Attentional influences on the performance of secondary physical tasks during posture control

Influence of cognitive demand and auditory noise on postural dynamics

The control of human balance involves an interaction between the human motor, cognitive, and sensory systems. The dynamics of this interaction are yet to be fully understood, however, work has shown the performance of cognitive tasks to have a hampering effect on motor performance, while additive sensory noise to have a beneficial effect. The current study aims to examine whether postural control will be impacted by a concurrent working memory task, and similarly, if additive noise can counteract the expected negative influence of the added cognitive demand. Postural sway of healthy young adults was collected during the performance of a modified N-back task with varying difficulty, in the presence and absence of auditory noise. Our results show a reduction in postural stability scaled to the difficulty of the cognitive task, but this effect is less prominent in the presence of additive noise. Additionally, by separating postural sway into different frequency bands, typically used to assess the exploratory vs feedback-driven stabilizing dynamics of sway, we found a differential effect between the cognitive task and additive noise, thus demonstrating that both frequency regimes of postural sway are sensitive to high cognitive load and increased sensory information.

Selective engagement of long-latency reflexes in postural control through wobble board training

Long-latency reflexes (LLRs) are critical precursors to intricate postural coordination of muscular adaptations that sustain equilibrium following abrupt disturbances. Both disturbances and adaptive responses reflect excursions of postural control from quiescent Gaussian stability under a narrow bell curve, excursions beyond Gaussianity unfolding at many timescales. LLRs slow with age, accentuating the risk of falls and undermining dexterity, particularly in settings with concurrent additional tasks. We investigated whether the wobble board could cultivate the engagement of LLRs selectively in healthy young participants executing a suprapostural Trail Making Task (TMT). A concurrent additional-task demand constituted visual precision predominantly along the anteroposterior (AP) axis and mechanical instability mainly along the mediolateral (ML) axis. We scrutinized planar center-of-pressure (CoP) trajectories to quantify postural non-Gaussianity across various temporal scales. Wobble board increased engagement of LLRs and decreased engagement of compensatory postural adjustments (CPAs), indicated by the peak in non-Gaussianity of CoP planar displacements over LLR-specific timescales (50-100 ms) and non-Gaussianity of CoP planar displacements progressively diminishing over CPA-specific timescales ([Formula: see text] ms). Engagement with TMT did not show any noticeable influence on non-Gaussian postural sway patterns. Despite aligning the unstable axis of the wobble board with participants' ML axis, thus rendering posture more unstable along the ML axis, the wobble board increased engagement of LLRs significantly more along the AP axis and reduced engagement of CPAs significantly more along the ML axis. These findings offer initial mechanistic insights into how wobble boards may bolster balance and potentially reduce the occurrence of falls by catalyzing the engagement of LLRs selectively.

Effects of Different Auditory Stimuli and Cognitive Tasks on Balance in Healthy Young Adults

INTRODUCTION

This study investigated the effect of different auditory stimuli and cognitive tasks on balance in healthy young adults.

METHODS

Thirty-three participants, aged 23.33 ± 2.43 years, were included in the study. The hearing levels of the participants were determined. Static and dynamic postural stability and limits of stability (LOS) tests were performed in the absence of auditory stimuli, in the presence of spondee word lists at 70 dB(A) and in the presence of spondee+white noise (-6 dB signal-to-noise ratio [SNR]), while auditory stimuli were presented bilaterally with supra-aural headphones. Participants were asked to repeat the words they listened to while performing balance-related tasks.

RESULTS

No significant differences between the three conditions were observed in the postural stability and LOS results. Increase in total repetition error was observed as the listening task became more difficult.

CONCLUSION

The presence of auditory stimuli and the cognitive tasks did not cause any changes in the participants' balance.

Effects of auditory noise intensity and color on the dynamics of upright stance

Previous work assessing the effect of additive noise on the postural control system has found a positive effect of additive white noise on postural dynamics. This study covers two separate experiments that were run sequentially to better understand how the structure of the additive noise signal affects postural dynamics, while also furthering our knowledge of how the intensity of auditory stimulation of noise may elicit this phenomenon. Across the two experiments, we introduced three auditory noise stimulations of varying structure (white, pink, and brown noise). Experiment 1 presented the stimuli at 35 dB while Experiment 2 was presented at 75 dB. Our findings demonstrate a decrease in variability of the postural control system regardless of the structure of the noise signal presented, but only for high intensity auditory stimulation.

