scholarly journals Sprint and Jump Mechanical Profiles in Academy Rugby League Players: Positional Differences and the Associations between Profiles and Sprint Performance

Sports ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 93
Author(s):  
Ben Nicholson ◽  
Alex Dinsdale ◽  
Ben Jones ◽  
Kevin Till
Keyword(s):  
Maximum Velocity ◽  
Mechanical Efficiency ◽  
Rugby League ◽  
Sprint Performance ◽  
Vertical Force ◽  
Horizontal Force ◽  
Cross Sectional ◽  
Performance Variables ◽  
Force Velocity ◽  
And Performance

This cross-sectional study evaluated the sprint and jump mechanical profiles of male academy rugby league players, the differences between positions, and the associations between mechanical profiles and sprint performance. Twenty academy rugby league players performed 40-m sprints and squat jumps at increasing loads (0–80 kg) to determine individual mechanical (force-velocity-power) and performance variables. The mechanical variables (absolute and relative theoretical maximal force-velocity-power, force-velocity linear relationship, and mechanical efficiency) were determined from the mechanical profiles. Forwards had significantly (p < 0.05) greater vertical and horizontal force, momentum but jumped lower (unloaded) and were slower than backs. No athlete presented an optimal jump profile. No associations were found between jump and sprint mechanical variables. Absolute theoretical maximal vertical force significantly (p < 0.05) correlated (r = 0.71–0.77) with sprint momentum. Moderate (r = −0.47) to near-perfect (r = 1.00) significant associations (p < 0.05) were found between sprint mechanical and performance variables. The largest associations shifted from maximum relative horizontal force-power generation and application to maximum velocity capabilities and force application at high velocities as distance increased. The jump and sprint mechanical profiles appear to provide distinctive and highly variable information about academy rugby league players’ sprint and jump capacities. Associations between mechanical variables and sprint performance suggest horizontal and vertical profiles differ and should be trained accordingly.

Mechanical Properties of Sprinting in Elite Rugby Union and Rugby League

2015 ◽  
Vol 10 (6) ◽  
pp. 695-702 ◽  
Author(s):  
Matt R. Cross ◽  
Matt Brughelli ◽  
Scott R. Brown ◽  
Pierre Samozino ◽  
Nicholas D. Gill ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Peak Power ◽  
Rugby League ◽  
Rugby Union ◽  
Sprint Performance ◽  
Maximal Velocity ◽  
Horizontal Force ◽  
Cross Sectional ◽  
The Individual ◽  
Sectional Analysis

Purpose: To compare mechanical properties of overground sprint running in elite rugby union and rugby league athletes. Methods: Thirty elite rugby code (15 rugby union and 15 rugby league) athletes participated in this cross-sectional analysis. Radar was used to measure maximal overground sprint performance over 20 or 30 m (forwards and backs, respectively). In addition to time at 2, 5, 10, 20, and 30 m, velocity-time signals were analyzed to derive external horizontal force–velocity relationships with a recently validated method. From this relationship, the maximal theoretical velocity, external relative and absolute horizontal force, horizontal power, and optimal horizontal force for peak power production were determined. Results: While differences in maximal velocity were unclear between codes, rugby union backs produced moderately faster split times, with the most substantial differences occurring at 2 and 5 m (ES 0.95 and 0.86, respectively). In addition, rugby union backs produced moderately larger relative horizontal force, optimal force, and peak power capabilities than rugby league backs (ES 0.73−0.77). Rugby union forwards had a higher absolute force (ES 0.77) despite having ~12% more body weight than rugby league forwards. Conclusions: In this elite sample, rugby union athletes typically displayed greater short-distance sprint performance, which may be linked to an ability to generate high levels of horizontal force and power. The acceleration characteristics presented in this study could be a result of the individual movement and positional demands of each code.

