Usage and acceptability of data normalization in baseball pitching.

In baseball pitching biomechanics, kinetic values are commonly ratio 'normalised' by dividing by mass or mass*height to allow for comparison between athletes of different sizes. However, creating a normalised ratio variable should meet certain statistical assumptions. Our purpose was to determine if elbow valgus torque predicted by pitching velocity is influenced by normalisation using regression model comparison with and without normalised torque values. Motion capture data for youth to professional pitchers (n = 1988) were retrospectively analysed. Normalisation assumptions were tested by comparing linear regression models to analogous models with an intercept fixed at zero and by examining remaining correlations between the confounding variable and new, normalised variable. Both mass (p < 0.001) and mass*height (p < 0.001) normalisation did not remove their respective relationship with torque. After accounting for mass or mass and height, velocity predicted 10% of variance in elbow valgus torque, whereas velocity predicted 59% of mass normalised torque and 45% of mass*height normalised torque. Ratio normalisation does not fully account for anthropometric variables that differ across pitchers and leads to different conclusions in the magnitude of velocity's predictive effect on elbow valgus torque. Therefore, we recommend using regression model comparison to account for anthropometric variables in baseball pitching kinetic data.

Validation of the Keele STarT MSK Tool for Patients With Musculoskeletal Pain in United States-based Outpatient Physical Therapy Settings.

The STarT MSK tool was developed to enable risk stratification of patients with common musculoskeletal (MSK) pain conditions and help identify individuals who may require more targeted interventions or closer monitoring in primary care settings, however, its validity in U.S.-based outpatient physical therapy settings has not been investigated. The 10-item Keele STarT MSK risk stratification tool was tested for construct (convergent and discriminant) and predictive validity using a multicenter, prospective cohort study design. Participants (n = 141) receiving physical therapy for MSK pain of the back, neck, shoulder, hip, knee, or multisite regions completed intake questionnaires including the Keele STarT MSK tool, Functional Comorbidity Index (FCI), Optimal Screening for Prediction of Referral and Outcome Review-of-Systems and Optimal Screening for Prediction of Referral and Outcome Yellow Flag tools. Pain intensity, pain interference, and health-related quality of life (Medical Outcomes Study 8-item Short-Form Health Survey (SF-8) physical [PCS] and mental [MCS] component summary scores) were measured at 2- and 6-month follow-up. Participants were classified as STarT MSK tool low (44%), medium (39%), and high (17%) risk. Follow-up rates were 70.2% (2 months) and 49.6% (6 months). For convergent validity, fair relationships were observed between the STarT MSK tool and FCI and SF-8 MCS (r = .35-.37) while moderate-to-good relationships (r = .51-.72) were observed for 7 other clinical measures. For discriminant validity, STarT MSK tool risk-dependent relationships were observed for Optimal Screening for Prediction of Referral and Outcome Review-of-Systems, Optimal Screening for Prediction of Referral and Outcome Yellow Flag, pain interference, and SF-8 PCS (low < medium < high; P < .01) and FCI, pain intensity, and SF-8 MCS (low < medium-or-high; P < .01). For predictive validity, intake STarT MSK tool scores explained additional variability in pain intensity (11.2%, 20.0%), pain interference (7.5%, 14.1%), and SF-8 PCS (8.2%, 12.8%) scores at 2 and 6 months, respectively. This study contributes to the existing literature by providing additional evidence of STarT MSK tool cross-sectional construct validity and longitudinal predictive validity. PERSPECTIVE: This study presents STarT MSK risk stratification tool validity findings from a U.S. outpatient physical therapy sample. The STarT MSK tool has the potential to help physical therapists identify individuals presenting with the most common MSK pain conditions who may require more targeted interventions or closer monitoring.

Exercise for rotator cuff tendinopathy: Proposed mechanisms of recovery.

