High-speed Running Research Articles

Analysing the physical output of international field hockey players through the lens of the phase of play

The purpose of this study was to describe the locomotor activity of men's hockey based on the phase of play and to identify if differences in locomotor activity exist between phases. Twenty-four players (age 26 ± 4) wore a 10 Hz Global Positioning System device to track locomotor activity during 10 international matches. The locomotor activity of players was allocated to five different phases: (1) established attack, (2) opposition counterattack, (3) established defence, (4) attacking counterattack and (5) offensive pressing, utilising a video analysis-based system. Linear mixed models and post-hoc pairwise comparisons, using estimated marginal means, were utilised to compare the locomotor activity in each phase of play within each position. Significant main effects were found for the phase of play on several locomotor activity metrics ( p ≤ 0.05). With respect to max speed and relative total distance across positions, counterattacks present a unique challenge compared to other phases. Established attack phases evoke lower max speed values than offensive pressing phases for all playing positions as well as compared to opposition counterattacks for defenders, midfielders, and forwards. Positional differences existed during attacking counterattack phases, with defenders producing lower values than both midfielders and forwards for high-speed running, high-speed running efforts, max speed and relative total distance. Depending on the metric, this approach captured 22%–70% of a player's locomotor activity providing valuable insight into the current dynamics of international hockey. This investigation demonstrated positional differences based on the phase of play, which may explain previous research findings regarding positional differences.

Progressive daily hopping exercise improves running economy in amateur runners: a randomized and controlled trial

This study investigated the effects of a daily plyometric hopping intervention on running economy (RE) in amateur runners. In a randomized, controlled trial, thirty-four amateur runners (29 ± 7 years, 27 males) were allocated to a control or a hopping exercise group. During the six-week study, the exercise group performed 5 min of double-legged hopping exercise daily. To progressively increase loading, the number of hopping bouts (10 s each) was steadily increased while break duration between sets was decreased. Pre- and post-intervention, RE, peak oxygen uptake (VO2peak), and respiratory exchange ratio (RER) were measured during 4-min stages at three running speeds (10, 12, and 14 km/h). ANCOVAs with baseline values and potential cofounders as cofactors were performed to identify differences between groups. ANCOVA revealed an effect of hopping on RE at 12 km/h (df = 1; F = 4.35; p < 0.05; η2 = 0.072) and 14 km/h (df = 1; F = 6.72; p < 0.05; η2 = 0.098), but not at 10 km/h (p > 0.05). Exercise did not affect VO2peak (p > 0.05), but increased RER at 12 km/h (df = 1; F = 4.26; p < 0.05; η2 = 0.059) and 14 km/h (df = 1; F = 36.73; p < 0.001; η2 = 0.520). No difference in RER was observed at 10 km/h (p > 0.05). Daily hopping exercise is effective in improving RE at high running speeds in amateurs and thus can be considered a feasible complementary training program.Clinical trial registration German Register of Clinical Trials (DRKS00017373).

Match Outcome and Running Performance Among UEFA Champions League Soccer Players

This study aimed to examine position-specific differences in running performance (RP) according to the match outcome in UEFA Champions League (UCL). The players’ RPs (n=244) were collected during UCL group stage matches (n=20) in the 2020/21 season using semiautomatic optical system InStat Fitness, and classified according to their playing positions as: central defenders (CD; n=79), fullbacks (FB; n=65), central midfielders (CM; n=55), wide midfielders (WM; n=28) and forward (FW; n=17). The RP variables included: total distance covered, low-intensity (LIR) (&lt;14.3km/h), running (14.4–19.7 km/h), high-speed running (HSR) (19.8–25.1 km/h), and sprinting (&gt;25.2 km/h). Match outcome was observed as win, draw and loss. One-way analysis of variance (ANOVA) was used to examine differences in RP according to the match outcome. Significant differences in TD (F-test=4.16, p=0.02) and LIR (F-test=4.51, p=0.01) among match outcomes were observed for FBs. Specifically, FBs covered significantly greater TD when their team won than when lost (p=0.03, d=0.79). In addition, FBs’ LIR was significantly greater in won matches than in drew (p=0.04, d=0.92) and lost matches (p=0.03, d=0.77). The RP of players on all other playing position were similar irrespective to the match outcome (F-test=0.08 to 2.84, all p&gt;0.05). These results indicated that winning UCL matches is not strongly influenced by players’ physical performance, except for FBs who tended to covered greater total- and low- distance when their teams won. This study indicated limited overall influence of RP on success in matches at elite-level soccer. The findings from this study may help soccer coaches to ensure optimal physical preparation of players in elite soccer.

