Competitive Distance Research Articles

Strength and Conditioning Habits of Competitive Distance Runners.

Blagrove, RC, Brown, N, Howatson, G, and Hayes, PR. Strength and conditioning habits of competitive distance runners. J Strength Cond Res 34(5): 1392-1399, 2020-Targeted strength and conditioning (S&C) programs can potentially improve performance and reduce injury risk factors in competitive runners. However, S&C practices of distance runners are unknown. This study aimed to explore S&C practices of competitive middle- and long-distance runners and examined whether reported frequency of injuries was influenced by training behaviors. One thousand eight hundred eighty-three distance runners (≥15 years old) completed an online survey. All runners who raced competitively were included in data analysis (n = 667). Distance runners mainly engaged with S&C activities to lower risk of injury (63.1%) and improve performance (53.8%). The most common activities used were stretching (86.2%) and core stability exercises (70.2%). Resistance training (RT) and plyometric training (PT) were used by 62.5 and 35.1% of runners, respectively. Junior (under-20) runners include PT, running drills, and circuit training more so than masters runners. Significantly more international standard runners engaged in RT, PT, and fundamental movement skills training compared with competitive club runners. Middle-distance (800-3,000 m) specialists were more likely to include RT, PT, running drills, circuit training, and barefoot exercises in their program than longer-distance runners. Injury frequency was associated with typical weekly running volume and run frequency. Strength and conditioning did not seem to confer a protection against the number of injuries the runners experienced. Practitioners working with distance runners should critically evaluate the current S&C practices of their athletes, to ensure that activities prescribed have a sound evidence-based rationale.

Mathematical model for the optimal determination of voltage level and PCC for large wind farms connection to transmission network

This study presents a practical mathematical model for the determination of the optimal point of connection of large wind farms to the transmission network. A comparative analysis of costs of connecting wind farms to the transmission network is given, about their distance from the point of common coupling (PCC). Calculations have been made for different installed capacity of the wind farm and for different voltage levels of PCC. Based on these calculations, there have been defined competitive distances of a wind farm with a certain power from the network of different voltage levels (e.g. 110 and 220 kV) for which the connection costs are equal. Such calculations are widely applicable and can be used by transmission system operators and wind power plant developers to optimise and plan the connection of a wind farm to the transmission network.

Визначення найбільш вагомих показників підготовленості юнаків, представників різних способів плавання, що лімітують їх спортивні досягнення

Elena Politko & Viacheslav Shutieiev Purpose: the establishment of the most significant selection criteria for swimmers aged 14–16 years specializing in various swimming methods, which limit their sporting achievements. Material & Methods: analysis and synthesis of scientific and methodical literature, pedagogical observation, testing, anthropometric measurements, methods of mathematical statistics. Results: the scientific knowledge about modern model characteristics of a constitution and physical preparedness of the young swimmers specializing in various ways of swimming is added. Established significant selection criteria, allowing to identify the most gifted athletes, to orient their training for a specific competitive distance. Conclusion: obtained results can be recommended for use in the work of swimming coaches to improve the quality of selection and sports orientation of young athletes on the choice of swimming and assess their prospects.

The Relationship between Bone Mineral Accrual and Changes of Body Composition in Competitive Girl Runners

