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Altered Cervical Spine Position Results in Decreased Eccentric Shoulder Rotation Strength
Abstract
Overhead athletics require strenuous shoulder activity in nonneutral cervical spine positions to eccentrically decelerate the throwing/striking arm following ball release/contact. Therefore, we aimed to compare eccentric shoulder rotation strength through a 90° arc between neutral and rotated positions. 52 participants (19M,34F170±10cm;73±18kg,21.9±2.9years) without shoulder or cervical spine pathology participated. Isokinetic eccentric shoulder rotation strength was measured through a 90° arc with shoulder elevated 90° in frontal plane (frontal plane), and 45° anterior to the frontal plane (scapular plane) in neutral and rotated cervical spine positions. Frontal plane eccentric external rotation strength differed between neutral and contralaterally positions in the first 10° of the motion, near forearm vertical (p=0.029). Cervical spine position was obtained by instructing participants to maximally rotate their respective side. Internal rotation strength differed between neutral and contralaterally rotated positions from 55-60° external rotation (p=0.004). Scapular plane eccentric external rotation differed between cervical positions between 21-67° shoulder external rotation (p<0.001). Scapular plane internal rotation strength differed between cervical positions between 22-60° shoulder external rotation (p<0.001). In populations requiring strenuous use of their shoulders in altered cervical spine positions, sports medicine clinicians should consider including strength testing reflecting the functional positions of their patients during an orthopedic examination.
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When investigating the dynamics of three-dimensional multi-body biomechanical systems it is often difficult to derive spatiotemporally directed predictions regarding experimentally induced effects. A paradigm of ‘non-directed’ hypothesis testing has emerged in the literature as a result. Non-directed analyses typically consist of ad hoc scalar extraction, an approach which substantially simplifies the original, highly multivariate datasets (many time points, many vector components). This paper describes a commensurately multivariate method as an alternative to scalar extraction. The method, called ‘statistical parametric mapping’ (SPM), uses random field theory to objectively identify field regions which co-vary significantly with the experimental design. We compared SPM to scalar extraction by re-analyzing three publicly available datasets: 3D knee kinematics, a ten-muscle force system, and 3D ground reaction forces. Scalar extraction was found to bias the analyses of all three datasets by failing to consider sufficient portions of the dataset, and/or by failing to consider covariance amongst vector components. SPM overcame both problems by conducting hypothesis testing at the (massively multivariate) vector trajectory level, with random field corrections simultaneously accounting for temporal correlation and vector covariance. While SPM has been widely demonstrated to be effective for analyzing 3D scalar fields, the current results are the first to demonstrate its effectiveness for 1D vector field analysis. It was concluded that SPM offers a generalized, statistically comprehensive solution to scalar extraction’s over-simplification of vector trajectories, thereby making it useful for objectively guiding analyses of complex biomechanical systems.
The common approach to the multiplicity problem calls for controlling the familywise error rate (FWER). This approach, though, has faults, and we point out a few. A different approach to problems of multiple significance testing is presented. It calls for controlling the expected proportion of falsely rejected hypotheses – the false discovery rate. This error rate is equivalent to the FWER when all hypotheses are true but is smaller otherwise. Therefore, in problems where the control of the false discovery rate rather than that of the FWER is desired, there is potential for a gain in power. A simple sequential Bonferroni-type procedure is proved to control the false discovery rate for independent test statistics, and a simulation study shows that the gain in power is substantial. The use of the new procedure and the appropriateness of the criterion are illustrated with examples.
Isokinetic assessment of shoulder internal-(IR) and external-rotator (ER) strength is commonly used with many different postures (sitting, standing, or supine) and shoulder positions (frontal or scapular plane with 45° or 90° of abduction).
To conduct a systematic review to determine the influence of position on the intersession reliability of the assessment of IR and ER isokinetic strength, to identify the most reliable position, and to determine which isokinetic variable appears to be most stable in intersession reliability.
A systematic literature search through MEDLINE and Pascal Biomed databases was performed in October 2009. Criteria for inclusion were that studies be written in English or French, describe the isokinetic evaluation methods, and describe statistical analysis.
Sixteen studies meeting the inclusion criteria were included. Variable reliability of ER and IR peak torque (PT) were generally reported for all assessment positions; intraclass correlation coefficients were .44-.98 in the seated position with 45° of shoulder abduction, .09-.77 in the seated position with 90° of shoulder abduction, .86-.99 (coefficient of variation: 7.5-29.8%) in the supine position with 90° of shoulder abduction, .82-.84 in the supine position with 45° of shoulder abduction, and .75-.94 in standing. The ER:IR ratio reliability was low for all positions.
