scholarly journals Operating length and velocity of human M. vastus lateralis fascicles during vertical jumping

2017 ◽  
Vol 4 (5) ◽  
pp. 170185 ◽  
Author(s):  
Maria Elissavet Nikolaidou ◽  
Robert Marzilger ◽  
Sebastian Bohm ◽  
Falk Mersmann ◽  
Adamantios Arampatzis
Keyword(s):  
Velocity Potential ◽  
Vastus Lateralis ◽  
Power Production ◽  
Velocity Curve ◽  
Mechanical Power ◽  
Jump Height ◽  
Velocity Relationship ◽  
Force Velocity ◽  
The Mean ◽  
Force Potential

Humans achieve greater jump height during a counter-movement jump (CMJ) than in a squat jump (SJ). However, the crucial difference is the mean mechanical power output during the propulsion phase, which could be determined by intrinsic neuro-muscular mechanisms for power production. We measured M. vastus lateralis (VL) fascicle length changes and activation patterns and assessed the force–length, force–velocity and power–velocity potentials during the jumps. Compared with the SJ, the VL fascicles operated on a more favourable portion of the force–length curve (7% greater force potential, i.e. fraction of VL maximum force according to the force–length relationship) and more disadvantageous portion of the force–velocity curve (11% lower force potential, i.e. fraction of VL maximum force according to the force–velocity relationship) in the CMJ, indicating a reciprocal effect of force–length and force–velocity potentials for force generation. The higher muscle activation (15%) could therefore explain the moderately greater jump height (5%) in the CMJ. The mean fascicle-shortening velocity in the CMJ was closer to the plateau of the power–velocity curve, which resulted in a greater (15%) power–velocity potential (i.e. fraction of VL maximum power according to the power–velocity relationship). Our findings provide evidence for a cumulative effect of three different mechanisms—i.e. greater force–length potential, greater power–velocity potential and greater muscle activity—for an advantaged power production in the CMJ contributing to the marked difference in mean mechanical power (56%) compared with SJ.

scholarly journals Force-Velocity Relationship in the Countermovement Jump Exercise Assessed by Different Measurement Methods

2019 ◽  
Vol 67 (1) ◽  
pp. 37-47 ◽  
Author(s):  
Amador García-Ramos ◽  
Alejandro Pérez-Castilla ◽  
Antonio J. Morales-Artacho ◽  
Filipa Almeida ◽  
Paulino Padial ◽  
...  
Keyword(s):  
Maximum Velocity ◽  
Measurement Methods ◽  
Loading Conditions ◽  
Countermovement Jump ◽  
Mean Values ◽  
Velocity Transducer ◽  
Jump Exercise ◽  
Velocity Relationship ◽  
Force Velocity ◽  
The Mean

AbstractThis study aimed to compare force, velocity, and power output collected under different loads, as well as the force-velocity (F-V) relationship between three measurement methods. Thirteen male judokas were tested under four loading conditions (20, 40, 60, and 80 kg) in the countermovement jump (CMJ) exercise, while mechanical output data were collected by three measurement methods: the Samozino's method (SAM), a force platform (FP), and a linear velocity transducer (LVT). The variables of the linear F-V relationship (maximum force [F0], maximum velocity [V0], F-V slope, and maximum power [P0]) were determined. The results revealed that (1) the LVT overestimated the mechanical output as compared to the SAM and FP methods, especially under light loading conditions, (2) the SAM provided the lowest magnitude for all mechanical output, (3) the F-V relationships were highly linear either for the SAM (r = 0.99), FP (r = 0.97), and LVT (r = 0.96) methods, (4) the F-V slope obtained by the LVT differed with respect to the other methods due to a larger V0 (5.28 ± 1.48 m·s-1) compared to the SAM (2.98 ± 0.64 m·s-1) and FP (3.06 ± 0.42 m·s-1), and (5) the methods were significantly correlated for F0 and P0, but not for V0 or F-V slope. These results only support the accuracy of the SAM and FP to determine the F-V relationship during the CMJ exercise. The very large correlations of the SAM and LVT methods with respect to the FP (presumed gold-standard) for the mean values of force, velocity and power support their concurrent validity for the assessment of mechanical output under individual loads.

scholarly journals Mechanical model of muscle contraction. 6. Calculations of the tension exerted by a skeletal fiber during a shortening staircase

2019 ◽  
Author(s):  
Louvet S.
Keyword(s):  
Myosin Head ◽  
Myosin Ii ◽  
Velocity Curve ◽  
Shortening Velocity ◽  
Velocity Relationship ◽  
Length Step ◽  
Force Velocity ◽  
Uniform Law ◽  
Slope Line ◽  
Constant Slope

