Accuracy and reliability of inertial devices for load assessment during flywheel workout / Precisión y confiabilidad de los dispositivos inerciales para la evaluación de la carga durante entrenamiento con polea cónica

Abstract There is currently an increase in inertial flywheel application in strength training; thus, it must be monitored by an accurate and reliable device. The present study tested: (1) the accuracy of an inertial measurement device (IMU) to correctly measure angular velocity and (2) its inter-unit reliability for the measurement of external load. The analysis was performed using Pearson Correlation and Intraclass Correlation Coefficient (ICC). The IMU accuracy was tested using Bland-Altman and the reliability with the coefficient of variation (CV). Ten elite-level football players performed ten series of 5 repetitions in a one-hand standing row exercise (5 series with each arm). A nearly perfect accuracy (ICC=.999) and a very good between-device reliability (Bias=-.010; CV=.017%) was found. IMU is a reliable and valid device to assess angular velocity in inertial flywheel workout objectively.

Resumen Actualmente, hay un aumento en la utilización de la polea cónica en el entrenamiento de fuerza; por lo tanto, es necesario monitorearlo con un dispositivo preciso y confiable. El presente estudio probó: (1) la precisión de un dispositivo de medición inercial (IMU), para medir correctamente la velocidad angular y (2) su confiabilidad entre unidades para la medición de carga externa. El análisis se realizó utilizando la correlación de Pearson y el Coeficiente de Correlación Intra-clase (CCI). La precisión de la IMU se probó usando Bland-Altman y la confiabilidad con el Coeficiente de Variación (CV). Diez jugadores de fútbol de nivel élite realizaron 10 series de 5 repeticiones en un ejercicio de fila de pie con una mano (5 series con cada brazo). Se encontró una precisión casi perfecta (ICC = .999) y una muy buena confiabilidad entre dispositivos (Sesgo = -. 010; CV = .017%). IMU´s es un dispositivo confiable y válido para evaluar objetivamente la velocidad angular en el entrenamiento inercial de la polea cónica.

Resumo Atualmente, há um aumento na utilização da polia cônica no treinamento de força; portanto, é necessário monitorá-lo com um dispositivo preciso e confiável. O presente estudo testou: (1) a precisão de um dispositivo de medição inercial (IMU), para medir corretamente a velocidade angular e (2) sua confiabilidade interunidades para medição de carga externa. A análise foi realizada por meio da correlação de Pearson e do Coeficiente de Correlação Intraclasse (ICC). A precisão do IMU foi testada usando Bland-Altman e a confiabilidade com o Coeficiente de Variação (CV). Dez jogadores de futebol de elite realizaram 10 séries de 5 repetições em um exercício de linha em pé com uma mão (5 séries com cada braço). Foi encontrado uma precisão quase perfeita (ICC = 0,999) e confiabilidade entre dispositivos muito boa (Bias = - 0,010; CV = 0,017%). IMU's é um dispositivo confiável e válido para avaliar objetivamente a velocidade angular no treinamento inercial da polia cônica.

Impact of high-heeled and sport shoes on multi-joint external load profile during walking.

BACKGROUND: Previous studies have analysed the effect of wearing high-heeled shoes (HHS) on gait analysis, balance and its relation to health. However, further research is needed to study its effect on the difference of chain reactions in the transfer of body impacts from the lower to the upper limbs. OBJECTIVES: The aims of the present research were: (a) to compare the effects of wearing HHS on impacts across body joints during walking with sport shoes (SS) as a reference, and (b) to examine such effects at different speeds. METHODS: Seven well-trained women completed this study. Incremental treadmill walking test were performed with two different footwear: SS and HHS. Inertial devices were used to quantify the chain reactions at selected anatomical lower limbs and trunk locations. Statistical analysis included the Wilcoxon test with ranges and Cohen's d effect size with percentage of differences. RESULTS: The highest values were found at the heel in both footwear and in both legs (SS: right =0.76 ± 0.27, left = 0.79 ± 0.27; HHS: right = 1.07 ± 0.38, left = 1.11 ± 0.41), while the lowest values were registered at lower and upper back. Furthermore, significant differences were found with the HHS load being higher at all locations (p< 0.05; %=𝑑𝑖𝑓𝑓 12.20-36.36%), influenced by the walking speed. In addition, a strong influence of footwear in the change of the laterality profile was found (p< 0.05). CONCLUSIONS: These findings suggest that the use of HHS increase the load on the lower limb and the trunk. Until reaching 5 km/h during walking, no significant differences were found between wearing HHS or SS in accelerometer load, producing exponential differences from this speed. The great between-subject variability implies that within-subject analysis is recommended, as it is more related to real clinical practice.