Rotator cuff (RC) tendinopathy is a common recurrent cause of shoulder pain, and resistance exercise is the first-line recommended intervention. Proposed causal mechanisms of resistance exercise for patients with RC tendinopathy consist of four domains: tendon structure, neuromuscular factors, pain and sensorimotor processing, and psychosocial factors. Tendon structure plays a role in RC tendinopathy, with decreased stiffness, increased thickness, and collagen disorganization. Neuromuscular performance deficits of altered kinematics, muscle activation, and force are present in RC tendinopathy, but advanced methods of assessing muscle performance are needed to fully assess these factors. Psychological factors of depression, anxiety, pain catastrophizing, treatment expectations, and self-efficacy are present and predict patient-reported outcomes. Central nervous system dysfunctions also exist, specifically altered pain and sensorimotor processing. Resisted exercise may normalize these factors, but limited evidence exists to explain the relationship of the four proposed domains to trajectory of recovery and defining persistent deficits limiting outcomes. Clinicians and researchers can use this model to understand how exercise mediates change in patient outcomes, develop subgroups to deliver patient-specific approach for treatment and define metrics to track recovery over time. Supporting evidence is limited, indicating the need for future studies characterizing mechanisms of recovery with exercise for RC tendinopathy.

Shoulder Performance Activity Test (SPAT) for People With Shoulder Pain: Feasibility, Reliability, and Validity.

OBJECTIVE: The purpose of this study was to assess feasibility, reliability, and validity of a new performance-based test, the Shoulder Performance Activity Test (SPAT). METHODS: People with shoulder pain (n = 93) and without shoulder pain (n = 43) were included. The SPAT consists of overhead reach, hand behind head, and hand behind back tasks, each performed with 20 repetitions and rated by time, pain, and effort. The SPAT scores were summed for time, pain, and effort, and a total score across the 3 tasks. Feasibility was assessed by the percentage of SPAT task completion, test-retest reliability by intraclass correlation coefficient (ICC), standard error measurement, minimal detectable change, and known-groups construct validity by comparing between groups (shoulder pain and no pain) and between shoulders in those with pain. RESULTS: All participants performed the 3 SPAT tasks. The ICC was 0.74-0.91, and the minimal detectable change was 3.1-4.7 for task scores and 10.0 points for the total score. Individuals with pain presented higher tasks and total scores compared with those without pain. The moderate/severe pain group had higher scores than the low pain and no shoulder pain groups, and the low pain group had higher scores than the no pain group. Scores were higher in the involved shoulder compared with the uninvolved shoulder. CONCLUSION: The SPAT is a feasible and reliable performance-based test for use in patients with shoulder pain and can differentiate between individuals with and without pain, among different levels of pain, and between involved and uninvolved shoulders. IMPACT: The SPAT provides a standardized method for clinicians to assess shoulder functional performance tasks, which can enable a comprehensive assessment of shoulder disability and clinical decision making. The error metrics can be used to determine meaningful changes in performance.

Initial Validation of a Sacroiliac Joint-Specific Disability Questionnaire.

Low back pain is a multidimensional disorder that can originate from a variety of pain generators, including the sacroiliac (SI) joint. Although the Oswestry Disability Index (ODI) is often used in SI joint treatment studies, the effects of the SI joint on functional disability are likely different from those of other low back pain generators. Thus, we developed the Denver SI Joint Questionnaire (DSIJQ) and performed validation testing in patients (n=24) with SI joint-specific pain at baseline, +2 weeks, and +6 months. Psychometric analyses included test-retest reliability, internal consistency, content validity, convergent criterion validity, divergent criterion validity, and responsiveness. The DSIJQ showed good test-retest reliability (intraclass correlation coefficient=0.87), internal consistency (Cronbach's alpha=0.842), content validity (<30% floor/ceiling effects), convergent criterion validity (r=0.89; P<.001), and divergent criterion validity (r=-0.33; P=.12). The DSIJQ was correlated with performance on two physical function tests: Timed Upand-Go (r=0.53; P=.008) and 5 Minute Walk (r=-0.52; P=.009). The DSIJQ showed better responsiveness than the ODI (standardized response mean and effect size, 1.14 and 1.45 for DSIJQ and 0.75 and 0.81 for ODI). Overall, the DSIJQ performed well on all psychometrics. Importantly, we validated the DSIJQ with patients' ability to complete two tests of physical functioning. Moreover, the DSIJQ was more sensitive to changes in SI joint disability than the ODI. These psychometrics suggest the DSIJQ is appropriate for evaluating SI joint disability and detecting changes in disability after targeted SI joint treatment. [Orthopedics. 2023;46(6):345-351.].

