Effect of Different Types of Loads on the Force-Velocity Relationship Obtained During the Bench Press Throw Exercise.

ABSTRACT: Cosic, M, Knezevic, OM, Nedeljkovic, A, Djuric, S, Zivkovic, MZ, and Garcia-Ramos, A. Effect of different types of loads on the force-velocity relationship obtained during the bench press throw exercise. J Strength Cond Res 35(9): 2401-2406, 2021-This study aimed (a) to evaluate the degree of linearity of the force-velocity (F-V) relationship across different types of loads, (b) to compare the magnitude of the F-V relationship parameters (maximum values of force [F0], velocity [V0], and power [Pmax]) between the different types of loads, and (c) to explore the concurrent validity of F0 with traditional measures of maximal strength. The F-V relationships of 15 physically active men (age: 20.9 ± 2.0 years, bench press 1 repetition maximum relative to body mass: 1.20 ± 0.10 kg·kg-1) were determined during the bench press throw exercise using predominantly gravitational (W), inertial (I), and combined (W + I) loads. The bench press maximal isometric force (Fiso) and the 1RM were also assessed. The individual F-V relationships were highly linear regardless of the type of load considered (median r [range] = 0.98 [0.94, 1.00]). The W + I load provided the largest value of F0 (972 ± 45 N; 6.0 and 14.6% higher than W and I, respectively), the I load the largest value of V0 (2.99 ± 0.34 m·s-1; 40.4 and 20.1% higher than W and W + I, respectively), and the W load the lowest value of Pmax (501 ± 46 W; -22.7 and -17.1% lower than I and W + I, respectively). The F0 obtained from the W load presented the highest association with Fiso and 1RM values (r > 0.90). The W + I load and the I load should be recommended to work closer to the F0 and V0 capacities, respectively. However, the W load should be recommended to assess maximal strength capacity through the value of F0.

Is Test Standardization Important when Arm and Leg Muscle Mechanical Properties are Assessed through the Force-Velocity Relationship?

The force-velocity (F-V) relationship observed in multi-joint tasks proved to be strong and approximately linear. Recent studies showed that mechanical properties of muscles: force (F), velocity (V) and power (P) could be assessed through the F-V relationship although the testing methods have not been standardized. The aim of the present study was to evaluate and compare F-V relationships assessed from two tests performed on a modified Smith machine that standardizes kinematics of the movement pattern. Fifteen participants were tested on the maximum performance bench press throws and squat jumps performed against a variety of different loads. In addition, their strength properties were assessed through maximum isometric force (Fiso) and one repetition maximum (1 RM). The observed individual F-V relationships were exceptionally strong and approximately linear (r = 0.98 for bench press throws; r = 0.99 for squat jumps). F-V relationship parameter depicting maximum force (F0) revealed high correlations with both Fiso and 1 RM indicating high concurrent validity (p < 0.01). However, the generalizability of F-V relationship parameters depicting maximum force (F0), velocity (V0) and power (P0) of the tested muscle groups was inconsistent and on average low (i.e. F0; r = -0.24) to moderate (i.e. V0 and P0; r = 0.54 and r = 0.64, respectively; both p < 0.05). We concluded that the F-V relationship could be used for the assessment of arm and leg muscle mechanical properties when standard tests are applied, since the typical outcome is an exceptionally strong and linear F-V relationship, as well as high concurrent validity of its parameters. However, muscle mechanical properties could be only partially generalized across different tests and muscles.

Health-related physical fitness levels and prevalence of obesity in Serbian elementary schoolchildren / Niveles de condición física relacionados con la salud y prevalencia de obesidad en estudiantes de escuela primaria de Serbia

Objectives: the aims of the study were to provide gender- and age-specific physical fitness levels among Serbian schoolchildren and to identify prevalence of overweight and obesity. Methods: a sample of 6,188 boys and 6,023 girls aged nine to 14 years were assessed using the physical fitness battery established through the National Fitness Project of Serbia. Physical fitness levels were determined for body height, body weight and body mass index and for six physical fitness tests (sit and reach, 4 x 10 m shuttle run, standing long jump, 30 sec sit-ups, bent arm hang, 20-m shuttle run). Centile smoothed curves for the 5rd, 25th, 50th, 75th and 95th percentiles were calculated using Cole’s LMS method. Prevalence of overweight and obesity was identified applying cut-off points for children (International Obesity Task Force). Results: the results revealed that anthropometric measures were higher in boys than in girls. In addition, boys had better physical fitness levels for all tests except for the sit and reach test, where girls performed slightly better. The overall prevalence of overweight and obesity amounts to 24.8% (19.8% overweight and 5% obese). With respect to gender, the prevalence of overweight and obesity was higher in boys (27%) compared to girls (22.4%). Conclusion: the presented data are the most up-to-date gender- and age-specific physical fitness levels for Serbian schoolchildren aged 9-14 years. The findings regarding prevalence in overweight and obesity indicated an alarming trend when compared to similar data from other similar studies (in European countries)

