Analysis of the kinetic chain in asymptomatic individuals with and without scapular dyskinesis

Comparing shoulder proprioception, upper extremity dynamic stability, and hand grip strength in overhead athletes with and without scapular dyskinesis

INTRODUCTION

Scapular dyskinesis is prevalent among asymptomatic athletes, particularly those involved in overhead activities, and can significantly impact their neuromuscular control. These changes may impair upper extremity function and strength, elevating the risk of injury. Therefore, it is imperative to investigate how scapular dyskinesis affects shoulder proprioception, upper extremity dynamic stability, and hand grip strength in overhead athletes. This study compared these parameters between overhead athletes with and without scapular dyskinesis.

METHODS

The study included twenty asymptomatic professional overhead athletes with scapular dyskinesis and twenty without scapular dyskinesis, identified using the lateral scapular slide test. In this cross-sectional study, shoulder active joint position sense, serving as shoulder proprioception, was measured using an isokinetic dynamometer. Upper extremity dynamic stability and hand grip strength were evaluated using an upper quarter modified star excursion balance test (UQ-mSEBT) and a handheld dynamometer.

RESULTS

The study found that the shoulder active joint position sense was significantly lower in the scapular dyskinesis group compared to the group without scapular dyskinesis (PExternal Rotation = 0.003, PInternal Rotation < 0.001, and PForward Flexion = 0.002). However, the two groups had no significant differences in UQ-mSEBT and hand grip strength scores.

CONCLUSIONS

The results showed that scapular dyskinesis could affect the sense of shoulder active joint position among asymptomatic overhead athletes. However, it did not affect their upper extremity dynamic stability and hand grip strength.

Motor alterations along the kinetic chain in amateur volleyball and handball athletes with shoulder pain: An observational comparative study

Overhead sports overload the shoulder complex due to movement repetition and the great amount of force created during the athletic motion, which may cause adaptations in the shoulder and lead to shoulder pain. However, overhead movements include the kinetic chain, and alterations in some of the structures throughout the kinetic chain may increase stress on the shoulder complex and be associated with shoulder pain.

PURPOSE

To compare kinetic chain components in overhead athletes with and without shoulder pain.

METHODS

Forty-one volleyball and handball athletes (21 with and 20 without shoulder pain) were included and assessed for hip internal (IR) and external rotation (ER) range of motion (ROM), hip and trunk isometric strength, trunk endurance and neuromuscular control of the lower and upper limbs (Y balance test).

RESULTS

Athletes with shoulder pain showed smaller IR ROM in both hips, lower endurance time for trunk extensors and flexors, decreased reach distance in the anterior and posteromedial direction, as well as a smaller composite score in the Y balance test (p < 0.05).

CONCLUSION

Volleyball and handball athletes with shoulder pain showed changes in ROM throughout the kinetic chain in addition to lower core endurance, and decreased neuromuscular control of lower limbs.

The associations of physical parameters with the Closed Kinetic Chain Upper Extremity Stability Test, the Upper Quarter Y Balance Test, and the Upper Limb Rotation Test in professional overhead athletes

OBJECTIVE

To investigate the associations of glenohumeral internal (IR) and external rotation (ER), horizontal adduction (HA), and thoracic spine rotation ranges of motion (ROM), isometric muscle strength of the shoulder rotators, and trunk muscle endurance with the Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST), the Upper Quarter Y Balance Test (YBT-UQ), and the Upper Limb Rotation Test (ULRT) in overhead athletes.

DESIGN

Cross-sectional study.

SETTINGS

Laboratory.

PARTICIPANTS

One hundred twenty-one athletes were enrolled.

MAIN OUTCOME MEASURES

Independent variables were: IR, ER, HA, and thoracic spine rotation ROMs, isometric muscle strength of glenohumeral IR and ER muscles, and trunk muscle endurance. Dependent variables were: CKCUEST, YBT-UQ, ULRT.

RESULTS

IR ROM of the nondominant side was associated with the CKCUEST, the YBT-UQ, and the ULRT. IR muscle strength of the dominant side was associated with the CKCUEST and the ULRT. Trunk flexor and lateral endurance of the dominant side were associated with the CKCUEST and the YBT-UQ, respectively.

CONCLUSIONS

Many of the physical parameters influencing scores on the CKCUEST and the YBT-UQ are different. Common parameters influence the CKCUEST and ULRT scores, yet more parameters influence the CKCUEST score. We suggest the combined use of the CKCUEST and the YBT-UQ in overhead athletes.