Physical Therapist Management of Glenohumeral Joint Osteoarthritis: A Clinical Practice Guideline from the American Physical Therapy Association.

A clinical practice guideline on glenohumeral joint osteoarthritis was developed by an American Physical Therapy Association volunteer guideline development group that consisted of physical therapists, an occupational therapist, and a physician. The guideline was based on systematic reviews of current scientific and clinical information and accepted approaches for physical therapist management of glenohumeral joint osteoarthritis. This clinical practice guideline is available in Spanish; see Supplementary Appendix 8.

Trajectory of patient-rated outcomes and association with patient acceptable symptom state in patients with musculoskeletal shoulder pain.

OBJECTIVE: Characterize trajectory and predictors of patient acceptable symptom state (PASS) defined recovery at 6 months. METHODS: Individuals with musculoskeletal shoulder pain (n = 140) completed patient-reported disability and PASS at baseline, 1 and 6 months. The PASS was categorized into 3 trajectory groups; 1.) Early Recovery (answered yes to PASS at 1 and 6-months), 2.) Delayed Recovery (PASS-yes only at 6-months), and 3.) Unrecovered. Mixed models characterized the trajectory between PASS-groups using SPADI and QDASH disability change scores. Logistic regression identified predictors of Early Recovery versus Delayed+Unrecovered groups. RESULTS: PASS-defined recovery rates by group were Early Recovery (58%), Delayed Recovery (22%), and Unrecovered (20%). A group main effect indicated lower disability over time in the Early Recovery versus Unrecovered (QDASH mean difference = 11(2.4); p = 0.001; SPADI mean difference = 12(3); p < 0.001). The odds of an Early Recovery slightly increased with greater change scores on the SPADI (odds ratio = 1.06, 95%CI:1.02,1.11; p = 0.004) and QDASH (odds ratio = 1.08, 95%CI:1.03,1.13; p = 0.003) over the first month of treatment. CONCLUSION: Recovery trajectories of patients indicate differing responses to treatment despite overall improvements over the first month of treatment. Incorporating both patient-reported disability (SPADI, QDASH) and acceptable satisfaction (PASS) may aid in determining recovery trajectory, but more evidence is needed to be clinically useful.

Sonographic morphological and qualitative deficits in the elbow ulnar collateral ligament and ulnohumeral joint in throwing arms of asymptomatic collegiate baseball pitchers.