Activity distribution among the hamstring muscles during high-speed running: A descriptive multichannel surface EMG study.

This study assessed activity distribution among the hamstring muscles during high-speed running. The objective was to compare within and between muscle activity, relative contribution and hip and knee joint angles at peak muscle activity during high-speed running. Through multichannel electromyography, we measured muscle activity in male basketball players during high-speed running on a treadmill at 15 locations: five for biceps femoris long head, four for semitendinosus, and six for semimembranosus. Muscle activity was calculated for each location within each hamstring muscle individually for each percent of a stride cycle. Twenty-nine non-injured basketball players were included (mean age: 17 ± 1 years; mass, 85 ± 9kg; height, 193 ± 9cm). Heterogeneous activity was found for all individual hamstring muscles across multiple events of the stride cycle. In the late-swing phase, muscle activity and relative contribution of the semimembranosus was significantly higher than of the semitendinosus. There was no significant difference in hip and knee joint angles at instant of peak muscle activity, assessed locally within individual hamstring muscles, as well as in general over the whole hamstring muscle. Hamstring muscles were most active in the late-swing phase during high-speed running. In this phase, the semimembranosus was most active and the semitendinosus was least active. Within the biceps femoris long head, the most proximal region was significantly more active in the late-swing phase, compared to other muscle regions. For each muscle and location, peak muscle activity occurred at similar hip and knee joint angles.

Vertical and lateral random vibration of high-temperature superconductor maglev under high-speed operation conditions

High-temperature superconductor (HTS) maglev systems shows significant potential to be applied to high-speed rail transportation based on its passive stable levitation owing to the coupling between the HTS bulks and permanent magnetic guideway (PMG). As one of the key factors to guarantee the safe and stable operation of HTS maglev, the dynamic characteristics of the HTS bulks reflecting the operational performance of the HTS maglev system under high-speed running conditions should be focused on. Therefore, this paper, based on H-formulation, established a finite element model of an HTS-PMG system, and assessed its feasibility by experiments. Moreover, the random free vibration of the HTS bulk caused by guideway random irregularity at high speed is also studied by this validated model. The random vibration characteristics and temperature variation of the HTS bulk at three high speeds (600 km h−1, 800 km h−1, and 1000 km h−1) under vertical vibration, lateral vibration, and vertical-lateral coupling vibration, respectively, are compared. The results show that at high speed, vertical vibration can only cause the fluctuation of levitation height, while lateral vibration and vertical-lateral coupled vibration will affect both lateral offset and levitation height. Compared with the mere vertical or lateral vibration mode, the levitation height attenuation and temperature rise of the coupling vibration mode is greater due to more energy loss caused by magnetic flux motion, but it can aid in the suppression of the vibration in the vertical and lateral directions. The increase of velocity intensifies the vibration strength of the HTS bulk and increases the fluctuation of the levitation height, lateral offset, and temperature rise. However, vibrations at a certain high speed causes a limited temperature rise and thus a limited influence on the bulk performance, and the HTS bulk is still in the safe operating range at a maximum speed of 1000 km h−1. These conclusions are anticipated to provide some references for future high-speed applications of the HTS maglev system.

Moving Model Experimental Study on a Slipstream of a High-Speed Train Running on the Bridge Suffering a Crosswind

A running train induces a slipstream around it, which is closely related to its aerodynamic features and crucial for the safety of people and structures near the track. However, the effect of crosswinds is almost inevitable when the train runs on a bridge. In this work, an experimental study using moving model testing technology was conducted to investigate the effects of wind speeds, train speeds, and yaw angles on the aerodynamic performance of a Fuxing Hao high-speed train running on a bridge under the influence of crosswind. The results show that, for the crosswind cases, the slipstream velocities on the leeward side of the train are generally higher than those in the no-crosswind cases. Moreover, the results were compared for the cases with the same effective yaw angle of 21.8° but different wind speeds (6 m/s, 8 m/s) and train speeds (15 m/s, 20 m/s), which suggests the method of the resultant wind’s yaw angle is no longer valid when the train runs on a bridge due to the aerodynamic interactions.

