Valentina Graci

Recently, pre-pretensioner equipped seatbelts (PPT) were found to be effective in repositioning forward-leaning adults. The aim of this study was to evaluate the influence of the PPT on booster-seated forward-leaning children during sled-simulated frontal oblique low-acceleration impacts. Eight child volunteers (mean: 6.6 ± 0.5 years, four males, four females; weight 24.2 ± 2.1 kg; seated height 64.4 ± 3.9 cm) were seated on a low-acceleration impact sled in a high-back belt-positioning booster seat (BPB) on a rear vehicle bench seat restrained with a three-point seatbelt with a PPT. Volunteers were exposed to a far-side impact 30° from frontal (peak acceleration 1 g, duration 265 ms). Four randomized testing conditions were examined and repeated twice: seatbelt conditions with PPT (85 N at 250 ms prior sled onset) and without PPT; and a standard and a forward-leaning posture. A 3D motion capture system captured participants' kinematics. Repeated measure three-way ANOVAs tested the effect of seatbelt condition, posture, and repetition on head and trunk peak forward displacement. All displacements were measured relative to the initial position. The PPT reduced peak forward head displacements in both standard (PPT 103 ± 21 mm vs no-PPT 165 ± 19 mm) and forward-leaning (PPT 42 ± 37 mm vs no-PPT 138 ± 25 mm) postures (p < .001). In the forward-leaning posture with the PPT, the maximum trunk displacement was the initial position: the peak trunk displacement during the sled pulse was less forward than the initial trunk position. Overall, the peak forward trunk displacement was greater in the standard posture (50 ± 37 mm) than in the forward-leaning posture (29 ± 45 mm) (p < .001) and was greater without the PPT (79 ± 13 mm) than with the PPT (1 ± 18 mm). Reduced values with the PPT were also found in the lateral head and trunk displacements (p < .005) regardless of initial posture. The PPT reduced head and trunk displacements in forward-leaning postures and prevented the trunk from moving further forward from the initial forward-leaning position. A PPT, with a relatively low force of 85 N, has the potential to reduce out-of-position postures in booster-seated children in nonstandard seating positions.

Occupant bracing behavior in pre-crash maneuvers has been previously investigated but the effect of the duration of the pre-crash maneuver on bracing is unknown. This is critical to understand as time-extended pre-crash maneuvers may emerge in cases where drivers lose control of a vehicle and in autonomous vehicles as they may take different approaches to avoid crashes than the current vehicles. Therefore, the aim of this study was to understand the effect of pre-crash maneuver duration on child and adult occupants' bracing behavior and resulting kinematics. Forty seatbelt restrained subjects (9-40 years old) experienced sled-simulated time-extended lateral swerving maneuvers (8 s, 4 cycles, peak acceleration 0.7 g) producing an alternating motion initially out-of-the-belt, followed by into-the-belt for each cycle. In a braced condition, subjects were instructed to hold on to a laterally placed handle with their right hand before the maneuver onset, while in an unbraced condition no instructions were given. A 3D-motion capture system, electromyography (EMG), and seatbelt load cells captured head and trunk kinematics (normalized to seated height), muscle activation (normalized to maximum voluntary isometric contraction, MVIC), and seatbelt reaction forces (normalized to body weight), respectively. The effects of cycles and interaction with bracing and age on peak lateral head and trunk displacement into- and out-of-the belt were examined with Mixed-Effects Models and Tukey's post-hoc tests (p ≤ 0.05). Out-of-the-belt peak lateral head and trunk displacements were the greatest in the first cycle and the smallest in the second cycle (p < 0.01). The third and four cycles were not significantly different from one another (p > 0.8). Into-the-belt peak lateral head and trunk displacements were smaller in the first cycle than the remaining cycles (p < 0.001) and were not significantly different across the remaining cycles (p > 0.8). No interactions between cycle, age and bracing were found (p > 0.3). Right bicep, trapezius and rectus femoris activations slightly increased with increasing cycles in the unbraced condition and in the into-the-belt direction for the 9-11 year-old group. Out-of-belt seat belt loads increased with increasing cycles in the unbraced condition for all age groups. Occupant kinematics as a result of their bracing behavior changed across cycles of swerving maneuvers from an exaggerated displacement in cycle 1 to an overcompensation due to bracing in cycle 2, ending with a plateau of a moderate displacement in cycle 3 and 4. Younger children (age 9-11) took longer to adapt to the oscillatory motion as they increased their muscle activation over time unlike the other age groups. These findings suggest that it may take time for occupants to find the optimal bracing strategy in time-extended maneuvers. Furthermore, children may find challenging to calibrate their bracing response overtime from a neuromotor perspective.

