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1.
Scand J Med Sci Sports ; 28(3): 961-971, 2018 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-29154407

RESUMEN

The purpose of this study was to assess the effectiveness of a specific exercise intervention of mechanisms to control dynamic postural stability under unstable conditions in old adults. Forty-seven old adults (65-80 years) were assigned to 2 experimental groups (muscle strength group, n = 15; perturbation-based group, n = 16) and a control group (n = 16). The strength group performed resistance exercises for leg and trunk muscles, while the perturbation-based group exercised mechanisms of dynamic stability under unstable conditions. The training duration was 14 weeks, with training sessions twice a week for 1.5 hours. Muscle strength, balance ability, and balance recovery performance were investigated before and after the interventions using maximal isometric plantar flexion and knee extension contractions, the approach of the center of pressure to the anterior limits of stability and simulated forward falls. Both interventions increased balance recovery performance in simulated forward falls (81%, d = 1.50 and 80%, d = 1.08 in the muscle strength and perturbation-based group, respectively), while the control group did not show any changes. Plantar flexor strength increased 20% (d = 0.72) in the muscle strength and 23% (d = 1.03) in the perturbation-based group, while muscle strength of the knee extensors increased only in the muscle strength group (8%, d = 0.76). On the other hand, only the perturbation-based group showed a significant improvement of standing balance ability (38%, d = 1.61). We conclude that a perturbation-based training program focusing on exercising mechanisms of dynamic stability in unstable conditions has the potential to enhance muscle strength as well as sensory information processing within the motor system during sudden and static balance tasks and, as a consequence, reduce the risk of falls in old adults.


Asunto(s)
Terapia por Ejercicio , Fuerza Muscular , Equilibrio Postural , Entrenamiento de Fuerza , Accidentes por Caídas/prevención & control , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Músculo Esquelético/fisiología
2.
Scand J Med Sci Sports ; 27(1): 75-82, 2017 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26644277

RESUMEN

There is evidence that a non-uniform adaptation of muscle and tendon in young athletes results in increased tendon stress during mid-adolescence. The present longitudinal study investigated the development of the morphological and mechanical properties of muscle and tendon of volleyball athletes in a time period of 2 years from mid-adolescence to late adolescence. Eighteen elite volleyball athletes participated in magnetic resonance imaging and ultrasound-dynamometry sessions to determine quadriceps femoris muscle strength, vastus lateralis, medialis and intermedius morphology, and patellar tendon mechanical and morphological properties in mid-adolescence (16 ± 1 years) and late adolescence (18 ± 1 years). Muscle strength, anatomical cross-sectional area (CSA), and volume showed significant (P < 0.05) but moderate increases of 13%, 6%, and 6%, respectively. The increase of patellar tendon CSA (P < 0.05) was substantially greater (27%) and went in line with increased stiffness (P < 0.05; 25%) and reduced stress (P < 0.05; 9%). During late adolescence, a pronounced hypertrophy of the patellar tendon led to a mechanical strengthening of the tendon in relation to the functional and morphological development of the muscle. These adaptive processes may compensate the unfavorable relation of muscle strength and tendon loading capacity in mid-adolescence and might have implications on athletic performance and tendon injury risk.


Asunto(s)
Adaptación Fisiológica/fisiología , Atletas , Ligamento Rotuliano/diagnóstico por imagen , Músculo Cuádriceps/diagnóstico por imagen , Voleibol , Adolescente , Femenino , Humanos , Estudios Longitudinales , Imagen por Resonancia Magnética , Masculino , Fuerza Muscular , Dinamómetro de Fuerza Muscular , Músculo Esquelético/anatomía & histología , Músculo Esquelético/diagnóstico por imagen , Músculo Esquelético/fisiología , Tamaño de los Órganos , Ligamento Rotuliano/fisiología , Músculo Cuádriceps/anatomía & histología , Músculo Cuádriceps/fisiología , Tendones/diagnóstico por imagen , Tendones/fisiología , Ultrasonografía
3.
Scand J Med Sci Sports ; 25(1): e124-32, 2015 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-24798645