The seated position with 45° of shoulder abduction in the scapular plane seemed the most reliable for IR and ER strength assessment. The standing position or a shoulder posture with 90° of shoulder abduction or in the frontal plane must be used with caution given the low reliability for peak torque. Good reliability of ER and IR PT was generally reported, but ER:IR ratio reliability was low.
A variety of biomechanical data are sampled from smooth n-dimensional spatiotemporal fields. These data are usually analyzed discretely, by extracting summary metrics from particular points or regions in the continuum. It has been shown that, in certain situations, such schemes can compromise the spatiotemporal integrity of the original fields. An alternative methodology called statistical parametric mapping (SPM), designed specifically for continuous field analysis, constructs statistical images that lie in the original, biomechanically meaningful sampling space. The current paper demonstrates how SPM can be used to analyze both experimental and simulated biomechanical field data of arbitrary spatiotemporal dimensionality. Firstly, 0-, 1-, 2-, and 3-dimensional spatiotemporal datasets derived from a pedobarographic experiment were analyzed using a common linear model to emphasize that SPM procedures are (practically) identical irrespective of the data's physical dimensionality. Secondly two probabilistic finite element simulation studies were conducted, examining heel pad stress and femoral strain fields, respectively, to demonstrate how SPM can be used to probe the significance of field-wide simulation results in the presence of uncontrollable or induced modeling uncertainty. Results were biomechanically intuitive and suggest that SPM may be suitable for a wide variety of mechanical field applications. SPM's main theoretical advantage is that it avoids problems associated with a priori assumptions regarding the spatiotemporal foci of field signals. SPM's main practical advantage is that a unified framework, encapsulated by a single linear equation, affords comprehensive statistical analyses of smooth scalar fields in arbitrarily bounded n-dimensional spaces.
Twelve experienced male weight lifters performed a rebound bench press and a purely concentric bench press lift. Data were obtained pertaining to 1) the benefits to concentric motion derived from a prior stretch and 2) the movement frequency adopted during performance of the stretch-shorten cycle (SSC) portion of the rebound bench press lift. The subjects also performed a series of quasi-static muscular actions in a position specific to the bench press movement. A brief perturbation was applied to the bar while these isometric efforts were maintained, and the resulting damped oscillations provided data pertaining to each subject's series elastic component (SEC) stiffness and natural frequency of oscillation. A significant correlation (r = -0.718, P less than 0.01) between maximal SEC stiffness and augmentation to concentric motion derived from prior stretch was observed. Subjects were also observed to perform the SSC portion of the rebound bench press movement to coincide with the natural frequency of oscillation of their SEC. These results are interpreted as demonstrating that the optimal stiffness in a rebound bench press lift was a resonant-compliant SEC.
Functional neuroimaging data embodies a massive multiple testing problem, where 100 000 correlated test statistics must be assessed. The familywise error rate, the chance of any false positives is the standard measure of Type I errors in multiple testing. In this paper we review and evaluate three approaches to thresholding images of test statistics: Bonferroni, random field and the permutation test. Owing to recent developments, improved Bonferroni procedures, such as Hochberg’s methods, are now applicable to dependent data. Continuous random field methods use the smoothness of the image to adapt to the severity of the multiple testing problem. Also, increased computing power has made both permutation and bootstrap methods applicable to functional neuroimaging. We evaluate these approaches on t images using simulations and a collection of real datasets. We find that Bonferroni-related tests offer little improvement over Bonferroni, while the permutation method offers substantial improvement over the random field method for low smoothness and low degrees of freedom. We also show the limitations of trying to find an equivalent number of independent tests for an image of correlated test statistics.
This study compared range of motion (ROM) measurements using a cervical range of motion device (CROM) and an optoelectronic system (OPTOTRAK).
To examine the criterion validity of the CROM for the measurement of cervical ROM on healthy adults.
Whereas measurements of cervical ROM are recognized as part of the assessment of patients with neck pain, few devices are available in clinical settings. Two papers published previously showed excellent criterion validity for measurements of cervical flexion/extension and lateral flexion using the CROM.
Subjects performed neck rotation, flexion/extension, and lateral flexion while sitting on a wooden chair. The ROM values were measured by the CROM as well as the OPTOTRAK.
