Central chemosensitivity is augmented during two hours of thermoneutral head out water immersion in healthy men and women

New Findings

• What is the central question of the study?

  Is central chemosensitivity blunted during thermoneutral head out water immersion in healthy humans?

• What is the main finding and its importance?

  Central chemosensitivity is augmented during thermoneutral head out water immersion in healthy men and women. Thus, we suggest that the central chemoreceptors do not contribute CO₂ retention during head out water immersion.

Abstract

Carbon dioxide (CO₂) retention occurs during water immersion. Therefore, we tested the hypothesis that central chemosensitivity to hypercapnia is blunted during two hours of thermoneutral head out water immersion (HOWI) in healthy young adults. Twenty-six participants (age: 22 ± 2 years, BMI: 24 ± 3 kg/m², 14 women) participated in two experimental visits: a HOWI visit (HOWI) and a dry time-control visit (Control). Central chemosensitivity was assessed via a rebreathing test at baseline, 10 minutes, 60 minutes, 90 minutes, 120 minutes, and post HOWI and Control. End tidal CO₂ tension (PETCO₂), minute ventilation, blood pressure, and heart rate were recorded continuously. PETCO₂ increased from baseline throughout HOWI (peak increase at 120 minutes: 2 ± 2 mmHg; p < 0.001) and the change in PETCO₂ was greater throughout HOWI than Control (p < 0.001). The change in minute and alveolar ventilation was not different across time (p ≥ 0.173) or between conditions (p ≥ 0.052). Central chemosensitivity was greater than baseline throughout HOWI (peak increase: 0.74 ± 1.01 L/min/mmHg at 120 minutes; p < 0.001) and the change in central chemosensitivity was greater throughout HOWI than Control (p ≤ 0.006). We also divided the cohort into tertiles based on baseline central chemosensitivity (i.e., Low, Intermediate, and High) and compared Low vs. High during HOWI. Low demonstrated an increase in PETCO₂ starting at 10 minutes (2 ± 3 mmHg; p < 0.001), whereas High didn't exhibit an increase in PETCO₂ until 60 minutes (2 ± 2 mmHg; p = 0.018). These data indicate that CO₂ retention occurs throughout HOWI despite augmented central chemosensitivity and that having a high baseline central chemosensitivity might delay the onset of CO₂ retention.

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Genetic engineering: Expanding the reach of Cas9

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Hormone sensitive lipase preferentially redistributes to perilipin-5 lipid droplets in human skeletal muscle during moderate-intensity exercise

Abstract

Hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) control skeletal muscle lipolysis. ATGL is present on the surface of lipid droplets (LD) containing intramuscular triglyceride (IMTG) in both the basal state and during exercise. HSL translocates to LD in ex vivo electrically stimulated rat skeletal muscle. Perilipin-2 and perilipin-5 associated lipid droplets (PLIN2+ and PLIN5+ LD) are preferentially depleted during exercise in humans indicating these PLINs may control muscle lipolysis. We aimed to test the hypothesis that in human skeletal muscle in vivo HSL (but not ATGL) is redistributed to PLIN2+ and PLIN5+ LD during moderate-intensity exercise. Muscle biopsies from 8 lean trained males (age 21 ± 1 years, BMI 22.6 ± 1.2 kg.m⁻² and V̇o_2peak 48.2 ± 5.0 ml.min⁻¹.kg⁻¹) were obtained before and immediately following 60 min of cycling exercise at ∼59% V̇o_2peak. Cryosections were stained using antibodies targeting ATGL, HSL, PLIN2 and PLIN5. LD were stained using BODIPY 493/503. Images were obtained using confocal immunofluorescence microscopy and object based colocalisation analyses were performed. Following exercise, HSL colocalisation to LD increased (P < 0.05), and was significantly larger to PLIN5+LD (+53%) than to PLIN5-LD (+34%) (P < 0.05), while the increases in HSL colocalisation to PLIN2+LD (+16%) and PLIN2-LD (+28%) were not significantly different. Following exercise the fraction of LD colocalised with ATGL (0.53 ± 0.04) did not significantly change (P < 0.05) and was not affected by PLIN association to the LD. This study presents the first evidence of exercise-induced HSL redistribution to LD in human skeletal muscle and identifies PLIN5 as a facilitator of this mechanism.