Power Autonomy and Agility Control of an Untethered Insect-Scale Soft Robot.

It is still challenging to achieve agility and trajectory control for untethered soft robots on an insect scale given their low mechanical impedance and compact structures. In this study, fast translational movements and swift turning motions are demonstrated on a power autonomous soft robot with a piezoelectric-thin-film-actuated body and electrostatic turning footpads. A high relative running speed of 2.5 body length per second compared with existing untethered robots is realized on a 24-mm-long untethered prototype integrated with power source, control, and wireless communication modules. An arc-shaped leg structure is adopted to self-regulate the frication forces on different footpads during turning by an inclination-induced redistribution of the payload gravity on legs and footpads. The trajectory maneuverability is demonstrated by navigating a 380 mg robot prototype with an 1810 mg payload to pass through a 58-cm-long S-shaped path with wireless control in 43.4 s. Due to the flexibility of the all-polymer body structure, the robustness of the untethered robot to large strain is demonstrated when compressed by 91 times the weight of the robot. A maximum travel distance of 58.6 m is achieved for the robot equipped with a 40 mA·h lithium battery, corresponding to the cost of transport of 261. This work provides a feasible solution to achieve high agility and advance the practicability of untethered soft robots on an insect scale.

High-speed running and sprinting in professional adult soccer: Current thresholds definition, match demands and training strategies. A systematic review.

The aims of this systematic review were (1) to summarize the evidence on absolute velocity thresholds used to classify high-speed running and sprinting, (2) to examine the existing evidence about the individualized thresholds approach, (3) to describe high-speed and sprint running distance match demands, and (4) to provide training strategies for eliciting HSR and sprinting during training sessions in professional adult soccer. This systematic review was conducted following the PRISMA 2020 guidelines. After the authors' screening, 30 studies were included in this review. This review found that, to date, there is no consensus on the absolute thresholds defining high-speed and sprint running in adult soccer players. Until international standards are defined, it is reasonable to set absolute thresholds considering the range of values found in the literature collected in this review. Relative velocity thresholds could be considered for specific training sessions whose goal is to reach near maximal velocity exposure. During official matches, high-speed and sprint running distances ranged from 911 to 1,063 m and 223-307 m, respectively, in professional female soccer players, while ranges from 618 to 1,001 m and 153-295 m, respectively, in professional male soccer players. During training, game-based drills designed in formats using relative areas per player greater than 225 m2 and 300 m2 appear to be adequate for achieving high-speed running and sprinting exposure, respectively, for male players. The combination of game-based, running exercises and soccer circuit-based drills is advisable to ensure adequate high-speed and sprint running exposure both at a team and individual level.

The effectiveness of two comprehensive recovery protocols on performance and physiological measures in elite soccer players: A parallel group-randomized trial

Elite soccer players consistently report using several recovery methods after practices and games. However, it is unclear how their subsequent performance could be enhanced using broad protocols. The aim of this study was to compare the effectiveness of two different comprehensive recovery protocols in physiological, neuromuscular, and perceptual outcomes. Eighteen Mexican National Team players (19.56 ± 0.62 years) were recruited. Using a randomized parallel group design, players followed one of two recovery protocols: (a) carbohydrate and protein shake, foam roller, cold-water immersion, and tart cherry juice concentrate ( n = 9) or (b) carbohydrate and protein shake, stretching, and intermittent cold-water immersion ( n = 9) following the completion of an unofficial game and the day after. Muscular creatine kinase, countermovement jump, hamstring maximal voluntary contraction, perceived recovery, and muscle soreness were assessed before, immediately after, and 20-44-68 h post-game. Significant effects (set at ρ≤0.05) of time were present in both interventions. Muscular creatine kinase was normalized entirely at 68 h post-game, while neuromuscular and perceptual outcomes were homogenized at 44 h. No statistically significant effects between protocols were found. Still, the interaction effects showed changes only in the group using protocol (a) at post-game and 20 h after in neuromuscular and muscle soreness. There were large correlations between muscular creatine kinase and accelerations, decelerations, sprints, and high-speed running distances. In conclusion, the interventions are equally effective for improving physiological, neuromuscular, and perceptual outcomes. Thus, elite soccer players may benefit from different combinations of methods after practices or games to obtain positive effects on recovery after them.