OBJECTIVE: The ulnar collateral ligament (UCL) supports the medial elbow against valgus torque and is commonly injured in baseball pitchers. Changes in UCL morphology and pathology occur with long-term pitching, with more severe findings at higher competition levels. We examined the bilateral differences and the relationship between UCL morphology, pathology, and ulnohumeral joint laxity in asymptomatic collegiate pitchers using ultrasound. MATERIALS AND METHODS: Division I college pitchers (n = 41) underwent ultrasound scans of their bilateral medial elbows, both at rest and in a valgus-stressed position. The presence of enthesopathy, calcifications, and degeneration was assessed qualitatively. UCL thickness and ulnohumeral joint gap were measured with online calipers. The bilateral differences were analyzed using paired t-tests and chi-square analysis, and the relationships between thickness, gapping, and degenerative changes were analyzed using regression analyses. RESULTS: The throwing arm demonstrated greater distal UCL thickness (mean difference (MD) = 0.2 mm (95%CI = 0.1-0.3), p < 0.01), resting and stressed gap (MD = 0.3 mm (95%CI = 0.0-0.7), p = 0.04; MD = 0.4 (95%CI = 0.0-0.9), p = 0.02), and greater prevalence of degeneration and enthesopathy (p = 0.03) compared bilaterally. Enthesopathy and calcifications predicted increased distal UCL thickness (p = 0.04; p = 0.02). Degenerative scores predicted increased stressed-resting ulnohumeral joint gap (p < 0.01). CONCLUSION: In the throwing arms of collegiate pitchers, ultrasound demonstrated UCL thickening, enthesopathy/intra-ligamentous calcification, and greater laxity of the ulnohumeral joint relative to the non-throwing arm. Degeneration of the UCL, not thickness, was related to greater elbow joint gapping. This study demonstrates the utility of ultrasound for examining sonographic characteristics of the UCL in a sample of college pitchers.

Incidence of complications associated with cervical spine surgery and post-operative physical therapy and implications for timing of initiation of post-operative physical therapy: a retrospective database study.

PURPOSE: To describe the incidence of complications associated with cervical spine surgery and post-operative physical therapy (PT), and to identify if the timing of initiation of post-operative PT impacts the incidence rates. METHODS: MOrtho PearlDiver database was queried using billing codes to identify patients who had undergone Anterior Cervical Discectomy and Fusion (ACDF), Posterior Cervical Fusion (PCF), or Cervical Foraminotomy and post-operative PT from 2010-2019. For each surgical procedure, patients were divided into three 12-week increments for post-operative PT (starting at post-operative weeks 2, 8, 12) and then matched based upon age, gender, and Charlson Comorbidity Index score. Each group was queried to determine complication rates and chi-square analysis with adjusted odds ratios, 95% confidence intervals, and p-values were used. RESULTS: Following matching, 3,609 patients who underwent cervical spine surgery at one or more levels and had post-operative PT (ACDF:1784, PCF:1593, and cervical foraminotomy:232). The most frequent complications were new onset cervicalgia (2-14 weeks, 8-20 weeks, 12-24 weeks): ACDF (15.0%, 14.0%, 13.0%), PCF (18.8%, 18.0%, 19.9%), cervical foraminotomy (16.8%, 16.4%, 19.4%); revision: ADCF (7.9%, 8.2%, 7.4%), PCF (9.3%, 10.6%, 10.2%), cervical foraminotomy (11.6%, 10.8% and 13.4%); wound infection: ACDF (3.3%, 3.4%, 3.1%), PCF (8.3%, 8.0%,7.7%), cervical foraminotomy (5.2%, 6.5%, < 4.7%). None of the comparisons were statistically significant. CONCLUSION: The most common post-operative complications included new onset cervicalgia, revision and wound infection. Complications rates were not impacted by the timing of initiation of PT whether at 2, 8, or 12 weeks post-operatively.

Hip Abductor Strength Asymmetry: Relationship to Upper Extremity Injury in Professional Baseball Players.

