Effects of Deficits in the Neuromuscular and Mechanical Properties of the Quadriceps and Hamstrings on Single-Leg Hop Performance and Dynamic Knee Stability in Patients After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Understanding the role of neuromuscular and mechanical muscle properties in knee functional performance and dynamic knee stability after anterior cruciate ligament reconstruction (ACLR) may help in the development of more focused rehabilitation programs. PURPOSE: To compare the involved and uninvolved limbs of patients after ACLR in terms of muscle strength, passive muscle stiffness, muscle activation of the quadriceps and hamstrings, hop performance, and dynamic knee stability and to investigate the association of neuromuscular and mechanical muscle properties with hop performance and dynamic knee stability. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHOD: The authors studied the quadriceps and hamstring muscles in 30 male patients (mean ± SD age, 25.4 ± 4.1 years) who had undergone unilateral ACLR. Muscle strength was measured using isokinetic testing at 60 and 180 deg/s. Passive muscle stiffness was quantified using ultrasound shear wave elastography. Muscle activation was evaluated via electromyographic (EMG) activity. Hop performance was evaluated via a single-leg hop test, and dynamic knee stability was evaluated via 3-dimensional knee movements during the landing phase of the hop test. RESULTS: Compared with the uninvolved limb, the involved limb exhibited decreased peak torque and shear modulus in both the quadriceps and hamstrings as well as delayed activity onset in the quadriceps (P < .05 for all). The involved limb also exhibited a shorter hop distance and decreased peak knee flexion angle during landing (P < .05 for both). Decreased peak quadriceps torque at 180 deg/s, the shear modulus of the semitendinosus, and the reactive EMG activity amplitude of the semimembranosus were all associated with shorter hop distance (R 2 = 0.565; P < .001). Decreased quadriceps peak torque at 60 deg/s and shear modulus of the vastus medialis were both associated with smaller peak knee flexion angle (R 2 = 0.319; P < .001). CONCLUSION: In addition to muscle strength deficits, deficits in passive muscle stiffness and muscle activation of the quadriceps and hamstrings were important contributors to poor single-leg hop performance and dynamic knee stability during landing. Further investigations should include a rehabilitation program that normalizes muscle stiffness and activation patterns during landing, thus improving knee functional performance and dynamic knee stability.

Effects of Whole-Body Vibration Therapy on Quadriceps Function in Patients With Anterior Cruciate Ligament Reconstruction: A Systematic Review.

CONTEXT: Quadriceps dysfunction is common for patients after anterior cruciate ligament reconstruction (ACLR). Whole-body vibration (WBV) could effectively treat quadriceps dysfunction. OBJECTIVE: To summarize WBV protocols for patients with ACLR and to evaluate the effects of WBV on quadriceps function. DATA SOURCES: PubMed, CINAHL, SportDiscus, Web of Science, Medline, and Embase were searched from inception to January 2020. STUDY SELECTION: Randomized controlled trials recruiting patients with ACLR, using WBV as intervention, and reporting at least 1 of the following outcomes, strength, rate of torque development (RTD), and voluntary activation ratio of quadriceps, were included. STUDY DESIGN: Systematic review. EVIDENCE LEVEL: Level 3. METHODS: This systematic review was reported according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Quality of evidence was determined by PEDro criteria and GRADE system. Participant characteristics, interventions, and the relevant results of the included studies were extracted and synthesized in a narrative way. RESULTS: In total, 8 studies were included. Of these, 2 studies had serious risk of bias. Five of 8 studies implemented a series of WBV program ranging from 2 to 10 weeks in duration, while the other 3 studies implemented a single session of WBV. Eight WBV protocols were reported. The reported outcomes consisted of quadriceps strength, RTD, and central activation ratio. WBV protocols were heterogeneous. Low quality of evidence supported that exclusive conventional rehabilitation was more effective than exclusive WBV therapy in increasing quadriceps strength. Low quality of evidence supported that WBV combined with conventional rehabilitation was more beneficial in increasing quadriceps strength when compared with conventional rehabilitation alone. Very low quality of evidence supported the efficacy of a single session of WBV on quadriceps function. CONCLUSIONS: There is no standardized WBV protocol for patients with ACLR, and the effectiveness of WBV in rehabilitation on quadriceps function remains inconclusive.

