Narrow Results

We discuss holographic QCD in the Veneziano limit (the V-QCD models), concentrating on phenomena near the “conformal” phase transition taking place at a critical value of the ratio $x\equiv N_f/N_c$. In particular, we review the results for the S-parameter, the technidilaton, and the masses of the mesons.

An important research area in physiological and sport sciences is the analysis of the variations of the muscle reaction due to changes in walking speed. In this paper, we investigated the effect of walking speed variations on leg muscle reaction by the analysis of Electromyogram (EMG) signals at different walking inclines. For this purpose, we benefited from fractal theory and sample entropy to analyze how the complexity of EMG signals changes at different walking speeds. According to the results, although fractal theory could not show a clear trend between the variations of the complexity of EMG signals and the variations of the walking speed, however, based on the results, increasing the speed of walking in the case of different inclines is mapped on to the decrement of the sample entropy of EMG signals. Therefore, sample entropy could decode the effect of walking speed on the reaction of leg muscle. This analysis method could be applied to analyze the variations of other physiological signals of humans durin walking.

Analysis of leg muscle activation and gait variability during locomotion is an important area of research in physiological and sport sciences. In this paper, we analyzed the coupling between the alterations of leg muscle activation and gait variability in single-task and dual-task walking. Since leg muscle activation in the form of electromyogram (EMG) signals and gait variability in the form of stride interval time series have complex structures, fractal theory and approximate entropy were used to evaluate their correlation at various walking conditions. Sixty subjects walked at their preferred speed for 10 min under the single-task condition and for 90s under the cognitive dual-task condition, and we evaluated the variations of the fractal dimension and approximate entropy of EMG signals and stride interval time series. According to the results, dual-task walking caused reductions in the complexity of EMG signals and stride interval time series than single-task walking. This technique can be used to evaluate the correlation between other organs during different locomotion.

Typical gait analyses commonly define the trunk as a single rigid segment, which overlooks its inter-segmental motion. The current study examined the validity and reliability of a multi-segmented trunk marker set and the quantification of trunk motion during gait. A total of 10 young subjects were tested on two different days using identical procedures which incorporated a 22-marker set to define 7 trunk segments. Validity was evaluated by comparing results to a previous protocol. Reliability was assessed with the range of motion (ROM), coefficient of multiple correlation (CMC) and intraclass correlation coefficient (ICC). The multi-segmented trunk marker set was able to reveal different inter-segmental movement patterns. During gait, ROM reliability was approximately 92%, and within-day CMC displayed moderate to strong reliabilities while between-day CMC data had moderately weak to moderately strong associations of the multi-segmented angle waveform trajectories. Reliability of the peak angles, assessed by ICC ranged from poor to almost perfect. The findings provide trends that suggest the incorporation of a multi-segmented trunk marker set could add a useful assessment to gait analysis.

The sagittal plane, which Pauwels regarded as being of no importance for the hip, was studied in the whole body with respect to posture while walking. After a preliminary study, which confirmed the importance of the sagittal plane for the hip, we performed a 3-dimensional modelling of the hip using the finite element method, with the aim of studying the resultant force exerted at the centre of the coxofemoral joint and of analysing the actions of the muscles from the efforts recorded. On the basis of these findings, we represented the overall mechanical problem of the hip in schematic terms as a variable dynamic balance. The results of this work also allowed us to establish in detail the impact of optimisation on the muscular actions and the impact of variations in displacement and the acceleration of the partial centre of gravity on the results recorded. Finally, the isolated hip model was developed, with the aims of allowing us to study the relations existing between variations in the angle of femoral anteversion and variations in forces, and of making a contribution to anthropological studies of the structures of locomotion through the ages.

Developing a model for the dynamic force generated by a pedestrian’s foot on a supporting structure (single footfall trace model) is crucial to advanced numerical analysis and vibration serviceability assessment of the structure. A reliable model needs to reflect the inter-subject and intra-subject randomness of human walking. This paper introduces a stochastic single footfall trace model in the form of a Fourier series in which body weight, walking frequency, and the first eight harmonics are treated as random variables. An experiment used 73 test subjects, walking at a range of pacing frequencies, to record force time histories and the corresponding gait parameters. Two variability descriptors were used to indicate inter-subject and intra-subject randomness. Further statistical analysis identified the relationships between key parameters as well as the probability distribution functions of random variables. In the final step, an application of the proposed single footfall trace model was developed and tested. The proposed model represented the experimental data well in both time and frequency domains.

