Theoretical Maximal Velocity Research Articles

Mechanical determinants of acceleration and maximal sprinting speed in highly trained young soccer players

The aim of the present study was to examine, in highly trained young soccer players, the mechanical horizontal determinants of acceleration (Acc) and maximal sprinting speed (MSS). Eighty-six players (14.1 ± 2.4 year) performed a 40-m sprint to assess Acc and MSS. Speed was measured with a 100-Hz radar, and theoretical maximal velocity (V0), horizontal force (F0) and horizontal power (Pmax) were calculated. Within each age group, players were classified as high Acc/fast MSS (>2% faster than group mean), medium (between −2% and +2%), and low/slow (>2% slower). Acc and MSS were very largely correlated (−0.79; 90% confidence limit [−0.85; −0.71]). The determinants (multiple regression r2 = 0.84 [0.78; 0.89]) of Acc were V0 (partial r: 0.80 [0.72; 0.86]) and F0 (0.57 [0.44; 0.68]); those of MSS (r2 = 0.96 [0.94; 0.97]) were V0 (0.96 [0.94; 0.97]) and Pmax (0.73 [0.63; −0.80]). High/Med have likely greater F0 (Cohen’s d: +0.8 [0.0; 1.5]), V0 (+0.6 [−0.1; 1.3]) and Pmax (+0.9 [0.2; 1.7]) than Low/Med. High/Fast have an almost certainly faster V0 (+2.1 [1.5; 2.7]) and a likely greater Pmax (+0.6 [−0.1; 1.3]) than High/Med, with no clear differences in F0 (−0.0 [−0.7; 0.6]). Speed may be a generic quality, but the mechanical horizontal determinants of Acc and MSS differ. While maximal speed training may improve both Acc and MSS, improving horizontal force production capability may be efficient to enhance sprinting performance over short distances.

Evaluation of fatigue in semi-professional football players: association between overtraining and physical fitness

Summary Study aim: overtraining (OT) has a detrimental effect on sport performance, but it is not clear to what extent it influences physical fitness. The aim of this study was to examine the relationship between OT and physical fitness in football players. Material and methods: a sample of semi-professional male football players (n = 124) performed a series of anthropometric and physical fitness measurements, and completed the 54-item OT questionnaire of the French Society of Sports Medicine. Results: the OT score was significantly correlated with sit-and-reach test (SAR; rho = −0.20, p < 0.05), theoretical maximal velocity (v0; rho = −0.23, p < 0.05), theoretical maximal force (F0) of the force-velocity test (F-v test; rho = 0.25, p < 0.01) and mean power (Pmean) in W · kg−1 of the Wingate anaerobic test (WAnT; rho = −0.20, p < 0.05). The comparison between OT quartiles revealed that the first quartile scored higher than the third quartile in SAR and in v0 (p < 0.05). The fourth quartile scored higher in F0 than the first, second and third quartiles (p < 0.05). The magnitude of these differences among groups was medium. Conclusions: the negative correlations between OT and physical fitness and the highest scores in fitness for the first OT quartile indicate a negative effect of OT on physical fitness (anaerobic capacity, maximal velocity and flexibility) of football players. In addition, because there is very limited prior relevant research on football players’ OT, our data can be used as reference for future research.

Progression of Mechanical Properties during On-field Sprint Running after Returning to Sports from a Hamstring Muscle Injury in Soccer Players

The objectives of this study were to examine the consequences of an acute hamstring injury on performance and mechanical properties of sprint-running at the time of returning to sports and after the subsequent ~2 months of regular soccer training after return. 28 semi-professional male soccer players, 14 with a recent history of unilateral hamstring injury and 14 without prior injury, participated in the study. All players performed two 50-m maximal sprints when cleared to return to play (Test 1), and 11 injured players performed the same sprint test about 2 months after returning to play (Test 2). Sprint performance (i. e., speed) was measured via a radar gun and used to derive linear horizontal force-velocity relationships from which the following variables obtained: theoretical maximal velocity (V(0)), horizontal force (F(H0)) and horizontal power (Pmax). Upon returning to sports the injured players were moderately slower compared to the uninjured players. F H0 and Pmax were also substantially lower in the injured players. At Test 2, the injured players showed a very likely increase in F(H0) and Pmax concomitant with improvements in early acceleration performance. Practitioners should consider assessing and training horizontal force production during sprint running after acute hamstring injuries in soccer players before they return to sports.

