Contemporary experience of mitral transcatheter edge-to-edge repair technology in patients with mitral annular calcification.

BACKGROUND: Mitral annular calcification (MAC) has been an exclusion for many of the earlier pivotal trials that were instrumental in gaining device approval and indications for mitral transcatheter edge-to-edge repair (M-TEER). AIMS: To evaluate the impact of MAC on the procedural durability and success of newer generation MitraClip® systems (G3 and G4 systems). METHODS: Data were collected from Northwell TEER registry. Patients that underwent M-TEER with third or fourth generation MitraClip device were included. Patients were divided into -MAC (none-mild) and +MAC (moderate-severe) groups. Procedural success was defined as ≤ grade 2 + mitral regurgitation (MR) postprocedure, and durability was defined as ≤ grade 2 + MR retention at 1 month and 1 year. Univariate analysis compared outcomes between groups. RESULTS: Of 260 M-TEER patients, 160 were -MAC and 100 were +MAC. Procedural success was comparable; however, there were three patients who required conversion to cardiac surgery during the index hospitalization in the +MAC group versus none in the -MAC group (though this was not statistically significant). At 1-month follow-up, there were no significant differences in MR severity. At 1-year follow-up, +MAC had higher moderate-severe MR (22.1% vs. 7.5%; p = 0.002) and higher mean transmitral gradients (5.3 vs. 4.0 mmHg; p = 0.001) with no differences in mortality, New York Heart Association functional class or ejection fraction. CONCLUSION: In selective patients with high burden of MAC, contemporary M-TEER is safe, and procedural success is similar to patients with none-mild MAC. However, a loss of procedural durability was seen in +MAC group at 1-year follow-up. Further studies with longer follow-ups are required to assess newer mTEER devices and their potential clinical implications in patients with a high burden of MAC.

Manipulating sensory information: obstacle crossing strategies between typically developing children and young adults.

Individuals constantly adapt their locomotion to navigate through complex environments. However, little known about anticipatory strategies used by children during adaptive locomotion. The purpose of this study was to compare the effects of manipulating visual and somatosensory information during a multiple obstacle crossing task between children and adults. It was hypothesized that compared to young adults, children would have difficulty with anticipatory motor planning and online control during a multiple obstacle crossing task when sensory information was manipulated. Children (N = 16, [Formula: see text] = 9 ± 1.07 years) and young adults (N = 16, [Formula: see text] = 22 ± 0.96 years) walked along a 7 m pathway towards a goal while avoiding stepping on one, or two virtual obstacles placed 5 m from the start. Visual information regarding the number of obstacles was either presented at the start of steady-state locomotion, or two steps prior to the first obstacle. Each participant completed 36 trials, 18 on flat ground and 18 on foam terrain. Results indicated that in comparison to young adults, children's foot positions were significantly closer to the first obstacle when visual information about the obstacle was delayed. On flat ground, children demonstrated similar Trail foot positions relative to the first and second obstacles, suggesting children planned for the avoidance of the obstacles separately. On foam terrain, children performed similar to young adults, such that their Trail foot position relative to the first obstacle was significantly closer to the obstacle compared to their Trial foot position relative to the second obstacle. The results suggest that children plan for the avoidance of multiple obstacles differently compared to young adults. When stability is challenged, maintaining forward progression of locomotion overrides the planning of obstacle crossing, such that children perform similar to young adults. Therefore, it appears that children have difficulties with online control and anticipatory motor strategies during a multiple obstacle crossing task.

Avoidance behaviours of young adults during a head-on collision course with an approaching person.

Individuals use visual information to guide their avoidance behaviours. More specifically, individuals may directly perceive the time prior to colliding with an approaching obstacle (i.e., time to contact, TTC) to determine when to avoid. In addition, individuals use body-scaled information to control their movements. These avoidance behaviours differ when avoiding a human obstacle compared to an inanimate object. As such, the purpose of this experiment was to examine the avoidance behaviours of individuals during a head-on collision course with an approaching person. Young adults (N = 20, [Formula: see text] = 22.25 ± 1.5 years, 10 males) were instructed to walk along a 10 m path towards a goal located along the midline. A female confederate positioned along the midline walked towards the participants to one of the four predetermined final positions: (1) along the midline in the participants' starting position; (2) stopped along the midline 2.5 m from her starting position; (3) to the left of the participants' starting position; and (4) to the right of the participants' starting position. Results revealed when the path of the confederate was certain, individuals used a greater TTC to determine when to change their path in comparison with when the path of the confederate was uncertain. Males were found to avoid significantly earlier (i.e., larger TTC) than females. However, following a change in path, sex did not impact the avoidance behaviours of the groups, but rather, the environment was the regulating factor.