Unbalanced vibration control of active magnetic bearing using an active disturbance rejection notch decoupling technique

Aiming at the position coupling, gyroscopic effect, and synchronized vibration caused by the unbalance mass in the magnetic bearing rotor, a linear active disturbance rejection notch decoupling control method is proposed. Firstly, a model with coupling and unbalanced vibration of the system was established. The terms of position coupling, gyroscopic effect, and unbalanced vibration in the system are estimated by Extended State Observer and the estimator is treated as the system disturbance to be compensated, then the radially existing coupled and unbalanced vibration systems are decoupled into four independent second-order series-integrated subsystems. The nonlinear state error feedback control law is designed to implement the decoupling control of each subsystem. For the problem of unbalanced vibration of the rotor after decoupling, the suppression method of the dynamic unbalanced force of the same frequency notch filter is designed, and then the closed-loop feedback structure of the new method is deduced, and its frequency characteristics are analyzed. Then the rules and principles of controller parameter selection are summarized using Bode diagram. The simulation results show that the designed linear active disturbance rejection notch decoupling controller not only achieves the decoupling control of the respective degrees of the magnetic bearing rotor but also suppresses the unbalanced vibration of the rotor. At the same time, it solves the influence of the gyroscopic effect on the control under the high-speed running of the magnetic bearing rotor.

The Efficacy of a Multimodal Recovery Strategy Implemented After a High-Intensity Rugby League Training Session.

Aben, HGJ, Hills, SP, Higgins, D, Cooke, CB, Davis, D, Jones, B, and Russell, M. The efficacy of a multimodal recovery strategy implemented after a high-intensity rugby league training session. J Strength Cond Res 37(8): 1634-1642, 2023-The efficacy of a multimodal recovery strategy implemented within 4 hours of rugby league (RL) training was investigated using repeated-measures, randomized, crossover methods in 10 professional academy RL players (age: 17 ± 1 years). Following standardized training (5,383 m covered, 350-m high-speed running, 28 repeated high-intensity efforts, 24 collisions), players completed a multimodal recovery (REC) strategy (i.e., ∼640 kcal meal + ∼1,285 kcal snacks or drinks, cold-water immersion, sleep hygiene recommendations) or control (i.e., ∼640 kcal meal: CONT) practices. Isometric mid-thigh pulls (IMTP), countermovement jumps (CMJ), and wellness questionnaires were completed before (-3 hours) and after (+24, +48 hours) training. The recovery strategy influenced IMTP peak force ( p = 0.026), but between-trial differences were undetectable. No other between-trial effects (all p > 0.05) were seen for IMTP, CMJ, or wellness variables. Training-induced reductions in CMJ peak power (-4 ± 6% vs baseline: 4,878 ± 642 W) at +24 hours ( p = 0.016) dissipated by +48 hours. Fatigue and lower-body soreness reduced by 16 ± 19% ( p = 0.01) and 32 ± 44% ( p = 0.024) at +48 hours versus +24 hours, respectively. Relative to CONT (i.e., posttraining nutrition), the effects of a single bout of recovery practices appeared limited when implemented after RL-specific training. Therefore, when training included limited collisions, balanced postexercise meals appeared equally effective relative to a multimodal recovery strategy. Transient changes in performance and wellness variables after training may have implications for practitioners. Consecutive training sessions, including a high frequency and intensity of eccentric muscle actions, should be carefully planned, especially near match-play.

