Dependence of Rotator Cuff Muscle Thickness and Stiffness on Low-Level Contractions: Metrology of the Contraction Level Using Shear-Wave Imaging.

OBJECTIVE: The study aimed to investigate the effects of the level of contraction during isometric shoulder abduction at different abduction angles on muscle thickness and stiffness of the shoulder girdle in asymptomatic individuals. DESIGN: Measurement properties study. SETTING: Biomechanics and motion analysis lab. PARTICIPANTS: Twenty individuals volunteered to participate in this study. MAIN OUTCOME MEASURE: The subjects were tested for morphological and mechanical properties, expressed by thickness and stiffness of the supraspinatus tendon and muscle, and upper trapezius muscle. Moreover, acromiohumeral distance was also evaluated using B-mode ultrasound and shear-wave elastography. INTERVENTION: The thickness and stiffness of the supraspinatus and upper trapezius muscle were assessed at 3 angles of abduction (0°, 60°, and 90°) and 3 levels of contraction (0%, 10%, and 20% of the maximal voluntary isometric contraction) using ultrasonography with shear-wave imaging. Moreover, the acromiohumeral distance was measured to establish the occupation ratio during passive movement. RESULTS: The supraspinatus and upper trapezius muscle thickness and stiffness were significantly greater at 60° shoulder abduction compared with 0°, and 90° compared with 60°, as well as significantly greater at 20% maximal voluntary isometric contraction compared with 0% and 10% maximal voluntary isometric contraction. Thickness and stiffness were significantly greater in the supraspinatus compared with the upper trapezius muscle at all 3 angles of shoulder abduction for all 3 level of contractions. The acromiohumeral distance decreased significantly from 0° to 60° and from 60° to 90°. CONCLUSION: Morphological and mechanical properties of the supraspinatus and upper trapezius muscles depended on the relative level of muscle contraction and the angle of shoulder abduction.

Ultrasound characteristics of soft tissues near sacroiliac joints and in the lumbar region of patients with ankylosing spondylitis.

AIMS: To investigate the musculoskeletal morphomechanical properties (i.e., the thickness and elastic modulus) and the total count of power Doppler signals near the sacroiliac joints in patients with ankylosing spondylitis (AS) and non-AS individuals. MATERIAL AND METHODS: Twenty participants with AS [median age (interquartile range): 31.7 (11.04) years] and 19 controls [36.3 (10.5) years] with no AS history were recruited. Bilateral ultrasound image acquisition was performed, including the short posterior sacroiliac ligament, interosseous sacroiliac ligament, long posterior sacroiliac ligament, iliolumbar ligament, proximal piriformis muscle, and sacrotuberous ligament. The intraclass correlation coefficients (ICC) of ultrasound parameters, laboratory test results of human leukocyte antigen B27, C-reactive protein, and erythrocyte sedimentation rate, and self-reported physical and disease activity scores were also obtained. RESULTS: The ligaments and piriformis muscle were thicker and stiffer (greater elastic modulus) in participants with AS than in non-AS participants (all p<0.01). The measurements showed good or excellent reliability (all ICC(3,1) >0.85). The numbers of power Doppler signals detected in the iliolumbar ligament, proximal piriformis muscle, and sacrotuberous ligament were higher in participants with AS than in non-AS participants (all p<0.001). A correlation was identified between disease duration and the elastic modulus of the piriformis muscle (r=0.640, p=0.003). CONCLUSION: We conclude that the ligaments and proximal piriformis muscle of AS participants have increased thickness, elastic modulus, and power Doppler signal than those of non-AS individuals. These reliable findings may serve as potential markers for the early diagnosis of AS and for assessing medication effects.

Cortical excitability and multifidus activation responses to transcranial direct current stimulation in patients with chronic low back pain during remission.