RESUMEN

Although symmetry of Achilles tendon (AT) properties between legs is commonly assumed in research and clinical settings, different loading profiles of both legs in daily life (i.e., foot dominance) may affect the tendon properties in a side-depended manner. Therefore, AT properties were examined with regard to symmetry between legs. Thirty-six male healthy adults (28 ± 4 years), who were physically active but not involved in sports featuring dissimilar leg load participated. Mechanical and morphological AT properties of the non-dominant and dominant leg were measured by means of ultrasound, magnetic resonance imaging and dynamometry. The AT of the dominant leg featured a significant higher Young's modulus and length (P < 0.05) but a tendency toward lower maximum strain (P = 0.068) compared with the non-dominant leg. The tendon cross-sectional area and stiffness were not significantly different between sides. The absolute asymmetry index of the investigated parameters ranged from 3% to 31% indicating poor AT side symmetry. These findings provide evidence of distinct differences of AT properties between both legs in a population without any sport-specific side-depended leg loading. The observed asymmetry may be a result of different loading profiles of both legs during daily activities (i.e., foot dominance) and challenges the general assumption of symmetrical AT properties between legs.


Asunto(s)
Tendón Calcáneo/fisiología , Lateralidad Funcional/fisiología , Tendón Calcáneo/anatomía & histología , Tendón Calcáneo/diagnóstico por imagen , Adulto , Electromiografía , Humanos , Imagen por Resonancia Magnética , Masculino , Dinamómetro de Fuerza Muscular , Tamaño de los Órganos , Ultrasonografía , Adulto Joven
4.
Scand J Med Sci Sports ; 25(2): e208-13, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-24975992

RESUMEN

The present study investigated the applicability of a muscle volume prediction method using only the muscle length (L(M)), the maximum anatomical cross-sectional area (ACSA(max)), and a muscle-specific shape factor (p) on the quadriceps vastii. L(M), ACSA(max), muscle volume, and p were obtained from magnetic resonance images of the vastus intermedius (VI), lateralis (VL), and medialis (VM) of female (n = 20) and male (n = 17) volleyball athletes. The average p was used to predict muscle volumes (V(p)) using the equation V(p) = p × ACSA(max) × L(M). Although there were significant differences in the muscle dimensions between male and female athletes, p was similar and on average 0.582, 0.658, 0.543 for the VI, VL, and VM, respectively. The position of ACSA(max) showed low variability and was at 57%, 60%, and 81% of the thigh length for VI, VL, and VM. Further, there were no significant differences between measured and predicted muscle volumes with root mean square differences of 5-8%. These results suggest that the muscle shape of the quadriceps vastii is independent of muscle dimensions or sex and that the prediction method could be sensitive enough to detect changes in muscle volume related to degeneration, atrophy, or hypertrophy.


Asunto(s)
Anatomía Transversal , Músculo Cuádriceps/anatomía & histología , Muslo/anatomía & histología , Adulto , Tamaño Corporal , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Modelos Biológicos , Caracteres Sexuales , Voleibol
5.
Scand J Med Sci Sports ; 25(6): 860-7, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-25902929

RESUMEN

Achilles tendon rupture (ATR) alters tissue composition, which may affect long-term tendon mechanics and ankle function during movement. However, a relationship between Achilles tendon (AT) properties and ankle joint function during gait remains unclear. The primary hypotheses were that (a) post-ATR tendon stiffness and length differ from the noninjured contralateral side and that (b) intra-patient asymmetries in AT properties correlate to ankle function asymmetries during gait, determined by ankle angles and moments. Ultrasonography and dynamometry were used to assess AT tendon stiffness, strain, elongation, and rest length in both limbs of 20 ATR patients 2-6 years after repair. Three-dimensional ankle angles and moments were determined using gait analysis. Injured tendons exhibited increased stiffness, rest length, and altered kinematics, with higher dorsiflexion and eversion, and lower plantarflexion and inversion. Intra-patient tendon stiffness and tendon length ratios were negatively correlated to intra-patient ratios of the maximum plantarflexion moment and maximum dorsiflexion angle, respectively. These results suggest that after surgical ATR repair, higher AT stiffness, but not a longer AT, may contribute to deficits in plantarflexion moment generation. These data further support the claim that post-ATR tendon regeneration results in the production of a tissue that is functionally different than noninjured tendon.