Low bone density is a complication of a long-term strict weight control during adolescence in women. PURPOSE: To assess whether decrease in percent body fat (%BF) is associated with an impaired bone mineral accrual in girl runners. METHODS: Consecutive 22 freshmen girl runners (15y/o, 158cm, 45kg) during 7 years in competitive high school teams were evaluated over 2 years of training. DXA was performed at the preparatory phase (baseline) and repeated after 23 ± 2 months (follow-up). The runners were divided into 2 groups; negative (DEC, n=11) or positive (GAIN, n=11) changes of %BF (Δ%BF) during the period. The effect of the period and the group on the changes in bone mineral content (BMC) and density (BMD) of total body less head and z-score were analyzed by 2-way repeated measures ANOVA. As for lean soft tissue mass (LSM) and fat mass (FM), paired t-test was used to compare between baseline and follow-up. Bivariate correlation analysis was used to examine the relationship between bone mineral accrual (ΔBMC and ΔBMD) and Δ%BF as well as the changes of FM (ΔFM) and LSM (ΔLSM). Written informed consent was obtained from the runners and their parents. P<0.05 was considered as statistically significant. RESULTS: %BF changed from 17.4 to 14.3 (DEC) and 15.0 to 18.4 % (GAIN). The period had significant effects on BMC, BMD, and z-score without interactions. Contrast showed significant increases in those variables, while the group of Δ%BF had no significant effect, indicating the values of DEC and GAIN were similarly increased; 1.57 to 1.64 and 1.66 to 1.77 kg, 0.98 to 1.00 and 1.00 to 1.03 g/cm2, and -0.25 to -0.20 and 0.04 to 0.22, respectively. The DEC runners gained LSM (34.2 to 36.1 kg) and reduced FM (7.7 to 6.4 kg) significantly, while the GAIN runners significantly increased FM (6.9 to 9.0 kg) without LSM change (36.6 to 37.0 kg). Neither Δ%BF nor ΔFM, but ΔLSM was significantly correlated with ΔBMC (r=0.45) and ΔBMD (r=0.55). CONCLUSIONS: Bone mineral was equally accrued among the runners of which %BF increased or decreased, where the accretion was associated with LSM gain. Competitive distance runners would develop leanness by not only losing FM but also gaining LSM (i.e., skeletal muscle) along with long-term exercise training. This would ameliorate an impairment of bone mineral acquisition by strict weight control.

The Association Between Trunk Lean and Running Kinetics in Competitive Distance Runners

The Association Between Trunk Lean and Running Kinetics in Competitive Distance Runners

Особливості техніко-тактичних дій висококваліфікованих спортсменів при пропливанні дистанції 100 метрів способом кроль на грудях

Olga Pilipko Purpose : to determine the features of technical and tactical actions of highly skilled athletes when swimming a distance of 100 meters by front crawl. Material & Methods : analysis and generalization of literary sources, video filming, timekeeping, methods of mathematical statistics. The contingent of subjects consisted of athletes who specialized in a distance of 100 meters in the way of swimming the front crawl and had the level of sports qualification master of sports of Ukraine, master of sports of international grade. Results : dynamics of indicators of technical and tactical skill among highly skilled athletes during their overcoming the 100 meter distance by front crawl has been investigated; characterized by the variability of technical and tactical actions of highly skilled athletes in different parts of the competition distance of 100 meters; determined the degree of influence of speed, pace and step of the cycle of rowing movements on the result of swimming a distance of 100 meters using the front crawl. Conclusion: overcoming the distance of 100 meters by the front crawl has its own specifics, which is reflected in changes in the indicators of technical and tactical masterhood; model characteristics of the most influential parameters of technical and tactical actions of highly skilled swimmers can serve as a guideline for improving the training process of athletes depending on their distance specialization.

Biomechanical Adaptations and Performance Indicators in Short Trail Running.

Our aims were to measure anthropometric and oxygen uptake (O2) variables in the laboratory, to measure kinetic and stride characteristics during a trail running time trial, and then analyse the data for correlations with trail running performance. Runners (13 men, 4 women: mean age: 29 ± 5 years; stature: 179.5 ± 0.8 cm; body mass: 69.1 ± 7.4 kg) performed laboratory tests to determine O2 max, running economy (RE), and anthropometric characteristics. On a separate day they performed an outdoor trail running time trial (two 3.5 km laps, total climb: 486 m) while we collected kinetic and time data. Comparing lap 2 with lap 1 (19:40 ± 1:57 min vs. 21:08 ± 2:09 min, P < 0.001), runners lost most time on the uphill sections and least on technical downhills (-2.5 ± 9.1 s). Inter-individual performance varied most for the downhills (CV > 25%) and least on flat terrain (CV < 10%). Overall stride cycle and ground contact time (GCT) were shorter in downhill than uphill sections (0.64 ± 0.03 vs. 0.84 ± 0.09 s; 0.26 ± 0.03 vs. 0.46 ± 0.90 s, both P < 0.001). Force impulse was greatest on uphill (248 ± 46 vs. 175 ± 24 Ns, P < 0.001) and related to GCT (r = 0.904, P < 0.001). Peak force was greater during downhill than during uphill running (1106 ± 135 vs. 959 ± 104 N, P < 0.01). Performance was related to absolute and relative O2 max (P < 0.01), vertical uphill treadmill speed (P < 0.001) and fat percent (P < 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. O2 max, vertical running speed and fat percent are important predictors for trail running performance. Performance between runners varied the most on downhills throughout the course, while pacing resembled a reversed J pattern. Future studies should focus on longer competition distances to verify these findings and with application of measures of 3D kinematics.

