Tendon Strain Research Articles

Functional morphology of the ankle extensor muscle-tendon units in the springhare Pedetes capensis shows convergent evolution with macropods for bipedal hopping locomotion.

This study assesses the functional morphology of the ankle extensor muscle-tendon units of the springhare Pedetes capensis, an African bipedal hopping rodent, to test for convergent evolution with the Australian bipedal hopping macropods. We dissect and measure the gastrocnemius, soleus, plantaris, and flexor digitorum longus in 10 adult springhares and compare them against similar-sized macropods using phylogenetically informed scaling analyses. We show that springhares align reasonably well with macropod predictions, being statistically indistinguishable with respect to the ankle extensor mean weighted muscle moment arm (1.63 vs. 1.65cm, respectively), total muscle mass (41.1 vs. 29.2g), total muscle physiological cross-sectional area (22.9 vs. 19.3 cm2 ), mean peak tendon stress (26.2 vs. 35.2MPa), mean tendon safety factor (4.7 vs. 3.6), and total tendon strain energy return capacity (1.81 vs. 1.82J). However, total tendon cross-sectional area is significantly larger in springhares than predicted for a similar-sized macropod (0.26 vs. 0.17 cm2 , respectively), primarily due to a greater plantaris tendon thickness (0.084 vs. 0.048 cm2 ), and secondarily because the soleus muscle-tendon unit is present in springhares but is vestigial in macropods. The overall similarities between springhares and macropods indicate that evolution has favored comparable lower hindlimb body plans for bipedal hopping locomotion in the two groups of mammals that last shared a common ancestor ~160 million years ago. The springhare's relatively thick plantaris tendon may facilitate rapid transfer of force from muscle to skeleton, enabling fast and accelerative hopping, which could help to outpace and outmaneuver predators.

Mechanical and Material Tendon Properties in Patients With Proximal Patellar Tendinopathy.

IntroductionThe effect of chronic patellar tendinopathy on tissue function and integrity is currently unclear and underinvestigated. The aim of this cohort comparison was to examine morphological, material, and mechanical properties of the patellar tendon and to extend earlier findings by measuring the ability to store and return elastic energy in symptomatic tendons.MethodsSeventeen patients with chronic (>3 months, VISA-P < 80), inferior pole patellar tendinopathy (24 ± 4 years; male = 12, female = 5) were carefully matched to controls (25 ± 3 years) for training status, pattern, and history of loading of the patellar tendon. Individual knee extension force, patellar tendon stiffness, stress, strain, Young’s modulus, hysteresis, and energy storage capacity, were obtained with combined dynamometry, ultrasonography, magnetic resonance imaging, and electromyography.ResultsAnthropometric parameters did not differ between groups. VISA-P scores ranged from 28 to 78 points, and symptoms had lasted from 10 to 120 months before testing. Tendon proximal cross-sectional area was 61% larger in the patellar tendinopathy group than in the control group. There were no differences between groups in maximal voluntary isometric knee extension torque (p = 0.216; d < −0.31) nor in tensile tendon force produced during isometric ramp contractions (p = 0.185; d < −0.34). Similarly, tendon strain (p = 0.634; d < 0.12), hysteresis (p = 0.461; d < 0.18), and strain energy storage (p = 0.656; d < 0.36) did not differ between groups. However, patellar tendon stiffness (−19%; p = 0.007; d < −0.74), stress (−27%; p< 0.002; d < −0.90) and Young’s modulus (−32%; p = 0.001; d < −0.94) were significantly lower in tendinopathic patients compared to healthy controls.DiscussionIn this study, we observed lower stiffness in affected tendons. However, despite the substantial structural and histological changes occurring with tendinopathy, the tendon capacity to store and dissipate energy did not differ significantly.

Skeletal Muscle Shape Change in Relation to Varying Force Requirements Across Locomotor Conditions.