Are muscle weakness and stiffness risk factors of the development of rotator cuff tendinopathy in overhead athletes: a systematic review.

BACKGROUND: Underlying muscle weakness and stiffness may increase the risk of developing rotator cuff tendinopathy. This systematic review aims to assess existing prospective studies to summarize whether muscle weakness and stiffness are risk factors for the development of rotator cuff tendinopathy in overhead athletes. METHODS: A systematic search was performed using PRISMA guidelines. Prospective studies measuring muscle strength or stiffness and the incidence of rotator cuff tendinopathy were included. Quality assessment was performed with the Newcastle-Ottawa quality assessment scale. RESULTS: The search yielded six studies, with a total of 523 trained overhead athletes followed up for one season. External rotation (ER) and internal rotation (IR) strength were described as protective factors against the development of rotator cuff tendinopathy. Athletes who did not sustain shoulder injuries had statistically stronger eccentric IR (p < 0.01) and ER (p < 0.05) strength in the pre-season assessment. Muscle stiffness indicated by limited range of motion of <106° for shoulder ER was described as a risk factor with an odds ratio of 1.12 (p < 0.001). Imbalance between ER and IR strength was reported as risk factors for shoulder injuries in two studies, with a relative risk of 2.57 (p < 0.05) reported in one study. Supraspinatus weakness was also reported as a risk factor for shoulder injuries in one study. CONCLUSION: Limited evidence support ER, IR weakness, limited ER range of motion, and very limited evidence support imbalance in ER/IR strength, and supraspinatus weakness as risk factors for rotator cuff tendinopathy in overhead athletes. No existing studies investigated the general population on this topic. Future cohort studies may improve on existing evidence with investigations on the general public, a longer follow-up time, clearly documented injury history, and a stringent diagnosis to rotator cuff tendinopathy.

Decreased passive muscle stiffness of vastus medialis is associated with poorer quadriceps strength and knee function after anterior cruciate ligament reconstruction.

BACKGROUND: Muscle deficits of the quadriceps and hamstrings are common after anterior cruciate ligament reconstruction, and increase the risk of knee reinjury. Muscle stiffness is an important factor for dynamic joint stability. However, the changes in quadriceps and hamstring muscle stiffness and its influence after anterior cruciate ligament reconstruction remain unclear. METHOD: Twenty-five male subjects with anterior cruciate ligament reconstruction and twenty-one matched healthy subjects participated in this study. The passive muscle stiffness of the quadriceps and hamstrings was assessed by shear modulus using ultrasound shear wave elastography. The isokinetic muscle strengths of the quadriceps and hamstrings were tested. Knee function was evaluated by the International Knee Documentation Committee and Lysholm score. Muscle stiffness was compared between limbs via non-parametric tests. Correlation analysis was used to detect the relationship between muscle stiffness, isokinetic muscle strength and knee functional scores. FINDINGS: The involved limb exhibited significantly decreased shear modulus in the vastus medialis compared to the dominant limbs(z = -3.585;P = 0.001;ES = 1.13) and non-dominant limbs(z = -3.551;P = 0.002;ES = 1.24) of healthy controls. The shear modulus of ST was also significantly lower in the involved limb when compared with the contralateral limbs(z = -3.996;P < 0.001;ES = 1.33), dominant limbs(z = -4.477;P < 0.001;ES = 1.65) and non-dominant limbs(z = -4.234;P = 0.001;ES = 1.43) of healthy controls. The shear modulus of the vastus medialis was associated with quadriceps peak torque at 60°/s(r = 0.470; p < 0.001) and knee functional score(r = 0.459; p = 0.021). INTERPRETATION: The passive muscle stiffness of the vastus medialis decreased after anterior cruciate ligament reconstruction, which is associated with poorer quadriceps strength and knee function. The effect of modulation of muscle stiffness on improving knee function warrants future investigation.