The effects of obstacle proximity on aperture crossing behaviours.

Affordance theory and behavioural dynamics have been used as theoretical constructs to explain how individuals interact with the environment in order to avoid obstacles. Features of obstacle distance and multiple obstacle avoidance have been discussed in unique studies, yet the interactions of these environmental features have yet to be explored. The purpose of this study was to asses the effects of obstacle distance, relative to the goal, on aperture crossing strategies. Kinematics and gaze behaviours were assessed in a cohort of female young adults (N = 24, 21.3 ± 1.4 years). Results identified that participants chose to navigate through gaps of 1.3× shoulder width or greater, regardless of obstacle distance. However, safety margin in the anterior-posterior direction was found to increase with increased obstacle distance, suggesting unique environmental affordances for each obstacle distance. Therefore, although decision making on whether to navigate through, or around, the aperture appears to be unaffected by obstacle location, specific environmental features result in unique kinematic behaviours. Such behaviours fit within, and add merit to, the tenets of both affordance theory and behavioural dynamics.

The effects of exercise on a choice reaction time task in individuals with post-concussion syndrome.

PURPOSE: To assess cognitive performance differences pre- and post-exercise in individuals without concussion (non-concussed, NC) and individuals with post-concussion syndrome (PCS). METHODS: A total of 30 participants completed a choice reaction time (CRT) task in the form of an iPad application, measuring each individual's decision-making capabilities, while wearing a head-mounted eye tracker system. Participants completed four blocks of testing; the time interval between the first two blocks of trials and the last two blocks of trials was 10 minutes. Between the completion of block 2 and the start of block 3, the participants completed a 15-minute bout of exercise. RESULTS: Individuals with PCS at rest and following exercise displayed greater average reaction time (RT) (p<.01), lower overall accuracy (p<.01) and shorter final fixation durations (p<.05) than NC. Combined influence of learning and exercise resulted in a significant difference (p<.05) in RT from block 1 to block 3 and block 1 to block 4. CONCLUSION: Persistent concussion-based symptoms may be indicative of deficits in higher-level cognitive processing, as indicated by both decreased CRT performance and differences in gaze behaviours between groups. Therefore, individuals with PCS may not elicit appropriate decisions when navigating through an environment, potentially leading to further risk of injury.

Using a Manipulation Check to Uncover Age-Related Difference in Focus of Attention Instruction During a Balance Task.

BACKGROUND/STUDY CONTEXT: A manipulation check was used to investigate whether there is an age-related difference in the adherence to specific external- and internal-focus instructional constraints. METHODS: Participants stood on a force platform and were to maintain a feedback cursor (representing their center of pressure) along the horizontal direction, within a target on a computer monitor. Trials were conducted with either an external focus of attention (keeping the feedback cursor within the target) or an internal focus of attention (keeping the weight evenly distributed between both legs). RESULTS: The finding showed that younger adults followed the experimental instructions; however, older adults relied on external visual information when they were asked to focus on the body movements. CONCLUSION: Age-related declines may contribute to attention allocation differences. The authors propose that specific manipulation checks be used to ensure proper adherence to instructions when comparing age-related differences in postural control.

Strategies used by individuals with multiple sclerosis and with mild disability to maintain dynamic stability during a steering task.