Validity and reliability of an eight antennae ultra-wideband local positioning system to measure performance in an indoor environment.

Validity and reliability have become crucial factors in tracking player load and positioning. One of the most important parameters to guarantee accurate measurements with radiofrequency systems is the number of reference nodes used to calculate player position. However, the accuracy of ultra-wideband (UWB) technology has only been analysed with 6 antennae. So, the purpose of the present study was to analyse the accuracy and inter-unit reliability of an UWB system with eight antennae. Three well-trained males covered 18 trajectories for the analysis of x- and y- coordinate accuracy assessment related to the positional variation among eight antennae UWB data and lines on a basketball court. This was achieved using geographical information system mapping software that calculated, for each interval and participant, the distance from the main axis of locomotion and the opposite side of the field every 0.5 s. The results showed that this is a valid system (Mean = 0.03 m; magnitude differences = 0.21% with real measures as reference; %CV <1% in all cases) for measuring locomotion and positioning. Besides, the inter-unit, test-retest and inter-subject analysis did not influence the reliability results. So, an eight antennae UWB system can be considered suitable for locomotion and positioning in an indoor environment.

Accelerometry as a method for external workload monitoring in invasion team sports. A systematic review.

Accelerometry is a recent method used to quantify workload in team sports. A rapidly increasing number of studies supports the practical implementation of accelerometry monitoring to regulate and optimize training schemes. Therefore, the purposes of this study were: (1) to reflect the current state of knowledge about accelerometry as a method of workload monitoring in invasion team sports according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, and (2) to conclude recommendations for application and scientific investigations. The Web of Science, PubMed and Scopus databases were searched for relevant published studies according to the following keywords: "accelerometry" or "accelerometer" or "microtechnology" or "inertial devices", and "load" or "workload", and "sport". Of the 1383 studies initially identified, 118 were selected for a full review. The main results indicate that the most frequent findings were (i) devices' body location: scapulae; (b) devices brand: Catapult Sports; (iii) variables: PlayerLoadTM and its variations; (iv) sports: rugby, Australian football, soccer and basketball; (v) sex: male; (vi) competition level: professional and elite; and (vii) context: separate training or competition. A great number of variables and devices from various companies make the comparability between findings difficult; unification is required. Although the most common location is at scapulae because of its optimal signal reception for time-motion analysis, new methods for multi-location skills and locomotion assessment without losing tracking accuracy should be developed.

Influence of playing position and laterality in centripetal force and changes of direction in elite soccer players.

The purpose of the present study was to: (a) assess centripetal force (CentF) and changes of direction (COD) in elite soccer players according to playing position (central defender, CD; lateral defender, LD; central midfielder, CM; lateral midfielder, LM; forward, FW), laterality (right-footed vs. left-footed) and field zone (central vs. lateral), and (b) analyze the relationship between anthropometric characteristics (age, weight, height, body mass and fat mass) and non-linear locomotion workload. Thirty professional soccer players (age: 26.57±5.56 years) were tracked during the 2017-2018 season during friendly, national and international matches (38 total games) using inertial measurement devices. CentF and COD were the variables extracted for analysis. A one-way ANOVA was used for playing position comparison, a t-test for laterality and field zone, and Pearson's correlation coefficient to analyze relationships between anthropometric characteristics and dependent variables. There were differences by playing position in COD (556.33-to-412.18), R20COD (484.36-to-354.81) and R60COD (48.38-to-38.61) (p < .01; ωp2 = 0.03-to-0.05; CD>CM>LD>LM = FW); in CODHIA (49.75-to-37.11), R20CODHIA (16.04-to-9.11) and R60CODHIA (10.64-to-9.11) (p < .01; ωp2 = 0.03-to-0.07; CM>FW>LM>CD = LD); in CODSPRINT (14.56-to-8.40) and R20CODSPRINT (3.29-to-1.40) (p < .01; ωp2 = 0.03-to-0.04; FW = LM = CM>CD = LD); and in CentFMAX both in clockwise (992.04-to-902.09N) and counterclockwise (999.24-to-872.61N) directions (p < .02; ωp2 = 0.02-to-0.07; FW = CD>CM = LM = LD). The highest values of counterclockwise CentF were performed by left-footed players in the central zone (p < .001; d = 0.71-to-1.44) and clockwise CentF by right-footed players (p < .001; d = 0.04-to-0.55) in the lateral field zone. Moderate correlations were found between age, body mass and high intensity/sprints COD and repeated COD ability (p < .05; r = 0.235-to-0.383). Therefore, team staff should consider anthropometric characteristics, playing position, laterality and field zone to individualize training workload related to non-linear locomotion in soccer.

