Effects of changes in segmental values and timing of both torque and torque reversal in simulated throws.

An overarm throw in the sagittal plane was simulated using a three-segment model representing the upper arm, forearm and hand plus ball. Torque inputs at each joint were turned on at systematically varied times and maintained constant once initiated. All simulations began from identical initial conditions. The aim was to determine the sequence of onset of joint torques which gave the maximal range which the ball would travel and the maximal velocity of the ball irrespective of direction. Best throws proved to be sequential in that joint torques were turned on in a proximal to distal (P-D) temporal sequence. The P-D sequence was also demonstrated by time of peak joint angular velocities. The P-D sequence also proved to be best when segmental constants and joint torques were changed. As this sequence is a common feature of skilled throwing and striking, it is concluded that the linked segmental nature of the limb, irrespective of normal muscle characteristics, primarily predisposes the system to the use of a P-D sequence. The algebraic sign of the shoulder and elbow torques was reversed instantaneously to represent the use of antagonistic muscles. This led to increased output if performed late in the throw and in a P-D sequence. It is concluded that the use of antagonism leads to beneficial redistributions of angular velocity amongst limb segments.     

A comparison of kinematics between overarm throwing with 20% underweight, regular, and 20% overweight balls

The aim of this study was to compare the kinematics in throwing with a regular weighted handball with 20% lighter and heavier balls in female experienced handball players. In total, eight joint movements during the throw were analyzed. The analysis consisted of maximal angles, angles at ball release, and maximal angular velocities of the joint movements and their timings during the throw. Results on 24 experienced female team handball players (mean age 18.2 ± 2.1 years) showed that the difference in ball weight affected the maximal ball velocity. The difference in ball release velocity was probably a result of the significant differences in kinematics of the major contributors to overarm throwing: elbow extension and internal rotation of the shoulder. These were altered when changing the ball weight, which resulted in differences in ball release velocity.     

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.     

Maturation of hamster epididymal sperm motility and influence of the thiol status of hamster and rat spermatozoa on their motility patterns

A method for objective quantification of hamster sperm movement parameters as an indicator of maturation along the epididymis was established using a computerised system. Analysis of spermatozoa released into medium from five epididymal regions showed that the most drastic increases in percentage motility and curvilinear velocity (VCL) occurred from the distal corpus to the beginning of the proximal cauda and in straight-line velocity (VSL) from the beginning to a more distal site within the proximal cauda region. Both high osmolarity (400 mOsm/kg) and the thiol-oxidising agent diamide (10 μM) increased flagellar straightness of distal corpus spermatozoa, but VSL was increased only with the latter. The thiol-reducing agent dithiothreitol (DTT, 1mM) stimulated and maintained percentage motility and velocities of spermatozoa from the caput, stimulated only percentage motility of distal corpus sperm, but decreased velocities of those from the proximal cauda in prolonged incubation. In rats, diamide increased path straightness but not velocities of caput spermatozoa and yet caused immotility within 15 min, whereas DTT prolonged the maintenance of in vitro motility. The slight increases in kinematic parameters in the presence of DTT were enhanced by a 2-min preincubation with diamide. The finding that the effects of DTT and diamide were not compensatory suggests that the influence of the SH/S-S status on sperm movement is multifaceted, with decreasing sensitivity to stimulation upon sperm maturation. © 1994 Wiley-Liss, Inc.     

Axonal transports of tripeptidyl peptidase II in rat sciatic nerves

Axonal transport of tripeptidyl peptidase II, a putative cholecystokinin inactivating serine peptidase, was examined in the proximal, middle, and distal segments of rat sciatic nerves using a double ligation technique. Enzyme activity significantly increased not only in the proximal segment but also in the distal segment 12-72h after ligation, and the maximal enzyme activity was found in the proximal and distal segments at 72h. Western blot analysis of tripeptidyl peptidase II showed that its immunoreactivities in the proximal and distal segments were 3.1- and 1.7-fold higher than that in the middle segment. The immunohistochemical analysis of the segments also showed an increase in immunoreactive tripeptidyl peptidase II level in the proximal and distal segments in comparison with that in the middle segment, indicating that tripeptidyl peptidase II is transported by anterograde and retrograde axonal flow. The results suggest that tripeptidyl peptidase II may be involved in the metabolism of neuropeptides in nerve terminals or synaptic clefts.     