Spatial variability and directional shifts in postural control in Parkinson's disease

Individuals with Parkinson's disease exhibit tremors, rigidity, and bradykinesia, disrupting normal movement variability and resulting in postural instability. This comprehensive study aimed to investigate the link between the temporal structure of postural sway variability and Parkinsonism by analyzing multiple datasets from young and older adults, including individuals with Parkinson's disease, across various task conditions. We used the Oriented Fractal Scaling Component Analysis (OFSCA), which identifies minimal and maximal long-range correlations within the center of pressure time series, allowing for detecting directional changes in postural sway variability. The objective was to uncover the primary directions along which individuals exerted control during the posture. The results, as anticipated, revealed that healthy adults predominantly exerted control along two orthogonal directions, closely aligned with the anteroposterior (AP) and mediolateral (ML) axes. In stark contrast, older adults and individuals with Parkinson's disease exhibited control along suborthogonal directions that notably diverged from the AP and ML axes. While older adults and those with Parkinson's disease demonstrated a similar reduction in the angle between these two control directions compared to healthy older adults, their reliance on this suborthogonal angle concerning endogenous fractal correlations exhibited significant differences from the healthy aging cohort. Importantly, individuals with Parkinson's disease did not manifest the sensitivity to destabilizing task settings observed in their healthy counterparts, affirming the distinction between Parkinson's disease and healthy aging.

Focus of Attention in Voice Training

OBJECTIVE

The vast majority of motor learning studies investigating focus of attention have found that an external focus of attention (focusing on the effect of a movement) results in enhanced performance and learning, compared to an internal focus of attention (focusing on the body movement itself). The present study attempts to determine if the high incidence of internal focus of attention instruction that has been reported in the realm of athletics is replicated in voice training.

METHODS

Two hundred and seventy-eight singers, who were at least 18 years old and taking voice lessons, were recruited to participate in an anonymous research survey entitled "Instructions given to singers in voice lessons." The main six questions asked singers to report phrases or instructions that their studio voice teachers gave them in regard to posture, breathing and/or support, tone clarity and/or onset of tone, space and/or resonance, articulation, and reducing tension.

RESULTS

Approximately 50.83% of the total responses were classified as inducing an external focus, 39.42% were classified as internal focus, 6.48% used a combination of both internal and external focus, and 3.27% were categorized as miscellaneous.

CONCLUSIONS

The results of this study indicate that voice teachers use both external and internal attentional focus directives in the voice studio. Given the robust body of literature supporting the use of external focus, it is noteworthy that the current study found that external focus is used more often than internal focus in voice training.

The effect of educational gymnastics on postural control of young children

Fundamental movement skill (FMS) proficiency does not develop solely due to maturation, but also via diverse perceptual-motor experiences across childhood. Practicing gymnastics has been shown to improve postural control. The purpose of the present study was to examine potential changes to postural control of children following a course of educational gymnastics. Two groups of children both completed 20 × 45-min physical education (PE) lessons; one group (n = 43, age = 6.4 ± 0.7, 56% male) completed educational gymnastics lessons in school delivered by a professional coach, the other group completed their typical PE classes (n = 18, age = 6.5 ± 0.3, 33% male). Unipedal balancing performance was assessed by calculating the percentage of successful trials made. Postural sway dynamics were explored by calculating center-of-pressure sample entropy, 95% ellipse sway area and sway velocity. Measurements were taken before the lessons began and immediately after the lessons were completed. The gymnastics group performed better than the typical PE group at unipedal balancing. Females outperformed males in both groups. Males made different changes to postural control (i.e., increased sway regularity and improved stability) compared to females across 3 months. Educational gymnastics enabled children in a critical period of development to make more rapid improvements to postural performance and control. Novel movement experiences, like those offered by educational gymnastics, may have a positive influence on postural control and importantly, physical literacy. Future work should examine how sex effects the development of postural control strategies in young children.

