Causes of left-right ball inaccuracy in overarm throws made by cerebellar patients

2000 ◽  
Vol 130 (4) ◽  
pp. 441-452 ◽  
Author(s):  
D. Timmann ◽  
S. Watts ◽  
J. Hore
Keyword(s):  
Overarm Throws

Kinematics of wrist joint flexion in overarm throws made by skilled subjects

2004 ◽  
Vol 154 (3) ◽  
pp. 382-394 ◽  
Author(s):  
P. L. Gribble ◽  
D. B. Debicki ◽  
S. Watts ◽  
J. Hore
Keyword(s):  
Wrist Joint ◽  
Joint Flexion ◽  
Overarm Throws

Timing of finger opening and ball release in fast and accurate overarm throws

1995 ◽  
Vol 103 (2) ◽  
Author(s):  
J. Hore ◽  
S. Watts ◽  
J. Martin ◽  
B. Miller
Keyword(s):  
Ball Release ◽  
Overarm Throws

Control of Joint Rotations in Overarm Throws of Different Speeds Made by Dominant and Nondominant Arms

2005 ◽  
Vol 94 (6) ◽  
pp. 3975-3986 ◽  
Author(s):  
Jon Hore ◽  
Michael O’Brien ◽  
Sherry Watts
Keyword(s):  
Future Study ◽  
Angular Position ◽  
Joint Space ◽  
Fast Time ◽  
Ball Speed ◽  
Time Scaling ◽  
Space Pattern ◽  
Interaction Torques ◽  
Overarm Throws ◽  
Search Coil Technique

We tested the hypothesis that dominant and nondominant overarm throws of different speeds are made by time-scaling of joint rotations, i.e., by joint rotations that have the same positions and amplitudes but that are scaled in time. Eight skilled subjects stood and made overarm throws with both their dominant and nondominant arms. Six joint rotations were computed from recordings of arm segments made with the search-coil technique. Throws made with nondominant arms were less accurate and had lower ball speeds. In contrast to the hypothesis, dominant arms showed large and consistent differences between fast and slow throws in six-dimensional angular position joint space. These same throws showed similar hand angular paths when these were time-scaled based on ball speed. Nondominant arms showed only small differences in angular position joint space in fast and slow throws. It is concluded that a joint space pattern resembling that predicted by time-scaling occurs in nondominant arm throwing when it is unskilled. However, time-scaling does not occur in dominant arm throwing, i.e., a skilled fast throw is not simply a skilled slow throw whose joint positions and amplitudes remain constant but whose joint velocities are sped-up. We hypothesize for future study that, when subjects first learn to throw at different speeds with their dominant arms, they use time-scaling of joint rotations that involves compensating for interaction torques; then as they become skilled at throwing fast, time-scaling is superseded by a more complex pattern of interjoint coordination that involves exploiting interaction torques.

Prediction and Compensation by an Internal Model for Back Forces During Finger Opening in an Overarm Throw

1999 ◽  
Vol 82 (3) ◽  
pp. 1187-1197 ◽  
Author(s):  
J. Hore ◽  
S. Watts ◽  
D. Tweed
Keyword(s):  
Internal Model ◽  
Middle Finger ◽  
Proximal Interphalangeal Joint ◽  
Force Transducers ◽  
Ball Release ◽  
Overarm Throw ◽  
Finger Motion ◽  
The Moment ◽  
Finger Control ◽  
Overarm Throws

Previous studies have indicated that timing of finger opening in an overarm throw is likely controlled centrally, possibly by means of an internal model of hand trajectory. The present objective was to extend the study of throwing to an examination of the dynamics of finger opening. Throwing a heavy ball and throwing a light ball presumably require different neural commands, because the weight of the ball affects the mechanics of the arm, and particularly, the mechanics of the finger. Yet finger control is critical to the accuracy of an overarm throw. We hypothesized that finger opening in an overarm throw is controlled by a central mechanism that uses an internal model to predict and compensate for movement-dependent back forces on the fingers. To test this idea we determined whether finger motion is affected by back forces, i.e., whether larger back forces cause larger finger extensions. Back forces were varied by having subjects throw, at the same fast speed, tennis-sized balls of different weights (14, 55, and 196 g). Arm- and finger-joint rotations were recorded with the search-coil technique; forces on the middle finger were measured with force transducers. Recordings showed that during ball release, the middle finger experienced larger back forces in throws with heavier balls. Nevertheless, most subjects showed proximal interphalangeal joint extensions that were unchanged or actually smaller with the heavier balls. This was the case for the first throw and for all subsequent throws with a ball of a new weight. This suggests that the finger flexors compensated for the larger back forces by exerting larger torques during finger extension. Supporting this view, at the moment of ball release, all finger joints flexed abruptly due to the now unopposed torques of the finger flexors, and the amplitude of this flexion was proportional to ball weight. We conclude that in overarm throws made with balls of different weights, the CNS predicts the different back forces from the balls and adjusts finger flexor torques accordingly. This is consistent with the view that finger opening in overarm throws is controlled by means of an internal model of the motor apparatus and the external load.