Experimental determination of velocity profiles and wall shear rate along the rabbit aortoiliac bifurcation: relationship to vessel wall low-density lipoprotein (LDL) metabolism.

We have determined the velocity profiles and wall shear rates along the New Zealand White (NZW) rabbit aortoiliac bifurcation. A pulsatile perfusion apparatus was used to impose physiologic pressure and flow waveforms on nine freshly excised NZW bifurcation segments. Pulsed Doppler velocimetry (PDV) was utilized to construct velocity profiles at five measurement sites: within the infrarenal aorta; immediately distal to the apex of the bifurcation; and, more distally along the iliac arteries. Wall shear rate was derived from a numerical differentiation of the experimental velocity profiles. The results of this study indicate that the average shear rate was lower along the lateral (approximately 40 s-1) vs medial (approximately 240 s-1) wall of the proximal iliac branch. The degree of flow reversal along the proximal lateral walls (20 +/- 2%) exceeded that along the proximal flow divider wall (1 +/- 1%). Flow at the distal iliac measurement sites and within the infrarenal aorta was approximately symmetric. These findings complement our companion in vivo study [Berceli et al., Arteriosclerosis 10, 688-694 (1990)] wherein we determined the rates of low-density lipoprotein (LDL) incorporation and catabolism along this symmetrically bifurcating conduit. Taken together, these studies provide original information regarding the effects of hemodynamics on one presumed atherogenic risk factor, namely, LDL metabolism.     

Dependence of Subjective Traverse Length on Velocity of Moving Tactile Stimuli

Two series of experiments were performed to assess the effects of stimulus velocity on human subjects' perception of the distance traversed by a moving tactile stimulus. In all experiments, constant-velocity stimuli were applied to the dorsal surface of the left forearm; velocities ranging between 1.0 and 256 cm/sec were used. In some experiments the stimuli moved from distal to proximal over the skin, and in others they moved from proximal to distal. The length of skin contacted by the moving stimulus was defined by a plate having an aperture of 4.0 × 0.5 cm.

In the first series of experiments, subjects were required to compare the distance traversed by a test stimulus delivered 2 sec after a standard stimulus, and also to report the on-locus and the off-locus of the brushing stimulus. In the second series of experiments, the subjects rated the perceived distance on the skin using a free-magnitude-estimation procedure. The data from both series of experiments defined the same relationship between stimulus velocity and perceived stimulus distance. More specifically, although the length of skin contacted by the stimulus was the same at all velocities, subjects' estimates of stimulus distance decreased with increasing stimulus velocity. In addition, the function relating estimates of stimulus distance to velocity was flat for velocities between 5 and 20 cm/sec, but possessed an appreciable negative slope at lower and higher velocities.

It is interesting that the plateau of the relationship between perceived stimulus distance and velocity occurred within the range of velocities that human subjects employ to scan textured surfaces; it also corresponded precisely with the range of stimulus velocities at which the directional sensitivity of somatosensory cortical neurons and human subjects is optimal.     

Relationship of biomechanical factors to baseball pitching velocity: within pitcher variation

To reach the level of elite, most baseball pitchers need to consistently produce high ball velocity but avoid high joint loads at the shoulder and elbow that may lead to injury. This study examined the relationship between fastball velocity and variations in throwing mechanics within 19 baseball pitchers who were analyzed via 3-D high-speed motion analysis. Inclusion in the study required each one to demonstrate a variation in velocity of at least 1.8 m/s (range 1.8-3.5 m/s) during 6 to 10 fastball pitch trials. Three mixed model analyses were performed to assess the independent effects of 7 kinetic, 11 temporal, and 12 kinematic parameters on pitched ball velocity. Results indicated that elbow flexion torque, shoulder proximal force, and elbow proximal force were the only three kinetic parameters significantly associated with increased ball velocity. Two temporal parameters (increased time to max shoulder horizontal adduction and decreased time to max shoulder internal rotation) and three kinematic parameters (decreased shoulder horizontal adduction at foot contact, decreased shoulder abduction during acceleration, and increased trunk tilt forward at release) were significantly related to increased ball velocity. These results point to variations in an individual's throwing mechanics that relate to pitched ball velocity, and also suggest that pitchers should focus on consistent mechanics to produce consistently high fastball velocities. In addition, pitchers should strengthen shoulder and elbow musculature that resist distraction as well as improve trunk strength and flexibility to maximize pitching velocity and help prevent injury.     