Millions of people around the globe are impacted by falls annually, making it a significant public health concern. Falls are particularly challenging to detect in real time, as they often occur suddenly and with little warning, highlighting the need for innovative detection methods. This study aimed to assist in the advancement of an accurate and efficient fall detection system using electroencephalogram (EEG) data to recognize the reaction to a postural disturbance. We employed a state-space-based system identification approach to extract features from EEG signals indicative of reactions to postural perturbations and compared its performance with those of traditional autoregressive (AR) and Shannon entropy (SE) methods. Using EEG epochs starting from 80 ms after the onset of the event yielded improved performance compared with epochs that started from the onset. The classifier trained on the EEG data achieved promising results, with a sensitivity of up to 90.9%, a specificity of up to 97.3%, and an accuracy of up to 95.2%. Additionally, a real-time algorithm was developed to integrate the EEG and accelerometer data, which enabled accurate fall detection in under 400 ms and achieved an over 99% accuracy in detecting unexpected falls. This research highlights the potential of using EEG data in conjunction with other sensors for developing more accurate and efficient fall detection systems, which can improve the safety and quality of life for elderly adults and other vulnerable individuals.

In frontal crashes belt-positioning boosters (BPB) may prevent submarining when the seatback is reclined. It is unclear if the BPB can also mitigate injuries in far-side lateral-oblique crashes in reclined conditions, where current restraints are less effective in reducing lateral excursion. This study aimed to understand reclined child injury risk during lateral-oblique impacts, with and without a booster seat, by using the Large Omni-Directional Child (LODC) test device. The LODC was tested in nine lateral-oblique impact (80° from frontal) sled tests (target 31.3 km/h, duration 58 ms maximum, peak acceleration 21 g). Three seatback angles (25°, 45°, and 60°) with and without the BPB were compared on a production passenger seat with an integrated seatbelt. The LODC moved toward the buckle side during the far-side lateral-oblique impact. Abdominal pressure (left and right), seatbelt loads, anterior superioriliac spine (ASIS) forces, and pelvis lateral rotation were examined. The LODC head and knee excursions were extracted from a 3D-motion capture system. In the reclined noBPB condition, peak abdominal pressures on the buckle side reached up to 186 kPa and the ASIS forces demonstrated an early (∼ 50 ms) peak and a subsequent drop in the reclined noBPB conditions, suggesting that the belt slid into the abdomen.With the BPB, peak pelvis lateral rotation was greater than in the noBPB conditions but decreased with increasing reclined seatback angles (BPB: 31° to 36.5° vs no-BPB: -5° to -4.6°). Peak lap belt forces were greater in the reclined noBPB conditions (4.8-4.9 kN) compared to all conditions with the BPB (2.9-3.2 kN).The greatest lateral head excursion was observed in the BPB 25° condition (895 mm) and the lowest in the noBPB 45° condition (748 mm). The BPB may prevent the lap belt intrusion into the abdomen in reclined configurations in far side lateral-oblique impacts. The greater pelvis lateral rotation and head displacement with the BPB may lead to contact with other rear-seated occupants and/or vehicle structures, although motion decreased with the BPB as the reclined seatback angle increased. This suggests that reclined seats may help reduce BPB-seated children's lateral excursion in far-side lateral-oblique impacts.