Timing of ball release in overarm throws affects ball speed in unskilled but not skilled individuals

2005 ◽  
Vol 23 (8) ◽  
pp. 805-816 ◽  
Author(s):  
E Jegede ◽  
S Watts ◽  
L Stitt ◽  
J Hore
Keyword(s):  
Ball Speed ◽  
Ball Release ◽  
Overarm Throws

Braking of elbow extension in fast overarm throws made by skilled and unskilled subjects

2005 ◽  
Vol 164 (3) ◽  
pp. 365-375 ◽  
Author(s):  
J. Hore ◽  
D. B. Debicki ◽  
S. Watts
Keyword(s):  
Elbow Extension ◽  
Overarm Throws

Failure of Cerebellar Patients to Time Finger Opening Precisely Causes Ball High-Low Inaccuracy in Overarm Throws

1999 ◽  
Vol 82 (1) ◽  
pp. 103-114 ◽  
Author(s):  
D. Timmann ◽  
S. Watts ◽  
J. Hore
Keyword(s):  
Arm Movement ◽  
Three Dimensions ◽  
Central Command ◽  
Hand Trajectory ◽  
Release Times ◽  
Ball Release ◽  
Timing Variability ◽  
Medium Speed ◽  
Release Timing ◽  
Overarm Throws

We investigated the idea that the cerebellum is required for precise timing of fast skilled arm movements by studying one situation where timing precision is required, namely finger opening in overarm throwing. Specifically, we tested the hypothesis that in overarm throws made by cerebellar patients, ball high-low inaccuracy is due to disordered timing of finger opening. Six cerebellar patients and six matched control subjects were instructed to throw tennis balls at three different speeds from a seated position while angular positions in three dimensions of five arm segments were recorded at 1,000 Hz with the search-coil technique. Cerebellar patients threw more slowly than controls, were markedly less accurate, had more variable hand trajectories, and showed increased variability in the timing, amplitude, and velocity of finger opening. Ball high-low inaccuracy was not related to variability in the height or direction of the hand trajectory or to variability in finger amplitude or velocity. Instead, the cause was variable timing of finger opening and thereby ball release occurring on a flattened arc hand trajectory. The ranges of finger opening times and ball release times (timing windows) for 95% of the throws were on average four to five times longer for cerebellar patients; e.g., across subjects mean ball release timing windows for throws made under the medium-speed instruction were 11 ms for controls and 55 ms for cerebellar patients. This increased timing variability could not be explained by disorder in control of force at the fingers. Because finger opening in throwing is likely controlled by a central command, the results implicate the cerebellum in timing the central command that initiates finger opening in this fast skilled multijoint arm movement.

Overarm throws with the nondominant arm: kinematics of accuracy

1996 ◽  
Vol 76 (6) ◽  
pp. 3693-3704 ◽  
Author(s):  
J. Hore ◽  
S. Watts ◽  
D. Tweed ◽  
B. Miller
Keyword(s):  
Right Hemisphere ◽  
Angular Position ◽  
Ball Impact ◽  
Hand Trajectory ◽  
Finger Extension ◽  
Ball Release ◽  
Left And Right ◽  
The Right ◽  
Timing Of Onset ◽  
Overarm Throws

1. Overarm throws made with the nondominant arm are usually less accurate than those made with the dominant arm. The objective was to determine the errors in the joint rotations associated with this inaccuracy, and thereby to gain insight into the neural mechanisms that contribute to skill in overarm throwing. 2. Overarm throws from both left and right arms were recorded on different occasions as six right-handed subjects sat with a fixed trunk and threw 150 tennis balls at about the same speed at a 6-cm square on a target grid 3 m away. Joint rotations at the shoulder, elbow, wrist, and finger, and arm translations, were computed from recordings of arm segment orientations made with the magnetic-field search-coil technique. 3. All subjects threw less accurately in this task with the left (nondominant) arm. For throws made with the left arm, the height of ball impact on the target grid was related to hand trajectory length and to hand orientation in space at ball release, but not to hand trajectory height. 4. Two hypotheses were proposed to explain the decreased ball accuracy in the high-low direction during throwing with the nondominant arm: that it was caused by increased variability in the velocity or timing of onset of rotations at proximal joints (which determine the path of the hand through space) or increased variability in the velocity or timing of onset of finger extension (which determine the moment of ball release). 5. A prediction of the first hypothesis was that proximal joint rotations should be more variable in throws with the left arm. This was the case for the majority of proximal joint rotations in the six subjects when variability was examined in joint space. However, some proximal joint rotations were more variable in the right arm. 6. The first hypothesis was directly tested by determining whether hand angular position in space (which represents the sum of all proximal joint rotations) was related to ball impact height on the target grid at a fixed translational position in the throw. No relation was found between these variables for throws with the left arm in four subjects, whereas a weak relation was found for two subjects. It was concluded that, considering all subjects, the first hypothesis could not explain the results. 7. In contrast, in agreement with the second hypothesis, a strong relation (P < 0.001) was found in all subjects between ball impact height on the target grid and time of ball release for throws with the left arm, and with time of onset of finger extension. 8. Across all six subjects the timing precision (windows) for 95% of the throws was (for ball release) right arm, 9.3 ms; left arm, 22.5 ms; (for onset of finger extension) right arm, 13.7 ms; left arm, 26.7 ms. 9. Timing of onset of finger extension was no less accurate than timing of onset of other joint rotations for both left and right arms. However, simulations of throws showed that, for the same error in timing, finger extension had twice as large an effect on ball direction as any other joint rotation. Timing errors at the fingers have a greater effect than errors at other joints because finger errors are scaled by the higher angular velocity of the hand in space rather than by the smaller angular velocities of the individual joints. 10. It is concluded that although rotations were in general more variable at both proximal and distal joints of the nondominant (left) arm, the major cause of its decreased throwing accuracy was increased variability at the distal joints, i.e., in the timing of onset of finger extension. This may be due to a lack of precision in the commands from the right hemisphere to the left fingers in right-handed throwers.

Finger flexion does not contribute to ball speed in overarm throws

1996 ◽  
Vol 14 (4) ◽  
pp. 335-342 ◽  
Author(s):  
J. Hore, S. Watts, J. Martin
Keyword(s):  
Ball Speed ◽  
Finger Flexion ◽  
Overarm Throws
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