Sprint Motion Research Articles

Detecting people in sprinting motion using HPRDenoise: Point cloud denoising with hidden point removal

<p>LiDARs are utilized in various applications, such as self-driving vehicles and robotics, to aid in sensing the environment. However, LiDARs do not provide instantaneous images and they generate noise, adding to measurement errors. This noise, often referred to as motion blur phenomenon also observed in other imaging sensors results in decreased sensing accuracy for moving objects. This study introduces HPRDenoise, a noise reduction method based on hidden point removal, specifically designed to reduce motion blur during sprinting motion. This method capitalizes on the occlusion produced by a fixed-position LiDAR. We propose a comprehensive denoising approach to filter points from a point cloud without resorting to supervised learning, unlike most existing denoising algorithms. The number of correct frames and accuracy were compared for Raw, ScoreDenoise, which is the state-of-the-art method for random point cloud denoising, and HPRDenoise (Ours). Accuracy is defined as the ratio of the number of correct frames to the total number of frames. Experimental results demonstrate that the detection accuracy of point clouds processed with HPRDenoise is 72.73%, achieving better accuracy than those using conventional methods.</p>

BUILDING A PROFILE OF SPECIFIC FITNESS INDICES FOR MALE TEENAGE CHINESE SPRINTERS

ABSTRACT Objectives: This study aimed to construct a profile of specific fitness indices for male teenage sprinters on the Chinese National Team to provide sprinting fitness assessments for teenage training. Material and Methods: 229 male teenage sprinters at the same level were recruited to participate in this test for the indices. The t- and Kruskal-Wallis tests were conducted for the first selection of fitness indices. In the second selection, principal components analysis was applied to select common factors with greater characteristic values. The fitness indices chosen were height, leg length, measurement B (ankle circumference/heel length×100%) and measurement A (thigh circumference/leg length×100%), hemoglobin, 60m sprint time, 100m sprint time, countermovement jump (CMJ), maximum countermovement jump velocity, CMJ flight time, CMJ maximum force, and CMJ force. Results: Thirteen indices were chosen for the specific fitness of male teenage Chinese male sprinters with 3 general categories and 9 subcategories. The weight of each fitness index was confirmed and used to construct a standard fitness assessment scale. Conclusion: Anthropometric indices indicate the athlete’s innate limits in the structure of the sprinting motion. Physiological indices indicate the athlete’s potential to expend energy and recover in a short time. Motor indices indicate the athlete’s maximum sprinting ability, lower limb reaction strength, power, and maximum strength. Level of evidence II, Diagnostic studies - Investigation of a diagnostic test.

Research on Real-Time Detection of Sprint Error Based on Visual Features and Internet of Things

The current sprint error detection methods do not consider the analysis of the visual characteristics of sprint error, which leads to low detection accuracy, long detection time, and poor detection stability. To overcome this defect, inspired by Internet of Things technology, a real-time sprint error detection method based on visual characteristics is proposed. Based on the basic principle of RFID action perception, the original phase data is preprocessed, the channel parameters are selected, and the tag layout is optimized to form the action-oriented feature. Based on the three-dimensional visual features, the three-dimensional coordinate points of the sports field are determined, and the movement features of the sprint are extracted and formally described. Based on the analysis of the visual characteristics of sprint errors, the block pheromones of single frame sprint motion edge contour are obtained for clustering, and the sprint errors’ feature information is obtained and filtered. Sift technology is used to obtain the boundary contour line and implement the corner characteristics. The Hessian matrix of contour wave domain edge detection is used to calculate the contour wave domain matrix of the image and draw the contour curve of the image of sprint error action to realize the detection of sprint error action. The experimental results show that the proposed method has good stability and can effectively improve the detection accuracy and shorten the detection time.

Matching of sprint performance videos focusing on the motion periodicity and the speed linearity

We present a method to analyze the sprinter's form in 100 m sprint races. To achieve good time records, sprinters should know the problem on their sprint form, for example, by analyzing the difference between good and bad forms. The proposed method captures two performance videos at different points (e.g., 50 and 90 m) in one 100 m sprint race, and matches them frame‐by‐frame to compare the two sprint forms. The method calculates the sprint motion similarity from body keypoints, and then matches video frames focusing on the periodicity of sprint motion and the linearity of sprint speed. We conducted experiments with performance video pairs for six sprinters, and confirmed that the proposed method could match them accurately, which showed the effectiveness and the usefulness of the method. Also, the coach of our track‐and‐field team could find some improvements of the sprinters by referring to the outputs of the method. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Kinetic and kinematic synchronization between blind and guide sprinters

