Multidimensional Analysis of Physiological Entropy during Self-Paced Marathon Running.

The pacing of a marathon is arguably the most challenging aspect for runners, particularly in avoiding a sudden decline in speed, or what is colloquially termed a "wall", occurring at approximately the 30 km mark. To gain further insight into the potential for optimizing self-paced marathon performance through the coding of comprehensive physiological data, this study investigates the complex physiological responses and pacing strategies during a marathon, with a focus on the application of Shannon entropy and principal component analysis (PCA) to quantify the variability and unpredictability of key cardiorespiratory measures. Nine recreational marathon runners were monitored throughout the marathon race, with continuous measurements of oxygen uptake (V˙O2), carbon dioxide output (V˙CO2), tidal volume (Vt), heart rate, respiratory frequency (Rf), and running speed. The PCA revealed that the entropy variance of V˙O2, V˙CO2, and Vt were captured along the F1 axis, while cadence and heart rate variances were primarily captured along the F2 axis. Notably, when distance and physiological responses were projected simultaneously on the PCA correlation circle, the first 26 km of the race were positioned on the same side of the F1 axis as the metabolic responses, whereas the final kilometers were distributed on the opposite side, indicating a shift in physiological state as fatigue set in. The separation of heart rate and cadence entropy variances from the metabolic parameters suggests that these responses are independent of distance, contrasting with the linear increase in heart rate and decrease in cadence typically observed. Additionally, Agglomerative Hierarchical Clustering further categorized runners' physiological responses, revealing distinct clusters of entropy profiles. The analysis identified two to four classes of responses, representing different phases of the marathon for individual runners, with some clusters clearly distinguishing the beginning, middle, and end of the race. This variability emphasizes the personalized nature of physiological responses and pacing strategies, reinforcing the need for individualized approaches. These findings offer practical applications for optimizing pacing strategies, suggesting that real-time monitoring of entropy could enhance marathon performance by providing insights into a runner's physiological state and helping to prevent the onset of hitting the wall.

Quantifying Hitting Load in Racket Sports: A Scoping Review of Key Technologies.

PURPOSE: This scoping review aims to identify the primary racket and arm-mounted technologies based on inertial measurement units that enable the quantification of hitting load in racket sports. METHODS: A comprehensive search of several databases (PubMed, SPORTDiscus, Web of Science, and IEEE Xplore) and Google search engines was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for scoping reviews guidelines. Included records primarily focused on monitoring hitting load in racket sports using commercialized racket or arm-mounted inertial sensors through noncompetitive and competitive racket-sports players. RESULTS: A total of 484 records were identified, and 19 finally met the inclusion criteria. The largest number of systems found were compatible with tennis (n = 11), followed by badminton (n = 4), table tennis (n = 2), padel (n = 1), and squash (n = 1). Four sensor locations were identified: grip-attached (n = 8), grip-embedded (n = 6), wrist (n = 3), and dampener sensors (n = 2). Among the tennis sensors, only 4 out of the 11 (36.4%) demonstrated excellent reliability (>.85) in monitoring the number of shots hit either during analytic drills or during simulated matches. None of the other racket-sports sensors have undergone successful, reliable validation for hitting-volume quantification. CONCLUSIONS: Despite recent advancements in this field, the quantification of hitting volume in racket sports remains a challenge, with only a limited number of tennis devices demonstrating reliable results. Thus, further progress in technology and research is essential to develop comprehensive solutions that adequately address these specific requirements.

Lower-Body Strength Relationships with Sprint, Jump, and Sport-Specific Skill Performance in High School Girls Softball Players.

