Effect of Body Type on Respiratory Kinematics in Female Classical Singers.

Breathing for singing is a highly contested issue in singing pedagogy with a wide variety of strategies recommended by teachers and the tendency for individuals to find more success with some strategies than others. The concept of body type as a determining factor has been suggested and supported by Hixon and Hoit, but little research has been conducted on this topic since and especially little research has been conducted using biologically female subjects. The investigators recruited eight female, classically trained singers and evaluated their body composition based on several anthropometric measurements (height, body mass, body fat percentage, and ectomorphy as determined by the Heath-Carter Somatotype system). Subjects were recruited from the greater San Antonio, Texas area and research was recorded on the campus of the University of Texas at San Antonio. The subjects were then fitted with reflective markers around the abdomen and thorax and stood on a platform with an eight-camera motion capture system recording their chest wall and abdominal movements while they performed a series of singing tasks. These singing tasks include a messa di voce, staccato arpeggio, and the first verse of "My Country 'Tis of Thee" in a variety of pitch ranges. Data on abdominal and thoracic movements was collected and compared according to body type to test the correlation between somatotype and breathing tendencies.

Marker-Based Versus IMU-Based Kinematics for Estimates of Lumbar Spine Loads Using a Full-Body Musculoskeletal Model.

Musculoskeletal modeling, typically implemented using marker-based systems in laboratory environments, is commonly used for noninvasive estimations of loads. Inertial measurement units (IMUs) have become an alternative for the evaluation of kinematics. However, estimates of spine joint contact forces using IMUs have yet to be thoroughly evaluated. Dynamics tasks and static postures from activities of daily living were captured on 11 healthy subjects using both systems simultaneously. Spine kinematics obtained from IMU- and marker-based systems and L4-L5 joint contact forces were compared. Lateral bending resulted in a weak agreement with significant differences between the 2 systems (P = .02, average root mean-squared error = 4.81), whereas flexion-extension and axial rotation exhibited the highest agreement with no significant differences (P < .05, average root mean-squared error = 5.51 and P < .31, average root mean-squared error = 5.08, respectively). All tasks showed excellent correlations (R2 = .76-.99) in estimated loads between systems. Differences in predicted loads at the L4-L5 were only observed during flexion-extension (1041 N vs 947 N, P = .0004) and walking with weights (814 N vs 727 N, P = .004). Different joint reaction force outcomes were obtained in 2 of the 8 tasks between systems, suggesting that IMUs can be robust tools allowing for convenient and less expensive evaluations and for longitudinal assessments inside and outside the laboratory setting.

Tutorial: Lessons Learned for Behavior Analysts from Data Scientists.

Big data is a computing term used to refer to large and complex data sets, typically consisting of terabytes or more of diverse data that is produced rapidly. The analysis of such complex data sets requires advanced analysis techniques with the capacity to identify patterns and abstract meanings from the vast data. The field of data science combines computer science with mathematics/statistics and leverages artificial intelligence, in particular machine learning, to analyze big data. This field holds great promise for behavior analysis, where both clinical and research studies produce large volumes of diverse data at a rapid pace (i.e., big data). This article presents basic lessons for the behavior analytic researchers and clinicians regarding integration of data science into the field of behavior analysis. We provide guidance on how to collect, protect, and process the data, while highlighting the importance of collaborating with data scientists to select a proper machine learning model that aligns with the project goals and develop models with input from human experts. We hope this serves as a guide to support the behavior analysts interested in the field of data science to advance their practice or research, and helps them avoid some common pitfalls.

Intracompartmental pressure in lower leg muscles and tibial nerve in healthy volunteers correlate to the stiffness measured using shear wave elastography.