Acquisition of the lateral inconsistency in involuntary behaviour of upper limbs in 12-year-old children during walking at moderate speed.

The aim of this work was to investigate possible lateralisation in the behaviour of periodic motion of the human upper limb, during normal walking at a comfortable speed of locomotion. Ten healthy pre-adolescent, strongly right-handed, 12-year-old males participated in the experiment. Participants were walking on a treadmill with a standardised velocity of 1.1m/s (comfortable speed for all of them). A video analysis system with Silicon software was used to synchronically measure various angles of arms and forearms. The initial, final and interim angular positions of both arms and forearms in 10 cycles of each participant were compared in terms of variations (cycle to cycle) between both upper extremities at corresponding phases of each cycle for distal and proximal segments, respectively. We compared the coefficients of variation in relation to the spatial and temporal data of both limbs and their angular velocities. In addition we investigated the level of cycle-to-cycle regularity (constancy) of behaviour in relation to various positions, periods and velocities of movement of upper extremities (specifically arms and forearms) using the Eta non-linear method of correlation. All participants exhibited a lower level of regularity for the distal segments. The spatial and temporal variations in the dominant limb were also greater than the non-dominant limb for all participants. This may be due to a larger contribution from the right-sided muscles that are considered to be the main contributing factor to the motion of the dominant upper limb during walking, rather than simply gravity force acting alone. A possible practical application of this information may be useful in the objective clinical identification of the level of dominance of the upper extremity (arm plus forearm), in addition to 'traditional' handedness.     

Mechanical energy and power flow analysis of wheelchair use with different camber settings

It has been suggested that minimisation of energy cost is one of the primary determinants of wheelchair designs. Wheel camber is one important parameter related to wheelchair design and its angle may affect usability during manual propulsion. However, there is little available literature addressing the effect of wheel camber on the mechanical energy or power flow involved in manual wheelchair propulsion. Twelve normal subjects (mean age, 22.3 years; SD, 1.6 years) participated in this study. A video-tracking system and an instrumented wheel were used to collect 3D kinematic and kinetic data. Wheel camber of 0° and 15° was chosen to examine the difference between mechanical power and power flow of the upper extremity during manual wheelchair propulsion. The work calculated from power flow and the discrepancy between the mechanical work and power flow work of upper extremity had significantly greater values with increased camber. The upper arm had a larger active muscle power compared with that in the forearm and hand segments. While propelling the increased camber, the magnitude of both the proximal and distal joint power and proximal muscle power was increased in all three segments. While the propelling wheel with camber not only needs a greater energy cost but also there is greater energy loss.     

Comparison of steady and pulsatile flow in a double branching arterial model

Data are presented to compare fluid flow parameters for steady flow with those for time-varying flow in a simplified two branch model which simulates the region of the abdominal aorta near the celiac and superior mesenteric branches of the dog. Measurements in the model included laser doppler anemometry velocity profiles during steady flow, sinusoidal flow with a superimposed mean flow (referred to as simple oscillatory flow) and arterial pulsatile flow. Shear rate measurements were made by an electrochemical technique during steady flow. Flow visualization studies were done during steady and pulsatile flow. Fluid flow effects in the simplified model during steady flow showed many similarities to the results from previous steady flow studies in a canine aortic cast. Shear rates in the region of the proximal (first, or celiac) branch were independent of flow rates in the distal (second, or mesenteric) branch, but the shear pattern within the proximal branch changed significantly as flow in the proximal branch increased. Shear rates on the proximal flow divider (leading edge into the distal branch) depended primarily on the flow rate to the proximal branch, but not on flow to the distal branch. At certain daughter branch flow ratios (approximately 2:1, proximal to distal), flow separation was promoted at the outer wall of the second branch, but flow separation did not occur in the first branch. In contrast to the canine aortic case results, flow separation was never detected on the distal (mesenteric) flow divider of the simplified model. This observation reflects the subtle effects of geometry on flow since the mesenteric flow divider in the canine cast protrudes into the main flow whereas the distal flow divider in the simplified model does not. There were distinct differences in the flow phenomena between steady, simple oscillatory and arterial pulsatile flow. Peak shear rates during pulsatile flow were as much as 10--100 times greater than steady flow shear rates at comparable mean flow rates. Particularly noteworthy for the pulsatile flow with a Womersley parameter of sixteen were very blunt velocity profiles throughout systole, and the absence of flow separation or reversal in those regions of the model that exhibited flow separation during steady flow. The shape of the waveform influences the nature of the flow during time-varying flows. Future studies of fluid dynamics in model systems must consider the pulsatile nature of the flow if a true interpretation of arterial flow phenomena is to be made.     

