mechanisms of injury in men's and women's soccer players. Future researchers should consider supplementing injury-surveillance data with a clinical record review to capture the burden of these injuries.

The Relationship Between the Push Off Ground Reaction Force and Ball Speed in High School Baseball Pitchers.

Oyama, S and Myers, JB. The relationship between the push off ground reaction force and ball speed in high school baseball pitchers. J Strength Cond Res 32(5): 1324-1328, 2018-Baseball pitching is a sequential movement that requires transfer of momentum from the lower extremity to the throwing arm. Therefore, the ground reaction force (GRF) during push off is suggested to play a role in production of ball speed. The purpose of this study was to investigate the correlation between GRF characteristics during push off and ball speed in high school baseball pitchers. A total of 52 pitchers performed fast pitches from an indoor pitching mound. A force plate embedded in an indoor mound was used to capture the push off GRF. The GRF characteristics (peak anterior, vertical, and resultant forces, vertical and resultant forces at the time of peak anterior GRF, and impulse produced by the anterior GRF) from the 3 fastest strike pitches from each pitcher were used for analyses. Spearman's rank correlation coefficients were used to describe the relationships between ball speed and the GRF characteristics. Ball speed was only weakly correlated with peak resultant force (ρ = 0.32, p = 0.02) and vertical (ρ = 0.45, p < 0.001) and resultant (ρ = 0.42, p = 0.002) forces at the time of peak anterior force. The ball speed was not correlated with other variables. The correlation between ball speed and push off force in high school pitchers was weak, especially when compared with what was reported for adult pitchers in other studies. Unlike for adult pitchers, higher push off force is only weakly correlated with ball velocity in high school pitchers, which suggests that training to better use body momentum may help high school pitchers improve ball speed.

The Influence of Verbal and Tactile Feedback on Electromyographic Amplitude of the Shoulder Musculature During Common Therapeutic Exercises.

CONTEXT: Verbal and tactile feedback (VTF) during rehabilitation exercises can increase muscle activation, thus improving the therapeutic benefits. However, it is unclear which feedback method elicits the greatest electromyographic (EMG) amplitude. OBJECTIVE: To determine if the addition of tactile to verbal feedback (VF) increases EMG amplitude of selected shoulder musculature during scapular plane elevation (Ys), shoulder horizontal abduction with external rotation (Ts), and scapular retraction with external rotation (Ws). DESIGN: Repeated-measures cross-over design. SETTING: Biomechanics laboratory. PARTICIPANTS: A total of 30 physically active adults volunteered for this study-age = 20.23 (1.25) years; height = 1.71 (0.073) m; and mass = 70.11 (15.14) kg. INTERVENTIONS: Electromyography of the serratus anterior; upper, middle, and lower trapezii; and anterior and posterior deltoids was recorded during Ys, Ts, and Ws with VTF and VF alone during separate testing sessions. Participants completed baseline trials without feedback, then received VTF and VF across 2 counterbalanced sessions. MAIN OUTCOME MEASURES: Difference scores were calculated between prefeedback and postfeedback interventions, and the difference score between baseline measurements was used as a control. One-way analysis of variance of the difference scores was used to evaluate the influence of VTF and VF on EMG amplitude during Ys, Ts, and Ws. RESULTS: There was a significant difference between conditions for EMG amplitude of the middle trapezius (F2,28 = 4.09, P = .02) and serratus anterior (F2,28 = 3.91, P = .03) during Ys, the middle trapezius (F2,28 = 7.82, P = .001) during Ws, and the upper (F2,28 = 3.61, P = .03) and middle trapezii (F2,28 = 5.81, P = .01) during Ts. Post hoc testing revealed that both feedback conditions elicited greater EMG amplitude compared with no feedback, but there were no significant differences between the feedback conditions. CONCLUSIONS: The addition of tactile feedback to VF does not increase EMG amplitude compared with VF alone. This study indicates that feedback, regardless of type, is more beneficial than providing no feedback, for increasing EMG amplitude.