LRP5, Bone Density, and Mechanical Stress: A Case Report and Literature Review

The Wnt-β-catenin pathway receptor, low-density lipoprotein receptor-related protein 5 (LRP5), is a known regulator of bone mineral density. It has been hypothesized that specific human polymorphisms in LRP5 impact bone density, in part, by altering the anabolic response of bone to mechanical loading. Although experiments in animal models support this hypothesis, there is limited evidence that LRP5 polymorphisms can alter the anabolic response of bone to mechanical loading in humans. Herein, we report a young male who harbors a rare LRP5 missense mutation (A745V) and who provides potential proof of principle for this mechanotransduction hypothesis for low bone density. The subject had no history of fractures until age 18, a year into a career in competitive distance running. As he continued to run over the following 2 years, his mileage threshold to fracture steadily and rapidly decreased until he was diagnosed with severe osteoporosis (lumbar spine BMD Z-score of −3.2). By contextualizing this case within the existing LRP5 and mechanical stress literature, we speculate that this represents the first documented case of an individual in whom a genetic mutation altered the anabolic response of bone to mechanical stress in a manner sufficient to contribute to osteoporosis.

Physiological and potentially pathological ECG changes in swimmers of different sports qualifications

The purpose of the work. To study the indicators of bioelectric myocardial activity in swimmers for a distance from 100 to 400 meters of different sports qualifications in the preparatory period of the training process. Materials and methods. At the beginning of the preparatory period, 257 sportsmen aged from 11 to 29 years old (average age 15.4 ± 0.18 years) who were engaged in swimming and their competition distance was from 100 to 400 meters with qualification from category III to MMS were examined. The bioelectric activity of the myocardium was studied using diagnostic automated complex “Cardio+”. For differential diagnostics, sportsmen with right atrial ectopic rhythm, wandering pacemaker (WP) and changes in the end part of the ventricular complex were subjected to an exercise tolerance test on a bicycle ergometer using the method of submaximal exercise PWC 170 test and sportsmen with CLC syndrome and left anterior fascicular block – to echocardiography using a device My Lab 7 (Italy). Results. The MS-MMS swimmers differ from the CMS-1 qualification swimmers by less number of individuals with right atrial ectopic rhythm and early repolarization syndrome (ERS); they are more likely to be diagnosed with bradycardia, high ECG voltage and changes in the end part of the ventricular complex, but CLC syndrome is less frequently, compared with the swimmers of II–III qualification category. Swimmers of CMS I qualification are more often diagnosed with high ECG voltage, ERS, but the number of persons with CLC syndrome and T-infantile is less among them in comparison with the sportsmen of II–III category. Conclusions. After physical activity in the form of a submaximal exercise PWC 170 test, sportsmen with right atrial ectopic rhythm and WP demonstrated sinus rhythm restoration, and sportsmen with changes in the end part of the ECG ventricular complex showed ECG normalization. Echocardiography revealed neither heart dilatation no hypertrophy in the sportsmen with CLC syndrome and left anterior fascicular block, and the presence of incomplete right bundle branch block and ERS should be considered as the ECG features in this category of sportsmen.

Achilles tendon structure differs between competitive distance runners and nonrunners despite no clinical signs or symptoms of midsubstance tendinopathy.