Anterograde axonal transport of endopeptidase 24.15 in rat sciatic nerves

Axonal transport of endopeptidase 24.15 (EP24.15), a putative neuropeptide degrading-enzyme, was examined in the proximal, middle, and distal segments of rat sciatic nerves using a double ligation technique. At 48h after ligation, a significant amount of the axonal transport of EP24.15 activity was found in the proximal segment, while axonal transport of deamidase activity, a lysosomal enzyme, increased in both proximal and distal segments. Western blot analysis of EP24.15 showed that EP24.15 immunoreactivity in the proximal segment was 1.8-fold higher than that in the middle segment. The immunohistochemical analysis of the segments also showed an increase in the immunoreactive EP24.15 in the proximal segment in comparison with that in the middle segment. In the distal segment, no axonal transport of EP24.15 was found in all methods examined, indicating that EP24.15 is mainly transported by an anterograde axonal flow. These observations suggest that EP24.15 may be involved in the metabolism of neuropeptides in nerve terminals or synaptic clefts.     

Hoffmann's reflex evoked on the soleus muscle and motor neural conduction velocity of the tibial nerve]

H reflex on the soleus muscle and motor tibial nerve conduction velocity are used to study peripheral nervous system maturation in 68 healthy children, from birth to 4 years of age. Proximal an distal conduction velocities develop in a parallel and approximately exponential way but proximal conduction velocities remain always faster. The latencies slightly decrease during the first 18 months of life and then increase very slowly.     

Resealing of the proximal and distal cut ends of transected axons: Electrophysiological and ultrastructural analysis

The fates of the proximal and distal segments of transected axons differ. Whereas the proximal segment usually recovers from injury and regenerates, the distal segment degenerates. In the present report we studied the kinetics of the recovery processes of both proximal and distal axonal segment following axotomy and its temporal relations to the alterations in the cytoarchitecture of the injured neuron. The experiments were performed on primary cultured metacerebral neurons (MCn) isolated from Aplysia. We transected axons while monitoring the changes in transmembrane potential and input resistance (Rn) by inserting intracellular microelectrodes into the soma and axon. Correlation between the electrophysiological status of the injured axon and its ultrastructure was provided by rapid fixation of the neuron at selected times postaxotomy. Axotomy leads to membrane depolarization from a mean of ?55.7 S.D. 12.8 mV to ?12.7 S.D. 3.3 mV and decreased Rn from tens of MΩ to 1–3 MΩ. The transected axons remained depolarized for a period of 10–260 s for as long as the axoplasm was in direct contact with the bathing solution. Rapid repolarization and partial recovery of Rn was associated with the formation of a membrane seal over the cut ends by the constriction and subsequent fusion of the axolema. Prior to the formation of a membraneous barrier, electron-dense deposits aggregate at the tip of the cut axon and appear to form an axoplasmic “plug.” Electrophysiological analysis revealed that this “plug” does not provide resistance for current flow and that the axoplasmic resistance is homogenously distributed. The kinetics of injury and recovery processes as well as the ultrastructural changes of the proximal and distal segments are cannot be attributed to differences in the immediated response of the segments to axotomy. © 1993 John Wiley & Sons, Inc.     

