Geoffrey C. Dover

Correlation of Range of Motion and Glenohumeral Translation in Professional Baseball Pitchers

Background Altered mobility patterns in the throwing shoulders of professional baseball pitchers have been reported. Most published reports examining glenohumeral laxity have not used an objective testing device. Objective Quantify and compare glenohumeral translation and rotational range of motion between the throwing and non-throwing shoulders in professional baseball pitchers. Study Design Descriptive laboratory study. Methods Force-displacement and range of motion measures were performed bilaterally on 43 asymptomatic professional baseball pitchers. Ultrasound imaging was used to measure glenohumeral translations under stressed and unstressed conditions. Results No significant difference in translation was found between the throwing and nonthrowing shoulders. For both shoulders, posterior translation (5.38 ± 2.7 mm) was significantly greater (P < .001) than was anterior translation (2.81 ± 1.6 mm). External rotation in the throwing shoulder was significantly greater than that in the nonthrowing shoulder (P < .001), whereas internal rotation in the throwing shoulder was significantly less than that in the nonthrowing shoulder (P < .001). The total arc of rotation for the throwing shoulder was not significantly different than that for the nonthrowing shoulder, and correlation coefficients were poor between rotational and translational range of motion in the throwing shoulder, ranging from r = 0.232 to 0.209 between variables. Conclusion No significant difference in glenohumeral translation exists between the throwing and nonthrowing shoulders in asymptomatic professional baseball pitchers, posterior translation is significantly greater than anterior translation in the throwing shoulders of professional baseball pitchers, and glenohumeral translation is not related to rotational range of motion in the throwing shoulders of professional baseball pitchers. Clinical Relevance Altered mobility patterns in asymptomatic professional baseball pitchers may be due to factors other than capsular adaptive changes.

Fear of pain influences outcomes after exercise-induced delayed onset muscle soreness at the shoulder.

ObjectivesThis study investigated whether anxiety, fear of pain, or pain catastrophizing were predictive of pain-related outcomes after induced delayed onset muscle soreness (DOMS) at the shoulder. MethodsHealthy participants (19 males and 23 females) were eligible for participation if they had (a) no history of neck or shoulder pain, (b) no sensory or motor impairments of the upper-extremity, (c) not regularly participating in upper-extremity weight training, (d) not currently or regularly taking pain medication, and (e) no history of upper-extremity surgery. Participants completed self-report measures for fear of pain, pain catastrophizing, and anxiety. Then, participants underwent a standard fatigue protocol to induce DOMS in the shoulder external rotator muscles. Participants were reassessed 24 hours after DOMS induction on clinical and evoked pressure pain reports, muscle force production, self-report of upper-extremity disability, and kinesiophobia. Stepwise regression models considered sex, anxiety, pain intensity, fear of pain, and pain catastrophizing as outcome predictors. ResultsFear of pain alone explained 16% (P=0.008) of the variance in clinical pain and 10% (P=0.047) evoked pressure pain intensity. Clinical pain intensity alone explained 11% (P<0.031) of the variance in muscle force production. Clinical pain intensity and fear of pain explained 50% (P<0.001) of the variance in upper-extremity disability, whereas fear of pain and sex accounted for 26% (P=0.005) of the variance in kinesiophobia. ConclusionsWith the exception of muscle force production, fear of pain had a consistent influence on shoulder DOMS outcomes, even after controlling for pain intensity. This study suggests fear of pain may be a relevant psychologic factor to consider in clinical studies investigating the development and treatment of chronic shoulder pain.

Assessment of Shoulder Proprioception in the Female Softball Athlete

Background There have been reports of overhand throwing athletes having decreased joint position sense in their dominant shoulder as compared with the nondominant shoulder. Very little research, however, exists concerning joint position sense in the female athlete. Hypothesis Female softball athletes have decreased joint position sense in their dominant shoulder as compared with their nondominant shoulder. Study Design Factorial design with investigation of multiple independent variables. Methods Joint position sense was assessed in 50 female softball players and 50 nonthrowing female athletes by using an inclinometer during four glenohumeral joint motions. Both the dominant and nondominant shoulders were assessed and error scores were calculated to describe joint position sense. Data were collected during the course of a fall semester and analyzed by using a mixed model analysis of variance with repeated measures on the dependent variable (error scores). Results A significant group by movement interaction was observed, with the softball athletes demonstrating significantly greater external rotation error scores than the nonthrowing athletes. Conclusion We failed to reject the null hypothesis. Increased error scores (less joint position sense) were observed in both arms of subjects in the softball group. Clinical Relevance This study suggests that there is decreased shoulder proprioception in asymptomatic female athletes involved in overyhand throwing sports, which may predispose them to injury.

Biopsychosocial Influence on Exercise-induced Delayed Onset Muscle Soreness at the Shoulder: Pain Catastrophizing and Catechol-o-methyltransferase ( comt ) Diplotype Predict Pain Ratings

