Grip Height Research Articles

An examination of kinematic parameters related to pole vault performance

ABSTRACT Although various studies have examined factors associated with pole vault performance, only a few have identified a linear relationship between these factors and performance. This study aimed to identify the kinematics variables correlating with the maximum centre of gravity (CG) height. This cross-sectional study included 16 male pole vaulters and recorded their performance using four high-speed cameras at 240 Hz. The vaulters cleared the bungee bars that were set at 90% of their personal best record. The variables during pole vaulting from the touchdown of the penultimate step on the approach to the peak height of the CG were calculated. Pearson’s correlation analysis and Spearman’s rank correlation were used to test the correlation between maximum CG height and the variables. Significant correlations were observed between the maximum CG height and the six variables (grip height, approach velocity, takeoff velocity, takeoff distance, push height, and maximum vertical velocity). Grip height showed the strongest relationship, followed by push height and takeoff velocity. Pole vaulters should aim to gain a high approach velocity and grip height to increase their mechanical energy.

The target as an obstacle: Grasping an object at different heights

Humans use a stereotypical movement pattern to grasp a target object. What is the cause of this stereotypical pattern? One of the possible factors is that the target object is considered an obstacle at positions other than the envisioned goal positions for the digits: while each digit aims for a goal position on the target object, they avoid other positions on the target object even if these positions do not obstruct the movement. According to this hypothesis, the maximum grip aperture will be higher if the risk of colliding with the target object is larger. Based on this hypothesis, we made a set of two unique predictions for grasping a vertically oriented cuboid at its sides at different heights. For cuboids of the same height, the maximum grip aperture will be smaller when grasped higher. For cuboids whose height varies with grip height, the maximum grip aperture will be larger when grasped higher. Both predicted relations were experimentally confirmed. This result supports the idea that considering the target object as an obstacle at positions other than the envisioned goal positions for the digits is underlying the stereotypical movement patterns in grasping. The goal positions of the digits thus influence the maximum grip aperture even if the distance between the goal positions on the target object does not change.

Two-dimensional biomechanical thumb model for pipetting

Manual pipetting imposes repetitive movements, high force, and awkward postures on the thumb, fingers, and wrist, increasing the risk of musculoskeletal injuries. The purpose of this study is to provide a linear regression model to estimate the optimal pipetting grip height based on the two-dimensional biomechanical static thumb model developed in this study. This biomechanical static thumb model uses hand anatomy and static equilibrium conditions to estimate internal tendon forces against a given external force. Based on the model, we conclude that the optimal grip height is 3 cm in males and 2 cm in females in terms of grip strength and force efficiency. In addition, the model is validated by RMS EMG data from correlation analysis between the predicted internal tendon forces, with RMS EMG values of 0.65 for Flexor Pollicis Longus, 0.57 for Flexor Pollicis Brevis, and 0.61 for Adductor Pollicis.

Development of Two-Dimensional Biomechanical Modeling of the Thumb for Pipetting

The aim of this study is to develop a two-dimensional biomechanical static thumb model based on the posture of the hand using pipette. This model used hand anatomy and static equilibrium conditions to estimate internal tendon forces against a given external force. The input variables can be divided into two groups: 1) joint angle, external load and bone length, which are directly measured from the test; and 2) tendon force ratio and moment arm, which are adopted from previous studies. The thumb model was simulated using an FSR (forcesensing resistor) and validated using an Electromyography (EMG) system with four grip heights from 1 to 4 cm and with two tasks: Aspirating and Dispensing. A similar trend was observed between the simulation and EMG results. The average thumb pressure for Dispensing tasks is about 3.1 times greater than that for Aspirating, and the overall force efficiency ratio for both tasks is around 8 times the external load. The optimal grip height is 3 cm in terms of grip strength, 1 or 3 cm in terms of minimum internal force and 1 cm in terms of force efficiency. Overall, the optimal grip height is 1 or 3 cm.