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EXTENDing fetal life: postnatal placentae for preterm babies

Abstract

The advances in perinatal medicine over the last 20 years are unprecedented. Babies born at extremes of gestational age and birthweight are now able to benefit from innovation in intensive care and many survive into adulthood.

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Failure to expand the motor unit size to compensate for declining motor unit numbers distinguishes sarcopenic from non-sarcopenic older men

Abstract

Sarcopenia results from the progressive loss of skeletal muscle mass and reduced function in older age. It is likely to be associated with the well-documented reduction of motor unit numbers innervating limb muscles and the increase in size of surviving motor units via reinnervation of denervated fibres. However no evidence currently exists to confirm the extent of motor unit remodelling in sarcopenic individuals. The aim of the present study was to compare motor unit size and number between young (n = 48), non-sarcopenic old (n = 13), pre-sarcopenic (n = 53) and sarcopenic (n = 29) men. Motor unit potentials (MUPs) were isolated from intramuscular and surface electromyographic recordings. The motor unit numbers were reduced in all groups of old compared with young (all P < 0.001). Motor unit potentials were enlarged in non-sarcopenic and pre-sarcopenic men compared with young (P = 0.039 and 0.001 respectively), but not in the VL of sarcopenic old (P = 0.485). The results suggest that extensive motor unit remodelling occurs relatively early during ageing, exceeds the loss of muscle mass and precedes sarcopenia. Reinnervation of denervated muscle fibres likely expands the motor unit size in non-sarcopenic and pre-sarcopenic old, but not in the sarcopenic old. These findings suggest that a failure to expand the motor unit size distinguishes sarcopenic from pre-sarcopenic muscles.

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AMSSM Oral Research Poster Presentations

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MRI Evidence of Neuropathic Changes in Former College Football Players

Objective: To examine effects of participating in collegiate football on neural health several years after retirement. We hypothesized that relative cortical thinning and loss of white matter integrity would be observed in former players. Design: Former NCAA Division I football players were compared with demographically similar track-and-field athletes with regard to cortical thickness and white matter integrity. Setting: Participants participated in MRI scans at the Center for Imaging Research at the University of Cincinnati. Participants: Eleven former football players and 10 demographically similar track-and-field athletes. Main Outcome Measures: Normalized cortical thickness was compared between groups using 2-tailed Student t test. As a secondary analysis, Spearman correlation coefficient was calculated between cortical thickness and number of concussions. Fractional anisotropy for regions-of-interest placed in frontal white matter tracts and internal capsule were compared between groups using 2-tailed Student t test. Results: Football players showed significantly lower cortical thickness within portions of both the frontal and temporal cortex. Affected frontal regions included left frontal pole and right superior frontal gyrus. Affected temporal regions included portions of the superior temporal gyrus, left inferior temporal gyrus, and right middle and superior temporal gyri. Cortical thickness inversely correlated with number of reported concussions over most of these regions. In addition, fractional anisotropy was lower in the right internal capsule of former football players, relative to controls. Conclusions: These findings suggest that at least some consequences of high-level collegiate football play persist even after the cessation of regular head blows. Longer-term studies are warranted to examine potential cognitive and functional implications of sustained cortical atrophy.

