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PURPOSE: The goal of this paper was to determine if sports participation influences torque control differently for adolescent boys and young men during a slow ramp task. METHODS: Twenty-one adolescent boys (11 athletes) and 31 young men (16 athletes) performed a slow ramp increase in plantar flexion torque from 0 to maximum. We quantified torque control as the coefficient of variation (CV) of torque during the ramp and quantified the Achilles tendon mechanical properties using ultrasonography. RESULTS: Relative to adolescent boys, young men were taller, heavier, stronger, and had a longer and stiffer Achilles tendon. However, these characteristics were not different between athletes and non-athletes in adolescent boys. For the CV of torque, there was a significant interaction with sports participation, indicating that only adolescent boys who were non-athletes had greater variability than young men. The CV of torque of all participants was predicted from the maximum torque and torque oscillations from 1 to 2 Hz, whereas the CV of torque for adolescent boys was predicted only from torque oscillations from 1 to 2 Hz. CONCLUSION: These findings suggested that adolescent boys who participate in sports exhibited lower torque variability during a slow ramp task, which was not explained by differences in Achilles tendon properties or strength.
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Tendão do Calcâneo , Esportes , Torque , Humanos , Masculino , Adolescente , Adulto Jovem , Atletas , Esportes/fisiologia , Tendão do Calcâneo/fisiologiaRESUMO
This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance and on peak rate of force development (RFDpeak) in preadolescent (10-12 y), adolescents (14-15 y) and adults (20-25 y) males and females. All participants performed a SJ with and without prior conditioning stimulus (PAP and control protocol, respectively), consisting of 3 × 3-second maximal isometric squats. Jump height and RFDpeak of the vertical ground reaction force during SJ were assessed before, and at 20 seconds and at 4 minutes following the conditioning stimulus. The results revealed a different pattern of age-effect on SJ performance within males and females. The RFDpeak significantly increased as a factor of age in both males and females (P < .05). Increase in SJ performance after conditioning stimulus occurred only in men (P < .05), with no effects in teen-males, boys, and female groups. There was a significant PAP effect on RFDpeak in both adult groups (P < .05) and teen-males, with no effects in children. In conclusion, the PAP effects on SJ performance and RFDpeak are age- and sex-dependent; that is PAP appears as a viable method for acutely enhancing SJ performance in men but not in pediatric population.
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Desempenho Atlético/fisiologia , Exercício Físico/fisiologia , Contração Isométrica/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Adolescente , Adulto , Fatores Etários , Fenômenos Biomecânicos , Criança , Feminino , Humanos , Masculino , Fatores Sexuais , Adulto JovemRESUMO
PURPOSE: Strenuous running triggers the coordination of pro- and anti-inflammatory, as well as immunoregulatory cytokines, which are upregulated in response to inflammatory stimulus and thus considered a precursor to overuse injury. The aim of this study was to correlate injury risk to footwear stiffness normalized against each runner's weight, i.e. the midsole's ability to resist deformation in response to the applied force. MATERIALS AND METHODS: Experienced runners participated in a 2h 15 âmin intensity-controlled run, averaging 85 â% of their threshold heart rate. Venous blood, collected in the field prior to and immediately after the race, was subjected to multi-parameter flow cytometry, to monitor the plasma levels of interleukin (IL)-2, IL-6 and tumor necrosis factor alpha (TNFα). Footwear stiffness was determined utilizing an automated drop test, recreating footfall pattern, impact speed and weight of each runner. Plasma level increase was analyzed for each cytokine, using one-way ANOVA and the data associated to footwear stiffness through the calculation of Pearson correlation coefficient. RESULTS: Only IL-6 levels exhibited a statistical significant increase pre-to post-race, corresponding to F (1,8) â= â24.0417 with a critical value of 4.4139. The increase in IL-6 levels was also found to produce a strong correlation to footwear stiffness, expressed in a Pearson coefficient of r (8) â= â0.79 âat ρ â= â0.0063 (P â< â0.05). CONCLUSION: The significant increase in pro-inflammatory markers, such as IL-6 which are associated with injury, would suggest that runners using compliant footwear are at lower risk of overuse injury than the ones running on stiffer midsoles.