Asunto(s)
Tendón Calcáneo/lesiones , Tendón Calcáneo/fisiopatología , Elasticidad , Marcha/fisiología , Tendón Calcáneo/diagnóstico por imagen , Adulto , Articulación del Tobillo/fisiopatología , Fenómenos Biomecánicos , Diagnóstico por Imagen de Elasticidad , Femenino , Humanos , Masculino , Persona de Mediana Edad , Rango del Movimiento Articular , Rotura/diagnóstico por imagen , Rotura/fisiopatología , Factores de Tiempo
6.
Scand J Med Sci Sports ; 24(4): e283-9, 2014 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-24372566

RESUMEN

Adolescence may be regarded as a critical phase of tissue plasticity in young growing athletes, as the adaptation process of muscle-tendon unit is affected by both environmental mechanical stimuli and maturation. The present study investigated potential imbalances of knee extensor muscle strength and patellar tendon properties in adolescent compared with middle-aged athletes featuring long-term musculotendinous adaptations. Nineteen adolescent elite volleyball athletes [(A), 15.9 ± 0.6 years] and 18 middle-aged competitively active former elite volleyball athletes [(MA), 46.9 ± 0.6 years] participated in magnetic resonance imaging and ultrasound-dynamometry sessions to determine quadriceps femoris muscle strength, vastus lateralis morphology and patellar tendon mechanical and morphological properties. There was no significant age effect on the physiological cross-sectional area of the vastus lateralis and maximum knee extension moment (P > 0.05) during voluntary isometric contractions. However, the patellar tendon cross-sectional area was significantly smaller (A: 107.4 ± 27.5 mm(2) ; MA: 121.7 ± 39.8 mm(2) ) and the tendon stress during the maximal contractions was significantly higher in adolescent compared with the middle-aged athletes (A: 50.0 ± 10.1 MPa; MA: 40.0 ± 9.5 MPa). These findings provide evidence of an imbalanced development of muscle strength and tendon mechanical and morphological properties in adolescent athletes, which may have implications for the risk of tendon overuse injuries.


Asunto(s)
Adaptación Fisiológica , Ligamento Rotuliano/fisiopatología , Músculo Cuádriceps/fisiopatología , Voleibol/fisiología , Adolescente , Adulto , Factores de Edad , Módulo de Elasticidad/fisiología , Femenino , Humanos , Contracción Isométrica , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Fuerza Muscular , Ligamento Rotuliano/patología , Músculo Cuádriceps/patología , Factores Sexuales , Estrés Fisiológico/fisiología
7.
Sci Rep ; 13(1): 8661, 2023 05 29.
Artículo en Inglés | MEDLINE | ID: mdl-37248376

RESUMEN

Tendon strain during exercise is a critical regulatory factor in tendon adaptive responses and there are indications for an optimal range of strain that promotes tendon adaptation. Back squats are used to improve patellar tendon properties in sport and clinical settings. To date, the operating patellar tendon strain during back squats is unknown and current recommendations for individual exercise loading are based on the one repetition maximum (1RM). Here, we quantified patellar tendon strain during loaded back squats at 40, 60 and 80% of the 1RM and during maximum isometric knee extension contractions (MVC) using ultrasonography. Kinematics, ground reaction forces and muscle electromyographic activity were also recorded. Additionally, maximum tendon strain during the MVC and the percentage of 1RM were used as explanatory variables to estimate the individual patellar tendon strain during the squats. Strain increased with increasing 1RM loading (4.7 to 8.2%), indicating that already medium-loading back squats may provide a sufficient stimulus for tendon adaptation. The individual variability was, however, too high to generalize these findings. Yet, there was a high agreement between the individually estimated and measured patellar tendon strain (R2 = 0.858) during back squats. We argue that this approach may provide new opportunities for personalized tendon exercise.