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Screening Tool to Determine Risk of Having Muscle Dysmorphia Symptoms in Men Who Engage in Weight Training at a Gym

Objective: Although 2 screening tests exist for having a high risk of muscle dysmorphia (MD) symptoms, they both require a long time to apply. Accordingly, we proposed the construction, validation, and implementation of such a test in a mobile application using easy-to-measure factors associated with MD. Design: Cross-sectional observational study. Setting: Gyms in Alicante (Spain) during 2013 to 2014. Participants: One hundred forty-one men who engaged in weight training. Assessment of Risk Factors: The variables are as follows: age, educational level, income, buys own food, physical activity per week, daily meals, importance of nutrition, special nutrition, guilt about dietary nonadherence, supplements, and body mass index (BMI). A points system was constructed through a binary logistic regression model to predict a high risk of MD symptoms by testing all possible combinations of secondary variables (5035). The system was validated using bootstrapping and implemented in a mobile application. Main Outcome Measures: High risk of having MD symptoms (Muscle Appearance Satisfaction Scale). Results: Of the 141 participants, 45 had a high risk of MD symptoms [31.9%, 95% confidence interval (CI), 24.2%-39.6%]. The logistic regression model combination providing the largest area under the receiver operating characteristic curve (0.76) included the following: age [odds ratio (OR) = 0.90; 95% CI, 0.84-0.97, P = 0.007], guilt about dietary nonadherence (OR = 2.46; 95% CI, 1.06-5.73, P = 0.037), energy supplements (OR = 3.60; 95% CI, 1.54-8.44, P = 0.003), and BMI (OR = 1.33, 95% CI, 1.12-1.57, P

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The Influence of Heavier Football Helmet Faceguards on Head Impact Location and Severity

Objective: To determine whether players with heavier faceguards have increased odds of sustaining top of the head impacts and head impacts of higher severity. Design: Cohort study. Setting: On-field. Participants: Thirty-five division I collegiate football players. Interventions: Faceguard mass was measured. Head impact location and severity (linear acceleration [gravity], rotational acceleration [radian per square second], and Head Impact Technology severity profile [unitless]) were captured for 19 379 total head impacts at practices using the Head Impact Telemetry System. Main Outcome Measures: Players' faceguards were categorized as either heavier (>480 g) or lighter (≤480 g) using a median split. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed for sustaining top of the head impacts between faceguard groups using a random intercepts generalized logit model. We compared head impact severity between groups using random intercepts general linear models (α = 0.05). Player position was included in all models. Results: Overall, the 4 head impact locations were equally distributed across faceguard groups (F(3,26) = 2.16, P = 0.117). Football players with heavier faceguards sustained a higher proportion impacts to the top of the head (24.7% vs 17.5%) and had slightly increased odds of sustaining top (OR, 1.72; 95% CI, 1.01-2.94) head impacts rather than front of the head impacts. Conclusions: Football players wearing heavier faceguards might be slightly more prone to sustaining a higher proportion of top of the head impacts, suggesting that greater faceguard mass may make players more likely to lower their head before collision. Individuals involved with equipment selection should consider the potential influence of faceguard design on head impact biomechanics when recommending the use of a heavier faceguard.

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Consequences of Traumatic Brain Injury in Professional American Football Players: A Systematic Review of the Literature

Objective: The purpose of this study was to systematically review the literature for the consequences Traumatic brain injury (TBI) has on cognitive, psychological, physical, and sports-related functioning in professional American Football players. Data Sources: We performed a systematic search in 2 databases, PubMed and SPORTDiscus, to obtain literature from January 1990 to January 2015. To be eligible for inclusion, a study had to examine the relationship between TBI and the consequences for several aspects of functioning in professional American football players older than 18 years. Methodological quality was assessed using a 5-item checklist which assessed selection bias, information bias, and correct reporting of the population and exposure characteristics. Main Results: The search yielded 21 studies that met our inclusion criteria. An evidence synthesis was performed on the extracted data and resulted in 5 levels of evidence. The evidence synthesis revealed that there is strong evidence that concussions are associated with late-life depression and short-term physical dysfunctions. Evidence for the relationship between concussion and impaired sports-related function, prolonged reaction time, memory impairment, and visual-motor speed was inconclusive. Moderate evidence was found for the association between TBI and mild cognitive impairment (MCI), and limited evidence was found for the association between TBI and executive dysfunction. Conclusions: There is strong evidence that a history of concussion in American football players is associated with depression later in life and short-term physical dysfunctions. Also cognitive dysfunctions such as MCI are seen in older players with a history of TBI. These results provide input for actions to prevent TBI and their consequences in (retired) American football players.

