Search

The objectives of this study were to compare conventional preservatives used in milk analysis, including potassium dichromate and bronopol with a non-toxic and biodegradable preservative such as methylene blue, to verify their effectiveness and limitations of use. This was achieved by comparing their effects on raw milk composition at different storage temperatures. The best performing preservative doses were 0.1, 0.036 and 0.01% for potassium dichromate, bronopol, and methylene blue respectively. Raw milk composition was significantly affected (p < 0.05) during the storage period at 25°C for all tested preservatives. However, at 4°C, potassium dichromate and bronopol preservatives maintained stable milk composition during 10 days of storage, whereas methylene blue maintained stable milk composition for three days. Methylene blue can be considered as an environmentally friendly and safe alternative for short-term preservation of refrigerated raw milk samples. [ABSTRACT FROM AUTHOR]

For yoghurts were made from milk with different levels of somatic cell count (SCC) (low 95,000 cells ml− 1, intermediate 398,000 cells ml− 1 and high 1,150,000 cells ml− 1). Yoghurt samples were analysed for the degree of proteolysis, lipolysis (free fatty acid (FFA) content), acidity, pH and apparent viscosity on days 1, 14 and 28. The SCC had no significant effect ( p>0.05) on either the acidity or the pH of the yoghurt after 1 day of cold storage. However, significant effects ( p < 0.05) of SCC were observed after 14 and 28 days of storage. Yoghurt samples made from intermediate and high SCC milk showed higher viscosity ( p < 0.05) and lower ( p < 0.05) casein content on days 14 and 28 of cold storage than yoghurt made from low SCC milk. High FFA concentrations ( p < 0.05) were observed only in yoghurt made from high SCC milk. High SCC in milk increased both proteolysis and lipolysis in yoghurt during storage. [ABSTRACT FROM AUTHOR]

Background: The aerobic capacity of soccer players substantially influences their technical performance and tactical choices. Thus, the assessment of soccer players' aerobic performance should be of interest for soccer coaches in order to evaluate and improve their endurance training sessions. In this study, we present a new test to assess aerobic performance in soccer by means of a specific dribbling track: the Hoff test. We further determined whether improvement in maximal oxygen uptake was reflected in increased distance covered in the Hoff test. Methods: We tested 18 male soccer players (14 years old) both in the laboratory and using the Hoff test before and after 8 weeks of soccer training. Results: The distance covered in the Hoff test correlated significantly with maximum oxygen uptake, and improved by 9.6% during the 8 week training period, while maximum oxygen uptake and running economy improved by 12 and 10%, respectively. Backward multiple regression showed maximum oxygen uptake to be the main explanatory variable for the distance covered in the Hoff test. Conclusion: The present study demonstrated a significant correlation between laboratory testing of VO2max and performance in the Hoff test. Furthermore, training induced improvements in VO2max were reflected in improved performance in the Hoff test. We suggest that it should be a goal for active U-15 soccer players to cover more than 2100 metres in the Hoff test, as this requires a VO2max of above 200 ml/kg0.75/min, which should serve as a minimum in modern soccer. [ABSTRACT FROM AUTHOR]

Aim: To determine if there are correlations between the physical fitness of young soccer players assessed by field and laboratory testing. Methods: Thirty four male soccer players took part in the study (mean (SD) age 17.5 (1.1) years, height 177.8 (6.7) cm, weight 70.5 (6.4) kg). Maximal oxygen uptake (Vo2MAX) during treadmill running and vertical lump height on a force platform were measured in the laboratory. Field tests consisted of a soccer specific endurance test (Bangsbo test) and 30 m sprint with 10 m lap times. Results: The Bangsbo test correlated with the lowest velocity associated with Vo2MAX (vVo2MAX; R² = 0.55, p < 0.001), but not with Vo2MAX. Sprint times at 30 m and 20 m were related to peak extension velocity and peak extension force measured during vertical jumping, but not to vertical jump height per se. The jumping force and velocity could explain 46% of the 30 m sprint performance (R² = 0.46, p < 0.001). Conclusion: The Bangsbo test and 30 m sprint test correlate with vVo2MAX and vertical jump force and velocity respectively. The Bangsbo test does not give a good estimate of Vo2MAX in young soccer players. [ABSTRACT FROM AUTHOR]

Summary Objectives The aim of this critical review was to discuss performance analysis characteristics and particular physiological demands related to karate kata and kumite . News The intermittent nature of karate has been revealed via kumite 's time-motion analysis, with a 1:1.5 effort-pause ratio during official competition. Karate combat is mainly dependent on the aerobic metabolism. However, decisive actions’ energy is provided by the anaerobic system. Concerning kata , it seems that the fraction of the energy supply is mainly a function of kata 's duration. The high-energy phosphate seems to be the major contributors while the aerobic energy system’ participation rises with the increased kata 's duration. Prospects and projects Future investigations in an ecologically valid environment are needed to support the findings presented in the current review. Conclusion Irrespective of karate's discipline, the aerobic system represents the main energy system, especially in longer kata . Kumite appears to demand much higher metabolic power than kata , regardless of gender, while kata appears to require more ATP-PCr energy system contribution than kumite . [ABSTRACT FROM AUTHOR]