Effects of postnatal maturation on energetics and cross-bridge properties in rat diaphragm

2002 ◽  
Vol 92 (3) ◽  
pp. 1074-1082 ◽  
Author(s):  
Gilles Orliaguet ◽  
Olivier Langeron ◽  
Belaid Bouhemad ◽  
Pierre Coriat ◽  
Yves LeCarpentier ◽  
...  
Keyword(s):  
Mechanical Efficiency ◽  
Total Force ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Muscle Energetics ◽  
Postnatal Maturation ◽  
Cross Bridge ◽  
Velocity Relationship ◽  
Force Velocity

The effects of maturation on cross-bridge (CB) properties were studied in rat diaphragm strips obtained at postnatal days 3, 10, and 17 and in adults (10–12 wk old). Calculations of muscle energetics and characteristics of CBs were determined from standard Huxley equations. Maturation did not change the curvature of the force-velocity relationship or the peak of mechanical efficiency. There was a significant increase in the total number of CBs per cross-sectional area (m) with aging but not in single CB force. The turnover rate of myosin ATPase increased, the duration of the CB cycle decreased, and the velocity of CBs decreased significantly only after the first week postpartum. There was a linear relationship between maximum total force and m ( r = 0.969, P < 0.001), and between maximum unloaded shortening velocity and m ( r = 0.728, P < 0.001). When this study in the rat and previous study in the hamster are compared, it appears that there are few species differences in the postnatal maturation process of the diaphragm.

scholarly journals Effects of Rest Position on Morphology of the Vastus Lateralis and Its Relationship with Lower-Body Strength and Power

2019 ◽  
Vol 4 (3) ◽  
pp. 64 ◽  
Author(s):  
Alyssa N. Varanoske ◽  
Nicholas A. Coker ◽  
Bri-Ana D.I. Johnson ◽  
Tal Belity ◽  
Gerald T. Mangine ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Morphological Characteristics ◽  
Muscle Thickness ◽  
Lower Body ◽  
Echo Intensity ◽  
Cross Sectional ◽  
Performance Variables ◽  
Body Strength ◽  
And Performance ◽  
Subcutaneous Adipose

Ultrasonography of the lower body typically encompasses supine rest due to fluid shifts affecting tissue size and composition. However, vastus lateralis (VL) examination is completed in the lateral recumbent position, and this positional change may influence morphology and its ability to predict function. This study aimed to examine the effect of position on VL morphology and its relationship with lower-body performance. Cross-sectional area (CSA), muscle thickness (MT), pennation angle (PA), echo intensity (UnCorEI), subcutaneous adipose tissue thickness (SFT), and echo intensity corrected for SFT (CorEI) were assessed in 31 resistance-trained males (23.0 ± 2.1 yrs; 1.79 ± 0.08 m; 87.4 ± 11.7 kg) immediately after transitioning from standing to supine (IP), after 15 min of standing (ST), and after 15 min of rest in three recumbent positions: supine (SUP), dominant lateral recumbent (DLR), non-dominant lateral recumbent (NDLR). Participants also completed unilateral vertical jumps, isometric/isokinetic tests, and a one-repetition maximum leg press. CSA, MT, PA, and SFT were greater in ST compared to NDLR, DLR, and SUP (p < 0.05). CSA, UnCorEI, and CorEI were different between recumbent positions; however no differences were observed for MT, PA, and SFT. Different magnitudes of relationships were observed between muscle morphological characteristics measured after rest in different positions and performance variables. Muscle morphology in IP generally appears to be the best predictor of performance for most variables, although utilizing the NDLR and DLR positions may provide comparable results, whereas morphology measured in ST and SUP provide weaker relationships with physical performance. IP also requires less time and fewer requirements on the technician and subject, thus researchers should consider this positioning for VL examination.

scholarly journals Decisive Factors for a Greater Performance in the Change of Direction and Its Angulation in Male Basketball Players