Achilles tendinopathy affects many running athletes and often leads to chronic pain and functional deficits. Although changes in tendon structure have been linked with tendinopathy, the effects of distance running on tendon structure are not well understood. Therefore, the purpose of this study was to characterize structural differences in the Achilles tendons in healthy young adults and competitive distance runners using quantitative ultrasound analyses. We hypothesized that competitive distance runners with no clinical signs or symptoms of tendinopathy would have quantitative signs of tendon damage, characterized by decreased collagen alignment and echogenicity, in addition to previous reports of thicker tendons. Longitudinal ultrasound images of the right Achilles tendon midsubstance were acquired in competitive distance runners and recreationally active adults. Collagen organization, mean echogenicity, and tendon thickness were quantified using image processing techniques. Clinical assessments confirmed that runners had no signs or symptoms of tendinopathy, and controls were only included if they had no history of Achilles tendon pain or injuries. Runner tendons were 40% less organized, 48% thicker, and 41% less echogenic compared with the control tendons ( P < 0.001). Young adults engaged in competitive distance running have structurally different tendons than recreationally active young adults. NEW & NOTEWORTHY In this study, we quantified the Achilles tendon substructure in distance runners, and a control group of young adults, to determine whether distance running elicits structural adaptations of the tendon. We found that competitive distance runners have structurally compromised Achilles tendons despite not showing any clinical signs or symptoms of tendon injury. These findings suggest that distance running may stimulate structural changes as a protective mechanism against tendon pain and dysfunction.

Dynamic Hip Strength and Footfall Patterns in Competitive Distance Runners

PURPOSE: Foot strike pattern during running can contribute to lower extremity overuse injuries such as stress fracture, potentially due to high loading rates (LR). However, adopting a forefoot strike (FF) may require additional lower extremity strength due to the greater demand placed on the gluteal muscles compared to a rearfoot strike. The purpose of this study was to determine the association between hip extensor strength, foot strike pattern, and LR. It was hypothesized that greater hip extensor strength would be associated with a FF pattern, and a lower LR. METHODS: 23 uninjured, collegiate distance runners (91% male, age=21.9±2.5 years, height=1.77±0.06 m, mass=64.15±6.6 kg, running volume=82.55±17.45 km/week) who were resistance trained were recruited for this study. Hip extensor strength was assessed via maximal voluntary isometric contractions (MVIC) on an isokinetic dynamometer and 1-repetition maximum back squat (1RM BS). LR and foot strike index (FSI) were assessed during 5 overground running trials at the participant’s preferred training pace. FSI was calculated as the distance (m) between the center of pressure and location of the calcaneal marker at initial contact relative to the participant’s foot length (m). The highest MVIC peak torque (PT; N/kg) and 1RM BS, median FSI, and average LR (body weight/second) of the 5 trials were used for analysis. Spearman Rho and partial correlations were used to determine relationships between dependent variables. RESULTS: Greater 1RM BS was associated with a larger FSI (rho=0.499, p=0.018). Greater FSI was associated with lesser LR (rho=-0.494, p=0.017). Greater 1RM BS and lesser LR were not significantly associated (r=-0.394, p=0.077). PT was not associated with FSI or LR. CONCLUSIONS: Runners with greater 1RM BS land in a more FF position and with lower LR. These findings emphasize the contribution of hip extensor strength to running mechanics, and justify the selection of the back squat for runners.

Competitive performance as a substitute for competiveness measurement in tourism destinations: an integrative study

PurposeThe purpose of this paper is to address a new method to evaluate the competitiveness of tourist destinations based on competitive performance from the consumers’ perspective. The main objective is to assess the sources of relative strength and weakness perceived in a destination, and to evaluate its performance vis-à-vis to the main competitors identified by tourists through measurement indexes.Design/methodology/approachThe strengths and weaknesses of the focal destination were identified by plotting 12 tourism-specific variables (attractors) and 12 business-related variables in importance-performance matrix (IPA) grids. The set of destinations identified as “the main competitors” were built according to the frequency they were mentioned, and the indicators of competitiveness were estimated by averaging variables representing dimensions identified by exploratory-confirmatory factor analysis. The variables were aggregated into dimensions to permit comparisons in relation to the main competitors.FindingsThe results suggest that tourism-specific variables converge to “tourist attractions” and “conviviality,” and that business-related variables converge into “accessibility,” “infrastructure” and “macrostructure.” The competitiveness against competition was evaluated twice: by using an IPA grid to evaluate competition against “all others,” and by comparing the factors of performance across the most cited competitors. The results show that the focal destination surpasses most of its main competitors in conviviality, but has some deficiencies in tourist attractions, and that dimensions representing the business-related variables fit in the middle.Research limitations/implicationsThe authors acknowledge that competitive performance, used as surrogate for competitiveness, is fairly limited once it does not consider the supply side potential forces that also influence the destination competitiveness (DC) at large. But although limited to the demand side, the proxy used to assess (DC) is in accordance with previous literature.Practical implicationsThe results have high value to DMO managers, especially to those ones involved in developing tourism attractions.Originality/valueThis research advances over previous works: by identifying the nearest competitors of a destination; and by representing the competitive distance between the focal destination and its main competitors.