Theoretical analysis on plane fire plume in a longitudinally ventilated tunnel

This paper presents a theoretical analysis on the longitudinal tunnel ventilation in fire emergency based on a plane fire plume model. The objective of the current research is to understand the physical mechanism leading to the decoupling of critical velocity and HRR in the case of large tunnel fire. The solution of the analysis has established a critical Fr curve that changes continuously from what can be approximated by Thomas’ cubic root correlation to a constant limited by Archimedes’ principle. The turning point between the two ventilation regimes is the unit relative tunnel height to the height of flame. The current analysis has revealed that in order to predict the behaviour of critical velocity correctly, all three controlling factors, namely fire, ventilation and tunnel height must be taken into account. Both traditional ceiling plume theory and Thomas’ correlation are inadequate in analysing tunnel fire ventilation. The former does not include forced ventilation and the later has left tunnel height out. The current Fr curve has provided the theoretical maximum critical velocity that can serve as guidance for fan sizing in tunnel ventilation design. Comparison between the prediction from the current theory and three independent sets of experimental data has shown excellent agreement.

Mechanical determinants of 100-m sprint running performance

Sprint mechanics and field 100-m performances were tested in 13 subjects including 9 non-specialists, 3 French national-level sprinters and a world-class sprinter, to further study the mechanical factors associated with sprint performance. 6-s sprints performed on an instrumented treadmill allowed continuous recording of step kinematics, ground reaction forces (GRF), and belt velocity and computation of mechanical power output and linear force-velocity relationships. An index of the force application technique was computed as the slope of the linear relationship between the decrease in the ratio of horizontal-to-resultant GRF and the increase in velocity. Mechanical power output was positively correlated to mean 100-m speed (P<0.01), as was the theoretical maximal velocity production capability (P<0.011), whereas the theoretical maximal force production capability was not. The ability to apply the resultant force backward during acceleration was positively correlated to 100-m performance (r (s)>0.683; P<0.018), but the magnitude of resultant force was not (P=0.16). Step frequency, contact and swing time were significantly correlated to acceleration and 100-m performance (positively for the former, negatively for the two latter, all P<0.05), whereas aerial time and step length were not (all P>0.21). Last, anthropometric data of body mass index and lower-limb-to-height ratio showed no significant correlation with 100-m performance. We concluded that the main mechanical determinants of 100-m performance were (1) a "velocity-oriented" force-velocity profile, likely explained by (2) a higher ability to apply the resultant GRF vector with a forward orientation over the acceleration, and (3) a higher step frequency resulting from a shorter contact time.

Differences in Force-velocity Characteristics of Upper and Lower Limbs of Non-competitive Male Boxers

Despite the increasing popularity of boxing, only a few studies have been conducted on the physiology or the biomechanics of this sport. The aim of the present study is to examine the ratios of mechanical characteristics (maximal anaerobic power, Pmax, theoretical maximal force, F0, and velocity, v0) between upper and lower limbs of male boxers. Twelve male caucasians, all members of a local fitness club, aged 29.5 (3.2) yr [mean (standard deviation)], stature 1.74 (.05) m, body mass 77.9 (8.1) kg, body fat 22.4 (3.9) % and somatotype 5.5-5.5-1.1, performed a force-velocity (F-v) test for both legs and arms. The F-v test included five supramaximal pedal sprints, each lasting 7 sec, against incremental braking force of 20-60 N for arms and 30-70 N for legs, on modified arm-cranking and on cycle ergometer (Ergomedics 874, Monark, Sweden). The legs had higher Pmax (910 W vs. 445 W, t11=22.9, p&lt;.001), Pmax expressed in relative to body mass values (rPmax, 11.8 W.kg-1 vs. 5.8 W.kg-1, t11=20.6,p&lt;.001), F0 (168 N vs. 102 N, t11=21.7, p&lt;.001), v0 (217 rpm vs. 177 rpm, t11=46.6, p&lt;.001) and lower v0/F0 (1.33 rpm.N-1 vs. 1.82 rpm.N-1, t11=15.3, p&lt;.001) than the arms. Pmax of upper limbs was associated with Pmax of lower limbs (r=.70, p&lt;.05) and their ratio was .49 (.06). The respective values of rPmax was r=.76 (p&lt;.01), F0, r=.35 (p=.26) and .61 (.13), and of velocity, v0,r=.17 (p=.59) and .812 (.10). In spite of moderate associations between upper and lower limbs’ F0 and v0, a stronger relationship was found with regard to Pmax. These findings emphasize the need for separate evaluation of arms’ and legs’ F-v characteristics on a regular basis and the consideration of these measures in training design.