The cervical rotational ROM values using the CROM demonstrated a good to excellent linear relationship with those using the OPTOTRAK: right rotation, r = 0.89 (95% confidence interval, 0.81-0.94), and left rotation, r = 0.94 (95% confidence interval, 0.90-0.97). Similar results were also obtained for flexion/extension and lateral flexion ROM values.
The CROM showed excellent criterion validity for measurements of cervical rotation. We propose using ROM values measured by the CROM as outcome measures for patients with neck pain.
Giordano, KA, Cassidy, MM, and Oliver, GD. Length-tension differences between concentric and eccentric shoulder rotation strength. J Strength Cond Res XX(X): 000–000, 2023—Eccentric contractions generally produce more force than concentric contractions. However, if length-tension relationships affect both contractions equally remains unknown. Therefore, our purpose was to compare concentric versus eccentric shoulder external and internal rotation strength across a continuous 90° arc. Fifty-two physically active individuals performed isokinetic concentric and eccentric shoulder external rotation and internal rotation through a 90° arc (forearm horizontal to forearm vertical) with the shoulder elevated in both the frontal and scapular planes. Statistical parametric mapping analysis compared concentric and eccentric trials within subjects. Frontal plane eccentric external rotation torque was greater than concentric 30°–90° ( p < 0.01) external rotation, and concentric external rotation torque was greater 5°–15° external rotation ( p = 0.01). Frontal plane, eccentric internal rotation torque was greater than concentric 15°–55° external rotation ( p < 0.01), and concentric torque was greater at forearm horizontal ( p = 0.05) and 70°–90° external rotation ( p < 0.01). Scapular plane eccentric external rotation torque was greater than concentric 30°–90° external rotation ( p < 0.01) and concentric external rotation torque was greater 5°–20° external rotation ( p < 0.01). Scapular plane eccentric internal rotation torque was greater than concentric 15°–60° external rotation ( p < 0.01), and concentric torque was greater at forearm horizontal ( p = 0.05) and 78°–90° external rotation ( p = 0.02). Coaches, clinicians, and researchers should interpret data from studies reporting isokinetic data with the understanding that isokinetic peak strength values are not comparing the same muscle length and are not an appropriate measure for all muscle lengths. Furthermore, shoulder stability is affected through decreased eccentric force production at end ranges of shoulder rotation.
Background:
Strength testing of shoulder rotation is commonly used in clinical examinations of the shoulder. People prone to shoulder injury, such as overhead athletes and manual trade workers, place their shoulders under tremendous amounts of stress when the cervical spine is in nonneutral positions. If these nonneutral cervical spine positions result in decreased shoulder strength, it may help explain the etiology of the high prevalence of shoulder injuries in these populations. Given standard clinical strength assessments are performed with a neutral cervical spine, an investigation into the effects of cervical spine rotation is warranted.
Questions/purposes:
We sought to compare isokinetic shoulder rotation strength while in a neutral position with rotated cervical spine positions, specifically (1) with the cervical spine rotated contralaterally with the shoulder elevated in the frontal plane and (2) with the cervical spine rotated ipsilaterally and the shoulder elevated in the scapular plane.
Methods:
A convenience sample of 52 individuals (height 170 ± 10 cm; weight 73 ± 18 kg, age 21 ± 2 years; 18 males, 34 females), without shoulder or cervical spine pathology participated in this study. Participants were screened for eligibility via questionnaire. Concentric shoulder internal and external rotation torque was measured through a 90° arc on an isokinetic dynamometer with the shoulder elevated 90° in the frontal plane, and again 45° anterior to the frontal plane (scapular plane). Two repetitions were performed in a single testing session with the participant's cervical spine in neutral in both planes, maximally rotated contralaterally in the frontal plane, and maximally rotated ipsilaterally with the shoulder in the scapular plane; the second repetition was used for analysis. The testing order was randomized. Data were imported into a platform for statistical parametric mapping analysis (a technique that allows data from the entire arc of motion to be compared with data from another arc to identify differences in the wave form) to compare strength between positions throughout 90° arc of motion.