Softball athletes require multiple fitness traits (e.g., strength, speed, power) and sport-specific skills (e.g., hitting, throwing) for success. Lower-body strength could underpin these qualities; this has received little analysis among high school female athletes. This research investigated correlations between absolute and relative lower-body strength with age, linear speed, lower-body power, and throwing and hitting velocity in high school girls softball athletes. Archival data collected from 34 high school girls softball players (age=14.91±1.00 years; height=1.66±0.07 m; body mass=63.21±9.59 kg) from a private strength and conditioning facility was analyzed. The data included: age, height, and body mass; 0-9.14 and 0-18.29 m sprint interval times; standing broad jump (SBJ) distance (lower-body power); batted ball exit (i.e., hitting) and throwing velocity; and absolute and relative three-repetition maximum (3RM) front squat and hexagonal bar deadlift (HBD). Pearson's correlations (p<0.05) derived relationships between absolute and relative strength with the fitness and sport-specific tests. The results indicated significant relationships between the 3RM HBD with age (r=0.389) and hitting velocity (r=0.418). The 3RM front squat related to the SBJ (r=0.422) and hitting velocity (r=0.457). Relative 3RM HBD correlated with the 0-18.29 m sprint interval (r=-0.349). These results suggested that a strength and conditioning program that improves the lower-body strength of high school girls softball players could contribute to faster sprinting speed, further horizontal jumps, and greater hitting velocity. The results from this study highlights the value of strength enhancement in high school girls softball athletes and provides support for strength and conditioning program provision for these individuals.

Drift Analysis with Fitness Levels for Elitist Evolutionary Algorithms.

The fitness level method is a popular tool for analyzing the hitting time of elitist evolutionary algorithms. Its idea is to divide the search space into multiple fitness levels and estimate lower and upper bounds on the hitting time using transition probabilities between fitness levels. However, the lower bound generated by this method is often loose. An open question regarding the fitness level method is what are the tightest lower and upper time bounds that can be constructed based on transition probabilities between fitness levels. To answer this question, we combine drift analysis with fitness levels and define the tightest bound problem as a constrained multi-objective optimization problem subject to fitness levels. The tightest metric bounds by fitness levels are constructed and proven for the first time. Then linear bounds are derived from metric bounds and a framework is established that can be used to develop different fitness level methods for different types of linear bounds. The framework is generic and promising, as it can be used to draw tight time bounds on both fitness landscapes with and without shortcuts. This is demonstrated in the example of the (1+1) EA maximizing the TwoMax1 function.

Virtual reality perceptual training can improve the temporal discrimination ability of swinging during softball batting.

Perception and action uncoupling in fastball sports anticipatory training is often criticized. Nevertheless, perception-only training offers distinct advantages, such as flexibility concerning time, place, and injury limitations. Therefore, the effectiveness of this training approach warrants evaluation. This study developed a virtual reality (VR) training system based on the idea that the two visual pathways in the brain are associated with visual information attributes, rather than perception or action. A key feature of this study's perception-only training was its presentation of not only the opponent's kinematics but also the ball's flight information (the attributes that guide hitting) to train the visual system necessary for real situations. Seventeen female softball batters were assigned to two groups: a training group (N = 9) and a control group (N = 8). Only the training group underwent the VR anticipatory skill training to discriminate the different ball speeds. Both groups completed a perception test and an action test on the VR during the pre- and post-training periods. The perception test assessed response accuracy (RA) in discriminating ball speed, and the action test assessed the temporal difference in swing onset (delta onset). Comparison of these two outcome variables between groups revealed that perception-only training improved both perceptual and action responses. This study demonstrated the effectiveness of perception-only training and emphasized the need for its thoughtful utilization and design.

Longitudinal changes in youth baseball batting based on body rotation and separation.

BACKGROUND: Identifying the characteristics of batting mechanics, such as the proper angle and position of each body segment in youth baseball players, is important for proper instructions. This study aimed to identify the age-related changes in batting kinematics including rotational and separational movements of the head, upper trunk, pelvis, and arms, in youth baseball players. METHODS: Over the three seasons, we measured the batting motion of baseball players aged 6- to 12 years using three high-speed cameras. Participants were divided into six age categories according to the little league eligibility rules (players were classified according to their age as of July 31 of a given year). Toss batting was performed using an automatic tossing machine set obliquely in front of the batter. Additionally, we analyzed the rotation angles of the head, upper trunk, pelvis, and arm direction, and the separation angles-calculated using the difference of each rotational angle and the head movement distance and step width-at five points in batting phase: stance, load, foot contact, pre-swing, and ball contact. Finally, 17 players from under 8 (U8, i.e., approximately 7-8 years) to U10 and 13 from U11 to U13 were analyzed. A one-way repeated measures analysis of variance was performed to analyze age-related changes in batting kinematics. RESULTS: Several age-related changes in batting kinematics at various batting point were observed. The head-to-upper trunk separation angle increased with age from U8 to U10 during the foot contact (effect sizes [ES] = 0.658) and from U11 to U13 during the pre-swing (ES = 0.630). Additionally, the U13 showed a significantly increase in the upper and pelvis separation angles during load, foot contact, and pre-swing compared with U11 and U12 (ES = 0.131, 0.793, and 0.480). CONCLUSION: Various changes in batting kinematics occurred among each age group. Notably, U12 and U13 had the greater upper trunk-to-pelvis separation angle at foot contact and pre-swing compared to U11. Therefore, it would be important for the instruction of younger baseball players to understand the underdevelopment of trunk separation when batting and encourage the acquisition of such separation movements.