AbstractAccompanying Paper 1 tests a theoretical relationship between force and shortening velocity of a muscle fiber without justifying its validity. Paper 2 determines the kinematics and dynamics of a myosin II head during the working stroke (WS). Paper 3 imposes the Uniform law as a density representative of the orientation of the levers belonging to the WS heads. By support of these works, Papers 4 and 5 put into equation the evolution of the tension during the four phases of a length step. The present paper closes all six articles by imposing two tasks on itself. The first purpose is to apply the theoretical elements developed for a length step to a succession of identical length steps, otherwise known as shortening staircase. With the values of the geometric and temporal parameters assigned to a myosin head in Papers 1 to 5, a correct adjustment is established between the theoretical tension deduced from our model and the experimental tension published in 1997 by a team of Italian researchers relating to nine shortening staircases performed on the same fiber. In particular, we obtain the equation of the tension reached at the time end of the step (T*) which remains constant step by step as soon as the shortening of a half-sarcomere exceeds 17 nm. The second objective is to find and explain the equation of the Force-Velocity curve introduced ex abrupto into Paper 1: by decreasing the size and duration of the steps, the staircase tends towards a constant slope line corresponding to a continuous speed shortening. By applying the methods of infinitesimal calculus to the different formulations leading to T*, we deduce the Force-Velocity relationship (see Supplement S6.L). And the circle is complete.

scholarly journals The Force-Velocity Relationship in Older People: Reliability and Validity of a Systematic Procedure

2017 ◽  
Vol 38 (14) ◽  
pp. 1097-1104 ◽  
Author(s):  
Julian Alcazar ◽  
Carlos Rodriguez-Lopez ◽  
Ignacio Ara ◽  
Ana Alfaro-Acha ◽  
Asier Mañas-Bote ◽  
...  
Keyword(s):  
Older Adults ◽  
Muscle Power ◽  
Reliability And Validity ◽  
Maximal Power ◽  
Mean Values ◽  
Multiple Loads ◽  
Velocity Relationship ◽  
Force Velocity ◽  
The Mean ◽  
Older Men And Women

AbstractThis study compared the reliability and validity of different protocols evaluating the force-velocity (F-V) relationship and muscle power in older adults. Thirty-one older men and women (75.8±4.7 years) underwent two F-V tests by collecting the mean and peak force and velocity data exerted against increasing loads until one repetition maximum (1RM) was achieved in the leg press exercise. Two attempts per load were performed, with a third attempt when F-V points deviated from the linear F-V regression equation. Then, the subjects performed 2×3 repetitions at 60% 1RM to compare purely concentric and eccentric-concentric repetitions. The Short Physical Performance Battery was conducted to assess the validity of the different protocols. Significant differences were found in maximal power (Pmax) between mean and peak values and between protocols differing in the number of attempts per load (p<0.01). Registering mean values, a third attempt, and multiple loads (>3), was significantly more reliable (Pmax: CV=2.6%; ICC=0.99) than the other alternatives. Mean values were also observed to be more associated with physical function than peak values (R2=0.34 and 0.15, respectively; p<0.05). No significant differences were observed between concentric and eccentric-concentric repetitions. Thus, collecting mean force and velocity values against multiple loads, while monitoring the linearity of the F-V relationship, seemed to be the more adequate procedure to assess the F-V profile and muscle power in older adults.

scholarly journals The force–length–velocity potential of the human soleus muscle is related to the energetic cost of running

2019 ◽  
Vol 286 (1917) ◽  
pp. 20192560 ◽  
Author(s):  
Sebastian Bohm ◽  
Falk Mersmann ◽  
Alessandro Santuz ◽  
Adamantios Arampatzis
Keyword(s):  
Soleus Muscle ◽  
Velocity Potential ◽  
Running Economy ◽  
Energetic Cost ◽  
Shortening Velocity ◽  
Optimal Length ◽  
Muscle Belly ◽  
Work Production ◽  
Force Velocity ◽  
Force Potential

According to the force–length–velocity relationships, the muscle force potential is determined by the operating length and velocity, which affects the energetic cost of contraction. During running, the human soleus muscle produces mechanical work through active shortening and provides the majority of propulsion. The trade-off between work production and alterations of the force–length and force–velocity potentials (i.e. fraction of maximum force according to the force–length–velocity curves) might mediate the energetic cost of running. By mapping the operating length and velocity of the soleus fascicles onto the experimentally assessed force–length and force–velocity curves, we investigated the association between the energetic cost and the force–length–velocity potentials during running. The fascicles operated close to optimal length (0.90 ± 0.10 L 0 ) with moderate velocity (0.118 ± 0.039 V max [maximum shortening velocity]) and, thus, with a force–length potential of 0.92 ± 0.07 and a force–velocity potential of 0.63 ± 0.09. The overall force–length–velocity potential was inversely related ( r = −0.52, p = 0.02) to the energetic cost, mainly determined by a reduced shortening velocity. Lower shortening velocity was largely explained ( p < 0.001, R 2 = 0.928) by greater tendon gearing, shorter Achilles tendon lever arm, greater muscle belly gearing and smaller ankle angle velocity. Here, we provide the first experimental evidence that lower shortening velocities of the soleus muscle improve running economy.