Bracing can reduce adult occupants' out-of-position postures, but it is unclear if this finding can be extended to child occupants. We investigated the effect of bracing, and age on the motion of vehicle occupants of different ages during sled-simulated pre-crash maneuvers. Forty seatbelt restrained subjects (9-40 y.o.) experienced sled simulated evasive swerving maneuvers during a brace condition, where subjects actively brace before the maneuver onset, and an unbraced condition. A 3D motion capture system, electromyography (EMG), and seatbelt load cells captured head and trunk kinematics, muscle activation, and seat belt reaction forces, respectively. The effects of age and bracing on peak lateral head and trunk displacement were examined with Mixed Effects Model (p ≤ 0.05). In the braced condition, all subjects had reduced normalized peak head (0.09 ± 0.05) and trunk (0.11 ± 0.05) displacements compared to the unbraced condition (Head: 0.14 ± 0.06, Trunk: 0.17 ± 0.07) (p < 0.05). For the into-the-belt direction in the unbraced condition, children showed the smallest peak head and trunk displacement of all age groups (p < 0.01) while teens had the greatest peak head and trunk displacement compared to all other age groups (p < 0.02). Similar trends were found in the out-of-the-belt direction in the unbraced condition (p < 0.01). In the unbraced condition, all occupants showed greater shoulder seat belt reaction loads than the braced condition (unbraced 1.6-2.7 N/kg, braced 1.0-1.4 N/kg). Children also showed greater neck muscle activation (50-64% MVIC) compared to other muscles and older occupants regardless of the bracing condition or direction of motion. Bracing reduced out-of-position postures across all ages. In the unbraced condition, children move less than teens and adults due to greater activation in the neck muscles. In the unbraced condition, teens showed the greatest motion, potentially due to their developing neuromotor control transitioning to a more mature stage. Across all age groups in the unbraced condition, occupants relied more heavily on the seat belt to maintain their position rather than their muscles to brace, suggesting the importance of good seatbelt-torso interaction in unbraced occupants.

Previous studies showed that awareness reduced adult occupants' out-of-position posture, but it is unclear if this finding can be extended to child occupants and time extended pre-crash maneuvers. This is important to be examined as, in highly automated vehicles, reduced awareness of impending maneuvers in all populations of occupants may influence restraint effectiveness. Therefore, we investigated the effect of awareness, age, and pre-crash maneuver duration on the motion and muscle activity of vehicle occupants during sled-simulated pre-crash evasive swerving maneuvers. Forty seatbelt restrained subjects (9-40 years old) experienced a sled oscillatory perturbation (4 cycles, peak acceleration 0.7g) mimicking a series of swerving maneuvers under 2 conditions: an aware condition where subjects were instructed to brace before the maneuver onset, and an unaware condition, with no bracing instructions given. A 3D motion capture system, electromyography (EMG), and seatbelt load cells captured head and trunk kinematics, muscle activation, and seat belt reaction forces, respectively. Data were normalized by the subject seated height (Kinematics), the subject maximum voluntary isometric contraction (MVIC) (Muscle Activation), and the subject body weight (BW) (Seat Belt Reaction Forces). The effects of awareness, age, cycle, and interactions of those variables on peak lateral head and trunk displacement into and out-of-the belt were examined with a Mixed Effects Model and Tukey's post-hoc tests (p≤0.05). In the aware condition, all subjects had reduced normalized peak head (0.09 ± 0.05) and trunk (0.11 ± 0.05) displacements compared to the unaware condition (Head: 0.14 ± 0.06, Trunk: 0.17 ± 0.07) (p<0.05). For the into the belt direction in the unaware condition, children showed the smallest peak head and trunk displacement of all age groups (p<0.01) while teens had the greatest peak head and trunk displacement compared to all other age groups (p<0.02). Similar trends were found in the out of the belt direction in the unaware condition, where children showed the smallest peak head and trunk displacement compared to adolescents and teens (p 0.05). Peak lateral head and trunk displacement was greatest in the first swerve out of the belt (p<0.01) and the smallest in the second swerve, regardless of age and awareness. In the unaware condition, all occupants showed greater shoulder seat belt reaction loads than the aware condition (unaware 1.6-2.7 N/kg, aware 1.0-1.4 N/kg). Children also showed greater neck muscle activation (50-64% MVIC) compared to other muscles and older occupants regardless of awareness condition or direction of motion. Awareness reduced out-of-position postures in pre-crash vehicle maneuvers across all ages, including pediatric occupants. In the unaware condition, young children move less (normalized by seated height) than older teens and adults. This may be due to children using a different bracing strategy than older occupants as shown by the greater neck muscle activation. On the other hand, in the unaware condition, teens showed the greatest motion, potentially due to their developing neuromotor control transitioning to a more mature stage. Occupant responses changed over the maneuver duration, likely due to becoming more familiar with oscillatory motion throughout the cycles. Across all age groups in the unaware condition, occupants relied more heavily on the seat belt to maintain their position rather than relying on an active bracing strategy, particularly when moving out of the belt, suggesting the importance of good seatbelt-torso interaction in unaware occupants. Further investigation examining occupant awareness in various pre-crash maneuvers and seating configurations is warranted to understand how to protect unaware occupants in future vehicle and crash dynamics.