BACKGROUND: Hip strength is an important factor for control of the lumbo-pelvic-hip complex. Deficits in hip strength may affect throwing performance and contribute to upper extremity injuries. HYPOTHESIS: Deficits in hip abduction isometric strength would be greater in those who sustained an upper extremity injury and hip strength would predict injury incidence. STUDY DESIGN: Prospective cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: Minor League baseball players (n = 188, age = 21.5 ± 2.2 years; n = 98 pitchers; n = 90 position players) volunteered. Hip abduction isometric strength was assessed bilaterally with a handheld dynamometer in side-lying position, expressed as torque using leg length (N·m). Hip abduction strength asymmetry was represented by [(trail leg/lead leg) × 100]. Overuse or nontraumatic throwing arm injuries were prospectively tracked. Poisson regression models were used to estimate relative risk ratios associated with hip asymmetry; confounders, including history of prior overuse injury in the past year, were included. RESULTS: Hip abduction asymmetry ranged from 0.05% to 57.5%. During the first 2 months of the season, 18 players (n = 12 pitchers) sustained an upper extremity injury. In pitchers, for every 5% increase in hip abduction asymmetry, there was a 1.24 increased risk of sustaining a shoulder or elbow injury. No relationship between hip abduction strength and injury was observed for position players. CONCLUSION: Hip abduction asymmetry in pitchers was related to subsequent upper extremity injuries. The observed risk ratio indicates that hip abduction asymmetry may contribute a significant but small increased risk of injury. CLINICAL RELEVANCE: Hip abduction muscle deficits may affect pitching mechanics and increase arm stress. Addressing hip asymmetry deficits that exceed 5% may be beneficial in reducing upper extremity injury rates in pitchers.

Functional and morphological changes in shoulder girdle muscles after repeated climbing exercise.

This study aimed to investigate the acute effect of repeated climbing actions on functional and morphological measures of the shoulder girdle. Fifteen male indoor climbers participated in this study. All the climbers declared route level 6a+, as the best climbing grade (French climbing grade scale). Functional (range of motion - ROM and muscle strength), and morphological measurements (muscle/tendon stiffness and thickness) after a repeated climbing exercise protocol were analysed. The ROM and muscle strength showed significant decreases from baseline to Immediate-Post (IA) as well as significant increases from IA to 1 h-Post for all movements (p ≤ .001 for all). Muscle stiffness showed significant increases from baseline to IA after as well as significant decreases from IA to 1 h-Post for all muscles (p ≤ .001 for all). However, the thickness showed significant increases from baseline to IA for supraspinatus tendon and muscle thickness and occupation ratio (p ≤ .001 for all), while a significant decrease was observed in acromiohumeral distance (p ≤ .001). Significant decreases from IA to 1 h-Post were found for muscles/tendons and occupation ratio (p ≤ .001 for all), while a significant increase for AHD (p ≤ .001). Our data demonstrated acute alterations in tendon thickness due to acute signs of implement symptom in climbers.

Stiffness and thickness of the upper trapezius muscle increase after repeated climbing bouts in male climbers.

Background: Indoor climbing involves overloading the shoulder girdle, including the rotator cuff and upper trapezius muscles. This on the field study aimed to investigate the effects of repeated climbing bouts on morphological and mechanical measures of the upper trapezius muscle. Materials and Methods: Fifteen experienced male climbers participated in the study. Rate of perceived exertion (RPE), blood lactate concentration ([La-]b), and stiffness and thickness over four points of the upper trapezius were assessed before and after a repeated climbing exercise. The procedure for the climbing exercise consisted of five climbs for a total time of 5-minutes per climb, followed by a 5-minute rest. Results: The analysis showed an increase from baseline to after the 3rd climb (p ≤ 0.01) for RPE and after the 5th climb for [La-]b (p ≤ 0.001). Muscle stiffness and thickness increased at all points (1-2-3-4) after the 5th climb (p ≤ 0.01). We found spatial heterogeneity in muscle stiffness and thickness; muscle stiffness was the highest at Point 4 (p ≤ 0.01), while muscle thickness reached the highest values at points 1-2 (both p ≤ 0.01). Moreover, the analysis between the dominant and non-dominant shoulder showed greater stiffness after the 1st climb at Point 1 (p = 0.004) and after the 5th climb at Point 4 (p ≤ 0.001). Conclusions: For muscle thickness, the analysis showed significant changes in time and location between the dominant and the non-dominant shoulder. Bilateral increases in upper trapezius muscle stiffness and thickness, with simultaneous increases in RPE and blood lactate in response to consecutive climbs eliciting fatigue.