In this study, we examined the effects of a prior run-up on intermittent maximal vertical jump performance. Seven regionally ranked male volleyball players volunteered to participate in the study. They performed three randomized tests: (1) six repeated intermittent maximal jumps (jump condition), (2) six repeated intermittent run-ups (run-up condition), and (3) six repeated run-ups followed by maximal jumps (run-up plus jump condition). All performances were assessed and blood lactate concentration and heart rate were measured before and after each of the tests. Mean ( ± ) jump performance (64.7 ± 2.3&ThickSpace;cm) increased significantly ( P = 0.02) over the course of the jump condition and was significantly higher ( P < 0.001) than for the run-up plus jump condition (58.0 ± 3.2&ThickSpace;cm), which tended to decrease with repetition. Blood lactate concentration was significantly higher in the run-up plus jump condition (3.73 ± 0.24&ThickSpace;mmol · l -1 ) than in the jump (2.61 ± 0.26&ThickSpace;mmol · l -1 , P = 0.02) and run-up (2.86 ± 0.18&ThickSpace;mmol · l -1 , P = 0.03) conditions. The increase in heart rate was significantly higher both in the run-up plus jump condition (33 ± 6 beats · min -1 , P = 0.05) and run-up condition (33 ± 4 beats · min -1 , P = 0.02) than in the jump condition (21 ± 3 beats · min -1 ). The results indicate that the addition of run-ups probably impeded performance in the repetition of vertical jumps. [ABSTRACT FROM AUTHOR]

Objective: To compare aerobic capacity of young and adult elite soccer players using appropriate scaling procedures. Methods: Twenty four male adult (mean (SD) age 24 (2) years, weight 75.7 (7.2) kg, VO2MAX 66.6 (5.2) ml/lbm/min, where lbm is lean body mass in kg) and 21 youth (14(0.4) years, 60.2(7.3) kg, 66.5 (5.9) ml/lbm/min) elite soccer players took part in the study. Allometric equations were used to determine the relation between maximal and submaximal oxygen cost of running (running economy) and body moss. Results: Maximal and submaximal oxygen uptake increased in proportion to body mass raised to the power of 0.72 (0.04) and 0.60 (0.06) respectively. The VO2MAX of adult players was similar to that of the youth players when expressed in direct proportion to body mass--that is, ml/kg/min--but 5% higher (p < 0.05) when expressed using appropriate procedures for scaling. Conversely, compared with seniors, youth players had 13% higher (p < 0.001) energy cost of running--that is, poorer running economy--when expressed as ml/kg/min but not when expressed according to the scaling procedures. Conclusions: Compared with the youth soccer players, VO2MAX in the seniors was underestimated and running economy overestimated when expressed traditionally as ml/lbm/min. The study clearly shows the pitfalls in previous studies when aerobic capacity was evaluated in subjects with different body mass. It further shows that the use of scaling procedures can affect the evaluation of, and the resultant training programme to improve, aerobic capacity. [ABSTRACT FROM AUTHOR]

Summary Purpose The purposes of this study were to compare change of direction speed (CODS) performances between different age categories (i.e., U-10, U-12, U-13, and U-18) and to develop allometric exponents for scaling this quality. Material and method Data were gathered with the participation of 101 male soccer players (mean ± SD; age = 12.5 ± 2.9 years, mass = 44.4 ± 14.7 kg, height = 149.3 ± 17.7 cm, and leg length = 75.7 ± 13.1 cm). All players performed the Illinois change of direction speed test (ICDST). Results U-18 players achieved significantly better results in ICDST compared with the other groups, whereas U-10 players had the lowest performances (F = 48.78, P < 0.0001). In regards to U-12 and U-13 soccer players, no significant differences were established between them ( P > 0.05). The ICDST performances were significantly associated with body mass ( r = −0.58; P < 0.0001), height ( r = −0.75; P < 0.0001) and leg length ( r = −0.75; P < 0.0001). No correlations between allometrically scaled ICDST performance and anthropometric measures were observed (all P > 0.05), indicating the effectiveness of allometric exponents in partialing out the effect of anthropometric measures on ICDST's compared to ratio scaling. Conclusion Results indicated differences in CODS performance among soccer players of different age categories. These results demonstrated that developing allometric exponents are effective in controlling for anthropometric measures. [ABSTRACT FROM AUTHOR]