Experimental and field approach to the hydraulics of nature-like pool-type fish migration facilities

Nature-like fish migration facilities have gradually become a common type to ensure longitudinal connectivity of fish movements in running waters. This article presents verification on hydraulic and geometric parameters of nature-like pool-type fish passes via experimental and field investigations. The experiment verified that the maximum streamwise velocity near a slot ranged from 0.8–1.0 time of the theoretical maximum velocity. Large vertical recirculations presented below sills, moved downstream with the increase in discharge, and were likely to vanish or to change the rotation direction with high flow conditions. High turbulent kinetic energy distributed immediately downstream from boulder sills instead of along the water jet. Fieldwork was conducted at a full-width ramp in Kolbermoor and a partial-width ramp in Leitner in Bavaria under low, mean and high flow conditions to investigate the flow and geometry characteristics in real constructions and under various hydrologic conditions. The results for velocity show confidence in the method to obtain the maximum value around a slot by measuring at one depth only. Instead of flow velocity, water depth played a more critical role in the performance of a nature-like fishway, in particular under low flow conditions, and so did the arrangement of boulders along a sill. A detailed hydraulic/geometric investigation, together with biological monitoring, should be conducted to identify appropriate criteria on assessment of fish free passage at nature-like fish migration facilities.

Measurements of colliding shock wave and supersonic gas flow

The collision between a laser generated shock wave and a supersonic flow from a gas jet was studied using pump-probe Schlieren shadowgraphy. The velocity of a gas escaping into vacuum from a high pressure gas jet nozzle was measured and verified in simulation. Time resolved tracking of the shock wave provided critical information about the gas jet vertical velocity and horizontal gas density profile. The measured velocity of the diatomic gas jet was found to be close to the theoretical maximum escape velocity of the gas released into vacuum. Modification of the hemispherical shock wave structure by the supersonic flow was minimal. However, the propagation of the shock wave was observed to be substantially effected by the gas flow.

Determination and validity of critical swimming velocity in elite physically disabled swimmers

Article The purpose of this investigation was to determine if the critical swimming velocity (CSV), defined as the theoretical maximal swimming velocity that could be maintained for a long period of time without exhaustion, corresponds to the exercise intensity at onset blood lactate accumulation (OBLA), and if it could be utilized as a practical index for assessing endurance performance in elite physically disabled swimmers. Eight elite physically disabled swimmers swam four different distances (50, 100, 200 and 400 m) at maximal effort. The swimming time was taken during each trial. The CSV was expressed as the slope of a regression line between the covered swimming distance and the corresponding times of all possible combinations of 2 or 4 time trials. Results indicate that all the CSVs calculated were similar independently of the distances utilized for their calculation. Afterwards, a CSV confirmation test consisting of 3×10-min trials at 95, 100, 105% of the CSV was carried out. The lactate concentration at the end of each trial was 3.32, 4.03 and 5.73 mmol·l−1, respectively. Lactate concentration at 100% CSV approached the value of 4 mmol·l−1, which is considered the exercise intensity at OBLA. We conclude that the CSV corresponds with the OBLA intensity and could be a valuable index to plan a training schedule for physically disabled swimmers.

Experimental study on both ionic wind and resuspension of particles under unequal electrostatic field

Abstract Ionic wind and resuspension of particles under an unequal electrostatic field have been investigated experimentally using a needle electrode and grounded plate where fine particles are deposited. As voltage is applied to the needle electrode, a straight stream is immediately generated around the needle. Then the straight stream induces a new flow around it. When the straight stream impacts on the target, circulated flow is generated and grows gradually with time. Finally, an almost steady jet stream is formed. Ionic current from the needle to the target increases with almost the square of the electrostatic field between the needle and particle layer. If the strength of the electrostatic field is high enough, most of particles are resuspended from the layer immediately after the voltage is applied to the needle. However, if the strength is reduced, some heaps remain on the layer. Resuspension of particles occurred in two stages. The more the initial mass of the layer, the faster the resuspension velocity of particles in the first stage. The velocity increases almost linearly with the electrostatic field. The fact suggests that the velocity in the first stage is related to the theoretical maximum velocity of the ionic wind.