Altered Neuromuscular Activity of the Lower-Extremities During Landing Tasks in Patients With Anterior Cruciate Ligament Reconstruction: A Systematic Review of Electromyographic Studies.

CONTEXT: Altered lower-limb biomechanics have been observed during landing task in patients with anterior cruciate ligament reconstruction (ACLR), which increases the risk of secondary anterior cruciate ligament injury. However, the alteration in neuromuscular activity of the lower-extremity during landing task is not clear. OBJECTIVE: To compare the muscle activity pattern assessed by electromyography between the involved limb of patients with ACLR and the contralateral limb or control limb of matched healthy subjects during landing task. EVIDENCE ACQUISITION: Database of PubMed, Ovid, Scopus, and Web of Science from the inception of the databases until July 2019, using a combination of keywords and their variations: (anterior cruciate ligament OR ACL) AND (electromyography OR EMG) AND (landing OR land). Studies that assessed lower-extremity muscle activity patterns during landing task in patients with ACLR and compared them either with the contralateral side or healthy controls were included. EVIDENCE SYNTHESIS: Of the 21 studies, 16 studies reported altered muscle activity pattern during landing tasks when compared with either the healthy controls or the contralateral side. For the specific muscle activity patterns, the majority of the studies showed no significant difference in reactive muscle activity, and comparisons across studies revealed a possible trend toward the early onset of quadriceps and hamstring activity and increased cocontraction of the involved limb. There are inconsistent findings regarding the alteration in muscle timing and preparatory muscle activity. CONCLUSIONS: Patients with ACLR displayed an altered muscle activity pattern during landing tasks, even though they were considered to be capable for sport return. Nevertheless, a firm conclusion could not be drawn due to great heterogeneity in the subject selection and study methods.

The effect of psychological factors on pain, function and quality of life in patients with rotator cuff tendinopathy: A systematic review.

BACKGROUND: Psychological factors may affect the pain level, shoulder function and quality of life in patients with rotator cuff tendinopathy. OBJECTIVE: To systematically review the prevalence of psychological factors reported in patients with rotator cuff tendinopathy; and to determine the association between psychological factors and pain, function and quality of life in patients with rotator cuff tendinopathy. STUDY DESIGN: Systematic review METHODS: Pubmed, Embase, CINAHL and Web of Science were systematically searched from inception to June 2019. Studies that investigated patients with signs and symptoms suggestive of rotator cuff tendinopathy, and reported psychological variables and patient-reported outcome measures including pain, shoulder function or disability and quality of life. RESULTS: A total of 14 studies were included. Our results showed that 22.8%-26.2% of patients with rotator cuff tendinopathy reported depression; 23% reported anxiety; and 70.2%-89% of patients reported sleep disturbance or insomnia. Overall, nine psychological factors were identified to be associated with pain, function and quality of life in patients with rotator cuff tendinopathy. Low-to-moderate quality of evidence suggests that various psychological factors are associated with pain, function and quality of life in patients with rotator cuff tendinopathy CONCLUSION: This review identified various psychological factors may affect the pain level, shoulder function and quality of life in patients with rotator cuff tendinopathy, and the causal relationship warrants future high-quality prospective studies.

Scapular Kinematics in Athletes With and Without Rotator Cuff Tendinopathy: A Systematic Review.