Results:
Rotating the cervical spine contralaterally with the shoulder in the frontal plane resulted in a decrease in external (2.24 Nm or 12% average difference; p < 0.001) and internal (2.22 Nm or a 6% average difference; p = 0.02) rotation strength with the forearm within 15° and 20° of the vertical position. Rotating the cervical spine ipsilaterally with the shoulder in the scapular plane resulted in a decrease in external rotation strength (1.27 Nm or a 6% average difference; p < 0.001) throughout nearly all the motion, with peaks approximately 20° and 60° from the horizontal position, and internal rotation strength (1.78 Nm or 5% average difference; p < 0.001) the last 60° towards the horizontal position.
Conclusion:
Patient populations who require strenuous use of their shoulders in altered cervical spine positions may be at increased risk for injury from decreased shoulder rotator strength.
Clinical relevance:
Clinicians should assess shoulder strength in the position the patient requires to use their shoulder because cervical spine position may cause weakness that would be missed in standard testing positions.
The common approach to the multiplicity problem calls for controlling the familywise error rate (FWER). This approach, though, has faults, and we point out a few. A different approach to problems of multiple significance testing is presented. It calls for controlling the expected proportion of falsely rejected hypotheses — the false discovery rate. This error rate is equivalent to the FWER when all hypotheses are true but is smaller otherwise. Therefore, in problems where the control of the false discovery rate rather than that of the FWER is desired, there is potential for a gain in power. A simple sequential Bonferronitype procedure is proved to control the false discovery rate for independent test statistics, and a simulation study shows that the gain in power is substantial. The use of the new procedure and the appropriateness of the criterion are illustrated with examples.
Background:
This study evaluated the clinical outcome of arthroscopic treatment for anterior shoulder dislocation in elite and professional baseball players.
Methods:
This study included 51 baseball players who underwent arthroscopic Bankart repair between 2008 and 2015. The follow-up duration was set at 24 months or longer, based on clinic visit or telephone survey. After surgery, players who played in 1 or more official games were considered to have returned to play (RTP), and those who participated in more than 10 official games were considered to have solidly returned to play (sRTP). The RTP and sRTP rates were analyzed by player position (pitcher, catcher, and in-fielder), and the period of RTP after surgery (rehabilitation period) was investigated.
Results:
Of 51 baseball players (mean age, 20.9 years), 14 were pitchers, 6 were catchers, and 31 were in-fielders. Pitchers showed 64% RTP and 57% sRTP, catchers, 83% RTP and 83% sRTP, and in-fielders, 90% RTP and 90% sRTP. The overall RTP and sRTP rates were 82% and 80%, respectively. The average RTP period after surgery (rehabilitation period) was 8.4 months, with 9.6, 9.1, and 7.4 months for pitchers, catchers, and in-fielders, respectively.
Conclusions:
The RTP after arthroscopic Bankart repair shows favorable results, with the nonthrowing shoulder and in-field position yielding the best results. Players undergoing arthroscopic Bankart repair and the surgeon should be aware of the possible outcomes based on the throwing/nonthrowing arm and various positions.
Shoulders of elite field hockey players are loaded continuously during play. However, shoulder girdle muscle performance in this population has never been examined yet. This study aimed to compare isokinetic shoulder girdle performance in elite male field hockey players to matched controls, with respect to strength, endurance and muscle balance. The complete male national field hockey team of Belgium (n = 25) was included and matched to a gender- and age-matched control group of healthy participants (n = 25). A Biodex system-4 dynamometer was used to measure glenohumeral and scapular muscle strength at 2 velocities in a concentric/concentric mode. With the main outcome measures being isokinetic strength values, peak force (protraction-retraction), peak torque (rotations), fatigue index and agonist/antagonist ratio’s. Measurement results showed that elite male field hockey players were stronger than their matched controls, for both the rotational and the protraction-retraction movement. Concerning rotational strength, symmetrical findings were established, contrary to scapular strength, where side differences were noted. At low velocity, retraction peak force was higher on the dominant side. Protraction peak force was higher on the non-dominant side when measured at high velocity. In conclusion, elite field hockey players have a symmetrical rotational strength profile, in contrast to their scapular strength profile.
Objective
To measure sports injuries prevalence, types and mechanisms, considering grappling and impact modalities.
Equipment and methods
An observational, descriptive epidemiology study was conducted involving 125 recreational practitioners. Subjects were inquired regarding the type of martial arts and combat sports (MACS), age, practice time and weekly training volume.
