A longitudinal assessment of lower extremity coordination patterns during gait within 6 months following anterior cruciate ligament reconstruction

• Speaker: Cortney Armitano-Lago, University of North Carolina, Chapel Hill
• Abstract: Less variable lower limb joint coupling strategies increase localized stress on knee joint tissues. While 50% of individuals who undergo anterior cruciate ligament reconstruction (ACLR) develop posttraumatic osteo-arthritis, it is unclear how the underlying coordination dynamics during gait differ from uninjured controls. We conducted a longitudinal assessment to compare gait coordination profiles of individuals 2-, 4-, and 6-months post-ACLR to a coordination profile of uninjured controls. Thirty-four people post-ACLR (age: 21±4years; 65% female) and 34 controls (age: 21±3years; 65% female) participated. Walking gait kinematics were collected in the ACLR group at 2, 4, and 6 months post-ACLR and in the control group at a single assessment. Cross-recurrence quantification analysis was used to characterize sagittal plane ankle-knee, ankle-hip, and knee-hip coordination patterns. Comprehensive GLMMs compared between-group coordination outcomes from each time point post-ACLR to the uninjured control session. A between-group effect of mean line was observed for each time point post-ACLR time points within the ankle-knee (F1,70=8.96; F1,68=8.05; F1,65=10.29; all p <0.05) and ankle-hip (F1,70=14.87; F1,68=13.50; F1,65=5.59; all p<0.05), respectively, and the knee-hip 4 (F1,68=38.95, p<0.05) and 6 months (F1,68=31.19, p<0.05) indicating, on average, stronger coupling over longer periods post- ACLR. A between-group effect of cross-max line at 4 (F1,68=12.34, p<0.05) and 6 months (F1,66=11.11, p<0.05) within the knee-hip was observed suggesting overall stronger joint coupling of the knee-hip within the ACLR group. These results indicate people within 6 months post-ACLR exhibit a distinct, stronger coupled, walking coordination pattern compared to uninjured controls which may increase localized joint stress and have long-term implications for knee joint health. Joint work with  Elizabeth Bjornsen, Caroline Lisee, Louise Thoma, Troy Blackburn, Jeffrey T. Spang, Adam W. Kiefer, and Brian Pietrosimone, University of North Carolina, Chapel Hill.

Complex socio-cognitive dynamics of age-related changes in challenging listening experiences

• Speaker: Ilse Wambacq, Montclair State University
• Abstract: Traditional clinical approaches are often too linear to grasp the complex dynamics which result in functional disabilities people perceive in their daily functioning. Persistent difficulties perceiving speech in adverse listening conditions (such as in a restaurant or at a party) are a common experience for people as they age, even when clinical evaluation of the hearing mechanism is non-indicative of hearing loss. Cognitive and psychological factors are at play, but all too often audiologists do not consider those when diagnosing or counseling their patients. The complex nature of contributing factors to acoustically degraded speech perception calls for a novel and interdisciplinary approach to the diagnosis of communication impediments for which no linear cause can be found. In our paper we provide evidence that non-linear dynamics can be used to build a sociocognitive network model of speech perception. We imported publicly available data from the MIDUS study (1995), which contains results from speech perception, cognitive and psychological self-report scales and tests. We conducted a network analysis on the data of 119 adults, ranging in age from 34 to 83 years, and found that socio-cognitive networks varies as a function of the degraded listening experience. Using a network analysis of the socio-cognitive profile of people with speech perception difficulties provides an innovative approach towards exploring solutions for those who are otherwise left without any insight into their listening problems. We look into examples involving the complex dynamics among age, anxiety, divided attention and executive functions during challenging listening experiences. Joint work with Koen DePryck, Vrije Universiteit Brussel.

Poised for performance: A preliminary analysis of preparatory neuromuscular dynamics and functional reaction time in a sport-like virtual reality task

• Speaker: Adam Kiefer, University of North Carolina at Chapel Hill
• Abstract: Enhancing athletic performance requires adaptive neuromuscular dynamics, which involve increased intermittency. Intermittency is a distinctive characteristic indicating a system's delicate balance between stability and instability. At the pinnacle lies metastability, which enables seamless and efficient transitions among transient, stable states of motor behavior. This study investigated the impact of task loading' i.e., the presence or absence of virtual defenders' on neuromuscular dynamics during an over-ground moving target interception task in virtual reality (VR). Contact sport athletes (N=17, 5 female, M age=20.47 ± 1.50 years) wore a VR headset, and EMG sensors on eight lower limb locations: this analysis focuses on the left and right quadriceps and medial gastrocnemius muscles. Participants were presented with an open field or three virtual defenders before a moving target appeared, and they ran to intercept it while avoiding any defenders. Recurrence quantification analysis was applied to the first 230 ms of EMG data following target onset. Functional reaction times (fRT) were also computed for each trial, defined as the time each athlete took to move 0.5 m in Euclidean distance from their origin. Paired-samples t-tests revealed increased intermittency in left quadriceps and gastrocnemius activation (lower trapping time and vertical line max) when defenders were present (all p < .027). Moreover, significant negative correlations were found between these measures and fRT across all four muscles (all r > 0.53). These findings demonstrate that task load affects preparatory neuromuscular activation dynamics in contact-sport athletes, potentially informing enhanced training practices through the identification of signatures of neuromotor adaptability. Joint work with Dominic Willoughby, Nikki AitchesonHuehn, Cortney Armitano-Lago, Ryan MacPherson, University of North Carolina at Chapel Hill, and Kelly Cohen, and Paula Silva, University of Cincinnati.