Dominance of Attention Focus and Its Electroencephalogram Activity in Standing Postural Control in Healthy Young Adults

Attention focus changes performance, and external focus (EF) improves performance compared to internal focus (IF). However, recently, the dominance of attention focus, rather than the effectiveness of unilateral EF, has been examined. Although the positive effects of EF on standing postural control have been reported, the dominance of attention focus has not yet been examined. Therefore, the purpose of this study was to examine the dominance of attention focus and its neural mechanism in standing postural control using electroencephalography (EEG). A standing postural control task under IF and EF conditions was performed on healthy young men. Gravity center sway and cortical activity simultaneously using a stabilometer and an EEG were measured. Participants were classified into IF-dominant and EF-dominant groups according to their index of postural stability. The EEG was analyzed, and cortical activity in the theta-wave band was compared between the IF-dominant and EF-dominant groups. Significant neural activity was observed in the left parietal lobe of the IF-dominant group in the IF condition, and in the left frontal lobe of the EF-dominant group in the EF condition (p < 0.05). Differences in EEG activity between IF-dominant and EF-dominant groups, in standing postural control, were detected. This contributes to the development of training methods that consider attentional focus dominance in postural control.

Influence of age on postural control during dual task: a centre of pressure motion and electromyographic analysis

BACKGROUND

Dual task influences postural control. A cognitive task seems to reduce muscle excitation during a postural balance, especially in older adults (OA).

AIM

The aim of this study is to evaluate the effect of three cognitive tasks on muscle excitation and static postural control in OA and young adults (YA) in an upright posture maintenance task.

METHODS

31 YA and 30 OA were evaluated while performing a modified Romberg Test in five different conditions over a force plate: open eyes, closed eyes, spatial-memory brooks' test, counting backwards aloud test and mental arithmetic task. The surface electromyographic signals of Tibialis anterior (TA), Lateral Gastrocnemius (GL), Peroneus Longus (PL), and Erector Spinae (ES) was acquired with an 8-channel surface electromyographic system. The following variables were computed for both the electromyographic analysis and the posturographic assessment: Root mean square (RMS), centre of pressure (CoP) excursion (Path) and velocity, sway area, RMS of the CoP Path and 50%, 95% of the power frequency. Mixed ANOVA was used to detect differences with group membership as factor between and type of task as within. The analysis was performed on the differences between each condition from OE.

RESULTS

An interaction effect was found for Log (logarithmic) Sway Area. A main effect for task emerged on all posturographic variables except Log 95% frequencies and for Log PL and ES RMS. A main effect for group was never detected.

DISCUSSION AND CONCLUSION

This study indicates a facilitating effect of mental secondary task on posturographic variables. Non-silent secondary task causes increase in ES and TA muscle activation and a worsening in static postural control performance.

Implications of Optimal Feedback Control Theory for Sport Coaching and Motor Learning: A Systematic Review

Best practice in skill acquisition has been informed by motor control theories. The main aim of this study is to screen existing literature on a relatively novel theory, Optimal Feedback Control Theory (OFCT), and to assess how OFCT concepts can be applied in sports and motor learning research. Based on 51 included studies with on average a high methodological quality, we found that different types of training seem to appeal to different control processes within OFCT. The minimum intervention principle (founded in OFCT) was used in many of the reviewed studies, and further investigation might lead to further improvements in sport skill acquisition. However, considering the homogenous nature of the tasks included in the reviewed studies, these ideas and their generalizability should be tested in future studies.

The effects of pain and a secondary task on postural sway during standing

BACKGROUND

Pain impairs available cognitive resources and somatosensory information, but its effects on postural control during standing are inconclusive. The aim of this study was to investigate whether postural sway is affected by the presence of pain and a secondary task during standing.

METHODS

Sixteen healthy subjects stood as quiet as possible at a tandem stance for 30s on a force platform at different conditions regarding the presence of pain and a secondary task. Subjects received painful stimulations on the right upper arm or lower leg according to a relative pain threshold [pain 7 out 10 on a Visual Analog Scale (VAS) - 0 representing "no pain" and 10 "worst pain imaginable"] using a computer pressurized cuff. The secondary task consisted of pointing to a target using a head-mounted laser-pointer as visual feedback. Center of Pressure (COP) sway area, velocity, mean frequency and sample entropy were calculated from force platform measures.

FINDINGS

Compared to no painful condition, pain intensity (leg: VAS = 7; arm VAS = 7.4) increased following cuff pressure conditions (P < .01). Pain at the leg decreased COP area (P < .05), increased COP velocity (P < .05), mean frequency (P < .05) and sample entropy (P < .05) compared with baseline condition regardless the completion of the secondary task. During condition with pain at the leg, completion of the secondary task reduced COP velocity (P < .001) compared with condition without secondary task.