Changing direction during walking is a common task humans encounter every day. This destabilizing event requires the central nervous system (CNS) to quickly produce an appropriate response, maintain stability, and propel the body in the intended direction. Previous research has demonstrated that 'individuals with multiple sclerosis' (IwMS) with mild balance impairment display differences in gait characteristics during clinical tests compared with controls. The current study used dynamic stability margin [DSM, difference between COM (i.e. the weighted average of the central point of an individual's total body mass) and lateral BOS (i.e. the most lateral border of the foot that is in contact with the ground)] calculations in addition to gait kinematics to determine whether dynamic stability differences during a steering task were present between IwMS with mild balance impairment and 'healthy age-matched individuals' (HAMI) as well as between IwMS with mild balance impairment and 'community-dwelling older adults' (OA). All IwMS reported mild balance impairment with expanded disability status scale scores ranging between 1.0 and 3.0. The steering task required participants to walk 3 m towards a pressure sensitive trigger mat that would illuminate one of five lights to indicate the future direction of travel (i.e. straight, 45° or 60° to the left or right of the midline). Results revealed that IwMS displayed reduced walking speed and cadence during the approach phase in addition to a smaller DSM range (i.e. COM remained close to lateral BOS) during the entire steering task when compared with HAMI. However, when compared to OAs, IwMS did not display differences in any of the gait kinematics or DSM calculations. Findings suggest that the IwMS displayed a conservative gait strategy in order to maintain stability during the steering task. Lack of dynamic stability differences between IwMS and OAs indicate that both groups use similar strategies to adapt locomotion as a result of impaired somatosensory quality and/or processing.

Understanding balance differences in individuals with multiple sclerosis with mild disability: an investigation of differences in sensory feedback on postural control during a Romberg task.

A major presenting symptom in 'individuals with multiple sclerosis with mild balance disability' (IwMS) is poor postural control, resulting from slowed spinal somatosensory conduction. Postural control deficits in IwMS are most apparent when vision is removed and the base of support is reduced such is the case during tandem and single support stances. The current study used center of pressure (COP) measurements to determine whether postural control differences exist between IwMS and either 'healthy age-matched individuals' (HAMI) or 'community-dwelling older adults' (OA). Postural control was evaluated using a Romberg standing task, which required participants to stand with their feet together and hands by their sides for 45 s with either their eyes open or closed. Results revealed that COP velocity root mean square was greater in IwMS and their COP position was closer to their self-selected maximum stability limits (e.g., greater Standing Index proportion) when vision was removed compared to HAMI. Conversely, IwMS displayed similar postural control characteristics to OA. The current study highlights two novel findings: (1) the utility of novel COP measurements to assess differences in the level of postural control in IwMS; and (2) the benefit of assessing postural control levels in IwMS to not only a population with a fully intact and functional postural control system (HAMI) but also to another population that is thought to experience postural control deficits (OA).

Cortical hypoexcitability persists beyond the symptomatic phase of a concussion.

PRIMARY OBJECTIVE: The purpose of this research was to assess cortical excitability, voluntary activation of muscle and force sensation beyond the initial highly symptomatic period post-concussion (1-4 weeks post-injury). It was hypothesized that reduced excitability of the motor cortex may impair muscle activation and alter perceptions of force and effort. RESEARCH DESIGN: Eight concussed varsity football players were age- and position-matched with eight healthy teammates to control for training and body size. Healthy controls had not suffered a concussion in the previous 12 months. METHODS AND PROCEDURES: Paired-pulse transcranial magnetic stimulation was used to assess cortical excitability, voluntary activation was calculated using cortical twitch interpolation technique and sense of force was determined using constant-force sensation contractions. MAIN OUTCOMES AND RESULTS: The concussed group had lower intra-cortical facilitation (p = 0.036), lower maximal voluntary muscle activation (p = 0.038) and greater perceptions of force (p < 0.05), likely due to compensatory increases in upstream drive, than their healthy matched teammates. CONCLUSIONS: Taken together, these findings suggest a state of hypoexcitability that persists beyond the immediate acute phase of a concussion and may result in neuromuscular impairments that would call to question the athlete's readiness to return to sport.

Collision avoidance behaviours while young adults avoid a virtual pedestrian approaching on a 45° angle under attentionally demanding conditions.