A Novel Multiresonant Chipless RFID Tag for Directional Strain Measurement on Metal Surface

In this article, a radio frequency identification (RFID) sensor tag for real-time health monitoring of the magnitude and direction of metal surface strain is presented. The chipless RFID sensor tag is composed of metal foil and F4B substrate, which is low-cost and works stably in harsh environments for a long time. Through highly sensitive strain monitoring, the risk can be predicted in the early stage of defect generation. The proposed tag includes a C-type resonator array, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> -type transmission line, and tag antennas. The C-type resonator has different sensitivities in the electrical length direction and width direction. Then, based on this characteristic, the resonator array creates a plurality of characteristic signatures containing strain information by optimizing the geometric parameters of the resonators. The strain information is transmitted to the tag antenna through the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> -type transmission line to complete the wireless communication between the tag and the reader. Finally, the performance of the strain monitoring system is verified by an experimental study. The experiment shows that the average sensitivity of the resonators is −4.94 and 1.14 kHz/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> in the electric length and width directions, respectively. When the strain is more than 150 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> , the relative error of magnitude is less than 12.7% and the absolute error of direction is less than 13.3°. Therefore, the proposed chipless RFID tag can monitor the amplitude and direction of strain with higher sensitivity and a simpler structure, for the key structures, such as the high-speed running gear.

Innovation-Superposed Simultaneous Localization and Mapping of Mobile Robots Based on Limited Augmentation

In this paper, Aaiming at the problem of simultaneous localization mapping (SLAM) for mobile robots, a limited-augmentation innovation superposition (LAIS) is proposed to solve the problems occurring in SLAM. By extending the single-time innovation superposition to multi-time innovation, the error accumulation during the movement of mobile robots is reduced and the accuracy of the algorithm is improved. At the same time, when the number of feature points observed by the sensor exceeds the threshold, the sensor range is restricted. Therefore, only the qualified feature points are added to the system state vector, which reduces the calculation amount of the algorithm and improves the running speed. Simulation results show that compared with other algorithms, LAIS has higher accuracy and higher running speed in environmental maps with a different number of landmark points.

Training Load Within a Soccer Microcycle Week—A Systematic Review

ABSTRACT Quantifying training load is important to ensure that athletes correctly respond to training prescription and reduce injury risk. Training load can be divided into internal training load, the response of an individual to the training demand, and external training load, the physical “work” of the players. We aimed to analyze training load during a training week (microcycle) in soccer players. Systematic searches of 3 electronic databases (PubMed, SPORTDiscus, and Web of Science) were conducted, and Preferred Reporting Items for Systematic Review and Meta-analysis guidelines were followed. From 1,718 studies initially found, 16 were selected after screening. Descriptive and Z-score analyses were performed for each variable (acceleration and deceleration [DEC], average speed, high-speed running, sprint, total distance, player load, percentage of maximal heart rate, and rating of perceived exertion [RPE]). A sample of this review was 317 male soccer players aged 16.4–27.6 years, competing in elite, professional, and youth levels. Three days prior to match day was the most demanding session of the week, except for DEC, average speed, and player load demands. The day prior to match day was the least demanding session, except for sprint and RPE. In conclusion, midweek sessions can be chosen to apply higher training loads, whereas training sessions immediately before and after the match can be used to taper or recover.

A low-power reconfigurable memristor for artificial neurons and synapses

With the advancement of artificial intelligence technology, memristors have aroused the interest of researchers because they can realize a variety of biological functions, good scalability, and high running speed. In this work, the amorphous semiconductor material silicon carbide (SiC) was used as the dielectric to fabricate the memristor with the Ag/SiC/n-Si structure. The device has a power consumption as low as 3.4 pJ, a switching ratio of up to 105, and a lower set voltage of 1.26 V, indicating excellent performance. Importantly, by adjusting the current compliance, the strength of the formed filaments changes, and the threshold characteristic and bipolar resistance switching phenomenon could be simultaneously realized in one device. On this basis, the biological long- and short-term memory process was simulated. Importantly, we have implemented leakage integration and fire models constructed based on structured Ag/SiC/n-Si memristor circuits. This low-power reconfigurable device opens up the possibilities for memristor-based applications combining artificial neurons and synapses.