Influence of Contextual Variables in the Changes of Direction and Centripetal Force Generated during an Elite-Level Soccer Team Season.

The study of the contextual variables that affect soccer performance is important to be able to reproduce the competition context during the training sessions. Therefore, the aim of the present study was to evaluate the effect of match outcome as related to goal difference (large win, >2 goals, LW; narrow win, 1-2 goals, NW; drawing, D; narrow loss, 1-2 goals, NL; or large loss, >2 goals, LL), match location (home, H; away, A; neutral, N), type of competition (international, INT; national, NAT; friendly, F), phase of the season (summer preseason, SPS; in-season 1, IS1; winter preseason, WPS; in-season 2), and the field surface (natural grass, NG; artificial turf, TF) on the change of direction (COD) and centripetal force (CentF) generated during official games. Thirty male elite-level soccer players (age: 26.57 ± 5.56 years) were assessed while using WIMU PROTM inertial devices (RealTrack Systems, Almeria, Spain) in 38 matches during the 2017-2018 season, selecting for analysis the number of COD at different intensities and the CentF, depending on the turn direction. Statistical analyses comprised a one-way ANOVA with the Bonferroni post-hoc and t-test for independent samples. The main results showed that the match outcome (ωp² = 0.01-0.04; NW = D = NL > LL), match location (ωp² = 0.01-0.06; A = N > H), type of competition (ωp² = 0.01-0.02; INT > NAT > F), and period of the season (ωp² = 0.01-0.02; SPS = IS1 = WPS > IS2) all exert some influence. No effect was found for the playing surface. Therefore, match outcome, match location, type of competition, and period of the season influence the demands of centripetal force and changes of direction. These aspects should be considered in the design of training sessions and microcycle workload planning during the season to improve competitive success.

Using an Inertial Device (WIMU PRO) to Quantify Neuromuscular Load in Running: Reliability, Convergent Validity, and Influence of Type of Surface and Device Location.

Gómez-Carmona, CD, Bastida-Castillo, A, González-Custodio, A, Olcina, G, and Pino-Ortega, J. Using an inertial device (WIMU PRO) to quantify neuromuscular load in running: reliability, convergent validity, and influence of type of surface and device location. J Strength Cond Res 34(2): 365-373, 2020-Currently, the use of accelerometers in sport is increasing, and thus, the devices are required to be valid and reliable. This study tested (a) the reliability and validity of WIMU PRO accelerometers to measure PlayerLoad (PL) and (b) the influence of speed, inertial device location, and type of surface where the incremental test is performed. Twenty resistance-trained men (age: 27.32 ± 6.65 years; height: 1.74 ± 0.03 m; body mass: 68.96 ± 4.37 kg; and body mass index: 22.76 ± 1.11 kg·m) volunteered to participate in the study that lasted 5 weeks. Four progressive incremental tests were performed in treadmill and athletic track conditions. External load variable (PL) and physiological variables (heart rate [HR] and SmO2) were recorded by 4 WIMU PRO inertial devices (scapulae, center of mass, knee, and ankle), a GARMIN HR band, and a MOXY near-infrared spectroscopy device, respectively. High reliability was found on both types of surface, showing the best values at the ankle (treadmill: intraclass correlation coefficient [ICC] = 0.99, coefficient of variation [CV] = 4.65%; track: ICC = 0.96, CV = 6.54%). A nearly perfect convergent validity was shown with HRAVG (r = 0.99) and a moderate one with SmO2 (r = -0.69). Significant differences in the PL variable between surfaces were reported in all locations except the scapulae (p = 0.173), and the higher values were found on the track. In the analysis per location, the ankle location reported the highest values at all speeds and on the 2 surfaces analyzed. Assessment needs to be individualized, due to the great variability of gait biomechanics among subjects. The accelerometer location should be chosen according to the purpose of the measurement, with the ankle location being recommended for neuromuscular load analysis in running.

