Power output in vertical jumps: does optimum loading depend on activity profiles?

The previously proposed maximum dynamic output hypothesis (MDO: i.e. the optimum load for maximizing the power output during jumping is one's own body) was tested on individuals of various activity profiles. Forty males (10 strength-trained athletes, 10 speed-trained athletes, 10 physically active non-athletes, and 10 sedentary individuals) performed different vertical jumps on a force plate while a pulley system was used to either reduce or increase the subject's body weight by 10-30 %. As expected, an increase in external loading resulted in a significant increase (p < 0.001) in force output and a concomitant decrease of peak jumping velocity in all groups of participants. The main finding, however, was that all groups revealed the maximum peak and mean power output at approximately the subjects' own body weight although their weight represented prominently different percentage of their maximum dynamic strength. While a significant (p < 0.05), albeit moderate, 'group × load' interaction in one jump was observed for the peak power output, the individual optimum load for maximizing the power output number did not differ among the groups. Although apparently further research on various types of movements is needed, the present results provide, so far, the strongest support of the MDO hypothesis.

Evaluation of alternating consecutive maximum contractions as an alternative test of neuromuscular function.

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.

Anthropometric and physical performance profiles of elite karate kumite and kata competitors.

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.

Evaluation of the field tests of flexibility of the lower extremity: reliability and the concurrent and factorial validity.

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.