INTERPRETATION

Pain in the arm did not affect postural sway. Rather, postural adaptations seem dependent on the location of pain as pain in the lower leg affected postural sway. The completion of a secondary task affected postural sway measurements and reduced the effect of leg pain on postural sway. Future treatment interventions could benefit from dual-task paradigm during balance training aiming to improve postural control in patients suffering from chronic pain.

Tracking differential activation of primary and supplementary motor cortex across timing tasks: An fNIRS validation study

Functional near-infrared spectroscopy (fNIRS) provides an alternative to functional magnetic resonance imaging (fMRI) for assessing changes in cortical hemodynamics. To establish the utility of fNIRS for measuring differential recruitment of the motor network during the production of timing-based actions, we measured cortical hemodynamic responses in 10 healthy adults while they performed two versions of a finger-tapping task. The task, used in an earlier fMRI study (Jantzen et al., 2004), was designed to track the neural basis of different timing behaviors. Participants paced their tapping to a metronomic tone, then continued tapping at the established pace without the tone. Initial tapping was either synchronous or syncopated relative to the tone. This produced a 2 × 2 design: synchronous or syncopated tapping and pacing the tapping with or continuing without a tone. Accuracy of the timing of tapping was tracked while cortical hemodynamics were monitored using fNIRS. Hemodynamic responses were computed by canonical statistical analysis across trials in each of the four conditions. Task-induced brain activation resulted in significant increases in oxygenated hemoglobin concentration (oxy-Hb) in a broad region in and around the motor cortex. Overall, syncopated tapping was harder behaviorally and produced more cortical activation than synchronous tapping. Thus, we observed significant changes in oxy-Hb in direct relation to the complexity of the task.

State-space intermittent feedback stabilization of a dual balancing task

Balancing the body in upright standing and balancing a stick on the fingertip are two examples of unstable tasks that, in spite of strong motor and sensory differences, appear to share a similar motor control paradigm, namely a state-space intermittent feedback stabilization mechanism. In this study subjects were required to perform the two tasks simultaneously, with the purpose of highlighting both the coordination between the two skills and the underlying interaction between the corresponding controllers. The experimental results reveal, in particular, that upright standing (the less critical task) is modified in an adaptive way, in order to facilitate the more critical task (stick balancing), but keeping the overall spatio-temporal signature well known in regular upright standing. We were then faced with the following question: to which extent the physical/biomechanical interaction between the two independent intermittent controllers is capable to explain the dual task coordination patterns, without the need to introduce an additional, supervisory layer/module? By comparing the experimental data with the output of a simulation study we support the former hypothesis, suggesting that it is made possible by the intrinsic robustness of both state-space intermittent feedback stabilization mechanisms.

Are attentional instruction and feedback type affect on learning of postural and supra-postural tasks?

Optimum postural control and balance is dependent on the individual, the environment, and the task limitations. Thus, the present study investigated the effect of attentional instruction and feedback type on postural and supra-postural tasks. The 96 participants aged 11-19 years with attention deficit hyperactivity disorder (ADHD) were randomly assigned to one of the eight groups such as attentional instruction (internal and external), feedback (external and internal), and task (postural and supra-postural). Following a pre-test, the participants underwent four training sessions. Each session included 20 trials of 30 s with 20 s of rest between trials. Twenty-four hours after the training session, they performed two trials of warm-up and then took part in a retention test. Twenty-four hours after the retention test, they again performed two trials of warm-up and then participated in the transfer test. The result showed that the external attentional feedback and external attentional instruction groups performed better on supra-postural and postural tasks than the other experimental groups (P > 0.05). The external attentional instruction group performed better on postural and supra-postural tasks in the delayed retention and transfer tests (P > 0.05). Also, the external feedback group scored highest on postural and supra-postural tasks in the delayed retention and transfer tests. The results suggest that external attentional feedback and instruction is more effective than internal attention when learning supra-postural tasks to maintain balance.

Motor Behavior Concepts in the Study of Balance: A Scoping Review

Previous research suggests that using Fitts' law; attentional focus or challenge point framework (CPF) is beneficial in balance control studies. A scoping review was conducted to examine studies that utilized these motor behavior concepts during balance control tasks. An extensive literature search was performed up to January 2018. Two independent reviewers conducted a study selection process followed by data extraction of the search results. Forty-six studies were identified, with 2 studies related to CPF, 12 studies related to Fitts' law and 32 studies related to focus of attention. The CPF appears to be a useful method for designing a progressive therapeutic program. Fitts' law can be used as a tool for controlling the difficulty of motor tasks. Focus of attention studies indicate that adopting an external focus of attention improves task performance. Overall, studies included in this review report benefit when using the selected motor behavior concepts. However, the majority (>80%) of studies included in the review involved healthy populations, with only three clinical trials. In order to ascertain the benefits of the selected motor behavior concepts in clinical settings, future research should focus on using these concepts for clinical trials to examine balance control among people with balance impairments.

