Biomedical subjects

Kiros Karamanidis

Publications and source records attributed to Kiros Karamanidis.

15 recordsLinked to original sources

PubMed2006

Mechanical properties of the triceps surae tendon and aponeurosis in relation to intensity of sport activity.

The purpose of the present study was to investigate whether the mechanical properties (i.e. force strain relationship) of the triceps surae tendon and aponeurosis relate to the performed sport activity in an intensity-dependent manner. This was done by comparing sprinters with endurance runners and subjects not active in sports. Sixty-six young male subjects (26+/-5 yr; 183+/-6 cm; 77.6+/-6.7 kg) participated in the study. Ten of these subjects were adults not active in sports, 28 were endurance runners and 28 sprinters. All subjects performed isometric maximal voluntary plantar flexion contractions (MVC) on a dynamometer. The distal aponeuroses of the gastrocnemius medialis (GM) was visualised by ultrasound during the MVC. The results showed that only the sprinters had higher normalised stiffness (relationship between tendon force and tendon strain) of the triceps surae tendon and aponeurosis and maximal calculated tendon forces than the endurance runners and the subjects not active in sports. Furthermore, including the data of all 66 examined participants tendon stiffness correlated significantly (r=0.817, P<0.001) with the maximal tendon force achieved during the MVC. It has been concluded that the mechanical properties of the triceps surae tendon and aponeurosis do not show a graded response to the intensity of the performed sport activity but rather remain at control level in a wide range of applied strains and that strain amplitude and/or frequency should exceed a given threshold in order to trigger additional adaptation effects. The results further indicate that subjects with higher muscle strength possibly increase the margin of tolerated mechanical loading of the tendon due to the greater stiffness of their triceps surae tendon and aponeurosis.

Adaptation, Physiological↗

PubMed2006

Age-related degeneration in leg-extensor muscle-tendon units decreases recovery performance after a forward fall: compensation with running experience.

The goals of this study were to investigate whether the lower muscle-tendon units (MTUs) capacities in older affect their ability to recover balance with a single-step after a fall, and to examine whether running experience enhances and protects this motor skill in young and old adults. The investigation was conducted on 30 older and 19 younger divided into two subgroups: runners versus non-active. In previous studies we documented that the older had lower leg extensor muscle strength and tendon stiffness while running had no effect on MTUs capacities. The current study examined recovery mechanics of the same individuals after an induced forward fall. Younger were better able to recover balance with a single-step compared to older (P < 0.001); this ability was associated with a more effective body configuration at touchdown (more posterior COM position relative to the recovery foot, P <0.001). MTUs capacities classified 88.6% of the subjects into single- or multiple-steppers. Runners showed a superior ability to recover balance with a single-step (P < 0.001) compared to non-active subjects due to a more effective mechanical response during the stance phase (greater knee joint flexion, P <0.05). We concluded that the age-related degeneration of the MTUs significantly diminished the older adults' ability to restore balance with a single-step. Running seems to enhance and protect this motor skill. We suggested that runners, due to their running experience, could update the internal representation of mechanisms responsible for the control of dynamic stability during a forward fall and, thus, were able to restore balance more often with a single-step compared to the non-active subjects.

Accidental Falls↗

PubMed2006

Aging and running experience affects the gearing in the musculoskeletal system of the lower extremities while walking.

The aims of this study were to investigate whether older adults modify their walking mechanics to compensate for the degeneration in their muscle-tendon units (MTUs), and to examine whether running has a beneficial effect on walking mechanics in younger and older adults. The investigation was conducted on 30 older and 19 younger adults divided into two subgroups: runners versus non-active. In previous studies we documented that older adults had lower leg-extensor muscle strength and tendon stiffness compared to younger. Runners and non-active subjects had similar MTU capacities. In this study we analysed walking kinematics and kinetics (1.6 m/s) from the same subjects. Older adults showed a lower gear ratio (ratio between moment arm of the ground reaction force and moment arm of muscle) at the triceps surae MTU during the initial and mid part of ground contact, lower average horizontal forces and lower average ankle joint moment during ground contact compared to younger (p<0.05). Compared to non-active subjects, runners had a lower gear ratio at the quadriceps femoris MTU during the initial and final part of ground contact, lower average horizontal forces and lower maximal knee joint moment during ground contact independent of the subject's age (p<0.05). We concluded that the older adults modify the gearing at the ankle joint in order to adjust the task effort to the reduced triceps surae muscle strength. It appears, further, that runners walked more effectively from a mechanical standpoint compared to non-active subjects, which suggests that runners may be able to transfer motor adaptation from running to walking even in old age.

