Classification of accurate and misarticulated /ɑr/ for ultrasound biofeedback using tongue part displacement trajectories.

Ultrasound biofeedback therapy (UBT), which incorporates real-time imaging of tongue articulation, has demonstrated generally positive speech remediation outcomes for individuals with residual speech sound disorder (RSSD). However, UBT requires high attentional demands and may therefore benefit from a simplified display of articulation targets that are easily interpretable and can be compared to real-time articulation. Identifying such targets requires automatic quantification and analysis of movement features relevant to accurate speech production. Our image-analysis program TonguePART automatically quantifies tongue movement as tongue part displacement trajectories from midsagittal ultrasound videos of the tongue, with real-time capability. The present study uses such displacement trajectories to compare accurate and misarticulated American-English rhotic /ɑr/ productions from 40 children, with degree of accuracy determined by auditory perceptual ratings. To identify relevant features of accurate articulation, support vector machine (SVM) classifiers were trained and evaluated on several candidate data representations. Classification accuracy was up to 85%, indicating that quantification of tongue part displacement trajectories captured tongue articulation characteristics that distinguish accurate from misarticulated production of /ɑr/. Regression models for perceptual ratings were also compared. The simplest data representation that retained high predictive ability, demonstrated by high classification accuracy and strong correlation between observed and predicted ratings, was displacements at the midpoint of /r/ relative to /ɑ/ for the tongue dorsum and blade. This indicates that movements of the dorsum and blade are especially relevant to accurate production of /r/, suggesting that a predictive parameter and biofeedback target based on this data representation may be usable for simplified UBT.

Movement Regularity Differentiates Specialized and Nonspecialized Athletes in a Virtual Reality Soccer Header Task.

BACKGROUND: Young athletes who specialize early in a single sport may subsequently be at increased risk of injury. While heightened injury risk has been theorized to be related to volume or length of exposure to a single sport, the development of unhealthy, homogenous movement patterns, and rigid neuromuscular control strategies may also be indicted. Unfortunately, traditional laboratory assessments have limited capability to expose such deficits due to the simplistic and constrained nature of laboratory measurement techniques and analyses. METHODS: To overcome limitations of prior studies, the authors proposed a soccer-specific virtual reality header assessment to characterize the generalized movement regularity of 44 young female athletes relative to their degree of sport specialization (high vs low). Participants also completed a traditional drop vertical jump assessment. RESULTS: During the virtual reality header assessment, significant differences in center of gravity sample entropy (a measure of movement regularity) were present between specialized (center of gravity sample entropy: mean = 0.08, SD = 0.02) and nonspecialized center of gravity sample entropy: mean = 0.10, SD = 0.03) groups. Specifically, specialized athletes exhibited more regular movement patterns during the soccer header than the nonspecialized athletes. However, no significant between-group differences were observed when comparing participants' center of gravity time series data from the drop vertical jump assessment. CONCLUSIONS: This pattern of altered movement strategy indicates that realistic, sport-specific virtual reality assessments may be uniquely beneficial in exposing overly rigid movement patterns of individuals who engage in repeated sport specialized practice.

Grip force anticipation of nonlinear, underactuated load force.

Feedforward internal model-based control enabled by efference copies of motor commands is the prevailing theoretical account of motor anticipation. Grip force control during object manipulation-a paradigmatic example of motor anticipation-is a key line of evidence for that account. However, the internal model approach has not addressed the computational challenges faced by the act of manipulating mechanically complex objects with nonlinear, underactuated degrees of freedom. These objects exhibit complex and unpredictable load force dynamics which cannot be encoded by efference copies of underlying motor commands, leading to the prediction from the perspective of an efference copy-enabled feedforward control scheme that grip force should either lag or fail to coordinate with changes in load force. In contrast to that prediction, we found evidence for strong, precise, anticipatory grip force control during manipulations of a complex object. The results are therefore inconsistent with the internal forward model approach and suggest that efference copies of motor commands are not necessary to enable anticipatory control during active object manipulation.NEW & NOTEWORTHY From the perspective of feedforward internal model-based control, precise, anticipatory grip force (GF) control when manipulating a complex object should not be possible as the object's changing load forces (LFs) cannot be encoded by efference copies of the underlying movements. However, we observed that GF exhibited strong, precise, anticipatory coupling with LF during extended manipulations of a complex object. These findings suggest that an alternative theoretical framework is needed to account for anticipatory GF control.

