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1.
PLoS One ; 16(1): e0233243, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33493178

RESUMO

The full-body ownership illusion exploits multisensory perception to induce a feeling of ownership of an entire artificial body. Although previous research has shown that synchronous visuotactile stimulation of a single body part is sufficient for illusory ownership of the whole body, the effect of combining multisensory stimulation across multiple body parts remains unknown. Therefore, 48 healthy adults participated in a full-body ownership illusion with conditions involving synchronous (illusion) or asynchronous (control) visuotactile stimulation to one, two, or three body parts simultaneously (2×3 design). We used questionnaires to isolate illusory ownership of five specific body parts (left arm, right arm, trunk, left leg, right leg) from the full-body ownership experience and sought to test not only for increased ownership in synchronous versus asynchronous conditions but also for potentially varying degrees of full-body ownership illusion intensity related to the number of body parts stimulated. Illusory full-body ownership and all five body-part ownership ratings were significantly higher following synchronous stimulation than asynchronous stimulation (p-values < .01). Since non-stimulated body parts also received significantly increased ownership ratings following synchronous stimulation, the results are consistent with an illusion that engages the entire body. Furthermore, we noted that ownership ratings for right body parts (which were often but not always stimulated in this experiment) were significantly higher than ownership ratings for left body parts (which were never stimulated). Regarding the effect of stimulating multiple body parts simultaneously on explicit full-body ownership ratings, there was no evidence of a significant main effect of the number of stimulations (p = .850) or any significant interaction with stimulation synchronicity (p = .160), as assessed by linear mixed modelling. Instead, median ratings indicated a moderate affirmation (+1) of an illusory full-body sensation in all three synchronous conditions, a finding mirrored by comparable full-body illusion onset times. In sum, illusory full-body ownership appears to be an 'all-or-nothing' phenomenon and depends upon the synchronicity of visuotactile stimulation, irrespective of the number of stimulated body parts.


Assuntos
Imagem Corporal/psicologia , Ilusões/psicologia , Adolescente , Adulto , Braço/fisiologia , Feminino , Corpo Humano , Humanos , Perna (Membro)/fisiologia , Masculino , Pessoa de Meia-Idade , Propriedade , Percepção do Tato/fisiologia , Percepção Visual/fisiologia , Adulto Jovem
2.
Nat Commun ; 11(1): 5615, 2020 11 05.
Artigo em Inglês | MEDLINE | ID: mdl-33154381

RESUMO

Limb motion capture is essential in human motion-recognition, motor-function assessment and dexterous human-robot interaction for assistive robots. Due to highly dynamic nature of limb activities, conventional inertial methods of limb motion capture suffer from serious drift and instability problems. Here, a motion capture method with integral-free velocity detection is proposed and a wearable device is developed by incorporating micro tri-axis flow sensors with micro tri-axis inertial sensors. The device allows accurate measurement of three-dimensional motion velocity, acceleration, and attitude angle of human limbs in daily activities, strenuous, and prolonged exercises. Additionally, we verify an intra-limb coordination relationship exists between thigh and shank in human walking and running, and establish a neural network model for it. Using the intra-limb coordination model, dynamic motion capture of human lower limbs including thigh and shank is tactfully implemented by a single shank-worn device, which simplifies the capture device and reduces cost. Experiments in strenuous activities and long-time running validate excellent performance and robustness of the wearable device in dynamic motion recognition and reconstruction of human limbs.


Assuntos
Extremidades/fisiologia , Monitorização Fisiológica/instrumentação , Movimento (Física) , Dispositivos Eletrônicos Vestíveis , Fenômenos Biomecânicos , Desenho de Equipamento , Humanos , Perna (Membro)/fisiologia , Redes Neurais de Computação , Reprodutibilidade dos Testes , Coxa da Perna/fisiologia
3.
Artigo em Inglês | MEDLINE | ID: mdl-32933208