Lower-limb Dynamics of Muscle Oxygen Saturation During the Back-squat Exercise: Effects of Training Load and Effort Level.

Gómez-Carmona, CD, Bastida-Castillo, A, Rojas-Valverde, D, de la Cruz Sánchez, E, García-Rubio, J, Ibáñez, SJ, and Pino-Ortega, J. Lower-limb dynamics of muscle oxygen saturation during the back-squat exercise: effects of training load and effort level. J Strength Cond Res 34(5): 1227-1236, 2020-The aim of this study was to analyze the effect of strength training on lower limb muscle oxygenation. The sample consisted of 12 male subjects (22.4 ± 1.73 years; 1.81 ± 0.08 cm height and 77.76 ± 8.77 kg body mass). Six different strength training stimuli were analyzed, based on the training variables: load (60-75% 1 repetition maximum [1RM]) and level of effort (LE) (E1: 4 × 8 [20RM], E2: 4 × 12 [20RM], E3: 4 × 16 [20RM], E4: 4 × 4 [10RM], E5: 4 × 6 [10RM], and E6: 4 × 8 [10RM]) in the squat exercise up to 90° with a 2-second stop between repetitions to avoid the myotatic reflex. Oxygen saturation at the beginning of the series (SmO2start), oxygen saturation at the end of the series (SmO2stop), percentage of oxygen saturation loss (▽%SmO2), and reoxygenation time (SmO2recT) were assessed using a near-infrared spectroscopy device. In addition, the percentage of mean propulsive velocity loss (%MPVL) was recorded using a linear transducer. The results suggested an influence of LE and training load on muscle oxygenation. A greater LE was directly associated with SmO2recT (r = 0.864), ▽%SmO2 (r = 0.873), and %MPVL (r = 0.883) and inversely with SmO2stop (r = -0.871). When the same LE was used (E1 vs. E4, E2 vs. E5, and E3 vs. E6), it was found that the stimuli with a higher load had a lower SmO2recT, ▽%SmO2, and %MPVL and a higher SmO2stop. Muscle oxygen saturation was found to be minimal (%SmO2 = 0) in stimuli with a LE greater than 60% (E3 and E6). The SmO2 variables studied in the present research could be considered as an easier and more useful method for understanding skeletal muscle fatigue during resistance training.

Monopodal Postural Stability Assessment by Wireless Inertial Measurement Units Through the Fast Fourier Transform.

OBJECTIVES: (1) To describe the fast Fourier transform (FFT) multijoint as monopodal postural stability measurement in well-trained athletes, (2) to compare the within-subject FFT between laterality, joints, and body segments, and (3) to establish the within- and between-subject relationship between joints. METHODS: Twelve national-level basketball players participated voluntarily in this investigation. The participants performed two 60-second repetitions of a monopodal stability test (1 repetition with each lower limb), separated by 3 minutes of active recovery. All tests were recorded by 4 WIMU PRO™ inertial devices located on the ankle, knee, lumbar spine, and thoracic spine. The main variable was total acceleration, where the FFT was applied. RESULTS: The higher instability results were found in the ankle and in the nondominant lower limb (dominant = 1.131 [0.122] a.u. (arbitrary units); nondominant = 1.141 [0.172] a.u). In the body segment analysis, the greater percentage of differences (%diff) were shown between lumbar spine and knee in the dominant (%diff = -2.989%; d = 0.87) and nondominant (%diff = -3.243%; d = 0.90) lower limb. Finally, very large between-subjects variability was found in all joints and body segments. CONCLUSIONS: The described protocol is proposed for monopodal postural stability assessment, being useful to provide information about the stability of joints and the body segment between joints. Besides, a within-subject analysis is recommended, and the FFT calculation will enable a linear analysis of each test.