Adaptation, Physiological↗

PubMed2006

Adaptational phenomena and mechanical responses during running: effect of surface, aging and task experience.

The goals of the study were to identify adaptational phenomena in running mechanics over a variety of surfaces due to age related changes in the muscle-tendon units (MTUs) capacities, to examine whether running experience is associated with adaptational effects on running mechanics over a variety of surfaces even at old age, and to investigate whether surface condition affects running mechanics. The investigation was executed on 30 old and 19 young including 29 runners and 20 non-active subjects. In a previous study we documented that the older had lower MTUs capacities. In the present study running mechanics were analysed as the same subjects ran at 2.7 m/s over three surfaces having different compliance. Surface condition did not affect centre of mass trajectory, duty factor or joint kinetics (P > 0.01). Older react to the reduced MTUs capacity by increasing duty factor and benefiting from a mechanical advantage for the triceps surae MTU and a lower rate of force generation on all surfaces (P < 0.01). Runners displayed lower average horizontal forces and a higher mechanical advantage for the quadriceps femoris MTU for all surfaces (P < 0.01). The results provided strong evidence on that running strategy remained essentially unchanged over a variety of surfaces. Adaptive improvements in running mechanics due to task experience were present for all surfaces and did not depend on age. We further concluded that older adults were able to recalibrate their running strategy to adjust the task effort to the reduced MTUs capacities in a feedforward control manner for a variety of mechanical environments.

Adaptation, Physiological↗

PubMed2006

Mechanical and morphological properties of human quadriceps femoris and triceps surae muscle-tendon unit in relation to aging and running.

The purpose of this study was to examine the effects of aging and endurance running on the mechanical and morphological properties of different muscle-tendon units (MTUs) in vivo. The investigation was conducted on 30 elderly and 19 young adult males. For the analysis of possible MTU adaptation in response to endurance running the subjects were divided into two subgroups: non-active vs. endurance-runners. All subjects performed isometric maximal voluntary plantarflexion and knee extension contractions on a dynamometer. The distal aponeurosis of the gastrocnemius medialis (GM) and vastus lateralis (VL) during plantarflexion and knee extensions and the muscle architecture of the GM and VL were visualized by ultrasonography. The maximal knee and ankle joint moment were higher for the young compared to the elderly population (p<0.05). No identifiable differences in muscle architecture between young and elderly subjects were detected in VL and GM. Aging results in a reduced (p<0.05) normalized stiffness of the quadriceps femoris tendon and aponeurosis, which were not identifiable for the triceps surae. In contrast, the properties of both MTUs showed no major differences between endurance-runners and the non-active group (p>0.05). Only pennation angle at the GM were higher for the runners compared to the non-active group (p<0.05). The present results indicate that tendon changes related to aging do not occur proportionally in different MTUs. Furthermore, it seems that the extra stress and load imposed on high-load-bearing MTUs during endurance running may not be sufficient to produce significant adaptative processes in the mechanical parameters analyzed.

Adult↗

PubMed2006

Influence of the muscle-tendon unit's mechanical and morphological properties on running economy.

The purpose of this study was to test the hypothesis that runners having different running economies show differences in the mechanical and morphological properties of their muscle-tendon units (MTU) in the lower extremities. Twenty eight long-distance runners (body mass: 76.8+/-6.7 kg, height: 182+/-6 cm, age: 28.1+/-4.5 years) participated in the study. The subjects ran on a treadmill at three velocities (3.0, 3.5 and 4.0 m s(-1)) for 15 min each. The V(O(2)) consumption was measured by spirometry. At all three examined velocities the kinematics of the left leg were captured whilst running on the treadmill using a high-speed digital video camera operating at 250 Hz. Furthermore the runners performed isometric maximal voluntary plantarflexion and knee extension contractions at eleven different MTU lengths with their left leg on a dynamometer. The distal aponeuroses of the gastrocnemius medialis (GM) and vastus lateralis (VL) were visualised by ultrasound during plantarflexion and knee extension, respectively. The morphological properties of the GM and VL (fascicle length, angle of pennation, and thickness) were determined at three different lengths for each MTU. A cluster analysis was used to classify the subjects into three groups according to their V(O(2)) consumption at all three velocities (high running economy, N=10; moderate running economy, N=12; low running economy, N=6). Neither the kinematic parameters nor the morphological properties of the GM and VL showed significant differences between groups. The most economical runners showed a higher contractile strength and a higher normalised tendon stiffness (relationship between tendon force and tendon strain) in the triceps surae MTU and a higher compliance of the quadriceps tendon and aponeurosis at low level tendon forces. It is suggested that at low level forces the more compliant quadriceps tendon and aponeurosis will increase the force potential of the muscle while running and therefore the volume of active muscle at a given force generation will decrease.

