Influence of the direction of the cable force and of the radius of the hammer path on speed fluctuations during hammer throwing

Hammer speed increases gradually during a throw, but this general increasing trend has one fluctuation superimposed in each turn. In some throwers, gravity and the forward translation of the system produce most of the fluctuation; in others, a marked fluctuation remains after the effects of gravity and of the forward translation of the system have been subtracted out. The remaining fluctuation could be produced through two mechanisms: (a) pulling on the hammer cable in a direction alternately ahead and behind the position of the centroid of the hammer path and (b) alternately shortening and lengthening the distance between the hammer head and the centroid of its path. Three-dimensional film analysis of eight highly-skilled throwers showed that the portion of the hammer speed fluctuation not due to gravity nor to the forward motion is produced mainly by pulling alternately ahead and behind the position of the centroid of the hammer path.     

A kinematic study of center of mass motions in the hammer throw

Eight highly-skilled hammer throwers were studied using film analysis procedures. The location and velocity of the center of mass (c.m.) of each thrower, hammer and thrower-hammer system were calculated. The vertical component of motion of all three c.m.s followed cyclic patterns with one fluctuation per turn. The fluctuation of the c.m. of the thrower was ahead of that of the hammer by approximately a third of a cycle, and this made the periods of upward vertical acceleration of the system c.m. coincide approximately with the double-support phases. In the horizontal direction, the c.m.s of the thrower and of the hammer followed roughly trochoid patterns as a result of the combination of rotation with forward displacement across the throwing circle. Their rotations were out of synchrony by approximate synchrony with the hammer, or an essentially straight trajectory. The results of this study suggest that the investigation of the hammer throw might be facilitated by the use of a quasi-inertial non-rotating reference frame that follows the general motion of the system c.m. while ignoring its fluctuations within each turn.     

Optimal distance from the implement to the axis of rotation in hammer and discus throws.

It is a well-known fact that a dramatic improvement in the range of any projective throw can be achieved by increasing the release velocity. In this paper a simple model of a competitor with an implement (hammer or discus) in the turns is considered. The thrower is regarded as a rigid body, and the implement as a point mass. The transverse velocity component of the implement at the release moment is maximized. For finding the optimal distance of the implement from the axis of rotation optimal control theory is applied. According to the proposed model, the optimal hammer throwing technique requires constant and maximal distance of the implement from the axis of rotation, followed by the rapid shortening of the distance immediately prior to the release. In the discus throw, however, this shortening is useless.     

Influence of environmental factors on shot put and hammer throw range

On the rotating Earth, in addition to the Newtonian gravitational force, two additional relevant inertial forces are induced, the centrifugal and Coriolis forces. Using computer modelling for typical release heights and optimal release angles, we compare the influence of Earth rotation on the range of the male hammer throw and shot put with that of air resistance, wind, air pressure and temperature, altitude and ground obliquity. Practical correction maps are presented, by which the ranges achieved at different latitudes and/or with different release directions can be corrected by a term involving the effect of Earth rotation. Our main conclusion and suggestion is that the normal variations of certain environmental factors can be substantially larger than the smallest increases in the world records as acknowledged by the International Amateur Athletic Federation and, therefore, perhaps these should be accounted for in a normalization and adjustment of the world records to some reference conditions. Although this suggestion has certainly been made before, the comprehensiveness of our study makes it even more compelling. Our numerical calculations contribute to the comprehensive understanding and tabulation of these effects, which is largely lacking today.     

Elevated plantar pressures in neuropathic diabetic patients with claw/hammer toe deformity

Elevated plantar foot pressures during gait in diabetic patients with neuropathy have been suggested to result, among other factors, from the distal displacement of sub-metatarsal head (MTH) fat-pad cushions caused by to claw/hammer toe deformity. The purpose of this study was to quantitatively assess these associations. Thirteen neuropathic diabetic subjects with claw/hammer toe deformity, and 13 age- and gender-matched neuropathic diabetic controls without deformity, were examined. Dynamic barefoot plantar pressures were measured with an EMED pressure platform. Peak pressure and force-time integral for each of 11 foot regions were calculated. Degree of toe deformity and the ratio of sub-MTH to sub-phalangeal fat-pad thickness (indicating fat-pad displacement) were measured from sagittal plane magnetic resonance images of the foot. Peak pressures at the MTHs were significantly higher in the patients with toe deformity (mean 626 (SD 260)kPa) when compared with controls (mean 363 (SD 115) kPa, P<0.005). MTH peak pressure was significantly correlated with degree of toe deformity (r=-0.74) and with fat-pad displacement (r=-0.71) (P<0.001). The ratio of force-time integral in the toes and the MTHs (toe-loading index) was significantly lower in the group with deformity. These results show that claw/hammer toe deformity is associated with a distal-to-proximal transfer of load in the forefoot and elevated plantar pressures at the MTHs in neuropathic diabetic patients. Distal displacement of the plantar fat pad is suggested to be the underlying mechanism in this association. These conditions increase the risk for plantar ulceration in these patients.     

