Impulse-Variability Theory: Implications for Ballistic, Multijoint Motor Skill Performance

Choice of low-pass filter influences practical interpretation of ball kicking motions: the effect of a time-frequency filter method

When studying ball kicking, conventional low-pass filters may distort kick leg kinematics near the time of foot-to-ball contact, leading to flawed practical interpretation of the skill. Time-frequency filters are a viable alternative but are not widely used. This study compared a fractional Fourier filter (FrFF) with conventional filters (CF) methods for estimating common parameters used to define kicking performance. Instep kicks from 23 experienced soccer players were captured by 3D motion analysis (1000 Hz), and kick leg foot velocities, knee angular velocities and ankle dorsi-plantarflexion angles compared between the FrFF and variations of a Butterworth CF. The FrFF and CFs using a higher cut-off frequency (>70 Hz) successfully detected lower leg motion prior to, during and following impact, whereas CFs with low cut-off frequencies (<20 Hz) attenuated motion near impact. Truncating data at impact provided valid pre-impact kinematics, but ignored information thereafter. Rather than decelerating the lower leg to conserve accuracy, 'kicking through the ball' should be considered a valid coaching cue. Further, controlling ankle plantar flexion to ensure efficient impact mechanics may be important for skilled kicking. Practitioners should consider how choice of filter will affect their data, and use of time-frequency methods can help inform empirically grounded coaching practices.

Applications of the Speed-Accuracy Trade-off and Impulse-Variability Theory for Teaching Ballistic Motor Skills

Bridging the gap between innovative research and teaching is a fundamental necessity for physical education practitioners to promote motor skill development and competency. This requires practitioners to understand, synthesize, and appropriately apply relevant research from different academic domains in their instructional environments. Ballistic motor skills such as kicking, throwing, and striking are fundamentally integrated into many games and sports and provide a foundation for physical activity and fitness for children and adults. Unfortunately, many individuals do not attain a high level of competence in these types of skills by adolescence. The purpose of this review is to integrate theory, pedagogical best practices, and current evidence on studies relating to Fitts' Law's application of the speed-accuracy trade-off and impulse-variability theory to provide an evidence-based framework for promoting effective instructional environments for learning ballistic motor skills.

Examining Impulse-Variability Theory and the Speed-Accuracy Trade-Off in Children's Overarm Throwing Performance

This study examined variability in throwing speed and spatial error to test the prediction of an inverted-U function (i.e., impulse-variability [IV] theory) and the speed-accuracy trade-off. Forty-five 9- to 11-year-old children were instructed to throw at a specified percentage of maximum speed (45%, 65%, 85%, and 100%) and hit the wall target. Results indicated no statistically significant differences in variable error across the target conditions (p = .72), failing to support the inverted-U hypothesis. Spatial accuracy results indicated no statistically significant differences with mean radial error (p = .18), centroid radial error (p = .13), and bivariate variable error (p = .08) also failing to support the speed-accuracy trade-off in overarm throwing. As neither throwing performance variability nor accuracy changed across percentages of maximum speed in this sample of children as well as in a previous adult sample, current policy and practices of practitioners may need to be reevaluated.

Sensorimotor Learning during a Marksmanship Task in Immersive Virtual Reality

Sensorimotor learning refers to improvements that occur through practice in the performance of sensory-guided motor behaviors. Leveraging novel technical capabilities of an immersive virtual environment, we probed the component kinematic processes that mediate sensorimotor learning. Twenty naïve subjects performed a simulated marksmanship task modeled after Olympic Trap Shooting standards. We measured movement kinematics and shooting performance as participants practiced 350 trials while receiving trial-by-trial feedback about shooting success. Spatiotemporal analysis of motion tracking elucidated the ballistic and refinement phases of hand movements. We found systematic changes in movement kinematics that accompanied improvements in shot accuracy during training, though reaction and response times did not change over blocks. In particular, we observed longer, slower, and more precise ballistic movements that replaced effort spent on corrections and refinement. Collectively, these results leverage developments in immersive virtual reality technology to quantify and compare the kinematics of movement during early learning of full-body sensorimotor orienting.

Force-Time Entropy of Isometric Impulse

The relation between force and temporal variability in discrete impulse production has been viewed as independent (R. A. Schmidt, H. Zelaznik, B. Hawkins, J. S. Frank, & J. T. Quinn, 1979 ) or dependent on the rate of force (L. G. Carlton & K. M. Newell, 1993 ). Two experiments in an isometric single finger force task investigated the joint force-time entropy with (a) fixed time to peak force and different percentages of force level and (b) fixed percentage of force level and different times to peak force. The results showed that the peak force variability increased either with the increment of force level or through a shorter time to peak force that also reduced timing error variability. The peak force entropy and entropy of time to peak force increased on the respective dimension as the parameter conditions approached either maximum force or a minimum rate of force production. The findings show that force error and timing error are dependent but complementary when considered in the same framework with the joint force-time entropy at a minimum in the middle parameter range of discrete impulse.