Beginning With the End in Mind: Implementing Backward Design to Improve Sports Injury Rehabilitation Practices.

SYNOPSIS: Current injury-specific return-to-performance rehabilitation programs are not comprehensive, lack intensity, and need better tailoring to the demands of sport. The vast number of rehabilitation and return to sport protocols also reflects a lack of consensus about what the best program looks like, which hinders beginning practitioners from implementing best practices across the spectrum of injuries and sports. Backward design, which has underpinnings in educational research, can facilitate implementation by encouraging practitioners to begin with the end in mind before logically and intentionally working backwards to design transferable and context-specific rehabilitation plans that improve sports injury rehabilitation practices. We discuss and illustrate using case examples how clinicians can apply backward design in best practice sports injury rehabilitation. J Orthop Sports Phys Ther 2022;52(12):770-776. Epub: 7 October 2022. doi:10.2519/jospt.2022.11440.

International physical therapists consensus on clinical descriptors for diagnosing rotator cuff related shoulder pain: A Delphi study.

BACKGROUND: There is a lack of standardized criteria for diagnosing rotator cuff related shoulder pain (RCRSP). OBJECTIVE: To identify the most relevant clinical descriptors for diagnosing RCRSP. METHODS: A Delphi study was conducted through use of an international physical therapists expert panel. A 3-round Delphi survey involving an international panel of physical therapists experts with extensive clinical, teaching, and research experience was conducted. A search query was performed in Web of Science, along with a manual search, to find the experts. The first round was composed of items obtained from a previous pilot Delphi study along with new items proposed by the experts. Participants were asked to rate items across six clinical domains using a five-point Likert scale. An Aiken's Validity Index ≥ 0.7 was considered indicative of group consensus. RESULTS: Fifteen experts participated in the Delphi survey. After the three rounds, consensus was reached on 18 clinical descriptors: 10 items were included in the "subjective examination" domain, 1 item was included in the "patient-reported outcome measures" domain, 3 items in the "diagnostic examination" domain, 2 items in the "physical examination" domain", and 2 items in the "functional tests" domain. No items reached consensus within the "special tests" domain. The reproduction of symptoms in relation to the application of load, the performance of overhead activities, and the need of active and resisted movement assessment were some of the results with greatest consensus. CONCLUSION: In this Delphi study, a total of 18 clinical descriptors across six clinical domains were agreed upon for diagnosing RCRSP.

Shoulder Kinesio Taping Does Not Change Biomechanical Deficits Associated With Scapular Dyskinesis.

Observable scapular dyskinesis is associated with biomechanical deficits. Preventative interventions aimed at correcting these deficits may aid in preventing the development and resolution of shoulder pain. Our purpose was to investigate the effects of kinesio taping (KT) on common biomechanical deficits associated with scapular dyskinesis and shoulder pain. Participants (n = 51) with observable scapular dyskinesis, and without shoulder pain were randomized to KT, KT-placebo, or a no-treatment control group. Measurements taken before, immediately after taping, and 3 days later included pectoralis minor muscle length, lower trapezius muscle strength, scapular upward rotation angle at 0° to 120° in scapular plane humeral elevation and acromiohumeral distance. There were no changes in scapular upward rotation, lower trapezius strength, and acromiohumeral distance immediately after taping or 3 days later compared to baseline (P > .05). The pectoralis minor increased in length in the KT group on day 3 compared to directly after taping (P = .03), but no difference between groups or interaction between time and group were determined (P > .05). Scapular dyskinesis prevalence did not change over time in any group (P > .05). In people with scapular dyskinesis free from shoulder pain, KT applied to the shoulder cannot be recommended to ameliorate the biomechanical deficits associated with shoulder pain.

Effectiveness of a Shoulder Exercise Program in Division I Collegiate Baseball Players During the Fall Season.

