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Satyajit Ambike, Daniela Mattos, Vladimir Zatsiorsky and Mark Latash

compliance with the protocol approved by the Office for Research Protection of the Pennsylvania State University. Equipment and Procedures Subjects sat in a chair with their right forearm resting on top of a table. Each subject was allowed to choose a comfortable hand posture with all fingers comfortably

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Robert MacKenzie, Linda Monaghan, Robert A. Masson, Alice K. Werner, Tansinee S. Caprez, Lynsey Johnston and Ole J. Kemi

. Accordingly, changes to those affect maximal climbing performance. Previous studies have identified many of those characteristics, such as upper-body and shoulder strength 6 – 8 including explosive power, 5 , 6 , 9 forearm grip and finger strength, 5 , 10 – 13 upper-body endurance capacity 10 , 14 and

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Jumpei Mizuno, Masashi Kawamura and Minoru Hoshiyama

head in the MEG dewar (PQ-1160C; RICOH, Tokyo, Japan). A 14-in. screen was placed 30 cm in front of the participants, and a movie was projected on the screen from the outside of the room. On the screen, an initial instruction and finger movements were presented in a movie. Figure  1 shows the sequence

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Siobhán O’Connor, Róisín Leahy, Enda Whyte, Paul O’Donovan and Lauren Fortington

injury type n/a 3.3–7.5 n/a 20.6–28.6 n/a 7.4–12.9 n/a 56.2–65.3 n/a n/a n/a Note . n/a = not applicable. Upper limb injuries were most often to the hand (26.2%), fingers (26.2%), and thumb (16.8%). Fractures accounted for 40.2% of all upper limb injuries. Injuries of the trunk/back were primarily

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Joel R. Martin, Mark L. Latash and Vladimir M. Zatsiorsky

This study investigated the effects of modifying contact finger forces in one direction—normal or tangential—on the entire set of the contact forces, while statically holding an object. Subjects grasped a handle instrumented with finger force-moment sensors, maintained it at rest in the air, and then slowly: (1) increased the grasping force, (2) tried to spread fingers apart, and (3) tried to squeeze fingers together. Analysis was mostly performed at the virtual finger (VF) level (the VF is an imaginable finger that generates the same force and moment as the four fingers combined). For all three tasks there were statistically significant changes in the VF normal and tangential forces. For finger spreading/squeezing the tangential force neutral point was located between the index and middle fingers. We conclude that the internal forces are regulated as a whole, including adjustments in both normal and tangential force, instead of only a subset of forces (normal or tangential). The effects of such factors as EFFORT and TORQUE were additive; their interaction was not statistically significant, thus supporting the principle of superposition in human prehension.

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S. L. Hong, M-H. Lee and K.M. Newell

This experiment examined the magnitude and structure of force variability in isometric index finger force production tasks at 5, 15, 25, 35, 45, 55, 65, 75, 85, and 95% of maximal force in two different finger orientations. In the finger flexion task, the participants generated a downward isometric force through index finger flexion. In the finger abduction task, isometric force was generated by adducting the index finger (mediolateral motion of the middle finger and forearm were restricted). The task-related, normal force (Fz) and tangential forces (Fx and Fy) were collected with a three-dimensional force transducer. The standard deviation (SD) of the task-related force output (Fz) increased exponentially with force level. With increasing force level, approximate entropy (ApEn, a measure of irregularity) of Fz followed an inverted-U function for finger flexion, but decreased linearly in finger abduction. However, changes in the ApEn of the tangential forces were generally opposite to that of Fz, revealing compensations in the irregularity of force output between force dimensions. The findings provide evidence that force variability is related to muscle force-length characteristics (Feldman, 1966; Gottlieb & Agarwal, 1988).

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Jaebum Park, Brian S. Baum, You-Sin Kim, Yoon Hyuk Kim and Jae Kun Shim

The aim of this study was to test the mechanical advantage (MA) hypothesis in multifinger torque production tasks in humans: fingers with longer moment arms produce greater force magnitudes during torque production tasks. There were eight experimental conditions: two prehension types determined by different mechanical constraints (i.e., fixed- and free-object prehension) with two torque directions (supination and pronation) and two torque magnitudes (0.24 and 0.48 N·m). The subjects were asked to produce prescribed torques during the fixed-object prehension or to maintain constant position of the free hand-held object against external torques. The index of MA was calculated for agonist and antagonist fingers, which produce torques in the same and opposite directions to the target torques, respectively. Within agonist fingers, the fingers with longer moment arms produced greater grasping forces while within antagonist fingers, the fingers with shorter moment arms produced greater forces. The MA index was greater in the fixed-object condition as compared with the free-object condition. The MA index was greater in the pronation condition than in the supination condition. This study supports the idea that the CNS utilizes the MA of agonist fingers, but not of antagonist fingers, during torque production in both fixed- and free-object conditions.

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Barry S. Mason, Viola C. Altmann and Victoria L. Goosey-Tolfrey

–3) around the shoulders, elbows, and wrists and no active finger function were categorized as “poor arm function” (PAF; arm score ≤ 1.5; n = 12). Those with no muscle weakness (MMT 4–5) around the shoulders, elbows, and wrists, but with minimal to no active finger function were categorized as “moderate arm

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Shinya Fujii and Shingo Oda

The aim of this study is to establish the effects of stick use on rhythmic bimanual coordination in drummers. Eighteen drummers performed a rapid antiphase coordination task using their fingers and handheld drumsticks. We found no significant differences in the speed of tapping between finger and stick-use tapping, while stick-use tapping had a larger peak force and smaller variability in coordination pattern than finger tapping. As a consequence, the quotient of the number of taps divided by the variability of coordination pattern, named the bimanual performance quotient, was higher for stick-use tapping than for finger tapping. A significant correlation was found between years of drumming experience and the bimanual performance quotient for both finger and stick-use tapping, but not between the years of drumming experience and the degree of improvement in the bimanual performance quotient with stick use relative to finger tapping. These results indicate that stick use enhances drummers’ bimanual coordination during rapid alternate tapping, whereas the degree of improvement with stick use does not depend on drumming experience.

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Jorge Arede, António Paulo Ferreira, Oliver Gonzalo-Skok and Nuno Leite

precision) were recorded for estimation of maturity status. Second digit and fourth digit ratio (2D:4D) were determined after measurements of the palmar surface of the fingers using steel vernier calipers (measuring to 0.05 mm), from a midpoint on the crease proximal to the palm to the tip of the finger