A three-dimensional analysis of overarm throwing in experienced handball players

The aim of this study was to investigate the contribution of upper extremity, trunk, and lower extremity movements in overarm throwing in team handball. In total, 11 joint movements during the throw were analyzed. The analysis consists of maximal angles, angles at ball release, and maximal angular velocities of the joint movements and their timing during the throw. Only the elbow angle (extension movement range) and the level of internal rotation velocity of the shoulder at ball release showed a significant relationship with the throwing performance. Also, a significant correlation was found for the timing of the maximal pelvis angle with ball velocity, indicating that better throwers started to rotate their pelvis forward earlier during the throw. No other significant correlations were found, indicating that the role of the trunk and lower limb are of minor importance for team handball players.     

Erratum and answer to the comment by Harris on: Numerical treatment of two-center overlap integrals (J Mol Mod, 12,213–220, 2006)

In the present contribution, we present two numerical tables for overlap integrals over Slater type functions and over B functions using the method present in the paper (J Mol Model, 12:213–220, 2006) where there were typos in the data that led Harris to conclude that our method is flawed and not useful for serious work. The typos are corrected and the numerical tables are listed as well as values from the literature and values obtained using ACJU code in order to perform comparisons with regards to accuracy.     

A Late Pleistocene time-series of bottom-current speed in the Vema Channel

A coarsening of the mean particle size of the carbonate-free silt fraction from sea-floor samples below 4000 m in the Vema Channel has been used to separate high-velocity Antarctic Bottom Water (AABW) from the overlying, slower North Atlantic Deep Water (NADW). A time-series of fluctuations in bottom-current speed within the modern AABW/NADW transition zone was examined by determining the particle-size distribution of sediments from eight gravity cores with a high-resolution stratigraphy for the past 250 kyrs. The bottom-current paleospeed was inferred from a correlation of particle size in seafloor samples with mean current speed from nearby current-meters. The mean bottom-current speed at depths comparable to modern AABW was highest (7–10 cm/s) during interglacial to glacial transitions corresponding to the oxygen isotopic stage 6/7 and 4/5 boundaries and at present. The mean bottom-current speed at depths comparable to modern NADW was nearly uniform for most of the past 250 kyrs except during glacial oxygen isotopic stage 2 when the speed dropped to 2 cm/s, or one-half of the present speed. The application of the “calibrated” particle-size method to examine bottom-current paleospeed allows testing of paleoceanographic models which rely on assumptions or inferences of changes in bottom-water production rate during the late Pleistocene paleoclimatic fluctuations.     

The effect of milling parameters on starch hydrolysis of milled malt in the brewing process

The effect of milling parameters on the hydrolysis of starch during the mashing process was investigated. Hammer milling was compared against roll milling. Roll gap settings, roll speed, speed differential were also analysed, as well as comparing four- to six-roll milling. The parameter of differential speed was also studied through grist particle size distribution. Employing a 65 °C infusion type mashing process for the wort, the glucose and maltose concentrations of malts milled in different ways were analysed. Results showed that the glucose concentration in the wort after 45 min of mashing, obtained using a hammer mill, was the same as that achieved from roll milling in 60 min. For roller mill gap settings the 0.8 mm gap grist required 60 min of mashing to reach a glucose concentration of 3.46 g l⁻¹, whereas the 0.1 mm gap grist achieved the same level of starch hydrolysis in almost half the time, around 30–35 min of mashing. The results regarding roll speed showed that the 300 and 700 rpm mashes required roughly 50 and 40 min, respectively. Comparable sugar concentrations in the 50 rpm mash were obtained in 60 min. Finally, the comparison between simulated four- and six-roll milling showed the latter yielded higher glucose concentrations.     

