Control of optical absorption of silica glass by Ag ion implantation and subsequent heavy ion irradiation.

Silica glass samples were implanted with 50-380 keV Ag ions. After ion implantation, some samples were subsequently irradiated with 16 MeV Au ions. The effects of the implantation and the subsequent Au ion irradiation on the optical absorption spectra and morphologies of the Ag nanoparticles produced in the samples were studied by using an ultraviolet-visible scanning spectrophotometer and a transmission electron microscope, respectively. For the samples implanted with 200 keV or 380 keV Ag ions to high fluence, optical absorption peaks appeared around 600 nm, as well as the well-known surface plasmon resonance peaks around 400 nm, and Ag spherical nanoparticles with a high spatial density were observed. The absorption peaks around 600 nm are explained as being due to interactions between the Ag nanoparticles (inter-particle interaction). Under the subsequent irradiation with 16 MeV Au ions, the optical absorption around 400 and 600 nm showed a blue shift and the peak intensity markedly decreased. Transmission electron microscopy observation revealed an elongation of the Ag nanoparticles along the direction of the 16 MeV Au irradiation, and a resulting enlargement of the distances between the nanoparticles. The change in the peak wavelength and peak intensity of the optical absorption by the 16 MeV Au irradiation can, therefore, be explained as originating from a decrease in inter-particle interaction.

Classification of the foot kinematics during gait and the characteristics of the knee and hip kinematics in individuals with pronated foot.

Overuse injuries are often caused by pronated foot and the associated abnormal lower-extremity kinematics during dynamic activities. Various patterns of foot kinematics are observed among individuals with pronated feet during dynamic activities, resulting in different dynamic kinematics of the proximal joint. This study aimed to identify the foot kinematic patterns during gait among individuals with pronated feet and evaluate the relationship between these foot kinematic patterns and the hip and knee kinematics. A three-dimensional motion capture system was used to collect data regarding the foot, knee, and hip kinematics during the stance phase of gait of 42 individuals with pronated feet. A hierarchical cluster analysis method was used to identify the optimal number of clusters based on the foot kinematics, including navicular height (NH) at initial contact and dynamic navicular drop (DND). The differences in the cluster and demographic variables were examined. One-dimensional statistical parametric mapping was used to evaluate the differences in the time histories of the NH, knee, and hip kinematics during the stance phase. Three subgroups were identified on the basis of the NH and DND: Cluster 1, moderate NH at initial contact and larger DND; Cluster 2, highest NH at initial contact and smaller DND; and Cluster 3, lowest NH at initial contact and smaller DND. The hip adduction angle of Cluster 1 was significantly higher than that of Cluster 3 from the 0% to 51% stance phases. Further longitudinal studies are needed to clarify the relationship between identified subgroups and the development of overuse injuries.

Classification of medial longitudinal arch kinematics during running and characteristics of foot muscle morphology in novice runners with pronated foot.

BACKGROUND: Novice runners with pronated feet are at an increased risk of running-related injuries. However, not all runners with pronated feet have increased foot pronation during running. Moreover, although foot muscle morphology is related to static foot alignment, the relationship between foot muscle morphology and foot kinematics during running remains unclear. We aimed to determine foot kinematic patterns during running among novice runners with pronated feet and the presence of a relationship between these foot kinematic patterns and foot muscle morphology. METHODS: Twenty-one novice runners with pronated feet participated in this study, and data on 39 lower limbs were collected. Data on foot kinematics during running (rearfoot strike) were collected using a three-dimensional motion capture system in terms of navicular height (NH) at initial contact and dynamic navicular drop (DND). A hierarchical cluster analysis method was used to identify the optimal number of clusters based on these two foot-related kinematic variables. Following identification of the clusters, differences in cluster variables and cross-sectional areas of selected foot muscles assessed using ultrasonography in each cluster were examined. The muscles of interest included the abductor hallucis, flexor hallucis brevis and longus, flexor digitorum brevis and longus, and peroneus longus. RESULTS: Three subgroups were identified based on foot kinematics during running: cluster 1, lowest NH at initial contact and larger DND; cluster 2, moderate NH at initial contact and smaller DND; and cluster 3, highest NH at initial contact and larger DND. Clusters 1 and 3 had a larger abductor hallucis compared with cluster 2, and cluster 3 had a larger flexor hallucis brevis compared with cluster 2. SIGNIFICANCE: These subgroups may differ in terms of resistance to and type of running-related injury. Moreover, foot kinematics during running is possibly impacted by the morphology and function of medial intrinsic foot muscles.

Relationship between foot muscle morphology and severity of pronated foot deformity and foot kinematics during gait: A preliminary study.