A Technical Report on the Development of a Real-Time Visual Biofeedback System to Optimize Motor Learning and Movement Deficit Correction.

This technical report describes the design and implementation of a novel biofeedback system to reduce biomechanical risk factors associated with anterior cruciate ligament (ACL) injuries. The system provided objective real-time biofeedback driven by biomechanical variables associated with increased ACL injury risk without the need of a present expert. Eleven adolescent female athletes (age = 16.7 ± 1.34 yrs; height = 1.70 ± 0.05 m; weight = 62.20 ± 5.63 kg) from the same varsity high school volleyball team were enrolled in the experiment. Participants first completed 10 bodyweight squats in the absence of the biofeedback (pretest), 40 bodyweight squats while interacting with the biofeedback, and a final 10 bodyweight squats in the absence of the biofeedback (posttest). Participants also completed three pretest drop vertical jumps and three posttest drop vertical jumps. Results revealed significant improvements in squat performance, as quantified by a novel heat map analysis, from the pretest to the posttest. Additionally, participants displayed improvements in landing mechanics during the drop vertical jump. This study demonstrates that participants were able to interact effectively with the real-time biofeedback and that biomechanical improvements observed during squatting translated to a separate task.

Flexible organization of grip force control during movement frequency scaling.

The grip force applied to maintain grasp of a handheld object has been typically reported as tightly coupled to the load force exerted by the object as it is actively manipulated, occurring proportionally and consistently in phase with changes in load force. However, continuous grip force-load force coupling breaks down when overall load force levels and oscillation amplitudes are lower (Grover F, Lamb M, Bonnette S, Silva PL, Lorenz T, Riley MA. Exp Brain Res 236: 2531-2544, 2018) or more predictable (Grover FM, Nalepka P, Silva PL, Lorenz T, Riley MA. Exp Brain Res 237: 687-703, 2019). Under these circumstances, grip force is instead only intermittently coupled to load force; continuous coupling is prompted only when load force levels or variations become sufficiently high or unpredictable. The current study investigated the nature of the transition between continuous and intermittent modes of grip force control by scaling the load force level and the oscillation amplitude continuously in time by means of scaling the required frequency of movement oscillations. Participants grasped a cylindrical object between the thumb and forefinger and oscillated their arm about the shoulder in the sagittal plane. Oscillation frequencies were paced with a metronome that scaled through an ascending or descending frequency progression. Due to greater accelerations, faster frequencies produced greater overall load force levels and more pronounced load oscillations. We observed smooth but nonlinear transitions between clear regimes of intermittent and continuous grip force-load force coordination, for both scaling directions, indicating that grip force control can flexibly reorganize as parameters affecting grasp (e.g., variations in load force) change over time.NEW & NOTEWORTHY Grip force (GF) is synchronously coupled to changing load forces (LF) during object manipulation when LF levels are high or unpredictable, but only intermittently coupled to LF during less challenging grasp conditions. This study characterized the nature of transitions between synchronous and intermittent GF-LF coupling, revealing a smooth but nonlinear change in intermittent GF modulation in response to continuous scaling of LF amplitude. Intermittent, "drift-and-act" control may provide an alternative framework for understanding GF-LF coupling.

Variable and intermittent grip force control in response to differing load force dynamics.

A recent study (Grover et al. Exp Brain Res 236(10):2531-2544, 2018) found that the grip force applied to maintain grasp of a hand-held object exhibited intermittent coupling to the changing load forces exerted by the object as it was oscillated. In particular, the strength and consistency of grip force response to load force oscillations was tied to overall load force levels and the prominence of load force oscillations. This contrasts with previous reports of grip force-load force coupling as generally continuous and stable and, therefore, has implications for theoretical accounts of grip force control that are predicated on these prior understandings of the coupling. The finding of intermittency additionally raises questions about the consistency of the temporal relation (i.e., lead/lag) between grip force and load force over time. The objective of the current study was, therefore, to investigate how the time-varying pattern (i.e., the regularity vs. complexity) of load force variations contribute to shifts between more intermittent and more continuous grip force control, and to determine the temporal consistency of the coupling. It was found that grip force became more tightly and continuously responsive to load force as load force changes became less predictable. Additionally, we report strong evidence that the temporal (i.e., lead/lag) relation between grip force and load force and the strength of their coupling vary substantially over time.