Preseason screening of shoulder range of motion and humeral retrotorsion does not predict injury in high school baseball players.

BACKGROUND: Shoulder and elbow injuries are commonplace in high school baseball. Although altered shoulder range of motion (ROM) and humeral retrotorsion angles have been associated with injuries, the efficacy of preseason screening of these characteristics remains controversial. METHODS: We conducted preseason screenings for shoulder internal and external rotation ROM and humeral retrotorsion on 832 high school baseball players and tracked their exposure and incidence on throwing-related shoulder and elbow injuries during a subsequent season. Poisson regression with robust error variance was used to determine whether preseason screening could identify injury risk in baseball players and whether the injury risk was higher for pitchers compared with players who do not pitch. RESULTS: Shoulder rotation ROM or humeral retrotorsion at preseason did not predict the risk of throwing-related upper extremity injury (P = .15-.89). Injury risk was 3.84 higher for baseball players who pitched compared with those who did not (95% confidence interval, 1.72-8.56; P = .001). DISCUSSION: Preseason measures of shoulder ROM and humeral retrotorsion may not be effective in identifying players who are at increased injury risk. Because shoulder ROM is a measure that fluctuates under a variety of influences, future study should investigate whether taking multiple measurements during a season can identify at-risk players. The usefulness of preseason screening may also depend on rigor of participation in sports. Future studies should investigate how preseason shoulder characteristics and participation factors (ie, pitch count and frequency, competitive level, pitching in multiple leagues) interact to predict injury risk in baseball players.

Effect of Swim Training on the Physical Characteristics of Competitive Adolescent Swimmers.

BACKGROUND: Subacromial space distance and forward head and shoulder posture are common characteristics resulting from swim training. These alterations can cause abnormal scapular kinematics and positioning, potentially increasing compression of structures in the subacromial space and increasing the risk for the development of swimmer's shoulder. PURPOSE: To evaluate the effect of the swim training season on subacromial space distance and forward head and forward shoulder posture as well as to determine the relationship between these variables. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Included in the study were 43 competitive adolescent swimmers and 29 nonoverhead adolescent athletes (controls) who were not currently experiencing any shoulder, neck, or back pain that limited their participation in sports activity. All participants were evaluated 3 times: once before the start of the swim training season and then at 2 follow-up sessions 6 and 12 weeks after the initial testing session. At each testing session, each participant completed a physical examination that included evaluation of posture and subacromial space distance. RESULTS: Swimmers had significantly greater decreases in subacromial space distance during the training season compared with nonoverhead athletes. Swimmers also demonstrated significantly greater increases in forward shoulder posture compared with nonoverhead athletes. A significant relationship was noted between changes in forward shoulder posture and changes in subacromial space distance from the baseline testing session to the assessment 6 weeks after baseline assessment. As forward shoulder posture increased, subacromial space significantly decreased. CONCLUSION: Because of their training load, swimmers experience a decrease in subacromial space distance and an increase in forward shoulder posture over the course of 12 weeks of training, potentially making these athletes more vulnerable to the development of shoulder pain and injury.

Comparison of Upper Extremity Physical Characteristics Between Adolescent Competitive Swimmers and Nonoverhead Athletes.