Individuals rely on visual information to determine when to adapt their behaviours (i.e., by changing path and/or speed) to avoid an approaching object or person. After initiating an avoidance behaviour, individuals may control the space (i.e., minimum clearance distance) between themselves and another person or object. The current study aimed to determine the action strategies of young adults while avoiding a virtual pedestrian approaching along a 45° angle in an attentionally demanding task. Twenty-one young adults (22.9 ± 1.9 yrs., 11 males) were immersed in a virtual environment and were instructed to walk along a 7.5 m path towards a goal located along the midline. Two virtual pedestrians (VP) positioned 2.83 m to the left and right of the midline approached participants on a 45° angle. To manipulate the point at which the participants and the VP would intersect during different trials, the VP approached at one of three speeds: 0.8×, 1.0×, or 1.2× each participants' average walking speed. Participants were instructed to walk to a goal without colliding with the VP while performing the attention task; reporting whether a shape changed above the VPs' heads. Results revealed that young adults did not modulate their timing of avoidance to the approach characteristics of the VP, as they consistently avoided the collision 1.67 s after the VP began moving. However, young adults seem to control how they avoid an oncoming collision by maintaining a consistent safety margin after an avoidance behaviour was initiated.

A treadmill running research protocol to assess dynamic visual acuity and balance for athletes with and without recent concussion history.

Athletes interpret dynamic visual scenes quickly and accurately during physical exertion. It is important to understand how increased exertion may impact vision and cognition following sport-related concussion (SRC).Purpose To examine the effect of a treadmill running research protocol on the assessment of dynamic visual acuity (DVA) and balance for athletes with and without recent history of SRC.Methods Varsity athletes following recent SRC (CONC=12) were compared to athletes without SRC (ATHLETE=19). The DVA task presented a Tumbling 'E' target in four possible orientations during random walk (RW) or horizontal (H) motion at a speed of 30°/s. Participants performed DVA trials standing on a force plate (1000Hz) at four time points: 1) pre-exercise (PRE-EX), 2) immediately (POST1), 3) 10-minutes (POST10), and 4) 20-minutes post- exercise (POST20). Performance was calculated as a change in DVA score from PRE-EX and median response time (RT, ms). Balance control was analyzed using the root mean square of centre of pressure displacement (dCOP).Results Both groups maintained DVA scores for both motion types and exhibited immediate exercise-induced benefits on RT. Both groups had similar change in balance control strategy following treadmill exercise.Conclusion Both groups elicited similar exercise-induced benefits on DVA following exercise. A repeated measures assessment following vigorous exercise may provide meaningful insights about visual and neurocognitive functions for athletes returning to sport following concussion.

IntraCardiac echocardiography-guided leaflet modification for coronary protection prior to transcatheter valve-in-valve replacement.

A 79-year-old man with a failed 25-mm CE Magna Ease 3300 surgical prosthesis (Edwards Lifesciences) and of high re-operative surgical risk (STS 8%) presented with dyspnea, NYHA III. Cardiac computed tomography angiography revealed anatomy that was high risk for coronary occlusion with a short right coronary artery height of 6 mm and a valve-to-coronary distance of 2 mm.

Unveiling the Hidden Stroke Threat in Patients With Atrial Fibrillation and Primary Hyperparathyroidism.

Recent American College of Cardiology (ACC), American Heart Association (AHA), American College of Clinical Pharmacy (ACCP), and Heart Rhythm Society (HRS) guidelines suggest that patients with atrial fibrillation (AF) at intermediate to low annual risk of ischemic stroke can benefit from consideration of factors that might modify their risk of stroke. The role of nontraditional risk factors, such as primary hyperparathyroidism (PHPT), remains unexplored. In our study, we investigated the potential association between PHPT and the risk of ischemic stroke in patients with AF. Using data from the Nationwide Inpatient Sample Database, a retrospective cohort study focused on the adult population with AF, we stratified the participants based on PHPT presence. Demographic information, co-morbidities, and hospitalization details were extracted using International Classification of Diseases, Tenth revision codes. Propensity score matching was applied, encompassing over 20 confounding variables, including the risk factors outlined in the CHA2DS2-VASc (Congestive heart failure (C), Hypertension (H), Age ≥75 years (A2), Diabetes Mellitus (D), Stroke/Transient Ischemic Attack (TIA)/Thromboembolism (S2), Vascular disease (V), Age 65-74 years (A), Sex category [female] (Sc)) score. Multivariate logistic regression analysis was performed after matching to assess the independent impact of PHPT as an ischemic stroke risk factor. A total of 2,051 of the identified 395,249 patients with AF had PHPT. The PHPT group had an average age of 74 years and consisted of more women (66.1% vs 53.0%). After matching, it was observed that the PHPT group had longer hospital stays (5 vs 4 days) and higher hospitalization charges ($45,126 vs $36,644). This group exhibited higher rates of ischemic stroke (6.0% vs 4.4%) and mortality (6.3% vs 4.9%). The adjusted outcomes showed a 1.4-fold increased risk for ischemic stroke and a 1.32-fold increased risk for mortality in the PHPT cohort. The subgroup analysis showed a higher incidence of mortality in men with a high CHA2DS2-VASc score. In conclusion, this study highlights a marked association between PHPT and ischemic stroke in patients with AF, independent of the conventional CHA2DS2-VASc score. The potential mechanisms implicated include vascular changes, cardiac dysfunction, and coagulation cascade alterations. The presence of PHPT should be taken into consideration when deciding the assessment of thromboembolic risk.