Evidence indicates that patients with chronic low back pain (CLBP) have lumbar multifidus muscle (LM) activation deficit which might be caused by changes in cortical excitability. Anodal transcranial direct current stimulation (a-tDCS) can be used to restore cortical excitability. This study aimed to (1) determine the immediate effects of a-tDCS on the cortical excitability and LM activation and (2) explore the relationship between cortical excitability and LM activation. Thirteen participants with CLBP during remission and 11 healthy participants were recruited. Cortical excitability (peak-to-peak motor evoked potential amplitude; P2P and cortical silent period; CSP) and LM activation were measured at pre- and post-intervention. We found significant difference (P < 0.05) in P2P between groups. However, no significant differences (P > 0.05) in P2P, CSP and LM activation were found between pre- and post-intervention in CLBP. The CLBP group demonstrated significant correlation (P = 0.05) between P2P and LM activation. Although our finding demonstrates change in P2P in the CLBP group, one-session of a-tDCS cannot induce changes in cortical excitability and LM activation. However, moderate to strong correlation between P2P and LM activation suggests the involvement of cortical level in LM activation deficit. Therefore, non-significant changes could have been due to inadequate dose of a-tDCS.

Validation of the Efficacy of Ultrasound Speckle Tracking in Measuring Tendon Gliding After Finger Flexor Tendon Repair.

OBJECTIVE: Restricted tendon gliding is commonly observed in patients after finger flexor tendon (FFT) repair. The study described here was aimed at quantifying the amount of FFT gliding to evaluate the recovery of post-operative tendons using a 2-D radiofrequency (RF)-based ultrasound speckle tracking algorithm (UST). METHODS: Ex vivo uniaxial tensile testing of porcine flexor tendons and in vivo isometric testing of human FFT were implemented to verify the efficacy of UST beforehand. The verified UST was then applied to the patients after FFT repair to compare tendon gliding between affected and healthy sides and to investigate its correlation with the joint range of motion (ROM). RESULTS: Excellent validity was confirmed with the average R2 value of 0.98, mean absolute error of 0.15 ± 0.08 mm and mean absolute percentage error of 5.19 ± 2.43% between results from UST and ex vivo testing. The test-retest reliability was verified with good agreement of ICC (0.90). The affected side exhibited less gliding (p = 0.001) and smaller active ROM (p = 0.002) than the healthy side. Meanwhile, a significant correlation between tendon gliding and passive ROM was found only on the healthy side (ρ = 0.711, p = 0.009). CONCLUSION: The present study provides a promising protocol to evaluate post-operative tendon recovery by quantifying the amount of FFT gliding with a validated UST. FFT gliding in patients with different levels of ROM restriction should be further explored for categorizing the severity of tendon adhesion.

Effects of Ving Tsun sticking-hand training on lower limb sensorimotor performance among community-dwelling middle-aged and older adults: a randomized controlled trial.

BACKGROUND: To explore the effects of Ving Tsun (VT) sticking-hand training on knee joint proprioception and leg muscular performance among community-dwelling middle-aged and older adults. METHODS: Thirty-three middle-aged and older adults were randomly assigned to either the VT or control group. The VT group received sticking-hand training twice/week for 3 months. Data were collected before and after the intervention period. The primary outcome was knee joint repositioning error, which was measured using knee joint active repositioning tests. The secondary outcomes included the maximum muscle strength and time to maximum muscle strength of the major leg muscles. RESULTS: No significant group, time, or group-by-time interaction effects were found for the knee joint repositioning error (p > 0.05). The maximum muscle strength of the knee flexors increased over time in the VT group only (p = 0.038). In addition, the time to maximum muscle strength in the hip extensors and flexors increased over time in both groups (p < 0.05). For the knee extensors and flexors, the time to maximum muscle strength increased in the control (p = 0.027) and VT (p = 0.019) groups, respectively, over time. CONCLUSIONS: VT sticking-hand training could improve the maximum muscle strength of the knee flexors but could not attenuate the age-related deterioration in leg muscle contraction speed nor improve knee joint proprioception among community-dwelling middle-aged and older adults. TRIAL REGISTRATION: ClinicalTrials.gov NCT03318289. Registered on 23 October 2017.

Muscle Microcirculatory Responses to Incremental Exercises Are Correlated with Peak Oxygen Uptake in Individuals With and Without Type 2 Diabetes Mellitus.