Adult↗

PubMed2005

In vivo motion transmission in the inactive gastrocnemius medialis muscle-tendon unit during ankle and knee joint rotation.

The purposes of this study were: (a) to quantify the influence of passive ankle and knee joint angular displacement on the estimated mechanical and architectural properties of the gastrocnemius medialis (GM) muscle-tendon unit, and (b) to determine the strain distribution of separate structures (tendon, aponeurosis and fascicle) during passive lengthening of the GM muscle-tendon unit at rest. Ten male subjects participated in the study. The passive ankle and knee joint movements were performed on an isokinetic dynamometer. The kinematics of the left leg were recorded using the Vicon 624 system with 8 cameras. Two ultrasound probes were used to examine the elongation of the tendon, the aponeurosis, the fascicles and the angle of pennation of the GM. To calculate the elongation of the GM muscle-tendon unit the Achilles tendon path was reconstructed using a series of small reflective markers. The results show that the passive ankle joint angular displacement has a considerable influence on the elongation of the tendinous and architectural structures of the GM muscle-tendon unit. In contrast, the influence of knee joint angular displacement on the GM fascicle length and pennation angle becomes relevant only at knee angles greater than 144 degrees . The contribution of the tendon to the elongation of the GM muscle-tendon unit at rest is relevant because of its greater resting length in comparison to the resting length of the GM fascicles. The results indicate the existence of slackness in the inactive GM muscle-tendon unit between 121 degrees and 107 degrees ankle angle and between 65 degrees and 144 degrees knee angle.

Adult↗

PubMed2005

Effect of different ankle- and knee-joint positions on gastrocnemius medialis fascicle length and EMG activity during isometric plantar flexion.

The purpose of this study was to provide evidence on the fact that the observed decrease in EMG activity of the gastrocnemius medialis (GM) at pronounced knee flexed positions is not only due to GM insufficiency, by examining muscle fascicle lengths during maximal voluntary contractions at different positions. Twenty-two male long distance runners (body mass: 78.5+/-6.7 kg, height: 183+/-6 cm) participated in the study. The subjects performed isometric maximal voluntary plantar flexion contractions (MVC) of their left leg at six ankle-knee angle combinations. To examine the resultant ankle joint moments the kinematics of the left leg were recorded using a Vicon 624 system with 8 cameras operating at 120 Hz. The EMG activity of GM, gastrocnemius lateralis (GL), soleus (SOL) and tibialis anterior (TA) were measured using surface electromyography. Synchronously, fascicle length and pennation angle values of the GM were obtained at rest and at the plateau of the maximal plantar flexion using ultrasonography. The main findings were: (a) identifiable differences in fascicle length of the GM at rest do not necessarily imply that these differences would also exist during a maximal isometric plantar flexion contraction and (b) the EMG activity of the biarticular GM during the MVC decreased at a pronounced flexed knee-joint position (up to 110 degrees ) despite of no differences in GM fascicle length. It is suggested that the decrease in EMG activity of the GM at pronounced knee flexed positions is due to a critical force-length potential of all three muscles of the triceps surae.

Ankle Joint↗

PubMed2005

Inevitable joint angular rotation affects muscle architecture during isometric contraction.

The purpose of this study was to quantify the influence of inevitable ankle joint motion during an isometric contraction on the measured change of the gastrocnemius medialis muscle (GM) architecture in vivo during the loading and the unloading phase. Sitting on a dynamometer subjects performed isometric maximal voluntary contractions as well as contractions induced by electrostimulation. Synchronous joint angular motion, plantarflexion moment, foot's centre of pressure and real-time ultrasonography of muscle architecture changes of the GM were obtained. During the contraction the ankle joint position altered and significantly affected the change in muscle architecture. At maximal tendon force (1094+/-323 N), the measured fascicle length overestimated the change in fascicle length due to the tendon force by 1.53 cm, while the measured pennation angle overestimated the change in pennation angle due to the tendon force by 5.5 degrees . At the same tendon force the measured fascicle length and pennation angle were significantly different between loading and unloading conditions. After correcting the values for the change in ankle joint angle no differences between the loading and the unloading phase at the same tendon force were found. Concerning the estimation of GM fascicle length-force and pennation angle-force curves during the loading and unloading phase of an isometric contraction, these findings indicate that not accounting for ankle joint motion will produce unreliable results.