scholarly journals Kinematics and Kinetics of Bulgarian-Bag-Overloaded Sprints in Young Athletes

Life ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 282
Author(s):  
Marco Duca ◽  
Athos Trecroci ◽  
Enrico Perri ◽  
Damiano Formenti ◽  
Giampietro Alberti
Keyword(s):  
Peak Power ◽  
Power Production ◽  
Maximal Velocity ◽  
Sprint Training ◽  
Young Athletes ◽  
Production Methods ◽  
Velocity Relationship ◽  
Force Velocity ◽  
Kinetics Of ◽  
Kinematics And Kinetics

Background: Effective sprinting requires large acceleration capabilities. To accelerate, large amount of force must be produced and applied effectively. The use of different implements such as sleds and vests can increase the amount of force produced and alter sprinting effectiveness. We propose the use of increasing overload via the Bulgarian Bag (BB) as a means to modify athletes’ sprint and acutely increase force and power production. Methods: 24 young athletes performed three sprints over 20 m in three different conditions: unloaded (BW) and loaded with BB weighing 2.5% (BB2.5) and 5% (BB5) of the athlete’s body mass. Sprint times at 2.5, 5, 10, 15, and 20 m were acquired and used to compute the force–velocity relationship for the sprints. Maximal velocity (V0), peak force (F0), peak power (PP), and decrease in ratio of force (DRF) were computed. Results: the additional load caused a decrease in sprint times (p < 0.05) and V0 (p = 0.028), conversely no differences were found for F0 (p = 0.21), PP (p = 0.50), and DRF (p = 0.83). Conclusions: Based on those findings, BB can be an alternative method to effectively overload sprint training toward improving sprinting performance.

Optimal shortening velocity (V/Vmax) of skeletal muscle during cyclical contractions: length-force effects and velocity-dependent activation and deactivation.

1998 ◽  
Vol 201 (10) ◽  
pp. 1527-1540 ◽  
Author(s):  
G N Askew ◽  
R L Marsh
Keyword(s):  
Power Output ◽  
Power Production ◽  
Cycle Duration ◽  
Shortening Velocity ◽  
Wide Range ◽  
Velocity Relationship ◽  
Strain Trajectory ◽  
Force Velocity ◽  
Net Power Output ◽  
Force Relationship

The force-velocity relationship has frequently been used to predict the shortening velocity that muscles should use to generate maximal net power output. Such predictions ignore other well-characterized intrinsic properties of the muscle, such as the length-force relationship and the kinetics of activation and deactivation (relaxation). We examined the effects of relative shortening velocity on the maximum net power output (over the entire cycle) of mouse soleus muscle, using sawtooth strain trajectories over a range of cycle frequencies. The strain trajectory was varied such that the proportion of the cycle spent shortening was 25, 50 or 75 % of the total cycle duration. A peak isotonic power output of 167 W kg-1 was obtained at a relative shortening velocity (V/Vmax) of 0.22. Over the range of cyclical contractions studied, the optimal V/Vmax for power production ranged almost fourfold from 0.075 to 0.30, with a maximum net power output of 94 W kg-1. The net power output increased as the proportion of the cycle spent shortening increased. Under conditions where the strain amplitude was high (i.e. low cycle frequencies and strain trajectories where the proportion of time spent shortening was greater than that spent lengthening), the effects of the length-force relationship reduced the optimal V/Vmax below that predicted from the force-velocity curve. At high cycle frequencies and also for strain trajectories with brief shortening periods, higher rates of activation and deactivation with increased strain rate shifted the optimal V/Vmax above that predicted from the force-velocity relationship. Thus, the force-velocity relationship alone does not accurately predict the optimal V/Vmax for maximum power production in muscles that operate over a wide range of conditions (e.g. red muscle of fish). The change in the rates of activation and deactivation with increasing velocity of stretch and shortening, respectively, made it difficult to model force accurately on the basis of the force-velocity and length-force relationships and isometric activation and deactivation kinetics. The discrepancies between the modelled and measured forces were largest at high cycle frequencies.

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