2020 ◽  
Vol 17 (18) ◽  
pp. 6598
Author(s):  
Francisco J. Barrera-Domínguez ◽  
Bartolomé J. Almagro ◽  
Inmaculada Tornero-Quiñones ◽  
Jesús Sáez-Padilla ◽  
Ángela Sierra-Robles ◽  
...  
Keyword(s):  
Total Sample ◽  
Sport Performance ◽  
Vertical Force ◽  
Basketball Players ◽  
Functional Movement ◽  
Performance Variables ◽  
Change Of Direction ◽  
Force Velocity ◽  
The Relationship ◽  
Age Category

A study was made to initially evaluate whether the age category directly could influence anthropometric measurements, functional movement tests, linear sprint (30 m) and strength. Moreover, and as the main purpose, this study aimed to examine the relationship between the time execution and angles in different changes of direction (COD) test with the analyzed sport performance variables. A total sample of 23 basketball players (age: 17.5 ± 2.42 years; height: 184.6 ± 6.68 cm; body weight: 78.09 ± 11.9 kg). Between-groups’ comparison explored the differences between basketball categories (Junior, n = 12; Senior, n = 11). The COD variables were divided by the time execution into low responders (LR) and high responders (HR) to establish comparisons between groups related to COD time execution. Pearson’s correlation coefficient was used to establish correlations between different CODs and sport performance variables. The results showed a greater influence of age category upon COD performance, especially when the cutting angle was sharper (7.05% [Confidence limits (CL) 90%: 2.33; 11.99]; Quantitative chances (QC) 0/2/98), in which athletes need greater application of strength. Moreover, the sharper the angle or the larger the number of cuts made, the greater the relationship with the vertical force–velocity profile (−42.39 [CL 90%: −57.37; −22.16]; QC 100/0/0%). Thus, the usefulness of the f–v profile to implement training programs that optimize the f–v imbalance and the improvement of the COD performance in basketball players is suggested.

scholarly journals Comparison of two measurement devices for obtaining horizontal force-velocity profile variables during sprint running

2022 ◽  
pp. 174795412110672
Author(s):  
Erin Feser ◽  
Kyle Lindley ◽  
Kenneth Clark ◽  
Neil Bezodis ◽  
Christian Korfist ◽  
...  
Keyword(s):  
Random Error ◽  
Maximum Velocity ◽  
American Football ◽  
Systematic Bias ◽  
Maximal Velocity ◽  
Horizontal Force ◽  
Time Data ◽  
Measured Velocity ◽  
Theoretical Maximum ◽  
Force Velocity

This study established the magnitude of systematic bias and random error of horizontal force-velocity (F-v) profile variables obtained from a 1080 Sprint compared to that obtained from a Stalker ATS II radar device. Twenty high-school athletes from an American football training group completed a 30 m sprint while the two devices simultaneously measured velocity-time data. The velocity-time data were modelled by an exponential equation fitting process and then used to calculate individual F-v profiles and related variables (theoretical maximum velocity, theoretical maximum horizontal force, slope of the linear F-v profile, peak power, time constant tau, and horizontal maximal velocity). The devices were compared by determining the systematic bias and the 95% limits of agreement (random error) for all variables, both of which were expressed as percentages of the mean radar value. All bias values were within 6.32%, with the 1080 Sprint reporting higher values for tau, horizontal maximal velocity, and theoretical maximum velocity. Random error was lowest for velocity-based variables but exceeded 7% for all others, with slope of the F-v profile being greatest at ±12.3%. These results provide practitioners with the information necessary to determine if the agreement between the devices and the magnitude of random error is acceptable within the context of their specific application.