Managing Scapular Dyskinesis

Scapular dyskinesis, the impairment of optimal scapular position and motion, is common in association with shoulder injury. A comprehensive evaluation process can show the causative factors and lead to effective treatment protocols. The complexity of scapular motion and the integrated relationship between the scapula, humerus, trunk, and legs suggest a need to develop rehabilitation programs that involve all segments working as a unit rather than isolated components. This is best accomplished with an integrated rehabilitation approach that includes rectifying deficits in mobility, strength, and motor control but not overtly focusing on any one area.

What factors contribute to the Scapular Assistance Test result? A classification and regression tree approach

The aim of this study was to determine predictive factors related to the Scapular Assistance Test in individuals with shoulder pain during arm elevation, and to analyze how these predictors interact in a nonlinear manner to discriminate the result of a positive and negative Scapular Assistance Test. Eighty-four individuals with shoulder pain with positive (n = 47, average age 38.4 years) and negative (n = 37, average age 37.8 years) Scapular Assistance Test completed the study. Demographic data, affected shoulder, pain duration, pain at rest, angular onset of pain, scapular dyskinesis, serratus anterior and lower trapezius muscle strength, Disabilities of Arm, Shoulder and Hand questionnaire and Pain Catastrophizing Scale were assessed in all participants. The Classification and Regression Tree analysis was used to determine which factors would predict the occurrence of a positive or negative Scapular Assistance Test and possible interactions among them. The resulting tree presented seven levels that combine the following variables: angular onset of pain, presence of scapular dyskinesis, pain catastrophizing, serratus anterior and lower trapezius muscle strength. The angular onset of pain during arm elevation was the main predictor of a positive Scapular Assistance Test selected by the Classification and Regression Tree. This study indicates that the Scapular Assistance Test result may be explained not only by biomechanical variables, but also by psychological factors. Disability of the upper limbs does not seem to contribute to the Scapular Assistance Test result.

Nonoperative Management of Traumatic Acromioclavicular Joint Injury: A Clinical Commentary with Clinical Practice Considerations

Traumatic injuries of the acromioclavicular joint result in pain and potentially long-term alterations in scapulohumeral rhythm that occurs due to disruption of the clavicular strut function which is integral to scapular kinematics. Nonoperative treatment remains a valid option in most acromioclavicular joint injuries with the potential of minimizing pain and restoring scapulohumeral rhythm. However, few studies have provided nonoperative treatment details. Therefore, the purpose of this clinical commentary is to discuss the rationale, indications, and techniques of nonoperative treatment and present an organized approach for evaluating and managing such patients based on the best available evidence. Attention will be focused on identifying the treatment methods employed and the results/outcomes of such treatments.

Level of Evidence

5.

Motor alterations in the kinetic chain in individuals with chronic shoulder pain

BACKGROUND

Shoulder pain may be related to biomechanical dysfunctions in the kinetic chain.

OBJECTIVE

To compare the mobility and muscular endurance of thoracolumbar spine and hip, and the neuromuscular control of the lower extremity of individuals with and without shoulder pain and to determine the discriminative capacity between groups of these variables.

DESIGN

A cross-sectional study.

METHOD

One hundred and two individuals with and without shoulder pain were evaluated to range of motion (ROM) of the thoracolumbar spine and hips, the muscular endurance time of the thoracolumbar spine and hips muscles, and the neuromuscular control of the lower extremity, by the Star Excursion Balance Test (SEBT).

RESULTS

Individuals with shoulder pain presented lower ROM and muscular endurance time in all tests evaluated (p < 0.01-p = 0.03), greater perception of pain during all ROM and muscle endurance (p < 0.01-p = 0.04) evaluations, and less neuromuscular control of the lower extremity in the compound reach (p < 0.01-p = 0.01), anterior and posteromedial (p < 0.01-p = 0.04) directions of the SEBT on both sides. The anterior reach direction of the SEBT of the contralateral limb to the shoulder pain (AUC=0.80, cut-off point=47.7%) presented excellent capacity to discriminate individuals with shoulder pain, while the other variables showed between acceptable and small capacity (AUC=0.58-0.76).

CONCLUSION

Individuals with chronic shoulder pain presented alterations in joint mobility, muscular endurance time of the thoracolumbar spine and hips and neuromuscular control of the lower extremity. The anterior reach of the SEBT of the contralateral limb showed excellent discriminative capacity.

