Interaction of exercise bioenergetics with pacing behavior predicts track distance running performance

The best possible finishing time for a runner competing in distance track events can be estimated from their critical speed (CS) and the finite amount of energy that can be expended above CS (D'). During tactical races with variable pacing, the runner with the 'best' combination of CS and D' and, therefore, the fastest estimated finishing time prior to the race, does not always win. We hypothesized that final race finishing positions depend on the relationships between the pacing strategy employed, the athletes' initial CS, and their instantaneous D' (i.e., D' balance) as the race unfolds. Using publicly available data from the 2017 IAAF World Championships men's 5,000 m and 10,000 m races, race speed, CS, and D' balance were calculated. The correlation between D' balance and actual finishing positions was non-significant utilizing start-line values but improved to R2 > 0.90 as both races progressed. The D' balance with 400 m remaining was strongly associated with both final 400 m split time and proximity to the winner. Athletes who exhausted their D' were unable to hold pace with the leaders, whereas a high D´ remaining enabled a fast final 400 m and a high finishing position. The D' balance model was able to accurately predict finishing positions in both a 'slow' 5,000 m and a 'fast' 10,000 m race. These results indicate that while CS and D' can characterize an athlete's performance capabilities prior to the start, the pacing strategy that optimizes D' utilization significantly impacts final race outcome.

Elemental Carbon and Its Fractions during Evolved Gas Analysis with Respect to Pyrolytic Carbon and Split Time

We demonstrated the relationships between elemental carbon (EC) and EC fractions during evolved gas analysis (EGA) for PM2.5 sampled at KOREATECH from 29 March 2018 to 12 May 2018. The EC concentrations were compared to the concentrations of equivalent black carbon to confirm that the level of EC concentrations analyzed in this study was valid. Among various EC fractions and their combination, EC1+EC3 fractions were best correlated with the EC concentrations. Especially, dominant EC fraction was related with the dependence of carbon oxidation quantity on the oxidation temperature. We also examined the relationships between pyrolytic carbon (PyC) and EC concentration with respect to the split time. PyC was correlated with the split time in the phase of oxygen-helium mixture. PyC was close to zero for the split time in the helium phase. It is novel, as far as the authors know, that the correlation between PyC and the split time under NIOSH 5040 protocol was reported with regard to EGA. We believe that our study helps to identify what causes uncertainty in the quantification of PyC.

Cladode size and collection time for pitahaya propagation

ABSTRACT Cutting is a propagation method with the advantages of early production and uniform cultivation. Some factors influence propagation and rooting, such as the cutting size and the time of year the collection is performed. Thus, the present work aimed to evaluate the ideal size of white-fleshed red pitahaya cladodes and the time of their collection for crop propagation by cutting in view of the physiological quality of the produced clonal plants to enable more appropriate cultural management and increase the cultivation area. The experiment was conducted at the Faculty of Engineering (UNESP) using three cladode sizes (cuttings) with lengths of 10, 20 and 40 cm collected in two seasons (summer and winter). The experimental design used was completely randomized in a split-time scheme, with no dependence on the factors and 20 replicates. Evaluations of the biometric factors related to sprouts and cladode rooting were carried out 60 days after cutting. According to the results, there were significant differences among treatments, with a significant interaction of the number of sprouts. It can be concluded that, regarding the size of the cladodes, it is recommended, when possible, to use cladodes 40 cm in length; regarding the time of collection, it is recommended that collection be conducted in the winter period to favor the development of better-quality clonal plants.

Changes in sprint performance and sagittal plane kinematics after heavy resisted sprint training in professional soccer players