Results
From all, 53.6% athletes suffered injury in the last 12 months. The most common were tendon injuries (39%) and sprains (39%), followed by dislocation/subluxation (23%). In grappling MACS, as Judo, joints injuries were the most frequent, especially the knees and shoulders. For striking modalities, such as Karate, muscle injuries were more frequent and the most common sites were feet and toes, followed by hands and fingers. The lower limbs were the most affected site (χ² = 67.8, P < 0.001). A higher prevalence of injury was found in combat simulations (43%) than in technical training (26%) and competition (10%).
Conclusion
There was a high percentage of injury in lower limbs for both modality groups, and the higher frequency of injuries in the upper limbs were the shoulders, hands and fingers, while for lower limbs were the feet and toes, ankles and knees. Injury occurred mainly during technical training and, in most cases, without protective equipment.
Context
Throwing injuries.
Objective
To study the effects of posterior capsule tightness on humeral head position in late cocking simulation.
Design
Eight fresh frozen shoulders were placed in position of “late cocking,” 90 degrees abduction, and 10 degrees adduction and maximal external rotation. 3D measurements of humeral head relationship to the glenoid were taken with an infrared motion sensor, both before and after suture plication of the posterior capsule. Plications of 20% posterior/inferior capsule and 20% entire posterior capsule were performed, followed by plications of 40% of the posterior/inferior capsule and 40% entire posterior capsule.
Setting
Cadaver Lab.
Intervention
Posterior capsular placation.
Main Outcome Measures
Humeral head position.
Results
40%, but not 20%, posterior/inferior and posterior plications demonstrated a trend to increased posterior-superior humeral head translation relative to controls.
Conclusion
Surgically created posterior capsular tightness of the glenohumeral joint demonstrated a nonsignificant trend to increased posterior/superior humeral head translation in the late cocking position of throwing.
The Second Edition of Kinesiology: The Mechanics and Pathomechanics of Human Movement relates the most current understanding of anatomy and mechanics with clinical practice concerns. Featuring seven chapters devoted to biomechanics, straightforward writing, and over 900 beautiful illustrations, the text provides detailed coverage of the structure, function and kinesiology of each body region. Readers will gain an in-depth understanding of the relationship between the quality of movement and overall human health. © 2009, 2004 Lippincott Williams & Wilkins, a Wolters Kluwer business. All rights reserved.
Purpose:
To systematically review the evidence in support of the purported function of the rotator cuff muscles as dynamic stabilizers of the glenohumeral joint.
Methods:
Electronic searches were conducted using AMED, CINAHL, Medline and SPORT Discus. Studies were required to include at least one characteristic of a stabilizer muscle. Quality analysis was completed by two assessors independently. Data were extracted for four main characteristics of stabilizer muscles: (1) moment arm length, (2) onset of muscle activity, (3) joint stiffness as measured by contribution of muscle activity to prevent joint translation, (4) co-contraction as demonstrated by electromyography muscle activity and co-activation ratio.
Results:
Twenty of the 1726 identified studies were selected for the review. Rotator cuff muscles can limit joint translation (five studies) and contribute to joint stiffness (one study), possess shorter moment arms in some movements (three studies), but show limited evidence for stabilizing characteristics of early onset (seven studies) and co-contraction (seven studies).
Conclusion:
The rotator cuff muscles exhibited some stabilization characteristics but not all. On the basis of our current low to moderate quality evidence, the most likely, but as yet unverified, stabilization role for the rotator cuff muscles appears to be limiting of translation in a direction-specific manner.
Implications for rehabilitation:
Diagnostic tests currently used are based largely on the assumption that the muscles of the rotator cuff can be individually recruited as prime movers. Our findings demonstrate the need for more research into the proposed stabilizing mechanisms of the rotator cuff muscles to increase diagnostic accuracy and more targeted shoulder rehabilitation programs. It may be that the rotator cuff muscles have a role in limiting glenohumeral joint translation which is not reflected in the current diagnostic tests and rehabilitation protocols. Further research is required to establish this stabilizing characteristic in living subjects. Knowledge of the contribution of rotator cuff muscle activation in limiting joint translation may be an important aspect in properly assessing and quantifying the proposed function of the rotator cuff muscles as dynamic stabilizers of the shoulder joint.
