Satoru Hashizume

Ethnicity and spatiotemporal parameters of bilateral and unilateral transtibial amputees in a 100-m sprint.

Similar to able-bodied sprinters, most of the medals for the 100-m sprint in past Paralympic Games and IPC Athletics World Championships were dominated by West African (WA) and Caucasian (CC) amputee sprinters, not Asian (AS) sprinters. Although these results indicate differences in sprint performance due to ethnicity, little is known about the ethnicity and spatiotemporal parameters of the 100-m sprint for amputee sprinters. The purpose of this study was to investigate the differences in the spatiotemporal parameters of WA, CC and AS sprinters with bilateral and unilateral transtibial amputations during a 100-m sprint. We analyzed 6 WA, 28 CC, and 10 AS amputee sprinters from publicly available Internet broadcasts. For each sprinter’s run, the average speed, average step length, and step frequency were calculated by using the number of steps in conjunction with the official race time. No significant differences were found in the spatiotemporal parameters of the 100-m sprint for the WA and CC groups. On the other hand, the average speed of the AS group was significantly lower because of its shorter step length during the 100-m sprint. The results suggest that WA and CC sprinters would perform similarly during a 100-m sprint, but AS sprinters would not.

Differences in spatiotemporal parameters during 200-m sprint between bilateral and unilateral transfemoral amputees

Background and aim: Although Paralympic T42 class Men’s 200u2009m sprints are currently competed by athletes with bilateral and unilateral transfemoral amputations, there may be performance differences between the groups. This study aimed to compare the spatiotemporal parameters of a 200-m sprint between bilateral and unilateral transfemoral amputees wearing running-specific prostheses. Technique: We analyzed 29 races (nine sprinters) with bilateral or unilateral transfemoral amputations from publicly available Internet broadcasts. For each sprinter’s race, the average speed, step frequency, and step length were calculated using the number of steps in conjunction with the official race time. Discussion: Average speed of bilateral transfemoral amputees was 5.7% greater than in unilateral transfemoral amputees. Bilateral transfemoral amputees exhibited lower step frequency (–8.9%) but longer step length (16.3%) than unilateral transfemoral amputees. Therefore, even in the same Paralympic classification (T42), different spatiotemporal strategies exist between bilateral and unilateral transfemoral amputees wearing running-specific prostheses during 200-m sprints. Clinical relevance Since different spatiotemporal strategies exist between bilateral and unilateral transfemoral amputees during 200-m sprints, our data supports recent revisions of classification rules (1st January, 2018), which each population was allocated into the different classification (T61 and T63, respectively).

Leg stiffness during sprinting in transfemoral amputees with running-specific prosthesis

Carbon fiber running-specific prostheses are designed to reproduce the spring-like stepping behavior of individuals similar to springs loaded by the entire body mass (i.e. spring-mass model). The aim of this study was to test whether leg stiffness would be modulated differently between intact and prosthetic legs in transfemoral amputees wearing RSP during sprinting. Eight unilateral transfemoral amputees performed maximum sprinting along an indoor overground runway. Leg stiffness was calculated from kinetic and kinematic data in intact and prosthetic legs. The results showed that leg stiffness was for the prosthetic limb approximately 12% decreased compared to the intact limb. Although there was no difference in leg compression between the legs, maximal vertical ground reaction force was significantly greater in the intact leg than in the prosthetic one. These results indicate that asymmetric modulation of leg stiffness in transfemoral amputees with running-specific prostheses is mainly associated with asymmetric ground reaction force.

Comparison of the Achilles tendon moment arms determined using the tendon excursion and three‐dimensional methods

The moment arm of muscle‐tendon force is a key parameter for calculating muscle and tendon properties. The tendon excursion method was used for determining the Achilles tendon moment arm (ATMA). However, the accuracy of this method remains unclear. This study aimed to investigate the magnitude of error introduced in determining the ATMA using the tendon excursion method by comparing it with the reference three‐dimensional (3D) method. The tendon excursion method determined the ATMA as the ratio between the Achilles tendon displacement during foot rotation from 15° of dorsiflexion to 15° of plantarflexion and the joint rotation angle. A series of foot images was obtained at 15° of dorsiflexion, the neutral position, and 15° of plantarflexion. The 3D value of the ATMA was determined as the shortest distance between the talocrural joint axis and the line of action of the Achilles tendon force. The ATMA determined by the tendon excursion method was smaller by 3.8 mm than that determined using the 3D method. This error may be explained mainly by the length change in the Achilles tendon due to the change in the force applied to it, as passive plantarflexion torque was different by 11 Nm between 15° of dorsiflexion and 15° of plantarflexion. Furthermore, the ATMAs determined using the 3D and tendon excursion methods were significantly correlated but the coefficient of determination was not large (R2 = 0.352). This result suggests that the tendon excursion method may not be feasible to evaluate the individual variability of the ATMA.

Spatiotemporal Parameters of 100-m Sprint in Different Levels of Sprinters with Unilateral Transtibial Amputation.

The aim of this study was to investigate differences of the spatiotemporal parameters in a 100-m sprint among elite, sub-elite, and non-elite sprinters with a unilateral transtibial amputation. Using publicly available Internet broadcasts, we analyzed 125, 19, and 33 records from 30 elite, 12 sub-elite, and 22 non-elite sprinters, respectively. For each sprinter’s run, the average velocity, step frequency, and step length were calculated using the number of steps in conjunction with the official race time. Average velocity was greatest in elite sprinters (8.71±0.32 m/s), followed by the sub-elite (8.09±0.06 m/s) and non-elite groups (7.72±0.27 m/s). Although there was a significant difference in average step frequency between the three groups, the effect size was small and the relative difference among the three groups was 3.1%. Statistical analysis also revealed that the average step length was longest in elite sprinters, followed by the sub-elite and non-elite groups. These results suggest that the differences in sprint performance between the three groups is mainly due to the average step length rather than step frequency.

