Kenta Moriyasu

New technique of three directional ground reaction force distributions

In this research, a shoe mounted miniature triaxial force sensors was developed to construct a new technique for the measurement of ground reaction force (GRF) distributions in contact area during running. Five sensor and 14 dummy block devices were mounted to a commercial marathon shoe. The shoe mass is 270.0 g. By using the shoe, distributions of lateral, longitudinal and normal direction force components at 19 local positions were measured by changing sensor arrangement at running speed of 5.5 min/km. The results showed contact periods and time history of GRFs at each position during stance phase was clearly different. It was confirmed that the resultant forces of the GRFs obtained from the sensor shoe gave close agreement with the GRFs obtained from the conventional force plate. Based on the distribution of the traction coefficient, which is calculated from the horizontal force divided by the vertical force, high traction coefficient area were clarified at the time 20 and 80% of stance phase. The distributions of the traction coefficient will imply area to apply structure and material design of the high grip shoe sole to avoid slip-related falls.

Multi-segmental foot modelling during shod activity: study of running shoe integrity

Introduction Multi-segmental foot modelling (MSFM) during shod activity has the potential to enhance our understanding of how footwear influences foot motion. Recent work by Bishop et al. (2015) and Shultz & Jenkyn (2012) has validated the incision parameters to accommodate surface mounted markers for two alternative MSFMs, requiring 7 and 5 incisions respectively, within the shoe. These MSFMs have been sparsely used in contrast to 3DFoot model (Leardini et al. 2007) which would require 10 incisions and has not been used previously to assess in-shoe foot motion. Purpose of the study To determine the influence of incisions to accommodate Jenkyn and Nicol (JN) and 3DFoot MSFMs upon the structural integrity of neutral running shoes. Methods Two procedures were applied to assess shoe deformation. A) Eight males (30±8yrs, 1.78±0.05m, 84±7kg) completed 2 testing sessions. Participants ran at a self-selected pace (3±0.5m.s-1) in standard ASICS running shoes. Baseline shoe deformation data was collected during the first session. Prior to session 2, 25mm incisions were made to accommodate MSFMs: 3DFoot (left shoe) and JN (right shoe). Kinematic data were recorded using a 3D motion analysis system (VICON, Oxford, England) at 200Hz. Three retro-reflective markers (Figure 1) were used to measure as shoe distance and shoe angle at initial contact (IC), heel rise (HR) and toe off (TO). Shoe deformation measures were compared using paired t-tests. B) Material strain of the shoe upper was assessed in 1 male participant (26yrs, 1.80m, 80kgs) using ARAMIS optical system. Material strain patterns were compared between intact and cut conditions using Trend symmetry (TS) analysis (Crenshaw & Richards, 2006). Here Figure 1. Results No significant differences (p > 0.05) in shoe distance were recorded between intact and cut conditions but significant differences (p < 0.05) were reported in shoe angle at all three events of running gait (Table 1). Material strain assessment showed lower TS scores for the lateral aspect of the shoe (TS = 0.81 ± 0.11) than the medial aspect (TS = 0.89 ± 0.12). Symmetry was greater between the intact and JN shoe (TS= 0.88 ± 0.10) than the intact and 3DFoot shoe (TS = 0.82 ± 0.13). Here Table 1. Discussion and Conclusion Analysis of kinematic shoe deformation measures revealed individual responses to incisions made within the upper of a running shoe to accommodate MSFMs. Significant (p < 0.05) changes in shoe angles were noted between the intact and cut conditions at IC and TO for the JN incisions and HR for the 3DFoot incisions. However, while the changes in shoe angle were significant, the mean difference was small (≤ 5°). This value is lower than the minimal important difference proposed by Nester et al. (2007) for comparison of gait kinematics. Thus, it may be argued that the differences in shoes angles between intact and cut conditions were negligible and the results support the use of either MSFM to assess shod foot motion. While the use of kinematic measures to infer the shoes structural integrity have been used previously (Shultz and Jenkyn, 2012), no validation of these measure has been undertaken. The small and non-systematic findings reported in both this study and that of Shultz and Jenkyn (2012), particularly for shoe distance measures; question the sensitivity of kinematic shoe deformation measures to detect changes in structural integrity. Material strain analysis was used to further explore area specific alterations in the running shoes structural integrity from the different incision sets. The material strain analysis supported the use of the JN foot model to assess in-shoe foot kinematics, due to higher symmetry scores and smaller mean differences between the intact and JN shoes. Further exploration of additional means of assessing the influence of incisions to accommodate MSFM upon the shoes structural integrity is warranted. References Bishop, C. et al. (2015). Gait Posture, 41 (1), 295-299. Crenshaw, S. and Richards, J. (2006) Gait Posture, 24 (4), 515-521. Jenkyn, T. and Nicol, A. (2007). J Biomech, 40 (14), 3271-3278. Leardini, A. et al. (2007). Gait Posture, 25 (3), 453-462. Nester, C. et al. (2007). J Biomech, 40 (15), 3412-3423. Shultz, R. and Jenkyn, T. (2012). Med Eng Phys, 34 (1), 118-122.