Contractions of skeletal muscles to generate in vivo movement involve dynamic changes in contractile and elastic tissue strains that likely interact to influence the force and work of a muscle. However, studies of the in vivo dynamics of skeletal muscle and tendon strains remain largely limited to bipedal animals, and rarely cover the broad spectra of movement requirements met by muscles that operate as motors, struts, or brakes across the various gaits that animals commonly use and conditions they encounter. Using high-speed bi-planar fluoromicrometry, we analyze in vivo strains within the rat medial gastrocnemius (MG) across a range of gait and slope conditions. These conditions require changes in muscle force ranging from decline walk (low) to incline gallop (high). Measurements are made from implanted (0.5–0.8 mm) tantalum spheres marking MG mid-belly width, mid-belly thickness, as well as strains of distal fascicles, the muscle belly, and the Achilles tendon. During stance, as the muscle contracts, muscle force increases linearly with respect to gait–slope combinations, and both shortening and lengthening fiber strains increase from approximately 5 to 15% resting length. Contractile change in muscle thickness (thickness strain) decreases (r2 = 0.86; p = 0.001); whereas, the change in muscle width (width strain) increases (r2 = 0.88; p = 0.001) and tendon strain increases (r2 = 0.77; p = 0.015). Our results demonstrate force-dependency of contractile and tendinous tissue strains with compensatory changes in shape for a key locomotor muscle in the hind limb of a small quadruped. These dynamic changes are linked to the ability of a muscle to tune its force and work output as requirements change with locomotor speed and environmental conditions.

Cumulative Metrics of Tendon Load and Damage Vary Discordantly with Running Speed.

Cumulative load has become a popular metric in running biomechanics research to account for potential spatiotemporal changes associated with different locomotion strategies. This study investigated how incorporating mechanical fatigue principles into Achilles tendon cumulative load measurements affected their relationship with running speed. Achilles tendon forces and strains were estimated from a dynamometry/ultrasound session followed by a motion capture session, where participants ran at three speeds. Three cumulative measures of increasing complexity were calculated using Achilles tendon force/strain: 1) cumulative load, defined as the product of the stance phase time integral of Achilles tendon force/strain and the stride count for 1 km of running; 2) cumulative damage, which accounted for the nonlinear relationship between load magnitude and fatigue life by exponentially weighting the time integral of Achilles tendon force/strain before multiplication with stride count; and (3) the probability of fatigue failure, which expanded upon the cumulative damage measure of Achilles tendon strain by fitting a probabilistic Weibull model to existing fatigue life data to account for the inherent variability that exists in the fatigue life of biological samples. Cumulative load measures significantly decreased with running speed, whereas the cumulative damage and probabilistic measures either increased or did not change significantly with running speed. The choice of cumulative metric has an important influence on the interpretation of overuse injury risk with changes in running speed. Although cumulative load metrics certainly provide meaningful information about the load experienced over a given distance, they do not account for the tissue damage incurred by such load. Cumulative load metrics should therefore be interpreted with caution when making inferences to overuse injury risk.

Flip-flops do not alter the neuromuscular function of the gastrocnemius muscle and tendon during walking in children

Introduction/Aim: Flip-flops are a popular choice of footwear for children. However, their inherent design provides minimal support to the foot and ankle and has been suggested to increase the work performed by muscle and tendon structures, potentially predisposing them to injury. Therefore, the aim of this study was to compare the length change behaviour of the medial gastrocnemius (MG) muscle fascicles and muscle tendon unit (MTU) and their mechanical function at the ankle and subtalar joints in children during walking with and without flip-flop. Methods: Eight healthy children walked barefoot and with flip-flops whilst 3D gait analysis and simultaneous B-mode ultrasound images of the MG fascicles during level walking were collected. Joint kinematics, kinetics and MTU lengths were analysed using musculoskeletal modelling and fascicle lengths using a semi-automated tracking algorithm. Results: The muscles and tendons across the ankle absorbed greater amounts of power during barefoot walking compared to flip-flop walking. The muscle activations of the lateral gastrocnemius, soleus and tibialis anterior remained invariant across the conditions as did the activation, and fascicle length change behaviour of the medial gastrocnemius. In the barefoot condition, there was a trend of greater MTU lengthening, to potentially absorb greater amounts of power, although no differences in shortening was observed during late stance. Conclusion: Walking with flip-flops does not increase the mechanical work performed by the MG muscle at the ankle and subtalar joints, suggesting that flip-flops do not increase the stresses and strains of the Achilles tendon and hence its predisposition to strain induced injury. Instead, our results suggest that flip-flops, act as a compliant surface and absorb energy during contact and hence the strain experienced by the Achilles tendon.