RESUMO

Backward jump-landing during sports performance will result in dynamic postural instability with a greater risk of injury, and most research studies have focused on forward landing. Differences in kinematic temporal characteristics between single-leg and double-leg backward jump-landing are seldom researched and understood. The purpose of this study was to compare and analyze lower extremity kinematic differences throughout the landing phases of forward and backward jumping using single-leg and double-leg landings (FS and BS, FD and BD). Kinematic data were collected during the landing phases of FS and BS, FD and BD in 45 participants. Through statistical parametric mapping (SPM) analysis, we found that the BS showed smaller hip and knee flexion and greater vertical ground reactive force (VGRF) than the FS during 0-37.42% (p = 0.031), 16.07-32.11% (p = 0.045), and 23.03-17.32% (p = 0.041) landing phases. The BD showed smaller hip and knee flexion than the FD during 0-20.66% (p = 0.047) and 0-100% (p < 0.001) landing phases. Most differences appeared within a time frame during the landing phase at 30-50 ms in which non-contact anterior cruciate ligament (ACL) injuries are thought to occur and are consistent with the identification of risk in biomechanical analysis. A landing strategy that consciously increases the knee and hip flexion angles during backward landing should be considered for people as a measure to avoid injury during the performance of this type of physical activity.


Assuntos
Lesões do Ligamento Cruzado Anterior , Desempenho Atlético/fisiologia , Traumatismos do Joelho/prevenção & controle , Perna (Membro)/fisiologia , Extremidade Inferior/fisiologia , Movimento/fisiologia , Equilíbrio Postural/fisiologia , Adulto , Atletas , Fenômenos Biomecânicos/fisiologia , Humanos , Articulação do Joelho/fisiologia
4.
Geriatr Gerontol Int ; 20(10): 943-950, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32886830

RESUMO

AIM: To re-evaluate the suitability of calf circumference as a surrogate marker of low muscle mass measured by both bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA). We also examined the effects of obesity and age on low muscle mass screening using calf circumference. METHODS: In total, 1239 adults participated in this cross-sectional study. We measured the maximum calf circumference in a standing position and appendicular skeletal muscle mass (ASM) using BIA and DXA. We defined low muscle mass based on the Asian Working Group for Sarcopenia 2019 consensus. RESULTS: Calf circumference was positively correlated with BIA-measured ASM/height2 (men: r = 0.81, women: r = 0.73) and DXA-measured ASM/height2 (men: r = 0.78, women: r = 0.76). In the subgroup analyses by obesity and age, calf circumference was also positively correlated with ASM/height2 . The optimal calf circumference cut-offs for low muscle mass screening measured by BIA and DXA were 35 cm (sensitivity 91%, specificity 84%) and 36 cm (sensitivity 82%, specificity 80%) for men, and 33 cm (sensitivity 82%, specificity 84%) and 34 cm (sensitivity 85%, specificity 72%) for women, respectively. CONCLUSIONS: Calf circumference is positively correlated with BIA- and DXA-measured muscle mass regardless of obesity and age and is a simple and accurate surrogate marker of muscle mass for diagnosing sarcopenia. Geriatr Gerontol Int 2020; 20: 943-950.


Assuntos
Perna (Membro)/fisiologia , Músculo Esquelético/fisiologia , Sarcopenia/diagnóstico , Absorciometria de Fóton , Adulto , Idoso , Idoso de 80 Anos ou mais , Composição Corporal , Índice de Massa Corporal , Estudos Transversais , Impedância Elétrica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Obesidade/fisiopatologia , Sensibilidade e Especificidade
5.
PLoS One ; 15(8): e0238197, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32841286

RESUMO

The aim of this study was to compare artistic swimmers (ASs) and water polo players (WPs) in their polyrhythmic production ability and entrainment between arm and leg motion frequency. Nine ASs and nine WPs participated in the study. First, we assessed the natural eggbeater kick frequency of each participant without any additional motion for 20 s. We then required the participants to perform a circular arm movement in synchronization with two sequences of metronome rhythms (either 100%, 80% and 120% or100%, 120% and 80% of their natural eggbeater kick frequency) while maintaining their natural eggbeater kick frequency. All tasks were repeated three times. The participants' performances were recorded by a motion capture system synchronized with the metronome. A two-way mixed-design ANOVA was performed on the coefficient of variation of natural eggbeater kick frequency obtained from the first task to confirm the consistency of participants' kicking motion. In the second task, a three-way mixed-design ANOVA was performed on the average frequency of the arm and leg motions to assess the entrainment between the two. In the first task, there were no significant main effects and interaction between group and trial in the coefficient of variation of eggbeater kick frequency, suggesting that both WPs and ASs maintained their natural eggbeater kick frequency equally consistently. In the second task, however, WPs were not able to maintain their natural eggbeater kick frequency when they were required to do circular arm movements at 120% tempo (p < .01). On the other hand, ASs successfully maintained their natural eggbeater kick frequency with all metronome rhythms, suggesting that they have a better polyrhythmic production ability than WPs.