Analysis of the vacuum cannon

We develop a model for the velocity of a projectile in a vacuum cannon. The theoretical maximum velocity is independent of the vacuum cannon diameter and projectile mass and is significantly lower than the speed of sound. Experimental measurements support the theory as an upper limit.

Isokinetic Measurement of Maximal Muscle Power during Leg Cycling: A Comparison of Adolescent Boys and Adult Men

This study investigated the maximal isokinetic muscle power characteristics in adolescent boys and adult men by comparing voluntary maximal efforts on a novel isokinetic cycling ergometer. Thirteen boys and 12 men performed between seven and ten 6-s (unpaced, maximal) sprints at crank velocities ranging from 80–170 rev · min−1 (8.3–17.8 rad · s−1). Maximum power over a single revolution (Pmax) and mean power for the total of complete revolutions in 5 s (MP5s) were recorded, and the optimal crank velocity for both parameters was calculated for each subject. Men’s Pmax were significantly higher (P &lt; .05) than boys. There were no significant differences in the optimal velocity at Pmax and MP5s or the theoretical maximum velocity at Pmax and MP5s for men or boys. All subjects showed a linear torque velocity relationship (r &gt; 0.90) for both Pmax and MP5s. Absolute differences in isokinetic power between adolescent boys and adult men cannot be attributable to the differences in crank pedal velocities as optimal velocities were similar in both groups.

Effects of aerobic exercise on the torque-velocity relationship in cycling

The kinetics of the torque-velocity (T-omega) relationship after aerobic exercise was studied to assess the effect of fatigue on the contractile properties of muscle. A group of 13 subjects exercised until fatigued on a cycle ergometer, at an intensity which corresponded to 60% of their maximal aerobic power for 50 min (MAP60%); ten subjects exercised until fatigued at 80% of their maximal aerobic power for 15 min (MAP80%). Of the subjects 7 exercised at both intensities with at least a 1-week interval between sessions. Pedalling rate was set at 60 rpm. The T-omega relationship was determined from the velocity data collected during all-out sprints against a 19 N.m braking torque on the same ergometer, according to a method proposed previously. Maximal theoretical velocity (omega zero) and maximal theoretical torque (Tzero) were estimated by extrapolation of the linear T-omega relationship. Maximal power (Pmax) was calculated from the values of Tzero and omega zero (Pmax = 0.25 omega zero Tzero). The T-omega relationships were determined before, immediately after and 5 and 10 min after the aerobic exercise. The kinetics of omega zero, Tzero and Pmax was assumed to express the effects of fatigue on the muscle contractile properties (maximal shortening velocity, maximal muscle strength and maximal power). Immediately after exercise at MAP60% a 7.8% decrease in Tzero and 8.8% decrease in Pmax was seen while the decrease in omega zero was nonsignificant, which suggested that Pmax decreased in the main because of a loss in maximal muscle strength. In contrast, MAP80% induced a 8.1% decrease in omega zero and 12.8% decrease in Pmax while the decrease in Tzero was nonsignificant, which suggested that the main cause of the decrease in Pmax was probably a slowing of maximal shortening velocity. The short recovery time of the T-omega relationship suggests that the causes of the decrease of torque and velocity are processes which recover rapidly.

Effect of fatigue on maximal velocity and maximal torque during short exhausting cycling.

