Evaluation of novel tests of neuromuscular function based on brief muscle actions.

Although widely used, the standard strength test (SST) is known to provide moderate correlations with functional measures, while being based on sustained maximum forces and a relatively large number of trials. The aim of this study was to compare the concurrent (with respect to SST) and external validity (with respect to the standard balance and maximum power output tests) of 2 alternate tests of neuromuscular function based on brief isometric actions. The first test provides a slope between the rates of torque development (RTD) and peak torques (T) measured from a number of consecutive rapid actions performed across a wide range of T levels (brief force pulses, BFP). The second test (alternating consecutive maximum contractions, ACMC) provides T and RTD from multiple cycles of rapid alternating maximum actions of 2 antagonistic muscle groups. The results obtained from 29 young and healthy subjects revealed moderate-to-high concurrent validity of ACMC (median r = 0.56, p < 0.05) and its similar, if not higher external validity than SST. Conversely, both the concurrent and external validity of BFP seemed to be relatively low (r = 0.23, p > 0.05). Because ACMC could also have advantage over SST by being based on somewhat lower and transitional muscle forces exerted and fewer trials are needed for testing 2 antagonistic muscles, the authors conclude that ACMC could be considered as either an alternative or complementary test to SST for testing the ability for rapid exertion of maximum forces. Conversely, BFP may offer a measure of the neuromuscular system "as a whole" that is complementary to SST by providing outcomes that are relatively independent of muscle size and function.

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.

Evaluation of a composite test of kicking performance.

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.

Trajectories of Body Height, Body Weight, BMI, and Nutrition Status from 1979 to 1987: A Measurement-Based Analysis of 8740 Montenegrin Male Adolescents from the Municipality of Berane.

This study aimed to consolidate the body height, body weight, BMI, and nutrition status data of the overall young male population from the Municipality of Berane in order to assess the trajectories of those variables from 1979 to 1987. The sample of respondents included 8740 adolescents who were divided into nine groups according to their age. The sample of variables included body height, body weight, body mass index, and nutrition status, which were presented based on a long-established BMI categorization (underweight, normal weight, pre-obese, and obese). The descriptive statistics are expressed as the mean and standard deviation for each variable; the analysis of nutrition status was calculated based on BMI, while LSD post hoc testing with ANOVA was employed to investigate differences between the means. The results indicate that a secular trend is visible regarding body height and body weight, while no trend is visible for the BMI and nutrition status. This study's contribution is that it provides insight into more recently published data for the studied period and in this municipality, which can significantly aid in following the secular trend throughout Montenegro.

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.

Evaluation of the torque-angular velocity relationship across various joint positions.

BACKGROUND: Standard neuromuscular assessment through a single value, such as the maximum voluntary torque, could be limited since it changes substantially with movement velocity and joint position and could not discern among force, velocity or power producing capacities of a specific muscle. Therefore, we aimed to evaluate the torque-angular velocity (T-AV) interchange across various joint positions. METHODS: Knee extensors were tested in 40 physically active participants at six velocities between 30° and 180°/s. Both, linear and the second-order polynomial regression methods were applied on peak torque (TMAX) and angle specific torque outputs (between 80° to 20° of knee extension). RESULTS: The obtained results suggest decline of the concentric torque as angular velocity increases (P<0.05). The obtained the T-AV relationship appears to be strong and linear for the most subjects (R2=0.74-0.97) and highly reliable (r>0.80) at least when the positions around the TMAX angle are considered. CONCLUSIONS: The present study revealed that the T-AV relationship of knee extensors, observed from isokinetic tests conducted within a wide range of angular velocities, could be strong, linear and reliable. The results demonstrate that linear regression method could be feasible approach for evaluating individual muscle mechanical capacities.

Effects of loading on maximum vertical jumps: Selective effects of weight and inertia.

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.

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.