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According to the speed-control hypothesis, the rate of force development (RFD) during ballistic contractions is dictated by force amplitude because time to peak force (TPF) remains constant regardless of changes in force amplitude. However, this hypothesis has not been tested at force levels below 20% of an individual's maximum voluntary contraction (MVC). Here, we examined the relationship between the RFD and force amplitude from 2 to 85% MVC and the underlying structure of muscle activity in 18 young adults. Participants exerted ballistic index finger abductions for 50 trials in each of seven randomly assigned force levels (2, 5, 15, 30, 50, 70, and 85% MVC). We quantified TPF, RFD, and various EMG burst characteristics. Contrary to the speed-control hypothesis, we found that TPF was not constant, but significantly varied from 2 to 85% MVC. Specifically, the RFD slope from 2 to 15% MVC was greater than the RFD slope from 30 to 85% MVC. Longer TPF at low force levels was associated with the variability of EMG burst duration, whereas longer TPF with higher force levels was associated with the EMG burst integral. Contrary to the speed-control hypothesis, we found that the regulation of TPF for low and high force levels was different, suggesting that neuronal variability is critical for force levels below 30% MVC and neuronal amplitude for force levels above 30% MVC. These findings present compelling new evidence highlighting the limitations of the speed-control hypothesis underscoring the need for a new theoretical framework.
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INTRODUCTION: Flexibility seems to be an essential part of both the training and rehabilitation processes. Several stretching techniques have been used to improve the range of motion (ROM) of the joints with the proprioceptive neuromuscular facilitation (PNF) method being the most effective one. Although plantar flexors are ideal to compare the acute effects of synergistic muscle groups on performance, it is not clear whether the PNF stretch at different muscle lengths could result in different alterations. MATERIAL AND METHODS: Sixteen male students randomly performed 2 levels of stretching (PNF with bended knees, or PNFshort, and with extended knee, or PNFlong) and 3 types of jumps, separated by 48 hours (7 sessions in total). Jumping parameters were recorded by a force plate, and the final jumping height (H) and ground reaction forces (Fz) were analyzed. Furthermore, the ROM of the ankle joint was recorded before, right after, and 15 minutes after the stretches. Results: The ankle joint's ROM joint was increased after both interventions. No significant changes were found in the jumping height of all jumps. The Fz, during the squat jump (SJ) and countermovement jump (CMJ), were increased after PNFshort. Similarly, a significant increase was found in Fz in drop jumps (DJ) right after the PNFshort. CONCLUSION: Our findings demonstrated that PNF stretches of different lengths could potentially alter the stretch-shortening cycle's performance, possibly leading to a non-optimal muscle-tendon interaction.
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The purpose of this study was to compare the effects of an Olympic weightlifting (OL) and traditional weight (TW) training program on muscle coactivation around the knee joint during vertical jump tests. Twenty-six men were assigned randomly to 3 groups: the OL (n = 9), the TW (n = 9), and Control (C) groups (n = 8). The experimental groups trained 3 d · wk(-1) for 8 weeks. Electromyographic (EMG) activity from the rectus femoris and biceps femoris, sagittal kinematics, vertical stiffness, maximum height, and power were collected during the squat jump, countermovement jump (CMJ), and drop jump (DJ), before and after training. Knee muscle coactivation index (CI) was calculated for different phases of each jump by dividing the antagonist EMG activity by the agonist. Analysis of variance showed that the CI recorded during the preactivation and eccentric phases of all the jumps increased in both training groups. The OL group showed a higher stiffness and jump height adaptation than the TW group did (p < 0.05). Further, the OL showed a decrease or maintenance of the CI recorded during the propulsion phase of the CMJ and DJs, which is in contrast to the increase in the CI observed after TW training (p < 0.05). The results indicated that the altered muscle activation patterns about the knee, coupled with changes of leg stiffness, differ between the 2 programs. The OL program improves jump performance via a constant CI, whereas the TW training caused an increased CI, probably to enhance joint stability.