ObjectiveThe experience of pain is believed to be influenced by psychologic and genetic factors. A previous study suggested pain catastrophizing and catechol-O-methyltransferase (COMT) genotype influenced clinical pain ratings for patients seeking operative treatment of shoulder pain. This study investigated whether these same psychologic and genetic factors predicted responses to induced shoulder pain. MethodsParticipants (n=63) completed self-report questionnaires and had COMT genotype determined before performing a standardized fatigue protocol to induce delayed onset muscle soreness. Then, shoulder pain ratings, self-report of upper-extremity disability ratings, and muscle torque production were reassessed 24, 48, and 72 hours later. ResultsThis cohort consisted of 35 women and 28 men, with a mean age of 20.9 years (SD=1.7). The frequency of COMT diplotypes was 42 with “high COMT enzyme activity” (low pain sensitivity group) and 21 with “low COMT enzyme activity” (average pain sensitivity/high pain sensitivity group). A hierarchical regression model indicated that an interaction between pain catastrophizing and COMT diplotype was the strongest unique predictor of 72-hour pain ratings. The same interaction was not predictive of self-report of disability or muscle torque production at 72 hours. The pain catastrophizing×COMT diplotype interaction indicated that participants with high pain catastrophizing and low COMT enzyme activity (average pain sensitivity/high pain sensitivity group) were more likely (relative risk=3.5, P=0.025) to have elevated pain intensity ratings (40/100 or higher). DiscussionThese findings from an experimental model converge with those from a surgical cohort and provide additional evidence that the presence of elevated pain catastrophizing and COMT diplotype indicative of low COMT enzyme activity have the potential to increase the risk of developing chronic pain syndromes.

Comparison of Dynamic Sonography to Stress Radiography for Assessing Glenohumeral Laxity in Asymptomatic Shoulders

Background Stress radiography has been the established imaging method for quantifying glenohumeral joint laxity. Dynamic ultrasound is an alternative imaging method that may be used to measure glenohumeral laxity; however, validity and repeatability have not been examined. Objective To determine criterion-related validity and repeatability of a sonographic imaging method for measuring glenohumeral laxity in asymptomatic shoulders. Study Design Controlled laboratory study. Methods In experiment 1, 20 subjects were assessed for glenohumeral laxity using stress radiography and dynamic ultrasound. In the second experiment, 13 subjects were assessed for laxity in 2 separate test sessions using the dynamic ultrasound technique. Results Correlational analysis between the sonographic and radiographic measures revealed an r = 0.79 (r2 = 0.62), indicating excellent criterion-related validity for the sonographic imaging method. Test-retest repeatability was 0.72 and 0.85 for anterior and posterior translation, respectively, and interrater repeatability was 0.96 and 0.99 for anterior and posterior translation, respectively. Conclusions Dynamic ultrasound appears to be a valid and repeatable method for assessing glenohumeral laxity in a clinical setting. Clinical Relevance Based on the results of this study, dynamic ultrasound is a repeatable and valid method for measuring glenohumeral laxity and therefore may be used as a viable replacement for stress radiography during assessments of glenohumeral laxity.

Unilateral eccentric exercise of the knee flexors affects muscle activation during gait

Uni-lateral muscle soreness is common yet the effects on gait or electromyographic (EMG) activity are unknown. The purpose of our study was to induce delayed onset muscle soreness (DOMS) in the knee flexor group and measure the resultant change in EMG activity and knee motion during gait. Nine healthy subjects participated in the study. Measures of function, evoked tenderness of the biceps femoris, as well as knee angle, and EMG activity during gait were assessed prior and 48 h after an eccentric exercise protocol. DOMS was induced unilaterally in the knee flexors using an isokinetic dynamometer and subjects exercised until they could not generate 50% of their maximal voluntary isometric contraction (MVIC). There was a significant decrease in biceps femoris activity after DOMS during the last phase of gait. Moreover, there was a day × phase interaction for gastrocnemius activity with the last two phases displaying an increase in activity. There was no significant change in knee angle during gait. The decrease in biceps femoris activity as well as the increase in gastrocnemius activity could be evidence of a protective mechanism designed to decrease activity of the sore muscle while increasing the activity of a synergistic muscle.

Prolonged Reduction in Shoulder Strength after Transcutaneous Electrical Nerve Stimulation Treatment of Exercise-Induced Acute Muscle Pain

Transcutaneous electrical nerve stimulation (TENS) is commonly used for reducing musculoskeletal pain to improve function. However, peripheral nerve stimulation using TENS can alter muscle motor output. Few studies examine motor outcomes following TENS in a human pain model. Therefore, this study investigated the influence of TENS sensory stimulation primarily on motor output (strength) and secondarily on pain and disability following exercise‐induced delayed‐onset muscle soreness (DOMS).

Expectancy Reduces Symptoms but not Functional Impairment Following Exercise Induced Musculoskeletal Injury

Objectives: To quantify the extent to which the participant-provider interaction influences the response to sham treatment following exercised-induced acute musculoskeletal pain. Materials and Methods: In total, 40 participants between the ages of 18 and 35 volunteered for the study. Participants came to the laboratory for 3 test sessions 48-hour apart (day 1, 3, and 5). During the initial session, baseline measures were assessed and participants underwent a fatigue protocol for the biceps brachii. Participants were then assigned to a positive expectation or a no-expectation condition before receiving a sham laser therapy treatment. The positive expectation group received symptom improvement priming before their sham treatment. Participants allocated to the no-expectation condition received no feedback before the sham treatment. Maximum voluntary isometric contraction; relaxed elbow angle; visual analog scale; and the QuickDash questionnaire were used as outcome measures. Results: The positive expectation group had a significant reduction in perceived pain compared with the no-expectation group at day 3 follow-up, with the mean scores being 34.65 mm (SE=4.44) compared with 49.4 mm (SE=5.79), respectively. There were no between-group differences with respect to maximum voluntary isometric contraction, QuickDash, or relaxed elbow angle outcomes. In addition, there were no significant between-group differences observed with expected pain on follow-up visits, the effect sizes were d=0.26 on day 1 for day 3 and d=0.51 on day for day 5. Discussion: Positive expectations before a sham treatment enhanced reduction in pain intensity but did not improve functional impairments following exercise-induced acute musculoskeletal injury.