Analysis of playing position and match statusrelated differences in external load demands on amateur handball: a case study / Análise das diferenças de posição de jogo e status de jogo nas demandas de carga externa do handebol amador: um estudo de caso

Abstract Currently, the load quantification during training and competition in all sports is important to injury prevention, design specific training sessions, and player performance enhancement. The present study aimed to describe the external load profile of amateur-level handball players and to compare the playing position and match outcome-related differences in an official 2nd Regional Division male official match. 19 handball players were monitored by WIMU PROTM electronic performance and tracking systems (EPTS) with ultrawide-band (UWB) indoor location technology. Statistical analysis was composed of a t-student independent sample test and one-way ANOVA with Bonferroni posthoc. In amateur handball, most demands are composed of aerobic intensity displacements (<12 km/h, 76% playing time) and low-intensity impacts (<5G). Differences were found between playing positions where wingers obtained the greatest values in high-intensity actions, centers in the volume of demands, and defensive specialist players in impacts. Besides, the winning teams performed greater high-intensity demands both in displacements and speed changes. In conclusion, the present results realized the first approximation to handball amateur demands, considering the playing role and match status-related demands to design specific training plans.

Resumo Atualmente, a quantificação da carga durante o treino e competição em todos os desportos é importante para a prevenção de lesões, sessões de treino específicas e melhoria do desempenho dos jogadores. Os objetivos do presente estudo foram descrever o perfil de carga externa dos jogadores de handebol a nível amador e comparar a posição de jogo e as diferenças relacionadas com os resultados de um jogo oficial da 2ª Divisão Regional masculino. Foram analisados 19 jogadores de handebol por meio do WIMU PROTM electronic performance and tracking systems (EPTS) com tecnologia de localização em interiores ultrawide-band (UWB). A análise estatística foi composta por um teste T para amostra independente e ANOVA unidirecional com posthoc de Bonferroni. No handebol amador, as maiores exigências são compostas por deslocamentos de intensidade aeróbica (<12 km/h, 76% de tempo de jogo) e impactos de baixa intensidade (<5G). Foram encontradas diferenças entre as posições de jogo em que os alas obtiveram os maiores valores em ações de alta intensidade, centros no volume de exigência e jogadores defensivos especializados em impactos. Além disso, as equipes vencedoras realizaram maiores exigências de alta intensidade, tanto em deslocamentos como em mudanças de velocidade. Esses resultados fazem a primeira aproximação às exigências do handebol amador, considerando as exigências relacionadas com o papel de jogo e status de jogo para desenhar planos de treino específicos.

Influencia de la modificación de la lógica interna en las emociones percibidas en estudiantes adolescentes durante las sesiones de expresión corporal / Influência da modificação da lógica interna nas emoções percebidas em adolescentes escolares durante as sessões de expressão corporal / Influence of changes in internal logic on emotions perceived in school teenagers students during body expression sessions

El objetivo de esta investigación es analizar la influencia de la modificación de la lógica interna en las emociones percibidas durante las actividades de expresión corporal en alumnos de educación secundaria. Ochenta alumnos (edad: 13.01±0.98 años; sexo: chicos n=49, chicas n=31; curso escolar: 1º ESO n=28, 2º ESO n=30, 3º ESO n=22) participaron voluntariamente en este estudio. Se realizaron dos sesiones compuestas por cinco actividades, separadas por una semana, donde se modificó la lógica interna entre sesiones. Se utilizó la Escala de Juegos y Emociones Deportivas (GES) modificada para el análisis de las emociones. Una modificación en la lógica interna influye directamente en las emociones negativas, manteniéndose altos los valores de emociones positivas. La satisfacción durante la práctica esta relacionada con la emoción de la alegría e inversamente relacionada con la emoción de la vergüenza. En conclusión, el trabajo y análisis de emociones es importante para alcanzar un mayor placer y satisfacción en los alumnos

O objetivo desta pesquisa é analisar a influência da modificação da lógica interna nas emoções percebidas durante as atividades de expressão corporal em alunos do ensino médio. Oitenta estudantes (idade: 13,01±0,98 anos, sexo: meninos n=49, meninas n=31, ano escolar: 1ºESO n=28, 2ºESO n=30, 3ºESO n=22) participaram voluntariamente deste estudo. Duas sessões foram compostas por cinco atividades, separadas por uma semana, em que a lógica interna entre sessões foi modificada. Foi utilizada a Escala de Jogos e Emoções Esportivas (GES) modificada para a análise das emoções. Uma modificação na lógica interna influencia diretamente as emoções negativas, mantendo altos os valores das emoções positivas. A satisfação durante a prática está relacionada à emoção da alegria e inversamente relacionada à vergonha da emoção. Em conclusão, o trabalho e análise de emoções é importante para alcançar maior prazer e satisfação nos alunos