Young and older adults use body-scaled information during a non-confined aperture crossing task.

Young and older adults demonstrate differences in action when passing through confined spaces (Warren and Whang in J Exp Psychol Hum Percept Perform 13:371-383, 1987; Hackney and Cinelli in Gait Posture 33:733-736, 2011). However, it is unknown whether or not these differences in actions exist during non-confined multiple obstacle avoidance tasks. The current study aimed to determine: (1) the differences in actions between young and older adults when given a choice in path selection and (2) establish the variables that may account for these differences in action. Older adults (N = 12) and young adults (N = 12) walked along a 10-m path towards a goal and avoided two vertical poles placed halfway down the path on either side of the midline (ranging between 0.6 and 1.8× shoulder width). Results revealed that in non-confined space, both age groups use body-scaled information to determine the passability of apertures and maintain similar Critical Points to those reported in confined aperture crossing (1.4 for young adults and 1.6 for older adults). Variability of the medial-lateral centre of mass movement (i.e. how much the trunk moved side to side) between the groups most likely accounted for the larger aperture sizes (i.e. Critical Points) required by the older adults to pass through the apertures. Therefore, it appears that body-scaled information may include an individual's knowledge of both actual body size and body sway magnitude.

Action strategies used by children to avoid two vertical obstacles in non-confined space.

Information used to determine the action strategies necessary to successfully pass through apertures is based on the dimensions of the individual and the mover's action capabilities (Warren in J Exp Psychol 10:683-703, 1984; Warren and Whang in J Exp Psychol 13:371-383, 1987). Previous research has demonstrated that when children must pass through small spaces, they will produce a shoulder rotation at apertures 1.6 times their shoulder width and smaller (i.e., critical point) and their avoidance strategies are based more on dynamic than geometric measures (Snapp-Childs and Bingham in Exp Brain Res 198:527-533, 2009; Wilmut and Barnett in Exp Brain Res 210:185-194, 2011). The question remains as to whether similar strategies exist when children are given a choice in their obstacle avoidance strategy. The current study aimed to determine the action strategies employed by children when confronted with a non-confined obstacle avoidance task. Specifically, the study intended to identify the aperture width that elicited a change in action (e.g., a shoulder rotation or a change in travel path). Children (N = 12, mean age = 7.1 years, ±0.2) were instructed to walk along a 10-m path toward a visible goal located at the end of the pathway and avoid colliding with the two vertical obstacles placed halfway (5 m) down the path on either side of the midline. The space between the obstacles ranged between 0.6 and 1.8 times the participant's shoulder width (presented in increments of 0.2). Results revealed that when the aperture was too small for straight passage, children choose to circumvent the obstacles rather than rotate their shoulders the majority of the time. However, unlike young and older adults (Hackney and Cinelli in Gait Posture 37:93-97, 2013a, Exp Brain Res 225:419-429, 2013b), this strategy was not used consistently. Instead, changes in travel path were highly variable both across participants and within trials. This variability suggests that a true critical point cannot be established for children in this non-confined task. Variable actions at the time of crossing were significantly correlated with the medial-lateral center of mass variability during the approach to the obstacles. These results further support the idea that children's actions may be more affected by dynamic factors than geometric measures.

