The purpose of this study was to evaluate the standard field tests of flexibility of the lower extremity through their (a) intratrial and test-retest reliability, (b) concurrent validity with respect to a high-precision 3D system for kinematic recording, and (c) factorial validity. Physically active men (n = 84) were tested over 2 separate sessions by means of standard simple devices (kinanthropometry, ruler, and protractor) on the following flexibility tests: leg raise in a supine position, hip abduction test, single-legged knee bend (SLKB), sideward leg splits (SdLS), sit and reach (SR), sideways leg splits, and lengthwise leg splits. Additionally, 17 participants were simultaneously tested by means of a laboratory 3D kinematic analysis system. Most of the tests demonstrated high intratrial and test-retest reliability and concurrent validity. The exceptions were SLKB and SR tests that revealed not only a somewhat lower reliability but also a lower concurrent validity. For estimation of factorial validity, we applied a principal component analysis of the intercorrelations among the evaluated flexibility tests that revealed a single extracted principal component. Strong mutual relationships among them also suggest that very few of them, if not a single one, should be applied within the standard batteries of physical performance tests. We particularly recommend using SdLS over the most frequently used SR not only because of its relatively high reliability and validity but also because of its postural properties. Finally, we conclude that most of the standard field tests of flexibility of the lower extremity based on using inexpensive field equipment could be both reliable and valid and, therefore, justified for use in routine testing.

Karate tournaments consist of two equally important karate disciplines: the kumite and kata competitions. Due to being based both on the distinctive selection of movement techniques and their kinematic and kinetic patterns, we hypothesized that the elite kumite and kata competitors could differ regarding their anthropometric and physical performance profiles. Thirty-one senior male karate competitors of the national karate team (kumite n = 19; kata n = 12) participated in this study. The tests applied included both the assessment of anthropometric (body height, mass and body mass index) and the following physical performance measurements: the adductor and hamstring flexibility (sideward leg splits test), speed and acceleration (20-m sprint test with 10-m acceleration time), explosive power (countermovement and standing triple jump), agility (“T”- test) and aerobic endurance (20-m multistage shuttle run test). The kumite competitors revealed a larger body size through body height (p = 0.01) and mass (p = 0.03), while the differences in body composition were non-significant. The kumite competitors also demonstrated higher acceleration (p = 0.03) and explosive power (standing triple jump; p = 0.03). A 6-7° higher flexibility of the kata competitors remained somewhat below the level of significance (p = 0.09). The findings could be interpreted by the distinctive differences in the movement techniques. Specifically, a higher explosive power could be beneficial for kumite, while both a smaller stature and higher flexibility (particularly of the lower extremity) could be important for the exceptionally low postures of the kata competitors. Although further elucidation is apparently needed, the obtained finding could be of importance for both the early selection and training of karate competitors.

The aim of this study was to evaluate the reliability and sensitivity of variables for the direct assessment of kicking performance in young soccer players. One hundred and six elite young soccer players were divided into 4 age groups (12-15 years). Absolute error (AE), variable error (VE), and constant error (CE) were evaluated as the variables of kicking accuracy, whereas the kicking velocity variables involved the maximum ball velocity (BVmax) and the ball velocity during accurate kicks (BVacc). Results suggested low-to-moderate reliability of the kicking accuracy (intraclass correlation coefficient [ICC] = 0.00-0.67) and high reliability of the kicking velocity variables (ICC = 0.87-0.94). Regarding the sensitivity, most of the variables detected the differences both between the dominant and nondominant legs and among the age groups. Because the evaluated variables should have a property of face validity, the findings obtained generally suggest that AE (and perhaps VE, as the measures of kicking accuracy) and both BVmax and BVacc (as the measures of kicking velocity) could be used within a routine composite test of kicking performance in young elite soccer players. Further development of the evaluated composite test of kicking performance could be based on the involvement of other kicking techniques and on testing the athletes of different ages, levels of skill, or sport specialization.