Assuntos
Música , Natação/fisiologia , Esportes Aquáticos/fisiologia , Adolescente , Adulto , Braço/fisiologia , Desempenho Atlético/fisiologia , Fenômenos Biomecânicos , Feminino , Humanos , Perna (Membro)/fisiologia , Masculino , Destreza Motora/fisiologia , Movimento/fisiologia , Amplitude de Movimento Articular/fisiologia , Adulto Jovem
6.
Clin Interv Aging ; 15: 1045-1056, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32636619

RESUMO

Aim: This study aimed to determine the association of handgrip strength with isometric and isokinetic strength (hip, knee and ankle extensor/flexor muscles), and functional capacity in older women. Methods: The handgrip strength and lower limb strength of 199 older women (60-86 years) were measured using JAMAR and BIODEX dynamometers, respectively. Time Up and Go, Five-times-sit-to-stand and 6m-walk functional tests were evaluated. Pearson correlations were used to determine the relationship between variables. Regression analysis was applied to identify if HS was able to predict TUG performance. The effect of age was analyzed by splitting the participants in a group of older women (OLD; from 60 to 70 years old) and very old women (from 71 to 86 years old). Results: The HS and isometric/isokinetic strength correlations were negligible/low and, in most cases, were non-significant. The correlation between handgrip strength and functional tests also ranged predominantly from negligible (r=0.0 to 0.3) to low (r=0.3 to 0.5), irrespective of the group age. The handgrip strength was not able to explain the variance of the TUG performance. Conclusion: Generalizing handgrip strength as a practical and straightforward measure to determine lower limbs and overall strength, and functional capacity in older women must be viewed with caution. Handgrip strength and standard strength measures of the lower limbs and functional tests present a negligible/low correlation.


Assuntos
Força da Mão/fisiologia , Perna (Membro)/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Desempenho Físico Funcional , Idoso , Idoso de 80 Anos ou mais , Feminino , Avaliação Geriátrica/métodos , Humanos , Articulação do Joelho/fisiologia , Caminhada/fisiologia
7.
PLoS One ; 15(7): e0235686, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32658907

RESUMO

Previous research found that below-knee prosthesis users proactively increase their lateral margin-of-stability on their impaired side in anticipation of an impending perturbation when the timing is predictable and potentially directed toward the impaired limb. While knowledge of perturbation timing and direction influences proactive strategies, the consequences of such knowledge and anticipatory behavior on recovery from perturbations is unclear. This study characterized center-of-mass (CoM) dynamics of below-knee prosthesis users and non-impaired controls following a lateral perturbation when the perturbation direction is known but a priori knowledge of the timing of perturbation is either known or unknown. Across groups, CoM displacement during perturbation exposure increased when directed towards the impaired or non-dominant limb with no influence of timing knowledge. In addition, peak CoM displacement was less with known timing irrespective of the perturbation direction. Generally, the CoM displacement during perturbation exposure correlated well with the CoM medial-lateral velocity during unperturbed walking, supporting evidence that human response dynamics to lateral perturbations are influenced by the instantaneous state of the body's momentum.


Assuntos
Membros Artificiais/psicologia , Equilíbrio Postural , Caminhada/fisiologia , Adulto , Fenômenos Biomecânicos , Estudos de Casos e Controles , Feminino , Humanos , Perna (Membro)/fisiologia , Masculino , Adulto Jovem
8.
J Sports Med Phys Fitness ; 60(7): 992-998, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32597616