CONTEXT: Alterations to upper extremity physical characteristics of competitive swimmers (posture, range of motion [ROM], and subacromial-space distance) are commonly attributed to cumulative training load during a swimmer's competitive career. However, this accepted clinical belief has not been established in the literature. It is important to understand whether alterations in posture and associated physical characteristics occur as a result of sport training or factors other than swimming participation to better understand injury risk and possible interventions. OBJECTIVE: To compare posture, subacromial-space distance, and glenohumeral external-rotation, internal-rotation, and horizontal-adduction ROM between adolescent competitive swimmers and nonoverhead athletes. DESIGN: Cross-sectional study. SETTING: Local swimming pools and high school athletic training rooms. PATIENTS OR OTHER PARTICIPANTS: Forty-four competitive adolescent swimmers and 31 nonoverhead athletes who were not currently experiencing any elbow, shoulder, neck, or back pain that limited their sport activity. INTERVENTION(S): Posture, subacromial-space distance, and glenohumeral ROM were measured using photography, diagnostic ultrasound, and a digital inclinometer, respectively. MAIN OUTCOME MEASURE(S): Forward shoulder posture, forward head posture, normalized subacromial-space distance, internal-rotation ROM, and external-rotation ROM. RESULTS: No clinically significant differences existed between swimmers and nonoverhead athletes for posture, normalized subacromial-space distance, or external- or internal-rotation ROM. Swimmers presented with less horizontal-adduction ROM than nonoverhead athletes. CONCLUSIONS: Factors other than swimming participation, such as school and technology use, play important roles in the adaptation of physical characteristics in adolescents. Adolescents, regardless of swimming participation, presented with postural deviations. It is important to consider factors other than swimming participation that contribute to alterations in physical characteristics to understand injury risk and injury-prevention strategies in competitive adolescent swimmers.

Epidemiology of Overuse Injuries in Collegiate and High School Athletics in the United States.

BACKGROUND: Overuse injuries result from microtrauma due to repetitive loading combined with insufficient tissue recovery time and can result in both immediate and long-term time loss from sports. HYPOTHESIS: Overuse injury rates and patterns differ across college and high school populations, sport, and sex. STUDY DESIGN: Descriptive epidemiology study. METHODS: Surveillance data for 16 sports from the National Collegiate Athletic Association's Injury Surveillance System (NCAA ISS; 2004-2005 through 2008-2009) and 14 sports from High School Reporting Information Online (High School RIO; 2006-2007 through 2012-2013) were analyzed. All reported injuries had an injury mechanism of overuse/gradual onset (college) or overuse/chronic (high school). Overuse injury incidence rates were calculated, and rate ratios with 95% CIs were used to compare subgroups. RESULTS: The rate of overuse injury was 3.28 times higher in college than high school sports (95% CI, 3.12-3.44). The rate of overuse injury among sex-comparable sports was higher in female than male athletes in both populations (college rate ratio, 1.25; 95% CI, 1.16-1.35; high school rate ratio, 1.55; 95% CI, 1.43-1.68). The lower extremity was the most commonly injured body site (college, 69.4%; high school, 70.4%). A larger proportion of overuse injuries among college athletes resulted in time loss of more than 21 days (college, 20.4%; high school, 7.7%) and surgery (college, 5.2%, high school, 2.5%). CONCLUSION: Overuse injuries can impose a significant burden on college and high school athletes. Interventions addressing prevention of overuse injury are needed.

Factors influencing ball-player impact probability in youth baseball.

BACKGROUND: Altering the weight of baseballs for youth play has been studied out of concern for player safety. Research has shown that decreasing the weight of baseballs may limit the severity of both chronic arm and collision injuries. Unfortunately, reducing the weight of the ball also increases its exit velocity, leaving pitchers and nonpitchers with less time to defend themselves. The purpose of this study was to examine impact probability for pitchers and nonpitchers. HYPOTHESIS: Reducing the available time to respond by 10% (expected from reducing ball weight from 142 g to 113 g) would increase impact probability for pitchers and nonpitchers, and players' mean simple response time would be a primary predictor of impact probability for all participants. STUDY DESIGN: Nineteen subjects between the ages of 9 and 13 years performed 3 experiments in a controlled laboratory setting: a simple response time test, an avoidance response time test, and a pitching response time test. METHODS: Each subject performed these tests in order. The simple reaction time test tested the subjects' mean simple response time, the avoidance reaction time test tested the subjects' ability to avoid a simulated batted ball as a fielder, and the pitching reaction time test tested the subjects' ability to avoid a simulated batted ball as a pitcher. RESULTS: Reducing the weight of a standard baseball from 142 g to 113 g led to a less than 5% increase in impact probability for nonpitchers. However, the results indicate that the impact probability for pitchers could increase by more than 25%. CONCLUSION: Pitching may greatly increase the amount of time needed to react and defend oneself from a batted ball. CLINICAL RELEVANCE: Impact injuries to youth baseball players may increase if a 113-g ball is used.