This study has investigated the reliability of an isokinetic testing protocol for the shoulder rotators in the scapular plane to estimate the minimum variation of rotator moment needed to detect a significant change between two tests. Concentric and eccentric actions of shoulder internal and external rotation were assessed in a group of 31 male students. Measurements were performed on the dominant and non-dominant sides, at 60 and 120°·s-1, using an isokinetic dynamometer. Each volunteer was assessed in the seated position, with the arm at 45° of abduction and 30° of horizontal adduction. The intraclass correlation coefficient (ICC 3,1), the standard error of measurement (SEM) and the limits of agreement (LOA) were used to determine inter-session reliability and the magnitude of the measurement error for gravity corrected peak and average moment. Moderate to high ICC values (0.76-0.93) were observed for all measured variables. The measurement error associated with repeated measures ranged between 3.9-13.3 Nm. Both SEM and LOA revealed greater measurement errors for peak compared to average moment, eccentric compared to concentric actions, and internal compared to external rotation. The findings of the present study suggested that decline or improvement in isokinetic shoulder rotator moment should only be considered as a significant response to a pathology or an intervention, when the moment data obtained in consecutive repeated measures is lower or greater than the measurement error.
The concept of using tests such as the straight leg raise and prone knee bend to stress “dura” or what Maitland (1978) has termed “pain sensitive structures within the vertebral canal” is believed to be an oversimplification of the true anatomical and biomechanical facts. This paper expands this concept to embrace the nervous system as a whole. It introduces the term adverse mechanical tension of the nervous system to explain how pathology affects the normal movement and biomechanics of the nervous system and its surrounding tissues. Mechanisms of sign and symptom production based on current literature are also put forward.
The standard or “base” tension tests and relevant biomechanics are reviewed and some new variations/combinations described. The key feature of this approach is to understand basic principles of tension testing and to be able to apply them to a wide variety of clinical presentations.
Key features identifying typical signs, symptoms and history of disorders demonstrating adverse mechanical tension of the nervous system are addressed. An approach to “musculoskeletal pain” embracing a broader outlook to all possible sources of presenting symptoms is highlighted as the “component concept”. The treatment principles of presentations showing signs of adverse mechanical tension of the nervous system are outlined, and clarified by many clinical examples. © 1989, The Chartered Society of Physiotherapy. All rights reserved.
The upper extremity is vulnerable to injury during the baseball pitch because of the repetitious nature of the action, the extremes in range of motion, and the high angular velocities and torques generated at the shoulder and elbow. Hence this study was designed to describe the muscle-firing patterns through fine-wire electromyography in 29 muscle bellies in the upper extremities of skilled pitchers during the fastball pitch. The results demonstrated that the muscles functioned with precise timing for joint stabilization to prevent injury, joint activation to transfer forces to the ball, and joint deceleration to dissipate forces after ball release. The synchrony of reciprocal and sequential muscle contraction necessary to accomplish these functions was clearly evident. This study provides a better understanding of the coordinated sequence of muscle activity during the throwing motion; this understanding is crucial to the development of exercise protocols and surgical procedures used for treatment and prevention of shoulder and elbow injuries in the throwing athlete.
This paper presents a general approach to the analysis of functional MRI time-series from one or more subjects. The approach is predicated on an extension of the general linear model that allows for correlations between error terms due to physiological noise or correlations that ensue after temporal smoothing. This extension uses the effective degrees of freedom associated with the error term. The effective degrees of freedom are a simple function of the number of scans and the temporal autocorrelation function. A specific form for the latter can be assumed if the data are smoothed, in time, to accentuate hemodynamic responses with a neural basis. This assumption leads to an expedient implementation of a flexible statistical framework. The importance of this small extension is that, in contradistinction to our previous approach, any parametric statistical analysis can be implemented. We demonstrate this point using a multiple regression analysis that tests for effects of interest (activations due to word generation), while taking explicit account of some obvious confounds.
The ability to identify pitchers at risk for injury could be valuable to a professional baseball organization. To our knowledge, there have been no prior studies examining the predictive value of preseason strength measurements.
Preseason weakness of shoulder external rotators is associated with increased risk of in-season throwing-related injury in professional baseball pitchers.
Cohort study (prognosis); Level of evidence, 2.
Preseason shoulder strength was measured for all pitchers in a professional baseball organization over a 5-year period (2001-2005). Prone internal rotation (IR), prone external rotation (PER), seated external rotation (SER), and supraspinatus (SS) strength were tested during spring training before each season. The players were then prospectively followed throughout the season for incidence of throwing-related injury. Injuries were categorized on an ordinal scale, with no injury, injury treated conservatively, and injury resulting in surgery delineated 0, 1, and 2, respectively. Subset analyses of shoulder injuries and of players with prior surgery were also performed. The association between strength measurements and injury was analyzed using Spearman rank correlation.