CONTEXT: Rotator cuff tendinopathy is one of the most frequently reported shoulder injuries in athletes of overhead sports. Abnormal scapular kinematics has been proposed as one of the contributing factors of rotator cuff tendinopathy in overhead athletes. OBJECTIVES: To review the literature on 3-dimensional scapular kinematics in overhead athletes with and without rotator cuff tendinopathy. EVIDENCE ACQUISITION: Electronic databases (Cochrane Library, MEDLINE, Embase, and PubMed) were searched from inception to September 2017. In addition, the reference lists of the articles that met the inclusion criteria were also searched. We included studies that compared the changes in 3-dimensional scapular kinematics in athletes with and without rotator cuff tendinopathy. Two reviewers independently examined the quality of studies by using the modified Downs and Black checklist. EVIDENCE SYNTHESIS: A total of 9 studies (a total of 332 athletes, mean age 23.41 [2.62] y) were included in the final analysis. The methodological quality was low (modified Downs and Black checklist = 9/15). Our findings showed a consistent pattern of increased scapular anterior tilting and internal rotation in the dominant shoulders than the nondominant shoulders of athletes who participated in overhead sports. Athletes of overhead sports seem to demonstrate an increase in scapular upward rotation during arm elevation when compared with nonathlete individuals. However, there is no consensus on the scapular kinematics pattern in athletes with rotator cuff tendinopathy when compared with healthy controls. CONCLUSION: Findings demonstrated that changes in scapular kinematics were observed in overhead athletes. However, all the included studies were cross-sectional studies with small sample size and diverse sports participation, whether changes in scapular kinematics may contribute to rotator cuff tendinopathy in overhead athletes warrants more high-quality prospective studies.

Risk factors for rotator cuff tendinopathy: A systematic review and meta-analysis.

OBJECTIVES: To conduct a systematic review and meta-analysis to identify risk and associated factors for symptomatic rotator cuff tendinopathy. DATA SOURCES: PubMed, CINAHL and Scopus were searched from inception to June 2017. STUDY SELECTION: Participants presented with signs and symptoms suggestive of rotator cuff tendinopathy/tendinosis/tendinitis, shoulder impingement syndrome, or subacromial bursitis diagnosed by clinical tests and/or conventional imaging. DATA EXTRACTION: Screening, quality assessment and data extraction were carried out by 2 reviewers. DATA SYNTHESIS: Sixteen studies were included in this review. Overall, 22 factors were identified and 5 factors were explored using meta-analysis. Pooled analyses provided strong evidence that age above 50 years (odds ratio (OR)?=?3.31, 95% confidence interval (95% CI)?=?2.304.76, I2?=?0%, p<0.001) and diabetes (OR?=?2.24, 95% CI?=?1.373.65, I2?=?0%, p?=?0.001) were associated with increased risk of rotator cuff tendinopathy. In addition, moderate evidence showed that work with the shoulder above 90° was associated with increased risk of rotator cuff tendinopathy (OR?=?2.41, 95% CI?=?1.314.45, I2=?83%, p?=?0.005). CONCLUSION: Age above 50 years, diabetes and overhead activities were associated with increased risk of rotator cuff tendinopathy.

Extracorporeal Shock Wave Therapy Immediately Affects Achilles Tendon Structure and Widespread Pressure Pain Thresholds in Healthy People: A Repeated-Measures Observational Study.

OBJECTIVE: Extracorporeal shockwave therapy is a common clinical treatment for tendinopathy, yet negative effects on tendon structure have been shown in animal studies. This study aimed to investigate the effect of extracorporeal shockwave therapy in healthy participants (i.e., no Achilles tendon pain or pathology). DESIGN: This study examined the effect of three bouts of weekly extracorporeal shockwave therapy for 3 wks in 13 healthy participants. Outcomes measures assessed were as follows: (a) Achilles tendon structure, quantified using ultrasound tissue characterization (before and 3 hrs after extracorporeal shockwave therapy), (b) pressure pain thresholds, over the Achilles tendon and common extensor tendon origin (before, immediately after, and 3 hrs after extracorporeal shockwave therapy), and (c) hop pain (before and immediately after extracorporeal shockwave therapy). RESULTS: There was a significant reduction in echo type I (P < 0.05) and increase in echo type II (P < 0.05) at 3 hrs after the first extracorporeal shockwave therapy session that recovered to baseline levels before week 2. There were no significant changes in ultrasound tissue characterization echo pattern observed in subsequent sessions. There were increased pressure pain thresholds immediately after extracorporeal shockwave therapy at the common extensor tendon origin but no significant change at the Achilles tendon. Pressure pain thresholds returned to baseline at 3 hrs after extracorporeal shockwave therapy. There were no significant changes in pressure pain threshold in subsequent sessions. CONCLUSIONS: Extracorporeal shockwave therapy resulted in transient changes to tendon structure and widespread hyperalgesia.