Assessing biological maturity: chronological age and the pubertal development scale predict free testosterone in adolescent males.

BACKGROUND: Pubertal development status has implications for development of physical characteristics, performance, and injury risk in school-aged athletes. OBJECTIVE: The objective of this study was to evaluate the ability of non-invasive measures of biological maturity to predict salivary free testosterone. PARTICIPANTS: A total of 61 physically active males (ages 6-16) participated in this study. METHODS: Participants had their anthropometrics measured, completed the Pubertal Development Scale (PDS), and reported their birthdays and the heights of their biological parents. Exact chronological age and percent of predicted height were calculated. Resting salivary samples were collected and assessed for free testosterone levels using enzyme-linked immunosorbent assay procedures. Variables were entered into a stepwise linear regression to predict free testosterone. RESULTS: The regression model was statistically significant (R²=0.716, F2,61=74.2, p<0.005) with chronological age (ß=0.66, t60=7.587, p<0.005) and PDS (ß=0.26, t60=3.02, p=0.004) remaining as significant predictors of free testosterone. CONCLUSIONS: Chronological age and PDS adequately predict salivary free testosterone levels in school-aged males and may be an appropriate tool to evaluate physical maturity in school-aged males quickly, cheaply, and accurately.

Dominant-limb range-of-motion and humeral-retrotorsion adaptation in collegiate baseball and softball position players.

CONTEXT: Biomechanically, the motions used by baseball and softball pitchers differ greatly; however, the throwing motions of position players in both sports are strikingly similar. Although the adaptations to the dominant limb from overhead throwing have been well documented in baseball athletes, these adaptations have not been clearly identified in softball players. This information is important in order to develop and implement injury-prevention programs specific to decreasing the risk of upper extremity injury in softball athletes. OBJECTIVE: To compare range-of-motion and humeral-retrotorsion characteristics of collegiate baseball and softball position players and of baseball and softball players to sex-matched controls. DESIGN: Cross-sectional study. SETTING: Research laboratories and athletic training rooms at the University of North Carolina at Chapel Hill. PATIENTS OR OTHER PARTICIPANTS: Fifty-three collegiate baseball players, 35 collegiate softball players, 25 male controls (nonoverhead athletes), and 19 female controls (nonoverhead athletes). INTERVENTION(S): Range of motion and humeral retrotorsion were measured using a digital inclinometer and diagnostic ultrasound. MAIN OUTCOME MEASURE(S): Glenohumeral internal-rotation deficit, external-rotation gain, total glenohumeral range of motion, and humeral retrotorsion. RESULTS: Baseball players had greater glenohumeral internal-rotation deficit, total-range-of-motion, and humeral-retrotorsion difference than softball players and male controls. There were no differences between glenohumeral internal-rotation deficit, total-range-of-motion, and humeral-retrotorsion difference in softball players and female controls. CONCLUSIONS: Few differences were evident between softball players and female control participants, although range-of-motion and humeral-retrotorsion adaptations were significantly different than baseball players. The throwing motions are similar between softball and baseball, but the athletes adapt to the demands of the sport differently; thus, stretching/strengthening programs designed for baseball may not be the most effective programs for softball athletes.

Improper trunk rotation sequence is associated with increased maximal shoulder external rotation angle and shoulder joint force in high school baseball pitchers.