Background: The role of impaired oxygen extraction on peak oxygen uptake (V̇O2peak) has been extensively studied using noninvasive and indirect methods in both diabetic patients and healthy participants. Methods: A total of 22 participants with type 2 diabetes mellitus [T2DM; median (range) age: 60 (47-70) years] and 22 controls [58 (52-69) years] with no history of diabetes were recruited (reference no. 201812135RINB). Subjects performed an exhaustive incremental exercise and were evaluated using a gas analyzer and near-infrared spectroscopy (NIRS) to determine V̇O2peak and changes in muscle oxygenation (SmO2) in the vastus lateralis, respectively. Measurements were taken at rest, warm-up, a period during exercise when SmO2 reached a minimum saturation plateau, and recovery. The microcirculatory responses of the vastus lateralis muscle during incremental exercise in patients with T2DM were compared with those in control individuals, and the correlation between changes in SmO2 and V̇O2peak was estimated. Results: The diabetic group demonstrated lower V̇O2peak, peak workload, peak heart rate, peak minute ventilation (all P < 0.05), and lower SmO2 during the rest, warm-up, and recovery phases (all P < 0.05) compared with the control group. A correlation was observed between the change in SmO2 between the warm-up and plateau value and the V̇O2peak (r = 0.608, P = 0.006). Conclusions: The results obtained in this study using NIRS support the feasibility of directly measuring changes in muscle SmO2 magnitudes to estimate the contributions of peripheral active muscle to systemic O2 uptake (V̇O2) during incremental exercise.

Individuals With Impaired Lumbopelvic Control Demonstrate Lumbar Multifidus Muscle Activation Deficit Using Ultrasound Imaging in Conjunction With Electrical Stimulation: A Cross-sectional Study.

OBJECTIVE: To determine lumbar multifidus (LM) muscle activation deficits in individuals with impaired lumbopelvic control (iLPC) based on musculoskeletal ultrasound in conjunction with electrical stimulation approach and the correlation between back extension force and LM activation. DESIGN: A cross-sectional study design. SETTING: A university laboratory. PARTICIPANTS: Fifty participants (25 iLPC and 25 no low back pain [NoLBP]) were recruited from the university physical therapy clinic and surrounding areas. MAIN OUTCOME MEASURES: The musculoskeletal ultrasound was used to measure LM thickness at rest, maximum voluntary isometric contraction (MVIC), and electrical stimulation combined with MVIC, and a handheld dynamometer was used to record force during MVIC and electrical stimulation combined with MVIC. These data were used to derive LM activation (LMACT) and percentage force generation (ForceGEN). RESULTS: The iLPC group had significantly lower LMACT (17%) than the NoLBP group (P<.05). No significant difference was seen in ForceGEN between the NoLBP and iLPC groups (P>.05). No significant correlation was seen between LMACT and ForceGEN (P>.05). CONCLUSIONS: The findings support the utility of our protocol to determine LM activation deficits. The lower LM activation in iLPC group suggests that individuals with iLPC were unable to fully recruit the motor units available in LM. Force generation measurements may not be an appropriate approach to determine such deficits in LM.

Cyclic mechanical stretch regulates the AMPK/Egr1 pathway in tenocytes via Ca2+-mediated mechanosensing.

PURPOSE: Mechanical stimuli are essential for the maintenance of tendon tissue homeostasis. The study aims to elucidate the mechanobiological mechanisms underlying the maintenance of tenocyte homeostasis by cyclic mechanical stretch under high-glucose (HG) condition. MATERIALS AND METHODS: Primary tenocytes were isolated from rat Achilles tendon and 2D-cultured under HG condition. The in vitro effects of a single bout, 2-h cyclic biaxial stretch session (1 Hz, 8%) on primary rat tenocytes were explored through Flexcell system. Cell viability, tenogenic gene expression, intracellular calcium concentration, focal adhesion kinase (FAK) expression, and signaling pathway activation were analyzed in tenocytes with or without mechanical stretch. RESULTS: Mechanical stretch increased tenocyte proliferation and upregulated early growth response protein 1 (Egr1) expression. An increase in intracellular calcium was observed after 30 min of stretching. Mechanical stretch phosphorylated FAK, calmodulin-dependent protein kinase kinase 2 (CaMKK2), and 5' adenosine monophosphate-activated protein kinase (AMPK) in a time-dependent manner, and these effects were abrogated after blocking intracellular calcium. Inhibition of FAK, CaMKK2, and AMPK downregulated the expression of Egr1. In addition, mechanical stretch reinforced cytoskeletal organization via calcium (Ca2+)/FAK signaling. CONCLUSIONS: Our study demonstrated that mechanical stretch-induced calcium influx activated CaMKK2/AMPK signaling and FAK-cytoskeleton reorganization, thereby promoting the expression of Egr1, which may help maintain tendon cell characteristics and homeostasis in the context of diabetic tendinopathy.

