Reduced Achilles Tendon Stiffness Disrupts Calf Muscle Neuromechanics in Elderly Gait.
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ABSTRACT:
SUBMITTER: Krupenevich RL
PROVIDER: S-EPMC8761229 | biostudies-literature | 2022
REPOSITORIES: biostudies-literature
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Reduced Achilles Tendon Stiffness Disrupts Calf Muscle Neuromechanics in Elderly Gait.
Krupenevich Rebecca L RL Beck Owen N ON Sawicki Gregory S GS Franz Jason R JR
Gerontology 20210716 3
Older adults walk slower and with a higher metabolic energy expenditure than younger adults. In this review, we explore the hypothesis that age-related declines in Achilles tendon stiffness increase the metabolic cost of walking due to less economical calf muscle contractions and increased proximal joint work. This viewpoint may motivate interventions to restore ankle muscle-tendon stiffness, improve walking mechanics, and reduce metabolic cost in older adults. ...[more]
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Project description:During rapid deceleration of the body, tendons buffer part of the elongation of the muscle-tendon unit (MTU), enabling safe energy dissipation via eccentric muscle contraction. Yet, the influence of changes in tendon stiffness within the physiological range upon these lengthening contractions is unknown. This study aimed to examine the effect of training-induced stiffening of the Achilles tendon on triceps surae muscle-tendon behavior during a landing task. Twenty-one male subjects were assigned to either a 10-week resistance-training program consisting of single-leg isometric plantarflexion (n = 11) or to a non-training control group (n = 10). Before and after the training period, plantarflexion force, peak Achilles tendon strain and stiffness were measured during isometric contractions, using a combination of dynamometry, ultrasound and kinematics data. Additionally, testing included a step-landing task, during which joint mechanics and lengths of gastrocnemius and soleus fascicles, Achilles tendon, and MTU were determined using synchronized ultrasound, kinematics and kinetics data collection. After training, plantarflexion strength and Achilles tendon stiffness increased (15 and 18%, respectively), and tendon strain during landing remained similar. Likewise, lengthening and negative work produced by the gastrocnemius MTU did not change detectably. However, in the training group, gastrocnemius fascicle length was offset (8%) to a longer length at touch down and, surprisingly, fascicle lengthening and velocity were reduced by 27 and 21%, respectively. These changes were not observed for soleus fascicles when accounting for variation in task execution between tests. These results indicate that a training-induced increase in tendon stiffness does not noticeably affect the buffering action of the tendon when the MTU is rapidly stretched. Reductions in gastrocnemius fascicle lengthening and lengthening velocity during landing occurred independently from tendon strain. Future studies are required to provide insight into the mechanisms underpinning these observations and their influence on energy dissipation.
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Project description:ObjectivesThe objective of the current cross-sectional study was to examine Achilles tendon transverse stiffness in a group of recreational runners with Achilles tendinopathy, in comparison to an asymptomatic group of runners with similar training history. We also aimed to determine the between-week intra-individual reliability of this measurement technique.DesignCross-sectional cohort study.MethodsA hand-held dynamometer was used to assess the transverse stiffness of the Achilles tendon (AT) in twenty-five recreational runners. In ten people with midportion Achilles tendinopathy (5 men, 5 women), measurements were taken directly over the most symptomatic location. In 15 people who were free of AT symptoms (7 men, 8 women), measurements were taken at an equivalent location on the tendon. Participants returned after one week to determine measurement reliability (intra-class correlation coefficient/ICC and minimum detectable change/MDC95). We also collected information about people's tendon loading activities, tendon thickness (ultrasound mesaurement), and symptoms (Victorian Institute of Sports Assessment-Achilles / VISA-A score).ResultsThe AT transverse stiffness was lower in people with Achilles tendinopathy (777 N/m ± 86) compared to those who were asymptomatic (873 N/m ± 72) (p < 0.05). AT transverse stiffness was negatively correlated with age and tendon thickness, and positively correlated with VISA-A score and waist circumference. Reliability was good, with ICC of 0.81 in people with tendinopathy and 0.80 in healthy controls, and an MDC95 of 118 and 87N/m in these two respective groups.ConclusionsTransverse Achilles tendon stiffness can be reliably measured in people with midportion Achilles tendinopathy, and appears to be lower in people who are older, more symptomatic, and with more extensive tendon thickening. The potential clinical utility of monitoring tendon stiffness in the management of tendon injuries merits further study.