A statistically significant association was observed for PER strength (P = .003), SER strength (P = .048), and SS strength (P = .006) with throwing-related injury requiring surgical intervention. Supraspinatus strength was also significantly associated with incidence of any shoulder injury (P = .031). There was an association between the ratio of PER/IR strength and incidence of shoulder injury (P = .037) and some evidence for an association with overall incidence of throwing-related injury (P = .051). No associations were noted in the subgroup of players with prior surgery.
Preseason weakness of external rotation and SS strength is associated with in-season throwing-related injury resulting in surgical intervention in professional baseball pitchers. Thus, preseason strength data may help identify players at risk for injury and formulate strengthening plans for prevention.
Forward head and rounded shoulder posture (FHRSP) is theorized to contribute to alterations in scapular kinematics and muscle activity leading to the development of shoulder pain. However, reported differences in scapular kinematics and muscle activity in those with forward head and rounded shoulder posture are confounded by the presence of shoulder pain. Therefore, the purpose of this study was to compare scapular kinematics and muscle activity in individuals free from shoulder pain, with and without FHRSP. Eighty volunteers were classified as having FHRSP or ideal posture. Scapular kinematics were collected concurrently with muscle activity from the upper and lower trapezius as well as the serratus anterior muscles during a loaded flexion and overhead reaching task using an electromagnetic tracking system and surface electromyography. Separate mixed model analyses of variance were used to compare three-dimensional scapular kinematics and muscle activity during the ascending phases of both tasks. Individuals with FHRSP displayed significantly greater scapular internal rotation with less serratus anterior activity, during both tasks as well as greater scapular upward rotation, anterior tilting during the flexion task when compared with the ideal posture group. These results provide support for the clinical hypothesis that FHRSP impacts shoulder mechanics independent of shoulder pain.
Clinical Measurement-Validity.
Validity of the JTech PowerTrack II hand-held dynamometer (JTech; JTech Medical, Salt Lake City, UT) for measuring shoulder strength has yet to be established.
To examine the concurrent validity of isometric strength scores obtained with the JTech PowerTrack II, and on a stationary dynamometer, the LIDO WorkSET (LIDO; LoredanBiomedical, West Sacramento, CA).
Thirty-eight subjects performed three maximal efforts of shoulder flexion, abduction, and external rotation on a single occasion on the two dynamometers. Two testers were randomly assigned to administer the tests.
Pearson correlations between the scores on the two dynamometers (r.0.81) indicated a good concurrent validity. Correlations were similar when the results were subdivided by tester or gender.
This study suggests that either the JTech PowerTrack II or LIDOWorkSET provide comparable scores for shoulder strength. Although not interchangeable because of the differences in units of measurement, the relative conclusions about strength should be similar, regardless of which instrument is used.
Not applicable.
Proper throwing mechanics may enable an athlete to achieve maximum performance with minimum chance of injury. While quantifiable differences do exist in proper mechanics for various sports, certain similarities are found in all overhand throws. One essential property is the utilisation of a kinetic chain to generate and transfer energy from the larger body parts to the smaller, more injury-prone upper extremity. This kinetic chain in throwing includes the following sequence of motions: stride, pelvis rotation, upper torso rotation, elbow extension, shoulder internal rotation and wrist flexion. As each joint rotates forward, the subsequent joint completes its rotation back into a cocked position, allowing the connecting segments and musculature to be stretched and eccentrically loaded. Most notable is the external rotation of the shoulder, which reaches a maximum value of approximately 180 degrees. This biomechanical measurement is a combination of true glenohumeral rotation, trunk hyperextension and scapulothoracic motion. Near the time of maximum shoulder external rotation (ERmax), shoulder and elbow musculature eccentrically contract to produce shoulder internal rotation torque and elbow varus torque. Both the shoulder and the elbow are susceptible to injury at this position. At ball release, significant energy and momentum have been transferred to the ball and throwing arm. After ball release, a kinetic chain is used to decelerate the rapidly moving arm with the entire body. Shoulder and elbow muscles produce large compressive forces to resist joint distraction. Both joints are susceptible to injury during arm deceleration.
To compare the effects of the soft cushion setting with those of the hard cushion setting of a Biodex II isokinetic dynamometer on peak velocity and peak torque with six loads at 23 preset speeds.
Mixed within- and between-groups, repeated-measures design.
Research laboratory of a physical therapy education program.