ABSTRACT This study aimed to evaluate the magnitude of synchronization and symmetry between blind and guide sprinters. Elite and sub-elite pairs of male blind sprinters and guide sprinters performed maximal effort 60-m sprints, during which ground reaction force (GRF) for a 50-m distance and sprinting motion during the initial acceleration and maximal speed phases were measured. While there were no significant differences in spatiotemporal and GRF variables between the sprinters of the elite pair, flight time and braking, propulsive and vertical forces in the sub-elite pair showed a significant difference between the sprinters. During the initial acceleration phase, although thigh segment angles in the sagittal plane between the blind and guide sprinters showed obvious phase shifting (lag = −0.078 and −0.088) for the sub-elite pair, the elite pair showed no phase shift and high cross-correlation coefficients (0.96 and 0.83) for the corresponding variable. During the maximal speed phase, for both the elite and sub-elite pairs, there were trivial lags (−0.004 to 0.008) and high cross-correlation coefficients (>0.98) between the thighs of the blind and guide sprinters for both legs. The results demonstrate that a higher magnitude of synchronization between blind and guide sprinters is possibly important for better blind sprint performance.

A warm-up performed with proper-weight sandbags on the leg improves the speed and RPE performance of 100 m sprint in collegiate male sprinters.

Muscle performance can be notably improved following a preloading maximal or near maximal stimulus due to the induction of postactivation potentiation, but the success of a preloading exercise in generating a postactivation potentiation response depends on the balance between fatigue and potentiation. However, the optimal warm-up strategy for sprint runners before a match may be not well established until now. Fifteen well-trained male sprint runners performed four different warm-up protocols: warm-up with 0% body mass; warm-up with 2% body mass; warm-up with 4% body mass; warm-up with 8% body mass. The weight-bearing sandbag was tied about 3~5 cm above each ankle joint. During the 100-meter test, the time and rating of perceived exertion (RPE) in the first 30 meters, time in the first 60 meters, and time in the 100 meters were recorded, respectively. Two-high-speed digital video cameras were separately set in the sagittal planes on the left side of a line drawn at a distance of 30 m and 60 m from the start line to record the sprint motion. A warm-up performed with a sandbag weighted 4% of body mass could significantly improve the time and the RPE score of 100 m sprint by improving average velocity, stride frequency, average stride length, and average accelerated velocity during the sections of 0~30 m, 30~60 m and 60~100 m. This positive effect was better than that of 2% body-weigh effect. However, a warm-up performed with a sandbag weighted 8% of body mass had no significant influence on the performance of a 100 m sprint. Current results indicated that a warm-up performed with proper-weight(4% body mass) sandbags on the leg was beneficial to the improvement of 100 m sprint performance, and the mechanism might be that it effectively activated the main muscles and neuromuscular regulation of running and produced a better postactivation potentiation.

Comparison between sprint coaches and non-specialized physical education elementary school teachers with regard to sprint motion focusing points

Comparison between sprint coaches and non-specialized physical education elementary school teachers with regard to sprint motion focusing points

The relationship between sprint speed and sprint motion in amputee soccer players

Sprint performance plays an important role in amputee soccer. Sprint motion such as step length and frequency are generally accepted as one of the determining factors of sprint performance. However, there is a paucity of sprint motion studies. Here we sought to analyze sprint motion in outfield positioned amputee soccer players using crutches and to clarify the relationship between sprint speed and sprint motion. Twelve male Japanese outfield players participated; they performed a 30-m sprint with maximum effort. Sprint times and speeds were recorded using electronic timing gates. A high-speed video camera recorded sprint motion. The time and distance of each crutch and step were determined via image analysis. Sprint speed was significantly positively correlated with body mass (r=0.692, p=0.013), length and frequency of one running cycle(r=0.817, p=0.001; r=0.666, p=0.018, respectively), 1st-2nd step length (r=0.890, p=0.001), and crutch-1st step length (r=0.659, p=0.020). In addition, sprint speed was significantly negatively correlated with time taken for each 10-m interval as well as with contact time of first foot (r=-0.881, p=0.001) and crutch stance time (r=-0.670, p=0.017). Our results suggest that improving sprint speed requires increasing the step length within a shorter time frame in first foot step and crutch stance.

Kinematics of Maximal Speed Sprinting With Different Running Speed, Leg Length, and Step Characteristics.