BACKGROUND: In a properly coordinated throwing motion, peak pelvic rotation velocity is reached before peak upper torso rotation velocity, so that angular momentum can be transferred effectively from the proximal (pelvis) to distal (upper torso) segment. However, the effects of trunk rotation sequence on pitching biomechanics and performance have not been investigated. PURPOSE: The aim of this study was to investigate the effects of trunk rotation sequence on ball speed and on upper extremity biomechanics that are linked to injuries in high school baseball pitchers. The hypothesis was that pitchers with improper trunk rotation sequence would demonstrate lower ball velocity and greater stress to the joint. STUDY DESIGN: Descriptive laboratory study. METHODS: Three-dimensional pitching kinematics data were captured from 72 high school pitchers. Subjects were considered to have proper or improper trunk rotation sequences when the peak pelvic rotation velocity was reached either before or after the peak upper torso rotation velocity beyond the margin of error (±3.7% of the time from stride-foot contact to ball release). Maximal shoulder external rotation angle, elbow extension angle at ball release, peak shoulder proximal force, shoulder internal rotation moment, and elbow varus moment were compared between groups using independent t tests (α < 0.05). RESULTS: Pitchers with improper trunk rotation sequences (n = 33) demonstrated greater maximal shoulder external rotation angle (mean difference, 7.2° ± 2.9°, P = .016) and greater shoulder proximal force (mean difference, 9.2% ± 3.9% body weight, P = .021) compared with those with proper trunk rotation sequences (n = 22). No other variables differed significantly different between groups. CONCLUSION: High school baseball pitchers who demonstrated improper trunk rotation sequences demonstrated greater maximal shoulder external rotation angle and shoulder proximal force compared with pitchers with proper trunk rotation sequences. CLINICAL RELEVANCE: Improper sequencing of the trunk and torso alter upper extremity joint loading in ways that may influence injury risk. As such, exercises that reinforce the use of a proper trunk rotation sequence during the pitching motion may reduce the stress placed on the structures around the shoulder joint and lead to the prevention of injuries.

Prevalence of freestyle biomechanical errors in elite competitive swimmers.

BACKGROUND: Poor freestyle stroke biomechanics is a suggested risk factor for shoulder pain and pathology, but this has not been proven in biomechanical or clinical studies. Furthermore, the prevalence of these theoretical errors has not been identified, which would help coaches, athletic trainers, and researchers determine the most appropriate errors to focus on and develop interventions. HYPOTHESIS: The majority of swimmers will present with at least 1 freestyle stroke error. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 4. METHODS: Stroke biomechanics for 31 swimmers from a collegiate swimming team were captured using underwater/above-water cameras. Each video was evaluated for biomechanical errors: a dropped elbow during the pull-through phase, a dropped elbow during the recovery phase, an eyes-forward head-carrying angle, incorrect hand position during hand entry, incorrect hand entry angle, incorrect pull-through pattern, and inadequate body roll. Error prevalence was calculated, and relationships among the errors were evaluated using chi-square statistics. RESULTS: A dropped elbow during the pull-through phase (61.3%) and a dropped elbow during the recovery phase (53.2%) had the highest prevalence. A dropped elbow during the recovery phase was significantly associated with a thumb-first hand entry angle (P = 0.027) and incorrect hand entry position (P = 0.009). An eyes-forward head-carrying angle was associated with an incorrect pull-through pattern (P = 0.047). CONCLUSION: Biomechanical errors potentially detrimental to the shoulder are prevalent among swimmers. Many of the errors were interrelated, suggesting that one error may lead to other errors. CLINICAL RELEVANCE: These errors highlight the need for proper stroke instruction and evaluation to decrease the risk of shoulder injury in competitive swimmers.

Increase in humeral retrotorsion accounts for age-related increase in glenohumeral internal rotation deficit in youth and adolescent baseball players.