BACKGROUND: Deficits in shoulder range of motion (ROM) and strength are associated with risk of arm injury in baseball players. PURPOSE: The purpose of this study was to assess the effectiveness of a standardized exercise program, during the fall season, on shoulder ROM and rotational strength in collegiate baseball players. STUDY DESIGN: Prospective cohort study. METHODS: Passive shoulder internal rotation (IR), external rotation (ER), and horizontal adduction ROM were measured with an inclinometer. Shoulder IR and ER strength was assessed using a hand-held dynamometer and normalized to body weight. Players performed a program of shoulder stretching and strengthening exercises, three times/week for one month and then one time/week for two months. Paired sample t-tests compared pre-intervention to post-intervention outcome measures. RESULTS: Division I baseball players (n=43; 19.6±1.2years, 185.8±5.5cm, 90.5±7.0kg) volunteered. From pre- to post-intervention, there were increases in horizontal adduction ROM in the throwing (Mean Difference (MD)=6.1°, 95%CI=3.7,8.5; p<0.001) and non-throwing arm (MD=8.0°, 95%CI=5.6,10.3; p<0.001), and a decrease in non-throwing arm ER ROM (MD=2.8°, 95%CI= 0.2,5.5; p=0.039). The ER ROM surplus (throwing - non-throwing) increased (MD=5.6°, 95%CI= 1.1,10.2; p=0.016). Throwing arm (MD=1.3%BW, 95%CI=0.5-2.1, p=0.003) and non-throwing arm (MD=1.2%BW, 95%CI=0.4,2.0; p=0.004) ER strength decreased. A notable, but non-significant increase in IR strength on the throwing arm (MD=1.6%BW, 95%CI=0.1,3.0; p=0.055) and decrease on the non-throwing arm (MD=1.2%BW, 95%CI=0.0,2.4; p=0.055) occurred. Additionally, throwing arm ER:IR strength ratio (MD=0.16, 95%CI=0.08,0.25; p<0.001) also decreased. CONCLUSION: Changes in shoulder horizontal adduction ROM, IR strength and relative ER surplus on the throwing arm were noted at the end of the season. The lack of change in IR and ER ROM and may be related to the lack of deficits at the start of the fall season. LEVEL OF EVIDENCE: 2.

Electromyography activation of shoulder and trunk muscles is greater during closed chain compared to open chain exercises.

BACKGROUND: To compare the activation of shoulder and trunk muscles between six pairs of closed (CC) and open chain (OC) exercises for the upper extremity, matched for performance characteristics. The secondary aims were to compare shoulder and trunk muscle activation and shoulder activation ratios during each pair of CC and OC exercise. METHODS: Twenty-two healthy young adults were recruited. During visit 1, the 5-repetition maximum resistance was established for each CC and OC exercise. During visit 2, electromyography activation from the infraspinatus (INF), deltoid (DEL), serratus anterior (SA), upper, middle and lower trapezius (UT, MT, LT), erector spinae (ES) and external oblique (EO) muscles was collected during 5-repetition max of each exercise. Average activation was calculated during the concentric and eccentric phases of each exercises. Activation ratios (DEL/INF, UT/LT, UT/MT, UT/SA) were also calculated. Linear mixed models compared the activation by muscle collapsed across CC and OC exercises. A paired t-test compared the activation of each muscle and the activation ratios (DEL/INF, UT/LT, UT/MT, UT/SA) between each pair of CC and OC exercises. RESULTS: The INF, LT, ES, and EO had greater activation during both concentric (p = 0.03) and eccentric (p < 0.01) phases of CC versus OC exercises. Activation ratios were lower in CC exercises compared to OC exercises (DEL/INF, 3 pairs; UT/LT, 2 pairs; UT/MT, 1 pair; UT/SA, 3 pairs). CONCLUSION: Upper extremity CC exercises generated greater activation of shoulder and trunk muscles compared to OC exercises. Some of the CC exercises produced lower activation ratios compared to OC exercises.