Effects of external focus of attention on balance: a short review

[Purpose] The present study reviewed studies that examined the effects of attentional focus on balance. [Methods] Keywords such as “attentional”, “focus”, and “balance” were used to find relevant research papers in PubMed (www.ncbi.nlm.nih.gov/pubmed). Forty-five papers were found, and 18 of them were used for this study, excluding review papers and papers irrelevant to the topic of this study. [Results] Among the papers used for the review, the number of papers in which external focus produced effective outcomes was 15 (83.3%). The number of papers in which both external and internal focus produced effective outcomes was 2 (11.1%). The number of paper in which no instruction about attentional focus was effective was 1 (5.5%), and the number of papers in which internal focus was effective was zero. [Conclusion] This short review suggests clinical implications about how physical therapists can use attentional focus for balance rehabilitation of patients. Instructions about external focus of attention can generally be useful as a method to improve posture and balance control. Furthermore, the present reviews indicates that external focus of attention would be more useful in a rehabilitation stage in which the difficulty level of balance performance is gradually increased.

Building a framework for a dual task taxonomy

The study of dual task interference has gained increasing attention in the literature for the past 35 years, with six MEDLINE citations in 1979 growing to 351 citations indexed in 2014 and a peak of 454 cited papers in 2013. Increasingly, researchers are examining dual task cost in individuals with pathology, including those with neurodegenerative diseases. While the influence of these papers has extended from the laboratory to the clinic, the field has evolved without clear definitions of commonly used terms and with extreme variations in experimental procedures. As a result, it is difficult to examine the interference literature as a single body of work. In this paper we present a new taxonomy for classifying cognitive-motor and motor-motor interference within the study of dual task behaviors that connects traditional concepts of learning and principles of motor control with current issues of multitasking analysis. As a first step in the process we provide an operational definition of dual task, distinguishing it from a complex single task. We present this new taxonomy, inclusive of both cognitive and motor modalities, as a working model; one that we hope will generate discussion and create a framework from which one can view previous studies and develop questions of interest.

Influence of age on postural sway during different dual-task conditions

Dual-task performance assessments of competing parallel tasks and postural outcomes are growing in importance for geriatricians, as it is associated with predicting fall risk in older adults. This study aims to evaluate the postural stability during different dual-task conditions including visual (SMBT), verbal (CBAT) and cognitive (MAT) tasks in comparison with the standard Romberg's open eyes position (OE). Furthermore, these conditions were investigated in a sample of young adults and a group of older healthy subjects to examine a potential interaction between type of secondary task and age status. To compare these groups across the four conditions, a within-between mixed model ANOVA was applied. Thus, a stabilometric platform has been used to measure center of pressure velocity (CoPV), sway area (SA), antero-posterior (AP) and medio-lateral (ML) oscillations as extents of postural sway. Tests of within-subjects effects indicated that different four conditions influenced the static balance for CoPV (p < 0.001), SA (p < 0.001). Post-hoc analyses indicated that CBAT task induced the worst balance condition on CoPV and resulted in significantly worse scores than OE (-11.4%; p < 0.05), SMBT (-17.8%; p < 0.01) and MAT (-17.8%; p < 0.01) conditions; the largest SA was found in OE, and it was statistically larger than SMBT (-27.0%; p < 0.01) and MAT (-23.1%; p < 0.01). The between-subjects analysis indicated a general lower balance control in the group of elderly subjects (CoPV p < 0.001, SA p < 0.002), while, the mixed model ANOVA did not detect any interaction effect between types of secondary task and groups in any parameters (CoPV p = 0.154, SA p = 0.125). Postural sway during dual-task assessments was also found to decrease with advancing age, however, no interactions between aging and types of secondary tasks were found. Overall, these results indicated that the secondary task which most influenced the length of sway path, as measured by postural stability was a simple verbal assignment.