Optimizing dynamic time warping’s window width for time series data mining applications

Dynamic Time Warping (DTW) is a highly competitive distance measure for most time series data mining problems. Obtaining the best performance from DTW requires setting its only parameter, the maximum amount of warping (w). In the supervised case with ample data, w is typically set by cross-validation in the training stage. However, this method is likely to yield suboptimal results for small training sets. For the unsupervised case, learning via cross-validation is not possible because we do not have access to labeled data. Many practitioners have thus resorted to assuming that “the larger the better”, and they use the largest value of w permitted by the computational resources. However, as we will show, in most circumstances, this is a naive approach that produces inferior clusterings. Moreover, the best warping window width is generally non-transferable between the two tasks, i.e., for a single dataset, practitioners cannot simply apply the best w learned for classification on clustering or vice versa. In addition, we will demonstrate that the appropriate amount of warping not only depends on the data structure, but also on the dataset size. Thus, even if a practitioner knows the best setting for a given dataset, they will likely be at a lost if they apply that setting on a bigger size version of that data. All these issues seem largely unknown or at least unappreciated in the community. In this work, we demonstrate the importance of setting DTW’s warping window width correctly, and we also propose novel methods to learn this parameter in both supervised and unsupervised settings. The algorithms we propose to learn w can produce significant improvements in classification accuracy and clustering quality. We demonstrate the correctness of our novel observations and the utility of our ideas by testing them with more than one hundred publicly available datasets. Our forceful results allow us to make a perhaps unexpected claim; an underappreciated “low hanging fruit” in optimizing DTW’s performance can produce improvements that make it an even stronger baseline, closing most or all the improvement gap of the more sophisticated methods proposed in recent years.

Relationship between Motivation for Participation in Trail running Competition and Competition Distance

Relationship between Motivation for Participation in Trail running Competition and Competition Distance

A fat mass and obesity-associated gene polymorphism influences fat mass in exercise-trained individuals

BackgroundA single nucleotide polymorphism (SNP) in the fat mass and obesity-associated (FTO) gene is a strong predictor of obesity in humans. The FTO SNP (rs1421085) results in a T to C nucleotide substitution that may result in an increased risk for obesity in individuals who carry at least one C allele. The purpose of this investigation was to characterize the FTO genotype in a cohort of exercise-trained men and women.MethodsWe tested 108 exercise-trained individuals that included professional mixed martial arts fighters, competitive distance runners, collegiate swimmers, stand-up paddlers as well as a cohort of recreational bodybuilders. Body composition was assessed via dual-energy x-ray absorptiometry (DXA). Saliva samples were collected in order to genotype participants and quantify cortisol levels.ResultsThe physical characteristics of the subjects were as follows (mean±SD): body weight 74.5±15.6 kg; height 171.5±9.5 cm; bone mineral content 2.8±0.7 kg; fat mass 15.7±5.5 kg; lean body mass 55.9±14.4 kg; % body fat 21.6±7.0. Independent samples t tests showed that C allele carriers (n = 54) had significantly higher fat mass t(106) = 3.13, p < 0.01 and body fat percentage t(106) = 2.68, p < 0.01, relative to the TT group (n = 54) (i.e., fat mass: C/− 17.3 ±5.6 kg, TT 14.2±4.6 kg; body fat percentage: C/− group 23.4±7.4%, TT group 19.9±6.2). No other measures of body composition were associated with the FTO genotype (i.e., body mineral density, bone mineral content, or lean body mass). Moreover, cortisol levels were significantly higher in the TT group relative to the C allele carriers t(106) = 2.37, p = 0.02 (i.e., TT 0.35 ±0.35 μg/dL, C/− 0.22±0.16 μg/dL).ConclusionsOur findings demonstrate a relationship between C allele carriers on the FTO gene and a predisposition to a higher fat mass and body fat percentage. In addition, we found no relationship between cortisol and fat mass. However, due to the cross-sectional nature of this investigation, we cannot infer causality regarding the FTO gene and body composition.