Heterotopic Ossification After an Achilles Tendon Rupture Cannot Be Prevented by Early Functional Rehabilitation: A Cohort Study.

Tendon loading might play a role in the development of heterotopic ossification after Achilles tendon ruptures. Early heavy loading on a healing tendon in animals has been shown to prolong the proinflammatory response, and inflammatory cells are thought to drive heterotopic ossification formation. Taken together, this suggests that early rehabilitation might influence heterotopic ossification development. The purposes of this study were to investigate (1) whether the presence of heterotopic ossification after Achilles tendon ruptures influences clinical outcome and (2) whether early mobilization or weightbearing prevents the development of heterotopic ossification. This was a retrospective analysis of 69 patients from a previous clinical trial. All patients were treated surgically, but with three different early rehabilitation protocols after surgery: late weightbearing and ankle immobilization, late weightbearing and ankle mobilization, and early weightbearing and ankle mobilization. Plain radiographs taken 2, 6, 12, 26, and 52 weeks postoperatively were analyzed for heterotopic ossification, which was detected in 19% of patients (13 of 69) at 52 weeks. Heterotopic ossification was measured, scored, and correlated to clinical outcomes; heel-raise index (HRI), ankle joint ROM, tendon strain, Achilles tendon rupture score (ATRS), and Victorian Institute of Sport Assessment-Achilles (VISA-A) questionnaire scores at 26 and 52 weeks postoperatively. Heterotopic ossification had no adverse effects on patient-reported outcomes (ATRS or VISA-A), tendon strain, or ROM. In fact, patients with heterotopic ossification tended to have a better HRI at 52 weeks compared with patients without (mean difference 14% [95% CI -0.2 to 27]; p = 0.053). Neither the occurrence (heterotopic ossification/no heterotopic ossification) nor the heterotopic ossification severity (ossification score) differed between the three rehabilitation groups. Seventeen percent of the patients (four of 24) with early functional rehabilitation (early weightbearing and ankle joint mobilization exercise) had heterotopic ossification (score, 2-3) while late weightbearing and immobilization resulted in heterotopic ossification in 13% of the patients (score, 3-4). Heterotopic ossification occurs relatively frequently after Achilles tendon ruptures but appears to have no adverse effects on functional outcomes. Furthermore, heterotopic ossification develops during the first 6 weeks after rupture, and weightbearing or ankle-joint mobilization does not prevent this from occurring. Level III, prognostic study.

Changes on Tendon Stiffness and Clinical Outcomes in Athletes Are Associated With Patellar Tendinopathy After Eccentric Exercise.

Eccentric exercise is commonly used as a form of loading exercise for individuals with patellar tendinopathy. This study investigated the change of mechanical properties and clinical outcomes and their interrelationships after a 12-week single-legged decline-board exercise with and without extracorporeal shockwave therapy (ESWT). Randomized controlled trial. Outpatient clinic of a university. Thirty-four male in-season athletes with patellar tendinopathy for more than 3 months were randomized into exercise and combined groups. The exercise group received a 12-week single-legged decline-squat exercise, and the combined group performed an identical exercise program in addition to a weekly session of ESWT in the initial 6 weeks. Tendon stiffness and strain were examined using ultrasonography and dynamometry. Visual analog scale and Victoria Institute of Sports Assessment-patella (VISA-p) score were used to assess pain and dysfunction. These parameters were measured at preintervention and postintervention. Significant time effect but no significant group effect on the outcome measures; significant reduction in tendon stiffness (P = 0.02) and increase in tendon strain (P = 0.00); and reduction of intensity of pain (P = 0.00) and dysfunction (P = 0.00) were observed. Significant correlations between changes in tendon stiffness and VISA-p score (ρ = -0.58, P = 0.05); alteration in tendon strain, pain intensity (ρ = -0.63, P = 0.03); and VISA-p score (ρ = 0.60, P = 0.04) were detected after the exercise program. Eccentric exercise-induced modulation on tendon mechanical properties and clinical symptoms are associated in athletes with patellar tendinopathy.

Effects of rabbit pinna-derived blastema cells on tendon healing.