The Effects of Rigid Scapular Taping on the Subacromial Space in Athletes With and Without Rotator Cuff Tendinopathy: A Randomized Controlled Study.

CONTEXT: Reduction of the subacromial space (SAS) during arm elevation may contribute to rotator cuff (RC) tendinopathy. The effects of scapular taping on the SAS in athletes with and without RC tendinopathy are unknown. OBJECTIVE: To investigate the immediate effects of scapular taping on the SAS in athletes with and without RC tendinopathy. DESIGN: Randomized controlled study with repeated measures. SETTING: University laboratory. PARTICIPANTS: A total of 43 male volleyball players (17 asymptomatic and 26 with RC tendinopathy, mean age = 22.9 [3.5] y) participated in the study. INTERVENTION: Three scapular taping protocols-no taping (control), taping with tension (therapeutic taping), and taping without tension (sham taping). MAIN OUTCOME MEASURES: Ultrasound measurements of the SAS with the arm at 0° and 60° of shoulder abduction, and the change in the SAS between 0° and 60° of shoulder abduction (SAS0°-60°) were calculated. RESULTS: Athletes with RC tendinopathy demonstrated larger SAS with therapeutic taping at 60° of shoulder abduction (6.9 [1.9] mm vs 5.8 [1.7] mm, mean difference = 1.1 mm, 95% confidence interval, -1.80 to -0.39, P = .002) when compared with the no taping condition. The tendinopathy group also showed less reduction in the SAS with therapeutic taping during SAS0°-60° (2.0 [1.4] mm vs 2.8 [1.4] mm, P = .02) when compared with the no taping condition. When tape was applied to the scapula in asymptomatic athletes, our results showed a relatively small increase in the SAS with therapeutic taping during arm resting at 0° of abduction when compared with the no taping condition (8.7 [0.9] mm vs 8.3 [0.8] mm, mean difference = 0.4 mm, 95% confidence interval, -0.71 to -0.11, P = .01). CONCLUSIONS: Athletes with RC tendinopathy demonstrated less reduction of the SAS with rigid scapular taping during early arm abduction. Such observation was not evidenced in asymptomatic athletes.

Rotator cuff tendinopathy alters the muscle activity onset and kinematics of scapula.

Athletes with rotator cuff (RC) tendinopathy demonstrate an aberrant pattern of scapular motion which might relate to deficits in the scapular muscles. This study aimed to determine whether alteration in scapular kinematics is associated with deficits in the activity onset of scapular muscles. Forty-three male volleyball players (17 asymptomatic and 26 with RC tendinopathy) joined the study. Three-dimensional scapular kinematics was quantified using an acromial marker cluster method. The activity onset of the upper (UT), middle (MT), and lower trapezius (LT), and serratus anterior (SA) during arm abduction was assessed with electromyography. Athletes with RC tendinopathy demonstrated less scapular upward rotation (6.6±2.3 vs. 8.2±1.1°, p=0.021) in the early phase of shoulder abduction from 0° to 30° when compared to asymptomatic athletes. The tendinopathy group had delayed activity onset of LT (14.1±31.4ms vs. 74.4±45.1ms, p<0.001) and SA (-44.9±26.0ms vs. 23.0±25.2ms, p<0.001) relative to UT when compared to the asymptomatic group. In asymptomatic athletes, earlier activity onset of MT and LT relative to UT was associated with more scapular upward rotation during 0-30° of abduction (r=0.665, p=0.021) and 30-60° of abduction (r=0.680, p=0.015), respectively. Our findings showed the control of the scapular upward rotation is related to the activity onset of the scapular muscles in athletes.