Individual Step Characteristics During Sprinting in Unilateral Transtibial Amputees

To understand the step characteristics during sprinting in lower-extremity amputees using running-specific prosthesis, each athlete should be investigated individually. Theoretically, sprint performance in a 100-m sprint is determined by both step frequency and step length. The aim of the present study was to investigate how step frequency and step length correlate with sprinting performance in elite unilateral transtibial amputees. By using publicly-available Internet broadcasts, the authors analyzed 88 races from 7 unilateral transtibial amputees. For each sprinters run, the average step frequency and step length were calculated using the number of steps and official race time. Based on Pearsons correlation coefficients between step frequency, step length, and official race time for each individual, the authors classified each individual into 3 groups: step-frequency reliant, step-length reliant, and hybrid. It was found that 2, 2, and 3 sprinters were classified into step-frequency reliant, step-length reliant, and hybrid, respectively. These results suggest that the step frequency or step length reliance during a 100-m sprint is an individual occurrence in elite unilateral transtibial amputees using running-specific prosthesis.

Estimation Accuracy of Average Walking Speed by Acceleration Signals: Comparison Among Three Different Sensor Locations

The ubiquity of wearable sensors now enables us to measure a user’s walking speed outside of a laboratory or clinical setting, during activities of daily living. However, this technology is recent, and researchers have yet to determine the locations on the body that produce the most accurate data from these sensors. This study aims to compare the accuracy of average walking speed estimation measured using acceleration data from three body landmarks: wrist, pelvis, and ankle. Estimation models are derived from the gait data of 247 healthy adults using stepwise linear multiple regression analyses. The absolute value of the within-participant mean of errors between actual average walking speed and estimated average walking speed is computed and compered across landmarks. The ankle is the most accurate locations from which to estimate average walking speeds from acceleration signals, whereas the wrist was the least accurate locations. Walking speed is an important measure of health and function, especially in older people, and accurately estimating walking speeds in daily life may be helpful in predicting health outcomes in the elderly.

Estimation Accuracy of Step Length by Acceleration Signals: Comparison Among Three Different Sensor Locations

Methods to estimate step length using accelerometers are gaining attention in recent times. However, the influence of the sensor location on the accuracy of step length estimation is still unknown for models fabricated in a uniform manner. Therefore, the purpose of this study was to compare the accuracy of step length estimations among the following three body parts: ankle, pelvis, and wrist. Ten time-normalized acceleration signals from one gait cycle were obtained from 247 healthy adults aged 20 to 77 while walking barefoot at a comfortable, self-selected speed. Linear multiple regression analyses with leave-one-participant-out cross validation technique were used to build the algorithms. The absolute value of mean error for each participant (AME) was computed to compare the accuracies among the body parts. Mean (standard deviation) values of AME for each part were as follows: ankle, 2.66 (2.24) cm; pelvis, 3.09 (2.39) cm; and wrist, 4.05 (3.01) cm. Statistical analyses revealed significant differences for the ankle–wrist and pelvis–wrist estimations. We found that step length can be estimated from the acceleration signal of the ankle or pelvis with almost the same accuracy (approximately 3 cm of average error between participants). Also, estimation of step lengths with the acceleration signals obtained from the wrist needs to be conducted more carefully than those obtained from the ankle or pelvis.

Modeling and analysis of individual with lower extremity amputation locomotion using prosthetic feet and running-specific prostheses

Prostheses have enabled individuals with lower extremity amputation (ILEAs) to accomplish many daily activities. Prosthetic feet allow ILEA to locomote and improves their quality of life. Carbon-fiber running-specific prostheses (RSPs) with energy storing capabilities support ILEAs to perform sprinting by partly providing spring-like properties in their amputated legs. Previous studies declare the spring-like RSP behavior and stiffness regulation during ILEA sprinting using RSP, though little is known about the behavior of the whole system that is a complex combination of human body and prostheses. This paper models this combined system with human and prosthetic foot and RSP using the digital human technology, then, analyzes the ILEA walking using the prosthetic foot and sprinting using RSP. We develop models that are combinations of human and prostheses by individualizing a linkage structure and inertial parameters of the digital human model. Then, locomotion of ILEA is analyzed based on measurements with optical motion capture system and force plates, and kinematics and dynamics computation. This modeling and computational technique can be applied to the locomotion of ILEA as well as a human motion using tools, and expanded to an analysis and improvement of system involving human.

A Forefoot Strike Requires the Highest Forces Applied to the Foot Among Foot Strike Patterns

Ground reaction force is often used to predict the potential risk of injuries but may not coincide with the forces applied to commonly injured regions of the foot. This study examined the forces applied to the foot, and the associated moment arms made by three foot strike patterns. 10 male runners ran barefoot along a runway at 3.3u2009m/s using forefoot, midfoot, and rearfoot strikes. The Achilles tendon and ground reaction force moment arms represented the shortest distance between the ankle joint axis and the line of action of each force. The Achilles tendon and joint reaction forces were calculated by solving equations of foot motion. The Achilles tendon and joint reaction forces were greatest for the forefoot strike (2u2009194 and 3u2009137 N), followed by the midfoot strike (1u2009929 and 2u2009853 N), and the rearfoot strike (1u2009526 and 2u2009394 N). The ground reaction force moment arm was greater for the forefoot strike than for the other foot strikes, and was greater for the midfoot strike than for the rearfoot strike. Meanwhile, there were no differences in the Achilles tendon moment arm among all foot strikes. These differences were attributed mainly to differences in the ground reaction force moment arm among the three foot strike patterns.