Background Sprint performance is an essential skill to target within soccer, which can be likely achieved with a variety of methods, including different on-field training options. One such method could be heavy resisted sprint training. However, the effects of such overload on sprint performance and the related kinetic changes are unknown in a professional setting. Another unknown factor is whether violating kinematic specificity via heavy resistance will lead to changes in unloaded sprinting kinematics. We investigated whether heavy resisted sled training (HS) affects sprint performance, kinetics, sagittal plane kinematics, and spatiotemporal parameters in professional male soccer players. Methods After familiarization, a nine-week training protocol and a two-week taper was completed with sprint performance and force-velocity (FV) profiles compared before and after. Out of the two recruited homogenous soccer teams (N = 32, age: 24.1 ± 5.1 years: height: 180 ± 10 cm; body-mass: 76.7 ± 7.7 kg, 30-m split-time: 4.63 ± 0.13 s), one was used as a control group continuing training as normal with no systematic acceleration training (CON, N = 13), while the intervention team was matched into two HS subgroups based on their sprint performance. Subgroup one trained with a resistance that induced a 60% velocity decrement from maximal velocity (N = 10, HS60%) and subgroup two used a 50% velocity decrement resistance (N = 9, HS50%) based on individual load-velocity profiles. Results Both heavy resistance subgroups improved significantly all 10–30-m split times (p < 0.05, d = − 1.25; −0.62). Post-hoc analysis showed that HS50% improved significantly more compared to CON in 0–10-m split-time (d = 1.03) and peak power (d = 1.16). Initial maximal theoretical horizontal force capacity (F0) and sprint FV-sprint profile properties showed a significant moderate relationship with F0 adaptation potential (p < 0.05). No significant differences in sprinting kinematics or spatiotemporal variables were observed that remained under the between-session minimal detectable change. Conclusion With appropriate coaching, heavy resisted sprint training could be one pragmatic option to assist improvements in sprint performance without adverse changes in sprinting kinematics in professional soccer players. Assessing each player’s initial individual sprint FV-profile may assist in predicting adaptation potential. More studies are needed that compare heavy resisted sprinting in randomized conditions.

Analyse Success Model of Split Time and Cut-Off Point Values of Physical Demands to Keep Category in Semi-Professional Football Players

The aim of this study was to analyse different success models and split time on cut-off point values on physical demands to keep category in semi-professional football players. An ad hoc observational controlled study was carried out with a total of ten (840 match data) outfield main players (25.2 ± 6.3 years, 1.79 ± 0.75 m, 74.9 ± 5.8 kg and 16.5 ± 6 years of football experience) and monitored using 15 Hz GPS devices. During 14 official matches from the Spanish division B in the 2016/2017 season, match data were coded considering the situational variable (score) and classified by match results (winning, losing or drawing). The results show significant differences between high-intensity attributes criteria that considered split time in velocity zones of 0–15 min (p = 0.043, ηp2 = 0.065, medium), 30–45 min (p = 0.010, ηp2 = 0.094, medium) and 60–75 min (p = 0.015, ηp2 = 0.086, medium), as well as sprint 60–75 min (p = 0.042, ηp2 = 0.066, medium) and 75–90 min (p = 0.002, ηp2 = 0.129, medium). Decision tree induction was applied to reduce the disparity range of data according to six 15-min intervals and to determine the cut-off point values for every parameter combination. It was possible to establish multivariate models for the main high-intensity actions criteria, allowing the establishment of all rules with their attributes and enabling the detection and visualisation of relationships and the pattern sets of variables for determining success.

Pemberian Serbuk Biji Kelor pada Limbah Cair Rumah Pemotongan Ayam Tradisional Mampu Menurunkan Jumlah Escherichia coli

Serbuk biji kelor dapat berperan sebagai koagulan alami untuk memperbaiki kualitas air, mereduksi logam berat, menurunkan jumlah bakteri Escherichia coli dan alga serta sebagai surfaktan / hidrofilik. Penelitian ini bertujuan untuk mengetahui pengaruh serbuk biji kelor pada konsentrasi berbeda terhadap jumlah E. coli pada limbah Rumah Pemotongan Ayam tradisional (RPA). Pada penelitian ini menggunakan Rancangan Acak Kelompok (RAK) pola split-time. Bakteri E. coli dihitung dengan metode penumbuhan pada media EMBA (eosin methylene blue agar). Faktor utama yaitu konsentrasi serbuk biji kelor sebagai berikut ; 0 mg / L, 50 mg / L, 100 mg / L, 150 mg / L dan 200 mg / L, dengan faktor tambahan adalah waktu pengendapan yaitu 0 menit, 20 menit, 40 menit, 60 menit. Hasil sidik ragam menunjukkan bahwa serbuk biji kelor berpengaruh sangat nyata terhadap jumlah bakteri E. coli pada limbah RPA tradisional. Dengan konsentrasi terbaik serbuk biji kelor, 200 mg/L dan lama pengendapan yakni 60 menit, memberikan pengaruh terhadap penurunan jumlah E. coli pada limbah RPA tradisional.