Development of shoulder pain with job-related repetitive load: mechanisms of tendon pathology and anxiety.

BACKGROUND: The paucity of longitudinal clinical studies limits our understanding of the development of shoulder pain with repetitive shoulder tasks, and its association with underlying mind and body mechanisms. Tendon thickening characterizes painful shoulder supraspinatus tendinopathy, and the perception of pain can be affected by the presence of psychological factors such as anxiety and depression. This study determined the incidence of shoulder pain in novice individuals exposed to repetitive shoulder tasks, and the associated change in outcomes of supraspinatus tendon morphology and measures of anxiety and depression. METHODS: We recruited dental hygiene (DH) students (n = 45, novice and exposed to shoulder repetitive tasks) and occupational therapy (OT) students (n = 52, novice, but not exposed to shoulder repetitive tasks), following them over their first year of training. We measured shoulder pain, supraspinatus morphology via ultrasonography, and psychosocial distress via the Hospital Anxiety and Depression Scale. We compared the incidence of shoulder pain (defined as a change of visual analog scale for pain score greater than the minimal clinically important difference) between DH and OT students using Fisher exact test. We used mixed effects models to longitudinally compare the change in outcomes between 3 groups: DH students who develop and did not develop shoulder pain, and OT students. RESULTS: The incidence of shoulder pain is higher in DH students (relative risk = 4.0, 95% confidence interval [CI] 1.4, 11.4). After 1 year, DH students with pain had the greatest thickening of the supraspinatus (0.7 mm, 95% CI 0.4, 0.9). The change in supraspinatus thickness of DH students with pain was greater than both DH students with no pain (0.4 mm, 95% CI 0.1, 0.8) and OT students (0.9 mm, 95% CI 0.5, 1.2). Anxiety score increased 3.8 points (95% CI 1.6, 5.1) in DH students with pain, and 43% of DH students with pain had abnormal anxiety score at 1 year (relative risk = 2.9, 95% CI 1.0, 8.6). CONCLUSION: Our results provide support for the theoretical model of repetitive load as a mechanism of tendinopathy. The supraspinatus tendon thickens in the presence of repetitive tasks, and it thickens the most in those who develop shoulder pain. Concurrently, anxiety develops with shoulder pain, indicating a potential maladaptive central mechanism that may impact the perception of pain.

Evidence for increased neuromuscular drive following spinal manipulation in individuals with subacromial pain syndrome.

BACKGROUND: Thoracic spinal manipulation can improve pain and function in individuals with shoulder pain; however, the mechanisms underlying these benefits remain unclear. Here, we evaluated the effects of thoracic spinal manipulation on muscle activity, as alteration in muscle activity is a key impairment for those with shoulder pain. We also evaluated the relationship between changes in muscle activity and clinical outcomes, to characterize the meaningful context of a change in neuromuscular drive. METHODS: Participants with shoulder pain related to subacromial pain syndrome (n = 28) received thoracic manipulation of low amplitude high velocity thrusts to the lower, middle and upper thoracic spine. Electromyographic muscle activity (trapezius-upper, middle, lower; serratus anterior; deltoid; infraspinatus) and shoulder pain (11-point scale) was collected pre and post-manipulation during arm elevation, and normalized to a reference contraction. Clinical benefits were assessed using the Pennsylvania Shoulder Score (Penn) at baseline and 2-3 days post-intervention. FINDINGS: A significant increase in muscle activity was observed during arm ascent (p = 0.002). Using backward stepwise regression analysis, a specific increase in the serratus anterior muscle activity during arm elevation explained improved Penn scores following post-manipulation (p < 0.05). INTERPRETATION: Thoracic spinal manipulation immediately increases neuromuscular drive. In addition, increased serratus anterior muscle activity, a key muscle for scapular motion, is associated with short-term improvements in shoulder clinical outcomes.