RESUMO

BACKGROUND: The rest interval between sets can affect the responses to resistance training. Thus, the purpose of this study was to compare the effects of different rest intervals (RI) on volume, density, and rating of perceived exertion (RPE) when adopting a crescent pyramid (CP) system. METHODS: Twenty young women (21.1±2.6 years, 1.59±0.06 m, 58.5±9.3 kg) participated in this study. All participants performed three experimental sessions of the leg press exercise in 5 sets until voluntary muscular failure at 60%, 65%, 70%, 75%, and 80% of one-repetition maximum (1RM). A randomized and crossover design was used so that in each session one of three RI (RI-1 = 1 min, RI-2 = 2 min, and RI-3 = 3 min) was tested. RESULTS: The participants performed a significantly larger volume in the RI-3 (12820±3134 kg) when compared to RI-1 (10367±3053 kg) condition (P<0.05). The volume did not differ between RI-2 and RI-3 (P>0.05). The density was higher (P<0.05) in RI-1 (43.1±12.7 kg/s) when compared RI-2 (25.6±5.8 kg/s) and RI-3 (17.7±4.3 kg/s). The RI-2 presented higher density compared to RI-3 condition (P<0.05). The RPE was not different between the three conditions (P>0.05). CONCLUSIONS: The use of 2 minutes of rest between sets allowed the performance of a high volume-load and density of the session in young women. In addition, the three experimental sessions provided a high perception of effort.


Assuntos
Percepção/fisiologia , Esforço Físico/fisiologia , Treinamento de Resistência/métodos , Levantamento de Peso/fisiologia , Adulto , Estudos Cross-Over , Feminino , Humanos , Perna (Membro)/fisiologia , Descanso/fisiologia , Fatores de Tempo , Adulto Jovem
9.
Int J Sports Med ; 41(11): 744-750, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32492732

RESUMO

Sprinting in curvilinear trajectories is an important soccer ability, corresponding to ~85% of the actions performed at maximum velocity in a soccer league. We compared the neuromuscular behavior and foot contact-time between outside leg and inside leg during curve sprinting to both sides in soccer players. Nine soccer players (age=23±4.12 years) performed: 3×Sprint linear, 3×Sprint right curve, and 3×Sprint left curve. An ANOVA with repeated measures was used to compare the differences between inside and outside leg, and Cohen's d was used to calculate the effect-size. Considering the average data, the performance classification (from best to worst) was as follows: 1. Curve "good" side (2.45±0.11 s), 2. Linear (2.47±0.13 s), and 3. Curve "weak" side (2.56±0.17 s). Comparing linear with curve sprinting, inside leg recorded significant differences ("good" and "weak"; effect size=1.20 and 2, respectively); in contrast, for outside leg, there were no significant differences ("good" and "weak"; effect size=0.30 and 0.49, respectively). Electromyography activity showed significant differences (p≤0.05) during curve sprinting between outside (higher in biceps femoris and gluteus medius) and inside leg (higher activity in semitendinosus and adductor). In summary, inside and outside leg play different roles during curved sprints, but inside leg is more affected by the change from straight to curve sprint.


Assuntos
Perna (Membro)/fisiologia , Destreza Motora/fisiologia , Músculo Esquelético/fisiologia , Corrida/fisiologia , Futebol/fisiologia , Fenômenos Biomecânicos , Eletromiografia , Teste de Esforço , Pé/fisiologia , Humanos , Estudos de Tempo e Movimento
10.
J Sports Sci ; 38(19): 2236-2241, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32552333

RESUMO

Surface compliance has been shown to affect leg stiffness and energetics. It is unknown if compliance differences between common treadmills would elicit such changes. Therefore, the purpose of this study was to determine if compliance design differences of common treadmills would affect the mechanics and energetics of running. Eleven runners ran at moderate, self-selected, matched belt speeds for three minutes on two treadmills: compliant (CT) and rigid (RT) decks. During the last minute of each trial, oxygen consumption and six markers describing the torso, thigh, shank and foot, and one marker to determine treadmill deflection were recorded. Leg stiffness, continuous relative phase (CRP) and CRP variability were calculated. Compared to RT, running on CT resulted in a significantly more compliant leg (8.591 kN•m-1 > 9.063 kN•m-1), lower oxygen consumption (34.69 ml•kg-1•min-1 < 36.86 ml•kg-1•min-1), different coordination patterns and greater variability, particularly during the push-off phase. These results are inconsistent with the literature because the deck of CT rebounds back at the runner during the absorption phase and away from the runner during the push-off phase. Therefore, care should be taken when using treadmills for research and comparing mechanical and energetic measures between studies.