BACKGROUND: The morphology of foot muscles that support the medial longitudinal arch differs between normal and pronated feet. The degree to which the difference depends on the severity of the pronated foot deformity is unclear. In the clinical setting, however, to reduce the pronated deformity, muscle-strengthening exercises are performed. RESEARCH QUESTION: Does a relationship exist between foot muscle morphology and severity of the pronated foot deformity and foot kinematics during gait? METHODS: Using the six-item foot posture index (FPI-6), 26 study participants were assessed for their foot posture and divided into two groups of 13 participants each based on the FPI-6 score: pronated foot group (with a score of 6-9) and highly pronated foot group (with a score of 10-12). Select foot muscles were scanned with ultrasonography, and muscle thicknesses were measured. The following were the muscles of interest: abductor hallucis, flexor hallucis brevis and longus, flexor digitorum brevis and longus, and peroneus longus. Foot kinematic data during gait was collected using a three-dimensional motion capture system as a dynamic navicular drop. RESULTS: No between-group differences were noted for muscle thickness and dynamic navicular drop. However, the abductor hallucis and flexor hallucis brevis thicknesses were correlated with the dynamic navicular drop, but not with the severity of the pronated foot deformity. SIGNIFICANCE: In individuals with pronated foot deformity, more developed abductor hallucis and flexor hallucis brevis muscles may reduce the dynamic navicular drop that represents the degree of medial longitudinal arch deformation during the stance phase of gait.

Effects of plantar intrinsic foot muscle strengthening exercise on static and dynamic foot kinematics: A pilot randomized controlled single-blind trial in individuals with pes planus.

BACKGROUND: No reliable evidence has confirmed whether plantar intrinsic foot muscle strengthening exercises improve static and dynamic foot kinematics in individuals with pes planus. RESEARCH QUESTION: Does the short-foot exercise affect static foot alignment and foot kinematics during gait in individuals with pes planus? METHODS: This was a randomized controlled single-blind trial involving 20 participants with pes planus who were randomly allocated to a short-foot exercise group (exercise) or a control group (controls). Exercise patients performed a progressive short-foot exercise three times per week for 8 weeks; controls received no intervention. Before and after the 8-week intervention, foot kinematics during gait, including dynamic navicular drop-the difference between navicular height at heel strike and the minimum value-and the time at which navicular height reached its minimum value were assessed, using three-dimensional motion analysis. We assessed static foot alignment by foot posture index and navicular drop test, and the thickness of the intrinsic and extrinsic foot muscles using ultrasound. All measurements were performed by one investigator (KO) blinded to the participants' allocation. RESULTS: After the 8-week intervention in the exercise group, foot posture index scores with regard to calcaneal inversion/eversion improved significantly (p < 0.05). Moreover, the time required for navicular height to reach the minimum value decreased significantly (p < 0.01). SIGNIFICANCE: For individuals with pes planus, the short-foot exercise effectively corrected static foot alignment and temporal parameters of foot kinematics during gait. This temporal change, which shortens the time for navicular height to reach its minimum value, indicates an improved windlass mechanism. Therefore, short-foot exercise might effectively prevent or treat injuries related to the pes planus alignment.

The effect of additional activation of the plantar intrinsic foot muscles on foot kinematics in flat-footed subjects.

BACKGROUND: Strengthening exercises of the plantar intrinsic foot muscles (PIFMs) are often prescribed to flat-footed subjects because of the capacity of the PIFMs to support the medial longitudinal arch (MLA). However, it is unclear whether the capacity of the PIFMs to support the MLA is enough to change the foot kinematics in flat-footed subjects. To confirm this, the current study examined changes in foot kinematics in flat-footed subjects during standing and gait accompanied by changes in the activity of the PIFMs. METHODS: Eighteen flat-footed subjects were randomly assigned to an electrical stimulation group (ESG) or a control group (CG). In the ESG, electrical stimulation to the PIFMs was applied during standing and gait to simulate reinforcement of the PIFMs. Then, foot kinematics were measured using 3D motion analysis, and the amount of change from baseline (when no electrical stimulation was applied) was compared between the groups. RESULTS: In the gait analysis, the time at which the MLA height reached its minimum value was significantly later in the ESG, with no reduction in the MLA height at that time. Moreover, forefoot inversion angle and tibial external rotation angle were significantly increased in the ESG at that time. In the standing analysis, there were no significant differences between the groups. CONCLUSION: The results revealed that in flat-footed subjects, the PIFMs have the capacity to support the MLA enough to change foot kinematics during gait. Strengthening these muscles may be effective in preventing or treating lower extremity overuse injuries related to flat-foot alignment.