Influence of normative data’s walking speed on the computation of conventional gait indices

The pathology’s impact on gait pattern may be overestimated by conventional gait indices (Gillette Gait Index – GGI, Gait Deviation Index – GDI, Gait Profile Score – GPS), since impairments’ consequences on kinematics may be amplified by a change in walking speed. The objectives of this study were to evaluate the influence of walking speed on the computation of gait indices and to propose a corrective method to cancel the effects of walking speed. Spatiotemporal parameters and kinematics of fifty-four asymptomatic participants (30 M/24 W, 37.9 ± 13.7 years, 72.8 ± 13.3 kg, 1.74 ± 0.10 m) were collected at four speed conditions (C₁:[0,0.4] m s⁻¹, C₂:[0.4,0.8] m s⁻¹, C₃:[0.8,1.2] m s⁻¹, C₄:spontaneous). Four values of each index were computed for each trial using successively the four conditions as normative data repository. Mean values over all participants were statistically compared (paired t-tests, 95% confidence level). Indices values computed with normative at equivalent walking speed were not statistically different from reference values. Meanwhile, deviations appeared when the walking speed discrepancy between conditions and normative increased. These drifts related to walking speed mismatch have been quantified and fitting functions proposed. A correction was applied to indices. GGI was efficiently adjusted while GDI and GPS remain different from their reference values for C₁ and C₂. Gait indices must be interpreted cautiously in function of the normative data repository’s walking speed used for computation. Furthermore, a coupled use of conventional and corrected gait indices could lead to a better comprehension of the contribution of impairments and walking speed on gait deviations and overall gait quality.     

Torque-velocity characteristics and muscle fiber type in human vastus lateralis

The relationship between torque-velocity characteristics of the knee extensors during isokinetic contractions and muscle fiber type of the vastus lateralis, determined from two muscle biopsy samples, was investigated in 12 male and 18 female subjects. Peak torque, corrected for the effect of gravity and impact artifact, was classified as corrected peak torque. The torque measured 30 degrees from full extension and, corrected for gravity, was classified as corrected torque at 30 degrees. No significant correlations were found between the percentage of fast-twitch fibers (%FT) or the relative area of FT fibers (%FTA) and corrected peak torque values for any of the velocities tested or the knee angles where corrected peak torques were measured. However, significant inverse relationships were determined for corrected torque at 30 degrees at all but the fastest velocity (270 degrees/s) and both %FT and %FTA for the male subjects. These results reveal that muscle fiber type of the vastus lateralis, based on duplicate muscle samples, is not related to the peak torque actually generated by the knee extensors but may influence the shape of the torque output for maximal contractions sustained over the entire range of motion.     

Characteristics of postural corrective responses before and after long-term spaceflight

Balance function is dramatically deteriorated after exposure to microgravity. The purpose of the present study was to investigate the role and the contribution of different gravity sensory systems to the development of balance impairment after long-term spaceflights. Postural perturbations (pushes to the chest) of the threshold, medium, and sub-maximal intensities were produced in eight cosmonauts before, and on the day 3, 7, and 11 following spaceflight. Postural corrective responses were analyzed by anterior-posterior body sway fluctuation and electromyographic activity of leg muscles. The characteristics of the postural corrective responses changed significantly on the day 3 following spaceflight: the amplitude of posterior sway caused by perturbation of threshold intensity was increased reaching 135% ofpreflight value; the corrective responses lasted more than 6 s in 50% of all trials, while it did not last more than 4 s in 96% before spaceflight. The EMG responses were characterized by increased contribution of medium- and long-latency reactions. On the day 11 following spaceflight, most of the characteristics of postural corrective responses were close to preflight values. We assumed that the balance alterations after spaceflight are caused by changes in weightlessness of functions of two main gravity sensory systems, namely, weight-bearing and vestibular one. The deficit of weight-bearing afferentation triggers a decline of the extensors' muscle tone, while changes of vestibular function cause a decline of accuracy of postural corrections.     

