Effects of additional load at different heights on gait initiation: A statistical parametric mapping of center of pressure and center of mass behavior.

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.

Effects of the infrared laser on classical ballerinas' feet: Analysis of plantar foot and static balance.

BACKGROUND AND PURPOSE: Overuse injuries and painful symptoms in athletes and dancers (especially classical ballerinas) may lead to reduced functional performance. However, laser application may reduce pain and increase physical conditioning. The aim of the current study was to evaluate the immediate and long-term effects of infrared laser on classical ballerinas' feet. METHODS: Eight female adults who perform classical ballet training and feel pain in their foot, but report no injuries in the last 6 months participated in the study. Infrared laser (808 nm) was applied on ballerina's feet twice a week during three months. The laser parameters utilized were 100 mW average optical power and spot size of 0.04 cm2 applied during 1 min, leading to 6 J and 125 J/cm2 per point. Thermography, algometry and unipodal static standing balance test were performed. RESULTS: There was a significant increase in plantar arch temperature (1.6 °C for center and 2.3 °C for border, p < 0.05) immediately after laser treatment for all ballerinas. The pressure pain thresholds (PPT) were significantly increased for 5 of 7 analyzed sites (p < 0.05). Regarding to the static standing balance, the time on one-foot showed a significant increases (from 23 ± 12 s to 34 ± 13 s, p < 0.05) only when the test was performed on the left foot (support foot). CONCLUSION: Then, there were pain relief and improvement of functional performance in ballerinas. The possible mechanism of laser action in reducing pain and thus enhancing performance, like higher blood flow of foot due to an increase of cutaneous temperature, will be discussed.

Standing balance in preschoolers using nonlinear dynamics and sway density curve analysis.

The aim of the present study was to investigate how age and sensory deprivation affect the temporal organization of CoP sway variability and the postural corrective commands during standing balance in typically developing preschoolers. A sample of 57 children aged 3-5 years participated in the study. Structural stabilometric descriptors of sample entropy (SEn), detrended fluctuation analysis (DFA), and sway density curve (SDC) analysis were employed to assess features of center of pressure sway. A force platform was used to collect center of pressure data during standing balance over 40 s in four conditions: standing on rigid and foam surfaces with eyes open and closed. The main results are as follows: (1) sample entropy decreased and DFA_coefficient increased with age, while the SDC variables remained unaltered among the 3-, 4-, and 5-year-old children; (2) as sensory conditions became more challenging, sample entropy decreased and DFA_coefficient increased, while MT and MD decreased and MD increased; age did not influence the responses to sensorial deprivation. In conclusion, 5-year-old children showed decreased variability of CoP sway during standing balance compared with the younger children, but all children used the same corrective torques to control for perturbations. More challenging sensory deprivation conditions resulted in decreased variability of postural sway, higher amplitudes and more frequent correcting torques for stabilization, but age did not influence these behaviors.

Footwear and Foam Surface Alter Gait Initiation of Typical Subjects.

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.

Effects of four days hiking on postural control.

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.

Psychometric properties of functional balance tests in children: a literature review.

AIM: Identifying balance problems are the first step towards monitoring and rehabilitation. Therefore, this paper aims to make an overview of the psychometric properties of the functional balance tests available for children. METHOD: A literature search was performed in PubMED and Web of Science on 8 February 2014 and updated on 6 July 2014. A conceptual framework for functional balance tests was defined, taking balance control components and task constraints into account. The tests were selected for inclusion by consensus of 2-3 reviewers using the conceptual framework. RESULTS: Fourteen tests were investigated in 25 articles and analysed within the conceptual framework. The Timed Up and Go test, Pediatric Balance Scale, and Pediatric Reach Test are well investigated and all show good reliability. Validity remains unclear because of lack of a criterion standard to measure balance control. INTERPRETATION: Because of the lack of good methodological studies, strong evidence for the use of one or more functional balance tests in children cannot be provided. Moreover, it is necessary that a criterion standard to measure balance is established.

Comparison of static footprints and pedobarography in obese and non-obese children.

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.

Repetibilidade de medidas isocinéticas dos músculos adutores e abdutores do quadril / Reliability of isokinetic measurements of hip adductors and abductors

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.