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Adaptação Fisiológica/fisiologia , Desempenho Atlético/fisiologia , Joelho/fisiologia , Músculo Quadríceps/fisiologia , Levantamento de Peso/fisiologia , Adolescente , Atletas , Fenômenos Biomecânicos/fisiologia , Eletromiografia , Humanos , Masculino , Força Muscular/fisiologia , Adulto JovemRESUMO
BACKGROUND: Adolescent children experience a critical developmental period marked by rapid biological changes. Research question To describe the longitudinal changes in postural control that occur in adolescent boys and girls before the age of peak height velocity (PHV). METHODS: Here, to address the gap of knowledge, we compared the postural control and activation strategies of the muscles that control the ankle joint in twenty-three boys (age 12.5 ± 0.29) and twenty-one girls (age 10.5 ± 0.32). They performed easy (two legs) and difficult (two legs-eyes closed; one leg) postural balance tasks at 18 and 9 months before PHV and at PHV. We quantified the center of pressure (COP) displacements in the anterior-posterior (AP) and mediolateral (ML) directions and electromyographic (EMG) activity of tibialis anterior (TA) and medial gastrocnemius (MG) muscles. RESULTS: Boys exhibited greater AP and ML COP displacement than girls only for the one leg task (difficult task). Although boys and girls had similar postural control 18 months prior to PHV, girls exhibited lesser COP displacement at 9 months before PHV, which related to greater TA-MG coactivation (R2 = 0.26; p < 0.01). In contrast, postural control was not different between boys and girls with an easy balance task (two legs) performed with eyes open and closed. Rather, we found that all children improved their COP displacement in the ML direction with maturity and both AP and ML COP was significantly lower with eyes open. CONCLUSION: These findings provide novel evidence that postural control is superior in early adolescent girls than boys 9 months prior to PHV, likely associated with an earlier maturation of muscle coordination.
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Estatura , Equilíbrio Postural , Adolescente , Articulação do Tornozelo , Estatura/fisiologia , Criança , Feminino , Humanos , Masculino , Músculo Esquelético , Equilíbrio Postural/fisiologiaRESUMO
BACKGROUND: Several spine instrumentation techniques have been introduced to correct inter-segmental alignment, or provide long-term stability. Whilst pedicle screws are considered the intervention of reference, we hypothesize that the week hold of osteoporotic bone, might be a clinical indicator for an alternative surgical approach. METHODS: To put this to the test, a non-linear Finite Element model, of a ligamentous lumbosacral spine, was employed to examine a stabilization spanning over L3-L5. Two different immobilization techniques (a Pedicle Screw System and Laminar Hook Fusion) are compared as to their biomechanical response during 7.5 Nm flexion, lateral flexion and torsion, while considering a 280 N follower load. Fifteen analyses performed in total, simulating patients of healthy and osteoporotic Bone Mineral Density. FINDINGS: Range of Motion was significantly reduced after instrumentation for both implant systems. This trend was more pronounced in the Pedicle Screw models, which were stressed to a higher degree. To evaluate implant loosening risk, we introduce the consideration of strain energy patterns around the screw tract. The notably higher intensity of these, for the osteoporotic model, taken into consideration with the weaker strength of the tissue and inconsistencies in the stress allocation between implant and bone, affirmed an increased risk for loosening of the Pedicle Screws in osteoporotic patients. INTERPRETATION: The analysis provided refined insight as to the treatment of osteoporotic patients as well as to their postoperative care, as restriction of specific movements (e.g. through bracing), could significantly restrict the stress values in the bone-implant interface and thus, reduce implant failure.