Asunto(s)
Ligamento Rotuliano , Traumatismos de los Tendones , Humanos , Ligamento Rotuliano/diagnóstico por imagen , Ligamento Rotuliano/fisiología , Tendones , Articulación de la Rodilla/diagnóstico por imagen , Articulación de la Rodilla/fisiología , Extremidad Inferior/fisiología , Rodilla , Fenómenos Biomecánicos
9.
Sci Rep ; 12(1): 21901, 2022 12 19.
Artículo en Inglés | MEDLINE | ID: mdl-36535994

RESUMEN

This study investigated transfer of improvements in stability recovery performance to novel perturbations. Thirty adults (20-53 yr) were assigned equally to three treadmill walking groups: groups exposed to eight trip perturbations of either low or high magnitude and a third control group that walked unperturbed. Following treadmill walking, participants were exposed to stability loss from a forward-inclined position (lean-and-release) and an overground trip. Lower limb joint kinematics for the swing phase of recovery steps was compared for the three tasks using statistical parametric mapping and recovery performance was analysed by margin of stability and base of support. The perturbation groups improved stability (greater margin of stability) over the eight gait perturbations. There was no group effect for stability recovery in lean-and-release. For the overground trip, both perturbation groups showed similar enhanced stability recovery (margin of stability and base of support) compared to controls. Differences in joint angle kinematics between treadmill-perturbation and lean-and-release were more prolonged and greater than between the two gait perturbation tasks. This study indicates that: (i) practising stability control enhances human resilience to novel perturbations; (ii) enhancement is not necessarily dependent on perturbation magnitude; (iii) differences in motor response patterns between tasks may limit transfer.


Asunto(s)
Equilibrio Postural , Caminata , Adulto , Humanos , Equilibrio Postural/fisiología , Caminata/fisiología , Marcha/fisiología , Fenómenos Biomecánicos , Prueba de Esfuerzo
10.
J Biomech ; 125: 110584, 2021 08 26.
Artículo en Inglés | MEDLINE | ID: mdl-34217031

RESUMEN

The ability to effectively increase the base of support is crucial to prevent from falling due to stability disturbances and has been commonly assessed using the forward-directed lean-and-release test. With this multicentre study we examined whether the assessment of stability recovery performance using two different forward lean-and-release test protocols is reliable in adults over a wide age range. Ninety-seven healthy adults (age from 21 to 80 years) were randomly assigned to one out of two lean angle protocols: gradual increase to maximal forward-lean angle (maximal lean angle; n = 43; seven participants were excluded due to marker artefacts) or predefined lean angle (single lean angle; n = 26; 21 participants needed to be excluded due to multiple stepping after release or marker artefacts). Both protocols were repeated after 0.5 h and 48 h to investigate intra- and inter-session reliability. Stability recovery performance was examined using the margin of stability at release (MoSRL) and touchdown (MoSTD) and increase in base of support (BoSTD). Intraclass correlation coefficients (confidence intervals at 95%) for the maximal lean angle and for the single lean angle were respectively 0.93 (0.89-0.96) and 0.94 (0.89-0.97) in MoSRL, 0.85 (0.77-0.91) and 0.67 (0.48-0.82) in MoSTD and 0.88 (0.81-0.93) and 0.80 (0.66-0.90) in BoSTD, with equivalence being revealed for each parameter between all three measurements (p < 0.01). We concluded that the assessment of stability recovery performance parameters in adults over a wide age range with the means of the forward lean-and-release test is reliable, independent of the used lean angle protocol.


Asunto(s)
Accidentes por Caídas , Equilibrio Postural , Adulto , Humanos , Recién Nacido , Estudios Multicéntricos como Asunto , Ensayos Clínicos Controlados Aleatorios como Asunto , Reproducibilidad de los Resultados
12.
J Biomech ; 41(10): 2211-8, 2008 Jul 19.
Artículo en Inglés | MEDLINE | ID: mdl-18555257