'What's my risk of sustaining an ACL injury while playing football (soccer)?' A systematic review with meta-analysis.

OBJECTIVE: To estimate the incidence proportion (IP) and incidence rate (IR) of ACL injury in football players. DESIGN: Systematic review with meta-analysis. DATA SOURCES: PubMed, CINAHL and SPORTDiscus electronic databases were searched from inception to 20 January 2017. ELIGIBILITY CRITERIA FOR SELECTING STUDY: Studies that reported the total number of participants/population by sex, total number of ACL injuries by sex and total person-time by sex were included. RESULTS: Twenty-eight studies were included. The IP and IR of ACL injury in female football players were 2.0% (95% CI 1.2% to 3.1%) and 2.0/10 000 athlete exposures (AEs) (95% CI 1.6 to 2.6; I2=91%) over a period of one season to 4 years. The IP and IR of ACL injury in male players were 3.5% (95% CI 0.7% to 8.2%) and 0.9/10 000 AEs (95% CI 0.7 to 1.1; I2=94%). Studies that evaluated matched cohorts of female and male players showed no difference in IP (relative risk=1.2; 95% CI 0.9 to 1.6; P=0.47) over a period of one season to 4 years. Women were at greater risk than men (incidence rate ratio (IRR)=2.2; 95% CI 1.6 to 3.1; I2=83%; P<0.001). When accounting for participation level, the difference in IR between women and men was greatest for intermediate players (IRR=2.9; 95% CI 2.4 to 3.6) compared with amateur (IRR=2.6; 95% CI 1.4 to 4.8) and elite (IRR=2.0; 95% CI 1.1 to 3.4) players. SUMMARY/CONCLUSION: Overall, more men sustained ACL injury in football. There was no difference in the relative risk of ACL injury between female and male football players in a window that spanned one season to 4 years. The IR of ACL injury among women was 2.2 times higher than the IR of ACL injury among men. The reported sex disparity in ACL injury was independent of participation level.

Beyond frequency counts: Novel conceptual recurrence analysis metrics to index semantic coordination in team communications.

Semantic alignment is a key process underlying interpersonal and team communication. However, semantic similarity is difficult to quantify, and statistical approaches designed to measure it often rely on methods that make the identification of the relative importance of key words difficult. This study outlines how conceptual recurrence analysis (CRA) can address these issues and can be used to detect conceptual structure in interpersonal communication. We developed several novel CRA metrics to analyze communication data reported previously by Mancuso, Finomore, Rahill, Blair, and Funke (Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 58, 405-409, 2014), gathered from teams who worked cooperatively on a logic puzzle under different cognitive biasing contexts. CRA, like other measures of semantic coordination, relies on parameters whose values affect estimates of semantic alignment. We evaluated how the dimensionality of semantic spaces affects metrics quantifying the conceptual similarity of communicative exchanges, and whether metrics calculated from top-down, a priori semantic spaces or bottom-up semantic spaces empirically derived from each data set were more sensitive to biasing context. We found that the novel CRA measures were sensitive to manipulations of cognitive bias, and that higher-dimensional, bottom-up semantic spaces generally yielded more sensitivity to the experimental manipulations, though when the communication was evaluated with respect to specific key concepts, lower-dimensional, top-down spaces performed nearly as well. We conclude that CRA is sensitive to experimental manipulations in ways consistent with prior findings and that it presents a customizable framework for testing predictions about interpersonal communication patterns and other linguistic exchanges.

Injury Risk Factors Integrated Into Self-Guided Real-Time Biofeedback Improves High-Risk Biomechanics.

CONTEXT: Existing anterior cruciate ligament (ACL) injury prevention programs have failed to reverse the high rate of ACL injuries in adolescent female athletes. OBJECTIVE: This investigation attempts to overcome factors that limit efficacy with existing injury prevention programs through the use of a novel, objective, and real-time interactive visual feedback system designed to reduce the biomechanical risk factors associated with ACL injuries. DESIGN: Cross-over study. SETTING: Medical center laboratory. PARTICIPANTS: A total of 20 females (age = 19.7 [1.34] y; height = 1.74 [0.09] m; weight = 72.16 [12.45] kg) participated in this study. METHODS: Participants performed sets of 10 bodyweight squats in each of 8 training blocks (ie, 4 real-time and 4 control blocks) and 3 testing blocks for a total of 110 squats. Feedback conditions were blocked and counterbalanced with half of participants randomly assigned to receive the real-time feedback block first and half receiving the control (sham) feedback first. RESULTS: Heat map analysis revealed that during interaction with the real-time feedback, squat performance measured in terms of key biomechanical parameters was improved compared with performance when participants squatted with the sham stimulus. CONCLUSIONS: This study demonstrates that the interactive feedback system guided participants to significantly improve movement biomechanics during performance of a body weight squat, which is a fundamental exercise for a longer term ACL injury risk reduction intervention. A longer training and testing period is necessary to investigate the efficacy of this feedback approach to effect long-term adaptations in the biomechanical risk profile of athletes.