Basic study on cleat shape design in soccer boots

Increasing mechanically available traction improved curve sprinting performance but only to a certain level. The divergence between the theoretically predicted and the experimentally measured maximum curve sprinting speed at the 0.8 and 1.2 traction conditions suggests that other factors might set new constraints for further performance improvement. These speed-limiting factors warrant further study. Joints of the lower extremity experience large loading during running turns (Besier et al. 2001). Chang and Kram (2007) proposed that during top speed curve sprinting, muscles acting to stabilize the lower extremity joints in the frontal and transverse plane may have reached critical operation limits, which may in turn inhibit the leg from generating more extension force in the sagittal plane. Footwear designs that can effectively reduce the ankle and knee resultant moments in the non-sagittal planes will facilitate the testing of this theory and may potentially improve curve sprinting performance.

Measurement technique of GRF components distribution in running

medial and lateral sides. Typical results are shown in Figure 4. Vertical axis denotes the markers displacement, the lateral direction is defined to be positive. At 10% of stance, maximum deformation in the lateral side, d Lat appears, after then that in medial side, d Max Med appears. These results can be understood by considering foot motion until FF. d Lat and d Max Med are 3.74 and 1.76mm. These values were smaller than those of the conventional counters with constant thickness. It was concluded that the proposed heel counter can reduce the footwear weight and control excessive heel motion at the same time. Conclusions

Effect of Porosity and Normal Load on Dry Sliding Friction of Polymer Foam Blocks

In this study, the effect of porosity on the dry sliding fiction of ethylene-vinyl acetate (EVA) foams was investigated under different normal load conditions. EVA foam blocks with varying porosities were slid against a smooth stainless steel plate under dry conditions. The friction coefficient increased with increasing porosity under all of the normal load conditions. In addition, the contact area was estimated using a contact model considering elastic buckling of the cell walls (elastic collapse). The elastic collapse area in the anterior portion of the EVA foam block increased with increasing normal load and porosity, which resulted in an increased contact area. Furthermore, the friction coefficient was positively correlated with the estimated contact area divided by the normal load, indicating that adhesion friction increases with increasing porosity of polymer foams. These results may contribute to the design of high-friction, lightweight shoe sole tread blocks prepared using polymer foam blocks.

Abrasion wear analysis in running shoes using a gridded methodology with CIE-L-a-b colour identification

Wear identification and projection have eluded shoe manufacturers due to the myriad of factors that affect the abrasion wear of shoes. Using a gridded three-dimensional cloud comparison in CloudCompare software, abrasion wear thickness of shoes was identified using the CIE-L-a-b colour system that is interpolated with the physical formula representation of colours. After obtaining the thickness lost, other wear factors like the material properties of the shoe sole, the runners’ personal profile and the running schedule were combined for wear projection. The methodological process from a non-destructive wear detection to wear projection allows shoe manufacturers to reduce the iterations of wear testing while maximizing the entire analysis of shoe wear. Shoe samples were kindly sponsored by ASICS Institute of Sport Science.

Establishment of the simplified technique for estimating joint moments in foot during running

To prevent injuries such as stress fractures during long-distance running, it is important to clarify the joint loads on the foot. The purpose of this study was to establish a method of estimating joint moments on foot during stance phase in running. Loads on the ankle, tarsometatarsal, and metatarsophalangeal joints were estimated by a new simplified foot model with the three-dimensional force distribution on the bottom of shoe sole. Three-dimensional ground reaction force distributions were obtained from a running test with special shoes on which three-axis miniature force sensors had been mounted. Foot model consisted of three segments: toe, mid foot, and heel. Each segment was linked with metatarsophalangeal, tarsometatarsal, and ankle joints, respectively. By calculating inverse dynamics with this model, each joint moment component, which is the contribution of forces on each sensor to joint moments, could be estimated. Each joint moment was equivalent with the sum of moment components. Results showed that the tarsometatarsal and metatarsophalangeal joint moments are estimated during the whole stance phase. The moment component distributions of each joint could also be quantified. In comparison of the moment components corresponding to each metatarsal bone, the loads of the second- and third-ray metatarsal bones were higher than those of the others. Furthermore, the effect of sole thickness distribution on moment component distribution was also confirmed. Increase of sole thickness in the vicinity of the first and fifth metatarsal bone heads reduced the load of the second- and third-ray metatarsal bones. These results showed a possibility to prevent stress fractures on foot with the sole design.

Establishment of the estimated technique for joint loads in foot during running

Recently, long distance running is getting a popular leisure with health conscious and popularity of running events. Meanwhile, it has been said that risk of lower extremity injuries such as tibial and metatarsal bones stress fractures is increased with repeated loads during long distance running (Van Gent et al., 2007). To clarify the loads subjected to foot joints, previous studies mainly discuss them based on plantar pressure distribution and ground reaction force (GRF) (Amir et al., 2011; Beragstra et al., 2015). However, in order to precisely calculate foot joint loads, it is important to consider three-dimensional (3D) GRF distribution at foot–ground interface.

A Method to Evaluate Abrasion of Shoe-Sole Using 3D Scanning Technique

A study was carried out to evaluate abrasion of shoe-sole for subjects with different running gait. A 3 dimensional (3D) scanning approach together with a commercial software, CloudCompare Mesh Cloud Comparison was utilized for this study. In CloudCompare, a grid system and colored scale was applied to identify the region and extend of abrasion of the shoe-sole. This study clearly showed the extent of abrasion on regions of shoe-sole identified from the colored scale. This paper was done with kind support from Asics Institute for Sports Science, Kobe, Japan and Institute for Sport Research (ISR-NTU).