Assuntos
Desenho de Equipamento , Perna (Membro)/fisiologia , Corrida/fisiologia , Equipamentos Esportivos , Adulto , Fenômenos Biomecânicos , Metabolismo Energético , Feminino , Humanos , Masculino , Consumo de Oxigênio , Propriedades de Superfície
11.
J Sports Sci ; 38(18): 2127-2148, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32552520

RESUMO

Cross-country skiing is a complex endurance sport requiring technical skills, in addition to considerable physiological and tactical abilities. This review aims to identify biomechanical factors that influence the performance of cross-country skiers. Four electronic databases were searched systematically for original articles in peer-reviewed journals addressing the relationship between biomechanical factors (including kinematics, kinetics, and muscle activation) and performance while skiing on snow or roller skiing. Of the 46 articles included, 22 focused exclusively on the classical technique, 18 on the skating technique, and six on both. The indicators of performance were: results from actual or simulated races (9 articles); speed on specific tracts (6 articles); maximal or peak speed (11 articles); skiing economy or efficiency (11 articles); and grouping on the basis of performance or level of skill (12 articles). The main findings were that i) cycle length, most often considered as a major determinant of skiing speed, is also related to skiing economy and level of performance; ii) higher cycle rate related with maximal speed capacity, while self-selected cycle rate improves skiing economy at sub-maximal speeds; iii) cross-country skiing performance appears to be improved by joint, whole-body, ski, and pole kinematics that promote forward propulsion while minimizing unnecessary movement.


Assuntos
Desempenho Atlético/fisiologia , Destreza Motora/fisiologia , Esqui/fisiologia , Aceleração , Braço/fisiologia , Fenômenos Biomecânicos , Humanos , Cinética , Perna (Membro)/fisiologia , Músculo Esquelético/fisiologia , Equipamentos Esportivos
12.
Int J Sports Med ; 41(11): 776-782, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32485777

RESUMO

This study determined the effect of divided attention on controlling postural stability during a drop vertical jump task. In total, 30 participants were tested for drop vertical jumps from a 30-cm high platform and landing on a single leg with or without divided attention tasks. Three-dimensional marker trajectories and ground reaction forces were collected simultaneously. Vertical ground reaction force, loading rate, and dynamic postural stability index were analyzed with or without divided attention tasks. The paired sample t test indicated a significantly low knee flexion angle, high vertical ground reaction force, and increased loading rate in the divided attention task. Moreover, participants showed an increased vertical stability index and dynamic postural stability index in the divided attention task than in the nondivided attention task. Thus, results demonstrated that the divided attention task could affect posture control, leading to poor dynamic posture stability and possibly increasing lower extremity injury risk. The influence of the divided attention task on movement quality likely indicates that an athlete can no longer focus his attention on the bounce drop jump maneuver. Therefore, the bounce drop jump combined with dynamic postural stability index could be used in posture stability screening.


Assuntos
Atenção/fisiologia , Exercício Pliométrico/psicologia , Equilíbrio Postural , Fenômenos Biomecânicos , Cognição/fisiologia , Humanos , Joelho/fisiologia , Perna (Membro)/fisiologia , Movimento/fisiologia , Análise e Desempenho de Tarefas
13.
Am J Physiol Regul Integr Comp Physiol ; 319(1): R50-R58, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32432913

RESUMO

The current study explored whether the marked hypertrophic response noted with a short-term unilateral concurrent exercise paradigm was associated with more prominent changes in myonuclei accretion, ribosome biogenesis, and capillarization compared with resistance exercise alone (RE). Ten men (age 25 ± 4 yr) performed aerobic and resistance exercise (AE + RE) for one leg while the other leg did RE. Muscle biopsies were obtained before and after 5 wk of training and subjected to fiber-type specific immunohistochemical analysis, and quantification of total RNA content and mRNA/rRNA transcript abundance. Type II fiber cross-sectional area (CSA) increased with both AE + RE (22%) and RE (16%), while type I fiber CSA increased mainly with AE + RE (16%). The change score tended to differ between legs for type I CSA (P = 0.099), and the increase in smallest fiber diameter was greater in AE + RE than RE (P = 0.029). The number of nuclei per fiber increased after AE + RE in both fiber types, and this increase was greater (P = 0.027) than after RE. A strong correlation was observed between changes in number of nuclei per fiber and fiber CSA in both fiber types, for both AE + RE and RE (r > 0.8, P < 0.004). RNA content increased after AE + RE (24%, P = 0.019), but the change-scores did not differ across legs. The capillary variables generally increased in both fiber types, with no difference across legs. In conclusion, the accentuated hypertrophic response to AE + RE was associated with more pronounced myonuclear accretion, which was strongly correlated with the degree of fiber hypertrophy. This suggests that myonuclear accretion could play a role in facilitating muscle hypertrophy also during very short training periods.