This study analyzed the influence of changes in internal logic on emotions perceived during body expression lessons with secondary education students. Participants were 80 volunteers (age: 13.01±0.98 years; sex: boys n=49, girls n=31; school year of mandatory secondary education: 1st n=28, 2nd n=30, 3rd n=22). Two sessions were performed, separated by 7 days, with five activities each. In each session, the internal logic of the activities was changed. The Games and Emotions Scale (GES) was used to analyze the perceived emotions. A change in internal logic directly influences negative emotions, keeping scores of positive emotions high. Satisfaction during practice is related to emotion of joy and inversely related to the emotion of shame. In conclusion, to work and analyze emotions perceived by the students is important to increase their enjoyment and satisfaction

Player Load and Metabolic Power Dynamics as Load Quantifiers in Soccer.

There has recently been an increase in quantification and objective analysis of soccer performance due to improvements in technology using load indexes such as Player Load (PL) and Metabolic Power (MP). The objectives of this study were: (1) to describe the performance of PL and MP in competition according to the specific role, match-to- match variation, periods of play, game location and match status according to game periods, and (2) to analyze the relationship between both indexes. Twenty-one national-level soccer players were distributed in the following specific positional roles: external defenders (ED) (n = 4), central defenders (CD) (n = 4), midfielders (M) (n = 5), external midfielders (EM) (n = 4) and attackers (A) (n = 4). A total of 12 matches played by a Spanish Third Division team during the 2016/2017 season were analyzed. WIMU PROTM inertial devices (RealTrack System, Almeria, Spain) were used for recording the data. The main results were: (1) a performance reduction in both variables over the course of match time, (2) significant differences in both variables based on the specific position, (3) differences in physical demands during the season matches, (4) winning during a game period and the condition of being the visitor team provoked higher demands, and (5) a high correlation between both variables in soccer. In conclusion, different contextual variables influence the external load demands; both indexes are related so they could be used for external load quantification, and it is necessary to analyze physical demands of the competition for a specific and individualized load design in training sessions.

Impact of Contextual Factors on External Load During a Congested-Fixture Tournament in Elite U'18 Basketball Players.

An understanding of basketball physical demands during official matches is fundamental for designing specific training, tactical, and strategic plans as well as recovery methods during congested fixture periods. Such assessments can be performed using wearable indoor time motion tracking systems. The purpose of this study was to analyze the time-motion profile of under 18-years of age (U'18) basketball players and compare their physical demands in relation to team ranking, playing position, match periods and consecutive matches during a 7-day tournament. Relative Distance (RD), percentage of High-Intensity Running (%HIR), Player Load (PL), Acceleration (Acc), Deceleration (Dec), Peak Speed (PSpeed), and Peak Acceleration (PAcc) were recorded from 94 players (13 centers, 47 forwards, and 34 guards) belonging to eight elite teams (age: 17.6 ± 0.8 years; height: 1.91 ± 0.08 m; body mass: 82.5 ± 8.8 kg). WIMU PROTM inertial measurement units with ultra-wide band (UWB) indoor-tracking technology recorded 13 matches during the Adidas Next Generation Tournament Finals in the 2016-2017 season. Paired t-tests and one-way analyses of variance with omega partial squared ( ω p 2 ) and Cohen's effect sizes (d) were used to analyze for differences between variables. According to team quality, the best teams had lower RD (p = 0.04; d = -0.14). Guards presented higher RD (p < 0.01; ω p 2 = 0.03), PSpeed (p < 0.01; ω p 2 = 0.01) and PAcc (p < 0.01; ω p 2 = 0.02) compared to forwards and centers. The first quarter showed differences with higher RD (p < 0.01; ω p 2 = 0.03), %HIR (p < 0.01; ω p 2 = 0.02), and PL (p < 0.01; ω p 2 = 0.04) compared to all other quarters. The third match of the tournament presented higher demands in RD (p < 0.01; ω p 2 = 0.03), HIR (p < 0.01; ω p 2 = 0.01) and PL (p < 0.01; ω p 2 = 0.02) compared with the first two matches. This study showed that team quality, playing position, match period, and consecutive matches throughout an U'18 basketball tournament influenced the kinematic demands experienced by players during official competition. Therefore, each of these contextual factors should be considered in managing the load and developing individualized strategies for players in tournament settings.