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Collegiate Student Athletes With History of ADHD or Academic Difficulties Are More Likely to Produce an Invalid Protocol on Baseline ImPACT Testing

Objective: Attention deficit hyperactivity disorder (ADHD) and other academically-relevant diagnoses have been suggested as modifiers of neurocognitive testing in sport-related concussion, such as Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT). These preexisting conditions may suppress ImPACT scores to the extent that they are indistinguishable from low scores because of poor effort. The present study hypothesized that student athletes with history of ADHD or academic difficulties produce lower ImPACT composite scores and are more likely to produce invalid protocols than those without such conditions. Design: Cross-sectional study. Setting: Midsized public university. Participants: Nine hundred forty-nine National College Athletic Association athletes (average age = 19.2 years; 6.8% ADHD, 5.6% Academic Difficulties, 2.0% comorbid ADHD/Academic Difficulties). Independent Variables: Three seasons of baseline ImPACT protocols were analyzed. Student athletes were grouped using self-reported histories of ADHD or academic difficulties taken from ImPACT demographic questions. Dependent Variables: ImPACT composite scores and protocol validity. Results: Student athletes in the academic difficulties and comorbid groups performed worse on ImPACT composite scores (Pillai's Trace = 0.05), though this pattern did not emerge for those with ADHD. Student athletes with comorbid history were more likely to produce an invalid baseline (10.5% invalid) (χ2 (2) = 11.08, P = 0.004). Those with ADHD were also more likely to produce an invalid protocol (7.7% invalid, compared with 2.6% in student athletes with no history) (χ2 (2) = 10.70, P = 0.005). Conclusions: These findings suggest that student athletes reporting comorbid histories or histories of academic difficulties alone produce lower ImPACT composite scores, and that those with comorbid histories or histories of ADHD alone produce invalid protocol warnings more frequently than student athletes without such histories. Future studies should further examine invalid score thresholds on the ImPACT, especially in student athletes with conditions that may influence test performance. Clinical Relevance: Student athletes with history of ADHD or academic difficulties may more frequently fall below validity score thresholds, suggesting caution in interpreting test performance.

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BTrackS Balance Test for Concussion Management is Resistant to Practice Effects

Objective: Recent guidelines advocate for ongoing balance testing in the assessment of management of concussion injuries. This study sought to determine whether the Balance Tracking System (BTrackS) provides stable balance results over repeated administration and, thus, is a reliable tool for concussion management. Design: Repeated measures and test–retest reliability. Setting: University Biomechanics Laboratory. Participants: Random sample of 20 healthy young adults. Interventions: Force plate balance testing using BTrackS on days 1, 3, 8, and 15. Main Outcome Measures: Practice-induced changes in the average center of pressure excursion over 4 repeated administrations of the BTrackS Balance Test (BBT). Test–retest reliability of center of pressure excursion from day 1 to day 15. Results: No significant practice-induced balance differences were found across testing days (P > 0.4), and test–retest reliability of the BBT was excellent from day 1 to day 15 (R 0.92). Conclusions: These findings indicate that the BBT does not elicit a practice effect over repeat administrations. BTrackS provides excellent reliability and objectivity, which can increase clinician accuracy when monitoring sport-related concussions.

