Temporal properties of the speed-accuracy trade-off for arm-pointing movements in various directions around the body

Human body movements are based on the intrinsic trade-off between speed and accuracy. Fitts’s law (1954) shows that the time required for movement is represented by a simple logarithmic equation and is applicable to a variety of movements. However, few studies have determined the role of the direction in modulating the performance of upper limb movements and the effects of the interactions between direction and distance and between direction and target size. This study examined the variations in temporal properties of the speed-accuracy trade-off in arm-pointing movements that directly manipulate objects according to the direction, distance, and target size. Participants performed pointing movements to the targets with 3 different sizes presented at 15 locations (5 directions and 3 distances) on a horizontal plane. Movement time (MT) for each trial in each condition was obtained. Subsequently, Mackenzie’s model (1992), MT = a + b log₂(D/W +1), where D and W represent the distance and width of the target, respectively, was fitted. The slope factor b, a fitted parameter in the equation, was calculated and evaluated according to the changes in the direction, distance, and target size. The results showed that MTs exhibited anisotropy in the hemifield, being the smallest in the right-forward direction. Additionally, the slope factor b, as a function of distance, was smaller in the rightward direction than in the forward and left-forward directions. These results suggest that the degree of difficulty of upper limb movements expands heterogeneously in various directions around the body

Evaluation of soccer team defense based on prediction models of ball recovery and being attacked

With the development of measurement technology, data on the movements of actual games in various sports are available and are expected to be used for planning and evaluating the tactics and strategy. In particular, defense in team sports is generally difficult to be evaluated because of the lack of statistical data. Conventional evaluation methods based on predictions of scores are considered unreliable and predict rare events throughout the entire game, and it is difficult to evaluate various plays leading up to a score. On the other hand, evaluation methods based on certain plays that lead to scoring and dominant regions are sometimes unsuitable to evaluate the performance (e.g., goals scored) of players and teams. In this study, we propose a method to evaluate team defense from a comprehensive perspective related to team performance based on the prediction of ball recovery and being attacked, which occur more frequently than goals, using player actions and positional data of all players and the ball. Using data from 45 soccer matches, we examined the relationship between the proposed index and team performance in actual matches and throughout a season. Results show that the proposed classifiers more accurately predicted the true events than the existing classifiers which were based on rare events (i.e., goals). Also, the proposed index had a moderate correlation with the long-term outcomes of the season. These results suggest that the proposed index might be a more reliable indicator rather than winning or losing with the inclusion of accidental factors.Comment: 12 pages, 4 figure

Temporal properties of preparation phase for arm-pointing movements in various directions.

In this study, we investigated how the temporal properties of the preparation phase for upper limb movements are affected by the reaching direction. Twelve right-handed participants performed three motor tasks, two types of reaching movements, and one finger-lifting movement. Reaching movements were performed from the home position to 15 target locations (5 directions and 3 distances), as quickly and precisely as possible, under two conditions: with and without pre-cueing of the target. The finger lifting movement was performed by lifting the index finger (from the home position) upward in the air as quickly as possible. The reaction time (RT), movement time (MT), and temporal kinematics of the index finger were obtained for each condition. In addition, differential RTs (DRT) were induced, implicitly representing the time required for the motor planning process to execute reaching movements. The results showed that the anisotropy of the DRTs was largest in the left-forward direction, suggesting that the temporal costs of the motor planning process depended on the movement direction. For the kinematic analysis, the MT in the left-forward direction was the largest among all directions. In addition, the time from peak velocity to termination of movement (TFPV) was significantly longer in the left-forward direction when the target pre-cueing was not provided than when it was provided. These results suggest that if a reaching movement under no-cue condition is initiated with insufficient time for the motor planning process, especially in the direction requiring large temporal costs, it relies more heavily on the online control process to accomplish the intended performance. It is likely that humans achieve their intended movements by allocating the amount of time before and after movement initiation according to the difficulty of control that varies in relation to the movement direction

Schematic diagram of experimental setup and procedure.

A: Experimental setup. Participants performed a pointing task on one of the targets presented in the workspace in front of their body. B: Experimental procedure. After pre-cueing and delay, participants reached the target with their right index finger as quickly as possible.</p

Reaction time relative to movement direction.

Human body movements are based on the intrinsic trade-off between speed and accuracy. Fitts’s law (1954) shows that the time required for movement is represented by a simple logarithmic equation and is applicable to a variety of movements. However, few studies have determined the role of the direction in modulating the performance of upper limb movements and the effects of the interactions between direction and distance and between direction and target size. This study examined the variations in temporal properties of the speed-accuracy trade-off in arm-pointing movements that directly manipulate objects according to the direction, distance, and target size. Participants performed pointing movements to the targets with 3 different sizes presented at 15 locations (5 directions and 3 distances) on a horizontal plane. Movement time (MT) for each trial in each condition was obtained. Subsequently, Mackenzie’s model (1992), MT = a + b log2(D/W +1), where D and W represent the distance and width of the target, respectively, was fitted. The slope factor b, a fitted parameter in the equation, was calculated and evaluated according to the changes in the direction, distance, and target size. The results showed that MTs exhibited anisotropy in the hemifield, being the smallest in the right-forward direction. Additionally, the slope factor b, as a function of distance, was smaller in the rightward direction than in the forward and left-forward directions. These results suggest that the degree of difficulty of upper limb movements expands heterogeneously in various directions around the body.</div

Coefficient of determination (R²) of each effect for each participant.

Coefficient of determination (R2) of each effect for each participant.</p

Index of difficulty calculated from each combined level of distance and target size.

Combinations of the distance and target size produced a distinct value of the index of difficulty (ID). For each ID, the movement time (MT) of the pointing movement was obtained. At each level of the distance and target size, MTs were fitted by Mackenzie’s model, then the values of slope factor b in each level, indicating the effects of target size (bSize_near, bSize_mid, and bSize_far) and distance (bDis_lag, bDis_mid, and bDis_sml) were obtained. Finally, bSize and bDis, showing generalized effect of target size and distance on MTs, was induced, respectively.</p

Movement time in each movement direction relative to index of difficulty.

The movement time according to the change in distance is shown by solid lines, whereas that according to the target size is shown by broken lines. The color and type of each line correspond to those shown in Fig 2.</p

Slope factor b relative to movement direction.

Human body movements are based on the intrinsic trade-off between speed and accuracy. Fitts’s law (1954) shows that the time required for movement is represented by a simple logarithmic equation and is applicable to a variety of movements. However, few studies have determined the role of the direction in modulating the performance of upper limb movements and the effects of the interactions between direction and distance and between direction and target size. This study examined the variations in temporal properties of the speed-accuracy trade-off in arm-pointing movements that directly manipulate objects according to the direction, distance, and target size. Participants performed pointing movements to the targets with 3 different sizes presented at 15 locations (5 directions and 3 distances) on a horizontal plane. Movement time (MT) for each trial in each condition was obtained. Subsequently, Mackenzie’s model (1992), MT = a + b log2(D/W +1), where D and W represent the distance and width of the target, respectively, was fitted. The slope factor b, a fitted parameter in the equation, was calculated and evaluated according to the changes in the direction, distance, and target size. The results showed that MTs exhibited anisotropy in the hemifield, being the smallest in the right-forward direction. Additionally, the slope factor b, as a function of distance, was smaller in the rightward direction than in the forward and left-forward directions. These results suggest that the degree of difficulty of upper limb movements expands heterogeneously in various directions around the body.</div