Intermittent coupling between grip force and load force during oscillations of a hand-held object.

Tightly coordinated grip force adaptations in response to changing load forces have been reported as continuous, stable, and proportional to the load force changes. Considering the existence of inherent sensorimotor feedback delays, current accounts of grip force-load force coupling invoke explicit predictive mechanisms in the form of internal models for feedforward control to account for anticipatory grip force modulations. However, recent findings suggest that the stability and regularity of grip force-load force coupling is less persistent than previously thought. Thus, the objective of the current study was to comprehensively quantify the time-varying characteristics of grip force-load force coupling. Investigations into the coupling's dynamics during continuous 30 s bouts of load force oscillation revealed intermittent phases of coordination, as well as phases that varied in stability, rather than a persistent and continuously stable pattern of coordination. These findings have important implications for accounts of grip force-load force coupling and of anticipation in motor control, more broadly.

A jugular vein compression collar prevents alterations of endogenous electrocortical dynamics following blast exposure during special weapons and tactical (SWAT) breacher training.

Exposure to explosive blasts places one at risk for traumatic brain injury, especially for special weapons and tactics (SWAT) and military personnel, who may be repeatedly exposed to blasts. In the current study, the effectiveness of a jugular vein compression collar to prevent alterations in resting-state electrocortical activity following a single-SWAT breacher training session was investigated. SWAT team personnel were randomly assigned to wear a compression collar during breacher training and resting state electroencephalography (EEG) was measured within 2 days prior to and two after breacher training. It was hypothesized that significant changes in brain dynamics-indicative of possible underlying neurodegenerative processes-would follow blast exposure for those who did not wear the collar, with ameliorated changes for the collar-wearing group. Using recurrence quantification analysis (RQA) it was found that participants who did not wear the collar displayed longer periods of laminar electrocortical behavior (as indexed by RQA's vertical max line measure) after breacher training. It is proposed that the blast wave exposure for the no-collar group may have reduced the number of pathways, via axonal disruption-for electrical transmission-resulting in the EEG signals becoming trapped in laminar states for longer periods of time. Longer laminar states have been associated with other electrocortical pathologies, such as seizure, and may be important for understanding head trauma and recovery.

Brain-Behavior Mechanisms for the Transfer of Neuromuscular Training Adaptions to Simulated Sport: Initial Findings From the Train the Brain Project.

CONTEXT: A limiting factor for reducing anterior cruciate ligament injury risk is ensuring that the movement adaptions made during the prevention program transfer to sport-specific activity. Virtual reality provides a mechanism to assess transferability, and neuroimaging provides a means to assay the neural processes allowing for such skill transfer. OBJECTIVE: To determine the neural mechanisms for injury risk-reducing biomechanics transfer to sport after anterior cruciate ligament injury prevention training. DESIGN: Cohort study. SETTING: Research laboratory. PARTICIPANTS: Four healthy high school soccer athletes. INTERVENTIONS: Participants completed augmented neuromuscular training utilizing real-time visual feedback. An unloaded knee extension task and a loaded leg press task were completed with neuroimaging before and after training. A virtual reality soccer-specific landing task was also competed following training to assess transfer of movement mechanics. MAIN OUTCOME MEASURES: Landing mechanics during the virtual reality soccer task and blood oxygen level-dependent signal change during neuroimaging. RESULTS: Increased motor planning, sensory and visual region activity during unloaded knee extension and decreased motor cortex activity during loaded leg press were highly correlated with improvements in landing mechanics (decreased hip adduction and knee rotation). CONCLUSION: Changes in brain activity may underlie adaptation and transfer of injury risk-reducing movement mechanics to sport activity. Clinicians may be able to target these specific brain processes with adjunctive therapy to facilitate intervention improvements transferring to sport.