Avoidance behaviours while circumventing to the left or right of someone with different shoulder widths and facing directions: How do side, width, or orientation matter?

BACKGROUND: Collision avoidance during locomotion is influenced by a variety of situational factors. When circumventing around an inanimate object, the amount of clearance is dependent on the side of avoidance. When avoiding other pedestrians, individuals most often choose to walk behind a moving pedestrian, and avoid people differently depending on their body size. However, side of avoidance has not been evaluated with human obstacles, nor facing direction of a stationary pedestrian, nor the size of a single pedestrian. Therefore, the aim of this study is to evaluate these knowledge gaps concurrently. RESEARCH QUESTION: How do people avoid a collision to the left-side or right-side of a single stationary pedestrian (interferer) of varying shoulder width and orientation? METHODS: Participants (n = 11) walked along a 10 m pathway towards a goal, while a stationary interferer stood 6.5 m from the start. The interferer faced one of three directions relative to the participant (orientation); forward, leftward, or rightward, with either their normal shoulder width or enlarged width created by wearing football shoulder pads. Participants were explicitly instructed as to which side of the interferer to avoid (forced-left vs forced-right). Each participant completed 32 randomized avoidance trials. Centre of Mass separation at the time of crossing was used to examine individual's avoidance behaviours. RESULTS: Results revealed no effect of interferer width, but a significant side of avoidance effect, where the centre of mass separation between the participant and interferer at the time of crossing was smallest when participants avoided to their left. SIGNIFICANCE: Findings suggest that changing the facing direction or artificially increasing the shoulder width of a stationary interferer will not affect one's avoidance behaviours. However, an asymmetry in side of avoidance is maintained similar to that observed in obstacle avoidance behaviours.

Comparison of Periprocedural and Intermediate-Term Outcomes of TAVI in Patients with Ejection Fraction ≤ 20% vs. Patients with 20% < EF ≤ 40.

Treatment of congestive heart failure (CHF) with left ventricular (LV) systolic dysfunction and severe aortic stenosis (AS) is challenging, yet transcatheter aortic valve replacement (TAVR) has emerged as a suitable treatment option in such patients. We compared the periprocedural outcomes of TAVR in patients with an ejection fraction (EF) of ≤20% (VLEF group) to patients with an EF > 20% to ≤40% (LEF group). We included patients with severe AS and reduced LV ejection fraction (LVEF ≤ 40%) who underwent TAVR at four centers within Northwell Health between January 2016 and December 2020. Over 2000 consecutive patients were analyzed, of which 355 patients met the inclusion criteria. The primary composite endpoint was in-hospital mortality, moderate or greater paravalvular (PVL), stroke, conversion to open surgery, aortic valve re-intervention, and/or need for PPM. Secondary endpoints were length of stay, NYHA classification at 1 month and 1 year, mortality at 1 month and 1 year, mean valve gradient at 1 month, KCCQ score at 1 month, and ≥ moderate PVL at 1 month. There was no difference in the primary composite endpoint between the two groups (23.6% for VLEF vs. 25.3% for LEF, p = 0.29). During TAVR placement, 40% of patients in the VLEF group required ≥1 vasopressors for hypotension lasting ≥30 min vs. only 21% of patients in the LEF group (p < 0.01). Intra-aortic balloon pump (IABP) use during procedure was greater in the VLEF group (9% vs. 1%, p < 0.01)-all placed post TAVR. Emergency ECMO use was higher in the VLEF group as well (5% vs. 0%). Total length of stay was significantly different between the two groups as well (6 days vs. 3 days, p < 0.01). Both groups had a change in LVEF of ~10%. One-year outcomes were similar between the groups. All-cause mortality at 1 year was not significantly different at 1 year (13% for VLEF vs. 11% for LEF), and KCC scores were also similar (77.54 vs. 74.97). Mean aortic valve gradients were also similar (12 mmHg vs. 11 mmHg, p = 0.48). Our study suggests that patients with EF ≤ 20% can safely have TAVR with similar periprocedural outcomes compared to patients with EF > 20% to ≤40% despite higher rates of vasopressor and mechanical support.