Objective(s):Tendon healing is substantially slow and often associated with suboptimal repair. Cell therapy is one of the promising methods to improve tendon repair. Blastema, a population of undifferentiated cells, represents characteristics of pluripotent mesenchymal stem cells and has the potentials to be used in regenerative medicine. The aim of this study was to investigate the use of blastema allotransplantation in rabbit tendon healing.Materials and Methods:In this study, one rabbit was used as a blastema donor, and twenty-four rabbits were divided into control and treatment groups. Blastema cells were obtained from ear pinna upon punch hole injury in the donor rabbit. Under general anesthesia, a complete transverse tenotomy was performed on the midsubstance of deep digital flexor tendon followed by suture-repair. In the treatment group, 1 × 106 blastema cells suspended in buffer saline were injected intratendinously at the repair site, while the control group received only the buffer saline. Cast coaptation was maintained for two weeks. Eight weeks after the operation, tendons were harvested, and histopathological, biomechanical, and biochemical assays were performed on samples. Results:Mechanical testing showed a significant increase in ultimate load, energy absorption, stiffness, yield load, stress, and strain in blastema-treated tendons compared to controls. Also, higher hydroxyproline content and improved collagen alignment along with lower inflammatory cell infiltration and decreased angiogenesis were observed in blastema-treated tendons. Conclusion:Increased levels of hydroxyproline and improved histopathological and biomechanical parameters in the treatment group suggest that blastema cells could be considered an adjunct to tendon repair in rabbits.

Surgical Release of the Adductor Longus With or Without Sports Hernia Repair Is a Useful Treatment for Recalcitrant Groin Strains in the Elite Athlete.

Background:Chronic strain and/or tendinopathy of the adductor longus tendon can be a cause of long-standing groin pain in the elite athlete, resulting in significant time lost from competition. Accurate diagnosis and treatment can expedite return to play.Purpose/Hypothesis:To evaluate return to sport and performance in National Collegiate Athletic Association (NCAA) Division I football players and National Football League (NFL) players following adductor longus release with or without sports hernia repair. We hypothesized that adductor release will be an effective method of treatment for recalcitrant groin/adductor pain in these athletes.Study Design:Case series; Level of evidence, 4.Methods:A cohort study was performed of all NFL players and NCAA Division I college athletes who had undergone an adductor longus tendon release with or without sports hernia repair by 1 of 2 fellowship-trained orthopaedic surgeons between May 1999 and January 2013. All patients reported groin pain below the inguinal ligament and localized to their adductor longus. Symptoms lasted longer than 10 weeks and limited their ability to effectively perform during sport, as assessed by their coach and self-assessment. Questionnaires were given to all 26 patients to assess long-term surgical outcomes. A subgroup analysis was performed for NFL players, in which “performance scores” were calculated according to individual player statistics while playing. Scores obtained before the diagnosis of chronic adductor longus tendinopathy or strain were compared with those after surgery. Patients with prior abdominal or pelvic surgery, radiographic evidence of degenerative joint disease of the hip, labral tears or femoral acetabular impingement, prostatic or urinary tract disease, or nerve entrapment of the ilioinguinal, genitofemoral, or lateral femoral cutaneous nerves were excluded from the study.Results:A total of 32 athletes underwent an adductor longus tenotomy during the study period. Of these patients, 28 were college- or professional-level athletes who underwent an adductor longus tenotomy, with a mean ± SD follow-up time of 6.2 ± 4.2 years (range, 12-178 months). Of the 32 patients, 20 had a concomitant sports hernia repair in addition to an adductor longus tenotomy. Thirty-one patients (97%) were able to return to their previous sport, and 30 (94%) were able to return at their previous level of play. Thirty patients (94%) reported that they were satisfied with their decision to have surgery. No player complained of weakness or a decrease in running speed or power. Mean return to play was 12 weeks from date of surgery. In the subgroup analysis of 16 NFL players, there were no statistically significant differences for the pre- versus postoperative comparisons of the athlete performance scores (P = .74) and the percentage of the games started versus played (P = .46). After separation of players who had a concomitant hernia repair from players who did not, there was no statistically significant difference in performance scores or percentages of games started.Conclusion:In this study of elite athletes, adductor longus tenotomy with or without a concomitant sports hernia repair provided overall acceptable and excellent results. Athletes were able to return to their previous level of athletic competition and performance with consistent relief of groin pain. Return to play in an NFL game averaged 12 weeks following surgery.