The Independent Perceptual Calibration of Action-Neutral and -Referential Environmental Properties.

Two experiments were conducted to explore how the calibration of perception of environmental properties taken with reference to an animal and their action capabilities (e.g., affordances) and those that are independent of action capabilities (e.g., metric properties) relate. In both experiments, participants provided reports of the maximum height they could reach above their head with a number of different stick(s) (reach-with-stick height) and the length of those stick(s), a property that is a constituent of reach-with-stick height. In Experiment 1 reach-with-stick height reports improved over trials whereas stick length reports remained constant. In Experiment 2, feedback about maximum reach-with-stick height improved perception of this affordance, but such improvements did not transfer to perception of stick length in a pretest/practice task/posttest design. The results suggest that the perceptual calibration with practice perceiving or feedback about actual dimensions of action-referential and action-neutral properties do not necessarily depend on one another.

Influence of Age on Postconcussive Postural Control Measures and Future Implications for Assessment.

OBJECTIVE: To examine the influence of age, sex, attention-deficit hyperactivity disorder (ADHD) status, previous history of concussion, and days since injury on postconcussion postural control assessment in adolescents who have suffered a concussion. DESIGN: Prospective cohort study. SETTING: Hospital-based outpatient clinic. PARTICIPANTS: Seventy-one participants (42 males; 29 females) with mean age 14.14 ± 2.44. INDEPENDENT VARIABLES: Age, sex, previous concussion history, ADHD status, total and severity of postconcussion symptoms, and days since injury. MAIN OUTCOME MEASURES: Total Balance Error Scoring System score, path length, center-of-pressure (COP) area, sample entropy, and Romberg quotient. RESULTS: Pearson product-moment correlation coefficients were calculated to test for potential associations between the continuous participant characteristics and the postural control variables. Spearman correlation was used to test the association between symptom severity and the postural control variables. Standard multiple regression was used to model the extent to which participant characteristics accounted for the variance in the postural sway variables. Age was significantly associated with all of the postural sway variables except COP area for the eyes open condition and sample entropy in the anterior-posterior direction for the eyes closed condition. Sex, ADHD status, and previous concussion history did not significantly predict postural control scores. CONCLUSIONS: Age significantly influences scores on common postconcussion postural control assessments. CLINICAL RELEVANCE: This study demonstrates that age is a critical factor that needs to be accounted for to improve the clinical appropriateness and utility of current postconcussion postural control assessments.

Characteristics of postural control among young adults with asthma.

OBJECTIVE: We investigated whether young adults with asthma have impaired balance and whether this impairment is related to altered musculoskeletal function and/or psychological characteristics. METHODS: 21 participants with a self-reported asthma diagnosis but no known postural instability or history of falls, and 18 control participants were recruited from undergraduate psychology courses. Participants performed a postural control task of maintaining the center of pressure (COP) in a fixed position with visual feedback (feedback condition) and while standing as still as possible without visual feedback (no-feedback condition). COP variability, regularity and task performance were used to characterize the quality of balance. To document group differences in musculoskeletal function, we measured neck and lower back angles as well as range of motion (ROM) of the neck in the frontal and sagittal planes. To document group differences in psychological state, we administered self-report questionnaires to assess symptoms of anxiety and depression, anxiety sensitivity and negative effect. RESULTS: COP variability and task performance were similar between the groups, but participants with asthma exhibited more regular anterior-posterior COP dynamics. Participants with asthma had smaller ROM of neck extension, a more forwardly bent neck, greater thoracic spine angle, and they reported greater levels of the physical concerns facet of anxiety sensitivity. These musculoskeletal and affective variables moderated COP differences between the groups. CONCLUSIONS: Young adults with asthma showed a different postural control strategy in the absence of any obvious balance impairment. This change in strategy is related to musculoskeletal and affective characteristics of individuals with asthma.

Postconcussion Postural Sway Variability Changes in Youth: The Benefit of Structural Variability Analyses.