Lower extremity kinematic and kinetic factors associated with bat speed at ball contact during the baseball swing.

The purpose of this study was to determine which biomechanical variables measured during the baseball swing are associated with linear bat speed at ball contact (bat speed). Twenty collegiate baseball players hit a baseball from a tee into a net. Kinematics were recorded with a motion capture system sampling at 500 Hz and kinetics were measured by force plates under each foot sampling at 1000 Hz. Associations between bat speed, individual joint and segment kinematics, joint moments and ground reaction forces (GRF) were assessed using Pearson correlations and stepwise linear regression. Average bat speed was 30 ± 2 m/s. Lead foot peak vertical (159 ± 29% BW, r = 0.622, P = 0.001), posterior (-57 ± 12% BW, r = -0.574, P = 0.008) and resultant (170 ± 30% BW, r = 0.662, P = 0.001) GRF were all correlated with bat speed. No combination of factors strengthened the relationship to bat speed beyond these individual variables. These results illustrate the role of the lead leg in generating and transferring ground reaction forces through the kinetic chain in order to accelerate the bat. Training to improve bat speed should include both general lower extremity strengthening exercises and sport-specific hitting drills to improve lower extremity force production following lead foot contact.

A Pilot Study Using Entropy for Optimizing Self-Pacing during a Marathon.

A new group of marathon participants with minimal prior experience encounters the phenomenon known as "hitting the wall," characterized by a notable decline in velocity accompanied by the heightened perception of fatigue (rate of perceived exertion, RPE). Previous research has suggested that successfully completing a marathon requires self-pacing according to RPE rather than attempting to maintain a constant speed or heart rate. However, it remains unclear how runners can self-pace their races based on the signals received from their physiological and mechanical running parameters. This study aims to investigate the relationship between the amount of information conveyed in a message or signal, RPE, and performance. It is hypothesized that a reduction in physiological or mechanical information (quantified by Shannon Entropy) affects performance. The entropy of heart rate, speed, and stride length was calculated for each kilometer of the race. The results showed that stride length had the highest entropy among the variables, and a reduction in its entropy to less than 50% of its maximum value (H = 3.3) was strongly associated with the distance (between 22 and 40) at which participants reported "hard exertion" (as indicated by an RPE of 15) and their performance (p < 0.001). These findings suggest that integrating stride length's Entropy feedback into new cardioGPS watches could improve marathon runners' performance.

Ankle proprioception in table tennis players: Expertise and sport-specific dual task effects.

OBJECTIVES: To compare ankle proprioception between professional adolescent table tennis players at national and regional levels and age-matched non-athletes, and, in a nominally upper-limb sport, to explore the relationships between single- and dual-task ankle proprioception, years of training and sport-specific performance. DESIGN: Cross-sectional observational study. METHODS: Fifty-five participants (29 professional adolescent table tennis players and 26 non-athletic peers) volunteered. Ankle proprioception was first assessed using the active movement extent discrimination apparatus (AMEDA-single) for all; yet only the players were then re-assessed while executing a secondary ball-hitting task (AMEDA-dual). The mean Area Under the Receiver Operating Characteristic Curve was calculated as the proprioceptive score, and years of training and hitting rate were recorded. RESULTS: National-level players had significantly better ankle proprioception as shown by higher AMEDA-single scores than the other groups (all p < 0.05). Ankle proprioceptive performance was significantly impaired while ball-hitting (F1,28 = 58.89, p ≤ 0.001, ηp2 = 0.69). National-level players outperformed the regional-level significantly on the AMEDA-dual task (F1,27 = 21.4, p ≤ 0.001, ηp2 = 0.44). Further, ankle proprioceptive performance was related to expertise, in that both AMEDA-single and AMEDA-dual proprioceptive scores were correlated with years of training and ball-hitting rate (r from 0.40 to 0.54, all p < 0.05). CONCLUSIONS: Ankle proprioception is a promising measure that may be used to identify different ability levels among adolescent table tennis players. Superior ankle proprioception may arise from rigorous training and contribute to stroke accuracy. Dual-task proprioceptive assessment suggests how elite table tennis players perform differently from lower-ranked players in complex and changeable sports circumstances.