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Parafusos Pediculares , Fusão Vertebral , Fenômenos Biomecânicos , Humanos , Vértebras Lombares/cirurgia , Amplitude de Movimento Articular/fisiologiaRESUMO
The purpose of the study was to assess the influence of short, intermediate, and long muscle lengths on dorsiflexor force steadiness and the discharge characteristics of motor units in tibialis anterior during submaximal isometric contractions. Steady contractions were performed at 5 target forces (5, 10, 20, 40, and 60% maximal voluntary contraction, MVC) for 3 ankle angles (75°, 90°, and 105°). MVC force was less (p = 0.043) at the smallest joint angle compared with the other two angles. The absolute (standard deviation) and normalised amplitudes (coefficient of variation) of the force fluctuations were similar for all 3 ankle angles at each target force. The coefficient of variation for force decreased progressively from 5% to 20% MVC force and then it plateaued at 40% and 60% MVC force. At all target forces, the mean discharge rate (MDR) of the motor units at 75° was greater than at 90° (p = 0.006) and 105° (p = 0.034). Moreover, the MDR was similar for 5% and 10% MVC forces and then increased gradually until 60% MVC force (p < 0.005). The variability in discharge times (coefficient of variation for interspike interval) and variability in neural drive (coefficient of variation of filtered cumulative spike train) were similar at all ankle angles. Variability in neural drive had a greater influence on force steadiness than did the variability in discharge times. Changes in ankle-joint angle did not influence either the normalised amplitude force fluctuations during steady submaximal contractions or the underlying modulation of the discharge characteristics of motor units in tibialis anterior.
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Contração Isométrica , Músculo Esquelético , Tornozelo/fisiologia , Articulação do Tornozelo/fisiologia , Eletromiografia , Humanos , Contração Isométrica/fisiologia , Fenômenos Mecânicos , Contração Muscular/fisiologia , Músculo Esquelético/fisiologiaRESUMO
An important but unresolved research question in adolescent children is the following: "Does sport participation interact with maturation to change motor control and the mechanical and morphological properties of tendons?" Here, we address this important research question with a longitudinal study around the age of peak height velocity (PHV). Our purpose was to characterize the interactive effects of maturation and sports participation on motor control and the mechanical and morphological properties of the Achilles tendon (AT) in adolescent athletes and non-athletes. Twenty-two adolescent athletes (13.1 ± 1.1 years) and 19 adolescent non-athletes (12.8 ± 1.1 years) volunteered for this study. We quantified motor control as the coefficient of variation of torque during a ramp task. In addition, we quantified the AT morphological and mechanical properties using ultrasonography from 18 months before to 12 months after PHV. We found that motor control improved with maturation in both athletes and non-athletes. We found that athletes have a greater increase in body mass with maturation that relates to greater plantarflexion peak force and AT peak stress. Also, athletes have a thicker and longer AT, as assessed with resting cross-sectional area and length. Although the rate of increase in the morphological change with maturation was similar for athletes and non-athletes, the rate of increase in normalized AT stiffness was greater for athletes. This increased AT stiffness in athletes related to peak force and stress. In summary, maturation improves motor control in adolescent children. Further, we provide novel longitudinal evidence that sport participation interacts with maturation in adolescents to induce adaptive effects on the Achilles tendon morphology and mechanical properties. These findings have the potential to minimize the risk of injuries and maximize athletic development in talented adolescents.
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The purpose of this study was to compare the effects of an Olympic weight lifting (OL), a plyometric (PL), and combined weight lifting + plyometric (WP) training program on vertical jump (VJ) biomechanics. Thirty-six men were assigned randomly to 4 groups: PL group (n = 9), OL group (n = 9), WP group (), and control (C) group (n = 8). The experimental groups trained 3 d.wk, for 8 weeks. Sagital kinematics, VJ height, power, and electromyographic (EMG) activity from rectus femoris (RF) and medial gastrocnemius (GAS) were collected during squat jumping and countermovement jumping (CMJ) before and after training. The results showed that all experimental groups improved VJ height (p < 0.05). The OL training improved power and muscle activation during the concentric phase of the CMJ while the subjects used a technique with wider hip and knee angles after training (p < 0.05). The PL group subjects did not change their CMJ technique although there was an increase in RF activation and a decrease of GAS activity after training (p < 0.05). The WP group displayed a decline in maximal hip angle and a lower activation during the CMJ after training (p < 0.05). These results indicate that all training programs are adequate for improving VJ performance. However, the mechanisms for these improvements differ between the 3 training protocols. Olympic weight lifting training might be more appropriate to achieve changes in VJ performance and power in the precompetition period of the training season. Emphasis on the PL exercises should be given when the competition period approaches, whereas the combination of OL and PL exercises may be used in the transition phases from precompetition to the competition period.