Patients with low back pain use stiffening strategy to compensate for movement control during active prone hip rotation: A cross-sectional study.

BACKGROUND: New motor adaptation to pain theory suggests that patients with low back pain (LBP) use the lumbopelvic stiffening strategy by redistribution of within and between muscle activities to protect painful structure. This could result in an altered postural control of the lumbopelvic region during active prone hip rotation (PHR). OBJECTIVE: To investigate coordination and timing of lumbopelvic and hip movements, and smoothness of the lumbopelvic control during PHR between participants with and without LBP. METHODS: Eight participants with LBP and eight participants without LBP were recruited. The electromagnetic tracking system was used to record kinematic data during PHR. Cross-correlation between hip rotation and lumbopelvic movement in the transverse plane was calculated. Correlation at zero time-lag, time-lag, correlation at time-lag, and maximal lumbopelvic motion were derived. Frequency of movement disruption was identified. An independent t-test was used in conjunction with the effect size and 95% minimal detectable difference (MDD95) to determine the difference in kinematic parameters. RESULTS: Participants with LBP demonstrated a significant delay (exceeding MDD95) in lumbopelvic motion while nonsignificant frequency of disrupted motion on the painful side PHR demonstrated a trend with a large effect size that exceeded MDD95. There were trends with moderate to large effect sizes and differences exceeding MDD95 in delay of lumbopelvic motion with greater movement disruption on the nonpainful side in participants with LBP. CONCLUSION: Participants with LBP used a lumbopelvic stiffening strategy for postural control to protect painful structures; however, the stiffening might complicate efforts to smoothly control lumbopelvic movement.

Combined neuromuscular electrical stimulation with motor control exercise can improve lumbar multifidus activation in individuals with recurrent low back pain.

Motor control exercise (MCE) is commonly prescribed for patients with low back pain. Although MCE can improve clinical outcomes, lumbar multifidus muscle (LM) activation remains unchanged. Neuromuscular electrical stimulation (NMES) can be used to re-activate motor units prior to MCE which should result in increased LM activation. Therefore, this study aimed to explore the immediate effects of NMES combined with MCE on LM activation and motor performance. Twenty-five participants without low back pain (NoLBP) and 35 participants with movement control impairment (MCI) were recruited. Participants with MCI were further randomized to combined NMES with MCE (COMB) or sham-NMES with MCE (MCE) group. Ultrasound imaging was used to measure LM thickness at rest, maximum voluntary isometric contraction (MVIC), and NMES with MVIC. These data were used to calculate LM activation. Quadruped rocking backward was used to represent motor performance. LM activation and motor performance were measured at baseline and after one-session of intervention. Results showed that both COMB and MCE groups had significantly lower (P < 0.05) LM activation compared with NoLBP group at baseline. Additionally, both COMB and MCE groups demonstrated significant improvement (P < 0.05) in motor performance while COMB group demonstrated significantly greater improvement (P < 0.05) in LM activation compared with MCE group. Individuals with MCI still have persisting LM activation deficit. Our key findings suggest that combined NMES and MCE may have better ability to improve LM activation in individuals with MCI. These findings would support the utility of NMES to induce a priming effect before MCE.

Microcirculatory Responses to Muscle and Tendon Exercises in Individuals With and Without Type 2 Diabetes Mellitus and the Association Between Microcirculatory and Exercise Performance.