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Investigation of the Rosenbaum Concussion Knowledge and Attitudes Survey in Collegiate Athletes

Objective: The purpose of this study is to determine whether the Rosenbaum Concussion Knowledge and Attitudes Survey (RoCKAS) is an appropriate outcome measure to assess knowledge and attitudes toward concussion in collegiate student-athletes as determined through validity and reliability testing. Study Design: Convenience study. Setting: The researcher recruited all athletic teams at a Division III National Collegiate Athletic Association institution. Participants: Four hundred thirty-three collegiate student-athletes, 18 years of age or older, from a variety of sports took part in this study. As the validity of RoCKAS has never been established for the target population, this study randomly split respondents into 2 studies. Interventions: Participants in this study completed the RoCKAS during preseason meetings before concussion education. The primary researcher was not present during the completion of the survey to allow participants to answer honestly without concern of coercion. Main Outcome Measures: A paper-based Rosenbaum Concussion Knowledge and Attitudes Survey. Results: The Concussion Knowledge Index (CKI) was distributed in 2 cluster constructs and identified variables of low and high difficulty. Multivariate statistical analysis of the Concussion Attitude Index (CAI) explains 68.79% of the total variance. The Confirmatory Factor Analysis did not confirm the hypothesis that similar constructs can be found between data sets ( JOURNAL/cjspm/04.02/00042752-201803000-00005/math_5MM1/v/2018-03-08T125547Z/r/image-tiff = 207.902; consistent akaike information criterion = 391.550; root mean square error of approximation = 0.125, and goodness of fit index = 0.868). Conclusions: The CKI is a valid and reliable measure in collegiate student-athletes. However, the results of the Confirmatory Factor Analysis indicated a poor model fit and improper correlations between attitude items. Therefore, the CAI may not be a sound outcome measure of collegiate student-athlete's attitudes toward concussions.

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AMSSM Research Podium Presentations

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Genetics Influence Neurocognitive Performance at Baseline but Not Concussion History in Collegiate Student-Athletes

Objective: This study investigates 4 single-nucleotide polymorphisms [Apolipoprotein E (APOE), APOE promoter, catechol-O-methyl transferase (COMT), and dopamine D2 receptor] that have been implicated in concussion susceptibility and/or cognitive ability in collegiate student-athletes. Design: Cross-sectional study. Setting: Neuroscience laboratory at Elon University. Participants: Two hundred fifty division I collegiate student-athletes (66 women, 184 men) from various sports. Intervention: All participants completed Immediate Postconcussion Assessment and Cognitive Testing (ImPACT) testing at baseline concussion testing and had a buccal swab taken for DNA for genotyping. Main Outcome Measures: Self-reported history of concussions and neurocognitive performance were taken from ImPACT. Results: Individuals carrying an ε4 allele in their APOE gene had a significantly slower reaction time (P = 0.001). Individuals homozygous for the Val allele of the COMT gene showed significantly worse impulse control scores (P = 0.014). None of the genotypes were able to predict self-reported concussion history in collegiate student-athletes. Conclusions: These results indicate that certain genotypes may influence performance on cognitive testing at baseline and that the APOE genotypes may not influence concussion susceptibility as suggested by past studies.

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Reliability and Validity of Athletes Disability Index Questionnaire

Objective: The purpose of this study was to evaluate validity and reliability of a new proposed questionnaire for assessment of functional disability in athletes with low back pain (LBP). Design: Validity and reliability study. Setting: Elite athletes participating in different fields of sports. Participants: Participants were 165 male and female athletes (between 12 and 50 years old) with LBP. Interventions: Athlete Disability Index (ADI) Questionnaire which is developed by the authors for assessing LBP-related disability in athletes, Oswestry Disability Index (ODI), and the Roland-Morris Disability Questionnaire (RDQ). Main Outcome Measures: Self-reported responses were collected regarding LBP-related disability through ADI, ODI, and RDQ. Results: The test–retest reliability was strong, and intraclass correlation value ranged between 0.74 and 0.94. The Cronbach alpha coefficient value of 0.91 (P

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No Seasonal Changes in Cognitive Functioning Among High School Football Athletes: Implementation of a Novel Electrophysiological Measure and Standard Clinical Measures