This study aimed to provide multiple regression equations taking into account differences in running speed, leg length, and step characteristics to predict kinematics of maximal speed sprinting. Seventy-nine male sprinters performed a maximal effort 60-m sprint, during which they were videoed through the section from the 40- to 50-m mark. From the video images, leg kinematic variables were obtained and used as dependent variables for multiple linear regression equation with predictors of running speed, leg length, step frequency, and swing/support ratio. Multiple regression equations to predict leg kinematics of maximal speed sprinting were successfully obtained. For swing leg kinematics, a significant regression model was obtained to predict thigh angle at the contralateral foot strike, maximal knee flexion and thigh lift angular velocities, and maximal leg backward swing velocity (adjusted R2 = 0.194–0.378, medium to large effect). For support leg kinematics, a significant regression model was obtained to predict knee flexion and extension angular displacements, maximal knee extension velocity, maximal leg backward swing angular velocity, and the other 13 kinematic variables (adjusted R2 = 0.134–0.757, medium to large effect). Based on the results, at a given leg length, faster maximal speed sprinting will be accompanied with greater thigh angle at the contralateral foot strike, greater maximal leg backward swing velocity during the swing phase, and smaller knee extension range during the support phase. Longer-legged sprinters will accomplish the same running speed with a greater thigh angle at contralateral foot strike, greater knee flexion range, and smaller maximal leg backward swing velocity during the support phase. At a given running speed and leg length, higher step frequencies will be achieved with a greater thigh angle at contralateral foot strike and smaller knee flexion and extension ranges during the support phase. At a given running speed, leg length and step frequency, a greater swing/support ratio will be accompanied with a greater thigh angle at contralateral foot strike and smaller knee extension angular displacement and velocity during the support phase. The regression equations obtained in this study will be useful for sprinters when trying to improve their maximal speed sprinting motion.

Effects of slope inclination on sprinting motion

Effects of slope inclination on sprinting motion

Optimality Studies of Human Sprinting Motions with and Without Running-Specific Prostheses

Due to the remarkable performances of some amputee athletes, the power of their running-specific prostheses came to the fore of the discussions. The aim of our study was to compare non-amputee and amputee sprinting motions resulting from optimization using combinations of eight optimality criteria with either fixed or free average velocity. For the description of the amputee and the non-amputee athlete, we created rigid multi-body system models with 16 degrees of freedom in the sagittal plane. Each sprinting motion is the solution of a specific optimal control problem with periodicity and dynamic constraints. We found realistic human-like sprinting motions for both the non-amputee and the amputee athlete. We compared the optimized solutions to dynamics-reconstructed solutions from motion capture data and determined similarity measures for each of them. The investigation of the amputee athlete’s joint torques and ground reaction forces revealed that the real amputee athlete does not exploit the functionality of his running-specific prosthesis as much as the model. The optimal control problems with free average velocity generated human-like sprinting motions as well. However, for specific objective functions the velocities exceed the fastest measured velocities in human sprinting.

Effects of an instructional program for 5th and 6th grade children with negative feelings toward sprinting

This study was performed to devise an instructional program for children who were not good at sprinting and to verify the program’s effectiveness for improvement of sprinting ability and motion. The participants were 19 upper grade elementary school children who were not good at sprinting. The program included 2 drills with some teaching devices and running on flat markers. The children attended the program for 8 days (2 days per week) and each lesson lasted an hour. In order to validate the program outcome, sprint time (50 m), interval speed (every 10 m), average speed, maximal speed, rate of speed decline, interval and average step frequency and step length were analyzed, and sprint motions were evaluated. The results were as follows: 1) Most of the children’s 50 m times were below the national average. This suggested that their negative feelings toward sprinting resulted from the realization that they were unable to run as fast as other children. 2) The children’s sprint times were improved after the program, and a significant correlation between pre-time and post-pre time was revealed. It was also found that the greater the increase in the children’s step frequency, the faster their sprint times became. These results suggest that sprinting instruction allows low-performing children to increase their step frequency and improve their sprint times. 3) The main aim of the program was to improve children’s sprint motions in the mid sprint phase, and the participants practiced start motions only twice during the program. As a result, speeds from the start to 10 m, 20-50 m, and maximum speed were increased significantly by this practice, suggesting that significant changes of speed led to improvement of the sprint times. 4) Participants became able to swing back their leg under their body and to make contact with the ground with the middle or front of the foot. Therefore it was considered that the drills and running on flat markers with teaching devices were valuable for improving the children’s sprint motions. 5) Although the scissors-like leg motion was not improved by practice with a color board and bells, the kneefolding motion of the swing leg did appear to be improved. Therefore, the children seemed to acquire basic skill in more rapid scissors-like leg motion. These results suggest that our instructional program was effective in enabling children to improve their sprinting ability and motion. However, additional research focusing on aspects such as the relationship between sprinting ability and sprint motion, or individual feelings and motor competency in the context of sprinting, will be needed.

Differences in sprinting performance and kinematics between preadolescent boys who are fore/mid and rear foot strikers.