Background: This study aimed to measure and compare (1) the microcirculation and microcirculatory responses of the muscles and tendons at rest and during isometric muscle contractions in participants with and without diabetes mellitus (DM) and (2) to determine correlations between microcirculation and muscle strength. Methods: Sixty-three participants with type 2 DM and 42 physically matched controls were recruited. Baseline measurements of the microcirculation of the rectus femoris (RF) and medial gastrocnemius (MG) muscles and patellar (PT) and Achilles tendons (AT), as well as their microcirculatory changes during maximal isometric exercises, were performed and recorded by using near-infrared spectroscopy and a red laser. Data on various laboratory tests (including glycated hemoglobin, triglyceride, high-density cholesterol), the monofilament test, and the ankle-brachial index were also obtained. Results: The baseline measurements indicated that, compared with the controls, the diabetic participants had lower oxygen saturation (SpO2) in their RF and MG muscles (both P < 0.001), and the total hemoglobin in the diabetic PT and AT was higher (P = 0.001 and P = 0.01). The minimal SpO2 levels in the aforementioned muscles during isometric contractions were lower in the diabetes group than in the control group (P ≤ 0.001). Furthermore, there were correlations between the microcirculatory change of the RF muscle and the knee extension force. Conclusions: This study demonstrated the effects of diabetes on the microcirculation of skeletal muscles and tendons during baseline measurements and responses to maximal isometric exercises. The results support the need for preventive strategies for diabetic muscles to prevent adverse complications when performing resistance training.

Neuromuscular control of the ankle during pre-landing in athletes with chronic ankle instability: Insights from statistical parametric mapping and muscle co-contraction analysis.

OBJECTIVE: The present study aimed to compare the neuromuscular control of the muscles around the ankle between athletes with CAI and without history of any ankle sprain (Non-CAI) by using statistic parametric mapping (SPM) and co-contraction analyses. DESIGN: Cross-sectional study; Setting: Laboratory; Participants: 40 athletes (20 CAI, 20 Non-CAI) were pair-matched for age and gender. MAIN OUTCOME MEASURES: Neuromuscular control was examined using surface electromyography (EMG) amplitude and muscle co-contraction 200 ms before foot-contact with the ground during a jump-landing task. RESULTS: The EMG amplitude of tibialis anterior, peroneus longus, and gastrocnemius medialis were analyzed using statistic parametric mapping. The CAI group exhibited decreased EMG amplitude of peroneus longus during preparation for foot-contact. There were no significant co-contraction differences between groups. CONCLUSIONS: Our findings demonstrate that SPM combined with the co-contraction provides a comprehensive EMG analysis to detect the differences of neuromuscular control between athletes with and without chronic ankle instability. Additionally, this finding indicates that CAI contributed to altered neuromuscular control during the pre-landing phase, which may contribute to re-injury mechanisms.

Using neuromuscular electrical stimulation in conjunction with ultrasound imaging technique to investigate lumbar multifidus muscle activation deficit.

Lumbar multifidus muscle (LM) activation deficit has been proposed as a potential underlying mechanism responsible for recurrence episode of low back pain (LBP). The quantification of voluntary LM activation can provide a better understanding of the role of muscle activation deficit in LBP. The objective of this technical report is to propose a new approach using neuromuscular electrical stimulation (NMES) in combination with the ultrasound imaging technique (USI) to investigate the ability of individual to voluntarily activate the LM. We recruited ten participants with a recurrent LBP (rLBP) and twelve participants with no history of LBP (NoLBP). Theoretically, the superimposition of NMES on the LM during maximum voluntary isometric contraction (MVIC) should activate all motor units available in the LM. The percentage of LM activation (%LM) can be calculated by the changes of LM thickness during MVIC, divided by the changes of LM thickness during the combination of MVIC and NMES. This %LM was used to compare between groups. The individuals with rLBP had significantly lower %LM (p < 0.05) compared with the NoLBP counterpart (%LM = 72.4 and 92.9, respectively). Results demonstrate that this new approach can potentially differentiate %LM among individuals with rLBP and NoLBP. This new approach can be potentially used to 1) determine the extent of LM activation deficit, 2) identify the existence of muscle activation deficit in the LM, and 3) objectively measure the effect of the intervention designed to address the LM activation deficit.

Acute and Long-Term Effects of Mechanotherapy on the Outcome After an Achilles Repair: A Prospective Cohort Study With Historical Controls.