Evaluation of Sonoelastography Compatibility on the Achilles Tendon Between Different Devices and Observers

Aim: To investigate the reliability of sonoelastography by comparing the Achilles tendon strain ratio obtained in healthy volunteers by different observers with different sonoelastography devices working on the same principle.Material and Methods: A total of 80 Achilles tendons in 40 volunteers without chronic disease were evaluated using Toshiba and Hitachi devices using real-time elastography principle. The Kager fat pad was selected for strain ratio measurement. Each tendon was evaluated with both devices twice by both observers. The intraobserver and interobserver agreement were examined by intraclass correlation coefficient (ICC) obtained by two-way mixed ANOVA model for absolute agreement and interpreted as Ko and Li (11) suggested.Results: Interobserver agreement in the first and second measurements of the Hitachi device and in the second measurements of the Toshiba device was found to be good (average ICC&amp;gt;0.75). The interobserver agreement in the first measurements made on the Toshiba device was found to be lower (average ICC=0.729, p&amp;lt;0.001). The intraobserver agreement was found to be excellent (ICC&amp;gt;0.90) for both device. The interobserver agreement for the Toshiba device was found lower than for the Hitachi device. Mean strain ratio was 2.96±1.07 for the Hitachi device and 3.54±1.03 for the Toshiba device. Measurements obtained from the Toshiba device were determined as significantly higher than those from the Hitachi device.Conclusion: There may be differences in strain rates depending on the compression application limits of the devices, in studies carried out using different devices. Therefore, intraobserver and interobserver agreement should be evaluated separately for each device.

Hip and Groin Pain in Soccer Players.

Purpose The aim of this article is to illustrate the recent framework necessary to standardize studies on groin pain and review the existing literature on groin pain in football. Methods The common pathological processes underlying groin pain such as muscle, tendon or ligament strain, bone injury or fracture, sport hernia, bursitis, osteitis pubis, and hip-related diseases have been reviewed and current management options have been considered. Results Groin pain is considered a pain in pubic or lower abdominal or adductors region which can be monolateral or bilateral. It is common in high-intensity team sports and can negatively affect an athlete's professional carrier, causing serious disruption in the performance. Despite a high prevalence of groin pain in athletes, diagnosis and management of the underlying pathological processes remain a challenge for surgeons, radiologists, and physiotherapists alike. Conclusion A multidisciplinary approach is essential for patients with groin pain allowing prompt diagnosis and initiation of treatment thus facilitating more rapid return to play and preventing potential long-term sequelae of chronic groin pathology.

The effects of both jump/land phases and direction on Achilles tendon loading.

Athletes in jumping and running sports have a high incidence of Achilles tendon (AT) injuries. We compared AT loading during jumping and landing phases in anteroposterior (AP) and mediolateral (ML) directions. Sixteen males (age: 21.6±1.8 years, height: 178.4±6.4 cm, weight: 76.4±11.2 kg) performed single leg AP and ML jump-landings during both propulsive (jump) and braking (land) phases. Inverse dynamics and static optimization were used to determine muscle forces. AT cross sectional area was measured with ultrasound. AT force was divided by cross sectional area to determine stress while strain was determined from previous data. Two-way repeated measures analysis of variance (α=0.05) compared several variables (vertical ground reaction force (VGRF), ankle and knee angle, ankle joint muscle moment arm, external ankle moment arm, AT tendon force, stress, and strain) between movements (jump-landings) and directions (AP/ML). AT loading was higher during jump than land in the ML compared to AP direction. VGRF was higher during land versus jump with no direction effect (AP/ML). An interaction showed a higher VGRF during the AP land and ML jump. The ankle joint moment arm was lower in jump and AP direction at peak tendon stress. External ankle moment arm at peak tendon stress was higher in jump and ML direction with an interaction. A larger external ankle moment arm occurred in ML but the change was less in the jump. Higher tendon loading occurred during the jump and ML direction. This may provide insight into both injuries and rehabilitation efforts.

Patellar Tendon Strain Associates to Tendon Structural Abnormalities in Adolescent Athletes.