Tendon vascularity in overhead athletes with subacromial pain syndrome and its correlation with the resting subacromial space.

BACKGROUND: Supraspinatus tendinopathy is one of the common causes of subacromial pain syndrome (SAPS) in overhead athletes. Changes in tendon vascularity have been reported in painful tendons; however, the prevalence and distribution have not been investigated in young overhead athletes. METHODS: We conducted a cross-sectional study of 47 overhead athletes (male, 31; female, 16) aged 18 to 36 years with SAPS for >3 months. A sonographer graded the severity of the tendinopathy and area of vascularization. Ultrasound imaging was used to measure supraspinatus tendon thickness, vascularity, and resting subacromial space. A self-written program was used to semiquantify the intensity of vascularity, expressed as the vascular index. RESULTS: The majority (87.2%) of the participants had signs of tendinopathy in the supraspinatus tendon, and 40 (85.1%) of the tendinopathic tendons had vascularity. The majority (66.0%) of the vascularized subjects presented with minimal increase in vascularity, and 19.1% had moderate to severe vascularization. Most (79.2%) of the vascularization was observed in the pericortical region. The vascular index was negatively correlated with the resting subacromial space in male athletes with a reduced subacromial space (ρ = -0.63; P = .038). CONCLUSION: Of overhead athletes with SAPS, 87.2% had supraspinatus tendinopathy with minimal to moderate vascularization, with the majority of vascularization occurring in the pericortical region. In male athletes with a reduced subacromial space, greater vascularity in the supraspinatus tendon was associated with a smaller resting subacromial space.

Effects of scapular taping on the activity onset of scapular muscles and the scapular kinematics in volleyball players with rotator cuff tendinopathy.

OBJECTIVES: To examine the effect of scapular taping on the activity onset of scapular muscles and the scapular kinematics during arm elevation in volleyball players with rotator cuff (RC) tendinopathy. DESIGN: Randomized placebo-controlled repeated measures METHODS: Twenty-six male volleyball players with RC tendinopathy (mean age=23.6±3.3years) participated in the study. Electromyography (EMG) activity onset of upper trapezius (UT), middle trapezius (MT), lower trapezius (LT) and serratus anterior (SA) and the three-dimensional scapular kinematics quantified by using an acromial marker cluster method were compared with three scapular taping protocols, namely, no taping, therapeutic taping, and placebo taping. RESULTS: The MT, LT and SA activated significantly earlier in both therapeutic taping (all p<0.005) and placebo taping conditions than no taping conditions (all p<0.002). There was a small increase in the scapular upward rotation when therapeutic taping and no taping conditions were compared (p=0.007). CONCLUSIONS: Scapular taping may enhance the neuromotor control of the scapular muscles. Whether it provides adequate support for normal scapular kinematics during arm movement in athletes with RC tendinopathy await for further studies.

Increased Upper Trapezius Muscle Stiffness in Overhead Athletes with Rotator Cuff Tendinopathy.