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Exercício Físico/fisiologia , Esforço Físico/fisiologia , Treinamento Resistido , Desempenho Atlético/fisiologia , Fenômenos Biomecânicos , Eletromiografia , Humanos , Masculino , Movimento/fisiologia , Músculo Esquelético/fisiologia , Levantamento de Peso/fisiologia , Adulto JovemRESUMO
Etiologic factors associated to running injuries are reviewed, with an emphasis on the transient shock waves experienced during foot strike. In these terms, impact mechanics are analyzed from both, a biomechanical and medical standpoint and evaluated with respect injury etiology, precursors and morbidity. The complex interaction of runner specific characteristics on the employed footwear system are examined, providing insight into footwear selection that could act as a preventive measure against non-acute trauma incidence. In conclusion, and despite the vast literature on running-related injury-risks, only few records could be identified to consider the effect of shoe cushioning and anthropometric data on injury prevalence. Based on this literature, we would stress the importance of such considerations in future studies aspiring to provide insight into running related injury etiology and prevention.
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BACKGROUND: Deficits in postural control and skill performance are important intrinsic fall risk factors. Thus, the purpose of this study was to investigate the impact of trampoline plyometrics on postural control, and jumping height in prepubertal children. METHODS: Twenty-two school children were assigned to either a trampoline group (TPLG, N.=12, 7 girls and 5 boys, age =9.30±0.55 years) or a control group (CG, N.=12, 8 girls and 4 boys, age =9.30±0.55 years). The TPLG participated in 4 weeks plyometric training on a mini-trampoline (3 times per week) integrated in their physical education lessons while the CG attended the standard physical education curriculum at school. Pre- and postintervention included the measurements of postural sway and maximum height in countermovement and drop jump. RESULTS: Postural sway decreased significantly (P<0.05) in normal quiet stance (NQS) for the TPLG but not for the CG. Statistically significant decreases in postural sway in the anteroposterior direction during one-leg stance (OLS) were found for the TPLG whereas postural sway was unchanged at both directions for control group. Furthermore, statistically significant improvements in jump height were found only for TPLG after training (P<0.05). CONCLUSIONS: Training on elastic surface could be incorporated into children's exercise programs aiming to enhance balance and lower-limb strength to reduce injury rates. For injury prevention during trampoline training, close supervision by experienced personnel is recommended.
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Adaptação Fisiológica , Exercício Pliométrico , Acidentes por Quedas , Aclimatação , Criança , Feminino , Humanos , Extremidade Inferior/fisiologia , Masculino , Movimento , Força Muscular , Educação Física e Treinamento , Equilíbrio PosturalRESUMO
The authors asked how sport expertise modulates visual field dependence and sensory reweighting for controlling posture. Experienced soccer athletes, ballet dancers, and nonathletes performed (a) a Rod and Frame test and (b) a 100-s bipedal stance task during which vision and proprioception were successively or concurrently disrupted in 20-s blocks. Postural adaptation was assessed in the mean center of pressure displacement, root mean square of center of pressure velocity and ankle muscles integrated electromyography activity. Soccer athletes were more field dependent than were nonathletes. During standing, dancers were more destabilized by vibration and required more time to reweigh sensory information compared with the other 2 groups. These findings reveal a sport skill-specific bias in the reweighing of sensory inputs for spatial orientation and postural control.