Characteristics of postural corrective responses before and after long-term spaceflights

Balance function is dramatically deteriorated after exposure to microgravity. The purpose of the present study was to investigate the role and the contribution of different gravity sensory systems to the development of balance impairment after long-term spaceflights. Postural perturbations (pushes to the chest) of the threshold, medium, and sub-maximal intensities were produced in eight cosmonauts before, and on the day 3, 7, and 11 following spaceflight. Postural corrective responses were analyzed by anterior-posterior body sway fluctuation and electromyographic activity of leg muscles. The characteristics of the postural corrective responses changed significantly on the day 3 following spaceflight: the amplitude of posterior sway caused by perturbation of threshold intensity was increased reaching 135% of preflight value; the corrective responses lasted more than 6 s in 50% of all trials, while it did not last more than 4 s in 96% before spaceflight. The EMG responses were characterized by increased contribution of medium- and long-latency reactions. On the day 11 following spaceflight, most of the characteristics of postural corrective responses were close to preflight values. We assumed that the balance alterations after spaceflight are caused by changes in weightlessness of functions of two main gravity sensory systems, namely, weight-bearing and vestibular one. The deficit of weight-bearing afferentation triggers a decline of the extensors’ muscle tone, while changes of vestibular function cause a decline of accuracy of postural corrections.     

Humans control stride-to-stride stepping movements differently for walking and running,independent of speed

As humans walk or run, external (environmental) and internal (physiological) disturbances induce variability. How humans regulate this variability from stride-to-stride can be critical to maintaining balance. One cannot infer what is “controlled” based on analyses of variability alone. Assessing control requires quantifying how deviations are corrected across consecutive movements. Here, we assessed walking and running, each at two speeds. We hypothesized differences in speed would drive changes in variability, while adopting different gaits would drive changes in how people regulated stepping. Ten healthy adults walked/ran on a treadmill under four conditions: walk or run at comfortable speed, and walk or run at their predicted walk-to-run transition speed. Time series of relevant stride parameters were analyzed to quantify variability and stride-to-stride error-correction dynamics within a Goal-Equivalent Manifold (GEM) framework. In all conditions, participants’ stride-to-stride control respected a constant-speed GEM strategy. At each consecutively faster speed, variability tangent to the GEM increased (p ≤ 0.031), while variability perpendicular to the GEM decreased (p ≤ 0.044). There were no differences (p ≥ 0.999) between gaits at the transition speed. Differences in speed determined how stepping variability was structured, independent of gait, confirming our first hypothesis. For running versus walking, measures of GEM-relevant statistical persistence were significantly less (p ≤ 0.004), but showed minimal-to-no speed differences (0.069 ≤ p ≤ 0.718). When running, people corrected deviations both more quickly and more directly, each indicating tighter control. Thus, differences in gait determined how stride-to-stride fluctuations were regulated, independent of speed, confirming our second hypothesis.     

The effects of rigid motions on elastic network model force constants

Elastic network models provide an efficient way to quickly calculate protein global dynamics from experimentally determined structures. The model's single parameter, its force constant, determines the physical extent of equilibrium fluctuations. The values of force constants can be calculated by fitting to experimental data, but the results depend on the type of experimental data used. Here, we investigate the differences between calculated values of force constants and data from NMR and X-ray structures. We find that X-ray B factors carry the signature of rigid-body motions, to the extent that B factors can be almost entirely accounted for by rigid motions alone. When fitting to more refined anisotropic temperature factors, the contributions of rigid motions are significantly reduced, indicating that the large contribution of rigid motions to B factors is a result of over-fitting. No correlation is found between force constants fit to NMR data and those fit to X-ray data, possibly due to the inability of NMR data to accurately capture protein dynamics.     

Mechanics of running under simulated low gravity.

Using a linear mass-spring model of the body and leg (T. A. McMahon and G. C. Cheng. J. Biomech. 23: 65-78, 1990), we present experimental observations of human running under simulated low gravity and an analysis of these experiments. The purpose of the study was to investigate how the spring properties of the leg are adjusted to different levels of gravity. We hypothesized that leg spring stiffness would not change under simulated low-gravity conditions. To simulate low gravity, a nearly constant vertical force was applied to human subjects via a bicycle seat. The force was obtained by stretching long steel springs via a hand-operated winch. Subjects ran on a motorized treadmill that had been modified to include a force platform under the tread. Four subjects ran at one speed (3.0 m/s) under conditions of normal gravity and six simulated fractions of normal gravity from 0.2 to 0.7 G. For comparison, subjects also ran under normal gravity at five speeds from 2.0 to 6.0 m/s. Two basic principles emerged from all comparisons: both the stiffness of the leg, considered as a linear spring, and the vertical excursion of the center of mass during the flight phase did not change with forward speed or gravity. With these results as inputs, the mathematical model is able to account correctly for many of the changes in dynamic parameters that do take place, including the increasing vertical stiffness with speed at normal gravity and the decreasing peak force observed under conditions simulating low gravity.     