Ankle Joint↗

PubMed2005

Strain and elongation of the vastus lateralis aponeurosis and tendon in vivo during maximal isometric contraction.

The strain and elongation of the vastus lateralis (VL) tendon, tendon plus aponeurosis, and aponeurosis were examined during maximal voluntary contractions on a Biodex-dynamometer (knee angle 115 degrees , hip angle 140 degrees ) in 12 sprinters. Following a warm-up phase, the subjects were instructed to perform a gradual maximal knee extension and hold it for about 3 s. The kinematics of the leg were recorded using a Vicon 512 system with eight cameras operating at 120 Hz. Ultrasonography images were taken simultaneously from the VL myotendinous junction and the mid lateral part of the VL muscle belly. During the maximal isometric knee extensions, the knee joint rotated (13.6+/-5.9 degrees ), leading to an overestimation of the elongation of the tendinous tissues. After correcting for this, the maximal elongation of the VL tendon examined at the myotendinous junction was lower (P<0.05) than the maximal elongation of the VL tendon plus aponeurosis examined at the muscle belly (15 vs. 27 mm, respectively). The maximal estimated strains of the tendon, tendon plus aponeurosis, and aponeurosis showed no statistical differences (8+/-2%, 8+/-1%, and 7+/-2%, respectively, P>0.05). It is concluded that the strains of the human VL tendon, VL tendon plus aponeurosis, and VL aponeurosis, as estimated in vivo by two dimensional ultrasound during maximal isometric contractions, do not differ from each other. The displacement measured at a cross point in the VL muscle belly is significantly greater than that measured at the VL myotendinous junction.

Adult↗

PubMed2005

Differences between measured and resultant joint moments during isometric contractions at the ankle joint.

The purpose of this study was to examine two hypotheses: (a) during voluntary and electrically induced isometric contractions the moments measured at the dynamometer are different from the resultant moments in the same plane around the ankle joint and (b) at a given resultant moment during electrically induced isometric contractions the ankle angle while loading is different from the ankle angle while unloading. Twenty-seven long distance runners participated in the study. All subjects performed isometric maximal voluntary contractions (MVC) and contractions induced by electrostimulation at four different ankle-knee angle combinations on a Biodex-dynamometer. The kinematics of the leg were recorded using the vicon 624 system with eight cameras operating at 120 Hz. The main findings were: (a) the resultant moment at the ankle joint and the moment measured by the Biodex-dynamometer during isometric contractions are different, (b) during a plantar flexion effort the ankle angle changes significantly, whereas the knee angle shows only small and in most cases not significant changes, and (c) at identical resultant ankle joint moments the ankle angles are different between the loading and the unloading phases. The observed differences may lead to erroneous conclusions concerning the following: (a) diagnostic of muscle architecture, (b) estimation of the moment-ankle angle relationship and (c) estimation of the strain and hysteresis of tendons and aponeuroses.

Ankle Joint↗

PubMed2005

Mechanical and morphological properties of different muscle-tendon units in the lower extremity and running mechanics: effect of aging and physical activity.

The objectives of this work were (i) to investigate whether chronic endurance running is a sufficient stimulus to counteract the age-related changes in the mechanical and morphological properties of human triceps surae (TS) and quadriceps femoris (QF) muscle-tendon units (MTUs) by comparing runners and non-active subjects at different ages (young and old), (ii) to identify adaptational phenomena in running mechanics due to age-related changes in the mechanical and morphological properties of the TS and QF MTUs, and finally (iii) to examine whether chronic endurance-running exercise is associated with adaptational effects on running characteristics in old and young adults. The investigation was conducted on 30 old and 19 young adult males divided into two subgroups according to their running activity: endurance-runners vs non-active. To analyse the properties of the MTUs, all subjects performed isometric maximal voluntary (MVC) ankle plantarflexion and knee extension contractions at 11 different MTU lengths on a dynamometer. The activation of the TS and QF during MVC was estimated by surface electromyography. The gastrocnemius medialis and the vastus lateralis and their distal aponeuroses were visualized by ultrasonography at rest and during MVC, respectively. Ground reaction forces and kinematic data were recorded during running trials at 2.7 m s(-1). The TS and QF MTU capacities were reduced with aging (lower muscle strength and lower tendon stiffness). Runners and non-active subjects had similar MTU properties, suggesting that chronic endurance-running exercise does not counteract the age-related degeneration of the MTUs. Runners showed a higher mechanical advantage for the QF MTU while running (lower gear ratio) compared to non-active subjects, indicating a task-specific adaptation even at old age. Older adults reacted to the reduced capacities of their MTUs by increasing running safety (higher duty factor, lower flight time) and benefitting from a mechanical advantage for the TS MTU, lower rate of force generation and force generation per meter distance. We suggest that the improvement in running mechanics in the older adults happens due to a perceptual motor recalibration and a feed-forward adaptation of the motor task aimed at decreasing the disparity between the reduced capacity of the MTUs and the running effort.