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Desempenho Atlético/fisiologia , Postura/fisiologia , Propriocepção/fisiologia , Sensação/fisiologia , Percepção Espacial/fisiologia , Adolescente , Adulto , Tornozelo/fisiologia , Atletas , Desempenho Atlético/psicologia , Dança/psicologia , Eletromiografia , Feminino , Humanos , Masculino , Orientação/fisiologia , Equilíbrio Postural/fisiologia , Caracteres Sexuais , Futebol/psicologia , Campos Visuais , Adulto JovemRESUMO
OBJECTIVE: During the last century, running shoes have been subject to drastic changes with incremental however improvements as to injury prevention. This may be, among others, due to the limited insight that experimental methodologies can provide on their 3D in situ response. The objective of this study was to demonstrate the effectiveness of finite element (FE) modelling techniques, in optimizing a midsole system as to the provided cushioning capacity. METHODS: A commercial running shoe was scanned by means of micro computed tomography and its gel-based midsole, reverse-engineered to a 200 µm accuracy. The resulting 3D model was subjected to biorealistic loading and boundary conditions, in terms of time-varying plantar pressure distribution and shoe-ground contact constraints. The mesh grid of the FE model was verified as to its conceptual soundness and validated against velocity-driven impact tests. Nonlinear material properties were assigned to all entities and the model subjected to a dynamic FE analysis. An optimization function (based on energy absorption criteria) was employed to determine the optimum gel volume and position, as to accommodate sequential cushioning in the rear-, mid-, and forefoot, of runner during stance phase. RESULTS: The in situ developing stress fields suggest that the shock dissipating properties of the midsole could be significantly improved. Altering the position of the gel pads and varying their volume led to different midsole responses that could be tuned more efficiently to the specific strike and pronation pattern. CONCLUSIONS: The results suggest that midsole design can be significantly improved through biorealistic FE modelling, thus providing a new platform for the conceptual redesign and/or optimization of modern footwear.
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The present study investigated how young and older individuals organize their posture in response to self-induced balance perturbations evoked by oscillatory single limb movements. Eleven old (70.1+/-4.3 years) and nine young (20.1+/-2.4 years) participants performed repeatedly for 5s hip flexion/extension movements using full range of motion and maximum velocity. Two-dimensional joint kinematics (sampling rate: 60Hz), center of pressure (CoP) and EMG activity of tibialis anterior (TA), medial gastrocnemius (MGAS) rectus femoris (RF) and, semitendinosus (ST) in the stance limb were recorded and analysed. Cross-correlation function (CCF) analysis was used to identify the degree of coupling between the swinging limb (SL), center of gravity (CoG) and CoP motions. Old adults significantly limited SL, CoG and CoP range of anterior/posterior (A/P) motion in response to the forceful leg swinging. In the stance limb, significantly lower levels of ankle muscle activity resulted in reduced hip and knee joint excursions and increased ankle instability. By contrast, young performers produced sufficient ankle muscle activity to stabilize the foot to the ground while progressively increasing joint range of motion from the ankle to the hip. Center of pressure and SL movements were strongly correlated in an anti-phase relationship in both age groups. In older adults, however, the relationship between CoG-SL and CoG-CoP movements was neither strong nor synchronous, reflecting a weaker coupling and lack of coordination between component movements. It is concluded that insufficient ankle muscle activity, central integration deficits and increased anxiety to postural threat are important factors implicated for the weaker postural synergies and freezing of degrees of freedom seen in the elderly during performance of single limb oscillations.
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Envelhecimento/fisiologia , Equilíbrio Postural , Postura , Adulto , Idoso , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Eletromiografia , Articulação do Quadril/fisiologia , Humanos , Articulação do Joelho/fisiologia , Movimento , Músculo Esquelético/fisiologiaRESUMO
The present study aimed to examine movement difficulties among typically developing 8- to 9-year-old elementary students in Greece and to investigate the possible effects of a balance training program to those children assessed with Developmental Coordination Disorder (DCD). The Body Coordination Test for Children (BCTC; Körperkoordinationstest fur Kinder, KTK, Kiphard & Schilling, 1974) was chosen for the purposes of this study and 20 children out of the total number of 200, exhibited motor difficulties indicating a probable DCD disorder. The 20 students diagnosed with DCD were equally separated into two groups where each individual of the experimental group was paired with an individual of the control group. The intervention group attended a 12-week balance training program while students of the second - control group followed the regular school schedule. All participants were tested prior to the start and after the end of the 12-week period by performing static balance control tasks while standing on an EPS pressure platform and structured observation of trampoline exercises while videotaping. The results indicated that after a 12-week balance training circuit including a trampoline station program, the intervention group improved both factors that were examined. In conclusion, balance training with the use of attractive equipment such as trampoline can be an effective intervention for improving functional outcomes and can be recommended as an alternative mode of physical activity.