A Nonlinear Model for Mouse Pointing Task Movement Time Analysis Based on Both System and Human Effects

This paper provides a detailed model for analyzing movement time performance during rapid goal-directed point- and-click motions with a computer mouse. Twelve typically developed individuals and eleven youths with cerebral palsy conducted point and click computer tasks from which the model was developed. The proposed model is nonlinear and based on both system (target width and movement amplitude) and human effects (erroneous clicks, number of submovements, number of slip-offs, curvature index, and average speed). To ensure successful targeting by youths with cerebral palsy, the index of difficulty was limited to a range of 1.58 - 3.0 bits. For consistency, the same range was used with both groups. The most significant contributing human effect to movement time was found to be the curvature index for both typically developed individuals and individuals with cerebral palsy. This model will assist in algorithm development to improve cursor speed and accuracy for youths with cerebral palsy.

Bimanual and unimanual convergent goal-directed movement times

Three experiments are reported, investigating the effects of using 1 or 2 hands when making convergent low index of difficulty (ID) and visually controlled movements (2 hands meeting together). The experiments involved movements in four different cases-a probe held in the right hand and moved to a target held in the stationary left hand, vice versa of this arrangement, both hands moving with the probe in the right hand and target in the left hand, and vice-versa of this arrangement. Experiments were the standard Fitts' paradigm, moving a pin into a hole and a low-ID task. In Fitts' task, 2-hand movements were faster than 1 hand only at higher IDs; this was also the case in the pin-to-hole transfer task and the movement times were lower when the pin was held in the preferred hand. Movements made with low ID showed a small effect of 1- or 2-handed movements, with the effective amplitude of the movement being reduced by about 20% when 2 hands were used.

Kinematics of a striking task: accuracy and speed-accuracy considerations

Handballing in Australian football (AF) is the most efficient passing method, yet little research exists examining technical factors associated with accuracy. This study had three aims: (a) To explore the kinematic differences between accurate and inaccurate handballers, (b) to compare within-individual successful (hit target) and unsuccessful (missed target) handballs and (c) to assess handballing when both accuracy and speed of ball-travel were combined using a novel approach utilising canonical correlation analysis. Three-dimensional data were collected on 18 elite AF players who performed handballs towards a target. More accurate handballers exhibited a significantly straighter hand-path, slower elbow angular velocity and smaller elbow range of motion (ROM) compared to the inaccurate group. Successful handballs displayed significantly larger trunk ROM, maximum trunk rotation velocity and step-angle and smaller elbow ROM in comparison to the unsuccessful handballs. The canonical model explained 73% of variance shared between the variable sets, with a significant relationship found between hand-path, elbow ROM and maximum elbow angular velocity (predictors) and hand-speed and accuracy (dependant variables). Interestingly, not all parameters were the same across each of the analyses, with technical differences between inaccurate and accurate handballers different from those between successful and unsuccessful handballs in the within-individual analysis.

Progressive resistance, whole body long-axis rotational training improves kicking motion motor performance

OBJECTIVES

To evaluate lower extremity muscle activation, peak resultant ground reaction force (GRF) production and quickness during performance of a kicking motion following progressive resistance, whole body long-axis rotational training.

DESIGN

Randomized, controlled study.

SETTING

Kinesiological research laboratory.

PARTICIPANTS

Thirty-six healthy subjects were assigned to a training (Group 1) or to a control (Group 2) group.

MAIN OUTCOME MEASURES

Time-synchronized EMG (1000 Hz), peak resultant GRF (1000 Hz) and two-dimensional kinematic (60 Hz) data were collected as subjects responded to an audio cue by kicking a cone. Group mean change differences (MCD) were compared using independent sample t-tests. Fisher's exact tests were used to determine group differences in the proportion of subjects that displayed earlier activation responses post-training.

RESULTS

Group 1 MCD revealed earlier gluteus maximus, gluteus medius, rectus femoris, medial hamstrings, and biceps femoris activation timing than Group 2 (P ≤ 0.006) and more Group 1 subjects displayed earlier activation of these muscles post-training (P ≤ 0.041). Group 1 MCD also revealed earlier peak resultant GRF timing and improved "kick quickness" than Group 2 (P ≤ 0.014) and more Group 1 subjects displayed earlier response timing for these variables post-training (P = 0.035).

CONCLUSION

Progressive resistance, whole body long-axis rotational training may improve performance during sports movements that require quick, integrated trunk-lower extremity function.