RESUMEN

The purpose of the present study was to investigate whether it is possible to predict the individual muscle volumes within the triceps surae (TS) muscle group by means of easily measurable parameters based on a theoretical consideration. A further objective was to verify the use of the available literature data to assess the contribution of each muscle of the group to the entire TS volume or physiological cross-sectional-area (PCSA). Therefore, magnetic resonance images of the right calf of 13 male subjects were acquired and each muscle of the TS was reconstructed. Muscle length (l(m)), the maximum anatomical cross-sectional-area (ACSA(max)) and muscle volume were obtained from the 3D models. To assess the PCSA, fascicle length was determined by ultrasonography. In general, muscle volume can be expressed as a fraction of the product of ACSA(max) and l(m). The size of the fraction depends on muscle shape and its coefficient of variance among the examined population was considerable low (soleus 6%, gastrocnemius 4% and gastrocnemius lateralis 7%) in the present study. The product of ACSA(max) and l(m) was, therefore, suitable to assess muscle volume (root mean squares, RMS 4-7%). Further, the soleus, gastrocnemius medialis and gastrocnemius lateralis accounted on average for about 52+/-3%, 32+/-2% and 16+/-2% of the total TS volume and 62+/-5%, 26+/-3% and 12+/-2% of the entire TS PCSA, respectively. The coefficient of variance of the relative portions were 5-10% for muscle volume and 8-17% for the PCSA.


Asunto(s)
Fenómenos Biomecánicos/métodos , Pierna/patología , Músculo Esquelético/patología , Músculos/patología , Adulto , Humanos , Contracción Isométrica/fisiología , Imagen por Resonancia Magnética/métodos , Masculino , Modelos Anatómicos , Modelos Estadísticos , Contracción Muscular , Equilibrio Postural , Ultrasonografía/métodos
13.
Sci Rep ; 8(1): 5066, 2018 03 22.
Artículo en Inglés | MEDLINE | ID: mdl-29567999

RESUMEN

According to the force-length-velocity relationships, the muscle force potential during locomotion is determined by the operating fibre length and velocity. We measured fascicle and muscle-tendon unit length and velocity as well as the activity of the human vastus lateralis muscle (VL) during walking and running. Furthermore, we determined the VL force-length relationship experimentally and calculated the force-length and force-velocity potentials (i.e. fraction of maximum force according to the force-length-velocity curves) for both gaits. During the active state of the stance phase, fascicles showed significantly (p < 0.05) smaller length changes (walking: 9.2 ± 4.7% of optimal length (L0); running: 9.0 ± 8.4%L0) and lower velocities (0.46 ± 0.36 L0/s; 0.03 ± 0.83 L0/s) compared to the muscle-tendon unit (walking: 19.7 ± 5.3%L0, -0.94 ± 0.32 L0/s; running: 34.5 ± 5.8%L0, -2.59 ± 0.41 L0/s). The VL fascicles operated close to optimum length (L0 = 9.4 ± 0.11 cm) in both walking (8.6 ± 0.14 cm) and running (10.1 ± 0.19 cm), resulting in high force-length (walking: 0.92 ± 0.08; running: 0.91 ± 0.14) and force-velocity (0.91 ± 0.08; 0.97 ± 0.13) potentials. For the first time we demonstrated that, in contrast to the current general conception, the VL fascicles operate almost isometrically and close to L0 during the active state of the stance phase of walking and running. The findings further verify an important contribution of the series-elastic element to VL fascicle dynamics.


Asunto(s)
Músculo Esquelético/fisiología , Músculo Cuádriceps/fisiología , Carrera/fisiología , Caminata/fisiología , Adulto , Fenómenos Biomecánicos , Electromiografía , Femenino , Marcha/fisiología , Humanos , Masculino , Contracción Muscular/fisiología , Tendones/fisiología
14.
J Biomech ; 38(4): 833-41, 2005 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-15713305

RESUMEN

Regarding the strain and elongation distribution along the tendon and aponeurosis the literature is reporting different findings. Therefore, the purpose of this study was to examine in vivo the elongation and the strain of the human gastrocnemius medialis tendon and aponeurosis simultaneously at the same trial during maximal voluntary plantarflexion efforts. Twelve subjects participated in the study. The subjects performed isometric maximal voluntary contractions of their left leg on a Biodex-dynamometer. The kinematics of the leg were recorded using the Vicon 624 system with 8 cameras operating at 120 Hz. Two ultrasound probes were used to visualise the tendon (myotendinous junction region) and the distal aponeurosis of the gastrocnemius medialis respectively. The main findings were: (a) the absolute elongation of the gastrocnemius medialis tendon was different to that of the aponeurosis, (b) the strain of the gastrocnemius medialis tendon did not differ from the strain of the aponeurosis, (c) during the "isometric" plantarflexion the ankle angle exhibited significant changes, and (d) the non-rigidity of the dynamometer arm-foot system and the coactivity of the tibialis anterior both have a significant influence on the moment exerted at the ankle joint. Thus the strain of the human gastrocnemius medialis tendon and aponeurosis estimated in vivo using two-dimensional ultrasonography is uniform. To calculate the elongation of the whole tendon it is necessary to multiply the strain calculated for the examined part of the tendon by the total length of the tendon.