A Novel Carbide-Free Bainitic Heavy-Haul Wheel Steel with an Excellent Wear-Resistance under Rolling-Sliding Condition

With the rapid development of railways towards high speed and larger carrying capacity, the problem of wear and fatigue damage between wheel/rail is gradually becoming serious. However, traditional pearlite wheel/rail has reached the limit, which leads to more attention to developing a novel wheel/rail material. This study aims to report a novel carbide-free bainite wheel steel. The wear-resistance of novel steel was tested by a rolling-sliding wear experiment under heavy-haul condition and investigated the impacts of the running speeds on the damage mechanism of wear and fatigue. The results show that the yield strength of the bainite wheel was as high as 950 MPa and the hardness was 415 HV, which was superior to most of the reported typical wheel steel. During the process of wear, the surface damage of the wheel was mainly adhesive wear and fatigue damage, and the gradient strain layer (GS layer) was formed on the wheel surface. As the running speed increased, fatigue damage gradually became more serious than adhesive wear, and the shear stress and strain of the GS layer were enhanced. The higher thickness and hardening were produced on the GS layer, which is the main reason for the higher wear-resistance of the bainitic wheel under higher running speeds. In addition, the wear-resistance of the novel wheel steel was better than that of the reported wheel steel. This novel bainitic wheel is a promising wheel for heavy-haul condition applications, which could provide a guide in choosing bainitic wheel steel for the railway.

Replicating Maximum Periods of Play in Australian Football Matches Through Position-Specific Drills.

Wing, C, Hart, NH, Ma'ayah, F, and Nosaka, K. Replicating maximum periods of play in Australian football matches through position-specific drills. J Strength Cond Res 37(8): 1628-1633, 2023-This study evaluated whether a position-specific drill replicates the running intensities of maximum ball in play (BiP) phases in competitive matches of Australian football (AF). Match data were collected on 32 AF players across 3 seasons (2019, 2020, 2021), with training session data collected from the same players across the 2021 season. Three position-specific training drills were created for defense, offense, and combination (defense and offense combined). Running intensities were compared between maximum BiP periods (e.g., periods with the highest metric per minute) from competitive matches and position-specific training drills, as well as between the 3 position-specific training drills using linear mixed models. The significance level was set at p < 0.05. Measures of distance (offense: 44.4 m·minute -1 , defense: 83.5 m·minute -1 , combination: 50.4 m·minute -1 ), high-speed running (offense: 76.7 m·minute -1 , defense: 134.6 m·minute -1 , combination: 89.6 m·minute -1 ), very high-speed running (offense: 26.7 m·minute -1 , defense: 56.2 m·minute -1 , combination: 55.0 m·minute -1 ), and high-intensity efforts (offense: 2.3 efforts·minute -1 , defense: 3.0 efforts·minute -1 , combination: 2.8 efforts·minute -1 ), relative to time were greater ( p < 0.001) in all 3 position-specific training drills compared with BiP phases. All measured metrics were significantly ( p < 0.001) greater in the defense drill compared with the offense drill, whereas distance, high-speed running, PlayerLoad, and accelerations were significantly ( p < 0.001) greater when compared with the combination drill. These demonstrate that position-specific training drills that we created replicated or exceeded the running intensities recorded during matches based on maximum BiP periods. Position-specific training drills seem to be an attractive addition to AF players training regimens because it concurrently provides training for physical and technical actions (e.g., handballs).

Common High-Speed Running Thresholds Likely Do Not Correspond to High-Speed Running in Field Sports.

Freeman, BW, Talpey, SW, James, LP, Opar, DA, and Young, WB. Common high-speed running thresholds likely do not correspond to high-speed running in field sports. J Strength Cond Res 37(7): 1411-1418, 2023-The purpose of this study was to clarify what percentage of maximum speed is associated with various running gaits. Fifteen amateur field sport athletes (age = 23 ± 3.6 years) participated in a series of 55-meter running trials. The speed of each trial was determined by instructions relating to 5 previously identified gait patterns (jog, run, stride, near maximum sprint, and sprint). Each trial was filmed in slow motion (240 fps), whereas running speed was obtained using Global Positioning Systems. Contact time, stride angle, and midstance free-leg knee angle were determined from video footage. Running gaits corresponded with the following running speeds, jogging = 4.51 m·s -1 , 56%Vmax, running = 5.41 m·s -1 , 66%Vmax , striding = 6.37 m·s -1 , 78%Vmax, near maximum sprinting = 7.08 m·s -1 , 87%Vmax, and sprinting = 8.15 m·s -1 , 100%Vmax. Significant ( p < 0.05) increases in stride angle were observed as running speed increased. Significant ( p < 0.05) decreases were observed in contact time and midstance free-leg knee angle as running speed increased. These findings suggest currently used thresholds for high-speed running (HSR) and sprinting most likely correspond with jogging and striding, which likely underestimates the true HSR demands. Therefore, a higher relative speed could be used to describe HSR and sprinting more accurately in field sports.

