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Joseph Hamill

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Frank E. DiLiberto and Deborah A. Nawoczenski

Although the midfoot is recognized to have an important role in the successful performance of a single-limb heel rise, healthy heel rise performance remains primarily characterized by ankle function. The purpose of this study was to examine the contribution of midfoot region power to single-limb heel rise in healthy adults. Participants (N = 12) performed 20 single-limb heel rises. An electromagnetic motion capture system and a force plate were used to record 3-segment foot motion and ground reaction forces. Inverse dynamic calculations were performed to obtain ankle and midfoot region powers. These data were evaluated with descriptive statistics. A correlation was performed to evaluate the contribution of midfoot region power to heel height, as heel height is a clinical measure of heel-rise performance. The midfoot contributed power during single-limb heel rise (peak positive power: 0.5 [0.2] W·kg−1). Furthermore, midfoot peak power accounted for 36% of the variance in heel height (P = .04). As energy generating internal mechanisms, such as muscle activity, are attributed to power generation, midfoot tissue loading and muscle performance should be considered during clinical and modeling applications of the heel-rise task.

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Marlowe Pecora, Luc Tremblay and Matthew Heath

Reaches with overlapping stimulus-response spatial relations (propointing) adhere to speed–accuracy relations as defined by Paul Fitts’ index of difficulty equation (IDFitts: in bits of information). This movement principle is attributed to response mediation via the “fast” visuomotor networks of the dorsal visual pathway. It is, however, unclear whether the executive demands of dissociating stimulus-response spatial relations by reaching mirror-symmetrical to a target (antipointing) elicits similar adherence to Fitts’ equation. Here, pro- and antipointing responses were directed to a constant target amplitude with varying target widths to provide IDFitts values of 3.0, 3.5, 4.3, and 6.3 bits. Propointing movement times linearly increased with IDFitts—a result attributed to visually based trajectory corrections. In contrast, antipointing movement times, deceleration times, and endpoint precision did not adhere to Fitts’ equation. These results indicate that antipointing renders a “slow” and offline mode of control mediated by the visuoperceptual networks of the ventral visual pathway.

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Niranjan Chakrabhavi and Varadhan SKM

A task involving an instructed finger movement causes involuntary movements in the noninstructed fingers of the hand, also known as finger interdependence. It is associated with both mechanical and neural mechanisms. The current experiment investigated the effect of finger interdependence due to systematic changes of the wrist posture, close to neutral. Eight right-handed healthy human participants performed submaximal cyclic flexion and extension at the metacarpophalangeal joint at 0° neutral, 30° extension, and 30° flexion wrist postures, respectively. The experiment comprised of an instruction to move one of the 4 fingers—index, middle, ring, and little. Movements of the instructed and noninstructed fingers were recorded. Finger interdependence was quantified using enslavement matrix, individuation index, and stationarity index, and it was compared across wrist postures. The authors found that the finger interdependence does not change with changes in wrist posture. Further analysis showed that individuation and stationarity indices were mostly equivalent across wrist postures, and their effects were much smaller than the average differences present among the fingers. The authors conclude that at wrist postures close to neutral, the finger interdependence is not affected by wrist posture.

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Joshua J. Liddy, Amanda J. Arnold, HyeYoung Cho, Nathaniel L. Romine and Jeffrey M. Haddad

Holding an object has been found to reduce postural sway during quiet standing. However, people normally stand to accomplish suprapostural goals, such as fitting a key into a lock. Postural control should therefore be assessed by examining postural outcomes in the context of suprapostural task performance. This study assessed whether holding an object increased standing postural stability and improved the performance of a concurrent precision manual task. A total of 15 young adults performed a precision manual task with their dominant hand while holding or not holding an object in their nondominant hand. Postural stability was assessed using measures of postural sway and time to boundary. Suprapostural task performance was assessed as an error count. Holding did not influence postural sway or suprapostural task performance. Discrepancies among previous studies coupled with the present findings suggest that the effects of holding an object on standing posture are highly sensitive to the experimental context. The authors provide several explanations for their findings and discuss the limitations of previous suggestions that holding an object may have clinical relevance for balance-compromised populations.

