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Catching a ball at the right time and place: individual factors matter.

Cesqui B, d'Avella A, Portone A, Lacquaniti F - PLoS ONE (2012)

Bottom Line: Inter-individual variability was observed in several kinematic parameters, such as wrist trajectory, wrist velocity profile, timing and spatial distribution of the impact point, upper limb posture, trunk motion, and submovement decomposition.Individual idiosyncratic behaviors were consistent across different ball flight time conditions and across two experimental sessions carried out at one year distance.These results highlight the importance of a systematic characterization of individual factors in the study of interceptive tasks.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Neuromotor Physiology, IRCCS Santa Lucia Foundation, Rome, Italy.

ABSTRACT
Intercepting a moving object requires accurate spatio-temporal control. Several studies have investigated how the CNS copes with such a challenging task, focusing on the nature of the information used to extract target motion parameters and on the identification of general control strategies. In the present study we provide evidence that the right time and place of the collision is not univocally specified by the CNS for a given target motion; instead, different but equally successful solutions can be adopted by different subjects when task constraints are loose. We characterized arm kinematics of fourteen subjects and performed a detailed analysis on a subset of six subjects who showed comparable success rates when asked to catch a flying ball in three dimensional space. Balls were projected by an actuated launching apparatus in order to obtain different arrival flight time and height conditions. Inter-individual variability was observed in several kinematic parameters, such as wrist trajectory, wrist velocity profile, timing and spatial distribution of the impact point, upper limb posture, trunk motion, and submovement decomposition. Individual idiosyncratic behaviors were consistent across different ball flight time conditions and across two experimental sessions carried out at one year distance. These results highlight the importance of a systematic characterization of individual factors in the study of interceptive tasks.

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Interception point along the ball trajectory.(A) Left panel: schematic representation of the interception point index (computed as the ratio between the BC and AB ball trajectory arc lengths, see Methods). Right panel: for each flight time condition (T1–T3), subjects impact point along ball trajectory (normalized with respect to subject arm length) was uniquely determined by the movement time, hence the value of the difference between the extrapolated time of arrival of the ball at the frontal plane (tC) and the impact time (tB). However, for different flight times, subjects are free to vary tB and impact the ball at the same normalized distance (vertical line labeled “const distance”) or to catch the ball closer to their shoulder (horizontal line labeled “const time”). (B) Scatter plots of the interception index vs. tC−tB (mean ± SE across trials in the same conditions; SE are reported only when number of trials per block was larger than 2). A value of I = 0 indicates a catch at C while I = 1 indicates a catch in correspondence of the first possible interception point (A point), computed as the interception between the ball trajectory and the sphere centered at the shoulder joint of radius equal to arm length. It was not possible to determine S3 behavior in the T3Z2 condition because the shoulder marker detached and was missing throughout the entire block. Subject color coding as in Figures 2 and 3.
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pone-0031770-g004: Interception point along the ball trajectory.(A) Left panel: schematic representation of the interception point index (computed as the ratio between the BC and AB ball trajectory arc lengths, see Methods). Right panel: for each flight time condition (T1–T3), subjects impact point along ball trajectory (normalized with respect to subject arm length) was uniquely determined by the movement time, hence the value of the difference between the extrapolated time of arrival of the ball at the frontal plane (tC) and the impact time (tB). However, for different flight times, subjects are free to vary tB and impact the ball at the same normalized distance (vertical line labeled “const distance”) or to catch the ball closer to their shoulder (horizontal line labeled “const time”). (B) Scatter plots of the interception index vs. tC−tB (mean ± SE across trials in the same conditions; SE are reported only when number of trials per block was larger than 2). A value of I = 0 indicates a catch at C while I = 1 indicates a catch in correspondence of the first possible interception point (A point), computed as the interception between the ball trajectory and the sphere centered at the shoulder joint of radius equal to arm length. It was not possible to determine S3 behavior in the T3Z2 condition because the shoulder marker detached and was missing throughout the entire block. Subject color coding as in Figures 2 and 3.

Mentions: Tc = time of arrival at the frontal plane passing for subject shoulder at launch time; TB = impact time (see Figure 4).


Catching a ball at the right time and place: individual factors matter.