High mechanical strain is thought to be one of the main factors for the risk of tendon injury, as it determines the mechanical demand placed upon the tendon by the working muscle. The present study investigates the association of tendon mechanical properties including force, stress and strain, and measures of tendon micromorphology and neovascularization, which are thought to be indicative of tendinopathy in an adolescent high-risk group for overuse injury. In 16 adolescent elite basketball athletes (14–15 years of age) we determined the mechanical properties of the patellar tendon by combining inverse dynamics with magnetic resonance and ultrasound imaging. Tendon micromorphology was determined based on a spatial frequency analysis of sagittal plane ultrasound images and neovascularization was quantified as color Doppler area. There was a significant inverse relationship between tendon strain and peak spatial frequency (PSF) in the proximal tendon region (r = −0.652, p = 0.006), indicating locally disorganized collagen fascicles in tendons that are subjected to high strain. No such associations were present at the distal tendon site and no significant correlations were observed between tendon force or stress and tendon PSF as well as between tendon loading and vascularity. Our results suggest that high levels of tendon strain might associate to a micromorphological deterioration of the collagenous network in the proximal patellar tendon, which is also the most frequent site affected by tendinopathy. Neovascularization of the tendon on the other hand seems not to be directly related to the magnitude of tendon loading and might be a physiological response to a high frequency of training in this group. Those findings have important implications for our understanding of the etiology of tendinopathy and for the development of diagnostical tools for the assessment of injury risk.

Interfascicular matrix-mediated transverse deformation and sliding of discontinuous tendon subcomponents control the viscoelasticity and failure of tendons

In the present article, we investigated the sliding of discontinuous tendon subcomponents and the variation of nonhomogeneous deformation in the human Achilles tendon (AT) over time using uniaxial tensile and relaxation tests. The deformation and the resulting strain distribution under uniaxial tension are examined using a vision-based 3-D digital image correlation (DIC) system, which allows estimation of the strain field in the axial and lateral directions. Relaxation test under B-mode ultrasound imaging with the use of DIC method provides information about the local strain variation over time in the axial and anteroposterior directions. The observed nonhomogeneous deformation, a result from the twisted structure of the tendon, shows both compressive and tensile transverse strains that can generate interfascicular matrix (IFM) failure and initiate water accumulation in the course of tendinopathy. Moreover, using B-mode elastography with the DIC method, we have observed areas of low stiffness when the strain values exceed the strength limits, and this could correspond to IFM carrying the load between discontinuous tendon subcomponents. Thus, IFM carrying complex multiscale stresses may be responsible for the strength and viscoelastic properties of the AT. The results presented here reveal a new pathomechanism of AT failure. This could be useful in further studies on tendinopathy as well as effective planning of the AT therapy.

Overexpression of mechanical sensitive miR-337-3p alleviates ectopic ossification in rat tendinopathy model via targeting IRS1 and Nox4 of tendon-derived stem cells.

Tendinopathy, which is characterized by the ectopic ossification of tendon, is a common disease occurring in certain population, such as athletes that suffer from repetitive tendon strains. However, the molecular mechanism underlying the pathogenesis of tendinopathy caused by the overuse of tendon is still lacking. Here, we found that the mechanosensitive miRNA, miR-337-3p, had lower expression under uniaxial cyclical mechanical loading in tendon-derived stem cells (TDSCs) and negatively controlled chondro-osteogenic differentiation of TDSCs. Importantly, downregulation of miR-337-3p expression was also observed in both rat and human calcified tendons, and overexpressing miR-337-3p in patellar tendons of rat tendinopathy model displayed a robust therapeutic efficiency. Mechanistically, we found that the proinflammatory cytokine interleukin-1β was the upstream factor of miR-337-3p that bridges the mechanical loading with its downregulation. Furthermore, the target genes of miR-337-3p, NADPH oxidase 4, and insulin receptor substrate 1, activated chondro-osteogenic differentiation of TDSCs through JNK and ERK signaling, respectively. Thus, these findings not only provide novel insight into the molecular mechanisms underlying ectopic ossification in tendinopathy but also highlight the significance of miR-337-3p as a putative therapeutic target for clinic treatment of tendinopathy.

Training-induced increase in Achilles tendon stiffness affects tendon strain pattern during running.