A group of 24 subjects performed on a cycle ergometer a fatigue test consisting of four successive all-out sprints against the same braking torque. The subjects were not allowed time to recover between sprints and consequently the test duration was shorter than 30 s. The pedal velocity was recorded every 10 ms from a disc fixed to the flywheel with 360 slots passing in front of a photo-electric cell linked to a microcomputer which processed the data. Taking into account the variation of kinetic energy of the ergometer flywheel, it was possible to determine the linear torque velocity relationship from data obtained during the all-out cycling exercise by computing torque and velocity from zero velocity to peak velocity according to a method proposed previously. The maximal theoretical velocity (v(0)) and the maximal theoretical torque (T(0)) were estimated by extrapolation of each torque-velocity relationship. Maximal power (P(max)) was calculated from the values of T(0) and v(0) (P(max) = 0.25v(0)T(0). The kinetics of v(0), T(0) and P(max) was assumed to express the effects of fatigue on the muscle contractile properties (maximal shortening velocity, maximal muscle strength and maximal power). Fatigue induced a parallel shift to the left of the torque-velocity relationships. The v( 0), T(0) and P(max) decreases were equal to 16.3 percent, 17.3 percent and 31 percent, respectively. The magnitude of the decrease was similar for v(0) and T(0) which suggested that P max decreased because of a slowing of maximal shortening velocity as well as a loss in maximal muscle strength. However, the interpretation of a decrease in cycling v(0) which has the dimension of a maximal cycling frequency is made difficult by the possible interactions between the agonistic and the antagonistic muscles and could also be explained by a slowing of the muscle relaxation rate.

A gas-driven gene gun for microprojectile methods of genetic engineering

A study has been made of a gas-driven gene gun which launches microprojectiles carrying foreign genetic material into living cells. The gene gun consists of a shock tube driver which generates pressure pulses that accelerate a membrane (macroprojectile) fitted across the end of the shock tube. The macroprojectile launches a cloud of high-speed microprojectiles on firing. The performance was studied in terms of the initial macroprojectile geometry and the pressure-time history on its surface. The pressure-time history was altered by varying the length of the shock tube. Direct measurements were made of the macroprojectile velocity and the penetration of microprojectiles into model cell systems. Under conditions of shock acceleration, good agreement was found between measured velocities and those predicted using one-dimensional gas dynamic theory. In terms of the terminal velocity of the macroprojectile, when the macroprojectile was initially planar, best results were obtained with the long shock tube (shock acceleration), but when the macroprojectile was initially domed convex upstream to increase acceleration distance, best results were obtained with the short shock tube (pressure pulse excitation). The difference between the performance of those two configurations was due to interaction of pressure loading mechanics and the structural properties of the macroprojectile as a consequence of its shape. Significant fractions of microprojectiles penetrated at least six cell layers at conditions consistent with a theoretical maximum macroprojectile velocity of 330 m s-1. Transient gene expression was achieved in target wheat suspension cells.

Comment on “Particle simulation of ion heating in the ring current” by S. Qian, M. K. Hudson, and I. Roth

In a recent paper, Qian et al. (1990) investigated an ion cyclotron wave (ICW) instability and heating of thermal ions in a plasma with a loss cone distribution of hot ions. This study is an extension of a simulation study (Omura et al., 1985) of helium heating in an ICW instability driven by anisotropic hot protons with a bi-Maxwellian distribution. The dependence of the ion heating on the thermal H{sup +}/He{sup +} density ratio is studied by simulation runs with better spatial resolution. In the simulations of the ICW instability, a small percentage of the thermal helium ions are accelerated beyond the theoretical maximum velocity. This is because the excited waves are not exactly monochromatic as assumed in the theory, and a stochastic acceleration takes place in the presence of waves with different wave numbers and frequencies. To confirm that the parallel electric field (Qian et al., 1990, equation (10)) is not operative in the process of parallel heating, the author has performed a computer experiment where the parallel electric field is artificially eliminated from the equation of motion in the hybrid code. He assumed the same parameters of the simulation in the work by Omura et al. (1988). Themore » results shows that the dynamics of the thermal helium ions in the acceleration phase is the same and that the time history of the thermal energy of helium ions is almost identical with the results of Omura et al. (1988). The computer experiment evidently demonstrates that the parallel electric field is not responsible for the parallel heating. As a summary, the interaction of the forward and backward traveling waves plays an important and essential role in the process of parallel heating found in the ICW instability driven by a temperature anisotropy.« less

The relationship between the isotonic mechanical power in jaw‐opening and jaw‐closing muscles in man

