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The aims of this study were to assess the criterion validity and the accuracy in estimating maximal aerobic power (V[O.sub.2]max) of a popular shuttle running field test (multistage fitness test [MSFT]) in women soccer players. Twenty-six women soccer players (age 12.1 [+ or -] 0.9 years, body mass 50 [+ or -] 9.2 kg, and height 155 [+ or -] 5.7 cm) were tested over separate occasions for V[O.sub.2]max (V[O.sub.2]max test) and MSFT performances with (MSFT peak oxygen uptake) or without (MSFT) gas analysis. Data showed that the V[O.sub.2]max estimation using the MSFT predicting nomogram was significantly lower than MSFT V[O.sub.2]peak (32.7 [+ or -] 3.9 vs. 40.1 [+ or -] 5.9 ml x [kg.sup.-1] x [min.sup.-1]; p < 0.001). No significant difference between V[O.sub.2]max test and MSFT for maximal V[O.sub.2] and heart rate (HR) was observed (38.7 [+ or -] 4.7 vs. 40.1 [+ or -] 5.9 ml x [kg.sup.-1] x [min.sup.-1] and 203 [+ or -] 5.3 vs. 200 [+ or -] 9.8 beats x [min.sup.-1]; p > 0.05; n = 15). The MSFT performance (950 [+ or -] 213 m) results significantly correlated with MSFT- V[O.sub.2]peak (r = 0.70; p < 0.001). This study results showed that the MSFT predicting nomogram significantly underestimated V[O.sub.2]peak. Average difference being in the order of 23% of the estimated value. Resulting MSFT- V[O.sub.2]peak significantly related to MSFT performance, and this test may be considered as an indirect measure of individual V[O.sub.2]max in young women soccer players. Furthermore, MSFT may be used as a valid test to assess V[O.sub.2]peak and HRmax when a portable gas analyzer and a HR monitor are available. However, great individual differences may occur. In light of this study results, it is suggested to consider MSFT performance (distance covered) and not estimated V[O.sub.2]max when dealing with young women soccer players. KEY WORDS association football, team sports, shuttle running, maximal oxygen uptake, aerobic fitness

Objectives: The aim of this study was to assess the relationship between the countermovement jump (CMJ) and sprint performance of professional football players, and to determine which strength and speed elements assessed by the CMJ translate into effective running. Methods: The research sample comprised 87 male professional football players (age 23.7 ± 4.20 years; body mass 82.33 ± 6.56 kg; body height 1.86 ± 0.05 m) who performed the CMJ on a dual-force platform, as well as the 30 m sprint test. The time and velocity of the run were recorded by photocells at 0, 5, 10, and 30 m of the distance. Results: No significant differences were noted in the time or velocity of the sprint over the initial 5 m between the groups of football players with a higher and lower braking rate of force development (RFD) in the CMJ (p > 0.05). However, at subsequent intervals (5–10 m and 10–30 m), players with a higher braking RFD achieved significantly better time and velocity than those with a lower RFD. Significant correlations in the group with a lower braking RFD between the CMJ and sprint variables occurred in the propulsion phase of the CMJ and most of them were in the first interval (0–5 m). In the group with a higher braking RFD, significant relationships were visible in both the propulsion (concentric) and braking (eccentric) phases of the CMJ, mainly during the second and third intervals of the sprint test. Conclusions: The noted observations may suggest that the relationship between strength and running performance is more complex than previously indicated, and that higher strength in the CMJ does not fully correlate with better sprinting. Therefore, it has been hypothesized that training aimed at generally increasing strength may not always be fully beneficial for running performance in football players and hence specific training guidelines are suggested for targeted strengthening of the required muscle performance characteristics. This may possibly contribute to reducing the unnecessary muscle overload during both training and matches, thereby preventing sports-related injuries. [ABSTRACT FROM AUTHOR]

Purpose: To examined the time-course of the early and late phase of the rate of voluntary force development (RVFD) and muscle damage markers after downhill running. Methods: Ten recreational runners performed a 30-min downhill run at 10 km h−1 and −20% (−11.3°) on a motorized treadmill. At baseline and each day up to 4 days RVFD, knee extensors maximum voluntary isometric force (MVIC), serum creatine kinase (CK) concentration, quadriceps swelling, and soreness were assessed. The early (0–50 ms) and late (100–200 ms) phase of the RVFD, as well as the force developed at 50 and 200 ms, were also determined. Results: MVIC showed moderate decrements (p < 0.05) and recovered after 4 days (p > 0.05). Force at 50 ms and the early phase were not impaired (p > 0.05). Conversely, force at 200 ms and the late phase showed moderate decrements (p < 0.05) and recovered after 3 and 4 days, respectively (p > 0.05). CK concentration, quadriceps swelling, and soreness increased (p < 0.05) were overall fully resolved after 4 days (p > 0.05). Conclusion: Downhill running affected the knee extensors RVFD late but not early phase. The RVFD late phase may be used as an additional marker of muscle damage in trail running. [ABSTRACT FROM AUTHOR]