Asunto(s)
Contracción Isométrica/fisiología , Estrés Mecánico , Tendones/fisiología , Tendón Calcáneo , Adolescente , Adulto , Articulación del Tobillo/fisiología , Elasticidad , Humanos , Pierna/fisiología , Músculo Esquelético/fisiología , Docilidad , Tendones/anatomía & histología , Tendones/diagnóstico por imagen , Ultrasonografía/métodos , Grabación en Video
15.
Sportverletz Sportschaden ; 19(1): 15-21, 2005 Mar.
Artículo en Alemán | MEDLINE | ID: mdl-15776324

RESUMEN

PURPOSE: In this study two groups of ACL-rupture patients having had a conservative or an operative treatment and a similar rehabilitation were compared regarding their muscle strength capabilities, and the clinical outcome. METHODS: Thirty-three patients (mean age 31 years) were selected according to the Lysholm-scores. Twelve patients were conservatively treated (Group I) and were examined between six and 16 months post trauma. Group II consisted of 21 operatively treated patients which were examined between 6 and 16 months post surgery. All patients underwent a clinical exam following the OAK evaluation form and were tested on a Cybex 6000 isokinetic machine. The subjects had to perform concentric contractions of the extensor and flexor muscles of the knee, hip and ankle at 60 and 120 degrees /s. In addition the knee musculature was isometrically tested at knee angles of 0 and 45 degrees . RESULTS: The clinical examination revealed significant (P < 0.05) differences between groups. The operatively treated patients scored better at the tests for ligamentous stability, whereas the testing of the muscular capabilities revealed significant differences (P < 0.05) favouring the conservatively treated patients in the isokinetic measures, (maximal concentric torque M (max,con)) of the knee extensors, knee flexors, and ankle plantarflexors. CONCLUSION: Whereas the clinical examination only revealed the ligamentous stability to be better results in the operatively treated patients, the conservatively treated patients showed better results in the isokinetik strength measures of the knee extensors, knee flexors, and ankle plantarflexors. The better muscular profiles found for the conservatively treated patients suggest that a better regeneration of the corresponding muscular capabilities after an ACL rupture is possible, provided a specific and controlled rehabilitation program is performed. This seems to be more difficult in operatively treated patients even six to 16 months after the surgical intervention.


Asunto(s)
Lesiones del Ligamento Cruzado Anterior , Ligamento Cruzado Anterior/cirugía , Traumatismos de la Rodilla/terapia , Articulación de la Rodilla/fisiología , Músculo Esquelético/fisiología , Adulto , Interpretación Estadística de Datos , Estudios de Seguimiento , Humanos , Contracción Isométrica , Traumatismos de la Rodilla/rehabilitación , Traumatismos de la Rodilla/cirugía , Ligamentos Articulares/fisiología , Modelos Estadísticos , Contracción Muscular/fisiología , Rotura/rehabilitación , Factores de Tiempo , Resultado del Tratamiento
16.
Med Sci Sports Exerc ; 33(6): 923-31, 2001 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-11404657

RESUMEN

PURPOSE: The purposes of this study were: a) to examine the effect of verbal instructions given to the subjects on the control of lower extremity stiffness and b) to determine the effect of leg stiffness on mechanical energetic processes during drop jumps on a sprung surface. METHODS: A total of 10 female athletes performed a series of drop jumps on a sprung surface from heights of 20 and 40 cm. The instructions given to the subjects were a) "jump as high as you can" and b) "jump high a little faster than at your previous jump." The jumps were performed at each height until the athlete could not achieve a shorter ground contact time. Four jumps per subject per height were analyzed. The ground reaction forces were measured using a "Kistler" force plate (1000 Hz). The athletes' body positions were recorded using a high-speed (250 Hz) video camera. The deformation of the sprung surface was determined by another high-speed camera operating at 500 Hz. Surface EMG was used to measure muscle activity in five leg muscles. RESULTS: The contact time showed high correlation with leg stiffness as well as with ankle and knee stiffness. The change in leg stiffness was not due to the duration of the preactivation but rather to the level of activation during this phase. An increase in leg stiffness caused an increase in the energy stored and recovered in and by the sprung surface and a decrease of the energy produced by the subjects. CONCLUSIONS: By influencing contact time through verbal instructions, it is possible to control leg stiffness. Maximal vertical take-off velocity of the center of mass and maximal take-off body energy can be achieved having different levels of leg stiffness. The maximization of mechanical power is achieved by optimal leg stiffness values and leg muscle preactivation levels.


