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).

This study analysed the effect of imposing a pause between the eccentric and concentric phases on the biological within-subject variation of velocity- and power–load isoinertial assessments. Seventeen resistance-trained athletes undertook a progressive loading test in the bench press (BP) and squat (SQ) exercises. Two trials at each load up to the one-repetition maximum (1RM) were performed using 2 techniques executed in random order: with (stop) and without (standard) a 2-s pause between the eccentric and concentric phases of each repetition. The stop technique resulted in a significantly lower coefficient of variation for the whole load–velocity relationship compared to the standard one, in both BP (2.9% vs. 4.1%; P = 0.02) and SQ (2.9% vs. 3.9%; P = 0.01). Test–retest intraclass correlation coefficients (ICCs) were r = 0.61–0.98 for the standard and r = 0.76–0.98 for the stop technique. Bland–Altman analysis showed that the error associated with the standard technique was 37.9% (BP) and 57.5% higher (SQ) than that associated with the stop technique. The biological within-subject variation is significantly reduced when a pause is imposed between the eccentric and concentric phases. Other relevant variables associated to the load–velocity and load–power relationships such as the contribution of the propulsive phase and the load that maximises power output remained basically unchanged.

The purpose of this study was to assess the accuracy of positional data and the inter-unit reliability of an ultra-wide-band (UWB) tracking system. Four well-trained males performed five courses designed for the analysis of x- and y-coordinate accuracy analysis, specifically related to the positional distance variation between the UWB data and the fixed reference lines of a basketball court. This was achieved using geographic information system (GIS) mapping software that calculated, for each interval and participant, the distance from the main axis of displacement and from the opposite side of the court each 0.5 s (x and y coordinate). The accuracy of the results was satisfactory, with a mean absolute error of all estimations for the x-position of 5.2 ± 3.1 cm and for the y-position of 5.8 ± 2.3 cm. Regarding inter-unit reliability, the intra-class correlation coefficient (ICC) value was high for the x-coordinate (0.65) and very high for the y-coordinate (0.85). The main findings of the study were: (i) The accuracy of UWB tracking systems can be considered suitable for practical applications in sport analyses; (ii) position estimations are very precise and acceptable for tactical analyses; (iii) the error of the position estimations does not change significantly across different courses; and (iv) the use of different devices does not significantly affect the measurement error.

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.

In Olympic combat sports, weight cutting is a common practice aimed to take advantage of competing in weight divisions below the athlete's normal weight. Fluid and food restriction in combination with dehydration (sauna and/or exercise induced profuse sweating) are common weight cut methods. However, the resultant hypohydration could adversely affect health and performance outcomes. The aim of this study is to determine which of the routinely used non-invasive measures of dehydration best track urine osmolality, the gold standard non-invasive test. Immediately prior to the official weigh-in of three National Championships, the hydration status of 345 athletes of Olympic combat sports (i.e., taekwondo, boxing and wrestling) was determined using five separate techniques: i) urine osmolality (U_OSM), ii) urine specific gravity (U_SG), iii) urine color (U_COL), iv) bioelectrical impedance analysis (BIA), and v) thirst perception scale (TPS). All techniques were correlated with U_OSM divided into three groups: euhydrated (G₁; U_OSM 250–700 mOsm·kg H₂O⁻¹), dehydrated (G₂; U_OSM 701–1080 mOsm·kg H₂O⁻¹), and severely dehydrated (G₃; U_OSM 1081–1500 mOsm·kg H₂O⁻¹). We found a positive high correlation between the U_OSM and U_SG (r = 0.89: p = 0.000), although this relationship lost strength as dehydration increased (G₁ r = 0.92; G₂ r = 0.73; and G₃ r = 0.65; p = 0.000). U_COL showed a moderate although significant correlation when considering the whole sample (r = 0.743: p = 0.000) and G₁ (r = 0.702: p = 0.000) but low correlation for the two dehydrated groups (r = 0.498–0.398). TPS and BIA showed very low correlation sizes for all groups assessed. In a wide range of pre-competitive hydration status (U_OSM 250–1500 mOsm·kg H₂O⁻¹), U_SG is highly associated with U_OSM while being a more affordable and easy to use technique. U_COL is a suitable tool when U_SG is not available. However, BIA or TPS are not sensitive enough to detect hypohydration at official weight-in before an Olympic combat championship.