OBJECTIVES: To evaluate the effects of vibration on Achilles' tendon microcirculation and characteristics following surgical repair of Achilles' tendon rupture. DESIGN: Cohort study with historical controls. SETTING: A university institute. PARTICIPANTS: Participants (N=32), including 19 (16 men, 3 women; median [range] age: 43.0 [25.0-57.0] years) and 13 (10 men, 3 women; 44.00 [29.0-60.0] years) in the vibration (application to the ball of the foot, 30Hz, 2mm amplitude, 4kg pressure, and self-administration) and control groups, respectively, who underwent unilateral Achilles' tendon repairs were recruited. INTERVENTION: A 4-week vibration intervention in the vibration group. MAIN OUTCOME MEASUREMENTS: The tendon microcirculation was measured after the first session of vibration. The participants were evaluated repeatedly with bilateral follow-up measurements of tendon stiffness, 3 functional outcome tests, and a questionnaire survey. RESULTS: Acute effects of the vibration were observed immediately after the 5-minute vibration (P≤.001). Lower total hemoglobin and oxygen saturation were respectively observed (P=.043) in the repaired legs 3 and 6 months postsurgery in the vibration group as compared with the control group. The vibration group also showed greater tendon stiffness, heel raising height and hopping distance 3 or 6 months postoperation in both the repaired and noninjured legs (all P<.05). The microcirculatory characteristics 2 months postoperation were correlated with the outcomes at 6 months postoperation. CONCLUSIONS: Differences in microcirculatory characteristics and better rehabilitation outcomes were observed in the legs with an Achilles repair that underwent the early vibration intervention.

Chinese Martial Art Training Failed to Improve Balance or Inhibit Falls in Older Adults.

This randomized controlled trial explored the effects of a Ving Tsun (VT) Chinese martial art training program on reactive standing balance performance, postural muscle reflex contraction latency, leg muscle performance, balance confidence and falls in community-dwelling older adults. We randomly assigned 33 healthy older adults to either a VT group (mean age = 67.5 years) or a control group (mean age = 72.1 years). The VT group received two 1-hour VT training sessions per week for three months (24 sessions). Primary outcome measures collected before and after the intervention period were electromyographic muscle activation onset latencies of the hamstring and gastrocnemius and the center of pressure path, length and movement velocity in standing (reactive balance performance). Secondary outcome measures included isometric peak force and time to isometric peak force of the knee extensors and flexors, the Activities-Specific Balance Confidence Scale score, and fall history. Results revealed that the mean gastrocnemius muscle activation onset latency was significantly longer (22.53 ms) in the VT group after the intervention. The peak force of the knee flexors significantly increased (by 1.58 kg) in the control group over time but not in the VT group. The time to reach peak force in the knee flexors was significantly longer (by 0.51 s) in the control group (but not the VT group) at posttest compared with the pretest value. No other significant group, time, or group-by-time interaction effects were noted. We discussed possible reasons for the failure of three months of martial art training to benefit fall risks among these older adults.

Balance control, agility, eye-hand coordination, and sport performance of amateur badminton players: A cross-sectional study.

In this study, balance performance, agility, eye-hand coordination, and sports performance were compared between amateur badminton players and active controls.Thirty young adult badminton players and 33 active controls participated in the study. Static single-leg standing balance (with eyes closed) was measured using a force platform, and dynamic balance was measured using the Y Balance Test (lower quarter). Agility was measured using a hexagon agility test, and eye-hand coordination was measured using a computerized finger-pointing task. Sports performance was quantified by the number of times a shuttlecock fell in a designated area following a badminton serve.The badminton players had superior accuracy in badminton serving (P < .001) relative to the active controls. However, no significant between-group differences were noted in all other outcome variables (P > .05).Amateur badminton players had more favorable sports performance, but not balance performance, agility, or eye-hand coordination, than controls.

Muscular Morphomechanical Characteristics After an Achilles Repair.

BACKGROUND: The purpose of the study was to compare the morphomechanical and functional characteristics during maximal isometric, concentric, and eccentric contractions in the legs of patients that underwent unilateral Achilles tendon repair with those in their noninjured control legs. METHODS: Twenty participants (median age = 38.2 years; range, 21.1-57.3 years) who underwent Achilles repair between 3 and 12 months ago were recruited with the following measures: (1) mechanical stiffness of the aponeurosis and (2) electromyography and medial gastrocnemius fascicle angle and length, standing muscle and tendon length, and height of heel rise with isometric contraction. RESULTS: Compared to the noninjured legs, the repaired legs showed less resting fascicle length, standing muscle length, isometric plantarflexion torque, and heel raise distance ( Ps ranged between .044 and <.001). During the concentric and eccentric phases of the raising and lowering test, the repaired legs demonstrated less fascicle length ( P ≤ .028) but greater tendinous tissue length ( Ps ranged between .084 and <.001) and fascicle angle ( Ps ranged between .247 and .008) and fewer change magnitudes of the fascicle length and tendinous tissue length ( P ≤ .003). The change magnitudes of the morphological characteristics showed correlations with the torque or distance. CONCLUSION: Selecting the appropriate surgical repair and rehabilitation for Achilles tendon ruptures is recommended for restoring the length and mechanical strength of the muscle-tendon unit of plantar-flexion muscles. LEVEL OF EVIDENCE: Level III, comparative study.