Ischemic injury to enteric free flaps: an experimental study in the dog

Enteric free flaps have proven to be useful for reconstructing the cervical esophagus. Although jejunum is favored, the rationale for this is not at all clear. We have postulated that resistance to warm ischemia varies in different regions of the gut. An experiment was carried out in 10 mongrel dogs in which 10-cm segments of proximal, middle, and distal small bowel were isolated on single vascular pedicles. In each portion of the gut there were three segments: a control, a segment subjected to 60 minutes of warm ischemia, and a segment subjected to 120 minutes of warm ischemia. The following day each animal was reexplored, and the viability of bowel segments was assessed visually and with fluorescein. All control segments were viable at 24 hours. Twenty segments were subjected to 1 hour of warm ischemia, and all but two were viable. Nineteen gut segments were subjected to 2 hours of warm ischemia. Seven of eight proximal segments were viable, two of five midsegments were viable, and zero of six distal segments were viable. Survival in the distal portion compared to the proximal portion was significantly less (p less than 0.01). It appears from this study that isolated distal small bowel segments are less resistant to warm ischemia than proximal segments.     

Postsystolic shortening of ischemic myocardium: a mechanism of abnormal intraventricular filling

Acute myocardial ischemia has been associated with abnormal filling patterns in the left ventricular (LV) apex. We hypothesized that this may in part be due to postsystolic shortening of ischemic apical segments, which leads to reversal of early diastolic apical flow. Fourteen open-chest anesthetized dogs were instrumented with micromanometers in the LV apex and left atrium and myocardial sonomicrometers in the anterior apical LV wall. Intraventricular filling by color Doppler and wall motion by strain Doppler echocardiography (SDE) were assessed from an apical view. Measurements were taken before and after 5 min of left anterior descending coronary artery (LAD) occlusion. In four dogs, we measured the pressure difference between the LV apex and outflow tract. At baseline, peak early diastolic flow velocities in the distal one-third of the LV were directed toward apex (9.2 +/- 1.6 cm/s). After LAD occlusion, the velocities reversed (-2.3 +/- 0.4 cm/s, P < 0.01), indicating that blood was ejected from the apex toward the base during early filling. This interpretation was confirmed by wall motion analysis, which showed postsystolic shortening of apical myocardial segments. The postsystolic shortening represented 9.7 +/- 1.7% (P < 0.01) and 14.2 +/- 2.4% (P < 0.01) of end-diastolic segment length by SDE and sonomicrometry, respectively. Consistent with the velocity changes, we found reversal of the early diastolic pressure gradient from the LV apex to outflow tract. In the present model, acute LAD occlusion resulted in reversal of early diastolic apical flow, and this was attributed to postsystolic shortening of dyskinetic apical segments. The clinical diagnostic importance of this finding remains to be determined.     

The linear cable theory as a model of gill blood flow

The vascular organization of the teleost gill suggests that blood flow distribution from the filamental artery to the respiratory lamellae is governed by relationships analogous to the cable conduction properties of a nerve axon. The space constant (λ) by definition is the distance along the gill filament at which the in-series resistance of the afferent filament artery equals the in-parallel resistance of the afferent lamellar arteriolar, lamellar, efferent lamellar arteriolar (ALA-L-ELA) segments. Constriction of the afferent filamental artery or uniform dilation of the ALA-L-ELA will decrease λ. As λ decreases, flow through the proximal (basal) lamellae greatly increases at the expense of distal lamellar perfusion. When λ increases in a system of finite length the flow profile must account for reflected pressures within the main vessel. The λ calculated from corrosion casts of gill vasculature is $\text{1}\text{4}$ to $\text{1}\text{2}$ the filament length. This favors blood flow through the proximal lamellae and when cardiac output increases, the proportion of cardiac output perfusing the proximal areas increases at the expense of distal lamellar blood flow. To offset these changes it is proposed that increased distal lamellar perfusion is achieved by simultaneous vasodilatation of distal and constriction of proximal ALA-L-ELA segments and dilation of the afferent filamental artery.     