Variability of Grip Kinetics during Adult Signature Writing

Grip kinetics and their variation are emerging as important considerations in the clinical assessment of handwriting pathologies, fine motor rehabilitation, biometrics, forensics and ergonomic pen design. This study evaluated the intra- and inter-participant variability of grip shape kinetics in adults during signature writing. Twenty (20) adult participants wrote on a digitizing tablet using an instrumented pen that measured the forces exerted on its barrel. Signature samples were collected over 10 days, 3 times a day, to capture temporal variations in grip shape kinetics. A kinetic topography (i.e., grip shape image) was derived per signature by time-averaging the measured force at each of 32 locations around the pen barrel. The normalized cross correlations (NCC) of grip shape images were calculated within- and between-participants. Several classification algorithms were implemented to gauge the error rate of participant discrimination based on grip shape kinetics. Four different grip shapes emerged and several participants made grip adjustments (change in grip shape or grip height) or rotated the pen during writing. Nonetheless, intra-participant variation in grip kinetics was generally much smaller than inter-participant force variations. Using the entire grip shape images as a 32-dimensional input feature vector, a K-nearest neighbor classifier achieved an error rate of % in discriminating among participants. These results indicate that writers had unique grip shape kinetics that were repeatable over time but distinct from those of other participants. The topographic analysis of grip kinetics may inform the development of personalized interventions or customizable grips in clinical and industrial applications, respectively.

The effect of lower body stabilization and different writing tools on writing biomechanics in children with cerebral palsy

A high percentage of children with cerebral palsy (CP) have difficulty keeping up with the handwriting demands at school. Previous studies have addressed the effects of proper sitting and writing tool on writing performance, but less on body biomechanics. The aim of this study was to investigate the influence of lower body stabilization and pencil design on body biomechanics in children with CP. Fourteen children (12.31±4.13 years old) with CP were recruited for this study. A crossover repeated measures design was employed, with two independent variables: lower body stabilization (with/without) and pencil (regular/assigned grip height/biaxial). The writing task was to trace the Archimedean spiral mazes. Electromyography (EMG) of the upper extremity, the wrist flexion/extension movements, and the whole body photography were recorded to quantify the changes in posture and upper extremity biomechanics. Two-way repeated measures ANOVA was used for statistical analysis. No significant main effects were revealed in the EMG and wrist kinematics. The lower body stabilization significantly decreased the trunk lateral and forward deviations, and the visual focus-vertical angle. The biaxial pencil and the assigned grip height design significantly decreased the head, shoulder, trunk, and pelvic deviations compared with the regular design. The results indicated that the lower body positioning was effective in improving the trunk posture. A pencil with an assigned grip height or with a biaxial design could improve head, shoulder, trunk and pelvic alignment, but did not influence the muscle exertion of the upper extremity. This study could provide guidelines for parents, teachers and clinicians regarding the selection of writing tools and the knowledge of proper positioning for the children with handwriting difficulties. Further analyses can focus on the design, modification and clinical application of assitive sitting and writing devices for the use in children with handwriting difficulties.

The Influence IV Pole Height and Grip Height on Gait of Healthy People Ages 60-70

The Influence IV Pole Height and Grip Height on Gait of Healthy People Ages 60-70

Learning to grasp efficiently: The development of motor planning and the role of observational learning

We examined whether 18-, 24-, and 42-month-old children, like adults, prospectively adjust their hand movements to insure a comfortable hand posture at the endpoint, and whether children can learn to grasp efficiently by observation. The task required grasping a bar and fitting it into a hollow cylinder in order to make it light up. Measures of quantitative (grip height), as well as qualitative (grip type) prospective grip adaptation were analyzed. Grip height adaptation was found reliably by 24 months, grip type adaptation by 3 years. The ability to learn efficient grasping by observation seems however very restricted.

How does a Psittacanthus robustus Mart. population structure relate to a Vochysia thyrsoidea Pohl. host population?