Introduction: Despite being a primary impairment in individuals with cerebral palsy (CP), selective motor control (SMC) is not routinely measured. Personalized treatment approaches in CP will be unattainable without the ability to precisely characterize the types and degrees of impairments in motor control. The objective of this study is to report the development and feasibility of a new methodological approach measuring muscle activation patterns during single-joint tasks to characterize obligatory muscle co-activation patterns that may underly impaired SMC.Methods: Muscle activation patterns were recorded during sub-maximal voluntary isometric contraction (sub-MVIC) tasks at the hip, knee, and ankle with an interactive feedback game to standardize effort across participants. We calculated indices of co-activation, synergistic movement, mirror movement, and overflow (indices range 0–2, greater scores equal to greater impairment in SMC) for each isolated joint task in 15 children – 8 with typical development (TD) (mean age 4.7 ± 1.0 SD years) and 7 with CP (mean age 5.8 ± 0.7 SD years). Indices were compared with Mann–Whitney tests. The relationships between the indices and gross motor function (GMFM-66) were examined with Pearson’s r.Results: Mean indices were higher in the CP vs. the TD group for each of the six tasks, with mean differences ranging from 0.05 (abduction and plantarflexion) to 0.44 (dorsiflexion). There was great inter-subject variability in the CP group such that significant group differences were detected for knee flexion mirroring (p = 0.029), dorsiflexion coactivation (p = 0.021), and dorsiflexion overflow (p = 0.014). Significant negative linear relations to gross motor function were found in all four indices for knee extension (r = −0.56 to −0.75), three of the indices for ankle dorsiflexion (r = −0.68 to −0.78) and in two of the indices for knee flexion (r = −0.66 to −0.67), and ankle plantarflexion (r = −0.53 to −0.60).Discussion: Indices of coactivation, mirror movement, synergy, and overflow during single-joint lower limb tasks may quantify the type and degree of impairment in SMC. Preliminary concurrent validity between several of the indices of SMC and gross motor function was observed. Our findings established the feasibility of a new methodological approach that quantifies muscle activation patterns using electromyography paired with biofeedback during single-joint movement.