Cesqui B, d'Avella A, Portone A, Lacquaniti F - PLoS ONE (2012)

Interception point along the ball trajectory.(A) Left panel: schematic representation of the interception point index (computed as the ratio between the BC and AB ball trajectory arc lengths, see Methods). Right panel: for each flight time condition (T1–T3), subjects impact point along ball trajectory (normalized with respect to subject arm length) was uniquely determined by the movement time, hence the value of the difference between the extrapolated time of arrival of the ball at the frontal plane (tC) and the impact time (tB). However, for different flight times, subjects are free to vary tB and impact the ball at the same normalized distance (vertical line labeled “const distance”) or to catch the ball closer to their shoulder (horizontal line labeled “const time”). (B) Scatter plots of the interception index vs. tC−tB (mean ± SE across trials in the same conditions; SE are reported only when number of trials per block was larger than 2). A value of I = 0 indicates a catch at C while I = 1 indicates a catch in correspondence of the first possible interception point (A point), computed as the interception between the ball trajectory and the sphere centered at the shoulder joint of radius equal to arm length. It was not possible to determine S3 behavior in the T3Z2 condition because the shoulder marker detached and was missing throughout the entire block. Subject color coding as in Figures 2 and 3.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3285177&req=5

pone-0031770-g004: Interception point along the ball trajectory.(A) Left panel: schematic representation of the interception point index (computed as the ratio between the BC and AB ball trajectory arc lengths, see Methods). Right panel: for each flight time condition (T1–T3), subjects impact point along ball trajectory (normalized with respect to subject arm length) was uniquely determined by the movement time, hence the value of the difference between the extrapolated time of arrival of the ball at the frontal plane (tC) and the impact time (tB). However, for different flight times, subjects are free to vary tB and impact the ball at the same normalized distance (vertical line labeled “const distance”) or to catch the ball closer to their shoulder (horizontal line labeled “const time”). (B) Scatter plots of the interception index vs. tC−tB (mean ± SE across trials in the same conditions; SE are reported only when number of trials per block was larger than 2). A value of I = 0 indicates a catch at C while I = 1 indicates a catch in correspondence of the first possible interception point (A point), computed as the interception between the ball trajectory and the sphere centered at the shoulder joint of radius equal to arm length. It was not possible to determine S3 behavior in the T3Z2 condition because the shoulder marker detached and was missing throughout the entire block. Subject color coding as in Figures 2 and 3.
Mentions: Tc = time of arrival at the frontal plane passing for subject shoulder at launch time; TB = impact time (see Figure 4).

Bottom Line: Inter-individual variability was observed in several kinematic parameters, such as wrist trajectory, wrist velocity profile, timing and spatial distribution of the impact point, upper limb posture, trunk motion, and submovement decomposition.Individual idiosyncratic behaviors were consistent across different ball flight time conditions and across two experimental sessions carried out at one year distance.These results highlight the importance of a systematic characterization of individual factors in the study of interceptive tasks.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Neuromotor Physiology, IRCCS Santa Lucia Foundation, Rome, Italy.

ABSTRACT
Intercepting a moving object requires accurate spatio-temporal control. Several studies have investigated how the CNS copes with such a challenging task, focusing on the nature of the information used to extract target motion parameters and on the identification of general control strategies. In the present study we provide evidence that the right time and place of the collision is not univocally specified by the CNS for a given target motion; instead, different but equally successful solutions can be adopted by different subjects when task constraints are loose. We characterized arm kinematics of fourteen subjects and performed a detailed analysis on a subset of six subjects who showed comparable success rates when asked to catch a flying ball in three dimensional space. Balls were projected by an actuated launching apparatus in order to obtain different arrival flight time and height conditions. Inter-individual variability was observed in several kinematic parameters, such as wrist trajectory, wrist velocity profile, timing and spatial distribution of the impact point, upper limb posture, trunk motion, and submovement decomposition. Individual idiosyncratic behaviors were consistent across different ball flight time conditions and across two experimental sessions carried out at one year distance. These results highlight the importance of a systematic characterization of individual factors in the study of interceptive tasks.

Show MeSH
Related in: MedlinePlus