BACKGROUND: Acute compartment syndrome in the lower leg is a painful condition characterized by an increase in intracompartmental pressure. To prevent misdiagnosis and delay in the recognition of the condition, which can lead to severe complications, continuous monitoring of intracompartmental pressure for at least 24 h. from the onset of initial symptoms has been recommended. The purpose of the current study was to establish shear wave elastography as a potential imaging biomarker for the observed increase in pressure in four compartments of the lower leg. METHODS: Eighteen healthy participants (9 males) without any injury in their leg muscles were recruited for the study after internal review board approval. Subjects were instructed to sit on a table and pressures at 60, 90, and 120 mmHg were applied using a pressure cuff placed above the proximal pole of the patella. Shear wave elastography-measured stiffness outcomes at baseline (0 mmHg) and at each cuff pressure level were obtained from the tibialis anterior, the peroneus longs, gastrocnemius medialis, and tibialis posterior muscles, as well as the tibial nerve. FINDINGS: Spearman's rank correlation coefficient showed strong correlations between shear wave elastography-measured stiffness from all four muscles and cuff pressure levels (r > 0.80, P < 0.05). Stiffness from the tibial nerve was also significantly correlated with cuff pressure levels (r > 0.99, P < 0.05). INTERPRETATION: Shear wave elastography imaging of lower leg muscles and nerve can be useful to non-invasively monitor intracompartmental pressure in patients suspected of acute compartment syndrome.

Reduced Injury Prevalence in Soccer Athletes Following GPS Guided Acclimatization.

GPS technology has been used to retrospectively correlate injury risk to changes in training load, however the use of GPS technology to plan and monitor training load over an acclimatization period to prevent musculoskeletal injury remains unexplored. This article reports the utility of GPS technology to help develop and monitor incremental increases in training load while transitioning from off-season to in season to reduce musculoskeletal injury. A series of daily minimum standards were established based on observed training loads in year 1 to gradually acclimate soccer athletes over a 5-week period prior to competition season in year 2. Daily check-ins with GPS data were used to ensure athletes met the standards to safely reach the expected training load of a competitive season. Following the 5-week GPS guided training program a lower overall prevalence of injury (Year 1: 92.6% (95%CI = 75.7-100) vs. Year 2: 55.2% (95%CI = 35.7-73.6)) (p = .002) and overall injury rate (Year 1: 8.1/1000 exposure hours (95%CI = 5.2-12) vs 4.6/1000 exposure hours (95%CI = 2.7-7.5) in year 2 (p = .08)) was observed. The observed reduction in injury prevalence and incidence demonstrates how GPS data can be used to proactively design and monitor preventative chronic training load acclimatization programs.

Intrasession and Intersession Reliability of Isometric Trunk and Hip Strength Measurements Using the Portable Tension Dynamometer.

CONTEXT: The trunk/pelvis is an important link between the upper- and lower-extremities. Therefore, assessing strength of the trunk and hip muscles that control the segments is clinically meaningful. While an isokinetic dynamometer can be used to measure trunk strength, the equipment is expensive and not portable. OBJECTIVE: To test the reliability of simple trunk and hip strength measures that utilize a bar, straps, and a portable tension dynamometer. DESIGN: Test-retest reliability study. SETTING: Biomechanics research laboratory. Patients (or Other Participants): Twenty college-age individuals (10 males/10 females, age = 20.9 [3.7] y) participated. INTERVENTION(S): The participants attended 2 testing sessions, 1 week apart. The participants' trunk-flexion, rotation, and hip abduction strength were measured at each session. MAIN OUTCOME MEASURES: Peak trunk flexion, rotation, and hip abduction forces were normalized to the participant's body weight (BW). In addition, hip-abduction torque was calculated by multiplying the force times the leg length and normalized to BW. The trial data from both sessions were used to calculate the intrasession reliability, and the averages from the 2 sessions were used to calculate the intersession reliability. Intraclass correlation coefficients, SEM, and minimal detectable change were calculated to evaluate reliability of measures. RESULTS: The intrasession intraclass correlation coefficients (SEM) for trunk flexion, rotation, hip abduction, and hip abduction torque were .837 (5.2% BW), .978 (1.3% BW), .955 (1.0% BW), and .969 (5.8 N·m/BW), respectively. The intersession reliability for trunk flexion, rotation, hip abduction, and hip abduction torque were .871 (4.3% BW), .801 (3.8% BW), .894 (1.5% BW), and .968 (5.9 N·m/BW), respectively. CONCLUSIONS: The measures of trunk and hip abduction strength are highly repeatable within a session. The reliability of the measures between sessions was also good/excellent with relatively small SEM and minimal detectable change. The tests described in this study can be used to assess changes in trunk/hip strength over time.

