RESUMO
The purpose of this study was to investigate the effects of different vertical positions of an asymmetrical load on the anticipatory postural adjustments phase of gait initiation. Sixty-eight college students (32 males, 36 females; age: 23.65 ± 3.21 years old; weight: 69.98 ± 8.15 kg; height: 1.74 ± 0.08 m) were enrolled in the study. Ground reaction forces and moments were collected using two force platforms. The participants completed three trials under each of the following random conditions: no-load (NL), waist uniformly distributed load (WUD), shoulder uniformly distributed load (SUD), waist stance foot load (WST), shoulder stance foot load (SST), waist swing foot load (WSW), and shoulder swing foot load (SSW). The paired Hotelling's T-square test was used to compare the experimental conditions. The center of pressure (COP) time series were significantly different for the SUD vs. NL, SST vs. NL, WST vs. NL, and WSW vs. NL comparisons. Significant differences in COP time series were observed for all comparisons between waist vs. shoulder conditions. Overall, these differences were greater when the load was positioned at the shoulders. For the center of mass (COM) time series, significant differences were found for the WUD vs. NL and WSW vs. NL conditions. However, no differences were observed with the load positioned at the shoulders. In conclusion, only asymmetrical loading at the waist produced significant differences, and the higher the extra load, the greater the effects on COP behavior. By contrast, only minor changes were observed in COM behavior, suggesting that the changes in COP (the controller) behavior are adjustments to maintain the COM (controlled object) unaltered.
Assuntos
Marcha/fisiologia , Pressão , Estatística como Assunto , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Suporte de Carga , Adulto JovemRESUMO
Gait initiation is the task commonly used to investigate the anticipatory postural adjustments necessary to begin a new gait cycle from the standing position. In this study, we analyzed whether and how foot-floor interface characteristics influence the gait initiation process. For this purpose, 25 undergraduate students were evaluated while performing a gait initiation task in three experimental conditions: barefoot on a hard surface (barefoot condition), barefoot on a soft surface (foam condition), and shod on a hard surface (shod condition). Two force plates were used to acquire ground reaction forces and moments for each foot separately. A statistical parametric mapping (SPM) analysis was performed in COP time series. We compared the anterior-posterior (AP) and medial-lateral (ML) resultant center of pressure (COP) paths and average velocities, the force peaks under the right and left foot, and the COP integral x force impulse for three different phases: the anticipatory postural adjustment (APA) phase (Phase 1), the swing-foot unloading phase (Phase 2), and the support-foot unloading phase (Phase 3). In Phase 1, significantly smaller ML COP paths and velocities were found for the shod condition compared to the barefoot and foam conditions. Significantly smaller ML COP paths were also found in Phase 2 for the shod condition compared to the barefoot and foam conditions. In Phase 3, increased AP COP velocities were found for the shod condition compared to the barefoot and foam conditions. SPM analysis revealed significant differences for vector COP time series in the shod condition compared to the barefoot and foam conditions. The foam condition limited the impulse-generating capacity of COP shift and produced smaller ML force peaks, resulting in limitations to body-weight transfer from the swing to the support foot. The results suggest that footwear and a soft surface affect COP and impose certain features of gait initiation, especially in the ML direction of Phase 1.