Effect of torso rotational strength on angular hip, angular shoulder, and linear bat velocities of high school baseball players

This investigation examined the effect of torso rotational strength on angular hip (AHV), angular shoulder (ASV), linear bat-end (BEV), and hand velocities (HV) and 3 repetition maximum (RM) torso rotational and sequential hip-torso-arm rotational strength (medicine ball hitter's throw) in high school baseball players (age 15.4 +/- 1.2 y). Participants were randomly assigned to 1 of 2 training groups. Group 1 (n = 24) and group 2 (n = 25) both performed a stepwise periodized resistance exercise program and took 100 swings a day, 3 days a week, for 12 weeks with their normal game bat. Group 2 performed additional rotational and full-body medicine ball exercises 3 days a week for 12 weeks. A 3RM parallel squat and bench press were measured at 0 and after 4, 8, and 12 weeks. Participants were pre- and posttested for 3RM dominant and nondominant torso rotational strength and medicine ball hitter's throw. Angular hip velocities, ASV, BEV, and HV were recorded pre- and posttraining by a motion capture system that identified and digitally processed reflective markers attached to each participant's bat and body. Groups 1 and 2 increased (p < or = 0.05) BEV (3.6 and 6.4%), HV (2.6 and 3.6%), 3RM dominant (10.5 and 17.1%) and nondominant (10.2 and 18.3%) torso rotational strength, and medicine ball hitter's throw (3.0 and 10.6%) after 12 weeks. Group 2 increased AHV (6.8%) and ASV (8.8%). Group 2 showed greater improvements in BEV, AHV, ASV, 3RM dominant and nondominant torso rotational strength, and medicine ball hitter's throw than group 1. Groups 1 and 2 increased predicted 1RM parallel squat (29.7 and 26.7%) and bench press (17.2 and 16.7%) strength after 12 weeks. These data indicate that performing additional rotational medicine ball exercises 2 days a week for 12 weeks statistically improves baseball performance variables.     

Unsteady and three-dimensional simulation of blood flow in the human aortic arch

A three-dimensional and pulsatile blood flow in a human aortic arch and its three major branches has been studied numerically for a peak Reynolds number of 2500 and a frequency (or Womersley) parameter of 10. The simulation geometry was derived from the three-dimensional reconstruction of a series of two-dimensional slices obtained in vivo using CAT scan imaging on a human aorta. The numerical simulations were obtained using a projection method, and a finite-volume formulation of the Navier-Stokes equations was used on a system of overset grids. Our results demonstrate that the primary flow velocity is skewed towards the inner aortic wall in the ascending aorta, but this skewness shifts to the outer wall in the descending thoracic aorta. Within the arch branches, the flow velocities were skewed to the distal walls with flow reversal along the proximal walls. Extensive secondary flow motion was observed in the aorta, and the structure of these secondary flows was influenced considerably by the presence of the branches. Within the aorta, wall shear stresses were highly dynamic, but were generally high along the outer wall in the vicinity of the branches and low along the inner wall, particularly in the descending thoracic aorta. Within the branches, the shear stresses were considerably higher along the distal walls than along the proximal walls. Wall pressure was low along the inner aortic wall and high around the branches and along the outer wall in the ascending thoracic aorta. Comparison of our numerical results with the localization of early atherosclerotic lesions broadly suggests preferential development of these lesions in regions of extrema (either maxima or minima) in wall shear stress and pressure.     

Absence of 'superfast' axonal transport in rat sciatic nerve.

Axonal transport of labelled protein was studied in rat sciatic nerve by analyzing nerve segments at intervals after injection of L-[3H]leucine into the lumbar spinal cord. Some nerves were sectioned before injection so that material in transit accumulated proximal to the section. The segments distal to the section served as controls for incorporation into the nerve of blood-borne label. An analysis of TCA-soluble and TCA-insoluble activity in cut and intact nerve segments was also made. No evidence was found for the existence of a 'superfast' component of axonal transport (velocity 2000 mm/day). Results showed that the most rapidly transported protein derived from the neuron soma had a conventional 'fast' velocity of 350-420 mm/day. There was no transport of TCA-soluble material. It is suggested that 'superfast' transport, detected in mice by other investigators, is an artefact resulting from failure to control for incorporation of circulating label into the sciatic nerve.