BackgroundDuring the stance phase of running, the elasticity of the Achilles tendon enables the utilisation of elastic energy and allows beneficial contractile conditions for the triceps surae muscles. However, the effect of changes in tendon mechanical properties induced by chronic loading is still poorly understood. We tested the hypothesis that a training-induced increase in Achilles tendon stiffness would result in reduced tendon strain during the stance phase of running, which would reduce fascicle strains in the triceps surae muscles, particularly in the mono-articular soleus.MethodsEleven subjects were assigned to a training group performing isometric single-leg plantarflexion contractions three times per week for ten weeks, and another ten subjects formed a control group. Before and after the training period, Achilles tendon stiffness was estimated, and muscle-tendon mechanics were assessed during running at preferred speed using ultrasonography, kinematics and kinetics.ResultsAchilles tendon stiffness increased by 18% (P < 0.01) in the training group, but the associated reduction in strain seen during isometric contractions was not statistically significant. Tendon elongation during the stance phase of running was similar after training, but tendon recoil was reduced by 30% (P < 0.01), while estimated tendon force remained unchanged. Neither gastrocnemius medialis nor soleus fascicle shortening during stance was affected by training.DiscussionThese results show that a training-induced increase in Achilles tendon stiffness altered tendon behaviour during running. Despite training-induced changes in tendon mechanical properties and recoil behaviour, the data suggest that fascicle shortening patterns were preserved for the running speed that we examined. The asymmetrical changes in tendon strain patterns supports the notion that simple in-series models do not fully explain the mechanical output of the muscle-tendon unit during a complex task like running.

Effect of Shoe and Surface Stiffness on Lower Limb Tendon Strain in Jumping.

Tendinopathies are painful overuse injuries observed in athletes participating in jumping sports. These injuries are heavily dependent on the resulting strain from the applied mechanical load. Therefore, mechanisms to reduce tendon strain may represent a primary prevention strategy to reduce the incidence of tendinopathy. The purpose of this study was to examine the effect of shoe and surface stiffness on Achilles and patellar tendon strains during jumping. We hypothesized that less stiff shoes and surfaces would reduce Achilles and patellar tendon strains during jumping. Thirty healthy male basketball players performed countermovement jumps in three shoes and on three surfaces with different stiffness properties while motion capture, force platform, and jump height data were collected. Magnetic resonance imaging was used to obtain participant-specific tendon morphology, and a combined dynamometry/ultrasound/electromyography session was used to obtain tendon material properties. Finally, a musculoskeletal model was used to estimate tendon strains in each surface and shoe combination. Achilles tendon strains during landing were reduced by 5.3% in the least stiff shoe compared with the stiffest shoe (P = 0.021) likely due to in bending stiffness altering the center of pressure location. Furthermore, Achilles tendon strains during landing were 5.7% and 8.1% lower on the stiffest surface compared with the least stiff and middle stiffness surfaces, respectively (P ≤ 0.047), because of changes in ground reaction force magnitude and center of pressure location. No effects of shoe stiffness or surface construction were observed for jump height (P > 0.243) or peak patellar tendon strains (P > 0.259). Changes to shoe stiffness and surface construction can alter Achilles tendon strains without affecting jump performance in athletes.

Impaired mechanical properties of Achilles tendon in spastic stroke survivors: an observational study

ABSTRACTBackground: The spasticity could lead to decreased functional capacity and changes in musculoskeletal tissue.Objective: To compare the Achilles tendon properties between the affected and contralateral limbs of participants with spasticity due to stroke and the healthy subjects.Methods: Fifteen individuals with ankle spasticity due to stroke and 15 healthy subjects were recruited. Maximal isometric ankle joint torque was obtained with an isokinetic dynamometer, and an ultrasound was used to determine tendon length, tendon cross-sectional area, and the medial gastrocnemius myotendinous junction displacement. The Achilles tendon strength, displacement, stress, strain, stiffness, and Young’s modulus were obtained during a maximum voluntary isometric plantarflexion contraction.Results: There were no differences between Achilles tendon length among participants. Both limbs of participants with stroke showed reduced tendon cross-sectional area (~18%) compared to healthy limb. The affected limb showed decreased tendon strength (686 ± 293.3 N), displacement (10.6 ± 1.7 mm), Young’s modulus values (849 ± 235.6 MPa), and lower stiffness (196.6 ± 67.6 N/mm) compared to the contralateral limb (strength, 1357.1 ± 294.8 N; displacement, 15.2 ± 5.5 mm; Young’s modulus, 1431.8 ± 301.9 MPa; stiffness, 337.5 ± 98.1 N/mm) and to the healthy limb. The contralateral limb also showed decreased tendon strength (~26.2%) and stiffness (~21.5%) compared to the healthy group.Conclusion: There is a decrement in Achilles tendon morphological and mechanical properties of the affected limb in individuals with spasticity due to stroke. The contralateral limb had a thinner tendon more compliant likely to physical activity reduction.