Although excessive tension of the upper trapezius (UT) is thought to contribute to rotator cuff tendinopathy, no study examined UT tension in athletes with and without rotator cuff tendinopathy. Here we used UT shear modulus measured using ultrasound shear wave elastography as an index of muscle stiffness/tension. The aims of this study were twofold: 1) to determine whether the UT muscle shear modulus is altered in athletes with rotator cuff tendinopathy compared to asymptomatic athletes, and 2) to detect optimal cut-off points of UT shear modulus in identifying athletes with rotator cuff tendinopathy. Forty-three male volleyball players (17 asymptomatic and 26 with rotator cuff tendinopathy, mean age = 22.9±3.5 years) participated in the study. UT shear modulus was quantified during active arm holding at 30° and 60° of shoulder abduction and passive arm positioning at 0°, 30° and 60° of shoulder abduction. During the active tasks, the UT shear modulus was higher in athletes with rotator cuff tendinopathy than the asymptomatic athletes (p = 0.002), regardless the arm position. During the passive tasks, athletes with rotator cuff tendinopathy exhibited a higher UT shear modulus than asymptomatic athletes only at 0° of shoulder abduction (13.0±2.5 kPa vs 10.2±1.8 kPa, p = 0.001). When considering the active task, an optimal cut-off shear modulus of 12.0 kPa at 30° of shoulder abduction (sensitivity = 0.84, specificity = 0.57, AUC = 0.757, p = 0.008) and 9.5 kPa at 60° of shoulder abduction (sensitivity = 0.88, specificity = 0.67, AUC = 0.816, p = 0.002) was detected. When considering the passive task at 0° of shoulder abduction, a cut-off of 12.2 kPa was found (sensitivity = 0.73, AUC = 0.817, p = 0.001). Findings from the present study show that monitoring passive and active UT muscle shear modulus may provide important information for the prevention/rehabilitation of rotator cuff tendinopathy.

Reduction of the subacromial space in athletes with and without rotator cuff tendinopathy and its association with the strength of scapular muscles.

OBJECTIVES: To compare the reduction of subacromial space (SAS) during arm abduction between overhead athletes with and without rotator cuff (RC) tendinopathy, and to explore the relationship between the strength of scapular muscles with the SAS. DESIGN: Cross-sectional study. METHODS: Sixty-six athletes (33 healthy and 33 with RC tendinopathy, mean age=22.3 years) participated in the study. Ultrasound measurement of the SAS with arm at 0°, 30° and 60° of shoulder abduction were taken, and the maximal isometric force in upper, middle and lower trapezius, and serratus anterior with manual muscle tests (MMT) were assessed using a handheld dynamometer. The change in SAS during arm abduction from 0° to 30° (SAS0°-30°), 30° to 60° (SAS30°-60°) and 0° to 60° (SAS0°-60°) was compared between groups. Differences in force produced with scapular muscles MMT between groups and relationships with reduction in SAS were explored. RESULTS: We found more reduction of the SAS during SAS0°-30° in athletes with RC tendinopathy (0.44±1.22mm) than healthy athletes (-0.06±1.41mm) (p=0.045). Athletes with RC tendinopathy demonstrated significant decrease in all scapular muscles MMT strength when compared to their healthy counterparts (p<0.05). In healthy athletes, a lower middle and lower trapezius MMT strength were moderately associated with a greater reduction in SAS during 0° to 30° (r=-0.445, p=0.016 and r=-0.423, p=0.022, respectively) and 0° to 60° of shoulder abduction (r=-0.415, p=0.018 and r=-0.504, p=0.003, respectively). CONCLUSIONS: Athletes with RC tendinopathy demonstrated more reduction in the SAS during early arm abduction. Decreased strength of middle and lower trapezius was related to reduction of the SAS.

Quantitative estimation of muscle shear elastic modulus of the upper trapezius with supersonic shear imaging during arm positioning.

Pain and tenderness of the upper trapezius are the major complaints among people with chronic neck and shoulder disorders. Hyper-activation and increased muscle tension of the upper trapezius during arm elevation will cause imbalance of the scapular muscle force and contribute to neck and shoulder disorders. Assessing the elasticity of the upper trapezius in different arm positions is therefore important for identifying people at risk so as to give preventive programmes or for monitoring the effectiveness of the intervention programmes for these disorders. This study aimed to establish the reliability of supersonic shear imaging (SSI) in quantifying upper trapezius elasticity/shear elastic modulus and its ability to measure the modulation of muscle elasticity during arm elevation. Twenty-eight healthy adults (15 males, 13 females; mean age = 29.6 years) were recruited to participate in the study. In each participant, the shear elastic modulus of the upper trapezius while the arm was at rest and at 30° abduction was measured by two operators and twice by operator 1 with a time interval between the measurements. The results showed excellent within- and between-session intra-operator (ICC = 0.87-0.97) and inter-observer (ICC = 0.78-0.83) reliability for the upper trapezius elasticity with the arm at rest and at 30° abduction. An increase of 55.23% of shear elastic modulus from resting to 30° abduction was observed. Our findings demonstrate the possibilities for using SSI to quantify muscle elasticity and its potential role in delineating the modulation of upper trapezius elasticity, which is essential for future studies to compare the differences in shear elastic modulus between normal elasticity and that of individuals with neck and shoulder disorders.