Each load was strapped onto the right knee attachment of the dynamometer and was dropped through a 100 degrees arc of motion five times at each preset speed using the soft and hard cushion settings.
Peak velocity, peak torque, time to peak velocity, time to peak torque.
Peak velocity was significantly influenced by the cushion setting, the weight dropped, and the preset speed. Maximal peak velocity achieved was 400 degrees/sec. Peak torque was influenced significantly by the cushion setting, the load, and the preset speed. Maximal peak torque measured was 34.99 kg-m.
The rotating shaft of Biodex II dynamometer moved at a slower speed through the entire arc of motion at the soft cushion setting and often failed to achieve a constant, preset speed. Peak torque measured using the soft cushion setting was more variable and therefore questionable.
The Bennett lesion is a mineralization of the posterior inferior glenoid noted in overhead throwing athletes. Although previous studies have debated appropriate treatment of the lesion, no studies have indicated the lesion prevalence in throwing athletes.
The Bennett lesion is more common than previously believed and may represent an asymptomatic finding.
Uncontrolled retrospective review.
Fifty-five asymptomatic major league pitchers underwent routine preseason radiographic screening. Radiographs were reviewed for the presence of a Bennett's lesion. Player demographics, pitching, and baseball records were reviewed to obtain the patient's dominant arm, age, years and innings pitched, and time on the disabled list or surgery.
Twelve pitchers (22%) were noted to have a radiographic Bennett lesion. No statistically significant difference was noted in age, years pitched, or innings pitched between pitchers with and without a Bennett lesion. No player who demonstrated a Bennett lesion required surgical treatment for shoulder pain during his time with the club. Two players required time on the disabled list, but neither player had complaints of posterior shoulder pain.
This lesion is a relatively common finding in major league pitchers. Concomitant pathology should be suspected when evaluating throwers with posterior shoulder pain and this lesion.
We compared normalized trapezius muscle activity and intramuscular balance ratios between overhead athletes with impingement symptoms and non-injured athletes during isokinetic abduction and external rotation movements. Thirty-nine overhead athletes with chronic impingement symptoms and 30 non-injured athletes participated in the study. Electromyographic activity of upper, middle, and lower trapezius was measured during isokinetic abduction and external rotation, using surface electrodes. The results show a significant increase of upper trapezius activity during both movements in the patient group, with decreased activity in the lower trapezius during abduction, and in the middle trapezius during external rotation. Analysis of the intramuscular activity ratios revealed muscle imbalance on the injured side of the patient group for upper/middle trapezius and upper/lower trapezius during abduction, and for all three muscle activity ratios during external rotation. These results confirm the presence of scapular muscle imbalances in patients with impingement symptoms and emphasize the relevance of restoration of scapular muscle balance in shoulder rehabilitation.
The purpose of this study was to investigate evidence of consistency of reported directional coupling patterns among selected studies and to determine its use in manual medical treatment.
The study was a systematic literature review of English-only journals using PubMed and CINAHL. The keywords included "cervical vertebrae," "biomechanics," "coupling," and "three-dimensional movement" and required coupling directional assessment of individual spine segments.
Four 2-dimensional and 8 3-dimensional studies met inclusion criteria. This study found 100% agreement in coupling direction (side flexion and rotation to the same side) in lower cervical vertebral segments (C2-3 and lower) and variation in coupling patterns in the upper cervical segments of occiput-C1 (during side flexion initiation) and C1-2. Dissimilarities may be explained by differences in measurement devices, movement initiation, in vivo vs in vitro specimens, and anatomical variations.
These findings suggest that use of 3-dimensional analyzed cervical coupling patterns for the lower cervical vertebral during apposition and treatment application may show clinical use for manual clinicians. The use of directional coupling based on 2-dimensional cervical coupling patterns or upper cervical spine coupling that addresses C1-2 should be questioned.
Medical Treatment Guideline for Shoulder Diagnosis and Treatment -updated
- M Gary
- L G Franklin
- Hal Stockbridge
- Robert Mootz
- Teresa Cooper
- Bintu Marong
Gary M. Franklin LG, Hal Stockbridge, Robert Mootz, Teresa Cooper,
Bintu Marong. Medical Treatment Guideline for Shoulder Diagnosis
and Treatment -updated May 2018. Washington state department of
labor & industries, 2018
First and last experiments in muscle mechanics
- A V Hill
Hill AV. First and last experiments in muscle mechanics. Cambridge
University Press; 1970