Electromiographic activity during single leg jump in adolescent athletes with chronic ankle instability: A pilot study

Chronic ankle instability (CAI) is a common condition in athletes, which can alter the muscular activity of lower limb during jump. The objective of the study was to verify the magnitude of activation, onset timing and order of recruitment of the proximal and local muscles to the ankle of young athletes with CAI during a single leg vertical jump. Thirty-seven athletes were selected and divided into: 1) CAI group and 2) control group. An electromyographic evaluation was performed during the jump on force plate. The muscles evaluated were the proximal muscles - gluteus medius (GMed), rectus femoris (RF) and local ankle muscles - tibialis anterior (TA), peroneus longus (PL) and lateral gastrocnemius (LG). In propulsion, the CAI group showed early activation of all evaluated muscles, when compared to control group (p = 0.05). No diferences were found between groups concerning magnitude of electromyographic signal and order of muscle recruitment. During landing, an increase in magnitude of the electromyographic signal of TA in the CAI group was observed and no diferences were found between groups for onset activation and order of muscle recruitment. The results can be applied to athletes' rehabilitation through specific neuromuscular control exercises, such as reaction time and local and proximal joint stabilization to optimize muscle performance and injury incidence. Therefore, in the single leg vertical jump athletes with CAI presented higher activation of the TA in the landing and an early activation of the GMed, RF, TA, PL and LG in propulsion in relation to control group.

Mirror Cross-Exercise on a Kinetic Chain Approach Improves Throwing Performance in Professional Volleyball Athletes With Scapular Dyskinesis

CONTEXT

Volleyball players have shown to be at an increased risk of developing scapular dyskinesis. The kinetic chain exercise approach has gained a lot of attention because of its claims to provide an improved motor control and scapular kinematics. A form of cross exercise, known as mirror therapy, may enhance the effects of a kinetic chain exercise approach in throwing performance.

OBJECTIVE

To examine the effects of mirror cross exercise (MCE), based on a kinetic chain exercise approach in the throwing performance of volleyball athletes with scapular dyskinesis.

DESIGN

Randomized controlled trial.

SETTING

Biomechanics laboratory.

METHODS

39 volleyball players with scapular dyskinesis were randomly allocated into 3 groups. The first group completed a 6-week kinetic chain approach (KCA group), the second group completed a kinetic chain exercise approach program in addition to MCE group, and the control group followed only their regular training program. Before and after delivering both interventions, throwing accuracy, speed, and force were determined while measuring the ground reaction forces of the drive leg during throwing. Two-way mixed analysis of variance investigated the effects of intervention and time and their interaction.

RESULTS

The results showed intervention × time statistically significant interactions for throwing accuracy, speed, and force for the MCE and the KCA groups. Over the 6-week training period, the MCE and the KCA groups showed significant improvements in throwing accuracy (P < .01) and speed (P < .01), while the ground reaction forces did not change (P > .05). Throwing force increased significantly in the MCE group (P = .01). Between-group comparison showed statistically significant improvements in the throwing accuracy for the MCE and KCA groups against the control group (P < .01) at posttesting. The MCE demonstrated superior results over the KCA in the aforementioned measures.

CONCLUSIONS

This study suggests that the addition of MCE in a KCA program enhances energy transfer throughout the distal and proximal segments, thus improving kinetic chain recruitment and potentially preventing shoulder pathology.

The adjunctive benefits of mirror cross education on kinetic chain exercise approach in volleyball athletes with scapular dyskinesis

BACKGROUND

Volleyball players as overhead athletes have the highest risk of developing Scapular Dyskinesis. The kinetic chain exercise-approach has gained a lot of attention because of its claims to provide an improved motor control and scapular kinematics. A form of cross exercise, known as mirror therapy, may enhance the effects of a Kinetic-Chain-Approach on scapular posture, upper and lower limb performance. The aim of this study was to investigate the adjunctive benefits of Mirror-Cross-Education in a Kinetic-Chain-Approach, in volleyball athletes with SD.

METHODS

39 professional volleyball athletes were randomly assigned to three groups of 13 each, two experimental, the Mirror-Cross-Education and Kinetic-Chain-Approach, and one control. Both experimental groups performed a Kinetic-Chain-Approach programme, however, the Mirror-Cross-Education group performed the exercise programme with the addition of two mirrors that allowed athletes to observe their opposite non-dyskinetic scapula. Scapular posture asymmetries in cm, the Y-Balance and the Upper-Quarter YBalance after normalizing by limb length the reach distance in each direction, were assessed before and after performing each intervention for 6 weeks.