Position-Specific Running and Technical Demands During Male Elite-Junior and Elite-Senior Australian Rules Football Match-Play.

Jennings, J, Štaka, Z, Wundersitz, DW, Sullivan, CJ, Cousins, SD, Čustović, E, and Kingsley, MI. Position-specific running and technical demands during male elite-junior and elite-senior Australian rules football match-play. J Strength Cond Res 37(7): 1449-1455, 2023-The aim of this study was to compare position-specific running and technical demands of elite-junior and elite-senior Australian rules football match-play to better inform practice and assist transition between the levels. Global positioning system and technical involvement data were collated from 12 Victorian U18 male NAB League ( n = 553) and 18 Australian Football League ( n = 702) teams competing in their respective 2019 seasons. Players were grouped by position as nomadic, fixed, or ruck, and data subsets were used for specific analyses. Relative total distance ( p = 0.635, trivial effect), high-speed running (HSR) distance ( p = 0.433, trivial effect), acceleration efforts ( p = 0.830, trivial effect), deceleration efforts ( p = 0.983, trivial effect), and efforts at >150 m·min -1 ( p = 0.229, trivial effect) and >200 m·min -1 ( p = 0.962, trivial effect) did not differ between elite-junior and elite-senior match-play. Elite juniors covered less total and HSR distance during peak periods (5 seconds-10 minutes) of demand ( p ≤ 0.022, small-moderate effects). Within both leagues, nomadic players had the greatest running demands followed by fixed position and then rucks. Relative disposals ( p = 0.330, trivial effect) and possessions ( p = 0.084, trivial effect) were comparable between the leagues. During peak periods (10 seconds to 2 minutes), elite juniors had less technical involvements than elite seniors ( p ≤ 0.001, small effects). Although relative running demands and positional differences were comparable between the leagues, elite juniors perform less running, HSR, and technical involvements during peak periods when compared with elite seniors. Therefore, coaching staff in elite-senior clubs should maintain intensity while progressively increasing the volume of training that recently drafted players undertake when they have transitioned from elite-junior leagues.

Performance analysis and multi-objective optimization of bionic dendritic furcal energy-absorbing structures for trains

Rail vehicles offer the characteristics of large carrying capacity and high running speed. Train accidents usually result in substantial personal casualties and economic losses. Energy-absorbing structures can efficiently and quickly absorb and disperse the energy generated during collisions. In this paper, the performances with different cross-sections and partings of the bionic dendritic furcal structure (BDFS) inspired by the furcal branch and bifurcation structure of neurons are analyzed and compared by numerical simulation. The simplified super folding element theory and experiments verify that the finite element models are effective. A hybrid multi-stage optimization decision system, i.e., multi-criteria decision-making (MCDM)- multi-objective optimization (MOP)- MCDM, which integrates the VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method, the multiple objective particle swarm optimization-crowding distance (MOPSO-CD) evolutionary algorithm and repetitive VIKOR method, is proposed to find the optimal structure and obtain the optimal parameter alternative of the structure. Comparisons and analyses of experiments and simulations are carried out to verify the effectiveness of the proposed method. The results show that BDFS with six furcal ribs and 3rd-order parting display the best comprehensive crashworthiness under the working condition of 10 m/s specified in EN15227 standard. When the single target requirement is considered, specific energy absorption (SEA) can be increased by 16.18%, peak crushing force (PCF) can be decreased by 67.07%, and undulation of the load-carrying capacity (ULC) can be decreased by 14.02%. This study provides an effective tool for the analysis and optimization of energy-absorbing structures.