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Terapia por Exercício/métodos , Transtornos das Habilidades Motoras/reabilitação , Equilíbrio Postural , Criança , Terapia por Exercício/instrumentação , Feminino , Humanos , Masculino , Programas de Rastreamento , Destreza Motora , Transtornos das Habilidades Motoras/diagnóstico , Resultado do TratamentoRESUMO
We examined how young and older adults adapt their posture to static balance tasks of increasing difficulty. Participants stood barefoot on a force platform in normal quiet, Romberg-sharpened and one-legged stance. Center of pressure (CoP) variations, electromyographic (EMG) activity of ankle and hip muscles and kinematic data were recorded. Both groups increased postural sway as a result of narrowing the base of support. Greater CoP excursions, EMG activity and joint displacements were noted in old compared to younger adults. Older adults displayed increased hip movement accompanied by higher hip EMG activity, whereas no similar increase was noted in the younger group. It is concluded that older adults rely more on their hip muscles when responding to self induced perturbations introduced by increased task constraints during quiet standing.
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Envelhecimento , Fenômenos Biomecânicos , Equilíbrio Postural/fisiologia , Postura/fisiologia , Adulto , Idoso , Tornozelo/fisiologia , Eletromiografia , Quadril/fisiologia , Humanos , Masculino , Músculo Esquelético/fisiologia , Propriocepção/fisiologiaRESUMO
Reaction time and muscle activation deficits might limit the individual's autonomy in activities of daily living and in participating in recreational activities. The aim of the present study was to assess the effects of a 14-week hippotherapy exercise program on movement reaction time and muscle activation in adolescents with intellectual disability (ID). Nineteen adolescents with moderate ID were assigned either to an experimental group (n=10) or a control group (n=9). The experimental group attended a hippotherapy exercise program, consisting of two 30-min sessions per week for 14 weeks. Reaction time, time of maximum muscle activity and electromyographic activity (EMG) of rectus femoris and biceps femoris when standing up from a chair under three conditions: in response to audio, visual and audio with closed eyes stimuli were measured. Analysis of variance designs showed that hippotherapy intervention program resulted in significant improvements in reaction time and a reduction in time to maximum muscle activity of the intervention group comparing to the control group in all 3 three conditions that were examined (p<0.05). The present findings suggest that the muscle reaction function of individuals with ID can be improved through hippotherapy training. Hippotherapy probably creates a changing environment with a variety of stimuli that enhance deep proprioception as well as other sensory inputs. In conclusion, this study provides evidence that hippotherapy can improve functional task performance by enhancing reaction time.
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Terapia Assistida por Cavalos/métodos , Cavalos , Deficiência Intelectual/fisiopatologia , Deficiência Intelectual/reabilitação , Destreza Motora/fisiologia , Adolescente , Animais , Braço/fisiologia , Eletromiografia , Humanos , Articulação do Joelho/fisiologia , Masculino , Contração Muscular/fisiologia , Tempo de Reação/fisiologia , Resultado do TratamentoRESUMO
The aim of this study was to assess the effects of a hippotherapy program on static balance and strength in adolescents with intellectual disability (ID). Nineteen adolescents with moderate ID were assigned either an experimental group (n=10) or a control group (n=9). The experimental group attended a 10-week hippotherapy program. To assess static balance, three tasks of increasing difficulty (Double-Leg Stance with opened or closed eyes, and One-Leg Stance with opened eyes) were performed while standing on an EPS pressure platform (Loran Engineering S.r.I., Bologna, Italy). The strength measurements consisted of three maximal isometric half-squats from the seating position (knee joint at 90°). The hippotherapy intervention program resulted in significant improvements in strength parameters, and on the more complex balance task (i.e. standing on one leg). In conclusion, this study provides evidence that hippotherapy can be used as an effective intervention for improving balance and strength in individuals with ID, and could thus influence functional activities and quality of life.