The purpose of this study was to clarify whether foot strike patterns are associated with different sprint performance and kinematics in preadolescent boys. The study enrolled 24 healthy 10–11-year-old boys in the fifth grade at public elementary schools in Japan. The participants performed the 50-m sprint with maximum effort. Sprint motion was recorded using a high-speed video camera (120 fps) placed in the sagittal plane on the left side of a line drawn at 35-m from the start line. Kinematic variables were calculated based on manually digitized body landmark coordinates. The participants were categorized into two groups according to their foot strike pattern (rearfoot strikers, RF group, n = 12; forefoot or midfoot strikers, FF/MF group, n = 12). The time taken to complete the 50-m sprint in the FF/MF group (9.08±0.52 s) was faster than that in the RF group (9.63±0.51 s). The FF/MF group had greater sprint speed, higher step frequency, and shorter foot contact time than the RF group. Regarding the association between foot strike pattern and sprint kinematics, we found that the RF group had a greater range of knee flexion during the support-leg phase, whereas the FF/MF group had shorter horizontal distance from the heel of the support leg to the centre of mass at the touchdown, greater maximal knee flexion velocity during the swing-leg phase, and higher the maximum hip extension velocity during the support-leg phase. The current results suggested that, in preadolescent boys, forefoot or midfoot strike (rather than rearfoot strike) is effective for obtaining a higher step frequency and sprint speed through greater magnitude of knee flexion and hip extension movement velocities during the swing and support phases, respectively. The current findings will be useful for understanding the characteristics of the development of sprinting performance in preadolescent children.

Can forward dynamics simulation with simple model estimate complex phenomena?: Case study on sprinting using running-specific prosthesis

Surpassing the world record in athletic performance requires extensive use of kinematic and dynamic motion analyses to develop novel body usage skills and training methods. Performance beyond the current world record has not been realized or measured; therefore, we need to generate it with dynamics consistency using forward dynamics simulation, although it is technologically difficult because of the complexity of the human structure and its dynamics. This research develops a multilayered kinodynamics simulation that uses a detailed digital human model and a simple motion-representation model to generate the detailed sprinting performances of individuals with lower extremity amputations (ILEAs) aided by carbon-fiber running-specific prostheses (RSPs), which have complex interactions with humans. First, we developed a digital human model of an ILEA using an RSP. We analyzed ILEA sprinting based on experimental motion measurements and kinematics/dynamics computations. We modeled the RSP-aided ILEA sprinting using a simple spring-loaded inverted pendulum model, comprising a linear massless spring, damper, and mass, and we identified the relevant parameters from experimentally measured motion data. Finally, we modified the sprint motion by varying the parameters corresponding to the RSP characteristics. Here, the forward dynamics have been utilized to simulate detailed whole-body sprinting with different RSP types (including simulated RSPs not worn by the subject). Our simulations show good correspondence with the experimentally measured data and further indicate that the sprint time can be improved by reducing the RSP viscosity and increasing stiffness. These simulation results are validated by the experimentally measured motion modifications obtained with different types of RSPs. These results show that the multilayered kinodynamics simulation using the detailed digital human model and the simple motion-representation model has the capacity to generate complex phenomena such as RSP-aided ILEA sprinting that contains complex interactions between the human and the RSP. This simulation technique can be applied to RSP design optimization for ILEA sprinting.

スプリント加速走における支持脚関節機能の距離による変化

スプリント加速走における支持脚関節機能の距離による変化

J2310105 スプリント走最大速度局面における遊脚関節機能の定量化

The purpose of this study was to quantify the functional roles of the swing leg joints during maximal velocity phase in sprint motion based on multi-body dynamics. Five male sprinters (height: 1.74±0.03m, body mass: 66.6±4.7kg, personal best time in the 100m: 10.9±0.27s) from a university track team performed 60m maximal sprints on a straight track in this experiment. Video data were recorded using three high-speed digital cameras (EXILIM-EX-F1, CASIO) operating at 300fps. Two dimensional kinematic and kinetic data of the participants sprinting around 50m were analyzed by using the trajectory of 25 landmarks of the body. In order to quantify the roles of primary joints such as hip and knee joints, which exert large joint torque, ankle joint input was treated as angular acceleration instead of joint torque. The results indicated that 1) this method enabled us to quantify the joint function of the swing leg in sprint, 2) the main generating factor of the swing leg motion was hip joint torque, and 3) ankle joint torque was necessary to control the orientation of the foot segment.

A-23 スプリント加速局面における支持脚関節トルクの機能および機序(ロコモーションとシューズ2)

A-23 スプリント加速局面における支持脚関節トルクの機能および機序(ロコモーションとシューズ2)

小学生男子と成人男性との全力疾走時における動作の違い

小学生男子と成人男性との全力疾走時における動作の違い

Influences of lower limb muscle thickness on sprint motion in childhood

Influences of lower limb muscle thickness on sprint motion in childhood

走行タイムの速い子どもに見られる疾走動作の特徴

走行タイムの速い子どもに見られる疾走動作の特徴