Effects of microtubules and microfilaments on [Ca2+]i and contractility in a reconstituted fibroblast fiber

2000 ◽  
Vol 279 (3) ◽  
pp. C785-C796 ◽  
Author(s):  
Kazuo Obara ◽  
Koji Nobe ◽  
Hiromi Nobe ◽  
Michael S. Kolodney ◽  
Primal De Lanerolle ◽  
...  
Keyword(s):  
Isometric Force ◽  
Calf Serum ◽  
Maximum Velocity ◽  
Mechanical Resistance ◽  
Cross Sectional ◽  
3T3 Fibroblasts ◽  
Primary Determinant ◽  
Intracellular Ca ◽  
Force Velocity ◽  
Contraction And Relaxation

We used a reconstituted fiber formed when 3T3 fibroblasts are grown in collagen to characterize nonmuscle contractility and Ca2+ signaling. Calf serum (CS) and thrombin elicited reversible contractures repeatable for >8 h. CS elicited dose-dependent increases in isometric force; 30% produced the largest forces of 106 ± 12 μN ( n = 30), which is estimated to be 0.5 mN/mm2 cell cross-sectional area. Half times for contraction and relaxation were 4.7 ± 0.3 and 3.1 ± 0.3 min at 37°C. With imposition of constant shortening velocities, force declined with time, yielding time-dependent force-velocity relations. Forces at 5 s fit the hyperbolic Hill equation; maximum velocity ( V max) was 0.035 ± 0.002 Lo/s. Compliance averaged 0.0076 ± 0.0006 Lo/Fo. Disruption of microtubules with nocodazole in a CS-contracted fiber had no net effects on force, V max, or stiffness; force increased in 8, but decreased in 13, fibers. Nocodazole did not affect baseline intracellular Ca2+ concentration ([Ca2+]i) but reduced (∼30%) the [Ca2+]i response to CS. The force after nocodazole treatment was the primary determinant of stiffness and V max, suggesting that microtubules were not a major component of fiber internal mechanical resistance. Cytochalasin D had major inhibitory effects on all contractile parameters measured but little effect on [Ca2+]i.

Mechanical, energetic, and biochemical changes in long-term pressure overload of rabbit heart

1990 ◽  
Vol 259 (3) ◽  
pp. H849-H859 ◽  
Author(s):  
C. L. Gibbs ◽  
I. R. Wendt ◽  
G. Kotsanas ◽  
I. R. Young ◽  
G. Woolley
Keyword(s):  
Stimulus Frequency ◽  
Pressure Overload ◽  
Maximum Velocity ◽  
Peak Stress ◽  
Mechanical Efficiency ◽  
Energy Output ◽  
Papillary Muscles ◽  
Work Output ◽  
Cross Sectional

The mechanical and energetic consequences of long-term pressure-overload (POL) hypertrophy have been investigated in rabbits and compared with sham-operated controls (SOC). Hypertrophy was induced by banding the pulmonary artery of young rabbits and examining the mechanical, biochemical, and energetic properties of the compensated heart 10-16 wk later. Experiments were undertaken on papillary muscles from the hypertrophic hearts. At 27 degrees C and a stimulus frequency of 1 Hz there was a modest depression of peak stress development but no significant changes in isometric rise times and one-half widths or in isotonic maximum velocity of shortening and power output. The inverse relationship between peak stress and cross-sectional area (CSA) was practically identical in the POL and SOC groups. Both polarographic and myothermic investigations were made on papillary muscles. Hypertrophy nearly halved basal metabolism, and in isometric contractions there was increased isometric economy due to a combination of a lower stress cost and a reduced activation heat. Hypertrophy did significantly depress the extent of shortening leading to a reduced work output per beat. In isotonic contractions the reduced work output was offset by a reduced energy output such that there was no significant change in suprabasal mechanical efficiency. Biochemical studies showed that the transition of myosin isoenzymes to the V3 form was essentially complete in the POL group, but that the SOC group was also predominantly V3 when the animals were killed. There was a significant 30% decline in the Ca2(+)-stimulated adenosinetriphosphatase activity of the sarcoplasmic reticulum. It is concluded that in long-term compensated hypertrophy of rabbit hearts there are only a few mechanical and energetic differences between control and hypertrophic muscles. The changes that can be detected appear to predominantly reflect disturbances in cellular Ca2+ regulation.

scholarly journals Relationships between Resisted Sprint Performance and Different Strength and Power Measures in Rugby Players