Distribution of parasitic plants is directly linked with the distribution of host species and behavioral patterns of seed dispersers. Psittacanthus robustus (Loranthaceae) is a neotropical hemiparasite that mainly colonizes species of the family Vochysiaceae. Vochysia thyrsoidea is the main host of P. robustus and is commonly found in areas of cerrado rupestre (rocky savanna), an abundant vegetation in our study site. We conducted the study in the ecological park Parque Ecológico Quedas do Rio Bonito (PEQRB), over an area of 2.82 ha of cerrado rupestre. The objective of this work was to investigate population structure, parasitic behavior (mistletoe grip height and circumference of host branch), and spatial distribution of Psittacanthus robustus on a population of Vochysia thyrsoidea. We sampled 267 V. thyrsoidea individuals and found that the population had a random distribution pattern. Seventy-nine individuals (29.6% of the sample population) hosted the hemiparasite, to a total of 193 P. robustus individuals. The number of mistletoe individuals per host plant ranged between 1 and 12. The V. thyrsoidea individuals most infested with mistletoes were those reaching greater heights. The correlation between height of host plant and preferred grip height was highly significant, with the preferred grip height being the uppermost portions of host plants. The crown size of P. robustus individuals ranged between 10 and 230 cm. The main disperser of P. robustus fruit was found to be swallow-tanager Tersina viridis viridis. Its activities led to a clumped pattern of spatial distribution of the hemiparasite along with higher infestation in larger trees.

Energy loss in the pole vault take-off and the advantage of the flexible pole

A model of pole vaulting with a flexible pole was developed with the aim of predicting the optimum take-off technique and pole characteristics for a typical world-class pole vaulter. The key features of the model are that it includes the interdependence of the take-off angle and the take-off velocity, and that it accounts for the energy losses in the pole plant and take-off phases of the vault. A computer simulation program was used to systematically investigate the effect of different combinations of take-off velocity, takeoff angle, grip height and pole stiffness on the performance of a world-class male vaulter. For the highest vault with this model, the vault height and the optimum combination of take-off velocity, take-off angle, grip height and pole stiffness were in good agreement with measured values for world-class vaulters using fibreglass poles. The results from the model were compared with those from a model of vaulting with a rigid pole. There was a clear performance advantage to vaulting with a flexible pole. The flexible pole produced a 90 cm higher vault by allowing a 60 cm higher grip and by giving a 30 cm greater push height. There are two main advantages of a flexible fibreglass pole over a rigid pole made of steel or bamboo. A flexible pole reduces the energy dissipated in the vaulter’s body during the pole plant, and it also lowers the optimum take-off angle so that the athlete loses less kinetic energy when jumping up at take-off.

ACROSKI: TWO POLE GRIPS ARE BETTER THAN ONE FOR JUMPING

1816 Principles of biomechanics once available only to researchers are now being used by coaches to improve athletic performance. When studying the existing guidelines for the length of poles used by Acro skiers, it was questioned whether the grip height above the snow would effect performance. The application of these biomechanical principles enabled a simple change in equipment to determine if they could improve athletes' jumps. Jumps are a key element of each Acro ski run, 25 - 50% of the score. By shortening the length of the ski pole, such that each elbow joint is at 90 degrees in the takeoff position, we found that athletes' could jump 11% higher than with traditional length Acro ski poles. This improvement results in jumps with greater amplitudes and speeds of rotation. Computer digitization was used to measure the height attained during a jump with both types of poles. Results from this study saw this increase in efficiency translate to increased height (0.7% to over 20%) for jumpers as well as increased rotational speeds. Nine National Team skiers from four countries volunteered for this study. Each skier performed 10 jumps; 5 with their traditional length poles and 5 with a shorter pole. There was a 5.5 ± 1.5 cm (mean ± SEM) increase in peak vertical height resulting from use of the shorter inside (lead) pole, which was statistically significant (p=0.004). Mean jump height for all subjects was 51.3 ± 4.7 and 56.8 ± 4.2 cm for the high and low grip, respectively. This represented an 11% improvement in performance on average. Nine out of ten of the athletes showed an improvement in the mean maximum height attained while using the shorter lead pole (range −5 to 28%). There appeared to be a direct relationship between the amount of change in jump height and the amount of change between the original pole length and the shorter pole which allowed a 90 degree bend of the elbow. Skiers who started with proportionately longer poles tended to have greater improvement when they switched to the shorter pole.