Clinical medication review type III of polypharmacy reduced unplanned hospitalizations in older adults: A meta-analysis of randomized clinical trials.

AIM: To analyze the impact of clinical medication reviews (CMR) on reducing unplanned hospitalizations owing to polypharmacy among older adults using an intervention. METHODS: Our meta-analysis complied with PRISMA guidelines. The literature review comprised a search for articles published between January 1972 and March 2017 on MEDLINE and Google Scholar. We identified randomized controlled trials focusing on CMR that evaluated unplanned hospitalization and re-hospitalization among older adults as a primary outcome. The keywords used were "CMR" or "medication review" in their titles, and the phrases "elderly" or "older adults" or "geriatric" and "polypharmacy." The randomized controlled trials selected were divided according to the three types of CMR to analyze the characteristics of each review. RESULTS: We included nine randomized controlled trials that examined the impact of CMR of polypharmacy in older patients. Five trials corresponded to CMR type I (prescription only review) or II (adherence review), whereas four corresponded to type III (comprehensive clinical evaluation for disease management). Type I/II increased the number of unplanned hospitalizations (RR 1.22, 95% CI 1.07-1.38, P = 0.002), whereas type III decreased hospital admissions (RR 0.86, 95% CI 0.79-0.95, P = 0.001). CONCLUSIONS: The present findings show the need for an intervention standardization for CMR, particularly for type III in older adults with polypharmacy, to decrease hospitalizations. Geriatr Gerontol Int 2019; 19: 1275-1281.

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.

Effect of Wheelchair Stroke Pattern on Upper Extremity Muscle Fatigue.

BACKGROUND: Shoulder dysfunction is common in persons with spinal cord injury (SCI) with an incidence of up to 63%. Dysfunction is a result of muscle imbalances, specifically denervated rotator cuff muscles that are repetitively used during manual wheelchair propulsion. OBJECTIVE: To determine which arm stroke technique, pump (P) or semicircular (SC), is most energy efficient for long periods of propulsion. DESIGN: A randomized study with repeated measures observations. SETTING: The study was performed at an institutional gait analysis laboratory. PARTICIPANTS: 18 able-bodied (AB) male participants were studied and randomized into one of 2 conditions, SC or P. METHODS: Shoulder muscle fatigue was measured by changes in Borg CR10 Rate of Perceived Exertion (Borg RPE) and upper extremity strength via a handheld dynamometer. Participants were studied and assigned into one of 2 conditions of wheelchair arm propulsion patterns, SC or P group, and propelled on a wheelchair treadmill for 10 minutes. MAIN OUTCOME MEASURES: The primary outcomes included recordings of Borg RPE scale during continuous wheelchair propulsion and pre- and post-test dynamometer testing means for bilateral elbow and shoulder extension. Analysis of covariance, t-tests, and Kruskal-Wallis tests were used in analyzing data. RESULTS: Although not significant (P = .23), the Borg RPE scores for the SC condition were consistently higher than the scores for the P condition. In addition, the dynamometer pre- and post-test readings demonstrated a larger decrease for the SC condition participants than for the P condition participants, but were not statistically significant. CONCLUSIONS: These data demonstrate that the SC wheelchair propulsion pattern appears to be more fatiguing to shoulder muscles than the P propulsion pattern. However, more data would need to be collected to find a significant difference. LEVEL OF EVIDENCE: II.

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.

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.

Evaluation of upper body kinematics and muscle activity during milking attachment task.

The objective of the study was to evaluate the effects of udder height on upper body kinematics and muscle activity during a simulated attachment task in a parallel parlor set up, and the effects of udder access method (back or side) on the task biomechanics. Twenty males performed the task under conditions that simulated three udder heights and two udder access methods. The muscular load and kinematics during the task confirmed that milking is a physically demanding task. Trunk flexion angle increased with decreasing udder height, and the erector spinae activation was higher when the udder was below shoulder height compared to at or above. Compared to accessing the udder from side of the cow (herringbone parlor style), accessing from behind (Parallel parlor style) was associated with lower trunk flexion, greater shoulder horizontal adduction, lower shoulder elevation, and greater anterior deltoid activation. Milking in herringbone parlor style and with the udder at or above shoulder level may help reduce strain on the trunk/neck.