Opponent Hitting Behavior Prediction and Ball Location Control for a Table Tennis Robot.

The hitting position and velocity control for table tennis robots have been investigated widely in the literature. However, most of the studies conducted do not consider the opponent's hitting behaviors, which may reduce hitting accuracy. This paper proposes a new table tennis robot framework that returns the ball based on the opponent's hitting behaviors. Specifically, we classify the opponent's hitting behaviors into four categories: forehand attacking, forehand rubbing, backhand attacking, and backhand rubbing. A tailor-made mechanical structure that consists of a robot arm and a two-dimensional slide rail is developed such that the robot can reach large workspaces. Additionally, a visual module is incorporated to enable the robot to capture opponent motion sequences. Based on the opponent's hitting behaviors and the predicted ball trajectory, smooth and stable control of the robot's hitting motion can be obtained by applying quintic polynomial trajectory planning. Moreover, a motion control strategy is devised for the robot to return the ball to the desired location. Extensive experimental results are presented to demonstrate the effectiveness of the proposed strategy.

DNA Sequence Optimization Design of Arithmetic Optimization Algorithm Based on Billiard Hitting Strategy.

DNA computing is a very efficient way to calculate, but it relies on high-quality DNA sequences, but it is difficult to design high-quality DNA sequences. The sequence it is looking for must meet multiple conflicting constraints at the same time to meet the requirements of DNA calculation. Therefore, we propose an improved arithmetic optimization algorithm of billiard algorithm to optimize the DNA sequence. This paper contributes as follows. The introduction to the good point set initialization to obtain high-quality solutions improves the optimization efficiency. The billiard hitting strategy was used to change the position of the population to enhance the global search scope. The use of a stochastic lens opposites learning mechanism can increase the capacity of the algorithm to get rid of locally optimal. The harmonic search algorithm is introduced to clarify some unqualified secondary structures and improve the quality of the solution. 12 benchmark functions and six other algorithms are used for comparison and ablation experiments to ensure the effectiveness of the algorithms. Finally, the DNA sequences we designed are of higher quality compared to other advanced algorithms.

Applications of three-dimensional uncertain heat equations.

Uncertain heat equation is a partial differential equation describing temperature changes with time, while the strength of heat source is affected by the interference of noise. This paper applies the three-dimensional uncertain heat equation in some practical problems, including average temperature, maximum temperature, minimum temperature and minimum time of reaching a given temperature by using mathematical tools of time integral, space integral, extreme value and first hitting time.

Relationship between ground reaction force in horizontal plane and mechanical energy flow in torso during baseball tee batting.

The purpose of this study was to clarify the relationship between the ground reaction force (GRF) in the horizontal plane and the mechanical energy flow in the torso during baseball tee batting. The batting motion and GRF acting on each foot of 30 collegiate baseball players were recorded using a motion capture system and two force plates. To measure the mechanical energy inflow into the torso from both hip joints, the mechanical power of the torso by the force and torque of both hip joints was calculated. The horizontal GRF variables of the stride foot were significantly correlated with mechanical energy inflow into the lower torso from the hip joint of the stride foot side. Conversely, the horizontal GRF variables of the pivot foot were not significantly correlated with mechanical energy inflow into the lower torso from the hip joint of the pivot foot side. Thus, these results suggest that exploring the posture easily to receive the horizontal GRF by the stride foot (i.e., optimisation of magnitude and/or angle of GRF acting on the stride foot) increases the mechanical energy inflow into the lower torso from the hip joint of the stride foot side during baseball batting.