Assuntos
Pé/fisiologia , Marcha/fisiologia , Sapatos/classificação , Adolescente , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Pressão , Estudantes , Adulto JovemRESUMO
Hiking is a demanding form of exercise that may cause delayed responses of the postural muscles and a loss of somatosensory information, particularly when repeatedly performed for several days. These effects may negatively influence the postural control of hikers. Therefore, the aim of this study was to investigate the effects of a four-day hike on postural control. Twenty-six adults of both sexes travelled 262 kilometers, stopping for lunch and resting in the early evening each day. Force platforms were used to collect center of pressure (COP) data at 100 Hz for 70 seconds before hiking started and immediately after arriving at the rest station each day. The COP time course data were analyzed according to global stabilometric descriptors, spectral analysis and structural descriptors using sway density curve (SDC) and stabilometric diffusion analysis (SDA). Significant increases were found for global variables in both the anterior-posterior and medial-lateral directions (COP sway area, COP total sway path, COP mean velocity, COP root mean square value and COP range). In the spectral analysis, only the 80% power frequency (F80) in the anterior-posterior direction showed a significant increase, reflecting the increase of the sway frequencies. The SDC revealed a significant increase in the mean distance between peaks (MD) and a significant decrease in the mean peak amplitudes (MP), suggesting that a larger torque amplitude is required for stabilization and that the postural stability is reduced. The SDA revealed a decrease in the long-term slope (Hl) and increases in the short-term (Ks) and the long-term (Kl) intercepts. We considered the likelihood that the presence of local and general fatigue, pain and related neuromuscular adaptations and somatosensory deficits may have contributed to these postural responses. Together, these results demonstrated that four days of hiking increased sway frequencies and deteriorated postural control in the standing position.
Assuntos
Equilíbrio Postural , Caminhada/fisiologia , Adulto , Fadiga/fisiopatologia , Feminino , Humanos , Masculino , Dor/fisiopatologia , Fatores de TempoRESUMO
BACKGROUND: Static footprints have been widely used clinically. However, since this measure provides only indirect information about the medial longitudinal arch height, it is not clear if it can be indicative of dynamic foot function especially in obese children. This study aimed to verify whether static footprints can predict dynamic plantar pressures in obese children. MATERIALS AND METHODS: Twenty children aged 9 to 11 years, divided into obese and non obese, voluntarily participated in this study. Static footprints and dynamic plantar pressures were analyzed by using a pedograph and the Pedar system (Novel GMbH, Munich, GER), respectively. RESULTS: In general, correlations between static and dynamic measures were observed to be significant for the non obese children, while no significant correlations were found for the obese ones. CONCLUSION: Since obesity may affect the relationship between static and dynamic measures, footprints should be used with caution when inferring the characteristics of obese children's feet under dynamic conditions. CLINICAL RELEVANCE: Footprints and pedobarography should not be used at this time for clinical decision making regarding the feet of obese children.
Assuntos
Dermatoglifia , Pé , Obesidade , Pressão , Índice de Massa Corporal , Estudos de Casos e Controles , Criança , Feminino , Humanos , Masculino , Obesidade/fisiopatologia , Reprodutibilidade dos Testes , Caminhada/fisiologia , Suporte de CargaRESUMO
O objetivo deste estudo foi determinar a repetibilidade de medidas isocinéticas dos músculos adutores e abdutores do quadril, a fim de verificar a possibilidade de suas aplicações clínicas em programas de treinamento e reabilitação. Participaram do estudo sete voluntários saudáveis, universitários, ativos, do sexo masculino, com idade média de 22,8 mais ou menos 3,4 anos. Estes indivíduos foram submetidos a três avaliações, em diferentes dias, para a obtenção do pico de torque concêntrico e da média do pico de torque, unilateralmente. Em cada avaliação foram realizadas cinco contrações concêntricas máximas contínuas, em duas velocidades (30 e 90º/s), para os movimentos de adução e abdução do quadril. Os dados foram obtidos por meio de um dinamômetro isocinético da marca Biodex. A análise estatística foi realizada por meio de um ANOVA com medidas repetidas e coeficiente de correlação intra-classe (ICC), considerando o nível de significância de a < 0,05. Pode-se observar que não houve diferenças significativas entre as tentativas, considerando-se o pico de torque e a média do pico de torque (p > 0,05); na análise do ICC entre a segunda e terceira avaliação, os valores variaram de baixo a excelente (0,20 - 0,79) para a média do pico de torque e de moderado a excelente (0,52 - 0,79) para o pico de torque para ambas as velocidades. Esses resultados apontam para uma medida reprodutível da performance isocinética concêntrica demúsculos adutores e abdutores do quadril.