Sports ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 34
Author(s):  
Santiago Zabaloy ◽  
Jorge Carlos-Vivas ◽  
Tomás T. Freitas ◽  
Fernando Pareja-Blanco ◽  
Lucas Pereira ◽  
...  
Keyword(s):  
Maximum Velocity ◽  
Sprint Performance ◽  
Individual Response ◽  
Sprint Training ◽  
Performance Variables ◽  
Back Squat ◽  
The Individual ◽  
The Relationship ◽  
Rugby Players ◽  
Joint Assessment

This study aimed to investigate the relationship between a specific isometric-strength sprint test (SIST) and unresisted maximum velocity (Vmax), sprint times across different loading conditions, and the velocity loss (Vloss) loads required to achieve each intended Vloss condition during resisted sprint training (RST) in rugby players. Additionally, the investigation examined the relationship between strength in the back-squat one-repetition maximum (1RM-SQ) as well as isometric squat (ISQT), jumps, and sprint performance variables. Twenty (n = 20) male amateur rugby players performed, on two separate occasions, a structural multiple-joint assessment of jumps, strength, and sprint performance. Interestingly, SIST revealed moderate correlations (r = 0.453 to 0.681; p < 0.05) between 1RM-SQ and ISQT. The SISTrel (relative to body mass), but not SIST, used in the present study showed moderate correlations (r = 0.508 to 0.675; p < 0.05) with the loads needed to reach 10%, 30%, and 50% of Vloss during RST. The SISTrel that measures resultant force application in a more sprint-related position explains much of the individual response of each athlete during sprinting towing a sled and can also be used to prescribe and quantify loads in the RST in a more objective and individual manner.

Association Between the Force–Velocity Profile and Performance Variables Obtained in Jumping and Sprinting in Elite Female Soccer Players

2019 ◽  
Vol 14 (2) ◽  
pp. 209-215 ◽  
Author(s):  
Ramón Marcote-Pequeño ◽  
Amador García-Ramos ◽  
Víctor Cuadrado-Peñafiel ◽  
Jorge M. González-Hernández ◽  
Miguel Ángel Gómez ◽  
...  
Keyword(s):  
Velocity Profile ◽  
Soccer Players ◽  
Performance Variables ◽  
Force Velocity ◽  
And Performance

Fore-Aft Forces in Tire-Wheel Assemblies Generated by Unbalances and the Influence of Balancing

1991 ◽  
Vol 19 (3) ◽  
pp. 142-162 ◽  
Author(s):  
D. S. Stutts ◽  
W. Soedel ◽  
S. K. Jha
Keyword(s):  
Mathematical Model ◽  
Elastic Foundation ◽  
Torsional Oscillation ◽  
Vertical Direction ◽  
Torsional Stiffness ◽  
Rolling Motion ◽  
Vertical Force ◽  
Horizontal Force ◽  
Wheel Rim ◽  
Open Question

Abstract When measuring bearing forces of the tire-wheel assembly during drum tests, it was found that beyond certain speeds, the horizontal force variations or so-called fore-aft forces were larger than the force variations in the vertical direction. The explanation of this phenomenon is still somewhat an open question. One of the hypothetical models argues in favor of torsional oscillations caused by a changing rolling radius. But it appears that there is a simpler answer. In this paper, a mathematical model of a tire consisting of a rigid tread ring connected to a freely rotating wheel or hub through an elastic foundation which has radial and torsional stiffness was developed. This model shows that an unbalanced mass on the tread ring will cause an oscillatory rolling motion of the tread ring on the drum which is superimposed on the nominal rolling. This will indeed result in larger fore-aft than vertical force variations beyond certain speeds, which are a function of run-out. The rolling motion is in a certain sense a torsional oscillation, but postulation of a changing rolling radius is not necessary for its creation. The model also shows the limitation on balancing the tire-wheel assembly at the wheel rim if the unbalance occurs at the tread band.

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