A boosting first-hitting-time model for survival analysis in high-dimensional settings.

In this paper we propose a boosting algorithm to extend the applicability of a first hitting time model to high-dimensional frameworks. Based on an underlying stochastic process, first hitting time models do not require the proportional hazards assumption, hardly verifiable in the high-dimensional context, and represent a valid parametric alternative to the Cox model for modelling time-to-event responses. First hitting time models also offer a natural way to integrate low-dimensional clinical and high-dimensional molecular information in a prediction model, that avoids complicated weighting schemes typical of current methods. The performance of our novel boosting algorithm is illustrated in three real data examples.

Evaluation, Treatment, and Outcomes of Batter's Shoulder.

PURPOSE OF REVIEW: This article reviews the incidence of batter's shoulder, the relevant biomechanics that predispose the lead shoulder to a posterior instability event, the evaluation and workup of posterior labral injury, the surgical technique for arthroscopic posterior labral repair, the postoperative rehabilitation process, and the clinical outcomes and return to sport after treatment of batter's shoulder. RECENT FINDINGS: New epidemiological studies have demonstrated the relatively low incidence of batter's shoulder at the professional baseball level with 85% of the injured players successfully returning to the sport with nonoperative management. However, recent studies have reinforced the limited historical literature that players requiring surgery are able to return to their prior sport at a high level. Batter's shoulder is a subtype of posterior glenohumeral instability caused by the significant forces experienced by the lead shoulder during the baseball swing. Although an uncommon injury, batter's shoulder is a source of significant time away from competition. In patients who do not improve with nonoperative management, arthroscopic posterior labral repair can reliably return players to sport. Future research studies should consider opportunities for injury prevention.

Accounting for delayed entry into observational studies and clinical trials: length-biased sampling and restricted mean survival time.

Individuals in many observational studies and clinical trials for chronic diseases are enrolled well after onset or diagnosis of their disease. Times to events of interest after enrollment are therefore residual or left-truncated event times. Individuals entering the studies have disease that has advanced to varying extents. Moreover, enrollment usually entails probability sampling of the study population. Finally, event times over a short to moderate time horizon are often of interest in these investigations, rather than more speculative and remote happenings that lie beyond the study period. This research report looks at the issue of delayed entry into these kinds of studies and trials. Time to event for an individual is modelled as a first hitting time of an event threshold by a latent disease process, which is taken to be a Wiener process. It is emphasized that recruitment into these studies often involves length-biased sampling. The requisite mathematics for this kind of sampling and delayed entry are presented, including explicit formulas needed for estimation and inference. Restricted mean survival time (RMST) is taken as the clinically relevant outcome measure. Exact parametric formulas for this measure are derived and presented. The results are extended to settings that involve study covariates using threshold regression methods. Methods adapted for clinical trials are presented. An extensive case illustration for a clinical trial setting is then presented to demonstrate the methods, the interpretation of results, and the harvesting of useful insights. The closing discussion covers a number of important issues and concepts.

Oxygen Uptake Measurements and Rate of Perceived Exertion during a Marathon.

Although the marathon race has been democratized, it remains complex due to the famous "hitting the wall" phenomenon after the 25th km. To characterize this "wall" from a physiological and Rate of Perceived Exertion (RPE) perspective in recreational marathon runners, we report first continuous breath-by-breath gas exchange measurements during an actual marathon race. In order to test the hypothesis that RPE could be a candidate for controlling the marathon pace, this study examined the relationship between RPE and the physiological variables time course throughout a marathon. Only the respiratory frequency and heart rate increased progressively during the race in all the runners, while the oxygen uptake and ventilatory rate followed different kinetics according the individuals. However, the indexation of the physiological parameters and speed by RPE showed the same decreased tendency for all the runners. In conclusion, these results suggest that running a marathon must be self-paced with the RPE.

Torso dynamics during follow through in baseball batting.