Influencing Mechanism of Potential Factors on Passengers’ Long-Distance Travel Mode Choices Based on Structural Equation Modeling

Understanding the public transportation users’ preferences to long-distance travel modes would contribute to reasonable developing policies and resource allocation. This paper aims to explore the influencing mechanism of potential factors on the long-distance travel mode choice. A survey was conducted to collect the data. The analysis of variance (ANOVA) approach was applied to analyze the correlation relationship between potential factors and travel mode choice behavior. The results showed that, except gender, service demand for safety and departure time, all of the other factors significantly influenced the travel mode choice behavior. Specifically, passengers with higher education level and income level were more likely to choose high-speed railway (HSR) and plane; passengers caring about travel expense were more likely to choose ordinary train, whereas plane and HSR may be chosen more by passengers caring more about comfort, punctuality and efficiency; the more passengers were satisfied with travel modes’ service performance, the more they would be likely to choose them; the most competitive distance ranges for coach, ordinary train, HSR and plane were below 500 km, 500–1000 km, 500–1500 km and over 1500 km, respectively. Besides, the structural equation modeling (SEM) technique was applied to investigate the influencing mechanism of factors on the long-distance travel mode choice. The results revealed that travel distance was the most significant variable directly influencing passengers’ mode choices, followed by the service demand, performance evaluation, and personal attributes. Furthermore, personal attributes were verified to have an indirect effect on travel mode choice behavior by significantly affecting the service demand and performance evaluation.

Особливості прояву енергетичного потенціалу кваліфікованих спортсменів і чутливість кардіореспіраторної системи до гіперкапнії

Мета. Виділити типи реакції кардіореспіраторної системи (КРС) на гіперкапнічні зрушення дихального гомеостазису кваліфікованих спортсменів, які спеціалізувалися на змагальних дистанціях різної тривалості, а також визначити їх взаємозв’язок з характером реалізації енергетичного і функціонального потенціалу в умовах фізичних навантажень. Методи. Для аналізу реакцій КРС на фізичні навантаження було використано комплекс тестів, який дав можливість визначити аеробні й анаеробні можливості організму спортсменів. Для оцінки реакції КРС на гіперкапнію використовували прогресуючу гіперкапнічну стимуляцію методом «зворотного дихання». Визначали характеристики функціональної підготовленості спортсменів. Результати. Зі збільшенням тривалості основної змагальної дистанції і рівня загальної працездатності спортсменів відзначалося зниження чутливості КРС до CO 2 -H + -стимула. Встановлено позитивний взаємозв’язок між характеристиками чутливості КРС до CO 2 -H + -стимула з рівнем реакцій КРС і швидкістю їх розвитку в умовах навантаження середньої аеробної потужності і негативний взаємозв’язок – в умовах навантаження максимальної аеробної потужності

Организация и проведение соревнований по зимнему триатлону в Украине

Vladimir VodlozerovPurpose: to analyze the system of organizing and running competitions according to the type of the triathlon-winter program in Ukraine for compliance with the rules of the International Triathlon Federation. Material &amp; Methods: on the basis of the study of the specialized literature and the regulatory framework of a number of triathlon federations, a comparative analysis of the winter triathlon emulation at competition distances abroad and in Ukraine. Result: correspondence of two winters combined distances in Ukraine to the official formats of the international winter triathlon competitions in Europe and the world are found out. Conclusion: in basis for organizing and conducting competitions for a new variety of continuous triathlon in our country are the rules of the International Triathlon Federation, and the competitive distances in the form of the triathlon-winter program in Ukraine correspond to international standards.