Objetivos: los objetivos del estudio fueron evaluar los niveles de condición física diferenciados por sexo y edad de estudiantes de escuela primaria de Serbia e identificar la prevalencia de sobrepeso y obesidad. Método: una muestra de 6.188 niños y 6.023 niñas de entre nueve y 14 años fueron evaluados mediante una batería de test físicos establecidos por el Proyecto Nacional de Condición Física de Serbia. Se evaluó la condición física mediante la altura, el peso, el índice de masa corporal y seis test físicos. Se calcularon curvas suavizadas para los percentiles 5, 25, 50, 75 y 95 usando el método de Cole. La prevalencia de sobrepeso y obesidad fue identificada aplicando los puntos de corte para niños (International Obesity Task Force). Resultados: los resultados revelaron medidas antropométricas mayores en niños que en niñas. Además, los niños tuvieron mejores niveles de condición física en todos los test, con la única excepción del sit and reach, que las niñas realizaron ligeramente mejor. La prevalencia de sobrepeso y obesidad fue del 24,8% (19,8% sobrepeso y 5% obesidad). Respecto al género, la prevalencia de sobrepeso y obesidad fue superior en los niños (27%) en comparación con las niñas (22,4%). Conclusión: los datos presentados son los más actualizados respecto a los niveles de condición física específicos para el género y la edad de niños estudiantes de Serbia de entre nueve y 14 años. Los hallazgos respecto a la prevalencia de sobrepeso y obesidad indican una tendencia alarmante frente a datos similares de otros estudios equivalentes (en países europeos)

Health-related physical fitness levels and prevalence of obesity in Serbian elementary schoolchildren.

INTRODUCTION: Objectives: the aims of the study were to provide gender- and age-specific physical fitness levels among Serbian schoolchildren and to identify prevalence of overweight and obesity. Methods: a sample of 6,188 boys and 6,023 girls aged nine to 14 years were assessed using the physical fitness battery established through the National Fitness Project of Serbia. Physical fitness levels were determined for body height, body weight and body mass index and for six physical fitness tests (sit and reach, 4 x 10 m shuttle run, standing long jump, 30 sec sit-ups, bent arm hang, 20-m shuttle run). Centile smoothed curves for the 5rd, 25th, 50th, 75th and 95th percentiles were calculated using Cole's LMS method. Prevalence of overweight and obesity was identified applying cut-off points for children (International Obesity Task Force). Results: the results revealed that anthropometric measures were higher in boys than in girls. In addition, boys had better physical fitness levels for all tests except for the sit and reach test, where girls performed slightly better. The overall prevalence of overweight and obesity amounts to 24.8% (19.8% overweight and 5% obese). With respect to gender, the prevalence of overweight and obesity was higher in boys (27%) compared to girls (22.4%). Conclusion: the presented data are the most up-to-date gender- and age-specific physical fitness levels for Serbian schoolchildren aged 9-14 years. The findings regarding prevalence in overweight and obesity indicated an alarming trend when compared to similar data from other similar studies (in European countries).

INTRODUCCIÓN: Objetivos: los objetivos del estudio fueron evaluar los niveles de condición física diferenciados por sexo y edad de estudiantes de escuela primaria de Serbia e identificar la prevalencia de sobrepeso y obesidad. Método: una muestra de 6.188 niños y 6.023 niñas de entre nueve y 14 años fueron evaluados mediante una batería de test físicos establecidos por el Proyecto Nacional de Condición Física de Serbia. Se evaluó la condición física mediante la altura,el peso, el índice de masa corporal y seis test físicos. Se calcularon curvas suavizadas para los percentiles 5, 25, 50, 75 y 95 usando el método de Cole. La prevalencia de sobrepeso y obesidad fue identificada aplicando los puntos de corte para niños (International Obesity Task Force). Resultados: los resultados revelaron medidas antropométricas mayores en niños que en niñas. Además, los niños tuvieron mejores niveles de condición física en todos los test, con la única excepción del sit and reach, que las niñas realizaron ligeramente mejor. La prevalencia de sobrepeso y obesidad fue del 24,8% (19,8% sobrepeso y 5% obesidad). Respecto al género, la prevalencia de sobrepeso y obesidad fue superior en los niños (27%) en comparación con las niñas (22,4%). Conclusión: los datos presentados son los más actualizados respecto a los niveles de condición física específicos para el género y la edad de niños estudiantes de Serbia de entre nueve y 14 años. Los hallazgos respecto a la prevalencia de sobrepeso y obesidad indican una tendencia alarmante frente a datos similares de otros estudios equivalentes (en países europeos).