Adult↗

PubMed2004

Differences between measured and resultant joint moments during voluntary and artificially elicited isometric knee extension contractions.

OBJECTIVE: Examine two hypotheses: (a) during isometric knee extension contractions the moment measured at the dynamometer is different from the resultant moment in the same plane around the knee joint and (b) during isometric contractions, at the same given resultant moment the knee angle while loading is different from the knee angle while unloading. DESIGN: Comparative study in which the geometrical and the kinetic differences between joint and dynamometer were determined. BACKGROUND: It is usually assumed that the moment measured by the dynamometer is equivalent to the resultant joint moment. The non-rigidity of the dynamometer-leg system can influence the equivalence of these two moments. METHOD: Twenty seven subjects performed isometric maximal knee extension contractions and contractions induced by electrostimulation on a dynamometer. The kinematics of the leg were recorded using 8 cameras (120 Hz). RESULTS: The resultant moment at the knee joint and the moment measured by the dynamometer are different. During a knee extension effort the knee angle changes significantly. At identical resultant knee joint moments the knee angles are different when comparing the loading and the unloading phases. CONCLUSIONS: The differences between the measured and the resultant joint moments might influence the estimation of parameters as: muscle forces, moment-angle relationship and strain and hysteresis of tendons and aponeuroses. RELEVANCE: Torque dynamometers have been often used to estimate muscle forces, to examine neuromuscular processes and to determine the mechanical properties of tendons and aponeuroses.

Biomechanical Phenomena↗

PubMed2004

Reproducibility of electromyography and ground reaction force during various running techniques.

This study examined the validity of the assumption of electromyographic (EMG) and vertical ground reaction force (GRF) parameter reproducibility during running at different velocities and stride frequencies. Each of 12 female long distance runners ran on a treadmill in combinations of three velocities (2.5, 3.0 and 3.5 m/s) and three stride frequencies (preferred, +/-10% from preferred). Seven parameters from the GRF and five parameters from the EMG signals from five muscles of the lower extremity were evaluated (1000 Hz). The GRF was analysed by a pressure measuring insoles. A total number of three trials for each running condition were recorded. GRF parameters during all running conditions showed high intraclass correlation coefficients (ICC average 0.87). The ICC of the EMG parameters of gastrocnemius medialis and lateralis were high (r>0.69 in 73% of the data), while those for vastus lateralis (22%), hamstrings (42%) and tibialis anterior (51%) were clearly lower. The results revealed that GRF parameters were reproducible during all running techniques indicating that a single trial would provide reproducible GRF-data. The reproducibility of the EMG parameters was not influenced by the running technique but dependent on the parameter itself and on the muscle studied.

Adult↗

PubMed2003

Symmetry and reproducibility of kinematic parameters during various running techniques.

PURPOSE: This study examined the validity of the assumption of lower-extremity kinematic parameter reproducibility and symmetry during running with different velocities and stride frequencies. METHODS: Each of 12 female long-distance runners ran on a treadmill in combinations of three different velocities (2.5, 3.0, and 3.5 m.s-1) and three different stride frequencies (preferred and +/- 10% from preferred). The left and right sides of the athletes were filmed using video cameras placed orthogonally to the sagittal plane. A total number of three step cycles for each running condition were recorded (250 Hz). For each side of the body, 19 sagittal kinematic parameters from the lower extremity were evaluated. RESULTS: Intraclass correlation coefficients (ICC) for both legs were high (generally > 0.80). Only the angular velocity parameters demonstrated correlation values below 0.70. The symmetry index for the linear and angular displacement parameters and the contact times during all running techniques were less than 8%, whereas those for the angular velocity parameters and flight times were higher than 15%. CONCLUSION: The present results suggested that the degree of reproducibility and symmetry of kinematic data do not vary with a deliberate change in running technique but rather depend on the parameter itself. With respect to the economy of data analysis, the present findings indicate that recording a single monolateral trial would provide reproducible and symmetric values for most kinematic parameters.

Adult↗