Assuntos
Núcleo Celular/metabolismo , Exercício Físico/fisiologia , Músculo Esquelético/fisiologia , Adulto , Capilares/fisiologia , Humanos , Hipertrofia , Perna (Membro)/anatomia & histologia , Perna (Membro)/fisiologia , Imagem por Ressonância Magnética , Masculino , Fibras Musculares de Contração Rápida/fisiologia , Fibras Musculares de Contração Rápida/ultraestrutura , Fibras Musculares de Contração Lenta/fisiologia , Fibras Musculares de Contração Lenta/ultraestrutura , Músculo Esquelético/crescimento & desenvolvimento , Músculo Esquelético/ultraestrutura , Resistência Física , RNA/biossíntese , Treinamento de Resistência , Ribossomos/metabolismo , Adulto Jovem
14.
Hum Mov Sci ; 71: 102611, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32452428

RESUMO

During walking older adults' gait is slower, they take shorter steps, and rely less on ankle and more on knee and hip joint moments and powers compared to young adults. Previous studies have suggested that walking speed and step length are confounds that affect joint moments and powers. Our purpose was to examine the effects of walking speed and step length manipulation on net joint moments and powers in young and older adults. Sixteen young and 18 older adults completed walking trials at three speeds under three step length conditions as marker position and force platform data were captured synchronously. Net joint moments were quantified using inverse dynamics and were subsequently used to compute net joint powers. Average extensor moments at each joint during the stance phase were then computed. Older adults displayed greater knee extensor moment compared to young adults. Older adults showed trends (p < .10) of having lower ankle and higher hip moments, but these differences were not statistically significant. Average ankle, knee, and hip extensor moments increased with speed and step length. At the fast speed, older compared to young adults generated lower average ankle power (p = .003) and showed a trend (p = .056) of exerting less average moment at the ankle joint. Age-associated distal-to-proximal redistribution of net joint moments was diminished and not statistically significant when the confounding effects of walking speed and relative step length were controlled. These findings imply that age-related distal-to-proximal redistribution of joint moments may influence the different speeds and step lengths chosen by young and older adults.


Assuntos
Fatores Etários , Marcha , Perna (Membro)/fisiologia , Velocidade de Caminhada , Adulto , Idoso , Tornozelo , Articulação do Tornozelo , Fenômenos Biomecânicos , Feminino , Articulação do Quadril , Humanos , Joelho , Articulação do Joelho , Masculino , Adulto Jovem
15.
Hum Mov Sci ; 71: 102614, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32452431

RESUMO

Age-induced decline in the ability to perform daily activities is associated with a deterioration of physical parameters. Changes occur in neuromuscular system with age; however, the relationship between these changes and physical parameters has not been fully elucidated. Therefore, in this study, we aimed to determine the relationship between neuromuscular system evaluated using a coherence analysis of the leg muscles and physical parameters in community-dwelling healthy elderly adults. The participants were required to stand still in bipedal and unipedal stances on a force plate. Then, electromyography (EMG) was recorded from the tibialis anterior (TA) and medial and lateral gastrocnemius (MG/LG) muscles, and intermuscular coherence was calculated between the following pairs: TA and MG (TA-MG), TA and LG (TA-LG), and MG and LG (MG-LG). Furthermore, gait speed, unipedal stance time, and muscle mass were measured. EMG-EMG coherence for the MG-LG pair was significantly greater in the unipedal stance task than in the bipedal one (p = .001). Multiple linear regression analysis revealed that the muscle mass of the leg was negatively correlated with the change in the ß-band coherence for the MG-LG pair from bipedal to unipedal stance (R2 = 0.067, standard ß = -0.345, p = .044). As the ß-band coherence could reflect the corticospinal activity, the increased ß-band coherence may be a compensation for the smaller muscle mass, or alternatively may be a sign of changes in the nervous system resulting in the loss of muscle mass.