Objective: To evaluate neuroelectric and cognitive function relative to a season of football participation. Cognitive and neuroelectric function declines are hypothesized to be present in football athletes. Design: Observational. Setting: Athletic fields and research laboratory. Patients (or Participants): Seventy-seven high school athletes (15.9 + 0.9 years, 178.6 + 7.2 cm, 74.4 + 14.7 kg, and 0.8 + 0.8 self-reported concussions) participating in football (n = 46) and noncontact sports (n = 31). Interventions (or Assessment of Risk Factors): All athletes completed preseason, midseason, and postseason assessments of cognitive and neuroelectric function, self-reported symptoms, and quality of life. All athletes participated in their respective sports without intervention, while head impact exposure in football athletes was tracked using the Head Impact Telemetry System. Main Outcome Measures: Cognitive performance was based on Cogstate computerized cognitive assessment tool processing speed, attention, learning, working memory speed, and working memory accuracy scores. ElMindA brain network activation amplitude, synchronization, timing and connectivity brain network activation scores demarcated neuroelectric performance. Quality of life was assessed on the Health Behavior Inventory and Satisfaction with Life Scale and symptoms on the SCAT3 inventory. Results: Football and control sport athletes did not show declines in cognitive or neuroelectric function, quality-of-life measures, or symptom reports across a season of sport participation. Conclusions: These findings refute the notion that routine football participation places athletes at risk for acute cognitive declines. The lack of impairment may be associated with no association with head impacts and cognitive function, increased physical activity offsetting any declines, and/or test sensitivity. How these findings are associated with long-term cognitive function is unknown.

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Sensitivity and Specificity of the Modified Balance Error Scoring System in Concussed Collegiate Student Athletes

Objective: To assess the efficacy of the modified Balance Error Scoring System (mBESS) compared with the Balance Error Scoring System (BESS) in an acutely concussed population. Design: Prospective observational study. Setting: University athletic training room. Patients: Thirty-five collegiate student-athletes (18 Female, 18.9 ± 0.8 year old, height: 1.71 ± 0.12 m, weight: 76.3 ± 24.1 kg) with diagnosed concussions and baseline BESS/mBESS tests. Interventions: All participants completed the BESS and mBESS on the day after the concussion (acute) and were retested daily until their BESS score achieved baseline value (recovery). Main Outcome Measures: The number of errors committed during the BESS and mBESS at each time point were recorded. The sensitivity and specificity of the BESS and mBESS compared with the baseline test was calculated for acute and recovery as well as the mBESS compared with the BESS. Results: At acute, the sensitivity of the BESS and mBESS were 60.0% and 71.4%, respectively. Relative to mBESS baseline, 60% of participants were misclassified at either acute or recovery. Conclusions: The mBESS had higher sensitivity at acute and identified lingering deficits at BESS recovery. Use of the mBESS is likely to produce different results than the BESS; however, the clinical implications of this warrant further investigation.

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Vision and Vestibular System Dysfunction Predicts Prolonged Concussion Recovery in Children

Objective: Up to one-third of children with concussion have prolonged symptoms lasting beyond 4 weeks. Vision and vestibular dysfunction is common after concussion. It is unknown whether such dysfunction predicts prolonged recovery. We sought to determine which vision or vestibular problems predict prolonged recovery in children. Design: A retrospective cohort of pediatric patients with concussion. Setting: A subspecialty pediatric concussion program. Patients (or Participants): Four hundred thirty-two patient records were abstracted. Assessment of Risk Factors: Presence of vision or vestibular dysfunction upon presentation to the subspecialty concussion program. Main Outcome Measures: The main outcome of interest was time to clinical recovery, defined by discharge from clinical follow-up, including resolution of acute symptoms, resumption of normal physical and cognitive activity, and normalization of physical examination findings to functional levels. Results: Study subjects were 5 to 18 years (median = 14). A total of 378 of 432 subjects (88%) presented with vision or vestibular problems. A history of motion sickness was associated with vestibular dysfunction. Younger age, public insurance, and presence of headache were associated with later presentation for subspecialty concussion care. Vision and vestibular problems were associated within distinct clusters. Provocable symptoms with vestibulo-ocular reflex (VOR) and smooth pursuits and abnormal balance and accommodative amplitude (AA) predicted prolonged recovery time. Conclusions: Vision and vestibular problems predict prolonged concussion recovery in children. A history of motion sickness may be an important premorbid factor. Public insurance status may represent problems with disparities in access to concussion care. Vision assessments in concussion must include smooth pursuits, saccades, near point of convergence (NPC), and accommodative amplitude (AA). A comprehensive, multidomain assessment is essential to predict prolonged recovery time and enable active intervention with specific school accommodations and targeted rehabilitation.