PURPOSE: The purpose of this study was to evaluate the utility of postural sway variability as a potential assessment to detect altered postural sway in youth with symptoms related to a concussion. METHODS: Forty participants (20 who were healthy and 20 who were injured) aged 10 to 16 years were assessed using the Balance Error Scoring System (BESS) and postural sway variability analyses applied to center-of-pressure data captured using a force plate. RESULTS: Significant differences were observed between the 2 groups for postural sway variability metrics but not for the BESS. Specifically, path length was shorter and Sample and Renyi Entropies were more regular for the participants who were injured compared with the participants who were healthy (P < .05). CONCLUSION: The results of this study indicate that postural sway variability may be a more valid measure than the BESS to detect postconcussion alterations in postural control in young athletes.

A Commentary on Real-Time Biofeedback to Augment Neuromuscular Training for ACL Injury Prevention in Adolescent Athletes.

Anterior cruciate ligament injury and the associated long-term sequelae, such as immediate reductions in physical inactivity, increased adiposity and increased risk of osteoarthritis throughout adulthood, are a major health concern for adolescent athletes. Current interventions for injury prevention may have limited effectiveness, are susceptible to issues of compliance and have not achieved the widespread acceptance necessary to promote full adoption. Neuromuscular training (NMT) is a well-established training intervention introduced to affect change in modifiable biomechanical risk factors to reduce the risk of injury in these athletes. Despite moderate success, neuromuscular training is still limited by its reliance on subjective feedback and after the fact (i.e., offline) objective feedback techniques. The purpose of this commentary is to discuss technological tools that could be used to enhance and objectify targeted biofeedback interventions to complement NMT. Electromyography, force plates, motion sensors, and camera-based motion capture systems are innovative tools that may have realistic feasibility for integration as biofeedback into NMT programs to improve training outcomes. Improved functional deficit identification and corrective analysis may further improve and optimize athletic performance, and decrease the risk of sports-related injury during sport performance. Key pointsSpecific, targeted interventions that isolate injury risk factors and can help correct modifiable neuromuscular deficits are essential.Current training interventions for anterior cruciate ligament (ACL) injury prevention have only demonstrated limited effectiveness and have not achieved the widespread acceptance necessary to promote full adoption to reduce ACL injury rates.The paper provides an overview of innovative strategies and technological tools that could be used to enhance and objectify targeted biofeedback interventions to complement neuromuscular training (NMT) including electromyography, force plates, motion sensors, and camera-based motion capture systems.These strategies utilize biomechanical, physiological, or neuromotor variables for training, automate the quantitative measurement of those variables through a variety of technological modalities, and then feed those measured variables via software to provide information in simplified form for online, visual biofeedback displays.

Visual influences on postural and manual interpersonal coordination during a joint precision task.

We investigated whether the interpersonal postural coordination that occurs during a joint supra-postural, manual precision task is driven by the constraints of the task, or, instead results from visual entrainment to the movements of a co-actor. Participants were instructed to coordinate their finger movements under conditions where participants could see others' whole-body movements or could only see the results of the other's actions. Participants' finger and torso movements were recorded. Coordination was quantified using cross-recurrence quantification analysis measures. Interpersonal coordination was enhanced by, although it did not depend entirely upon, visual information about the co-actor's body movements.

In Remembrance: The Life and Legacy of Michael T. Turvey (1942-2023).

Michael T. Turvey passed away on August 12, 2023 at the age of 81. This obituary aims to honor his life and career by highlighting some key events in his personal and professional life, noting some of his many remarkable accomplishments, and emphasizing his exceptional mentorship, friendship, and generosity.

Felt heaviness is used to perceive the affordance for throwing but rotational inertia does not affect either.

Bingham et al. discovered a perceptible affordance property, composed of a relation between object weight and size, used to select optimal objects for long-distance throwing. Subsequent research confirmed this finding, but disconfirmed a hypothesis formulated by Bingham et al. about the information used to perceive the affordance. Following this, Zhu and Bingham investigated the possibility that optimal objects for throwing are selected as having a particular felt heaviness. The results supported this hypothesis. Perceived heaviness exhibits the size-weight illusion: to be perceived as equally heavy, larger objects must weigh more than smaller ones. Amazeen and Turvey showed that heaviness perception is determined by rotational inertia. We investigated whether rotational inertia would determine both perceived heaviness and throw-ability when spherical objects were held in the hand and wielded about the wrist. We found again that a particular judged heaviness corresponded to judged throw-ability. However, rotational inertia was found to have no effect on either judgment, suggesting that rotational inertia does not determine perceived heaviness of spherical objects held in the hand, as it did for the weighted-rod-type objects used by Amazeen and Turvey.