RESULTS

3x2 two-way Mixed ANOVAs detected significant interactions on scapular posture (p=0.001) on both experimental groups when compared with the control. The Y-Balance and the Upper Quarter Y-Balance scores at both Mirror-Cross-Education and Kinetic-Chain-Approach groups showed significant differences when compared with the control (p<0.05). Overall, variables showed significant superiority of the Mirror-Cross-Education group.

CONCLUSIONS

The Mirror-Cross-Education demonstrated significant effects in scapular posture and in the functional balance tests of volleyball athletes with Scapular Dyskinesis.

Scapular Dyskinesis: From Basic Science to Ultimate Treatment

Background: This study intends to summarize the causes, clinical examination, and treatments of scapular dyskinesis (SD) and to briefly investigate whether alteration can be managed by a precision rehabilitation protocol planned on the basis of features derived from clinical tests. Methods: We performed a comprehensive search of PubMed, Cochrane, CINAHL and EMBASE databases using various combinations of the keywords “Rotator cuff”, “Scapula”, “Scapular Dyskinesis”, “Shoulder”, “Biomechanics” and “Arthroscopy”. Results: SD incidence is growing in patients with shoulder pathologies, even if it is not a specific injury or directly related to a particular injury. SD can be caused by multiple factors or can be the trigger of shoulder-degenerative pathologies. In both cases, SD results in a protracted scapula with the arm at rest or in motion. Conclusions: A clinical evaluation of altered shoulder kinematics is still complicated. Limitations in observing scapular motion are mainly related to the anatomical position and function of the scapula itself and the absence of a tool for quantitative SD clinical assessment. High-quality clinical trials are needed to establish whether there is a possible correlation between SD patterns and the specific findings of shoulder pathologies with altered scapular kinematics.

Comparison of scapular kinematics and muscle strength between those with a positive and a negative Scapular Assistance Test

BACKGROUND

The Scapular Assistance Test was suggested to directly assess the influence of scapular motion on pain and indirectly measure the function of the scapular rotators. However, it is still not clear if individuals with a positive Scapular Assistance Test actually present changes in scapular motion and muscle strength. This study compared scapular kinematics and muscle strength between those with a positive Scapular Assistance Test and those with a negative Scapular Assistance Test.

METHODS

Fifty individuals with shoulder pain were randomly allocated to: positive (n = 25) or negative Scapular Assistance Test (n = 25) group. Scapular kinematics was measured during elevation and lowering of the arm. Strength of the serratus anterior and lower trapezius was also measured. Two-way analysis of variance was used to compare kinematics between groups. Unpaired Student's t-test and Mann-Whitney test were used to compare strength of serratus anterior and lower trapezius, respectively.

FINDINGS

There were no differences (P > 0.05) in scapular internal rotation and upward rotation between both groups. For scapular tilt, there was group main effect (P < 0.05) during elevation and lowering of the arm, whereas the positive Scapular Assistance Test group presented greater scapular anterior tilt. There was no difference (P > 0.05) in strength between groups.

INTERPRETATION

Individuals with a positive Scapular Assistance Test are more likely to present decreased scapular posterior tilt in those with shoulder pain. Strength of the scapular muscles seems to be same in those with a positive and a negative Scapular Assistance Test.

Tuck Jump Assessment as an Indicator for Upper Extremity Injury

The purpose of this study was to determine if tuck jumps can be used as a dynamic movement assessment to ascertain a previous history of upper extremity injury in an overhead throwing sport. Seventy-one youth baseball and softball athletes (28 baseball/43 softball; 12.41±2.22 yrs.; 161.98±13.65 cm; 59.17 ± 14.90 kg) were recruited to participate and were placed in either the previous injury (N=18) or no previous injury (N=53) groups. Kinematic data were collected from jumps 4 through 8 during a trial of 10 tuck jumps performed at 100 Hz using an electromagnetic tracking system (trakSTAR ^TM , Ascension Technologies, Inc., Burlington, VT, USA) synced with the MotionMonitor ^® (Innovative Sports Training, Chicago, IL, USA). A logistic regression showed no significance in trunk flexion or upper leg elevation in the ability to determine upper extremity injury ( χ ² (1, N =71)=3.55, p =0.315). In conclusion, examining only trunk flexion and upper leg elevation during the tuck jump assessment (TJA) is not enough for clinicians to recognize previous upper extremity injury. Even though the body behaves as a kinetic chain, simplifying the dynamic movement assessment while not specifying the type of upper extremity injury is not favorable for the clinician to identify previous injury.