A forward trunk lean sometimes occurs to compensate for quadriceps muscle weakness. Since muscle weakness in the lower extremities is commonly observed in the elderly, quadriceps weakness may trigger age-related postural change. The objective of this study was to ascertain the association between forward trunk lean during walking and musculoskeletal strength in females aged between 46 and 79 years. Musculoskeletal functions (range of joint motion, degree of kyphosis, muscle strength) and joint moments during walking were measured for 13 females. Subjects who showed greater joint moments during walking tended to lean more. Moderate association was seen between mean trunk angle during walking and knee extension moment (r = 0.535, p = 0.060). There was no statistically significant correlation between the strength of the quadriceps muscle and the mean trunk angle in walking subjects (r = 0.095, p = 0.758). These observations suggested that muscle weakness in the quadriceps is largely independent of leaning of the trunk for this sample of subjects. Other factors may change the posture to a stoop, such as severe thoracic kyphosis, poor balance control, or fear of falling.

The aim of this study was to investigate the foot plantar pressure distribution and the effect of different step width during walking. Methods: Nineteen female volunteers who aged 18~30 years old and with no history of lower extremity injury were considered. Subjects walked at a pre-determined set speed with varied step width (5 cm, 10 cm, and 20 cm) for three trials at each step width. This study used an in-sole plantar pressure measurement system to collect the peak pressure, maximum ground reaction force, pressure–time integral, and force–time integral data of eight different foot regions. Results: The data revealed that the peak plantar foot pressure on the medial arch increased with wider step width (p < 0.05). In contrast, maximum ground reaction force, peak plantar pressure, pressure–time integral, and force–time integral on the lateral arch and lateral side of the metatarsals decreased with wider step width (p < 0.05). Conclusion: The results of this study revealed that smaller step width during walking result in decreasing the pressure on the medial arch of the foot. It may have the relieving effect for clients with pes planus and it can be a reference for rehabilitation clinicians while treating the above-mentioned subjects.

High heeled shoes may alter the regular loading pattern of the plantar pressure, especially increased in the forefoot area. Walking with narrow base of high heeled shoes may induce the brisk acceleration of the supported leg due to instability that increases the force on the plantar area. Particularly, this phenomenon may be amplified while slow running, but never been investigated. Materials and Methods: Plantar pressures were measured for different specific area of foot using the Pedar-X system. The effects on plantar pressure with different sized bases (1.2× 1.2 cm² and 2.2 × 3.5 cm²) of high-heeled shoe (7.8 cm in height) were examined while walking in thirteen healthy female subjects and during slow running in nine healthy female subjects. Results: The plantar pressures of the hallux and toe while wearing narrow base high heel were significantly (p < 0.05) greater than those when walking with wearing wide base one. For both narrow and wide base heels, significantly increased (p < 0.05) plantar pressure were found in the medial forefoot while slow running at 2.0 m/s as compared with walking at 1.0 m/s and 1.5 m/s. While slow running with wearing narrow base high heel indicated significantly (p < 0.05) increased plantar pressures in the medial, central and lateral forefoot and toes regions compared with those with wearing wide base one. Conclusion: The findings suggest that if individuals have to wear high heeled shoes, it would be better to select one with a wide based heel to avoid running in at any circumstance.

Footwear is an extremely important clothing item worn by all individuals. Currently, there is insufficient research regarding the influence of dress shoes on standing stability and energy consumption while walking. Therefore, the aim of this study was to evaluate the influence of dress shoes on the performance of normal subjects based on stability and energy consumption analysis. Fifteen normal subjects were recruited in this research study to stand and walk with and without shoes. The stability of the subjects in quiet standing was measured by the use of a force plate based on center of pressure (COP) sway. The energy consumption was evaluated by a heart rate monitoring system (Polar Electro) based on the physiological cost index (PCI). The mean values of PCI while walking with and without shoes were 0.29 ± 0.117 and 0.265 ± 0.112 beats/m, respectively (p-value > 0.05). The amplitudes of COP sways in the mediolateral and anteroposterior directions were 10.4 ± 3.5 and 25 ± 6.92 mm while standing with shoes and 9.3 ± 2.84 and 22.5 ± 5.25 mm in barefoot standing, respectively (p-value > 0.05). It can be concluded that wearing dress shoes does not influence the performance of subjects while standing or walking.

The purpose of this study was to compare kinematics and kinetics during walking for healthy subjects using unstable shoes with different designs. Ten subjects participated in this study, and foot biomechanical data during walking were quantified using motion analysis system and a force plate. Data were collected for unstable shoes condition after accommodation period of one week. With soft material added in the heel region, the peak impact force was effectively reduced when compared among similar shapes. In addition, the soft material added in the rocker bottom showed more to be in dorsiflexed position during the initial stance. The shoe with three rocker curves design reduced the contact area in the heel strike, which may result in increasing human body forward speed. Further studies shall be carried out after adapting to long periods of wearing unstable shoes.