Disruptions in gait function are common after concussion in adolescents; however, the neuromotor control deficits driving these gait disruptions are not well known. Fifteen concussed (age mean [SD]): 17.4 [0.6], 13 females, days since injury: 26.3 [9.9]) and 17 uninjured (age: 18.0 [0.7], 10 females) adolescents completed 3 trials each of single-task gait and dual-task gait (DT). During DT, participants simultaneously walked while completing a serial subtraction task. Gait metrics and variability in instantaneous mean frequency in lower extremity muscles were captured by inertial sensors and surface electromyography, respectively. A 2-way analysis of covariance was used to compare gait metrics across groups and conditions. Functional principal components analysis was used to identify regions of variability in instantaneous mean frequency curves. Functional principal component scores were compared across groups using a Welch statistic. Both groups displayed worse performance on gait metrics during DT condition compared to single-task, with no differences between groups (P < .001). Concussed adolescents displayed significantly greater instantaneous mean frequency, indicated by functional principal component 1, in the tibialis anterior, biceps femoris, and semitendinosus (P < .05) during single-task and DT compared with uninjured adolescents. Our observations suggest that concussed adolescents display inefficient motor unit recruitment lasting longer than 2 weeks following injury, regardless of the addition of a secondary task.

Belt-positioning booster (BPB) seats may prevent submarining in reclined child occupants in frontal impacts. BPB-seated child volunteers showed reduced lateral displacement in reclined seating in low-acceleration lateral-oblique impacts. As submarining was particularly evident in reclined small adult female occupants, we examined if a booster seat could provide similar effects on the kinematics of the small female occupant to the ones found on the reclined child volunteers in low-acceleration far-side lateral oblique impacts. The THOR-AV-5F was seated on a vehicle seat on a sled simulating a far-side lateral-oblique impact (80 deg from frontal, maximum acceleration ∼2 g, duration ∼170 ms). Lateral and forward head and trunk displacements, trunk rotation, knee-head distance, seatbelt loads, and head acceleration were recorded. Three seatback angles (25 deg, 45 deg, 60 deg) and two booster conditions were examined. Lateral peak head and trunk displacements decreased in more severe reclined seatback angles (25–36 mm decrease compared to nominal). Forward peak head, trunk displacements, and knee-head distance were greater with the seatback reclined and no BPB. Knee-head distance increased in the severe reclined angle also with the booster seat (>40 mm compared to nominal). Seat belt peak loads increased with increased recline angle with the booster, but not without the booster seat. Booster-like solutions may be beneficial for reclined small female adult occupants to reduce head and trunk displacements in far-side lateral-oblique impacts, and knee-head distance and motion variability in severe reclined seatback angles.

Balance perturbations are accompanied by global cortical activation that increases in magnitude when postural perturbations are unexpected, potentially due to the addition of a startle response. A specific site for best recording the response to unexpected destabilization has not been identified. We hypothesize that a single sensor located near to subcortical brainstem mechanisms could serve as a marker for the response to unpredictable postural events. Twenty healthy young (20.8 ± 2.9 yrs) and 20 healthy elder (71.7 ± 4.2 yrs) adults stood upright on a dynamic platform with eyes open. Platform translations (20 cm at 100 cm/s) were delivered in the posterior (29 trials) and anterior (5 catch trials) directions. Active EEG electrodes were located at Fz and Cz and bilaterally on the mastoids. Following platform acceleration onset, 300 ms of EEG activity from each trial was detrended, baseline-corrected, and normalized to the first trial. Average Root-Mean-Square (RMS) values across “unpredictable” and “predictable” events were computed for each channel. EEG RMS responses were significantly greater with unpredictable than predictable disturbances: Cz ( $\text{p} < 0.001$ ), Fz ( $\text{p} < 0.003$ ), and mastoid ( $\text{p} < 0.0001$ ). EEG RMS responses were also significantly greater in elderly than young adults at Cz ( $\text{p} < 0.02$ ) and mastoid ( $\text{p} < 0.04$ ). A significant effect of sex in the responses at the mastoid sensors ( $\text{p} < 0.04$ ) revealed that elderly male adults were principally responsible for the age effect. These results confirm that the cortical activity resulting from an unexpected postural disturbance could be portrayed by a single sensor located over the mastoid bone in both young and elderly adults.