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Project description:Biomechanical deviations at individual joints are often identified by gait analysis of patients with cerebral palsy (CP). Analysis of the control of joint and leg stiffness of the locomotor system during gait in children with spastic diplegic CP has been used to reveal their control strategy, but the differences between before and after surgery remain unknown. The current study aimed to bridge the gap by comparing the leg stiffness-both skeletal and muscular components-and associated joint stiffness during gait in 12 healthy controls and 12 children with spastic diplegic CP before and after tendon release surgery (TRS). Each subject walked at a self-selected pace on a 10-meter walkway while their kinematic and forceplate data were measured to calculate the stiffness-related variables during loading response, mid-stance, terminal stance, and pre-swing. The CP group altered the stiffness of the lower limb joints and decreased the demand on the muscular components while maintaining an unaltered leg stiffness during stance phase after the TRS. The TRS surgery improved the joint and leg stiffness control during gait, although residual deficits and associated deviations still remained. It is suggested that the stiffness-related variables be included in future clinical gait analysis for a more complete assessment of gait in children with CP.
| S-EPMC7810324 | biostudies-literature
Project description: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.
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Project description:It is believed that hormonal changes during pregnancy lead to an increased compliance in ligaments and tendons, increasing the risk to suffer from connective tissue injuries particularly during exercise. While the laxity of the pelvic ligaments may increase to facilitate childbirth, to our knowledge no study has ever investigated the mechanical properties of human tendons in different stages of pregnancy. Thus, the purpose of our longitudinal study was to investigate the mechanical properties of the patellar tendon in different stages of pregnancy and postpartum. Nineteen pregnant women (30 ± 4 years) and 11 non-pregnant controls (28 ± 3 years) performed maximum isometric knee extension contractions on a dynamometer. Muscle strength and mechanical properties of the patellar tendon were determined integrating ultrasound, kinematic, and electromyographic measurements. In pregnant women, measurements were performed in the 16 ± 4th week of pregnancy (EP), the 29 ± 4th week of pregnancy (LP) and 32 ± 9th weeks postpartum (PP). On average, muscle strength as well as patellar tendon stiffness, force, and relative strain did not change during pregnancy and did not differ from non-pregnant controls. Tendon length measured at 90° knee flexion continuously increased during and after pregnancy (tendon length PP>EP; PP>controls). Our results indicate that patellar tendon stiffness is not universally affected by pregnancy. We found no evidence to support the often stated assumption that tendons would become more compliant during pregnancy. However, variability between individuals as well as the progressive increase in tendon rest length during and after pregnancy and its implications on injury risk need to be further examined.
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Project description:Incomplete tendon healing and postponed muscle weakness after Achilles tendon rupture and surgical repair lead to poor performance in patient activities. Although the effectiveness of postoperative early functional rehabilitation has been proven, the priority and each effect of specific methods in early rehabilitation remain unclear. We hypothesized early muscle contraction exercises without joint motion would promote tendon healing and prevent calf muscle atrophy; in contrast, early static stretching after surgical repair would not contribute to tendon healing and induce calf muscle atrophy. C57Bl/6 mice underwent Achilles tendon rupture and suture repair, followed by different methods of post-surgery interventions: a non-exercise group, a Static stretching group, and an Electrical muscle stimulation group. 3 and 5 weeks after surgery, we assessed ex vivo tendon mechanical properties, collagen fiber alignment, and histological muscle properties. Electrical Muscle Stimulation restored the recovery of tendon mechanical properties and muscle strength more quickly than Static stretching. Static stretching had no additional effect on them compared to the non-exercise. Our results suggested that calf muscle contraction was essential as a post-surgery early functional rehabilitation to load tensile forces on tendons and improve Achilles tendon healing. Additionally, early muscle contractions naturally promote restoring muscle function after the rupture, but further research is needed to optimize muscle contraction protocols.
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