Although regularly used, the standard strength test (SST) is known to have several shortcomings, such as being based only on sustained maximum forces, and on a relatively large number of trials that expose the tested muscle to rapid fatigue. The purpose of this study was to evaluate alternating consecutive maximum contractions (ACMCs) as a test of the muscle function through its comparison with SST. Twenty-four participants performed both the externally paced isometric ACMC (i.e., series of consecutive maximum force exertions in 2 directions) and SST of the knee extensor and flexor muscle. The derived variables of both tests included the knee extensor and flexor peak forces (PFs) and their maximum rates of development. Movement speed and muscle power output were also assessed through standard maximum performance tests. Both ACMC and SST revealed on average high intratrial (intraclass correlation coefficient [ICC] > 0.80) and moderate-to-high test-retest reliability (ICC > 0.60), and significant (p < 0.05) positive relationships among the PFs and their rates of development of the tested muscles. The variables of both tests also suggested on average moderate correlations with the maximum performance tests. Finally, ACMC variables revealed relatively stable values across a wide range of frequencies including the 'self-selected' one. Although some properties of ACMC could be similar to SST, the important comparative advantages of ACMC could be relatively low and transitional maximum forces exerted, and fewer trials needed for testing 2 antagonistic muscles. Although further research is needed, particularly concerning the external validity and generalizability, we conclude that the ACMC represents a test of muscle function that could be applied either as an alternative or complementary test to SST.

The standard strength test (SST) has been based only on sustained maximum forces, as well as on relatively large number trials needed to record the maximum forces (F) and their rate of development (RFD). The aim of this study was to extend our recent research on alternating consecutive maximum contractions (ACMC) performed by antagonist muscles. Instead of varying the frequency, we explored the properties of ACMC performed at the self-selected frequency and compared it with SST. Knee extensors and flexors were tested in 64 participants. Within-session reliability of F and RFD of the two muscles evaluated through a single ACMC trial proved to be high (ICC ≥ 0.8), as well as their concurrent validity regarding the SST (r ≥ 0.7). Mainly strong relationships (r > 0.50) with the maximum performance tests also suggested moderate-to-high external validity of ACMC variables. Finally, the same variables were also able to distinguish among the participants of different training and physical activity history (p < 0.05). Taken together, these data suggest that ACMC could have the properties of reliability, external validity, and sensitivity similar to SST. However, since ACMC still retains some important advantages over SST (e.g., being based on a brief and fatigue free procedure for testing two antagonistic muscles, and exposing the muscle and joint tissues to relatively low and transient forces), one could conclude that ACMC performed at the self-selected frequency could be developed into a test of muscle function that could be either alternative or complementary to the SST.

This surveillance system should be regularly implemented throughout Europe, providing comparable data on rates of overweight/obesity in primary schools that might drive prudent actions to reverse the pandemic trend of childhood obesity.

The effect of body size on the output of the tests of directly assessed muscle power has been mainly ignored in the applied research. We hypothesized that the muscle power output would reveal a positive relationship with body size closely in line with the theoretical predictions, as well as that the strength of the studied relationship could justify standardized normalization procedures applied in routine testing. Male physical education students (n = 111) were evaluated in 10 standard tests of direct assessment of muscle power output. A standard allometric relationship P = A SB was applied to assess the relationship between the tested power output P and selected indices of body size S ( B = allometric exponent; A = parameter). The correlation coefficients obtained between the tested power output and body size ranged within 0.21 - 0.56 for body mass and 0.10 - 0.49 for body height. The mean (SD) values of the allometric exponents B obtained with respect to body mass and body height were 0.55 (0.15) and 1.15 (0.62), respectively. This relationship proved to be strong enough to merit applying a standard normalization. The normalization method should be based on body mass as a preferred index of body size, while the allometric exponent could correspond to the theoretically predicted one (i.e., B = 0.67).

A novel loading method was applied to explore selective effects of externally added weight (W), weight and inertia (W+I), and inertia (I) on maximum counter-movement jumps (CMJ) performed with arm swing. Externally applied extended rubber bands and/or loaded vest added W, W+I, and I corresponding to 10–40% of subjects' body mass. As expected, an increase in magnitude of all types of load was associated with an increase in ground reaction forces (GRF), as well as with a decrease in both the jumping performance and power output. However, of more importance could be that discernible differences among the effects of W, W+I, and I were recorded despite a relatively narrow loading range. In particular, an increase in W was associated with the minimal changes in movement kinematic pattern and smallest reduction of jumping performance, while also allowing for the highest power output. Conversely, W+I was associated with the highest ground reaction forces. Finally, the lowest maxima of GRF and power were associated with I. Although further research is apparently needed, the obtained finding could be of potential importance not only for understanding fundamental properties of the neuromuscular system, but also for optimization of loading in standard athletic training and rehabilitation procedures.