Effect of attentional interference on balance recovery in older adults

Since most working memory (WM) tasks used in dual-task (DT) postural paradigms include both storage and processing of information, it is difficult to determine the extent to which each of these contributes to interference with balance control. In the current study, a change-detection task (changes in colored squares between two presentation events) that estimates visual working memory capacity (VWMC) was paired with tasks of increasing postural demand (stance, perturbation) in young adults (YAs) and older adults (OAs) and performance compared between the two postural conditions and across the two populations. The change-detection task was selected as it requires storage of information without updating or manipulation; 34 YAs, 34 OAs, and five frail OAs were recruited. A significant reduction in VWMC occurred with increasing postural demand during the perturbation condition for both YAs (p < 0.01) and OAs (p < 0.001). VWMC was also significantly lower for OAs than YAs in the control condition (1.8 ± 0.7 vs. 2.8 ± 0.6) (p < 0.001). OAs showed a significant increase in the number of trials in which steps or rise to toes occurred during recovery between single-task (ST) and DT (p < 0.05; p < 0.05). OAs also showed a significant increase in normalized tibialis anterior amplitude (p < 0.001) following perturbations. YAs showed an increase in normalized area under the center of pressure trajectory and in AP forces (nAcopx1: p < 0.001; nFap1: p < 0.05) during the DT condition.

An External Skill Focus is Necessary to Enhance Performance

This study examined the interaction between a skill/extraneous attentional focus and an internal/external focus of attention using a dual-task paradigm. Thirty-two low-skill participants completed a primary dart-throwing task with their dominant arm while simultaneously performing a secondary arm-stabilizing task with their nondominant arm. Two aspects of the participants’ attentional focus were manipulated: skill versus extraneous focus and external versus internal focus. Participants completed 120 trials across four conditions created by combining the dimensions of the two variables. Performance on the primary task was assessed by measuring throwing accuracy and the kinematics of the throwing action. Results indicated that accuracy improved under the external, skill-oriented condition relative to all other conditions; no differences between the remaining conditions were observed. These findings suggest that an external, skill-oriented focus of attention is needed to facilitate performance improvements in novices.

Visual reliance for balance control in older adults persists when visual information is disrupted by artificial feedback delays

Sensory information from our eyes, skin and muscles helps guide and correct balance. Less appreciated, however, is that delays in the transmission of sensory information between our eyes, limbs and central nervous system can exceed several 10s of milliseconds. Investigating how these time-delayed sensory signals influence balance control is central to understanding the postural system. Here, we investigate how delayed visual feedback and cognitive performance influence postural control in healthy young and older adults. The task required that participants position their center of pressure (COP) in a fixed target as accurately as possible without visual feedback about their COP location (eyes-open balance), or with artificial time delays imposed on visual COP feedback. On selected trials, the participants also performed a silent arithmetic task (cognitive dual task). We separated COP time series into distinct frequency components using low and high-pass filtering routines. Visual feedback delays affected low frequency postural corrections in young and older adults, with larger increases in postural sway noted for the group of older adults. In comparison, cognitive performance reduced the variability of rapid center of pressure displacements in young adults, but did not alter postural sway in the group of older adults. Our results demonstrate that older adults prioritize vision to control posture. This visual reliance persists even when feedback about the task is delayed by several hundreds of milliseconds.

Learning a stick-balancing task involves task-specific coupling between posture and hand displacements

Theories of motor learning argue that the acquisition of novel motor skills requires a task-specific organization of sensory and motor subsystems. We examined task-specific coupling between motor subsystems as subjects learned a novel stick-balancing task. We focused on learning-induced changes in finger movements and body sway and investigated the effect of practice on their coupling. Eight subjects practiced balancing a cylindrical wooden stick for 30 min a day during a 20 day learning period. Finger movements and center of pressure trajectories were recorded in every fifth practice session (4 in total) using a ten camera VICON motion capture system interfaced with two force platforms. Motor learning was quantified using average balancing trial lengths, which increased with practice and confirmed that subjects learned the task. Nonlinear time series and phase space reconstruction methods were subsequently used to investigate changes in the spatiotemporal properties of finger movements, body sway and their progressive coupling. Systematic increases in subsystem coupling were observed despite reduced autocorrelation and differences in the temporal properties of center of pressure and finger trajectories. The average duration of these coupled trajectories increased systematically across the learning period. In short, the abrupt transition between coupled and decoupled subsystem dynamics suggested that stick balancing is regulated by a hierarchical control mechanism that switches from collective to independent control of the finger and center of pressure. In addition to traditional measures of motor performance, dynamical analyses revealed changes in motor subsystem organization that occurred when subjects learned a novel stick-balancing task.