Reliability and Validity of Quantitative Video Analysis of Baseball Pitching Motion.

Video recordings are used to quantitatively analyze pitchers' techniques. However, reliability and validity of such analysis is unknown. The purpose of the study was to investigate the reliability and validity of joint and segment angles identified during a pitching motion using video analysis. Thirty high school baseball pitchers participated. The pitching motion was captured using 2 high-speed video cameras and a motion capture system. Two raters reviewed the videos to digitize the body segments to calculate 2-dimensional angles. The corresponding 3-dimensional angles were calculated from the motion capture data. Intrarater reliability, interrater reliability, and validity of the 2-dimensional angles were determined. The intrarater and interrater reliability of the 2-dimensional angles were high for most variables. The trunk contralateral flexion at maximum external rotation was the only variable with high validity. Trunk contralateral flexion at ball release, trunk forward flexion at foot contact and ball release, shoulder elevation angle at foot contact, and maximum shoulder external rotation had moderate validity. Two-dimensional angles at the shoulder, elbow, and trunk could be measured with high reliability. However, the angles are not necessarily anatomically correct, and thus use of quantitative video analysis should be limited to angles that can be measured with good validity.

Trunk Muscle Function Deficit in Youth Baseball Pitchers With Excessive Contralateral Trunk Tilt During Pitching.

OBJECTIVE: Pitching technique is one of many factors that affect injury risk. Exhibiting excessive contralateral trunk tilt (CLT) during pitching has been linked to higher ball speed but also to increased joint loading. Deficit in trunk muscle strength has been suggested as an underlying cause of this movement pattern. The purpose of the study was to compare trunk muscle strength between youth baseball pitchers with varying degree of CLT during pitching. DESIGN: Cross-sectional study. SETTING: Baseball practice fields. PARTICIPANTS: Twenty-eight youth baseball pitchers. INDEPENDENT VARIABLES: Pitching technique was captured using a video camera. Based on the 2-dimensional trunk contralateral flexion angle, pitchers were categorized into low (<15 degrees), moderate (15-30 degrees), or high (>30 degrees) CLT groups. MAIN OUTCOME MEASURES: Maximum isometric strength tests for trunk flexion, extension, and bilateral rotation, measured using a dynamometer. RESULTS: The pitchers with high CLT (n = 10) had longer pitching experience (P = 0.014), produced higher ball speed (P = 0.003) compared with the pitchers with moderate (n = 10) and low (n = 8) CLT, but demonstrated greater asymmetry in trunk rotation strength (relative weakness in rotation strength toward dominant side) compared with the pitchers with low CLT (P = 0.015). CONCLUSIONS: Excessive CLT may be a strategy that young pitchers learn to achieve higher ball velocity but also may be associated with imbalance between the oblique muscles on dominant and nondominant side, which may be acquired from repetitive pitching. Strengthening and emphasizing the use of dominant side oblique muscles may keep pitchers from leaning excessively during pitching and thus decrease joint loading.

Accuracy and repeatability of an inertial measurement unit system for field-based occupational studies.

The accuracy and repeatability of an inertial measurement unit (IMU) system for directly measuring trunk angular displacement and upper arm elevation were evaluated over eight hours (i) in comparison to a gold standard, optical motion capture (OMC) system in a laboratory setting, and (ii) during a field-based assessment of dairy parlour work. Sample-to-sample root mean square differences between the IMU and OMC system ranged from 4.1° to 6.6° for the trunk and 7.2°-12.1° for the upper arm depending on the processing method. Estimates of mean angular displacement and angular displacement variation (difference between the 90th and 10th percentiles of angular displacement) were observed to change <4.5° on average in the laboratory and <1.5° on average in the field per eight hours of data collection. Results suggest the IMU system may serve as an acceptable instrument for directly measuring trunk and upper arm postures in field-based occupational exposure assessment studies with long sampling durations. Practitioner Summary: Few studies have evaluated inertial measurement unit (IMU) systems in the field or over long sampling durations. Results of this study indicate that the IMU system evaluated has reasonably good accuracy and repeatability for use in a field setting over a long sampling duration.

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.