Genomics-Based Insights Into the Biosynthesis and Unusually High Accumulation of Free Fatty Acids by Streptomyces sp. NP10.

Streptomyces sp. NP10 was previously shown to synthesize large amounts of free fatty acids (FFAs). In this work, we report the first insights into the biosynthesis of these fatty acids (FAs) gained after genome sequencing and identification of the genes involved. Analysis of the Streptomyces sp. NP10 draft genome revealed that it is closely related to several strains of Streptomyces griseus. Comparative analyses of secondary metabolite biosynthetic gene clusters, as well as those presumably involved in FA biosynthesis, allowed identification of an unusual cluster C12-2, which could be identified in only one other S. griseus-related streptomycete. To prove the involvement of identified cluster in FFA biosynthesis, one of its three ketosynthase genes was insertionally inactivated to generate mutant strain mNP10. Accumulation of FFAs in mNP10 was almost completely abolished, reaching less than 0.01% compared to the wild-type strain. Cloning and transfer of the C12-2 cluster to the mNP10 mutant partially restored FFA production, albeit to a low level. The discovery of this rare FFA biosynthesis cluster opens possibilities for detailed characterization of the roles of individual genes and their products in the biosynthesis of FFAs in NP10.

Muscle Force-Velocity Relationships Observed in Four Different Functional Tests.

The aims of the present study were to investigate the shape and strength of the force-velocity relationships observed in different functional movement tests and explore the parameters depicting force, velocity and power producing capacities of the tested muscles. Twelve subjects were tested on maximum performance in vertical jumps, cycling, bench press throws, and bench pulls performed against different loads. Thereafter, both the averaged and maximum force and velocity variables recorded from individual trials were used for force-velocity relationship modeling. The observed individual force-velocity relationships were exceptionally strong (median correlation coefficients ranged from r = 0.930 to r = 0.995) and approximately linear independently of the test and variable type. Most of the relationship parameters observed from the averaged and maximum force and velocity variable types were strongly related in all tests (r = 0.789-0.991), except for those in vertical jumps (r = 0.485-0.930). However, the generalizability of the force-velocity relationship parameters depicting maximum force, velocity and power of the tested muscles across different tests was inconsistent and on average moderate. We concluded that the linear force-velocity relationship model based on either maximum or averaged force-velocity data could provide the outcomes depicting force, velocity and power generating capacity of the tested muscles, although such outcomes can only be partially generalized across different muscles.

A simple method for assessment of muscle force, velocity, and power producing capacities from functional movement tasks.

A range of force (F) and velocity (V) data obtained from functional movement tasks (e.g., running, jumping, throwing, lifting, cycling) performed under variety of external loads have typically revealed strong and approximately linear F-V relationships. The regression model parameters reveal the maximum F (F-intercept), V (V-intercept), and power (P) producing capacities of the tested muscles. The aim of the present study was to evaluate the level of agreement between the routinely used "multiple-load model" and a simple "two-load model" based on direct assessment of the F-V relationship from only 2 external loads applied. Twelve participants were tested on the maximum performance vertical jumps, cycling, bench press throws, and bench pull performed against a variety of different loads. All 4 tested tasks revealed both exceptionally strong relationships between the parameters of the 2 models (median R = 0.98) and a lack of meaningful differences between their magnitudes (fixed bias below 3.4%). Therefore, addition of another load to the standard tests of various functional tasks typically conducted under a single set of mechanical conditions could allow for the assessment of the muscle mechanical properties such as the muscle F, V, and P producing capacities.

Structural diversity and possible functional roles of free fatty acids of the novel soil isolate Streptomyces sp. NP10.

Herein, a novel soil bacterium Streptomyces sp. NP10 able to grow outside usual streptomycetes optimum conditions (e.g., at 4 °C, pH 9 and high NaCl concentration), exhibiting atypical hemolytic, DNAse, and cellulolytic activities, is described. This strain produces and excretes into the growth medium large amounts of free long-chain fatty acids (FAs). A concurrent lipidomics study revealed a large structural diversity of FAs with over 50 different n- and branched-chain, (un)saturated, and cyclopropane FAs (C7-C30) produced by this strain. Two of these, i-17:0cy9-10 and a-18:0cy9-10, represent new natural products and the first ever identified branched cyclopropane FAs. Both free and bound lipid profiles of Streptomyces sp. NP10 were dominated by saturated branched chain FAs (i-14:0, a-15:0, and i-16:0). Although these free FAs showed only a moderate antimicrobial activity, our results suggest that they could have an ecophysiological role in interspecies signaling with another soil microorganism Pseudomonas aeruginosa. This work represents the first comprehensive report on the structural diversity and complexity of the free FA pool in Streptomyces. A naturally occurring streptomycete, such as Streptomyces sp. NP10, which secretes significant amounts of free long-chain FAs (non-cytotoxic) into the medium, could be useful in microbial biodiesel production.