Asunto(s)
Articulación de la Rodilla/patología , Pierna/fisiología , Locomoción/fisiología , Adulto , Fenómenos Biomecánicos , Simulación por Computador , Metabolismo Energético , Femenino , Humanos , Articulación de la Rodilla/fisiología , Materiales Manufacturados , Músculo Esquelético/fisiología , Rango del Movimiento Articular
17.
J Biomech ; 33(10): 1263-8, 2000 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-10899336

RESUMEN

The purposes of this study were as follows: (1) To determine the differences between two- and three-dimensionally calculated energy of the athlete in the pole vault. (2) To determine the differences between CM energy and total body energy. (3) To examine the influence of these different approaches of calculating the athlete's energy on energetic parameter values during the pole vault. Kinematic data were gathered during the pole vault final of the track and field world championships in 1997. Two video cameras (50Hz) covered the last step of the approach including the pole plant and 2 cameras covered the pole phase up to bar clearance, respectively. Twenty successful jumps were analysed. The characteristics of the energy development is similar for the different approaches. Initial energy, energy at maximum pole bend and energy at pole release (primary parameters) show significant differences (p<0.05). The findings indicate that rotatory movements and movements relative to the CM have a larger influence on the primary parameters than movements apart from the main plane of movement. For analysing the energy exchange between the athlete and the elastic implement pole only the differences among the secondary parameters (initial energy minus energy at maximum pole bend, final energy minus energy at maximum pole bend) are needed (Arampatzis et al., 1997 Biomechanical Research Project at the Vth World Championships in Athletics, Athens 1997: Preliminary Report. New Studies in Athletics 13, 66-69). For those parameters the relative differences between the calculation approaches range only between 1.47 and 0.04%. This indicates that the influence of the different approaches for calculating the athlete's energy on the analysis of energy exchange is negligible.


Asunto(s)
Metabolismo Energético , Modelos Biológicos , Atletismo , Fenómenos Biomecánicos , Humanos , Cinética
18.
J Biomech ; 31(12): 1083-92, 1998 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-9882040

RESUMEN

The aims of this study were: 1. To study the transfer of energy between the high bar and the gymnast. 2. To develop criteria from the utilisation of high bar elasticity and the utilisation of muscle capacity to assess the effectiveness of a movement solution. 3. To study the influence of varying segment movement upon release parameters. For these purposes a model of the human body attached to the high bar (high bar-human body model) was developed. The human body was modelled using a 15-segment body system. The joint-beam element method (superelement) was employed for modelling the high bar. A superelement consists of four rigid segments connected by joints (two Cardan joints and one rotational-translational joint) and springs (seven rotation springs and one tension-compression spring). The high bar was modelled using three superelements. The input data required for the high bar human body model were collected with video-kinematographic (50 Hz) and dynamometric (500 Hz) techniques. Masses and moments of inertia of the 15 segments were calculated using the data from the Zatsiorsky et al. (1984) model. There are two major phases characteristic of the giant swing prior to dismounts from the high bar. In the first phase the gymnast attempts to supply energy to the high bar-humanbody system through muscle activity and to store this energy in the high bar. The difference between the energy transferred to the high bar and the reduction in the total energy of the body could be adopted as a criterion for the utilisation of high bar elasticity. The energy previously transferred into the high bar is returned to the body during the second phase. An advantageous increase in total body energy at the end of the exercise could only be obtained through muscle energy supply. An index characterising the utilisation of muscle capacity was developed out of the difference between the increase in total body energy and the energy returned from the high bar. A delayed and initially slow but even reduction of hip and shoulder angles provided more advantageous release conditions. The total body energy could be improved by up to 15%, the vertical CM release velocity by up to 10% and the angular momentum by up to 35%.