Assuntos
Eletromiografia , Perna (Membro)/fisiologia , Músculo Esquelético/fisiologia , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Análise de Regressão , Posição Ortostática , Velocidade de Caminhada
16.
Hum Mov Sci ; 71: 102623, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32452440

RESUMO

Following total knee replacement (TKR), patients often persist in maladaptive motor behavior which they developed before surgery to cope with symptoms of osteoarthritis. An important challenge in physical therapy is to detect, recognize and change such undesired movement behavior. The goal of this study was to measure the differences in clinical status of patients pre-TKR and post-TKR and to investigate if differences in clinical status were accompanied by differences in the patients'' motor flexibility. Eleven TKR participants were measured twice: pre-TKR and post-TKR (twenty weeks after TKR). In order to infer maladaptation, the pre-TKR and post-TKR measurements of the patient group were separately compared to one measurement in a control group of fourteen healthy individuals. Clinical status was measured with the Visual Analogue Scale (VAS) for pain and knee stiffness and the Knee Injury and Osteoarthritis Outcome Score (KOOS). Furthermore, Lower-limb motor flexibility was assessed by means of a treadmill walking task and a leg-amplitude differentiation task (LAD-task) supported by haptic or visual feedback. Motor flexibility was measured by coordination variability (standard deviation (SD) of relative phase between the legs) and temporal variability (sample entropy) of both leg movements. In the TKR-group, the VAS-pain and VAS- stiffness and the subscales of the KOOS significantly decreased after TKR. In treadmill walking, lower-limb motor flexibility did not significantly change after TKR. Between-leg coordination variability was significantly lower post-TKR compared to controls. In the LAD-task, a significant decrease of between-leg coordination variability between pre-TKR and post-TKR was accompanied by a significant increase in temporal variability. Post-TKR-values of lower-limb flexibility approached the values of the control group. The results demonstrate that a clinically relevant change in clinical status, twenty weeks after TKR, is not accompanied by alterations in lower-limb motor flexibility during treadmill walking but is accompanied by changes in motor flexibility towards the level of healthy controls during a LAD-task with visual and haptic feedback. Challenging patients with non-preferred movements such as amplitude differentiation may be a promising tool in clinical assessment of motor flexibility following TKR.


Assuntos
Artroplastia do Joelho , Retroalimentação Sensorial , Joelho/cirurgia , Perna (Membro)/fisiologia , Movimento , Osteoartrite do Joelho/cirurgia , Adulto , Idoso , Teste de Esforço , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dor , Período Pós-Operatório , Resultado do Tratamento , Caminhada
17.
Artigo em Inglês | MEDLINE | ID: mdl-32456048

RESUMO

BACKGROUND: This study aimed to compare the effects of plyometric and ankle stability exercises on the dynamic balance and lower limb kinematic and kinetic parameters of Taekwondo demonstration athletes with functional ankle instability. METHODS: Fourteen subjects participated in this study and were randomly divided into two groups: a plyometric exercise group (n = 7) and an ankle stability exercise group (n = 7). Exercises were performed twice a week for 8 weeks. A Y-balance test was used to measure dynamic balance, and a motion analysis system and force plate were used to collect kinematic and kinetic parameters during single-leg drop landing. A paired t-test was used for intragroup comparisons, and an independent t-test was used for intergroup comparisons. RESULTS: In both groups, exercise increased dynamic balance and shock absorption and reduced postural sway on the anteroposterior displacement (p < 0.05). The plyometric exercise group decreased their ankle dorsiflexion and increased their knee and hip joint flexion at maximum knee flexion (p < 0.05). In contrast, the stability exercise increased their ankle plantar flexion at initial contact (p < 0.05). CONCLUSIONS: The plyometric exercise group altered their landing strategies using their knee and hip joints to control ankle instability at landing. This study suggests that the application of plyometric exercises in ankle rehabilitation would improve stability and shock absorption and help prevent injuries during Taekwondo demonstrations.


Assuntos
Instabilidade Articular , Perna (Membro) , Exercício Pliométrico , Tornozelo , Atletas , Humanos , Perna (Membro)/fisiologia , Adulto Jovem
18.
Brain Stimul ; 13(3): 900-907, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32289723