Do walkers follow their heads? Investigating the role of head rotation in locomotor control.

Eye and head rotations are normally correlated with changes in walking direction; however, it is unknown whether they play a causal role in the control of steering. The objective of the present study was to answer two questions about the role of head rotations in steering control when walking to a goal. First, are head rotations sufficient to elicit a change in walking direction? Second, are head rotations necessary to initiate a change in walking direction or guide steering to a goal? To answer these questions, participants either walked toward a goal located 7 m away or were cued to steer to the left or right by 37°. On a subset of trials, participants were either cued to voluntarily turn their heads to the left or right, or they underwent an involuntary head perturbation via a head-mounted air jet. The results showed that large voluntary head turns (35°) yielded slight path deviations (1°-2°) in the same or opposite direction as the head turn, depending on conditions, which have alternative explanations. Involuntary head rotations did not elicit path deviations despite comparable head rotation magnitudes. In addition, the walking trajectory when turning toward an eccentric goal was the same regardless of head orientation. Steering can thus be decoupled from head rotation during walking. We conclude that head rotations are neither a sufficient nor a necessary component of steering control, because they do not induce a turn and they are not required to initiate a turn or to guide the locomotor trajectory to a goal.

Aperture Crossing in Virtual Reality: Physical Fatigue Delays Response Time.

Visual perception and cognitive (i.e., decision-making) abilities facilitate successful avoidance of obstacles in a person's environment. However, detrimental changes to cognition can occur after physical fatigue is induced by strenuous exercise. The purpose of the current study was to determine if obstacle avoidance behaviors reflect similar negative effects following physically fatiguing exercise. A virtual reality (VR) closing-gap aperture crossing task was completed by 13 recreationally active individuals to assess the effects of physical fatigue on passability judgements and response time. Participants approached closing apertures that moved at one of seven speeds while deciding to either pass through the closing aperture or stop. Participants completed four blocks of trials over a 7-day period (i.e., pre- and post-tests on the fatiguing day and control day). No significant differences for passability judgements were found across each of the blocks, but there was a significant reduction in response time on the post-test exercise day. Thus, physical fatigue increased the time required to make, and follow through on, a decision. The current findings suggest that processes requiring more cortical areas and processing (i.e., response time) may be more detrimentally affected by physically fatiguing exercise compared to dichotomous visuomotor tasks (i.e., passability judgements).

Collision avoidance strategies between two athlete walkers: Understanding impaired avoidance behaviours in athletes with a previous concussion.

BACKGROUND: Individuals who have sustained a concussion often display associated balance control deficits and visuomotor impairments despite being cleared by a physician to return to sport. Such visuomotor impairments can be highlighted in collision avoidance tasks that involves a mutual adaptation between two walkers. However, studies have yet to challenged athletes with a previous concussion during an everyday collision avoidance task, following return to sport. RESEARCH QUESTION: Do athletes with a previous concussion display associated behavioural changes during a 90°-collision avoidance task with an approaching pedestrian? METHODS: Thirteen athletes (ATH; 9 females, 23 ±â€¯4years) and 13 athletes with a previous concussion (CONC; 9 females, 22 ±â€¯3 years, concussion <6 months) walked at a comfortable walking speed along a 12.6 m pathway while avoiding another athlete on a 90º-collision course. Each participant randomly interacted with individuals from the same group 20 times and interacted with individuals from the opposite group 21 times. Minimum predicted distance (mpd) was used to examine collision avoidance behaviours between ATH and CONC groups. RESULTS: The overall progression of mpd(t) did not differ between groups (p > .05). During the collision avoidance task, previously concussed athletes contributed less when passing second compared to their peers(p < .001). When two previously concussed athletes were on a collision course, there was a greater amount of variability resulting in inappropriate adaptive behaviours. SIGNIFICANCE: Although successful at avoiding a collision with an approaching athlete, previously concussed athletes exhibit behavioural changes manifesting in riskier behaviours. The current findings suggest that previously concussed athletes possess behavioural changes even after being cleared to returned to sport, which may increase their risk of a subsequent injury when playing.