Background and aim: Flatfoot is characterized based on the height of the medial longitudinal arch of the foot relative to ground. The most common methods used to evaluate the severity of flatfoot and influences of the foot insole on the alignment of the foot structure in static situation are footprints and the use of X-ray. However, both of them have some limitations and cannot be used during walking while the subject uses the insole. Therefore, the aim of this research was to find a parameter which represents the alignment of the foot structure while walking.

Methods: Two groups of normal and flat-arched subjects were recruited into this study. The location of center of ankle joint (COJ) and center of pressure (COP) while walking was obtained using Qualysis motion analysis system and a force plate. The area between COP and COJ in the medial side to the total area was the new parameter used in this study.

Conclusion: The mean value of the new parameter was 74.65 ± 7.15 and 91.86 ± 12.4 for normal and flatfooted subjects, respectively. It appears that the new parameter can be used to check the alignment of the foot structure during walking.

Clinical statement: The results of this research study can be used by clinicians to determine the alignment of the foot structure and the influence of the foot insole.

The aim of this study was to determine changes of peak pressure, maximal force, and contact area in five foot regions with two different insoles during walking and running, thereby obtaining data contributing to optimization of footwear and reduction of lower leg injury.

Twenty-six male soldiers participated in the study. Peak pressure, maximal force, and contact area were measured in five foot regions (lateral and medial heel, midfoot, lateral and medial forefoot, big toe, and toes 2, 3, 4, and 5) with two different insoles (conventional vs. custom molded shock-absorbing insoles) during a walking speed of 5 km/h and running speeds of 8 and 12 km/h using the Pedar-X tensometric system (Novel, St. Paul, MN). Measurements revealed that the shock-absorbing insoles significantly (p < 0.05) attenuated the peak pressures in heel and forefoot region and increased the contact area in the midfoot region which indicates a successful redistribution of forces that arise during the contact phase in walking and running. Shock-absorbing insoles hence may contribute to better plantar pressure distribution during walking and running, and effectively prevent lower leg injuries.

Young females with mild hallux valgus (HV) have been identified as having an increased risk of first ray deformation. Little is known, however, about the biomechanical changes that might contribute to this increased risk. The purpose of this study was to compare kinetics changes during walking for mild HV subjects with high-heel-height shoes. Twelve female subjects (six with mild HV and six controls) participated in this study with heel height varying from 0 cm (barefoot) to 4.5 cm. Compared to healthy controls, patients had significantly higher peak pressure on the big toe area during barefoot walking. When the heel height increased, loading was transferred to medial side of the forefoot, and the big toe area suffered more impact compared to barefoot in mild HV. This study also demonstrated that the center of pressure (COP) inclines to medial side alteration after high-heeled shoes wearing. These findings indicate that mild HV people should be discouraged from wearing high-heeled shoes.

Various kinds of orthosis have been designed for paraplegic subjects to stand and walk. They have been designed based on this assumption that most of the loads applied on the orthosis (OR) and body complex is transmitted by OR. In this study, it was aimed to determine the role of OR to transmit the loads by use of strain gauge system. Three spinal cord injury subjects, with lesion between T12 and L1, were recruited in this study. A motion analysis system with a Kistler force plate was used to collect the kinetic and kinematic parameters. Moreover, the loads applied on the OR were determined by use of strain gauges attached on the lateral bar of OR. The pattern of the loads applied on the complex, OR and body, differed from that of OR. Nearly 43% of adduction moment was transmitted by OR. In contrast the role of OR to transmit the flexing/extending moments and vertical force is negligible. The results of strain gauge and motion analysis systems differed completely from each other's. As the strain gauge show the absolute values of the loads applied on OR, it is recommended using its result in order to design an OR for paraplegic subjects.

Foot loading patterns can be changed by using different unstable sole structures, detailed quantification of which is of great significance for research and technological development in falling prevention and lower limb disorders rehabilitation. In this study, unstable soles constructions are adjusted through unstable elements in heel and medial, neutral and lateral forefoot and the foot loading patterns are comparatively studied. A total of 22 healthy male subjects participated in this test. Subjects are asked to walk over a 12 m walkway with control shoes and experimental shoes in self-adapted speed. Significant peak pressure, contact area and pressure-time integral differences in middle foot are found between control shoes and experimental shoes. In addition, peak pressure and pressure-time integral are found to increase significantly with unstable elements adding to center forefoot. The results showed that adjusting the unstable elements in coronal plane of forefoot could effectively alter the distribution of plantar pressure, this could potentially offer a mechanism for preventing falling of elderly and rehabilitation of lower extremity malfunctions. This study also demonstrates a novel concept that unstable element could be effectively adjusted in terms of position to meet different functional requirement.