棒高跳に関するバイオメカニクス的研究 : ポール弦反力から見た最大重心高増大のための技術的要因

An attempt was made to investigate three-dimensional box reation forces applied to the pole-tipduring pole vaulting, and to idenfify technical factors necessary for increasing the maximal height of center of gravity (C.G.) based on the pole-chord reaction forces (henceforth, PCF). The subjects (five pole vaulters and four decathletes) performed pole vaults to clear the cross bar set at a height of 82-93% of their personal best record. All trials were videotaped with four video cameras (60 fps), and box reaction forces (500Hz) were measured with a Kistler force platform on which a specially made vaulting box was bolted. Three-dimensional coordinates of points on the vaulting poles and body landmarks of vaulters were obtained using a DLT procedure. Impulse and PCF were calculated from the forces and coordinate data. Force exerted via the lower hand (henceforth, F_<Ly>) was calculated by solving equations of motion for the pole segment between the hands. For simplicity, the mass and moment of inertia of the pole segment were assumed to be zero. The horizontal impulse of box reaction forces in the pole-bending phase and verticalimpulse in the pole-straightening phase were significantly related to the maximal C.G.height (r=-0.701, p<0.05 and r=0.688, p<0.05, respectively). These impulses were significantly related to the PCF in each vaulting phase (r=-0.888, p<0.01 and r=0.981, p<0.001, respectively). Three PCF patterns were found: Type A, in which PCF during the pole-straightening phase exceeded that during the pole-bending phase; Type B, in which the pattern of Type A was reversed; Type C, in which the PCFs during both phases were almost equal. It has been suggested by some researchers that bending and straightening moments applied to the pole by F_<Ly> influence the magnitude of pole-bending and the PCF. Type A subjects exerted F_<Ly> in a pushing direction (applied bending moment) during the pole-bending phase, and in a pulling direction (applied straightening moment) during the pole-straightening phase. The lower hand technique shown in Type A seemed more appropriate for increasing the maximal C.G. height, because (1) the vaulter was able to use a higher grip height due to the increased magnitude of pole-bending, and (2) the vertical impulse of the box reaction force was increased due to enhancement of PCF in the pole-straightening phase.

Mathematical Model of the Takeoff Phase in the Pole Vault

A mathematical model is presented of the takeoff phase in the pole vault for an athlete vaulting with a rigid pole. An expression is derived that gives the maximum height that the vaulter may grip on the pole in terms of the takeoff velocity, the takeoff angle, the athlete's vertical reach, and the depth of the takeoff box. Including the dependence of the vaulter's takeoff velocity on the takeoff angle reveals that there is an optimum takeoff angle that maximizes the vaulter's grip height. It is also shown that taller and faster vaulters are able to grip higher on the pole. The results of the investigation compare favorably with data for vaulters using bamboo and steel poles.

Human strength: measurements of maximum isometric forces in industry.

Within the framework of an on-going research project, the maximum isometric forces of staff working in production were measured for nine test conditions representative for manual material handling (n=3600), The technique for the measurement of maximum human forces depending on body posture, the test set-up, and the procedures used for data analysis plus the preliminary group results (n=1245) are described. The results show a marked influence of the initial grip height on the maximum forces achievable for the lifting of a stacking case with both hands. Under comparable grip height and type of grip, small differences between the lifting forces with one or with two hands exist. In comparison to males, females clearly have lower maximum isometric forces than is generally supposed.

Use of separate hand locations to calculate ground reaction force exerted on a vaulting pole.

A model was developed to permit calculation of the force exerted by the ground on a vaulting pole given the flexibility characteristics of the pole, the grip height of the upper hand, and the coordinates of each of the two hands relative to the base of the pole. The flexural rigidity of the pole was assumed constant throughout the length of the pole and not subject to hysteresis or dynamic loading effects. The model was based on the following rationale: knowing the initial angle of the base of the pole (beta 0) and the force vector (F1) exerted by the ground on the pole, it was possible to estimate the shape of the pole and the coordinates of the two hands following an iterative procedure. Conversely, it was possible to find a combination of beta 0 and F1 that made the pole fit two specified hand locations.