The relationship between isotonic jaw-opening and jaw-closing muscle function was studied using a newly developed apparatus which enables load and velocity to be detected simultaneously. The following results were obtained from 17 male adults (age range 22-32 years) without any occlusal dysfunction. (i) The force-velocity relationship in jaw-opening and jaw-closing muscles was represented by a hyperbolic curve, which fitted well with Hill's equation. (ii) The theoretical maximum force obtained by extrapolation from regression was 32.55 +/- 4.98 kg for jaw opening and 35.74 +/- 4.52 kg for jaw closing. (iii) The theoretical maximum velocity obtained by extrapolation from regression was 456.70 +/- 183.27 mm s-1 for jaw opening and 372.77 +/- 141.67 mm s-1 for jaw closing. (iv) The maximum mechanical power (Pmax) calculated from the product of the force and velocity was 772.20 +/- 182.65 kg.mm s-1 for jaw opening and 708.68 +/- 128.14 kg.mm s-1 for jaw closing. (v) The Pmax exerted by individual subjects was approximately 12-34% of the maximum possible force (Fmax) calculated from the force and velocity, in both jaw opening and jaw closing. There were no statistically significant differences between jaw opening and jaw closing with regard to any isotonic muscle functions. In other words, the results of this study strongly indicated a substantial balance between isotonic jaw-opening and jaw-closing muscle function in the subjects who were investigated.

Metabolism of endogenous and xenobiotic aldehydes by rainbow trout ( Oncorhynchus mykiss) liver fractions

Aldehyde dehydrogenase (ALDH) specific activity was measured in crude homogenates, post-mitochondrial supernatants, cytosolic and microsomal fractions of trout liver, using a number of endogenous and xenobiotic aldehydes and both NAD + and NADP + as co-factors. All the activity found in the crude homogenate could be accounted for by the sum of the cytosolic and microsomal activities. Highest activities were found with the medium chain length substrates hexanal and nonanal in all fractions. The α,β-unsaturated aldehydes, (E,E)-2,4-nonadienal-1-al, and trans, trans-2,4-decadienal, were also good substrates for both fractions, while the hydroxylated α,β unsaturated trans-4-hydroxy-2-nonenal was a good substrate only for the microsomal fraction. Short chain and aromatic xenobiotic substrates were metabolized at much lower rates, and only the microsomal fraction was effective against acetaldehyde, acrolein, and benzaldehyde. Neither fraction metabolized 2,5-dihydroxy benzaldehyde. NAD + was the preferred co-factor for most substrates. Apparent affinity ( K m) for hexanal and nonanal in the cytosolic fraction were comparable to that found in rats, but the theoretical maximal velocity ( V max) for these substrates, and the specific activities for the other substrates, were much lower than found in mammals. The biochemical results suggest that trout are well adapted to detoxify products of endogenous lipid peroxidation, but are poorly adapted to detoxify xenobiotic aldehydes. In another study with carcinogen-fed fish, ALDH distribution was evaluated histochemically in cryostat sections. In control trout, ALDH was uniformly distributed without an apparent zonal pattern. However, in hepatic tumors, ALDH was apparently induced with hexanal, nonanal, and propionaldehyde giving the strongest reaction products; other substrates also reacted, but with much lower sensitivity.

Potential of Datura innoxia cell suspension cultures for glucosylating hydroquinone

The efficiency of glucosylation of hydroquinone by Datura innoxia cell suspension cultures was investigated. The yield of arbutin was 2.4 g/l medium when 10 mM of hydroquinone was added to a suspension culture that was then incubated for 24 h, but the yield decreased at a higher concentration. This decrease, which could not be overcome by changing the growth phase or increasing the cell density used, could be avoided by the repeated addition of a low concentration of hydroquinone over 3 days. This increased the yield of arbutin to 4.2 g/l at the usual cell density and to 7.1 g/l at a high density. The kinetics of this reaction were explained by the Michaelis-Menten formula. The theoretical maximum velocity of the arbutin-forming reaction was estimated as 0.77 mg/h/g. The velocity increased linearly up to a cell density of 300 g/l under standard aeration, the theoretical maximum yield of arbutin being calculated to be 5.5 g/l/day.

Dynamic considerations of fracture in mortars

The results of two series of experiments on mortars are presented. The results on the first series related to the effect of a disturbance (e.g. on aggregate) on the crack path and the crack velocity. For the second series the effects of the aggregate type on the velocity and the dynamic fracture toughness were analysed. High speed photography was used to measure crack velocities and it was concluded that the velocities observed are well below the theoretical maximum velocity for the materials. The problems of crack branching are also discussed.