RESUMO

BACKGROUND: Transcranial magnetic stimulation (TMS) is a rapidly expanding technology utilized in research and neuropsychiatric treatments. Yet, conventional TMS configurations affect primarily neurons that are aligned parallel to the induced electric field by a fixed coil, making the activation orientation-specific. A novel method termed rotational field TMS (rfTMS), where two orthogonal coils are operated with a 90° phase shift, produces rotation of the electric field vector over almost a complete cycle, and may stimulate larger portion of the neuronal population within a given brain area. OBJECTIVE: To compare the physiological effects of rfTMS and conventional unidirectional TMS (udTMS) in the motor cortex. METHODS: Hand and leg resting motor thresholds (rMT), and motor evoked potential (MEP) amplitudes and latencies (at 120% of rMT), were measured using a dual-coil array based on the H7-coil, in 8 healthy volunteers following stimulation at different orientations of either udTMS or rfTMS. RESULTS: For both target areas rfTMS produced significantly lower rMTs and much higher MEPs than those induced by udTMS, for comparable induced electric field amplitude. Both hand and leg rMTs were orientation-dependent. CONCLUSIONS: rfTMS induces stronger physiologic effects in targeted brain regions at significantly lower intensities. Importantly, given the activation of a much larger population of neurons within a certain brain area, repeated application of rfTMS may induce different neuroplastic effects in neural networks, opening novel research and clinical opportunities.


Assuntos
Potencial Evocado Motor/fisiologia , Mãos/fisiologia , Perna (Membro)/fisiologia , Córtex Motor/fisiologia , Estimulação Magnética Transcraniana/métodos , Adulto , Eletromiografia/métodos , Feminino , Mãos/inervação , Humanos , Perna (Membro)/inervação , Masculino
19.
J Sports Sci ; 38(14): 1605-1614, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32286154

RESUMO

This study investigated the between-limb asymmetry in kinetic and temporal characteristics during bilateral plyometric drop jumps from different heights. Seventeen male basketball players performed drop jumps from 3 heights on two platforms in randomized orders. Vertical ground reaction force data were analysed with respect to the lead limb (i.e. the limb stepping off the raised platform first) and trail limb. Peak forces and loading rates of each limb were calculated. The absolute time differential between the two limbs at initial ground contact and takeoff were determined. The frequency of symmetrical landing and taking off with "both limbs together" were counted using 3 time windows. Results showed that the lead limb displayed higher peak forces and loading rates than the trail limb across all heights (p <.05). As drop height increased, the absolute time differentials decreased at initial ground contact (p <.001) but increased at takeoff (p =.035). The greater the preset time window, the more landings and takeoffs were classified as bilaterally symmetrical. In conclusion, higher drop heights allowed subjects to become more bilaterally symmetrical in the timing of landing but this reduction in temporal asymmetry did not accompany with any reduction in kinetic asymmetry.


Assuntos
Perna (Membro)/fisiologia , Exercício Pliométrico , Adulto , Fenômenos Biomecânicos , Humanos , Cinética , Masculino , Análise e Desempenho de Tarefas , Fatores de Tempo , Adulto Jovem
20.
Sci Rep ; 10(1): 6342, 2020 04 14.
Artigo em Inglês | MEDLINE | ID: mdl-32286372

RESUMO

Impairments in oxygen delivery and consumption can lead to reduced muscle endurance and physical disability. Perfusion, a measure of microvascular blood flow, provides information on nutrient delivery. T2* provides information about relative tissue oxygenation. Changes in these parameters following stress, such as exercise, can yield important information about imbalance between delivery and consumption. In this study, we implemented novel golden angle radial MRI acquisition technique to simultaneously quantify muscle perfusion and T2* at 7T with improved temporal resolution, and demonstrated assessment of spatial and temporal changes in these parameters within calf muscles during recovery from plantar flexion exercise. Nine healthy subjects participated the studies. At rest, perfusion and T2* in gastrocnemius muscle group within calf muscle were 5 ± 2 mL/100 g/min and 21.1 ± 3 ms respectively. Then the subjects performed plantar flexion exercise producing a torque of ~8ft-lb. Immediately after the exercise, perfusion was elevated to 79.3 ± 9 mL/100 g/min and T2* was decreased by 6 ± 3%. The time constants for 50% perfusion and T2* recovery were 54.1 ± 10 s and 68.5 ± 7 s respectively. These results demonstrate successful simultaneous quantification of perfusion and T2* in skeletal muscle using the developed technique.


Assuntos
Exercício Físico , Músculo Esquelético/fisiologia , Consumo de Oxigênio , Fluxo Sanguíneo Regional , Adolescente , Adulto , Feminino , Humanos , Perna (Membro)/fisiologia , Imagem por Ressonância Magnética , Masculino , Contração Muscular , Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/diagnóstico por imagem
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