Effects of kinesiology taping on shoulder girdle muscle activity and sports performance during badminton forehand overhead strokes in amateur badminton players with shoulder impingement syndrome.

BACKGROUND: This study aimed to examine the influence of kinesiology taping (KT), various overhead stroke techniques, and their interactions on shoulder girdle muscle activity and on sports performance in badminton players with shoulder impingement syndrome. METHODS: Twenty-five amateur badminton players with shoulder impingement syndrome participated in the study. Each was exposed to two KT conditions (no taping and taping) while performing four badminton strokes (defensive clear, attacking clear, smash, and drop shot) in a random order. Surface electromyography (EMG) was used to evaluate the activity of the pectoralis major, anterior deltoid, infraspinatus, and latissimus dorsi muscles. The EMG data are expressed as a percentage of the EMG amplitude recorded during a maximal voluntary isometric contraction of the respective muscles. The shuttlecock speed was also measured via video analysis. RESULTS: The pectoralis major, anterior deltoid, infraspinatus, and latissimus dorsi EMG amplitudes were greatest during smashes (P<0.05), followed in general by attacking clearances (P<0.05) and defensive clearances (P<0.05). Drop shots induced the lowest EMG amplitudes in the shoulder girdle muscles (P<0.05). No significant main effect of the KT condition or KT-badminton stroke interaction effects were found (P>0.05). CONCLUSIONS: The use of KT conferred no immediate benefits in improving shoulder girdle muscle activity or sports performance in amateur badminton players with shoulder impingement syndrome. Shoulder girdle muscle activity and sports performance were primarily influenced by the badminton overhead stroke techniques.

Hyperglycemia Augments the Adipogenic Transdifferentiation Potential of Tenocytes and Is Alleviated by Cyclic Mechanical Stretch.

Diabetes mellitus is associated with damage to tendons, which may result from cellular dysfunction in response to a hyperglycemic environment. Tenocytes express diminished levels of tendon-associated genes under hyperglycemic conditions. In contrast, mechanical stretch enhances tenogenic differentiation. However, whether hyperglycemia increases the non-tenogenic differentiation potential of tenocytes and whether this can be mitigated by mechanical stretch remains elusive. We explored the in vitro effects of high glucose and mechanical stretch on rat primary tenocytes. Specifically, non-tenogenic gene expression, adipogenic potential, cell migration rate, filamentous actin expression, and the activation of signaling pathways were analyzed in tenocytes treated with high glucose, followed by the presence or absence of mechanical stretch. We analyzed tenocyte phenotype in vivo by immunohistochemistry using an STZ (streptozotocin)-induced long-term diabetic mouse model. High glucose-treated tenocytes expressed higher levels of the adipogenic transcription factors PPARγ and C/EBPs. PPARγ was also highly expressed in diabetic tendons. In addition, increased adipogenic differentiation and decreased cell migration induced by high glucose implicated a fibroblast-to-adipocyte phenotypic change. By applying mechanical stretch to tenocytes in high-glucose conditions, adipogenic differentiation was repressed, while cell motility was enhanced, and fibroblastic morphology and gene expression profiles were strengthened. In part, these effects resulted from a stretch-induced activation of ERK (extracellular signal-regulated kinases) and a concomitant inactivation of Akt. Our results show that mechanical stretch alleviates the augmented adipogenic transdifferentiation potential of high glucose-treated tenocytes and helps maintain their fibroblastic characteristics. The alterations induced by high glucose highlight possible pathological mechanisms for diabetic tendinopathy. Furthermore, the beneficial effects of mechanical stretch on tenocytes suggest that an appropriate physical load possesses therapeutic potential for diabetic tendinopathy.