BACKGROUND: Glenohumeral internal rotation deficit (GIRD) is the difference in internal rotation range of motion (IRROM) between the dominant and nondominant limbs. Pathological GIRD of greater than 15° to 25° has previously been linked to shoulder and elbow injuries in baseball players. Because of its relationship to shoulder and elbow disorders, research has focused on understanding the underlying factors that contribute to changes in IRROM and ultimately GIRD. The rotation deficit reportedly increases during adolescence, but it remains unclear whether this change is caused by changes in osseous properties or soft tissue tightness. PURPOSE: To evaluate the influence of age group on GIRD, humeral retrotorsion, retrotorsion-adjusted GIRD, and total range of motion (TROM) in healthy baseball players. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Four groups of healthy baseball players participated in the study: 52 youth (aged 6-10 years), 52 junior high school (JH) (aged 11-13 years), 70 junior varsity (JV) (aged 14-15 years), and 113 varsity (aged 16-18 years) players. Internal rotation range of motion, external rotation range of motion (ERROM), and humeral retrotorsion were measured bilaterally using a digital inclinometer and diagnostic ultrasound. Retrotorsion-adjusted IRROM was calculated as the available IRROM from the humeral retrotorsion position; TROM was calculated as the sum of IRROM and ERROM; and GIRD, the difference in humeral retrotorsion between limbs, adjusted GIRD, and the difference in TROM between limbs were calculated as the difference between the dominant and nondominant sides. Four separate analyses of variance were used to compare these variables between age groups. RESULTS: There was a significant group difference in GIRD (F3,284 = 8.957; P < .001) and a difference in humeral retrotorsion between limbs (F3,284 = 9.688; P < .001). Also, GIRD was greater in varsity participants compared with youth (mean difference [MD], 5.05°) and JH (MD, 4.95°) participants and in JV participants compared with JH (MD, 5.36°) and youth (MD, 5.47°) participants. The difference in humeral retrotorsion between limbs was greater in varsity participants compared with youth (MD, 8.79°) and JH (MD, 5.52°) participants and in JV participants compared with youth participants (MD, 7.88°). There were no significant differences in adjusted GIRD (F3,284 = 1.136; P = .335) or TROM (F3,284 = 1.214; P = .305). CONCLUSION: Glenohumeral internal rotation deficit and humeral retrotorsion increased with age in youth/adolescent baseball players, while retrotorsion-adjusted GIRD and TROM remained unchanged. An age-related increase in GIRD is primarily attributed to humeral retrotorsion rather than soft tissue tightness. CLINICAL RELEVANCE: While there was an increase in GIRD from youth league to high school participants, TROM and retrotorsion-adjusted GIRD remained constant across the age groups, indicating that this increase between the age groups is not pathological GIRD and may not contribute to an increased injury risk.

Practice habits and attitudes and behaviors concerning shoulder pain in high school competitive club swimmers.

OBJECTIVE: The objective of this study is to describe the practice habits, injury frequency, and attitudes and behaviors concerning shoulder pain in high school-aged competitive swimmers and describe the relationship between attitudes and behaviors. DESIGN: Cross-sectional research design. SETTING: Local swimming clubs. PARTICIPANTS: One hundred two swimmers, aged 13-18 years, at the top training level of their club team were included in the study. ASSESSMENT OF RISK FACTORS: Participants were given a survey with questions regarding swimming practice and attitudes and behaviors concerning shoulder pain. MAIN OUTCOME MEASURES: Practice habits (yards/week, practice/week, dry-land and weight/week, and months swimming/year) and attitudes and behaviors concerning shoulder pain. RESULTS: Subjects completed an average of 6.89 ± 1.41 swimming practices/wk of 6000 to 7000 yd/practice. The majority of swimmers believe that mild and moderate shoulder pain is normal in swimming and should be tolerated to complete practice, while a majority responded that they swim with shoulder pain. Seventy-three percent of swimmers reported using pain medication to manage their shoulder pain. There was a significant correlation between attitude and behaviors of moderate and severe shoulder pain. CONCLUSIONS: Club swimmers have a high frequency of practices, comparable to collegiate and professional swimmers. They believe that shoulder pain is normal and should be tolerated to complete practice. The association between the swimmers' attitudes and behaviors indicates that the interventions that educate the swimmers, coaches, and parents may be effective in changing their attitudes and ultimately their behaviors, decreasing the number of athletes who train with shoulder pain.