Ultrasound measurements on acromio-humeral distance and supraspinatus tendon thickness: test-retest reliability and correlations with shoulder rotational strengths.

OBJECTIVES: To establish the test-retest reliability of ultrasound measurements on acromio-humeral distance (AHD) and supraspinatus tendon thickness; and to explore their relationships with shoulder rotational strengths. DESIGN: Test-retest observational study. METHODS: Thirty-seven individuals (age: 21.5±1.4 years) participated in this study. Twenty-four were University volleyball players with 15 healthy and 9 players with shoulder impingement syndrome (SIS). Thirteen participants were healthy untrained individuals. Ultrasound measurements of AHD and supraspinatus tendon thickness were taken, and isokinetic testing of concentric shoulder internal rotation (IR) and external rotation (ER) at a speed of 90°/s was performed. RESULTS: The measurement of the AHD and the supraspinatus tendon thickness indicated excellent reliability (ICC=0.922, and ICC=0.933 respectively), and the minimum detectable difference (MDD) were 2.10mm and 0.64 mm respectively. A cut-off AHD distance of 23.9 mm had a sensitivity of 0.67 and specificity of 0.71 (area under curve (AUC): 0.70; p=0.05) in identifying individuals with and without SIS. Hence, individuals with AHD larger than 23.9 mm had greater possibility of having SIS. Positive correlations were found in AHD with supraspinatus tendon thickness (r=0.36, p<0.05) and shoulder external rotational strengths (r=0.47-0.62, all p<0.05) and ER/IR ratios (r=0.56-0.58, all p<0.05). CONCLUSIONS: Ultrasound measurements of AHD and tendon thickness have excellent reliability. The reported cut-off AHD highlighted the potential role of ultrasound measurements in volleyball players for early identification of SIS. The AHD was related to the supraspinatus tendon thickness and shoulder external rotation strengths. Our findings provide a scientific basis for muscle training in overhead athletes such as volleyball players.

Low-level Taekwondo practitioners have better somatosensory organisation in standing balance than sedentary people.

Sports training, especially for those requiring fast and skilled movements have been reported to improve one's postural control, but the underlying sensory integration mechanism is unknown. The purpose is to explore the sensory organisation strategies for maintaining standing balance in Taekwondo practitioners, and to examine the quasi-static and dynamic balance performance in subjects with and without TKD training. Case-control study was used as a study design. Eleven subjects with low level of Taekwondo training for 1-3 years, and eleven sedentary healthy subjects were assessed with the sensory organisation tests (SOT) under six visual and somatosensory input conditions and their balance upon landing from self- or operator-triggered drop test with the eyes closed condition. The SOT measured the equilibrium scores, whereas the drop test assessed the time to stabilisation (TTS), normalised peak force and distance of antero-posterior and medial-lateral centre of pressure on landing. Results for the SOT test revealed that Taekwondo subjects performed better during stance with eyes closed on a fixed support than the untrained group (p = 0.011). For the drop tests, the untrained group was slower in postural correction as revealed by the longer TTS than the Taekwondo group after the operator-triggered drops (p = 0.018). All subjects had a larger normalised peak force in operator-triggered than self-triggered drops. In conclusion, we observed that people with low-level Taekwondo training have better balance performance than untrained subjects as shown in the SOT results and shorter TTS with the drop test. They may rely more on the somatosensory and vestibular inputs for maintaining balance. People with balance problems may benefit from Taekwondo training.