The purpose of this study was to clarify the relationship between the bat swing speed immediately after the ball impact and the dynamics of the torso during the follow through in baseball batting. The batting motion and ground reaction forces acting on each foot for 29 collegiate baseball players were recorded using a motion capture system and two force plates. The biomechanical variables of the torso joint (i.e., the virtual joint that divides the torso between upper and lower) were calculated. For right-handed batters, the torque power of the right rotation in the torso joint was negative. Additionally, the bat head speed immediately after the ball impact was significantly correlated with the negative (i.e., right) peak rotation torque of the torso joint (r = -.635, p < 0.001) and the negative peak power in the right rotation torque of the torso joint (r = -.590, p = 0.001). These results suggest that the left external abdominal oblique muscle is in eccentric contraction during the follow through in baseball batting. Moreover, the results imply that the higher the bat head speed immediately after the ball impact, the higher the possibility to strain the abdominal oblique muscle.

Simplified Virtual Reality System Can Be Used to Evaluate the Temporal Discrimination Ability in Softball Batting as in the Real Environment.

Recently, virtual reality (VR) technology has developed rapidly and has increasingly come to be used in the sports field. VR technology ranges from large, highly immersive devices to simple devices such as smartphones, and the respective usefulness and shortcomings of different device types have been debated. Simple devices have advantages such as portability, but also provide only a weak sense of realism. It is important to understand the purpose and extent to which VR technologies can be used. Our purpose in this study was to briefly measure one of the cognitive-motor abilities used in softball batting: temporal discrimination ability in swing onset when a batter faces two types of balls thrown at different speeds. We investigated whether a simplified head-mounted display (HMD) system can evaluate such cognitive-motor ability to the same extent as in a real environment. Ten elite female softball batters swung at fastballs and slowballs randomly thrown by the same pitcher in both real and 3D VR environments, with the same range of trajectories. We then compared the temporal discrimination ability of swing onset analyzed by video analysis between environments. We found that the discrimination ability in VR is almost the same as in reality. In addition, questionnaire items on the VR system related to user experience and cybersickness showed overall promising responses. However, we also found that the system had some issues that need to be considered, such as leading to early swing onset and large variability in it. We discussed the usefulness and limitations of the VR system by combining the results for swing onset with the questionnaire responses. By understanding the characteristics of VR technology and using it as an efficient evaluation and training of players, the sports field can make significant progress.

Associations between spanking beliefs and reported spanking among adolescents-parent/caregiver dyads in a Canadian sample.

BACKGROUND: Research consistently demonstrates that physical punishment of children including "spanking" is harmful. Interest in effective prevention is growing rapidly. The aim of the current study is to examine spanking beliefs among adolescents and parents in relation to reports of spanking that the adolescents experienced before 11 years of age. METHODS: Data were drawn from Wave 1 of a study conducted in 2017-2018 that included adolescents (14-17 years old) and one of their parents/caregivers from Manitoba, Canada (n = 1000 pairs). The study objectives were to examine: 1) spanking beliefs of adolescents and their parents; 2) the correlation between parent and adolescent spanking beliefs; 3) whether parents perceive the words "spank" vs. "hit" differently using intraclass correlation; 4) the association between parents' beliefs about spanking and parent- and adolescent-reported use of it; and 5) the relationship between sociodemographic variables and spanking. The data were analyzed using descriptive statistics, Spearman's correlation, intraclass correlation, and binary and multinomial logistic regression analyses. RESULTS: The prevalence of adolescent-reported and parents'-reported spanking were 46.0% and 39.6%, respectively. The proportions agreeing that spanking is a normal part of parenting were similar among adolescents (22.0%) and parents (18.5%), and were moderately correlated (intraclass correlation = 0.38, SE = 0.038). More than five times as many parents believed that "spanking" is necessary (19.5%) than believed that "hitting" is necessary (3.5%). Parents' positive spanking beliefs were associated with increased likelihood of adolescent- and parent-reported spanking. Few significant associations were found between sociodemographic variables and parent-reported or adolescent-reported spanking. CONCLUSIONS: Adolescents' spanking beliefs are related to their parents' spanking beliefs, suggesting that they are transmitted across generations. Public education and law reform are needed to decrease the normalization and perceived necessity of spanking in child-rearing. Efforts should include improving the understanding that spanking is a form of violence against children. With only a few significant differences noted between sociodemographic variables and parent- and adolescent- reported spanking and the prevalent use of spanking across all sociodemographic variable categories, it may be useful to develop universal approaches to awareness-raising and implementation of education strategies in Canada.