Kicking performance in relation to balance ability over the support leg.

Balance control is presumed to be a fundamental constraint on the organization of skilled movement. The current experiment explored whether single-leg balance ability predicted kicking performance on the other leg. Thirty-eight participants ranging widely in skill kicked a soccer ball with the right and left legs for maximum accuracy and velocity and performed single-leg balance on a force plate for 30 s with the right and left legs. Significant correlations between single-leg balance and kicking accuracy, but not velocity, were found. Left leg balance was more highly correlated than right leg balance with right (dominant) leg kicking accuracy. However, the same pattern of relations was not seen between single-leg balance and left (non-dominant) leg kicking accuracy. These findings provide preliminary support for the importance of balance ability in kicking performance. The importance of balance in the production of athletic skills is discussed and additional experimental paradigms are suggested that might further our knowledge in this area.

Spatial accuracy demand in aiming movements: kinematic analysis of subtended angle and tolerance width.

Subtended angle has been assumed to be an important factor in both response programming time and kinematic characteristics of aiming movements. Support for this assumption has come mainly from studies in which circular targets have been used. However, with circular targets, the subtended angle covaries with the size of the target in the principal direction of the movement (tolerance width). The purpose of this study was to examine the effects of tolerance width and subtended angle on aiming movement with multiple targets. Participants first hit a 5-cm-diameter circular target located 8 cm to the left of a starting position and then moved another 8 cm left to hit either a 5-cm diameter circular target or a 5- x 1-cm rectangular target oriented either horizontally or vertically, depending on the condition. Analysis showed that reaction times and movement times were longer for the vertical rectangular target, which had a smaller tolerance width than the other two targets. In addition, the vertical rectangular target also showed a greater percentage of secondary-submovement trials, lower movement velocity, and higher peak vertical displacement. Overall, the results indicate that the tolerance width of the target may impose more constraints on aiming movements than subtended angle.

Training with an upper-limb prosthetic simulator to enhance transfer of skill across limbs.

OBJECTIVE: To examine what effect bilateral transfer of movement across limbs may have in a person's ability to learn use of an upper-limb prosthetic simulator. DESIGN: Randomized trial. SETTING: University laboratory. PARTICIPANTS: Able-bodied subjects randomly assigned to 1 of 3 groups. INTERVENTIONS: Subjects performed 3 different tasks that required manipulation of objects with the simulator. Group 1 practiced with the simulator on the preferred limb and then transferred it to the nonpreferred limb; group 2 practiced with the simulator on the nonpreferred limb and then transferred it to the preferred limb; group 3 was a control group. Groups 1 and 2 underwent pretest trials, acquisition practice, posttest trials, and a 24-hour retention test; the control group followed the same design with the exception of acquisition practice. MAIN OUTCOME MEASURES: Elapsed time (1) from a signal to move until movement began (initiation time) and (2) from the beginning of movement to task completion (movement time). RESULTS: Compared with the controls, groups 1 and 2 significantly reduced initiation time across all tasks from pretest to posttest (P=.003) and from pretest to retention test (P=.029). Groups 1 and 2 did not differ from each other. Movement time did not differ among the groups in the posttest. However, groups 1 and 2 significantly (P=.026) reduced movement time across all tasks from pretest to retention test compared with the control group. Groups 1 and 2 did not differ from each other. CONCLUSION: The effects of bilateral transfer were evident for initiation time immediately on transfer, and this learning effect persisted to the retention test. The ability to execute movement, represented by movement time, occurred after consolidation of learning was complete. Cross-limb training with a prosthetic simulator may be useful for persons with recent unilateral upper-extremity amputation who are learning to use a prosthesis.

Sport competition as a dynamical self-organizing system.

The existence of structure in sport competition is implicated in the widespread practice of using the information gathered from a past contest to prepare for a future contest. Based on this reasoning, we previously analysed squash match-play for evidence of signature traits from among the stochastic relations between the various types of shot. The mixed findings from these analyses led us to re-analyse squash match-play as a dynamical system. Here, we extend this line of investigation with some suggestions as to how various sports might be described further within this theoretical framework. We offer some examples of dynamical interactions in dyadic (i.e. one vs one) and team (e.g. many vs many) sports, as well as some predictions from a dynamical systems analysis for these types of sports contests. This paper should serve to initiate further research into the complex interactions that occur in sport competition.