Comparing accuracy between global positioning systems and ultra-wideband-based position tracking systems used for tactical analyses in soccer.

Current studies have reported high accuracy in global positioning system (GPS) and recently developed ultra-wideband (UWB)-based tracking systems for monitoring time - motion patterns. The accuracy and reliability of both systems may be different in tactical analysis application, an aspect that has never been studied previously. The aims of the present study were: (i) to determine and compare the accuracy of GPS and UWB technologies in soccer players' positions (ii) to compare the tactical application of both systems. Following institutional ethical approval and familiarisation, 14 well-trained soccer players performed tests around five courses: (a) field perimeter, (b) halfway line, (c) centre circle, (d) perimeter of the penalty area, and (e) semicircle penalty area. Also, a small-sided game was played monitored with WIMUPRO™ to determine real and practical differences in accuracy of both systems in tactical analysis. For the GPS, the mean absolute error (N = 9445) of "x" and "y" coordinates was 41.23 ± 17.31 cm and 47.6 ± 8.97 cm, respectively. For UWB, it was 9.57 ± 2.66 cm and 7.15 ± 2.62 cm. The results of the "x" and "y" accuracy comparison were significantly lower in all cases (p < 0.05) with an ES of 0.78 and 0.95, respectively. In a real practical application, the differences of both systems reached 8.31% in typical tactical variables (ES = 0.11). In contrast to GPS-10Hz, UWB WIMUPRO™-20 Hz has been demonstrated to be an acceptable technology to estimate the position of players on the pitch with high accuracy and be a useful, automatic, and portable instrument for tactical analysis measurement.

Validity and reliability of an inertial device (WIMU PROTM) to quantify physical activity level through steps measurement.

BACKGROUND: Currently, there is an increase in the application of accelerometers to quantify physical activity level through daily steps, and therefore, it is required that the devices are valid and reliable. The current study tested the validity of the WIMU PROTM inertial device in steps detection and the inter-device reliability for steps measurement. METHODS: Ten endurance-trained men volunteered to participate in this study (height: 1.78±0.05 m; body mass: 72.96±4.2 kg). Twelve trials of 40.32 m at different speeds (four trials at each speed) were performed: 1) walking (<5 km/h); 2) jogging (5-10 km/h) and running (10-15 km/h). The video analysis was used as criterion to assess validity, while, two WIMU PROTM inertial devices were compared to assess between-unit reliability. RESULTS: A near-perfect validity between video analysis and WIMU PROTM (ICC=0.999; bias=0.03) and a very good reliability between WIMU PROTM devices (bias=-0.01; CV=0.02%) was found. The highest values were found at walking (ICC=0.999) and the lowest values were found at running (ICC=0.995). CONCLUSIONS: WIMU PROTM is a reliable and valid device to quantify physical activity level through steps measurement.

Accuracy, intra- and inter-unit reliability, and comparison between GPS and UWB-based position-tracking systems used for time-motion analyses in soccer.

There is interest in the accuracy and inter-unit reliability of position-tracking systems to monitor players. Research into this technology, although relatively recent, has grown exponentially in the last years, and it is difficult to find professional team sport that does not use Global Positioning System (GPS) technology at least. The aim of this study is to know the accuracy of both GPS-based and Ultra Wide Band (UWB)-based systems on a soccer field and their inter- and intra-unit reliability. A secondary aim is to compare them for practical applications in sport science. Following institutional ethical approval and familiarization, 10 healthy and well-trained former soccer players (20 ± 1.6 years, 1.76 ± 0.08 cm, and 69.5 ± 9.8 kg) performed three course tests: (i) linear course, (ii) circular course, and (iii) a zig-zag course, all using UWB and GPS technologies. The average speed and distance covered were compared with timing gates and the real distance as references. The UWB technology showed better accuracy (bias: 0.57-5.85%), test-retest reliability (%TEM: 1.19), and inter-unit reliability (bias: 0.18) in determining distance covered than the GPS technology (bias: 0.69-6.05%; %TEM: 1.47; bias: 0.25) overall. Also, UWB showed better results (bias: 0.09; ICC: 0.979; bias: 0.01) for mean velocity measurement than GPS (bias: 0.18; ICC: 0.951; bias: 0.03).