Fast and Accurate Time-Series Clustering

The proliferation and ubiquity of temporal data across many disciplines has generated substantial interest in the analysis and mining of time series. Clustering is one of the most popular data-mining methods, not only due to its exploratory power but also because it is often a preprocessing step or subroutine for other techniques. In this article, we present k -Shape and k -MultiShapes ( k -MS), two novel algorithms for time-series clustering. k -Shape and k -MS rely on a scalable iterative refinement procedure. As their distance measure, k -Shape and k -MS use shape-based distance (SBD), a normalized version of the cross-correlation measure, to consider the shapes of time series while comparing them. Based on the properties of SBD, we develop two new methods, namely ShapeExtraction (SE) and MultiShapesExtraction (MSE), to compute cluster centroids that are used in every iteration to update the assignment of time series to clusters. k -Shape relies on SE to compute a single centroid per cluster based on all time series in each cluster. In contrast, k -MS relies on MSE to compute multiple centroids per cluster to account for the proximity and spatial distribution of time series in each cluster. To demonstrate the robustness of SBD, k -Shape, and k -MS, we perform an extensive experimental evaluation on 85 datasets against state-of-the-art distance measures and clustering methods for time series using rigorous statistical analysis. SBD, our efficient and parameter-free distance measure, achieves similar accuracy to Dynamic Time Warping (DTW), a highly accurate but computationally expensive distance measure that requires parameter tuning. For clustering, we compare k -Shape and k -MS against scalable and non-scalable partitional, hierarchical, spectral, density-based, and shapelet-based methods, with combinations of the most competitive distance measures. k -Shape outperforms all scalable methods in terms of accuracy. Furthermore, k -Shape also outperforms all non-scalable approaches, with one exception, namely k -medoids with DTW, which achieves similar accuracy. However, unlike k -Shape, this approach requires tuning of its distance measure and is significantly slower than k -Shape. k -MS performs similarly to k -Shape in comparison to rival methods, but k -MS is significantly more accurate than k -Shape. Beyond clustering, we demonstrate the effectiveness of k -Shape to reduce the search space of one-nearest-neighbor classifiers for time series. Overall, SBD, k -Shape, and k -MS emerge as domain-independent, highly accurate, and efficient methods for time-series comparison and clustering with broad applications.

Are Clinical Symptoms Of Running Overuse Injuries Associated With Thermographic Response? A Proof-of-concept Study

Medical infrared thermography (MIT), a non-radiating imaging technology, detects changes in skin temperature. Musculoskeletal injuries result in blood flow changes which may produce patterns of associated changes in skin temperature that can be visually detected by MIT. PURPOSE: To determine if clinical symptoms of distal lower extremity overuse injuries in runners are associated with visually detectible changes in MIT. METHODS: 29 competitive distance runners (age 18-25y, running >25 miles per week) enrolled and participated. Once weekly, runners reported to lab for MIT photos of bilateral lower limbs taken with an infrared camera. Prior to MIT, runners acclimatized to lab conditions for 15 minutes and the camera was calibrated to the room temperature and humidity. A modified Oslo Sports Trauma Research Centre (OSTRC) overuse injury questionnaire was used for athlete-reported musculoskeletal symptoms and problems. MIT photos and OSTRC scores were obtained on a weekly basis for 8 weeks. Runners’ photos were grouped into those with no reports of any lower extremity problems (Controls: OSTRC = 0, n=5); and those with reports of significant lower extremity problems (Injured: OSTRC >50, n=7). Photos from each group were placed into an online viewer and evaluated by 7 blinded clinicians. For the injured group, a photo from the week of the highest reported OSTRC score was paired with a baseline (OSTRC <25) photo. For the control group, two uninjured photos were paired. The reference photo for each pair was labeled. The order of photos (control vs. injured) was randomized and reviewers were not provided the number of included injured runners. Clinicians visually inspected 12 image pairs and decided whether or not the photo suggested a lower extremity problem existed. Diagnostic accuracy statistics were computed for each evaluator. RESULTS: The median (interquartile range) for the seven evaluators were: sensitivity=0.43 (0.29), specificity=0.60 (0.2), positive likelihood ratio=1.43 (0.0), negative likelihood ratio=0.71 (0.18). CONCLUSIONS: Low diagnostic accuracy and considerable inter-rater variability suggests evaluator training of MIT interpretation is necessary to accurately confirm or disconfirm presence of injury based on MIT findings.