Transfemoral amputation (TFA) results in reduced sensation, altered body image and loss of function. Energy expenditure is known to be significantly higher in individuals with TFA compared with their healthy counterparts. Kinetic and kinematics characteristics of individuals with TFA have been evaluated; however, stability during quiet standing has not been examined. This study evaluated stability, gait performance and energy consumption in individuals with TFA during standing and walking. A total of subjects (5 healthy and 5 with TFA) participated in this study. The motion of lower limb joints and the force applied on the leg were evaluated using a motion analysis system, Qualysis. Stability during standing was examined using a force plate and energy consumption during walking was evaluated based on physiological cost index (PCI). Group comparisons were made using the independent t-test. There was no significant difference in stability between subjects with TFA and normal subjects during standing. However, walking speed in subjects with TFA decreased significantly compared to normal subjects (p = 0.014). PCI of subjects with TFA was 0.525 ± 0.13 compared to 0.298 ± 0.059 beats/m in normal subjects (p < 0.05). It seems that stability in subjects with TFA was similar to their healthy counterparts. However, energy consumption was higher in the TFA group than in normal subjects, which may be due to slow walking speed. Clinicians are to be aware of these findings as they may be useful for effective management of the patients with TFA.

This study set out to investigate if a relationship exists between weight change and changes in 3D acceleration signals associated with walking. In addition to giving biomechanical information, this relationship could be applied in conjunction with new weight management solutions to address the excess weight problem currently plaguing the world. The study was conducted with 15 subjects. For a period of two months, they were weighed every morning and carried a 3D accelerometer during the working day. Daily accelerometric signals were recorded and signals recognized as walking were analyzed. To obtain information in a more controlled situation and higher weight change, a separate follow-up study was carried out involving one test subject performing controlled walking exercises. Our results show that a relationship does exist between weight change and 3D acceleration signals. The obtained correlation coefficient between weight change and the acceleration-related parameter was 0.21 for the combined result of all test subjects (n = 147, p = 0.01). Higher correlations were recorded for individual subjects (r = 0.97, p < 0.001). Also the follow-up with controlled walking exercises showed a high correlation (r = 0.89, p < 0.001). On the other hand, statistically significant results were not obtained for all subjects, and identical signal parameters did not always produce similar results.

High amplitude of movements in the lower body during walking is attenuated in the upper body to stabilize the head, which serves as the platform of critical sensory systems (vestibular and visual). The upper body attenuation has been investigated on the linear acceleration, however, not on the angular motion. This study aimed to compare the attenuation of axial rotation in different age-groups. Methods: Thirty healthy men (15 young and 15 elderly) participated in this study. Subjects walked on a level surface with gyro sensors attached at four locations of the back (pelvis, thorax, shoulder, and head), from which the angular motion was derived. Outcome measures included the average peak-to-peak amplitude of axial rotation at all sensor locations and the phase delay at each location with reference to the pelvis. Results: Age-position interaction was significant for both the amplitude and phase delay. Post hoc test revealed that rotation amplitude was similar at pelvis, thorax and shoulder in the elderly, whereas it was significantly reduced at the thorax-shoulder section in the young. The elderly also showed smaller phase delay at shoulder and head than those of the young. Discussion: The results suggest that the attenuation by upper trunk was reduced and the shoulder and head motions were more tightly coupled to the pelvis in the elderly, i.e., the upper body moved more like a rigid body in the axial motion.

During walking, attuning the heel contact to the external cueing is attentional and physical demanding. Based on this point of view, this is a preliminary study conducted for identifying the temporal accuracy of subjects for rhythmic auditory cueing, and to identify the balancing ability of the elderly based on this information. A measurement system was constructed to measure the motion delay time for the given rhythm and a pilot gait experiment was conducted for young adults while performing a cognitive dual task. The system consisted of a metronome and an accelerometer sensor measurement unit and is implemented as a program using LabVIEW. This pilot gait experiment measured individual delay times in 15 healthy adults in their 20s under two conditions: metronome walking (MET) and metronome walking with backward counting (MET+BC). Consequently, the delay time of MET and MET+BC conditions was $128.8\pm 29.0$msec and $200.2\pm 37.0$msec, respectively ($p<0.05$). Further experiments with the elderly will be needed to confirm whether such delay time can be used as an indicator for balancing ability.