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Increased Level of Serum Hepcidin in Female Adolescent Athletes

Objective: To determine the serum hepcidin concentration and standard hematological parameters in a group of female adolescent athletes, compared with a group of nonathlete females. Design: A case–control study. Setting: A senior high school for athletes in Gothenburg, Sweden. Participants: All female athletes (70), at the school were offered to take part. Fifty-six athletes accepted. From a random sample of age-matched nonathletes, 71 students were recruited to the control group. Main Outcome Measures: Iron deficiency (ID) was determined by levels of serum iron, total iron-binding capacity, transferrin saturation (TS), and ferritin. Serum hepcidin was determined by a mass spectrometry method. All samples were taken at least 12 hours after training. Results: The main result was the finding of a significantly elevated serum hepcidin level in the athlete group, 4.7 nmol/L compared with 3.3 nmol/L (P

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Effectiveness of a Posterior Shoulder Stretching Program on University-Level Overhead Athletes: Randomized Controlled Trial

Objective: To determine whether a posterior shoulder stretch was effective in increasing internal rotation (IR) and horizontal adduction (HAd) range of motion (ROM) in overhead athletes identified as having reduced mobility. Design: Randomized controlled trial (parallel design). Setting: University-based sports medicine clinic. Participants: Thirty-seven university-level athletes in volleyball, swimming, and tennis, with IR ROM deficits ≥15°, were randomized into intervention or control groups. No subjects withdrew or were lost to follow-up. Intervention: The intervention group performed the "sleeper stretch" daily for 8 weeks, whereas the control group performed usual activities. Main Outcome Measures: Independent t tests determined whether IR and HAd ROM differences between groups were significant at 8 weeks and 2-way repeated-measures analysis of variance tests measured the rate of shoulder ROM change. Subject-reported shoulder pain and function were obtained at each evaluation. Results: Significant differences were found between the intervention and control groups' IR and HAd ROM at 8 weeks (P

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AMSSM Rising With Research Presentations

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Shoulder Dynamic Control Ratio and Rotation Range of Motion in Female Junior Elite Handball Players and Controls

Objective: To compare glenohumeral range of motion and shoulder rotator muscle strength in healthy female junior elite handball players and controls. Design: Cross-sectional case–control study. Setting: Sports medical center. Participants: Forty elite female handball players and 30 controls active in nonoverhead sports participated in this study. Main Outcome Measures: Passive external rotator (ER), internal rotator (IR), and total range of motion (TROM) of the dominant and nondominant arm were examined with a goniometer. An isokinetic dynamometer was used to evaluate concentric and eccentric rotator muscle strength at 60 and 120 degrees/s with dynamic control ratio (DCR = ERecc:IRcon) as the main outcome parameter. Results: Except for the ER range of motion in the nondominant arm, no significant differences were found between groups for IR, ER of the dominant arm, and the TROM. Within the handball group, the side-to-side difference for IR of the dominant arm was −1.4 degrees. The ER and the TROM of the dominant arm were significantly larger, 6.3 and 4.9 degrees, respectively. For both groups, the DCR values were above 1 and no significant differences were found between the dominant and nondominant arm. The DCR values in the handball group were significantly lower than in the control group. Conclusions: Based on the adopted definitions for muscle imbalance, glenohumeral internal range of motion deficit and TROM deficit our elite female handball players seem not at risk for shoulder injuries. Prospective studies are needed to support the belief that a DCR below 1 places the shoulder at risk for injury.

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