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Aisha Chen, Sandhya Selvaraj, Vennila Krishnan and Shadnaz Asgari

Accurate and reliable detection of the onset of gait initiation is essential for the correct assessment of gait. Thus, this study was aimed at evaluation of the reliability and accuracy of 3 different center of pressure–based gait onset detection algorithms: A displacement baseline–based algorithm (method 1), a velocity baseline–based algorithm (method 2), and a velocity extrema–based algorithm (method 3). The center of pressure signal was obtained during 10 gait initiation trials from 16 healthy participants and 3 participants with Parkinson’s disease. Intrasession and absolute reliability of each algorithm was assessed using the intraclass correlation coefficient and the coefficient of variation of center of pressure displacement during the postural phase of gait initiation. The accuracy was evaluated using the time error of the detected onset by each algorithm relative to that of visual inspection. The authors’ results revealed that although all 3 algorithms had high to very high intrasession reliabilities in both healthy subjects and subjects with Parkinson’s disease, methods 2 and 3 showed significantly better absolute reliability than method 1 in healthy controls (P = .001). Furthermore, method 2 outperformed the other 2 algorithms in both healthy subjects and subjects with Parkinson’s disease with an overall accuracy of 0.80. Based on these results, the authors recommend using method 2 for accurate and reliable gait onset detection.

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Kristin D. Morgan

Between-limb deficits in vertical ground reaction force (vGRF) production continue to remain years after anterior cruciate ligament rehabilitation, resulting in altered dynamic stability. However, the challenge is in identifying ways to assess this between-limb stability. This study implemented second-order autoregressive [AR(2)] modeling and its stationarity triangle to both quantitatively and visually delineate differences in dynamic stability from peak vGRF data in controls and post-anterior cruciate ligament reconstruction (ACLR) individuals during running. It was hypothesized that post-ACLR individuals would exhibit less dynamic stability than the controls, and that they would reside in a different location on the stationarity triangle, thus denoting differences in stability. The results presented supported the hypothesis that post-ACLR individuals exhibited significantly less dynamic stability than their control counterparts based on their model coefficients (AR1 P < .01; AR2 P = .02). These findings suggested that the post-ACLR individuals adopted a similar running pattern, possibly due to muscle weakness asymmetry, which was less dynamically stable and potentially places them at greater risk for injury. The ability of this approach to both quantitatively and visually delineate differences between these 2 groups indicates its potential as a return-to-sport decision tool.

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Kylie McNeill, Natalie Durand-Bush and Pierre-Nicolas Lemyre

While coaches are considered at risk of experiencing burnout, there is an absence of intervention studies addressing this syndrome. The purpose of this qualitative study was to conduct a self-regulation intervention with five Canadian developmental (n = 2) and elite (n = 3) sport coaches (three men, two women) experiencing moderate to high levels of burnout and examine the perceived impact of this intervention on their self-regulation capacity and experiences of burnout and well-being. The content analysis of the coaches’ outtake interviews and five bi-weekly journals revealed that all five of them learned to self-regulate more effectively by developing various competencies (e.g., strategic planning for their well-being, self-monitoring) and strategies (e.g., task delegation, facilitative self-talk). Four of the coaches also perceived improvements in their symptoms of burnout and well-being. Sport psychology interventions individualized for coaches are a promising means for helping them manage burnout and enhance their overall functioning.

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Yumeng Li, He Wang and Kathy J. Simpson

The purpose of the study was to compare the tibiofemoral contact forces of participants with chronic ankle instability versus controls during landings using a computer-simulated musculoskeletal model. A total of 21 female participants with chronic ankle instability and 21 pair-matched controls performed a drop landing task on a tilted force plate. A 7-camera motion capture system and 2 force plates were used to test participants’ lower-extremity biomechanics. A musculoskeletal model was used to calculate the tibiofemoral contact forces (femur on tibia). No significant between-group differences were observed for the peak tibiofemoral contact forces (P = .25–.48) during the landing phase based on paired t tests. The group differences ranged from 0.05 to 0.58 body weight (BW). Most participants demonstrated a posterior force (peak,  ∼1.1 BW) for most duration of the landing phase and a medial force (peak, ∼0.9 BW) and large compressive force (peak, ∼10 BW) in the landing phase. The authors conclude that chronic ankle instability may not be related to the increased tibiofemoral contact forces or knee injury mechanisms during landings on the tilted surface.

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Jessica Ross and Peter D. MacIntyre

Flow is a desirable state of consciousness and absorption in an optimally challenging activity. Prior research has investigated individual differences in flow. The present study investigates flow by contrasting physical versus mental activities, using a mixed-methods, sequential explanatory design. The sample from the quantitative phase included 205 undergraduate university students assessed on measures of personality, difficulties in emotion regulation, and flow. The big-five traits intellect and conscientiousness, as well as the emotion regulation subscale “lack of emotional clarity” predicted flow during mental activities, but unexpectedly no variables significantly predicted physical flow activities. The second phase used semi-structured interviews with 10 participants. Analyses of the interviews helped further explain the statistical findings, revealing four main themes: role of stress, source of guilt, presence of others, and satisfaction and fulfillment. We conclude that flow is especially relevant in physical activities which have advantages over mental activities in opportunities to experience flow.