Day-to-day and seasonal fluctuations of urban mortality in Kyoto,Japan

The study and interpretation of temporal variability in mortality requires the consideration of both exogenous and endogenous influences as underlying factors. In the present paper the relative contribution of fluctuations in daily weather was investigated using the unbiased techniques of lagged cross-correlation and spectral analyses. The study focused on patterns of daily mortality in Kyoto, Japan. Studied herein were total mortality of all ages less accidental, ischemic heart (IHD), cerebrovascular (CVD), cardiovascular (IHD + CVD), cancer and among elderly (over 70 years of age) deaths. The meteorological factors were mean, maximum and minimum daily temperature, mean barometric pressure, mean relative humidity, and mean and maximum wind speed. It was found that after extreme weather conditions, such as heat waves (with mean air temperature in excess of 30°C) or the intrusion of cold waves (with mean air temperature below 0°C), mortality increased to about three times the daily average with a lag effect of usually one—three days and up to one week. Over the year, however, weather fluctuations were found to account statistically for no more than 10% of the overall annual variability in mortality. Importantly, the short-term upswings in mortality were usually accompanied by noticeable drops in the number of deaths on the subsequent days suggesting a triggering effect of external factors. The most weather-sensitive mortality group was people over 70 years of age.     

Number fluctuation spectroscopy of motile microorganisms.

A random-walk model of motility is used to predict the dynamics of fluctuations in the number of particles in a small observation volume. The results show that number fluctuations provide a measure of the mean swimming speed as well as the persistence length. Experimental light-scattering results are presented for three strains of Escherichia coli whose motion appears random-walk in nature. For the strain with th elongest persistence length, excellent agreement is found that theoretical predictions. For the more erratic strains, however, the shape of the measured scattered light intensity correlation functions indicates the presence of a contribution due to orientational fluctuations.     

Muscle-contraction properties in overarm throwing movements

On the basis of dynamic and kinematic data, this study identifies the type of muscle contraction in unloaded overarm throwing movements. An unloaded throw or nearly unloaded throw is defined as the throw in which the external resistance is too small (e.g., the team handball, baseball, and water polo throws as well as the tennis and badminton smashes). A special arm-force-measuring apparatus was constructed to imitate an overarm throw. Forty-two subjects were placed into 3 groups: untrained subjects, weight-trained athletes, and team handball players. The measured parameters included the velocity of the initial movement, the release velocity, the velocity of the first 50 milliseconds of the concentric phase, the force value at the moment of deceleration of the initial movement, and the impulse values during the eccentric and concentric phases of the test movement. Statistically significant higher values of the above parameters (p < 0.05) were determined in that test at which the initial speed of movement was higher. Also, the correlation coefficients of the parameters of the initial phase of the throw movement were very high (p < 0.001), especially the parameters related with the movement's first 50 milliseconds. The results support the thesis that the stretch-shortening cycle is the type of muscle contraction in unloaded overarm throws. Furthermore, it is possible to increase the throw velocity by increasing the velocity of the initial movement (i.e., by provoking higher inertia forces).     

Declining track and field performance trends in recent years in the Austrian best results 1897-2019

Objectives:Plateauing of world records in sports has been suggested to reflect the limits of human physiology. Possible explanations include reduced doping or declining popularity that may even lead to a decrease in human performance. Such a decrease, however, has not yet been observed. We hypothesized that rather than a performance plateau, performance has recently declined.Methods:Fifteen athletic disciplines of the Austrian annual rankings were analyzed by regression statistics and the average best performance of the last 20 years compared to earlier periods.Results:The best performances occurred between 1980–1999 and were on average 2.56% (men) and 1.67% (women) better than between 2000–2019. This attenuation was significant in men in 200 m, 800 m, 1500 m, 10 km, long jump, javelin throw (p<0.05), high jump, pole vault, discus throw, shot put and hammer throw (p<0.001); and in women in 400 m, long jump, discus throw (p<0.05) and high jump (p<0.001). The greatest performance declines were observed in the men’s shot put (9.11%) and hammer throw (11.44%).Conclusions:The Austrian track and field annual best results show a performance decline following a peak, instead of a plateau. Future studies should address the causes and whether this also applies to other sports and countries.