MAPPING COMPRESSIVE AND TENSILE STRAINS OF THE PATELLAR TENDON IN OSGOOD-SCHLATTER DISEASE USING ULTRASOUND ELASTOGRAPHY

Background Osgood-Schlatter Disease (OSD) impacts millions of young athletes every year, yet its biomechanical etiology remains unclear. It’s been postulated that increased growth velocity in children elevates tension within the patellar tendon, placing distal strain on the tibial tubercle, causing anterior knee pain, but this process has not been previously elucidated. The purpose of this study was to evaluate axial tensile and transverse compressive strains in adolescent patellar tendons during exercise to identify differences between those with and without OSD using a cumulative strain, ultrasound elastography measurement method [REF: Chimenti et al 2016]. Methods Axial tensile and transverse compressive strains of the patellar tendon in eight adolescents with OSD and ten adolescents without OSD were quantified from ultrasound elastography images. Multiaxial strains of the patellar tendon were assessed as the participant performed two different exercises: 1) participant seated with leg fully extended, participant bends knee, followed by a return to initial extended position; (2) participant standing performs a squat and then returns to initial standing position. Participants’ disease severity was clinically assessed using the VISA-P and Cincinnati knee scale. Results Mean age was 13.1 years (+/- 2.7), 39% were male (63% of OSD group). There was no statistically significant difference in patellar tendon tensile strains during the seated knee flexion and squat positions between groups (p = 0.99, p = 0.83 respectively). The OSD group had significantly less tendon compression compared to the non-OSD group during both the knee flexion (p &lt;0.01), and squat exercises (p &lt;0.05). Conclusions/Significance Adolescents with OSD had lower transverse compressive strains in the patellar tendon as compared to adolescents without OSD. In contrast, tensile strains were not increased in children with OSD. These findings appear to contradict the tension hypothesis postulating that OSD is caused by increased patellar tendon axial tension associated with rapid bone growth, Instead, impingement from the tibia leading to transverse tendon compression may lead to an adaptive stiffing the patellar tendon, However, further research is needed to confirm this hypothesis. While OSD is a common cause of knee pain in growing athletes that frequently leads to loss in participation, its etiology is unclear, making development of effective treatment approaches difficult. This study highlights differences in multiaxial patellar tendon strains in adolescents with OSD which may help direct future research on management strategies.

Usability of Achilles tendon strain elastography for the diagnosis of coronary artery disease.

There are close relationships between major coronary artery disease (CAD) risk factors and Achilles tendon thickness (AT-T) and AT strain ratio (AT-SR). Our aim was to evaluate the diagnostic importance of AT-T and AT-SR as obtained by ultrasonography (USG) and strain elastography (SE) for predicting CAD. One hundred and eighty-four patients scheduled to undergo coronary angiography were included in the study. Achilles tendon USG (B-mode and SE) and laboratory tests were performed on all patients. The patients were divided into two groups, i.e., patients with and without CAD. The patients with CAD (72.8%) were more likely to be male, exhibited higher frequencies of diabetes mellitus (DM) and hyperlipidemia, exhibited higher levels of basal creatinine and glucose, and had higher AT-T and AT-SR values (p < 0.05 for all). Age, DM, AT-T, and AT-SR independently predicted the probability of CAD in a logistic regression analysis (p < 0.05 for all). Age (each year), DM (presence), AT-T (each 1mm), and AT-SR (each 0.1) increased the CAD risk by 3.4%, 2.9 times, 47.1%, and 16.0%, respectively. ROC analysis revealed AUCs of 0.665 and 0.730 for the AT-T and AT-SR values, respectively (p < 0.05). The AT-SR cutoff value of 1.2 predicted the presence of CAD with 75.4% sensitivity and 72.7% specificity. AT-SR is a simple, inexpensive, noninvasive, reproducible, and objective parameter for the prediction of CAD. We think that AT-SR evaluation should become a part of conventional USG assessments in patients who are at a high risk of CAD.