Asunto(s)
Gimnasia/fisiología , Modelos Biológicos , Equipo Deportivo , Algoritmos , Fenómenos Biomecánicos , Simulación por Computador , Elasticidad , Transferencia de Energía , Articulación de la Cadera/fisiología , Humanos , Cinética , Movimiento/fisiología , Músculo Esquelético/fisiología , Rotación , Articulación del Hombro/fisiología , Estrés Mecánico , Torque , Grabación en Video
19.
J Biomech ; 32(8): 811-20, 1999 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-10433423

RESUMEN

The purposes of this study were as follows: (1) To study the energy exchange between the body of the gymnast and the high bar and uneven parallel bars during forward and backward giant swings. (2) To examine the differences between the mechanical energy produced and the mechanical energy absorbed by the muscles during forward and backward giant swings on the high bar and the uneven parallel bars. The data were gathered during the gymnastic world championships in 1994. The experimental set up consisted of two video cameras (50 Hz) and two force measurement bars (500 Hz). A total of 101 giant swings before dismounts and flight elements performed by 33 male and 34 female gymnasts were analyzed. There are characteristically two main phases during forward and backward giant swings before dismounts and flight elements. During the first phase energy is transferred from the gymnast's body into the bar. During this phase of the backward giant swing the energy of the system decreases because the amount of energy decrease of the gymnast's body is more than the energy transferred into the high bar. An exception can be seen during the giant swings in which the gymnast used the power technique. During forward giant swings the energy of the system increases during the first phase. This occurs through active flexion of the hipjoint which produced the extra muscular energy. During the second phase energy is transferred from the bar back into the gymnast's body whose total energy increases. An increase in the energy of the system can only be achieved through muscular work. During the second phase of the backward giant swing the energy of the system increases. The forward giant swings performed on the uneven parallel bars showed a large energy loss during this phase. The energy deficit seen during the first phase of the backward giant swing can be improved by using the power technique. To achieve this the athlete must be in a bent position at the start of the giant swing exercise. Through extension at the shoulder and hip joints muscular energy can be put into the system.


Asunto(s)
Ejercicio Físico/fisiología , Gimnasia/fisiología , Articulación de la Cadera/fisiología , Movimiento/fisiología , Articulación del Hombro/fisiología , Fenómenos Biomecánicos , Femenino , Humanos , Recién Nacido , Masculino , Modelos Biológicos , Músculo Esquelético/fisiología , Valores de Referencia , Estrés Mecánico , Torque , Grabación en Video
20.
J Biomech ; 34(4): 505-12, 2001 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-11266674

RESUMEN

The goal of this study was to examine the possibility of the utilization of high bar and uneven parallel bar elasticity by the gymnasts through muscular work during the giant swing before the Tkatchev exercise on the high bar or uneven parallel bars. The performances were gathered during the Gymnastic World Championship in 1994. The set up consisted of two video cameras (50Hz) and two force measuring bars (500Hz). Twenty giant swings before the Tkatchev exercise, nine giant swings before the Tkatchev exercise after Tkatchev on the high bar and 15 giant swings before the Tkatchev exercise on the uneven parallel bars were analyzed. The giant swings were performed by 20 male and 15 female gymnasts. There are three phases during the giant swing exercise before the Tkatchev in which the systems (high bar-human body) total energy can be changed. During the first phase, energy is transferred from the gymnast's body into the bar. A clearly effective use of the bar's elasticity during the first phase could not be found. During the second phase, energy is transferred from the bar's back into the gymnast's body whose total energy increases. An increase in the energy of the system can only be achieved through muscular work. During the second phase of the various giant swing techniques no significant (p<0.05) difference in the energy increase through muscular work could be found. During the third phase, energy is once again produced by the gymnast through extension at the hip and shoulder joints.


Asunto(s)
Gimnasia , Transferencia Lineal de Energía , Adulto , Fenómenos Biomecánicos , Femenino , Humanos , Articulaciones/fisiología , Masculino , Modelos Biológicos , Estrés Mecánico
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